CA1259373A - Power supply circuit - Google Patents
Power supply circuitInfo
- Publication number
- CA1259373A CA1259373A CA000525272A CA525272A CA1259373A CA 1259373 A CA1259373 A CA 1259373A CA 000525272 A CA000525272 A CA 000525272A CA 525272 A CA525272 A CA 525272A CA 1259373 A CA1259373 A CA 1259373A
- Authority
- CA
- Canada
- Prior art keywords
- transistor
- battery
- power supply
- base
- supply circuit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/1563—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators without using an external clock
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/02—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from ac mains by converters
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2207/00—Indexing scheme relating to details of circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J2207/20—Charging or discharging characterised by the power electronics converter
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S30/00—Cutlery
- Y10S30/01—Rechargeable battery operated
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S320/00—Electricity: battery or capacitor charging or discharging
- Y10S320/28—Regulating transformer, e.g. high leakage, ferro-resonant
Abstract
ABSTRACT:
"Power supply circuit".
For charging a battery (6) a self-oscillating power supply circuit is used in which energy is stored in a transformer (Tr) during the so-called forward intervals, which energy is applied in the form of a charge current to the battery (6) during the so-called flyback intervals.
To prevent overcharge of the battery (6), the circuit is provided with an accumulator voltage protection circuit (10) receiving its power supply from the battery (6), to which circuit a fraction of the battery voltage is applied by means of a voltage divider (R3,R4) which is arranged across the battery (6) by means of a switch (S1) during the flyback intervals. To prevent the voltage drop across the internal resistance of the battery from influencing the measurement of the battery voltage, the battery voltage is measured after the end of a flyback interval and before the commencement of the next forward interval.
To this end the inputs (11, 12) of the accumulator voltage protection circuit (10) are short-circuited with the aid of two diodes (D1, D2) during the flyback intervals.
Figure 1.
"Power supply circuit".
For charging a battery (6) a self-oscillating power supply circuit is used in which energy is stored in a transformer (Tr) during the so-called forward intervals, which energy is applied in the form of a charge current to the battery (6) during the so-called flyback intervals.
To prevent overcharge of the battery (6), the circuit is provided with an accumulator voltage protection circuit (10) receiving its power supply from the battery (6), to which circuit a fraction of the battery voltage is applied by means of a voltage divider (R3,R4) which is arranged across the battery (6) by means of a switch (S1) during the flyback intervals. To prevent the voltage drop across the internal resistance of the battery from influencing the measurement of the battery voltage, the battery voltage is measured after the end of a flyback interval and before the commencement of the next forward interval.
To this end the inputs (11, 12) of the accumulator voltage protection circuit (10) are short-circuited with the aid of two diodes (D1, D2) during the flyback intervals.
Figure 1.
Description
~ ~593~73 PHN 11 596 l 10 -3-1986 "Power supply circui-t".
The invention relates to a power supply circuit for charging a battery, comprising a first series arrange-ment of a primary winding of a transformer, a first tran-sistor, a first resistor and a second series arrangement of a secondary winding of the transformer and a first rectifier diode, said second series arrangement being provided with connection terminals for connecting the battery, and comprising a positive feedback provided with a first capacitor between the junction of the secondary 10 winding and the first rectiier diode and the base of the first transistor, a second transistor coupled to the first resistor for turning off the first transistor and furthermore comprising a switching amplifier arranged be-tween the connection terminals of the battery for turning on the second transistor above a first value of the battery voltage and for turning off the second transistor below a second value of the battery voltage below the first value,said switching amplifier having a first input, a second input and an output, said first input being 20 coupled to a tap on a voltage divider which is arranged between the connection terminals of the battery by means of a switch during the periods when the first transistor is turned off, said second input being coupled to the con-nection terminal of the battery facing the first rectifier diode,and said output being coupled to the base of the second transistor.
A circuit of this type can be used for charging a battery from different input voltages. The input voltage may be both a rectified alternating voltage and a direct voltage. A circuit of this type is particularly suitable for use in a shaver in which the circuit is used for charging the battery and/or for the power supply of the motor.
~ '~
' , `` ~2S~373 A power supply circuit of the type mentioned in the opening paragraph is used in the Philips'shaver which is commercially available under type number HP 1335 at the time of filing this Application. In this circuit a current flows through the primary winding during the so-called forward interval resulting in energy being stored in the transformer. At a given value of the primary current the second transistor is turned on by the voltage across the first resistor and consequently the first transistor is turned off so that the primary current is interrupted. The energy stored is then applied in the form of a charge cur-rent to the battery vla the secondary winding and the diode during the so-caIled flyback interval. After the fly-back interval the next forward interval is initiated by the positive feedback between the secondary winding and the base of the first transistor. In this manner the battery can be charged relatively rapidly with a comparati-vely large current.
To avoid damage of the battery due to overcharge, the power supply circuit is provided with a switching amplifier turning off the power supply circuit above a first value of the battery voltage and subsequently releas-ing the circuit at the instant when the battery voltage has decreased to below a second value determinèd by the hysteresis of the switching amplifier. Thus there is a change-over from rapid charge to trickle charge after the first value has been exceeded for the first time.
A circuit of this type is also known from European Patent Application 95 072. In these known power supply circuits the switching amplifier is connected to the connection terminals of the battery throughout the fly-back interval. During this flyback interval the battery voltage may exceed the first value of the switching amplifier due to the voltage drop caused by the charge current across the internal resistance of the battery, so that the second transistor is turned off. To eliminate the influence of the internal resistance of the battery on the measurement of the battery voltage, the battery voltage ~ -,' -- ' ' ' ~55~373 determines only at the end of the flyback interval, i.e.
at the instant when the charge current becomes zero, whether the second transistor remains actually turned on and hence whether the next forward interval is blocked.
However, the following problem occurs in these circuits. When the second transistor is turned on during the flyback interval by a battery voltage above the first value of the switching amplifier, this second transistor is to be turned off again if the battery voltage is not above this value at the end of the flyback interval. It takes some time to turn off the second transistor as a result of the presence of capacitive charges. This delays the initiation of the next forward interval, which disturbs the satisfactory operation of the circuit.
lS It is therefore an object of the invention to provide a power supply circuit obviating this problem.
According to the invention, a power supply circuit of the type mentioned in the opening paragraph is characterized in that the first input of the switching amplifier is coupled by means of a second rectifier diode to the junction of the secondary winding and the first rectifier diode and that the forward direction of the second rectifier diode, reckon-ed from this junction, is the same as that of the first rectifier diode.
Due to the measure according to the invention two conducting diodes having, however, opposite polarities, are present between the first and the second input of~ the switching amplifier during a flyback interval, so that no voltage is present between these inputs. Consequently the switching amplifier is not activated during a flyback interval. At the end of a flyback interval the secondary voltage and the secondary current become ~ero. The voltage at the junction of the secondary winding and the first diode subsequently increases again so that the two rectifier diodes are cut off. However, it takes some time before the first transis-tor is turned on via the positive feedback of the capacitor between the secondary winding and the base of this transis-tor and the next forward interval is initiated. This time , ...
' ' '.
`" 125~373 PHN 11 596 -~- 4-3-1986 is utilized to measure the battery voltage. At a battery voltage above the first value the second transistor is turned on by the switching amplifier so that the next forward interval is blocked until the battery voltage has decreased to below the second value.
An embodiment of a power supply circuit according to the invention is characterized in that the switch is constituted by a third transistor of a conductivity type which is opposed to that of the first transistor, and whose 0 emitter-collector path is disposed between the battery terminal facing the first transistor and the end of the voltage divider facing this terminal and whose base is coupl-- ed by means of a third rectifier diode to the junction of the secondary winding and the first rectifier diode.
During a flyback interval the voltage at the junction of the secondary winding and the first diode is negative so that the third transistor is turned on via the third diode and consequently the voltage divider is arranged between the connection terminals of the battery.
This embodiment can be futher characterized in that the base of the third transistor is further coupled by means of a fourth rectifier diode to the connection terminal of the battery facing the first tranSiStOE~ the fourth rectifier diode being preferably a light-emitting diode. Apparrently, this diode lights up during rapid charge and flashes during trickle charge thus informing the user on the fully charged condition of the battery.
To ensure that the voltage divider is not arranged between the connection terminals of the battery during the forward intervals~ a further embodiment may be character-ized in that the base of the third transistor is also coupled by means of a resistor to the collector of the second transistor. Due to this measure the third transistor is also immediately turned on at the instant when the second transistor is turned on.
Still a further embodiment is characterized in that the base of the third transistor is connected by means of a second capacitor to a tap, separated with respect to d.c. current from the secondary winding, in the positive ~ll25~373 feedback between the secondary winding and the base of the first transistor.
Thus it is achieved that if the battery voltage is not above the first value, at the end of a flyback interval, the third transistor is rapidly turned off prior to the next forward interval being fully initiated.
In a power supply circuit according to the in-vention the switching amplifier may be constituted by a Schmitt trigger. A suitable embodiment thereof may be o characterized in that the Schmitt trigger is constituted by a fourth transistor of a conductivity type which is the same as that of the first transistor and whose base is coupled to the first input and the emitter is coupled to the second input and whose collector is connected by means of the parallel arrangement of a second resistor and the base-emitter junction of a fifth resistor of a conductivity type opposed to that of the fourth transistor to the con-nection terminal of the battery facing the first transistor, th collector of said fifth transistor being coupled by means of a third resistor to the base of the fourth transistor and also to the base of the second transistor.
The invention will be further described with ` reference to the accompanying drawing in which Figure 1 shows a principle circuit diagram of the power supply circuit according to the invention, Figure 2 shows a first embodiment of a power supply circuit according to the invention, Figure 3 shows a second embodiment of a power supply circuit according to the invention, and Figure 4 shows a third embodiment of a power supply circuit according to the invention.
Figure 1 shows a principle circuit diagram of a power supply circuit according to the invention. The circuit has two input terminals 2 and 3 for applying an input volt-age which may be both a rectified alternating voltage and a direct voltage. The series arrangement of a primary wind-ing n1 of a transformer Tr, the collector-emitter path of a first transistor T1, the series arrangement of a secondary winding n2 and a first rectifier diode D1 with connection terminals 4 and 5 between which a battery 6 is connected, and a first resistor R1 is incorporated between these ter-minals 2 and 3. In this example the battery 6 is formed by two series-arranged nickel cadmium accumulator cells 7 and 8. A d.c. motor M of, for example, a shaver may be arranged in parallel with this battery 6 by means of a switch S2. In that case a resistor R6 is arranged in paral-lel with the resistor R1, simultaneously with the aid of a switch S3. A positive feedback constituted by the series arrangement of a first capacitor C1 and a resistor R2 is arranged between the junction 9 of the secondary winding n2 and the diode D1 and the base of transistor T1. The base pf transistor T1 is also connected via a starting resis-tor R5 to the input terminal 2. It is to be noted that thecircuit may alternatively be started in manners other than with this resistor R5. The resistor R1 is connected to the base of a second transistor T2 whose collector is coupled to the base of the first transistor T1. Further-more a switching amplifier 10 having a first input 11,a second input 12 and an output 13 is arranged between the connection terminals 4 and 5 of the battery 6. The first input 11 is connected` to a tap 14 of a voltage divider con-stituted by resistors R3 and R4, resistor R3 being con-nected by means of a switch S1 to the connection terminal4 and resistor R4 being connected to the connection terminal 5 of the battery 6. Furthermore the first input 11 is con-nected by means of a diode D2 to the junction 9 of the secondary winding n2 and diode D4. The forward direction of diode D2, viewed from the junction 9, is the same as that of diode D1. The second input 12 is connected to the connection terminal 5, whilst the output 13 is con-nected to the base of the second transistor T2.
The circuit operates as follows. The switches S2 and S3 are initially open and the circuit thus only provides the charge current for the accumulator cells 7 and 8. In the presence of an input voltage across the termina]s 2 and 3 a small current flows via the starting ~:5~373 resistor S5 in the base of transistor T1 so that it is partly rendered conducting. The resultant current through the primary winding n1 results in an increase of the voltage across the secondary winding n2 so that transistor T1 is further rendered conducing via the positive feedback of capacitor C1 and resistor R1. Due to this positive feed-back transistor T1 is then rapidly driven into saturation.
The current through the primaray winding n1 subsequently increases linearly in time during the so-called forward interval. At a level of the primary current determined by the resistance of resistor R1 transistor T2 is turned on so that transistor T1 is turned off. Due to the interruption of the primary current the polarity of the voltage across the secondary winding n2 is reversed so that diode D1 becomes conducting. The energy stored in the transformer Tr during the forward interval is then applied in the form of a charge current to the battery 6 during the so-called flyback interval. This current decreases linearly in time to zero.
During the flyback interval the voltage at the junction 9 is negative and is equal to the voltage across the diode D1.
At the end of the flyback interval the voltage across the winding n2 becomes equal to zero volt so that the voltage at the end 9 becomes equal to the battery voltage. This positive voltage step at the junction 1'19 ensures the initiation of the next forward interval via the positive feedback of capacitor C1 and resistor R2.
In the manner described above the accumulator cells 7 and 8 can be charged relatively rapidly with a comparatively large current. To prevent damage of the accumulator cells due to overcharge, the power supply cir-cuit is provided with a switching device switching off the power supply circuit when the accumulator cells 7 and 8 are full. Its operation will now be further explained.
The voltage divider with resistors R3 and R4 is connected between the connection terminals 4 and 5 of the battery 6 by means of the switch S1 during a flyback interval. A fraction of the battery voltage would then be present across the resistor R4 and it would also be present ` .~l2~3~3 between the first and the second inputs 11 and 12 of the switching amplifier 10. This is, however, prevented by the second rectifier diode D2.
At the beginning of a flyback interval the voltage across the secondary winding n2 reverses its polarity so that the voltage at the junction 9 becomes negative. Consequently not only diode D1 but also diode D2 becomes conducting.
Two conducting diodes having, however, opposite polarities are then present between the inputs 11 and 12 of the switching amplifier 10 so that there is no voltage between these inputs. Thus, no information about the magnitude of the battery voltage is presented to the switching ampli-fier 10 during a flyback interval. As already stated, a voltage step occurs at the end 9 of the secondary winding n2 at the end of the flyback interval. This step is passed on with a certain delay by the positive feedback of capaci-tor C1 and resistor R2 to the base of transistor T1 so that it takes some time after the end of a flyback interval before transistor T1 is rendered fully conducting again.
Since the swltch S1 is also opened with a certain delay, the battery voltage can be measured in this time without the internal resistance of the accumu~tor cells 7 and 8 in-fluencing this measurement. Due to the voltage step at the junction 9 at the end of a flyback interval diode D2 is in fact cut off so that then the fraction of the battery voltage present across the resistor R4 is present between the inputs 11 and 12 of the switching amplifier 10. If this voltage is higher than a first threshold value, the voltage at the output 13 switches over from a low to a high value.
Consequently transistor T2 is turned on and transistor T1 is turned off so that the further initiation of the next forward interval is blocked. The battery voltage is then to decrease to below the second threshold value of the switching amplifier 10 before transistor T2 is turned off again and transistor T1 can become conducting again via the starting resistor R5. In this manner there is a change over from rapid charge to trickle charge.
If the switches S2 and S,3 are closed, the motor M is .~ .
~25~373 arranged in parallel with the battery 6. The power supply circuit then also supplies the motor current. The value of the primary current at which the transistor T1 is turned off is then determined by the parallel arrangement of the resistors R1 and R6.
Figure 2 shows a first embodiment of the power supply circuit according to the invention. The same com-ponents are denoted by the same reference numerals as in Figure 1. In -this embodiment the mains voltage is applied via two terminals 20 and 21 to a rectifier bridge G. The rectified voltage is smoothed with the aid of a filter 22 constituted by two capacitors C3 and C4 and a coil L1 and is subsequently applied to the primary winding n1 of the transformer. A Zener diode Z1 in series with a lS diode D5 is arranged in parallel with this winding n1 with which diode voltage peaks are suppressed when switching off the current through the primary winding. Furthermore transistor T2 is coupled to resistor R1 by means of a voltage divider with resistors R7 and R8 in this embodiment.
20 The switch S1 is constituted by a PNP transistor T3 whose emitter is connected to the connection terminal 4 of the battery 6 and whose collector is connected to the resistor R3 of the voltage divider. A resistor R11 is provided between the emitter and the base of tra~sistor T3. This base is connected by means of the series arrangement of a resistor R1o and a third rectifier diode D3 to the junction 9 of the secondary winding n2 and the diode D1 and further-more by means of a resistor R12 to the collector of transistor T2. The junction 10 of resistor R10 and diode 30 D3 is connected by means of a series arrangement of a resistor R13 and a light-emitting diode D4 to the connect-ion terminal 4 of the battery 6. During a forward interval the voltage at the end 9 is positive relative to the end 4 of the secondary winding n2. Therefore transistor T3 will not be conducting during a forward interval. However, the connection between the base of transistor T3 via resistor R12 and the base of transistor T1 certainly prevents tran-sistor T3 from being turned on during a forward interval.
. . , ~L~ 33~3 In factt the positive base-emitter voltage of transistor T1 is then present between the base and emitter of transis-tor T3. At the end of the forward interval transistor T2 is rapidly driven into saturation so that transistor T1 is turned off. Consequently, the voltage at the base of transis-tor T3 is decreased via resistor R12 so that transistor T3 is turned on. By reversing of the polarity of the voltage across the secondary winding n2 the voltage at the end 9 becomes negative so that diode D3 becomes conducting and transistor T3 is maintained turned on. Transistor T3 is then entirely driven into saturation so that the voltage drop across the collector-emitter path of this transistor is negligible. Due to the diode D3 becoming conducting a cur-rent will also start flowing through the light-emitting diode D4. During rapid charge this diode will appear to be continuously on due to the high frequency of the flyback intervals, whereas during trickle charge this diode will flash. The switching amplifier 10 has an npn transistor T4 whose base constitutes the first input 11 and whose emitter constitutes the second input 12. The collector of this transistor is connected by means of the series arrangement of a resistor R15 and the base-emitter junction of a pnp transistor T5 to the connection terminal 4 of the battery. The collector of this transistor T5 is coupled by means of a resistor R16 to the base of transistor T4 and is furthermore coupled by means of a resistor R17 to the output 13. In this embodiment the voltage divider has a resi~
tor R14 with a positive temperature coefficient which, together with the negative temperature coefficient of the base-emitter voltage of transistor T4, ensures that the temperature coefficient of the threshold voltage of the switching amplifier is adapted to the temperature coeffi-cient of the accumulator cells, which is negative. The switching amplifier 10 constitutes a Schmitt trigger whose operation is assumed to be known and will not be further explained. When the voltage across the resistor R4 exceeds the first threshold value after the end of a flyback inter-val, transistor T2 is turned on via the Schmitt trigger .~
~59373 PHN 11 596 ~ 10-3-1986 10 and the power supply circuit is switched off. Transis-tor T3 is then maintained saturated by means of resistor R12. ~,~hen the battery voltage subsequently decreases to below a second threshold value determined by the resistor R16, transistor T2 is turned off again and the power supply circuit can start again. When the voltage across re-sistor R4 does not exceed the first threshold value of the Schmitt trigger after the end of a flyback interval, the subsequent forward interval is initiated again via the posi-tive feedback of capacitor C1 and resistor R2. TransistorT3 should then be turned off before transistor T1 is turned on. This is realiæed by a capacitor C2 which is disposed be-tween the base of transistor T3 and the junction 15 of ca-pacitor C1 and resistor R2.
Figure 3 shows a second embodiment of a power supply circuit according to the invention in which the same components have the same reference numerals as those in Figure 2. The difference between this embodiment and that of Figure 2 is that resistor R1 is now disposed be-tween transistor T1 and the connection terminal 4 of the battery 6. The resistor R1 is coupled to the base of transistor T2 by means of a Zener diode Z2 During a for-ward interval Zener diode Z2 breaks down at a given value of the primary current so that transistor T2 is turned on and consequently transistor T1 is turned off. Otherwise, the operation of the circuit is the same as that of Figure
The invention relates to a power supply circuit for charging a battery, comprising a first series arrange-ment of a primary winding of a transformer, a first tran-sistor, a first resistor and a second series arrangement of a secondary winding of the transformer and a first rectifier diode, said second series arrangement being provided with connection terminals for connecting the battery, and comprising a positive feedback provided with a first capacitor between the junction of the secondary 10 winding and the first rectiier diode and the base of the first transistor, a second transistor coupled to the first resistor for turning off the first transistor and furthermore comprising a switching amplifier arranged be-tween the connection terminals of the battery for turning on the second transistor above a first value of the battery voltage and for turning off the second transistor below a second value of the battery voltage below the first value,said switching amplifier having a first input, a second input and an output, said first input being 20 coupled to a tap on a voltage divider which is arranged between the connection terminals of the battery by means of a switch during the periods when the first transistor is turned off, said second input being coupled to the con-nection terminal of the battery facing the first rectifier diode,and said output being coupled to the base of the second transistor.
A circuit of this type can be used for charging a battery from different input voltages. The input voltage may be both a rectified alternating voltage and a direct voltage. A circuit of this type is particularly suitable for use in a shaver in which the circuit is used for charging the battery and/or for the power supply of the motor.
~ '~
' , `` ~2S~373 A power supply circuit of the type mentioned in the opening paragraph is used in the Philips'shaver which is commercially available under type number HP 1335 at the time of filing this Application. In this circuit a current flows through the primary winding during the so-called forward interval resulting in energy being stored in the transformer. At a given value of the primary current the second transistor is turned on by the voltage across the first resistor and consequently the first transistor is turned off so that the primary current is interrupted. The energy stored is then applied in the form of a charge cur-rent to the battery vla the secondary winding and the diode during the so-caIled flyback interval. After the fly-back interval the next forward interval is initiated by the positive feedback between the secondary winding and the base of the first transistor. In this manner the battery can be charged relatively rapidly with a comparati-vely large current.
To avoid damage of the battery due to overcharge, the power supply circuit is provided with a switching amplifier turning off the power supply circuit above a first value of the battery voltage and subsequently releas-ing the circuit at the instant when the battery voltage has decreased to below a second value determinèd by the hysteresis of the switching amplifier. Thus there is a change-over from rapid charge to trickle charge after the first value has been exceeded for the first time.
A circuit of this type is also known from European Patent Application 95 072. In these known power supply circuits the switching amplifier is connected to the connection terminals of the battery throughout the fly-back interval. During this flyback interval the battery voltage may exceed the first value of the switching amplifier due to the voltage drop caused by the charge current across the internal resistance of the battery, so that the second transistor is turned off. To eliminate the influence of the internal resistance of the battery on the measurement of the battery voltage, the battery voltage ~ -,' -- ' ' ' ~55~373 determines only at the end of the flyback interval, i.e.
at the instant when the charge current becomes zero, whether the second transistor remains actually turned on and hence whether the next forward interval is blocked.
However, the following problem occurs in these circuits. When the second transistor is turned on during the flyback interval by a battery voltage above the first value of the switching amplifier, this second transistor is to be turned off again if the battery voltage is not above this value at the end of the flyback interval. It takes some time to turn off the second transistor as a result of the presence of capacitive charges. This delays the initiation of the next forward interval, which disturbs the satisfactory operation of the circuit.
lS It is therefore an object of the invention to provide a power supply circuit obviating this problem.
According to the invention, a power supply circuit of the type mentioned in the opening paragraph is characterized in that the first input of the switching amplifier is coupled by means of a second rectifier diode to the junction of the secondary winding and the first rectifier diode and that the forward direction of the second rectifier diode, reckon-ed from this junction, is the same as that of the first rectifier diode.
Due to the measure according to the invention two conducting diodes having, however, opposite polarities, are present between the first and the second input of~ the switching amplifier during a flyback interval, so that no voltage is present between these inputs. Consequently the switching amplifier is not activated during a flyback interval. At the end of a flyback interval the secondary voltage and the secondary current become ~ero. The voltage at the junction of the secondary winding and the first diode subsequently increases again so that the two rectifier diodes are cut off. However, it takes some time before the first transis-tor is turned on via the positive feedback of the capacitor between the secondary winding and the base of this transis-tor and the next forward interval is initiated. This time , ...
' ' '.
`" 125~373 PHN 11 596 -~- 4-3-1986 is utilized to measure the battery voltage. At a battery voltage above the first value the second transistor is turned on by the switching amplifier so that the next forward interval is blocked until the battery voltage has decreased to below the second value.
An embodiment of a power supply circuit according to the invention is characterized in that the switch is constituted by a third transistor of a conductivity type which is opposed to that of the first transistor, and whose 0 emitter-collector path is disposed between the battery terminal facing the first transistor and the end of the voltage divider facing this terminal and whose base is coupl-- ed by means of a third rectifier diode to the junction of the secondary winding and the first rectifier diode.
During a flyback interval the voltage at the junction of the secondary winding and the first diode is negative so that the third transistor is turned on via the third diode and consequently the voltage divider is arranged between the connection terminals of the battery.
This embodiment can be futher characterized in that the base of the third transistor is further coupled by means of a fourth rectifier diode to the connection terminal of the battery facing the first tranSiStOE~ the fourth rectifier diode being preferably a light-emitting diode. Apparrently, this diode lights up during rapid charge and flashes during trickle charge thus informing the user on the fully charged condition of the battery.
To ensure that the voltage divider is not arranged between the connection terminals of the battery during the forward intervals~ a further embodiment may be character-ized in that the base of the third transistor is also coupled by means of a resistor to the collector of the second transistor. Due to this measure the third transistor is also immediately turned on at the instant when the second transistor is turned on.
Still a further embodiment is characterized in that the base of the third transistor is connected by means of a second capacitor to a tap, separated with respect to d.c. current from the secondary winding, in the positive ~ll25~373 feedback between the secondary winding and the base of the first transistor.
Thus it is achieved that if the battery voltage is not above the first value, at the end of a flyback interval, the third transistor is rapidly turned off prior to the next forward interval being fully initiated.
In a power supply circuit according to the in-vention the switching amplifier may be constituted by a Schmitt trigger. A suitable embodiment thereof may be o characterized in that the Schmitt trigger is constituted by a fourth transistor of a conductivity type which is the same as that of the first transistor and whose base is coupled to the first input and the emitter is coupled to the second input and whose collector is connected by means of the parallel arrangement of a second resistor and the base-emitter junction of a fifth resistor of a conductivity type opposed to that of the fourth transistor to the con-nection terminal of the battery facing the first transistor, th collector of said fifth transistor being coupled by means of a third resistor to the base of the fourth transistor and also to the base of the second transistor.
The invention will be further described with ` reference to the accompanying drawing in which Figure 1 shows a principle circuit diagram of the power supply circuit according to the invention, Figure 2 shows a first embodiment of a power supply circuit according to the invention, Figure 3 shows a second embodiment of a power supply circuit according to the invention, and Figure 4 shows a third embodiment of a power supply circuit according to the invention.
Figure 1 shows a principle circuit diagram of a power supply circuit according to the invention. The circuit has two input terminals 2 and 3 for applying an input volt-age which may be both a rectified alternating voltage and a direct voltage. The series arrangement of a primary wind-ing n1 of a transformer Tr, the collector-emitter path of a first transistor T1, the series arrangement of a secondary winding n2 and a first rectifier diode D1 with connection terminals 4 and 5 between which a battery 6 is connected, and a first resistor R1 is incorporated between these ter-minals 2 and 3. In this example the battery 6 is formed by two series-arranged nickel cadmium accumulator cells 7 and 8. A d.c. motor M of, for example, a shaver may be arranged in parallel with this battery 6 by means of a switch S2. In that case a resistor R6 is arranged in paral-lel with the resistor R1, simultaneously with the aid of a switch S3. A positive feedback constituted by the series arrangement of a first capacitor C1 and a resistor R2 is arranged between the junction 9 of the secondary winding n2 and the diode D1 and the base of transistor T1. The base pf transistor T1 is also connected via a starting resis-tor R5 to the input terminal 2. It is to be noted that thecircuit may alternatively be started in manners other than with this resistor R5. The resistor R1 is connected to the base of a second transistor T2 whose collector is coupled to the base of the first transistor T1. Further-more a switching amplifier 10 having a first input 11,a second input 12 and an output 13 is arranged between the connection terminals 4 and 5 of the battery 6. The first input 11 is connected` to a tap 14 of a voltage divider con-stituted by resistors R3 and R4, resistor R3 being con-nected by means of a switch S1 to the connection terminal4 and resistor R4 being connected to the connection terminal 5 of the battery 6. Furthermore the first input 11 is con-nected by means of a diode D2 to the junction 9 of the secondary winding n2 and diode D4. The forward direction of diode D2, viewed from the junction 9, is the same as that of diode D1. The second input 12 is connected to the connection terminal 5, whilst the output 13 is con-nected to the base of the second transistor T2.
The circuit operates as follows. The switches S2 and S3 are initially open and the circuit thus only provides the charge current for the accumulator cells 7 and 8. In the presence of an input voltage across the termina]s 2 and 3 a small current flows via the starting ~:5~373 resistor S5 in the base of transistor T1 so that it is partly rendered conducting. The resultant current through the primary winding n1 results in an increase of the voltage across the secondary winding n2 so that transistor T1 is further rendered conducing via the positive feedback of capacitor C1 and resistor R1. Due to this positive feed-back transistor T1 is then rapidly driven into saturation.
The current through the primaray winding n1 subsequently increases linearly in time during the so-called forward interval. At a level of the primary current determined by the resistance of resistor R1 transistor T2 is turned on so that transistor T1 is turned off. Due to the interruption of the primary current the polarity of the voltage across the secondary winding n2 is reversed so that diode D1 becomes conducting. The energy stored in the transformer Tr during the forward interval is then applied in the form of a charge current to the battery 6 during the so-called flyback interval. This current decreases linearly in time to zero.
During the flyback interval the voltage at the junction 9 is negative and is equal to the voltage across the diode D1.
At the end of the flyback interval the voltage across the winding n2 becomes equal to zero volt so that the voltage at the end 9 becomes equal to the battery voltage. This positive voltage step at the junction 1'19 ensures the initiation of the next forward interval via the positive feedback of capacitor C1 and resistor R2.
In the manner described above the accumulator cells 7 and 8 can be charged relatively rapidly with a comparatively large current. To prevent damage of the accumulator cells due to overcharge, the power supply cir-cuit is provided with a switching device switching off the power supply circuit when the accumulator cells 7 and 8 are full. Its operation will now be further explained.
The voltage divider with resistors R3 and R4 is connected between the connection terminals 4 and 5 of the battery 6 by means of the switch S1 during a flyback interval. A fraction of the battery voltage would then be present across the resistor R4 and it would also be present ` .~l2~3~3 between the first and the second inputs 11 and 12 of the switching amplifier 10. This is, however, prevented by the second rectifier diode D2.
At the beginning of a flyback interval the voltage across the secondary winding n2 reverses its polarity so that the voltage at the junction 9 becomes negative. Consequently not only diode D1 but also diode D2 becomes conducting.
Two conducting diodes having, however, opposite polarities are then present between the inputs 11 and 12 of the switching amplifier 10 so that there is no voltage between these inputs. Thus, no information about the magnitude of the battery voltage is presented to the switching ampli-fier 10 during a flyback interval. As already stated, a voltage step occurs at the end 9 of the secondary winding n2 at the end of the flyback interval. This step is passed on with a certain delay by the positive feedback of capaci-tor C1 and resistor R2 to the base of transistor T1 so that it takes some time after the end of a flyback interval before transistor T1 is rendered fully conducting again.
Since the swltch S1 is also opened with a certain delay, the battery voltage can be measured in this time without the internal resistance of the accumu~tor cells 7 and 8 in-fluencing this measurement. Due to the voltage step at the junction 9 at the end of a flyback interval diode D2 is in fact cut off so that then the fraction of the battery voltage present across the resistor R4 is present between the inputs 11 and 12 of the switching amplifier 10. If this voltage is higher than a first threshold value, the voltage at the output 13 switches over from a low to a high value.
Consequently transistor T2 is turned on and transistor T1 is turned off so that the further initiation of the next forward interval is blocked. The battery voltage is then to decrease to below the second threshold value of the switching amplifier 10 before transistor T2 is turned off again and transistor T1 can become conducting again via the starting resistor R5. In this manner there is a change over from rapid charge to trickle charge.
If the switches S2 and S,3 are closed, the motor M is .~ .
~25~373 arranged in parallel with the battery 6. The power supply circuit then also supplies the motor current. The value of the primary current at which the transistor T1 is turned off is then determined by the parallel arrangement of the resistors R1 and R6.
Figure 2 shows a first embodiment of the power supply circuit according to the invention. The same com-ponents are denoted by the same reference numerals as in Figure 1. In -this embodiment the mains voltage is applied via two terminals 20 and 21 to a rectifier bridge G. The rectified voltage is smoothed with the aid of a filter 22 constituted by two capacitors C3 and C4 and a coil L1 and is subsequently applied to the primary winding n1 of the transformer. A Zener diode Z1 in series with a lS diode D5 is arranged in parallel with this winding n1 with which diode voltage peaks are suppressed when switching off the current through the primary winding. Furthermore transistor T2 is coupled to resistor R1 by means of a voltage divider with resistors R7 and R8 in this embodiment.
20 The switch S1 is constituted by a PNP transistor T3 whose emitter is connected to the connection terminal 4 of the battery 6 and whose collector is connected to the resistor R3 of the voltage divider. A resistor R11 is provided between the emitter and the base of tra~sistor T3. This base is connected by means of the series arrangement of a resistor R1o and a third rectifier diode D3 to the junction 9 of the secondary winding n2 and the diode D1 and further-more by means of a resistor R12 to the collector of transistor T2. The junction 10 of resistor R10 and diode 30 D3 is connected by means of a series arrangement of a resistor R13 and a light-emitting diode D4 to the connect-ion terminal 4 of the battery 6. During a forward interval the voltage at the end 9 is positive relative to the end 4 of the secondary winding n2. Therefore transistor T3 will not be conducting during a forward interval. However, the connection between the base of transistor T3 via resistor R12 and the base of transistor T1 certainly prevents tran-sistor T3 from being turned on during a forward interval.
. . , ~L~ 33~3 In factt the positive base-emitter voltage of transistor T1 is then present between the base and emitter of transis-tor T3. At the end of the forward interval transistor T2 is rapidly driven into saturation so that transistor T1 is turned off. Consequently, the voltage at the base of transis-tor T3 is decreased via resistor R12 so that transistor T3 is turned on. By reversing of the polarity of the voltage across the secondary winding n2 the voltage at the end 9 becomes negative so that diode D3 becomes conducting and transistor T3 is maintained turned on. Transistor T3 is then entirely driven into saturation so that the voltage drop across the collector-emitter path of this transistor is negligible. Due to the diode D3 becoming conducting a cur-rent will also start flowing through the light-emitting diode D4. During rapid charge this diode will appear to be continuously on due to the high frequency of the flyback intervals, whereas during trickle charge this diode will flash. The switching amplifier 10 has an npn transistor T4 whose base constitutes the first input 11 and whose emitter constitutes the second input 12. The collector of this transistor is connected by means of the series arrangement of a resistor R15 and the base-emitter junction of a pnp transistor T5 to the connection terminal 4 of the battery. The collector of this transistor T5 is coupled by means of a resistor R16 to the base of transistor T4 and is furthermore coupled by means of a resistor R17 to the output 13. In this embodiment the voltage divider has a resi~
tor R14 with a positive temperature coefficient which, together with the negative temperature coefficient of the base-emitter voltage of transistor T4, ensures that the temperature coefficient of the threshold voltage of the switching amplifier is adapted to the temperature coeffi-cient of the accumulator cells, which is negative. The switching amplifier 10 constitutes a Schmitt trigger whose operation is assumed to be known and will not be further explained. When the voltage across the resistor R4 exceeds the first threshold value after the end of a flyback inter-val, transistor T2 is turned on via the Schmitt trigger .~
~59373 PHN 11 596 ~ 10-3-1986 10 and the power supply circuit is switched off. Transis-tor T3 is then maintained saturated by means of resistor R12. ~,~hen the battery voltage subsequently decreases to below a second threshold value determined by the resistor R16, transistor T2 is turned off again and the power supply circuit can start again. When the voltage across re-sistor R4 does not exceed the first threshold value of the Schmitt trigger after the end of a flyback interval, the subsequent forward interval is initiated again via the posi-tive feedback of capacitor C1 and resistor R2. TransistorT3 should then be turned off before transistor T1 is turned on. This is realiæed by a capacitor C2 which is disposed be-tween the base of transistor T3 and the junction 15 of ca-pacitor C1 and resistor R2.
Figure 3 shows a second embodiment of a power supply circuit according to the invention in which the same components have the same reference numerals as those in Figure 2. The difference between this embodiment and that of Figure 2 is that resistor R1 is now disposed be-tween transistor T1 and the connection terminal 4 of the battery 6. The resistor R1 is coupled to the base of transistor T2 by means of a Zener diode Z2 During a for-ward interval Zener diode Z2 breaks down at a given value of the primary current so that transistor T2 is turned on and consequently transistor T1 is turned off. Otherwise, the operation of the circuit is the same as that of Figure
2.
Figure 4 shows a third embodiment of a power sup-ply circuit according to the invention. The same components are denoted by the same reference numerals as in Figure 2.
The power supply circuits shown in Figures 1, 2 and 3 provide a constant mean output current at a given input voltage~ This output current is, however, dependent on the input voltage. An increasing input voltage leads to an increasing base current of the first transistor T1 via the positive feedback between the secondary winding n2 and the base of this transistor. Consequently transistor T1 is each time driven into further saturation with S~3373 increasing input voltages so that an increasing delay occurs upon turning off transistor T1 after the switch-off level of the primary current has been reached. The primary current therefore has an increasing overshoot at increasing input voltages, which results in an in~reasing mean output current.
However, the output current of the power supply circuit is to remain wi~hin a given range in order to prev~nt damage of the batteries and/or the motor and the electronics of the circuit due to a too large current at high inpu~ voltages and in order to be able to æupply a sufficient charge current for the batteries and~or the supply current for the motor at low input voltages.
In order that the power supply circuit can be used at the mains voltages present in the various countries withou~ any adaptation or switch-over, a base-current compensation is employed in the circuit of Figure 4, which realizes that the base-current of transistor T1 does not increase any further above a given input voltage. It i5 to be noted that this base-current compensation is described in the Canadian Patent Application Serial No. 499,735 flled on January 10, 1986, assigned to the assignee of the present application. In this embodiment the positive feedback is constltuted by the series arrangement of a resistor R18, capacitor C1 and resis~or R2, whilst the first two elements may be interchanged. Furthermore the connection terminal 4 of the battery 6 is connected by means of a Zener diode Z2 to the junction 15 of resistor R2 and capacitor C1.
During a forward interval the maximum voltage at the end 9 of the secondary winding n2 is determined by the input voltage 5~373 and the transformation ratio of transformer Tr. At comparatively low lnput voltages the Zener diode Z2 is not yet conducting durlng a forward interval. The base current of transistor Tl is then determlned by the voltage difference between ~he positive end 9 of winding n2 and the base of transistor Tl and by the resistance of the reslstors R2 and R18. At an increasing input voltage the voltage at the junction 15 of capacitor Cl and resiætor R2 increases due to the increasing base current, so that 12a 12S~73 P~N 11 596 -13- 10-3-1986 at a given input voltage the Zener diode Z2 becomes conduct-ing during a forward interval. The base current is then determined by the difference between the Zener voltage and the base-emitter voltage of the transistor T1 and by the resistance of resistor R2. In the case of a further in-crease of the input voltage the further increase of the base current is removed via the Zener diode Z2 to the emitter of transistor T1. The base current of transistor T1 thus does not increase any further, so that transistor T1 is not further driven into saturation at increasing input voltages. This prevents an increasing turn-off delay from occurring at increasing input voltages. The output current of the circuit thus remains within the range in which the accumulator cells 7 and 8 and the electronics of the circuits are not damaged by a too large current.
In addition to the base current compensation shown, the power supply circuit according to the invention may also be provided with a compensation for the frequency increasing at an increasing input voltage and hence an in-creasing mean output current of the circuit. This increasingfrequency is caused because the primary current increases more and more rapidly during a forward interval in the case of an increasing input voltage so that also the level at which the transistor T1 is turned off is reached more and more rapidly. Such compensations are known, for example, from European Patent Specification 30 026 and British Patent ~pplication 2,138,977.
The invention is not limited to the embodiments shown. For example, the switching amplifier may alternati-vely be constructed in different manners.
Figure 4 shows a third embodiment of a power sup-ply circuit according to the invention. The same components are denoted by the same reference numerals as in Figure 2.
The power supply circuits shown in Figures 1, 2 and 3 provide a constant mean output current at a given input voltage~ This output current is, however, dependent on the input voltage. An increasing input voltage leads to an increasing base current of the first transistor T1 via the positive feedback between the secondary winding n2 and the base of this transistor. Consequently transistor T1 is each time driven into further saturation with S~3373 increasing input voltages so that an increasing delay occurs upon turning off transistor T1 after the switch-off level of the primary current has been reached. The primary current therefore has an increasing overshoot at increasing input voltages, which results in an in~reasing mean output current.
However, the output current of the power supply circuit is to remain wi~hin a given range in order to prev~nt damage of the batteries and/or the motor and the electronics of the circuit due to a too large current at high inpu~ voltages and in order to be able to æupply a sufficient charge current for the batteries and~or the supply current for the motor at low input voltages.
In order that the power supply circuit can be used at the mains voltages present in the various countries withou~ any adaptation or switch-over, a base-current compensation is employed in the circuit of Figure 4, which realizes that the base-current of transistor T1 does not increase any further above a given input voltage. It i5 to be noted that this base-current compensation is described in the Canadian Patent Application Serial No. 499,735 flled on January 10, 1986, assigned to the assignee of the present application. In this embodiment the positive feedback is constltuted by the series arrangement of a resistor R18, capacitor C1 and resis~or R2, whilst the first two elements may be interchanged. Furthermore the connection terminal 4 of the battery 6 is connected by means of a Zener diode Z2 to the junction 15 of resistor R2 and capacitor C1.
During a forward interval the maximum voltage at the end 9 of the secondary winding n2 is determined by the input voltage 5~373 and the transformation ratio of transformer Tr. At comparatively low lnput voltages the Zener diode Z2 is not yet conducting durlng a forward interval. The base current of transistor Tl is then determlned by the voltage difference between ~he positive end 9 of winding n2 and the base of transistor Tl and by the resistance of the reslstors R2 and R18. At an increasing input voltage the voltage at the junction 15 of capacitor Cl and resiætor R2 increases due to the increasing base current, so that 12a 12S~73 P~N 11 596 -13- 10-3-1986 at a given input voltage the Zener diode Z2 becomes conduct-ing during a forward interval. The base current is then determined by the difference between the Zener voltage and the base-emitter voltage of the transistor T1 and by the resistance of resistor R2. In the case of a further in-crease of the input voltage the further increase of the base current is removed via the Zener diode Z2 to the emitter of transistor T1. The base current of transistor T1 thus does not increase any further, so that transistor T1 is not further driven into saturation at increasing input voltages. This prevents an increasing turn-off delay from occurring at increasing input voltages. The output current of the circuit thus remains within the range in which the accumulator cells 7 and 8 and the electronics of the circuits are not damaged by a too large current.
In addition to the base current compensation shown, the power supply circuit according to the invention may also be provided with a compensation for the frequency increasing at an increasing input voltage and hence an in-creasing mean output current of the circuit. This increasingfrequency is caused because the primary current increases more and more rapidly during a forward interval in the case of an increasing input voltage so that also the level at which the transistor T1 is turned off is reached more and more rapidly. Such compensations are known, for example, from European Patent Specification 30 026 and British Patent ~pplication 2,138,977.
The invention is not limited to the embodiments shown. For example, the switching amplifier may alternati-vely be constructed in different manners.
Claims (10)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A power supply circuit for charging a battery, comprising a first series arrangement of a primary winding of a transformer,a first transistor, a first resistor and a second series arrangement of a secondary winding of the transformer and a first rectifier diode, said second series arrangement being provided with connection terminals for connecting the battery, and comprising a positive feedback provided with a first capacitor between the junction of the secondary winding and the first rectifier diode and the base of the first transistor, a second transistor coupled to the first resistor for turning off the first transis-tor, and furthermore comprising a switching amplifier arranged between the connection terminals of the battery for turning on the second transistor above a first value of the battery voltage and for turning off the second transistor below a second value of the battery voltage below the first value, said switching amplifier having a first input, a second input and an output, said first input being coupled to a tap on a voltage divider which is arranged between the connection terminals of the battery by means of a switch during the periods when the first transistor is turned off, said second input being coupled to the connection terminal of the battery facing the first rectifier diode, and said output being coupled to the base of the second transistor, characterized in that the first input of the switching amplifier is coupled by means of a second rectifier diode to the junction of the secondary winding and the first rectifier diode and that the forward direction of the second rectifier diode, reckoned from this junction, is the same as that of the first rectifier diode.
2. A power supply circuit as claimed in Claim 1, characterized in that the switch is constituted by a third transistor of a conductivity type which is opposed to that of the first transistor, and whose emitter-collector path is disposed between the battery terminal facing the first transistor and the end of the voltage divider facing said terminal and whose base is coupled by means of a third rectifier diode to the junction of the secondary winding and the first rectifier diode.
3. A power supply circuit as claimed in claim 2, characterized in that the base of the third transistor is further coupled by means of a fourth rectifier diode to the connection terminal of the battery facing the first transistor.
4. A power supply circuit as claimed in claim 3, characterized in that the fourth rectifier diode is a light-emitting diode.
5. A power supply circuit as claimed in claim 2, 3 or 4, characterized in that the base of the third transistor is also coupled by means of a resistor to the collector of the second transistor.
6. A power supply circuit as claimed in claim 2, 3 or 4, characterized in that the base of the third transistor is connected by means of a second capacitor to a tap, separated with respect to d.c. current from the secondary winding, in the positive feedback between the secondary winding and the base of the first transistor.
7. A power supply circuit as claimed in claim 1, characterized in that the switching amplifier is constituted by a Schmitt trigger.
8. A power supply circuit as claimed in claim 7, characterized in that the Schmitt trigger is constituted by a fourth transistor of a conductivity type which is the same as that of the first transistor and whose base is coupled to the first input and the emitter is coupled to the second input and whose collector is connected by means of the parallel arrangement of a second resistor and the base-emitter junction of a fifth transistor of a conductivity type opposed to that of the fourth transistor to the connection terminal of the battery facing the first transistor, the collector of said fifth transistor being coupled by means of a third resistor to the base of the fourth transistor and also to the base of the second transistor.
9. A power supply circuit as claimed in claim 1, 2 or 3, characterized in that the circuit is provided with a second switch for arranging a motor in parallel with the battery, and with a third switch for simultaneously arranging a fourth resistor in parallel with the first resistor.
10. A shaver, characterized in that it is provided with a power supply circuit as claimed in claim 1, 2 or 3.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL8503479A NL8503479A (en) | 1985-12-18 | 1985-12-18 | POWER SUPPLY. |
| NL8503479 | 1985-12-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1259373A true CA1259373A (en) | 1989-09-12 |
Family
ID=19847030
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000525272A Expired CA1259373A (en) | 1985-12-18 | 1986-12-15 | Power supply circuit |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US4684871A (en) |
| EP (1) | EP0226253B1 (en) |
| JP (1) | JPH0736672B2 (en) |
| KR (1) | KR930011803B1 (en) |
| AT (1) | ATE56568T1 (en) |
| CA (1) | CA1259373A (en) |
| DE (1) | DE3674164D1 (en) |
| HK (1) | HK33994A (en) |
| NL (1) | NL8503479A (en) |
Families Citing this family (23)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1330828C (en) * | 1987-10-09 | 1994-07-19 | Jiri K. Nor | Battery charger |
| DE3742613A1 (en) * | 1987-12-16 | 1989-06-29 | Braun Ag | ELECTRONIC SWITCHING POWER SUPPLY WITH A THROTTLE CONVERTER |
| CA1311268C (en) * | 1988-04-11 | 1992-12-08 | Karl Kordesch | Method and a taper charger for the resistance free charging of a rechargeable battery |
| DE8906689U1 (en) * | 1988-06-06 | 1989-08-24 | Altus Corp., San Jose, Calif., Us | |
| US5055763A (en) * | 1988-09-26 | 1991-10-08 | Eveready Battery Company, Inc. | Electronic battery charger device and method |
| US4969077A (en) * | 1989-02-14 | 1990-11-06 | U.S. Philips Corporation | Power supply circuit |
| US5101334A (en) * | 1989-02-14 | 1992-03-31 | U.S. Philips Corporation | High speed power supply circuit with circuit with positive feedback |
| US4939632A (en) * | 1989-02-14 | 1990-07-03 | U.S. Philips Corporation | Power supply circuit |
| US4965506A (en) * | 1989-02-14 | 1990-10-23 | U.S. Philips Corporation | Power-supply circuit having circuitry for switching from a battery charging mode to a battery trickle-charging mode |
| FR2654876B1 (en) * | 1989-11-23 | 1993-11-12 | Commissariat A Energie Atomique | DEVICE FOR CHARGING MEANS OF ACCUMULATING ELECTRICAL ENERGY, PROVIDED WITH MEANS FOR CONTROLLING THIS LOAD. |
| DE4212041A1 (en) * | 1992-04-10 | 1993-10-14 | Braun Ag | Electronic switching power supply |
| DE4241065C1 (en) * | 1992-12-05 | 1994-03-31 | Braun Ag | Electronic switching power supply for feeding an accumulator |
| DE4337461A1 (en) * | 1993-11-03 | 1995-05-04 | Braun Ag | Switching power supply |
| US5610804A (en) * | 1994-06-20 | 1997-03-11 | Tdk Corporation | Power supply with dual energy transfer circuits for power factor correction |
| US5581170A (en) * | 1994-12-12 | 1996-12-03 | Unitrode Corporation | Battery protector |
| US5652501A (en) * | 1994-12-12 | 1997-07-29 | Unitrode Corporation | Voltage sensor for detecting cell voltages |
| WO1997020379A1 (en) * | 1995-11-27 | 1997-06-05 | Philips Electronics N.V. | Power-supply circuit |
| DE69706490T2 (en) * | 1996-03-01 | 2002-05-16 | Koninkl Philips Electronics Nv | POWER CIRCUIT |
| DE19614816C1 (en) * | 1996-04-15 | 1997-06-19 | Braun Ag | Electronic switched network supply stage |
| FR2789818B1 (en) * | 1999-02-16 | 2001-03-09 | Advanced Electromagnetic Syste | FAST BATTERY CHARGER |
| FR2830383B1 (en) * | 2001-10-02 | 2004-09-10 | Somfy | VOLTAGE CONVERTER |
| EP2571150A3 (en) | 2011-09-16 | 2018-02-28 | Braun GmbH | Power-supply circuit for an electrical appliance having a battery and a dc-to-dc converter |
| CN110050400B (en) * | 2016-12-01 | 2023-05-02 | 集成装置技术公司 | Battery charging system |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3531706A (en) * | 1967-04-28 | 1970-09-29 | Gen Electric | Rapid charge rates for sealed cells |
| NL7706447A (en) * | 1977-06-13 | 1978-12-15 | Philips Nv | DEVICE FOR POWERING A DC MOTOR CONTAINING A BATTERY BATTERY. |
| WO1981001634A1 (en) * | 1979-11-29 | 1981-06-11 | K Becker | Switching device for regulating the supply of a consumer apparatus |
| JPS56115141A (en) * | 1980-02-14 | 1981-09-10 | Matsushita Electric Works Ltd | Automatic voltage changing type charger |
| US4376263A (en) * | 1980-11-06 | 1983-03-08 | Braun Aktiengesellschaft | Battery charging circuit |
| DE3218594A1 (en) * | 1982-05-17 | 1983-12-22 | Braun Ag, 6000 Frankfurt | ELECTRONIC SWITCHING POWER SUPPLY |
-
1985
- 1985-12-18 NL NL8503479A patent/NL8503479A/en unknown
-
1986
- 1986-03-28 US US06/845,659 patent/US4684871A/en not_active Expired - Lifetime
- 1986-12-10 DE DE8686202222T patent/DE3674164D1/en not_active Expired - Lifetime
- 1986-12-10 EP EP86202222A patent/EP0226253B1/en not_active Expired - Lifetime
- 1986-12-10 AT AT86202222T patent/ATE56568T1/en not_active IP Right Cessation
- 1986-12-15 CA CA000525272A patent/CA1259373A/en not_active Expired
- 1986-12-15 KR KR1019860010716A patent/KR930011803B1/en not_active IP Right Cessation
- 1986-12-18 JP JP61300165A patent/JPH0736672B2/en not_active Expired - Lifetime
-
1994
- 1994-04-14 HK HK33994A patent/HK33994A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| HK33994A (en) | 1994-04-22 |
| JPS62155734A (en) | 1987-07-10 |
| EP0226253A1 (en) | 1987-06-24 |
| DE3674164D1 (en) | 1990-10-18 |
| US4684871A (en) | 1987-08-04 |
| KR870006691A (en) | 1987-07-14 |
| NL8503479A (en) | 1987-07-16 |
| ATE56568T1 (en) | 1990-09-15 |
| JPH0736672B2 (en) | 1995-04-19 |
| KR930011803B1 (en) | 1993-12-21 |
| EP0226253B1 (en) | 1990-09-12 |
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