WO1999020085A1

WO1999020085A1 - Electric lamp circuit and structure using light emitting diodes

Info

Publication number: WO1999020085A1
Application number: PCT/KR1998/000306
Authority: WO
Inventors: Byung Hyo Min; Chan Koo Jeon; Ir Bong Jeon; Wan Ho Oh
Original assignee: Se Kang Electric Co., Ltd.
Priority date: 1997-10-10
Filing date: 1998-10-08
Publication date: 1999-04-22
Also published as: AU9465498A

Abstract

An electric lamp circuit comprising a light emitting circuit (41) including a plurality of LEDs (D11..DMN) arranged in a matrix form of M rows x N columns, a power source (42) for supplying an AC voltage to the light emitting circuit, and a variable resistor circuit (43) for adjusting the amount of current flowing to the light emitting circuit (41). The LEDs (D11..DMN) are arranged in a net form. Therefore, eventhough a specific one of the LEDs (D11..DMN) fails, the other LEDs of the same row can normally be turned on. As a result, the failed LED is readily distinguishable, resulting in a reduction in failure repair working time. Further, a variation in the AC voltage is compensated so that the amount of current flowing to the light emitting circuit (41) can be maintained within a predetermined range. Therefore, a lighting failure of the light emitting circuit (41) can be avoided and overcurrent can be prevented from flowing to the light emitting circuit (41). These have the effect of extending the product's life span. Moreover, an ambient brightness of a lamp is sensed and a light intensity of the light emitting circuit (41) is adjusted in accordance with the sensed result, thereby reducing power consumption. Further, a circuit regenerator (79, 88) is provided to, eventhough all LEDs of a specific column fail, transfer current to LEDs or the subsequent column, thereby preventing operation incapability.

Description

ELECTRIC LAMP CIRCUIT AND STRUCTURE USING LIGHT EMITTING DIODES

Technical Field

The present invention relates in general to electric lamp circuits and structures for application to traffic signal lamps, street lamps and others, and more particularly to an electric lamp circuit and structure using light emitting diodes, which can generate high luminance using low power.

Background Art

Traffic signal lamps are generally disposed in crosswalks of crossroads to indicate vehicle or pedestrian passage. A conventional traffic signal lamp is provided with one electric bulb, resulting in frequent failure and a large amount of power consumption. A structure with a plurality of light emitting diodes (referred to hereinafter as LEDs) connected in series has therefore been proposed to overcome such a problem.

Figs. 1 and 2 show examples of conventional electric lamp circuits applied to traffic signal lamps.

In Fig. 1, the reference numeral 11 denotes a light emitting circuit which is provided with a plurality of LEDs D_n, D₁₂, ..., D_MN arranged in a matrix form of M rows x N columns. The reference numeral 12 denotes a power source which supplies an alternating current (AC) voltage to the light emitting circuit 11. The reference numeral 13 denotes a variable resistor which forms a closed loop with the light emitting circuit 11 and power source 12 and adjusts the amount of current flowing to the light emitting circuit 11.

In the light emitting circuit 11, the LEDs D_π, D₁₂, ..., D,^ are connected in series in respective rows in such a manner that they have the same polarities in the respective rows. The light emitting circuit 11 consists of a first LED group 11A turned on for a positive (+) half period of the AC voltage from the power source 12, and a second LED group

1 IB turned on for a negative (-) half period of the AC voltage. Although the first and second LED groups 11A and 1 IB are alternately turned on, they seem to remain turned on, because the power source 12 typically has a frequency of 60Hz.

In Fig. 2, the reference numeral 21 denotes a light emitting circuit which is provided with a plurality of LEDs D_π, D₁₂, ..., D^ arranged in a matrix form of M rows x N columns. The reference numeral 22 denotes a power source which supplies an AC voltage. The reference numeral 23 denotes a bridge rectifier which full-wave rectifies the AC voltage from the power source 22 to supply a direct current (DC) voltage to the light emitting circuit 21. The reference numeral 24 denotes a variable resistor which forms a closed loop with the light emitting circuit 21 and bridge rectifier 23 and adjusts the amount of current flowing to the light emitting circuit 21.

In the light emitting circuit 21, the LEDs D_π, D₁₂, ..., D^ are connected in series in respective rows and have the same polarity.

However, the above-mentioned conventional electric lamp circuits using the LEDs have a disadvantage in that the LEDs are connected in series in respective rows. Namely, if any one of the LEDs fails, no current flows to any of the LEDs connected in the row to which the failed

LED belongs, thereby causing them not to be turned on.

Furthermore, all of the LEDs belonging to the row corresponding to the failed LED must be tested for finding out the failed LED, resulting in an increase in working time and, thus, a degradation in working efficiency.

In order to solve the above-mentioned problems, there has been proposed a circuit for, even though any one of a plurality of lamps connected in series fails, allowing all of the remaining lamps not to be turned off. Such a circuit is shown in Fig. 3.

With reference to Fig. 3, a plurality of lamps LI, L2 and L3 are connected in series to a power source 30, and symmetrical Zener diodes VRD1, VRD2 and VRD3 are connected in parallel respectively to the lamps LI, L2 and L3. Each of the symmetrical Zener diodes VRD1, VRD2 and VRD3 has a Zener voltage slightly higher than a peak value of a voltage which is applied across the lamp at a normal state.

In Fig. 3, if a specific one of the lamps is short-circuited, a voltage higher than the Zener voltage is applied to the symmetrical Zener diode connected in parallel to the specific lamp, resulting in breakdown. As a result, current flows through the symmetrical Zener diode connected in parallel to the specific lamp and is then supplied to the other lamps to normally turn them on.

Alternatively, thermistors which convert temperatures into resistances may be used instead of the symmetrical Zener diodes VRD1, VRD2 and VRD3. 5 In this case, if a specific one of the lamps is short-circuited, a high voltage is applied to the thermistor connected in parallel to the specific lamp, to heat it. Then, as the thermistor connected in parallel to the specific lamp is reduced in resistance, current flows therethrough, thereby normally turning the other lamps on. 0 In the circuit of Fig. 3, even if one light emitter fails, the other light emitters are normally turned on. This solves the entire failure. However, the above-mentioned circuit is disadvantageous in that one symmetrical Zener diode is connected in parallel to every light emitter, resulting in an increase in the number of components. The increased number of 5 components then results in an increase in manufacturing cost of products and hinders miniaturization thereof. In particular, recently, because several tens to hundreds of light emitters are used in an electric lamp circuit applied to traffic signal lamps, etc., the same number of symmetrical Zener diodes or thermistors are thus required therein. o Moreover, the above-mentioned conventional electric lamp circuits have a further disadvantage in that they have no method capable of coping with a variation in a drive voltage applied thereto. In this connection, if the drive voltage falls below a first threshold value, all LEDs are not turned on, and so the associated lamp loses its function such as, for 5 example, a traffic signal function. In the case where the drive voltage rises above a second threshold value, current larger than a predetermined value flows to the LEDs, thereby shortening their life span.

Disclosure of the Invention

Therefore, the present invention has been made in view of the o above problems, and it is an object of the present invention to provide an electric lamp circuit using LEDs, in which the LEDs are connected in parallel in respective columns in a light emitting circuit, so that, even though a specific one of the LEDs fails, the other LEDs of the same row can normally be turned on. 5 It is another object of the present invention to provide an electric lamp circuit using LEDs, in which there is provided a circuit for detecting the amount of current flowing to a light emitting circuit and correcting a voltage variation on the basis of the detected result, thereby avoiding luminance degradation and lighting failure and preventing overcurrent 5 from flowing to the light emitting circuit.

It is another object of the present invention to provide an electric lamp circuit using LEDs, in which a power device for analog control or pulse width modulation is used instead of a variable resistor to adjust the amount of current flowing to a light emitting circuit, thereby reducing 0 power consumption.

It is another object of the present invention to provide an electric lamp circuit using LEDs, which is capable of sensing an ambient brightness of a lamp and adjusting a light intensity of a light emitting circuit in accordance with the sensed result, thereby reducing power 5 consumption.

It is a further object of the present invention to provide an electric lamp circuit using LEDs, in which a circuit regenerator is provided to, even though all the LEDs of a specific column fail, transfer current to the

LEDs of the subsequent column, thereby preventing operation o incapability.

It is yet another object of the present invention to provide an LED detachable lamp structure in which a plurality of connectors are disposed on an LED board and each of them has a plurality of pin holes internally interconnected and respectively receiving lead terminals of LEDs 5 constituting a light emitting circuit, in such a manner that the LEDs are detachable to make failure repairs easier.

In accordance with a first aspect of the present invention, there is provided an electric lamp circuit comprising light emitting means including a plurality of LEDs arranged in a matrix form of M rows x N o columns; power supply means for supplying an AC voltage to the light emitting means; and variable resistor means for forming a closed loop with the light emitting means and power supply means and adjusting the amount of current flowing to the light emitting means, wherein the LEDs in the light emitting means are arranged in such a net form that they are 5 connected in series in respective rows and in parallel in respective columns, the LEDs in a part of the rows having the same polarity and constituting a first LED group turned on for a positive (+) half period of the AC voltage supplied from the power supply means, the LEDs in the other part of the rows having the opposite polarity to that of the LEDs of the first LED group and constituting a second LED group turned on for a negative (-) half period of the AC voltage from the power supply means. The electric lamp circuit further comprises boosting means for boosting the AC voltage from the power supply means to a predetermined level when the light emitting means is not turned on because the AC voltage from the power supply means falls below a first reference value; and system control means for detecting the level of the AC voltage from the power supply means, discriminating the detected voltage level and adjusting a resistance of the variable resistor means or operating the boosting means in accordance with the discriminated result.

The variable resistor means includes a first switch operative under control of the system control means for connecting the power supply means to the light emitting means if the AC voltage from the power supply means is within the range between the first reference value and a second reference value, the second reference value being higher than the first reference value; a first resistor having a first resistance, the first resistor being adapted to, if the AC voltage from the power supply means is within the range between the second reference value and a third reference value, the third reference value being higher than the second reference value, connect the power supply means to the light emitting means to allow current within a predetermined range to flow to the light emitting means; a second resistor having a second resistance larger than the first resistance of the first resistor, the second resistor being adapted to connect the power supply means to the light emitting means if the AC voltage from the power supply means is above the third reference value; and a second switch operative under control of the system control means for selectively connecting the power supply means to the first resistor or the second resistor.

The system control means includes a voltage detector for detecting the level of the AC voltage from the power supply means; a level discriminator for discriminating the voltage level detected by the voltage detector; a third switch for selectively connecting the power supply means to the variable resistor means or the boosting means; and a driver operative in response to an output signal from the level discriminator for controlling the third switch to determine a current path and for, if the power supply means is connected to the variable resistor means by the third switch, controlling the variable resistor means to adjust the resistance thereof according to the level of the AC voltage from the power supply means. 5 In accordance with a second aspect of the present invention, there is provided an electric lamp circuit comprising light emitting means including a plurality of LEDs arranged in a matrix form of M rows x N columns; power supply means for supplying an AC voltage; bridge rectification means for full-wave rectifying the AC voltage from the 0 power supply means to supply a DC voltage to the light emitting means; and variable resistor means for forming a closed loop with the light emitting means and bridge rectification means and adjusting the amount of current flowing to the light emitting means, wherein the LEDs in the light emitting means have the same polarity and are arranged in such a net 5 form that they are connected in series in respective rows and in parallel in respective columns.

In accordance with a third aspect of the present invention, there is provided an electric lamp circuit comprising light emitting means including a plurality of LEDs having the same polarity and arranged in a o matrix form of M rows x N columns and in such a net form that they are connected in series in respective rows and in parallel in respective columns; power supply means for supplying an AC voltage; and bridge rectification means for full-wave rectifying the AC voltage from the power supply means, wherein the improvement comprises power means 5 for performing an analog control operation or a pulse width modulation operation with respect to an output voltage from the bridge rectification means to allow forward current to flow to the LEDs in the light emitting means; current detection means for detecting the amount of current flowing to the light emitting means; arithmetic means for obtaining the o average of the results detected by the current detection means; and control means for controlling the analog control operation or pulse width modulation operation of the power means in response to the current average obtained by the arithmetic means to adjust the amount of current flowing to the light emitting means. 5 The electric lamp circuit further comprises ambient brightness sensing means for sensing an ambient brightness of a lamp and outputting the resultant level signal to the control means to adjust a light intensity of the light emitting means according to the ambient brightness.

The electric lamp circuit further comprises circuit regeneration means including N Zener diodes having the opposite polarity to that of the LEDs in the light emitting means and connected in series to one another and in parallel respectively to the LEDs in the respective columns, each of the Zener diodes being adapted to, if all the LEDs of the corresponding column fail, create breakdown to transfer current to the LEDs of the subsequent column.

In accordance with a fourth aspect of the present invention, there is provided an electric lamp circuit comprising light emitting means including a plurality of LEDs arranged in a matrix form of M rows x N columns and in such a net form that they are connected in series in respective rows and in parallel in respective columns, the LEDs in a part of the rows having the same polarity and constituting a first LED group turned on for a positive (+) half period of an AC voltage, the LEDs in the other part of the rows having the opposite polarity to that of the LEDs of the first LED group and constituting a second LED group turned on for a negative (-) half period of the AC voltage; and power supply means for supplying the AC voltage to the light emitting means, wherein the improvement comprises power means for performing an analog control operation or a pulse width modulation operation with respect to the AC voltage from the power supply means to allow forward current to flow to the LEDs in the light emitting means; current detection means for detecting the amount of current flowing to the light emitting means; arithmetic means for obtaining the average of the results detected by the current detection means; and control means for controlling the analog control operation or pulse width modulation operation of the power means in response to the current average obtained by the arithmetic means to adjust the amount of current flowing to the light emitting means. The electric lamp circuit further comprises ambient brightness sensing means for sensing an ambient brightness of a lamp and outputting the resultant level signal to the control means to adjust a light intensity of the light emitting means according to the ambient brightness.

The electric lamp circuit further comprises circuit regeneration means including N pairs of Zener diodes with the opposite polarities, the

N Zener diode pairs being connected in series to one another and in parallel respectively to the LEDs in the respective columns, each of the N Zener diode pairs being adapted to, if all the LEDs of the corresponding column fail, create breakdown to transfer current to the LEDs of the subsequent column.

In accordance with a fifth aspect of the present invention, there is 5 provided an electric lamp structure comprising a base inserted into a socket to be connected to an external power source; a plurality of LEDs for emitting light; N+l connectors for mounting the LEDs on an LED board in a matrix form of M rows x N columns; and a lens disposed in the front of the LED board for widely dispersing the light emitted by the o LEDs, wherein each of the connectors includes an external case having

M pin holes formed thereon to receive lead terminals of the LEDs of each column, respectively; and a plurality of metal connection pins inserted respectively into the pin holes for interconnecting the lead terminals of the LEDs in the pin holes so as to arrange the LEDs in a net form. 5 In accordance with a sixth aspect of the present invention, there is provided an electric lamp structure comprising a base inserted into a socket to be connected to an external power source; a plurality of LEDs for emitting light; an LED board having a net-shaped pattern printed thereon; MxN connectors for mounting the LEDs on the pattern of the o LED board in a matrix form of M rows x N columns; and a lens disposed in the front of the LED board for widely dispersing the light emitted by the LEDs, wherein each of the connectors includes an external case having two pin holes formed thereon to receive lead terminals of each of the LEDs, respectively; and two metal connection pins inserted 5 respectively into the pin holes to individually support the lead terminals in the pin holes and connect them to the pattern of the LED board.

Brief Description of the Drawings

The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed 0 description taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a circuit diagram of a conventional electric lamp circuit which comprises a light emitting circuit consisting of a first LED group turned on for a positive (+) half period of an AC voltage and a second 5 LED group turned on for a negative (-) half period of the AC voltage; Fig. 2 is a circuit diagram of another conventional electric lamp circuit which comprises a bridge rectifier for supplying a DC voltage to a light emitting circuit;

Fig. 3 is a circuit diagram of yet another conventional electric lamp 5 circuit in which, even if any one of a plurality of lamps connected in series fails, the other lamps are normally turned on;

Figs. 4 and 5 are circuit diagrams of electric lamp circuits in accordance with first and second embodiments of the present invention, in whichA light emitting circuit includes LEDs connected in a net form; 0 Frg ) is a circuit diagram of an electric lamp circuit in accordance with a third embodiment of the present invention, in which a variation of an applied drive voltage is sensed and a resistance is adjusted on the basis of the sensed result to allow current within a predetermined range to flow to a light emitting circuit; 5 Figs. 7 and 8 are circuit diagrams of electric lamp circuits in accordance with fourth and fifth embodiments of the present invention, in which the amount of current flowing to a light emitting circuit is detected and an analog control operation or a pulse width modulation operation is performed on the basis of the detected result to allow current o within a predetermined range to flow to the light emitting circuit;

Fig. 9 is a sectional view of an electric lamp structure to which the present invention is applied;

Figs. 10A and 10B are exploded perspective views illustrating an embodiment of connectors in Fig. 9 in accordance with the present 5 invention; and

Figs. 11 A and 1 IB are exploded perspective views illustrating an alternative embodiment of the connectors in Fig. 9 in accordance with the present invention.

Best Modes for Carrying Out the Invention

o Fig. 4 is a circuit diagram of an electric lamp circuit in accordance with a first embodiment of the present invention.

With reference to Fig. 4, the electric lamp circuit comprises a light emitting circuit 41, power source 42 and variable resistor 43. The light emitting circuit 41 is provided with a plurality of LEDs D_n, D₁₂, ..., D,^ 5 arranged in a matrix form of M rows x N columns and in such a net form that they are connected in series in respective rows and in parallel in respective columns. The LEDs in a part of the rows have the same polarity and constitute a first LED group 41 A turned on for a positive (+) half period of an AC voltage supplied from the power source 42. The 5 LEDs in the other part of the rows have the opposite polarity to that of the LEDs of the first LED group 41 A and constitute a second LED group 4 IB turned on for a negative (-) half period of the AC voltage.

If a high voltage of AC is supplied from the power source 42, the variable resistor 43 is adjusted in resistance to allow a desired amount of l o current to flow to the light emitting circuit 41. As a result, the LEDs D, ,, D₁₂, ..., D_j^ are turned on to emit light. At this time, because the voltage from the power source 42 is of AC, the LEDs in the first LED group 41 A are turned on for a positive (+) half period of the AC voltage, and the LEDs in the second LED group 4 IB are turned on for a negative (-) half

15 period of the AC voltage.

In operation, if a specific LED fails, the other LEDs belonging to the same column are supplied with current through LEDs of the other columns connected in parallel thereto, so as to normally emit light. For example, if the LED D_n fails, current through the LEDs D₂₁ to D_κl flows

20 separately to the LEDs D₁₂ to D_K2, thereby allowing the LED D₁₂ to normally emit light.

Fig. 5 is a circuit diagram of an electric lamp circuit in accordance with a second embodiment of the present invention.

With reference to Fig. 5, the electric lamp circuit comprises a light 25 emitting circuit 51, power source 52, bridge rectifier 53 and variable resistor 54. The light emitting circuit 51 is provided with a plurality of LEDs D_n, D₁₂, ..., D_MN having the same polarity and arranged in a matrix form of M rows x N columns and in such a net form that they are connected in series in respective rows and in parallel in respective

3 o columns.

If a high voltage of AC is supplied from the power source 52, then it is full-wave rectified into a DC voltage by the bridge rectifier 53. The variable resistor 54 is then adjusted in resistance to allow a desired amount of current to flow to the light emitting circuit 51. As a result, all 35 the LEDs D_H, D₁₂, ..., D,^, in the light emitting circuit 51 are turned on to emit light.

In operation, if a specific LED fails, the other LEDs belonging to -l ithe same column are supplied with current through LEDs of the other columns connected in parallel thereto, so as to normally emit light. For example, if the LED D_n fails, current through the LEDs D₂₁ to D_M1 flows separately to the LEDs D₁₂ to D,^ thereby allowing the LED D _j normally emit light.

Fig. 6 is a circuit diagram of an electric lamp circuit in accordance with a third embodiment of the present invention.

With reference to Fig. 6, the reference numeral 61 denotes a light emitting circuit which is provided with a plurality of LEDs D_π, D₁₂, ..., D_j^ arranged in a matrix form of M rows x N columns and in such a net form that they are connected in series in respective rows and in parallel in respective columns. The reference numeral 62 denotes a power source which supplies an AC voltage of a desired frequency to the light emitting circuit 61. The reference numeral 63 denotes a variable resistor circuit which is adjustable in resistance to constantly maintain the amount of current flowing to the light emitting circuit 61 when the power source 62 is connected to the light emitting circuit 61 to turn the LEDs therein on.

The reference numeral 64 denotes a booster which boosts the AC voltage from the power source 62 to a predetermined level when the variable resistor circuit 63 cannot maintain, within a predetermined range, the amount of current flowing to the light emitting circuit 61 because the AC voltage from the power source 62 falls below a first reference value. The booster 64 then supplies the boosted voltage to the light emitting circuit 61 to avoid lighting failure thereof. The reference numeral 65 denotes a system controller which detects the level of the AC voltage from the power source 62, discriminates the detected voltage level and adjusts the resistance of the variable resistor circuit 63 or operates the booster 64 in accordance with the discriminated result.

The variable resistor circuit 63 includes a first resistor Rl having a first resistance and allowing current within a predetermined range to flow to the light emitting circuit 61 if the AC voltage from the power source 62 is within the range between second and third reference values. Here, the second reference value is higher than the first reference value, and the third reference value is higher than the second reference value. A first switch 63 A is connected in parallel to the first resistor Rl and operated under control of the system controller 65 to, if the AC voltage from the power source 62 is within the range between the first and second reference values, bypass the first resistor Rl to allow the current within the predetermined range to flow to the light emitting circuit 61. A second resistor R2 has a second resistance larger than the first resistance and allows the current within the predetermined range to flow to the light 5 emitting circuit 61 if the AC voltage from the power source 62 is above the third reference value. A second switch 63B is operated under control of the system controller 65 to selectively connect the power source 62 to the first resistor Rl or the second resistor R2. Preferably, the third reference value is a typical commercial voltage value which may be 110V 0 or 220V.

The system controller 65 includes a voltage detector 65A for detecting the level of the AC voltage from the power source 62, and a level discriminator 65B for discriminating the voltage level detected by the voltage detector 65A by comparing it with the first to third reference 5 values. A third switch 65C is operated to selectively connect the power source 62 to the variable resistor circuit 63 or the booster 64. A driver 65D is operated in response to an output signal from the level discriminator 65B to control the third switch 65C to determine a current path and to control the variable resistor circuit 63 to adjust the resistance o thereof.

If the system begins to be operated, the level of the AC voltage from the power source 62 is detected by the voltage detector 65A and then discriminated by the level discriminator 65B. At this time, the level discrimination is performed by comparing the voltage level detected by 5 the voltage detector 65 A with the first to third reference values.

If the AC voltage from the power source 62 falls below the first reference value, the driver 65D determines that the variable resistor circuit 63 cannot maintain, within the predetermined range, the amount of current flowing to the light emitting circuit 61. Thus, the driver 65D controls the o third switch 65C to connect the power source 62 to the booster 64 through a terminal P. Then, the booster 64 boosts the AC voltage from the power source 62 to the predetermined level and supplies the boosted voltage to the light emitting circuit 61 to avoid lighting failure thereof.

On the other hand, in the case where the AC voltage from the 5 power source 62 does not fall below the first reference value, the driver

65D controls the third switch 65C to connect the power source 62 to the variable resistor circuit 63 through a terminal Q. If the AC voltage from the power source 62 is above the third reference voltage, the driver 65D connects a terminal R of the second switch 63B to the power source 62 to, in turn, connect the power source 62 to the light emitting circuit 61 through the second resistor R2. If the AC voltage from the power source 62 is within the range between the second and third reference values, the driver 65D connects a terminal S of the second switch 63B to the power source 62 to, in turn, connect the power source 62 to the light emitting circuit 61 through the first resistor Rl. In the case where the AC voltage from the power source 62 is within the range between the first and second reference values, the driver 65D turns the first switch 63 A on to connect the power source 62 directly to the light emitting circuit 61.

In other words, in the variable resistor circuit 63, if the AC voltage from the power source 62 is within the range between the second and third reference values, the power source 62 is connected to the light emitting circuit 61 through the first resistor Rl so that the current within the predetermined range can flow to the light emitting circuit 61. If the AC voltage from the power source 62 is above the third reference value, current reduction is made by the second resistor R2 so that the current within the predetermined range can flow to the light emitting circuit 61. In the case where the AC voltage from the power source 62 is within the range between the first and second reference values, current increase is made by the first switch 63A so that the current within the predetermined range can flow to the light emitting circuit 61.

Therefore, a variation of the AC voltage from the power source 62 can be compensated in the above-mentioned manner, and so the amount of current flowing to the light emitting circuit 61 can be maintained constantly within the predetermined range.

Fig. 7 is a circuit diagram of an electric lamp circuit in accordance with a fourth embodiment of the present invention. With reference to Fig. 7, the electric lamp circuit comprises a light emitting circuit 71, power source 72, bridge rectifier 73, power device 74, current detector 75, arithmetic unit 76, controller 77, ambient brightness sensor 78 and circuit regenerator 79.

The light emitting circuit 71 is provided with a plurality of LEDs having the same polarity and arranged in a matrix form of M rows x N columns and in such a net form that they are connected in series in respective rows and in parallel in respective columns. The circuit regenerator 79 includes N Zener diodes having the opposite polarity to that of the LEDs in the light emitting circuit 71 and connected in series to one another and in parallel respectively to the LEDs in the respective columns. Each of the Zener diodes is adapted to, if all the LEDs of the corresponding column fail, create breakdown to transfer current to the LEDs of the subsequent column.

The power device 74 is adapted to perform an analog control operation or a pulse width modulation (PWM) operation with respect to an output voltage from the bridge rectifier 73 under control of the controller 77 to allow forward current to flow to the LEDs in the light emitting circuit 71 and adjust the amount of the flowing current. Preferably, the analog control operation may be an amplitude modulation operation.

An AC voltage from the power source 72 is full-wave rectified by the bridge rectifier 73 and then pulse width-modulated by the power device 74. As a result, forward current flows to the LEDs in the light emitting circuit 71 to turn them on. At this time, the current detector 75 detects the amount of current flowing to the light emitting circuit 71, and the arithmetic unit 76 continuously inputs the results detected by the current detector 75 for a predetermined period. The arithmetic unit 76 then obtains the average of the inputted results and outputs the obtained average to the controller 77.

In operation, the ambient brightness sensor 78 senses an ambient brightness of a lamp and outputs the resultant level signal to the controller 77.

The controller 77 then controls the power device 74 in response to the current average obtained by the arithmetic unit 76 and the ambient brightness level signal from the ambient brightness sensor 78 to adjust the amount of current flowing to the light emitting circuit 71 and, thus, a light intensity of the light emitting circuit 71.

Accordingly, if the surroundings are bright under the condition that the lamp is used as a traffic signal lamp, the amount of current flowing to the light emitting circuit 71 is increased to make the lamp readily distinguishable. To the contrary, in the case where the surroundings are dark, the amount of current flowing to the light emitting circuit 71 is reduced, resulting in a reduction in power consumption. On the other hand, in the case where the lamp is used as a street lamp, the operation is performed in the opposite manner to that mentioned above.

In operation, if a specific LED fails, overcurrent flows to LEDs belonging to a column corresponding thereto, thereby shortening the life span thereof. Subsequently, if all the LEDs of the corresponding column fail, breakdown occurs in one of the Zener diodes in the circuit regenerator 79 belonging to the corresponding column, thereby causing current to be transferred to the subsequent column to turn on the other LEDs.

Fig. 8 is a circuit diagram of an electric lamp circuit in accordance with a fifth embodiment of the present invention.

With reference to Fig. 8, the electric lamp circuit comprises a light emitting circuit 81, power source 82, power device 83, current detector 84, arithmetic unit 85, controller 86, ambient brightness sensor 87 and circuit regenerator 88. The light emitting circuit 81 is provided with a plurality of LEDs arranged in a matrix form of M rows x N columns and in such a net form that they are connected in series in respective rows and in parallel in respective columns. The LEDs in a part of the rows have the same polarity and constitute a first LED group turned on for a positive (+) half period of an AC voltage supplied from the power source 82, and the

LEDs in the other part of the rows have the opposite polarity to that of the LEDs of the first LED group and constitute a second LED group turned on for a negative (-) half period of the AC voltage. The circuit regenerator 88 includes N pairs of Zener diodes with the opposite polarities. The N Zener diode pairs are connected in series to one another and in parallel respectively to the LEDs in the respective columns. If all the LEDs of the corresponding column fail, each of the Zener diode pairs is adapted to create breakdown to transfer current to the LEDs of the subsequent column. If the AC voltage is supplied from the power source 82, the first and second LED groups with the opposite polarities are alternately turned on for the positive (+) and negative (-) half periods of the AC voltage.

In operation, if all the LEDs of a specific column fail, breakdown occurs in one of the Zener diode pairs in the circuit regenerator 88 belonging to the specific column, thereby causing current to be transferred to the subsequent column to turn on the other LEDs. As mentioned previously, the Zener diodes of each Zener diode pair have the opposite polarities. For this reason, reverse current is applied to one of the Zener diodes of the Zener diode pair belonging to the specific column to create breakdown, whereas forward current is applied to the other Zener diode to create no breakdown. Fig. 9 is a sectional view of an electric lamp structure to which the present invention is applied.

With reference to Fig. 9, the reference numeral 91 denotes a base which is inserted into a socket to be connected to an external power source. The reference numeral 92 denotes a plurality of LEDs which emit light. The reference numeral 93 denotes a plurality of connectors which interconnect the LEDs 92 in a matrix form. The reference numeral 94 denotes an LED board on which the connectors 93 are mounted or an integrated circuit is printed. The reference numeral 95 denotes a control circuit which controls turning-on/off of the LEDs 92. The reference numeral 96 denotes an LED support which supports the LED board 94. The reference numeral 97 denotes electric wires which are connected between the LED board 94 and the control circuit 95.

The reference numeral 98 denotes a lens which widely disperses the light emitted from the LEDs 92. The reference numeral 99 denotes a lens support which is mechanically coupled between and the base 91 and the lens 98 to support the lens 98.

Figs. 10A and 10B are exploded perspective views illustrating an embodiment of the connectors 93 in Fig. 9 in accordance with the present invention. With reference to Figs. 10A and 10B, the connectors 93 are adapted to interconnect the LEDs 92 in a matrix form. Preferably, N+l connectors are required to mount the LEDs 92 on the LED board 94 in a matrix form of M rows x N columns. M pin holes 93C are formed on each external case 93 A to receive lead terminals of the LEDs 92 of each column, respectively. Metal connection pins 93B are also inserted respectively into the pin holes 93 C to interconnect the lead terminals of the LEDs 92 in the pin holes 93C so as to arrange the LEDs in a net form. The metal connection pins 93B may also discharge heat generated from the LEDs 92 in operation. If a certain one of the LEDs 92 fails in operation, the user can pull out it from the corresponding pin holes 93 C of the corresponding connector 93 and replace it with a new one. In this manner, failure repairs can simply be made.

Figs. 11 A and 1 IB are exploded perspective views illustrating an alternative embodiment of the connectors in Fig. 9 in accordance with the present invention, which are designated by the reference numeral 93'. With reference to Figs. 11A and 1 IB, a net-shaped pattern 94' is printed on the LED board 94. Preferably, MxN connectors are required to mount the LEDs 92 on the pattern 94' of the LED board 94 in a matrix form of M rows x N columns. Two pin holes 93C are formed on each external case 93 A' to receive lead terminals of each LED 92, respectively, and have therebetween the same interval as that between the lead terminals. Two metal connection pins 93B' are also inserted respectively into the pin holes 93 C to individually support the lead terminals in the pin holes 93 C and connect them to the pattern 94' of the LED board 94.

Industrial Applicability

As apparent from the above description, according to the present invention, the LEDs in the light emitting circuit are arranged in a net form. Therefore, even though a specific one of the LEDs fails, the other LEDs of the same row can normally be turned on.

Further, because only the failed LED is turned off in the above- mentioned manner, it is readily distinguishable, resulting in a reduction in failure repair working time.

Further, a variation in the AC voltage from the power source is compensated so that the amount of current flowing to the light emitting circuit can be maintained within a predetermined range. Therefore, a lighting failure of the light emitting circuit can be avoided and overcurrent can be prevented from flowing to the light emitting circuit. These have the effect of extending the product's life span.

Further, the current detector and arithmetic unit are provided to detect an abrupt variation in the AC voltage from the power source and maintain the amount of current flowing to the light emitting circuit constantly within a predetermined range in accordance with the detected result, so as to protect the light emitting circuit from overcurrent. Moreover, the power device and ambient brightness sensor are provided to sense the ambient brightness of the lamp and adjust the light intensity of the light emitting circuit in accordance with the sensed result, thereby reducing power consumption.

Further, the circuit regenerator is provided to, even though all LEDs of a specific column fail, transfer current to LEDs of the subsequent column, thereby preventing operation incapability. 5 Finally, each LED can be mounted on the LED board by inserting its lead terminals into the pin holes of the connectors and replaced with a new one by detaching the lead terminals from the pin holes of the connectors. Therefore, if a certain one of the LEDs in the light emitting circuit fails, it can readily be repaired. l o Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. For example, the present invention

15 is not limited to a traffic signal lamp and can be applied to a variety of lamps including a plurality of LEDs, such as a street lamp, an advertising lamp, a lighting lamp, car's tail and direction indicating lamps and other LED signal lamps.

Claims

1. An electric lamp circuit comprising light emitting means including a plurality of LEDs arranged in a matrix form of M rows x N columns; power supply means for supplying an AC voltage to said light

5 emitting means; and variable resistor means for forming a closed loop with said light emitting means and power supply means and adjusting the amount of current flowing to said light emitting means, wherein said LEDs in said light emitting means are arranged in such a net form that they are connected in series in respective rows and in parallel in 0 respective columns, said LEDs in a part of said rows having the same polarity and constituting a first LED group turned on for a positive (+) half period of said AC voltage supplied from said power supply means, said LEDs in the other part of said rows having the opposite polarity to that of said LEDs of said first LED group and constituting a second LED 5 group turned on for a negative (-) half period of said AC voltage from said power supply means.

2. An electric lamp circuit as set forth in Claim 1, further comprising: boosting means for boosting said AC voltage from said power o supply means to a predetermined level when said light emitting means is not turned on because said AC voltage from said power supply means falls below a first reference value; and system control means for detecting the level of said AC voltage from said power supply means, discriminating the detected voltage level 5 and adjusting a resistance of said variable resistor means or operating said boosting means in accordance with the discriminated result.

3. An electric lamp circuit as set forth in Claim 1 or Claim 2, wherein said variable resistor means includes: a first switch operative under control of said system control means o for connecting said power supply means to said light emitting means if said AC voltage from said power supply means is within the range between said first reference value and a second reference value, said second reference value being higher than said first reference value; a first resistor having a first resistance, said first resistor being adapted to, if said AC voltage from said power supply means is within the range between said second reference value and a third reference value, said third reference value being higher than said second reference value, connect said power supply means to said light emitting means to allow current within a predetermined range to flow to said light emitting means; a second resistor having a second resistance larger than said first resistance of said first resistor, said second resistor being adapted to connect said power supply means to said light emitting means if said AC voltage from said power supply means is above said third reference value; and a second switch operative under control of said system control means for selectively connecting said power supply means to said first resistor or said second resistor.

4. An electric lamp circuit as set forth in Claim 2, wherein said system control means includes: a voltage detector for detecting the level of said AC voltage from said power supply means; a level discriminator for discriminating the voltage level detected by said voltage detector; a third switch for selectively connecting said power supply means to said variable resistor means or said boosting means; and a driver operative in response to an output signal from said level discriminator for controlling said third switch to determine a current path and for, if said power supply means is connected to said variable resistor means by said third switch, controlling said variable resistor means to adjust said resistance thereof according to the level of said AC voltage from said power supply means.

5. An electric lamp circuit comprising light emitting means including a plurality of LEDs arranged in a matrix form of M rows x N columns; power supply means for supplying an AC voltage; bridge rectification means for full-wave rectifying said AC voltage from said power supply means to supply a DC voltage to said light emitting means; and variable resistor means for forming a closed loop with said light emitting means and bridge rectification means and adjusting the amount of current flowing to said light emitting means, wherein said LEDs in said light emitting means have the same polarity and are arranged in such a net form that they are connected in series in respective rows and in parallel in respective columns.

6. An electric lamp circuit comprising light emitting means including a plurality of LEDs having the same polarity and arranged in a matrix form of M rows x N columns and in such a net form that they are connected in series in respective rows and in parallel in respective columns; power supply means for supplying an AC voltage; and bridge rectification means for full-wave rectifying said AC voltage from said power supply means, wherein the improvement comprises: power means for performing an analog control operation or a pulse width modulation operation with respect to an output voltage from said bridge rectification means to allow forward current to flow to said LEDs in said light emitting means; current detection means for detecting the amount of current flowing to said light emitting means; arithmetic means for obtaining the average of the results detected by said current detection means; and control means for controlling said analog control operation or pulse width modulation operation of said power means in response to the current average obtained by said arithmetic means to adjust the amount of current flowing to said light emitting means.

7. An electric lamp circuit as set forth in Claim 6, further comprising ambient brightness sensing means for sensing an ambient brightness of a lamp and outputting the resultant level signal to said control means to adjust a light intensity of said light emitting means according to the ambient brightness.

8. An electric lamp circuit as set forth in Claim 6, further comprising circuit regeneration means including N Zener diodes having the opposite polarity to that of said LEDs in said light emitting means and connected in series to one another and in parallel respectively to said LEDs in the respective columns, each of said Zener diodes being adapted to, if all said LEDs of the corresponding column fail, create breakdown to transfer current to said LEDs of the subsequent column.

9. An electric lamp circuit comprising light emitting means including a plurality of LEDs arranged in a matrix form of M rows x N columns and in such a net form that they are connected in series in respective rows and in parallel in respective columns, said LEDs in a part

5 of said rows having the same polarity and constituting a first LED group turned on for a positive (+) half period of an AC voltage, said LEDs in the other part of said rows having the opposite polarity to that of said LEDs of said first LED group and constituting a second LED group turned on for a negative (-) half period of said AC voltage; and power 0 supply means for supplying said AC voltage to said light emitting means, wherein the improvement comprises: power means for performing an analog control operation or a pulse width modulation operation with respect to said AC voltage from said power supply means to allow forward current to flow to said LEDs in said 5 light emitting means; current detection means for detecting the amount of current flowing to said light emitting means; arithmetic means for obtaining the average of the results detected by said current detection means; and o control means for controlling said analog control operation or pulse width modulation operation of said power means in response to the current average obtained by said arithmetic means to adjust the amount of current flowing to said light emitting means.

10. An electric lamp circuit as set forth in Claim 9, further 5 comprising ambient brightness sensing means for sensing an ambient brightness of a lamp and outputting the resultant level signal to said control means to adjust a light intensity of said light emitting means according to the ambient brightness.

11. An electric lamp circuit as set forth in Claim 9 or Claim 10, o further comprising circuit regeneration means including N pairs of Zener diodes with the opposite polarities, said N Zener diode pairs being connected in series to one another and in parallel respectively to said LEDs in the respective columns, each of said N Zener diode pairs being adapted to, if all said LEDs of the corresponding column fail, create 5 breakdown to transfer current to said LEDs of the subsequent column.

12. An electric lamp structure comprising a base inserted into a socket to be connected to an external power source; a plurality of LEDs for emitting light; N+l connectors for mounting said LEDs on an LED board in a matrix form of M rows x N columns; and a lens disposed in the

5 front of said LED board for widely dispersing the light emitted by said LEDs, wherein each of said connectors includes: an external case having M pin holes formed thereon to receive lead terminals of said LEDs of each column, respectively; and a plurality of metal connection pins inserted respectively into said o pin holes for interconnecting said lead terminals of said LEDs in said pin holes so as to arrange said LEDs in a net form.

13. An electric lamp structure comprising a base inserted into a socket to be connected to an external power source; a plurality of LEDs for emitting light; an LED board having a net-shaped pattern printed 5 thereon; MxN connectors for mounting said LEDs on said pattern of said LED board in a matrix form of M rows x N columns; and a lens disposed in the front of said LED board for widely dispersing the light emitted by said LEDs, wherein each of said connectors includes: an external case having two pin holes formed thereon to receive o lead terminals of each of said LEDs, respectively; and two metal connection pins inserted respectively into said pin holes to individually support said lead terminals in said pin holes and connect them to said pattern of said LED board.