EP0853445A1 - Controllable or dimmable electronic ballast provided with a lamp power measurement - Google Patents

Controllable or dimmable electronic ballast provided with a lamp power measurement Download PDF

Info

Publication number
EP0853445A1
EP0853445A1 EP97660148A EP97660148A EP0853445A1 EP 0853445 A1 EP0853445 A1 EP 0853445A1 EP 97660148 A EP97660148 A EP 97660148A EP 97660148 A EP97660148 A EP 97660148A EP 0853445 A1 EP0853445 A1 EP 0853445A1
Authority
EP
European Patent Office
Prior art keywords
lamp
power
current
filament
load 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.)
Withdrawn
Application number
EP97660148A
Other languages
German (de)
French (fr)
Inventor
Erkki Ahonen
Jari Heine
Hannu Vihinen
Teijo Viljanen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Helvar Oy AB
Original Assignee
Helvar Oy AB
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Helvar Oy AB filed Critical Helvar Oy AB
Publication of EP0853445A1 publication Critical patent/EP0853445A1/en
Withdrawn legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/36—Controlling
    • H05B41/38—Controlling the intensity of light
    • H05B41/39—Controlling the intensity of light continuously
    • H05B41/392—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor
    • H05B41/3921—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations
    • H05B41/3925—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations by frequency variation

Definitions

  • the present invention relates to a dimmable or controllable electronic ballast for a low-pressure discharge lamp, especially a fluorescent lamp, whose operation is based on regulating the light output of a lamp by varying the frequency of voltage supplied to the lamp.
  • the invention relates to a method and a circuit system for accurately measuring the power supplied by such a ballast to a lamp load so as to find out the proportional share of power consumed by the lamp cathodes.
  • the structure of electronic ballasts for low-pressure discharge lamps is prior known from the Applicant's patent No. 64478 as well as the theoretical foundations from the Applicant's patent No. FI 63314.
  • the Applicant's patent No. FI 63146 discloses the structure and operation of a low-voltage controlled electronic ballast for gaining a light output proportional to an external control signal.
  • the ballast shown in fig. 1 includes a rectifier V1 connected to a supply voltage UV, a smoothing capacitor C1, a high-frequency oscillator A1, as well as transistors TR1 and TR2 constituting a semi- or half-bridge circuit.
  • a lamp LL is connected as part of a resonance circuit, constituted by a capacitor C2 and a winding L2 and supplied by the push-pull transistors TR1 and TR2.
  • a filament pre-heating current for the cathodes of the lamp LL at a switch-on stage of the lamp is passed via a capacitor C3.
  • the oscillator Al is provided with a control connection CO1 - CO2, wherethrough the control signal influences the oscillating frequency of the oscillator.
  • the electronic ballast must generally be fitted with a separate safety feature for against certain special circumstances, such as over- or undervoltage in an electric network supplying the ballast, overheating of the device, a missing lamp, or breaking of the lamp cathodes, as described e.g. in the Applicant's patent application FI 955695.
  • heating the cathodes of low-pressure discharge lamps during the switch-on sequence of a lamp has a positive contribution to the service life and operating characteristics of the lamp.
  • the appropriately dimensioned filament power can be used for prolonging the service life of a lamp by reducing a stress applied to the lamp cathodes and especially to the emission material layer serving as a coating therefor. At the same time, this enables a lamp to be switched on without flicker with a voltage across the lamp that is lower than what is required when pre-heating is not used.
  • the requirements set on electronic ballasts regarding the heating of cathodes during the ignition of a lamp are set forth in the International standard IEC 929.
  • Fig. 2 of the drawings depicts one preferred embodiment for heating of the cathodes of a lamp LL.
  • a coil L2 includes two secondary windings for supplying the cathodes of the lamp LL with filament heating energy of a desired magnitude via capacitors C5 and C6.
  • Circuit elements R4 and V5 are used for a measuring purpose in a manner explained in more detail in connection with the description of the characterizing features of the invention.
  • the power delivered by the half-bridge connected transistor circuit TR1 and TR2 to the lamp load LL consists of two components: an actual lamp power, which sustains a light-generating discharge within the lamp, and a filament power, which is used for heating the lamp cathodes.
  • the power of cathode heating constitutes a substantial share of the power of the entire circuit.
  • a problem with the above-described ballast is the measurement of a load power in such a fashion that the actual lamp power can be measured at a sufficient accuracy without the power required by cathode heating having a significant effect on the measuring result.
  • An object of this invention is to introduce a measuring circuit connection for a ballast of the type defined in the preamble of claim 1, whereby the power of a low-pressure discharge lamp, especially a fluorescent lamp, can be measured such that the proportion of a power used for incandescence of the cathodes is compensated out of the measuring result.
  • the load circuit is constituted by a coil or winding L2, a lamp LL, and capacitors C2, C3.
  • the lamp LL is the only one of these to use effective power.
  • the energy spent by the lamp LL is divided into the use of energy caused by the lamp discharge and the energy consumed by filaments. In terms of light output, the energy of a lamp current is interesting.
  • the regulation functions well as long as the lamp power exceeds the filament power.
  • the regulation becomes inaccurate. Depending on the type of lamp, this occurs between about 10...20 % light level.
  • the effect of the filament power must be eliminated from the measuring signal. This can be effected e.g. by measuring a voltage existing across one of the cathodes of the lamp LL.
  • the cathode voltage is a product of the cathode resistance and the square sum of a filament current as well as a lamp current.
  • the filament current and the lamp current have a phase difference of about 90 degrees.
  • the filament voltage is constituted primarily by the filament current, as the lamp current is low.
  • a preferred compensating signal is obtained by simply subtracting an appropriately dimensioned voltage proportional to the filament voltage from a voltage proportional to the halfbridge supply current.
  • the compensation is dimensioned to be significant at lower light levels only.
  • the filament power can be calibrated, i.e. the effect of filament resistance fluctuations between various individual lamps can be compensated for prior to the ignition of a lamp by comparing the halfbridge current with the filament voltage.
  • a measurement from the end of a lamp yields both the filament and lamp current.
  • the dynamic impedance of a fluorescent lamp is almost resistive over a wide frequency range and the value of impedance is keenly dependent on the level of a lamp current such that, on low currents, the effective resistance is very high and, on high currents, it is respectively low.
  • Fig. 3 of the drawings illustrates one embodiment of the above-described measuring principle.
  • the total output of a load circuit is measured by using a resistance R2, which produces a voltage proportional to the current of a halfbridge TR1 - TR2, said voltage bing filtered by means of elements R3 and C4 and forwarded to an oscillator block A1.
  • the oscillator block A1 in terms of its function, is divided in two sections, whereby a sub-block II handles the processing of measuring signals and a sub-block I the control of the halfbridge transistors TR1 and TR2.
  • the voltage proportional to a power used for the heating of the cathodes of the lamp LL is developed by means of elements V4 and R1 and this measuring signal is likewise forwarded into the sub-block II of the oscillator circuit A1.
  • the difference between said measuring signals is obtained here, whereby the control block has at its disposal a real measuring signal proportional to the lamp power.
  • the control block II is able to conduct its control function in such a manner that control of the halfbridge TR1 - TR2 by way of the sub-block I guarantees a stable lighting regulation as designed for the ballast.
  • the voltage proportional to the filament power of the cathodes is obtained across a resistance R4 and the measuring signal is delivered to the control block by way of a diode V5.
  • the invention is not limited solely to the described embodiments but it equally well adaptable to numerous other frequency-regulation based ballast circuits, e.g. to multiple-lamp ballast versions.
  • the technology of switching transistors used in the halfbridge bears no significance on the usefulness of the described circuit, i.e. applicable in this context are a.o. a bipolar transistor and various versions of field effect transistors.
  • the control signal of the oscillator A1 in the circuit CO1 - CO2 can also be digital, in which case the sub-block II includes necessary circuit elements for processing digital information, e.g. by means of a programmable microcontroller.

Abstract

The invention relates to a controllable or dimmable electronic ballast provided with a lamp power measurement for a low-pressure discharge lamp, especially a fluorescent lamp. A halfbridge inverter (TR1, TR2; V2, V3) supplies high-frequency alternating current into a load circuit including a discharge lamp (LL). A regulation or control block (A1/I, II) controls light output of the lamp by regulating frequency of the inverter. Measurement information about a current proportional to the load circuit power is fed to the regulation or control block, which is also supplied with measurement information about a voltage proportional to a current passing through the filament of the lamp, the latter information being used for compensating the effect of filament power out of the measuring result of the load circuit power.

Description

The present invention relates to a dimmable or controllable electronic ballast for a low-pressure discharge lamp, especially a fluorescent lamp, whose operation is based on regulating the light output of a lamp by varying the frequency of voltage supplied to the lamp. The invention relates to a method and a circuit system for accurately measuring the power supplied by such a ballast to a lamp load so as to find out the proportional share of power consumed by the lamp cathodes.
The structure of electronic ballasts for low-pressure discharge lamps is prior known from the Applicant's patent No. 64478 as well as the theoretical foundations from the Applicant's patent No. FI 63314. On the other hand, the Applicant's patent No. FI 63146 discloses the structure and operation of a low-voltage controlled electronic ballast for gaining a light output proportional to an external control signal.
The structure and operation of a controllable or dimmable ballast prior known from the Applicant's patent No. FI63146 will be described in more detail with reference to fig. 1 of the attached drawings, depicting one preferred embodiment for such a ballast. In order to simplify the representation, fig. 1 only illustrates the structural components that are most essential in terms of understanding the operation.
The ballast shown in fig. 1 includes a rectifier V1 connected to a supply voltage UV, a smoothing capacitor C1, a high-frequency oscillator A1, as well as transistors TR1 and TR2 constituting a semi- or half-bridge circuit. A lamp LL is connected as part of a resonance circuit, constituted by a capacitor C2 and a winding L2 and supplied by the push-pull transistors TR1 and TR2. A filament pre-heating current for the cathodes of the lamp LL at a switch-on stage of the lamp is passed via a capacitor C3. The oscillator Al is provided with a control connection CO1 - CO2, wherethrough the control signal influences the oscillating frequency of the oscillator. The electronic ballast must generally be fitted with a separate safety feature for against certain special circumstances, such as over- or undervoltage in an electric network supplying the ballast, overheating of the device, a missing lamp, or breaking of the lamp cathodes, as described e.g. in the Applicant's patent application FI 955695.
It is general knowledge that heating the cathodes of low-pressure discharge lamps during the switch-on sequence of a lamp has a positive contribution to the service life and operating characteristics of the lamp. The appropriately dimensioned filament power can be used for prolonging the service life of a lamp by reducing a stress applied to the lamp cathodes and especially to the emission material layer serving as a coating therefor. At the same time, this enables a lamp to be switched on without flicker with a voltage across the lamp that is lower than what is required when pre-heating is not used. The requirements set on electronic ballasts regarding the heating of cathodes during the ignition of a lamp are set forth in the International standard IEC 929. The purpose of these requirements is to make sure that fluorescent lamps according to standards IEC 81 and IEC 901 reach the service life specified therefor. Deviation from the requirements of said standards may cause also other adverse effects, such as blackening of the glass bulb of a lamp in areas next to the cathodes, as material emitting from the cathodes accumulates on the internal surface of the glass bulb.
It is also prior known that said heating of the lamp cathodes is necessary whenever it is desirable to regulate the light output of the lamp. Sufficient cathode incandescence is used to make sure that a sufficient number of charge carriers are emitted from the cathodes to sustain discharge in a lamp as the current passing therethrough is diminishing. An optimal heating level is again necessary for maintaining the service life of a lamp at an acceptable level. Fig. 2 of the drawings depicts one preferred embodiment for heating of the cathodes of a lamp LL. In this circuit, a coil L2 includes two secondary windings for supplying the cathodes of the lamp LL with filament heating energy of a desired magnitude via capacitors C5 and C6. Circuit elements R4 and V5 are used for a measuring purpose in a manner explained in more detail in connection with the description of the characterizing features of the invention.
It is essential for the operation of an electronic ballast as described above that the power supplied to the lamp LL can be measured at a sufficient accuracy. This measuring information is utilized in the operation of a control block Al, such that the lamp LL can be supplied in a stable manner with a power proportional to a voltage between control lines CO1 and CO2 for regulating the light output of the lamp. The power delivered by the half-bridge connected transistor circuit TR1 and TR2 to the lamp load LL consists of two components: an actual lamp power, which sustains a light-generating discharge within the lamp, and a filament power, which is used for heating the lamp cathodes. Especially at lower regulation levels, whereby the power consumed by the discharge of a lamp is low, the power of cathode heating constitutes a substantial share of the power of the entire circuit. A problem with the above-described ballast is the measurement of a load power in such a fashion that the actual lamp power can be measured at a sufficient accuracy without the power required by cathode heating having a significant effect on the measuring result.
An object of this invention is to introduce a measuring circuit connection for a ballast of the type defined in the preamble of claim 1, whereby the power of a low-pressure discharge lamp, especially a fluorescent lamp, can be measured such that the proportion of a power used for incandescence of the cathodes is compensated out of the measuring result.
This object is achieved in the invention by means of the features set forth in the annexed claim 1. The non-independent claims disclose preferred embodiments of the invention.
In the drawings,
fig. 1
illustrates the prior art as described above;
fig. 2
shows one circuit configuration for the incandescence of a lamp cathode, said circuit being provided with elements R4, V5 for measuring the proportion of a power used for heating the cathodes; and
fig. 3
shows an electronic ballast, provided with a lamp power measurement of the invention and including a circuit configuration slightly different from that of fig. 2 for heating the cathodes and for measuring the proportion of a power used therefor.
The invention will be described in more detail in terms of its operation with reference made to fig. 3, most of the functions thereof having already been explained by means of fig. 1 of the drawings. An addition to this are so-called freewheel diodes V2 and V3, which allow the forward passage of the current of an oscillating circuit whenever a transistor TR1 or TR2 in parallel therewith has broken the circuit in the opposite direction of the current.
The effective energy consumed by a half-bridge TR1 - TR2 is primarily transferred into a load circuit C2, L2, LL, and C3. As a result of the symmetrical action of the circuit, the current through either one of the half-bridge supplies is proportional to the energy consumed by the load circuit, if the half-bridge supply voltage is maintained constant.
Pload ~ Ihalfbridge,supply
The load circuit is constituted by a coil or winding L2, a lamp LL, and capacitors C2, C3. The lamp LL is the only one of these to use effective power. The energy spent by the lamp LL is divided into the use of energy caused by the lamp discharge and the energy consumed by filaments. In terms of light output, the energy of a lamp current is interesting.
When the effective power of a load circuit or the light output produced by the lamp LL is regulated by using the halfbridge supply current as a reference value, the regulation functions well as long as the lamp power exceeds the filament power. When said powers are equal or the lamp power is lower than the filament power, the regulation becomes inaccurate. Depending on the type of lamp, this occurs between about 10...20 % light level. When it is desirable to adjust this to a lower light level, the effect of the filament power must be eliminated from the measuring signal. This can be effected e.g. by measuring a voltage existing across one of the cathodes of the lamp LL. The cathode voltage is a product of the cathode resistance and the square sum of a filament current as well as a lamp current. It should be noted that the filament current and the lamp current have a phase difference of about 90 degrees. At low light levels, the filament voltage is constituted primarily by the filament current, as the lamp current is low. Thus, a preferred compensating signal is obtained by simply subtracting an appropriately dimensioned voltage proportional to the filament voltage from a voltage proportional to the halfbridge supply current.
The compensation is dimensioned to be significant at lower light levels only. The filament power can be calibrated, i.e. the effect of filament resistance fluctuations between various individual lamps can be compensated for prior to the ignition of a lamp by comparing the halfbridge current with the filament voltage.
A measurement from the end of a lamp yields both the filament and lamp current. The dynamic impedance of a fluorescent lamp is almost resistive over a wide frequency range and the value of impedance is keenly dependent on the level of a lamp current such that, on low currents, the effective resistance is very high and, on high currents, it is respectively low.
Fig. 3 of the drawings illustrates one embodiment of the above-described measuring principle. In this case, the total output of a load circuit is measured by using a resistance R2, which produces a voltage proportional to the current of a halfbridge TR1 - TR2, said voltage bing filtered by means of elements R3 and C4 and forwarded to an oscillator block A1. Here, the oscillator block A1, in terms of its function, is divided in two sections, whereby a sub-block II handles the processing of measuring signals and a sub-block I the control of the halfbridge transistors TR1 and TR2.
The voltage proportional to a power used for the heating of the cathodes of the lamp LL is developed by means of elements V4 and R1 and this measuring signal is likewise forwarded into the sub-block II of the oscillator circuit A1. The difference between said measuring signals is obtained here, whereby the control block has at its disposal a real measuring signal proportional to the lamp power. By means of this and a control signal fed into the lines CO1 - CO2, the control block II is able to conduct its control function in such a manner that control of the halfbridge TR1 - TR2 by way of the sub-block I guarantees a stable lighting regulation as designed for the ballast.
When the pre-incandescence of cathodes is carried out by using a circuit as set forth in fig. 2, the voltage proportional to the filament power of the cathodes is obtained across a resistance R4 and the measuring signal is delivered to the control block by way of a diode V5.
It is evident for a skilled person that the invention is not limited solely to the described embodiments but it equally well adaptable to numerous other frequency-regulation based ballast circuits, e.g. to multiple-lamp ballast versions. Especially, the technology of switching transistors used in the halfbridge bears no significance on the usefulness of the described circuit, i.e. applicable in this context are a.o. a bipolar transistor and various versions of field effect transistors. It is also obvious that the control signal of the oscillator A1 in the circuit CO1 - CO2 can also be digital, in which case the sub-block II includes necessary circuit elements for processing digital information, e.g. by means of a programmable microcontroller.

Claims (3)

  1. A controllable or dimmable electronic ballast provided with a lamp power measurement for a low-pressure discharge lamp, especially for a fluorescent lamp, said ballast comprising
    at least one halfbridge inverter (TR1, TR2, V2, V3) or a corresponding AC-source, which supplies power to a load circuit,
    a load circuit, which includes a current limiting inductance (L2) and a filament current supplying capacitance (C3) as well as a discharge lamp (LL) connectable to the ballast,
    a regulation or control block (A1/I, II) for controlling the frequency of the inverter or a corresponding AC-source for regulating the light output of the lamp; and
    elements (R2, R3, C4) for measuring a current proportional to the load circuit power and for delivering measurement information (Umeas.) to the regulation or control block,
    characterized in that the device further includes elements (R1, V4; R4, V5) for measuring a voltage proportional to a current passing through one or more filaments of the lamp and for delivering measurement information to the regulation or control block (A1/I, II), wherein the measurement information is used for compensating the effect of filament power out of the measuring result of the load circuit power.
  2. A ballast as set forth in claim 1, characterized in that from a voltage proportional to the load circuit current is subtracted a voltage proportional to the filament current and the difference is used for controlling the regulation of the light output of a lamp.
  3. A ballast as set forth in claim 1 or 2, characterized in that said elements for measuring a voltage proportional to the filament current include a resistance (R1, R4) connected to the end of a filament, and the elements for delivering measurement information to the regulation or control block (A1/I, II) include a diode (V4, V5) connected to one of the poles of the measuring resistance (R1, R4).
EP97660148A 1997-01-03 1997-12-19 Controllable or dimmable electronic ballast provided with a lamp power measurement Withdrawn EP0853445A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI970017A FI101187B (en) 1997-01-03 1997-01-03 With the measurement of lamp power, an adjustable electronic connection device is provided
FI970017 1997-01-03

Publications (1)

Publication Number Publication Date
EP0853445A1 true EP0853445A1 (en) 1998-07-15

Family

ID=8547417

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97660148A Withdrawn EP0853445A1 (en) 1997-01-03 1997-12-19 Controllable or dimmable electronic ballast provided with a lamp power measurement

Country Status (2)

Country Link
EP (1) EP0853445A1 (en)
FI (1) FI101187B (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110761262B (en) * 2019-10-14 2020-09-11 浙江大学 Self-powered high-speed railway foundation monitoring system and monitoring method

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0422255A1 (en) * 1989-10-09 1991-04-17 Siemens Aktiengesellschaft Electronic ballast
EP0461441A1 (en) * 1990-06-06 1991-12-18 Zumtobel Aktiengesellschaft Process and circuit for varying the light intensity (dimming) of gas discharge lamps
US5424611A (en) * 1993-12-22 1995-06-13 At&T Corp. Method for pre-heating a gas-discharge lamp
EP0707438A2 (en) * 1994-10-13 1996-04-17 Tridonic Bauelemente GmbH Ballast for at least one discharge lamp
WO1997001945A1 (en) * 1995-06-29 1997-01-16 Philips Electronics N.V. Circuit arrangement
US5612595A (en) * 1995-09-13 1997-03-18 C-P-M Lighting, Inc. Electronic dimming ballast current sensing scheme

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0422255A1 (en) * 1989-10-09 1991-04-17 Siemens Aktiengesellschaft Electronic ballast
EP0461441A1 (en) * 1990-06-06 1991-12-18 Zumtobel Aktiengesellschaft Process and circuit for varying the light intensity (dimming) of gas discharge lamps
US5424611A (en) * 1993-12-22 1995-06-13 At&T Corp. Method for pre-heating a gas-discharge lamp
EP0707438A2 (en) * 1994-10-13 1996-04-17 Tridonic Bauelemente GmbH Ballast for at least one discharge lamp
WO1997001945A1 (en) * 1995-06-29 1997-01-16 Philips Electronics N.V. Circuit arrangement
US5612595A (en) * 1995-09-13 1997-03-18 C-P-M Lighting, Inc. Electronic dimming ballast current sensing scheme

Also Published As

Publication number Publication date
FI970017A0 (en) 1997-01-03
FI101187B1 (en) 1998-04-30
FI101187B (en) 1998-04-30

Similar Documents

Publication Publication Date Title
CA2032058C (en) Circuit for dimming gas discharge lamps without introducing striations
US5866993A (en) Three-way dimming ballast circuit with passive power factor correction
US6181083B1 (en) Ballast circuit with controlled strike/restart
US5925986A (en) Method and apparatus for controlling power delivered to a fluorescent lamp
WO1999045750A1 (en) Triac dimmable ballast
US4352045A (en) Energy conservation system using current control
WO1996010898A3 (en) Improvements in ballast circuit for fluorescent lamps
CN1110044A (en) Ballast circuit for a cathode-heated type of gas discharge lamp
JPH11509966A (en) Dimmable ballast
US20070138967A1 (en) Dimming ballast and method
US5581161A (en) DC coupled electronic ballast with a larger DC and smaller AC signal
EP0852453B1 (en) Electronic ballast for a discharge lamp, provided with a lamp power measurement by means of a DC-signal
EP1057378B1 (en) Drive scheme for low pressure gas discharge lamps
EP0853445A1 (en) Controllable or dimmable electronic ballast provided with a lamp power measurement
EP0948244A2 (en) A self ballasted fluorescent lamp and lighting fixture
US6242869B1 (en) Fluorescent lamp stabilizer harmonics reduction method
KR100291689B1 (en) Low Loss Electronic Ballast Resistor Circuit for Discharge Lamps
EP0848581A1 (en) Cathode filament heating circuit for a low-pressure discharge lamp
KR100283312B1 (en) Fluorescent Flasher
US6100646A (en) Ballast feedback scheme
EP0929995A1 (en) Ballast
KR200241268Y1 (en) Electronic Fluorescent Ballast with Preheating Light Circuit
CA2347470A1 (en) Ballast circuit
RU2007128966A (en) METHOD FOR CONTROLING A CATHODE VOLTAGE OF A DISCHARGE LAMP WITH A LOW DISCHARGE CURRENT
JPS6149399A (en) Device for firing fluorescent lamp

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): DE FR GB IT NL

AX Request for extension of the european patent

Free format text: AL;LT;LV;MK;RO;SI

17P Request for examination filed

Effective date: 19990115

AKX Designation fees paid

Free format text: DE FR GB IT NL

RBV Designated contracting states (corrected)

Designated state(s): DE FR GB IT NL

17Q First examination report despatched

Effective date: 19990223

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION HAS BEEN WITHDRAWN

18W Application withdrawn

Withdrawal date: 19990527