EP0602719B1 - High frequency inverter for a discharge lamp with preheatable electrodes - Google Patents

High frequency inverter for a discharge lamp with preheatable electrodes Download PDF

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Publication number
EP0602719B1
EP0602719B1 EP19930203448 EP93203448A EP0602719B1 EP 0602719 B1 EP0602719 B1 EP 0602719B1 EP 19930203448 EP19930203448 EP 19930203448 EP 93203448 A EP93203448 A EP 93203448A EP 0602719 B1 EP0602719 B1 EP 0602719B1
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EP
European Patent Office
Prior art keywords
frequency
discharge lamp
load branch
branch
electrode
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 - Lifetime
Application number
EP19930203448
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German (de)
French (fr)
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EP0602719A1 (en
Inventor
Frans Slegers
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.)
Koninklijke Philips NV
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Koninklijke Philips Electronics NV
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Priority to EP19930203448 priority Critical patent/EP0602719B1/en
Publication of EP0602719A1 publication Critical patent/EP0602719A1/en
Application granted granted Critical
Publication of EP0602719B1 publication Critical patent/EP0602719B1/en
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    • 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
    • H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
    • H05B41/28—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
    • H05B41/295—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices and specially adapted for lamps with preheating electrodes, e.g. for fluorescent lamps
    • 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 invention relates to a circuit arrangement for high-frequency operation of a discharge lamp, comprising
  • Such a circuit arrangement is known from European Patent EP-A-0 098 285 and American Patent US-A-4 682 020.
  • the luminous flux of a discharge lamp operated by means of one of these known circuit arrangements may be adjusted in that the frequency of the control signal is adjusted.
  • a change in the frequency of the control signal leads to a change in the frequency of the high-frequency current through the load branch, so that the impedance of the load branch and the amplitude of the high-frequency current are also changed.
  • a change in the luminous flux of the discharge lamp may thus be achieved through a change in the frequency of the control signal.
  • the electrodes of the discharge lamp are heated during lamp operation both by the high-frequency current flowing through the lamp and by an electrode heating current of the same frequency which flows through the electrodes of the discharge lamp as a result of a potential difference between the ends of the secondary windings of the electrode heating transformer during lamp operation. It is ensured through dimensioning of the known circuit arrangement that the temperature of the lamp electrodes is maintained at a suitable value during a lamp operation in which the discharge lamp achieves the highest adjustable luminous flux as a result of the discharge current and the electrode heating current. Lamp electrode life is comparatively long at this suitable value of the electrode temperature.
  • the invention has for its object inter alia to provide a circuit arrangement by which it is possible to dim a discharge lamp operated by means of the circuit arrangement without the life of the discharge lamp being adversely affected by this.
  • a circuit arrangement of the kind mentioned in the opening paragraph is for this pulse characterized in that each branch shunting a secondary winding of the transformer comprises inductive means and capacitive means and has a resonance frequency which is different from the resonance frequency of the load branch.
  • the resonance frequencies of all branches shunting a secondary winding of the transformer are chosen to be either all lower than the resonance frequency of the load branch or all higher than the resonance frequency of the load branch. It is achieved by this that, at operating frequencies between the resonance frequency of the load branch and the resonance frequency of each branch shunting the ends of a secondary winding, a change in the operating frequency results either in an increase in the discharge current and an accompanying decrease in the electrode heating current, or in a decrease in the discharge current and an accompanying increase in the electrode heating current.
  • the luminous flux of the discharge lamp may be adjusted over a wide range, each luminous flux value of the discharge lamp having an accompanying electrode temperature of the discharge lamp of such a value that the electrode life is comparatively long, while in addition blackening of the lamp vessel ends hardly takes place.
  • An advantageous embodiment of a circuit arrangement according to the invention is characterized in that the load branch comprises an inductive element, in that the resonance frequency of the load branch has a lower value than the resonance frequencies of the branches shunting the secondary windings, and in that the frequency of the high-frequency current through the load branch is higher for each luminous flux value of the lamp which can be set than the resonance frequency of the load branch and lower than the resonance frequencies of the branches shunting the secondary windings of the electrode heating transformer. Since the frequency of the high-frequency current through the load branch is higher than the resonance frequency of the load branch, the load branch acts as an inductive impedance.
  • this is an important advantage because the life of the switching elements in the circuit arrangement is comparatively long when the load branch is an inductive impedance.
  • it is profitable to integrate the inductive element and the electrode heating transformer, so that one component performs different functions in the circuit arrangement. Owing to the comparatively small number of components, the circuit is of a comparatively simple construction, and thus more readily manufactured on a large scale.
  • reference numerals 1 and 2 denote input terminals for connection to a supply voltage source. It is desirable for the circuit arrangement shown in Fig. 1 that the supply voltage source should be a DC voltage source whose anode is connected to terminal 1 and whose cathode is connected to terminal 2.
  • Input terminals 1 and 2 are interconnected by a series circuit of two switching elements S1 and S2. Control electrodes of the switching elements are connected to respective outputs of control circuit I for generating a control signal which is to render the switching elements S1 and S2 alternately conducting and non-conducting with high frequency.
  • An input of control circuit I is connected to an output of dimmer circuit II which adjusts the frequency of the control signal.
  • the load branch in this embodiment is formed by capacitors C1, C2, C3 and C4, transformer L3, coils L1 and L2, terminals H1 and H2 for accommodating a discharge lamp, and the discharge lamp La.
  • the transformer L3 in this embodiment performs the function of electrode heating transformer as well as the function of inductive element.
  • a common junction point of the switching elements S1 and S2 is connected to a first side of capacitor C1.
  • a further side of capacitor C1 is connected to a first end of primary winding P of transformer L3.
  • a further end of primary winding P is connected to a first side of capacitor C4.
  • a further side of capacitor C4 is connected to input terminal 2.
  • the further end of primary winding P is also connected to a first end of electrode E11 of discharge lamp La.
  • Electrode E11 is shunted by a series circuit of coil L1, capacitor C1, and secondary winding Sec1 of transformer L3.
  • a first end of electrode E12 of the discharge lamp La is connected to input terminal 2.
  • Electrode E12 is shunted by a series circuit of coil L2, capacitor C2, and secondary winding Sec2.
  • the control circuit I When the input terminals 1 and 2 are connected to the anode and cathode, respectively, of a DC voltage source, the control circuit I renders the switching elements S1 and S2 conducting and non-conducting with a high frequency f. As a result, a high-frequency current with frequency f flows through the load branch. A high-frequency current with frequency f also flows through the two branches which shunt the secondary windings Sec1 and Sec2 of the transformer L3.
  • the lowest adjustable frequency of the control signal has been set by means of the dimmer circuit II, the discharge lamp La dissipates approximately its rated power and the luminous flux of the discharge lamp La has the maximum value which can be set.
  • the load branch is so dimensioned that the frequency f has a higher value than the resonance frequency of the load branch, so that the load branch is an inductive impedance at the frequency f.
  • the branches shunting the secondary windings Sec1 and Sec2 of transformer L3 are so dimensioned that the resonance frequencies of these branches are higher than the frequency f.
  • the impedances of these branches as a result are capacitive.
  • the electrode heating current is plotted on the vertical axis in mA.
  • the discharge current is plotted on the horizontal axis in mA.
  • the discharge lamp for which the relation between discharge current and electrode heating current as shown in Fig. 2 was measured was a low-pressure mercury discharge lamp of the PL-L type, make Philips, with a power rating of 55 W.
  • the curve K1 shows the measured relation between the discharge current and the electrode heating current. Points A and B on the curve K1 mark the limits of the adjustment range of the discharge current: 50 mA and 600 mA, respectively.
  • Curves K1 and K3 give the empirically determined maximum and minimum values, respectively, of the electrode heating current for each value of the discharge current, at which the electrode life of the discharge lamp is comparatively long.
  • Fig. 2 shows that the electrode heating current lies between the minimum and the maximum value throughout the entire adjustment range of the discharge current.

Landscapes

  • Circuit Arrangements For Discharge Lamps (AREA)

Description

The invention relates to a circuit arrangement for high-frequency operation of a discharge lamp, comprising
  • input terminals for connection to a supply voltage source,
  • a load branch provided with terminals for accommodating the discharge lamp and with an electrode heating transformer provided with a primary winding and secondary windings, each secondary winding being shunted by a branch comprising an electrode of the discharge lamp,
  • at least one switching element for generating a high-frequency current through the load branch from a supply voltage delivered by the supply voltage source,
  • a control circuit for generating a control signal for rendering the switching element conducting and non-conducting with high frequency,
  • a dimmer circuit coupled to the control circuit for adjusting the frequency of the control signal.
Such a circuit arrangement is known from European Patent EP-A-0 098 285 and American Patent US-A-4 682 020. The luminous flux of a discharge lamp operated by means of one of these known circuit arrangements may be adjusted in that the frequency of the control signal is adjusted. A change in the frequency of the control signal leads to a change in the frequency of the high-frequency current through the load branch, so that the impedance of the load branch and the amplitude of the high-frequency current are also changed. A change in the luminous flux of the discharge lamp may thus be achieved through a change in the frequency of the control signal. In the known circuit arrangement, the electrodes of the discharge lamp are heated during lamp operation both by the high-frequency current flowing through the lamp and by an electrode heating current of the same frequency which flows through the electrodes of the discharge lamp as a result of a potential difference between the ends of the secondary windings of the electrode heating transformer during lamp operation. It is ensured through dimensioning of the known circuit arrangement that the temperature of the lamp electrodes is maintained at a suitable value during a lamp operation in which the discharge lamp achieves the highest adjustable luminous flux as a result of the discharge current and the electrode heating current. Lamp electrode life is comparatively long at this suitable value of the electrode temperature. When the luminous flux of the discharge lamp is reduced by a user by means of the dimmer circuit, however, not only the discharge current through the discharge lamp but also the electrode heating current through the electrodes decreases. The temperature of the electrode as a result drops further below the suitable value in proportion as the luminous flux of the discharge lamp is reduced further. As a result, lamp electrode life is shortened to a comparatively high degree by dimming of the discharge lamp, while at the same time blackening of the ends of the lamp vessel of the discharge lamp takes place.
The invention has for its object inter alia to provide a circuit arrangement by which it is possible to dim a discharge lamp operated by means of the circuit arrangement without the life of the discharge lamp being adversely affected by this.
According to the invention, a circuit arrangement of the kind mentioned in the opening paragraph is for this pulse characterized in that each branch shunting a secondary winding of the transformer comprises inductive means and capacitive means and has a resonance frequency which is different from the resonance frequency of the load branch.
The resonance frequencies of all branches shunting a secondary winding of the transformer are chosen to be either all lower than the resonance frequency of the load branch or all higher than the resonance frequency of the load branch. It is achieved by this that, at operating frequencies between the resonance frequency of the load branch and the resonance frequency of each branch shunting the ends of a secondary winding, a change in the operating frequency results either in an increase in the discharge current and an accompanying decrease in the electrode heating current, or in a decrease in the discharge current and an accompanying increase in the electrode heating current. This means that, provided the circuit arrangement is suitably dimensioned, the luminous flux of the discharge lamp may be adjusted over a wide range, each luminous flux value of the discharge lamp having an accompanying electrode temperature of the discharge lamp of such a value that the electrode life is comparatively long, while in addition blackening of the lamp vessel ends hardly takes place.
An advantageous embodiment of a circuit arrangement according to the invention is characterized in that the load branch comprises an inductive element, in that the resonance frequency of the load branch has a lower value than the resonance frequencies of the branches shunting the secondary windings, and in that the frequency of the high-frequency current through the load branch is higher for each luminous flux value of the lamp which can be set than the resonance frequency of the load branch and lower than the resonance frequencies of the branches shunting the secondary windings of the electrode heating transformer. Since the frequency of the high-frequency current through the load branch is higher than the resonance frequency of the load branch, the load branch acts as an inductive impedance. Depending on the design of the circuit arrangement, this is an important advantage because the life of the switching elements in the circuit arrangement is comparatively long when the load branch is an inductive impedance. In this advantageous embodiment of a circuit arrangement according to the invention, it is profitable to integrate the inductive element and the electrode heating transformer, so that one component performs different functions in the circuit arrangement. Owing to the comparatively small number of components, the circuit is of a comparatively simple construction, and thus more readily manufactured on a large scale.
An embodiment of the invention will be explained with reference to a drawing.
  • In the drawing, Fig. 1 shows an embodiment of a circuit arrangement according to the invention, and
  • Fig. 2 shows an electrode heating current as a function of a discharge current through a lamp operated by means of a circuit arrangement as shown in Fig. 1.
    • In Fig. 1, reference numerals 1 and 2 denote input terminals for connection to a supply voltage source. It is desirable for the circuit arrangement shown in Fig. 1 that the supply voltage source should be a DC voltage source whose anode is connected to terminal 1 and whose cathode is connected to terminal 2. Input terminals 1 and 2 are interconnected by a series circuit of two switching elements S1 and S2. Control electrodes of the switching elements are connected to respective outputs of control circuit I for generating a control signal which is to render the switching elements S1 and S2 alternately conducting and non-conducting with high frequency. An input of control circuit I is connected to an output of dimmer circuit II which adjusts the frequency of the control signal. The load branch in this embodiment is formed by capacitors C1, C2, C3 and C4, transformer L3, coils L1 and L2, terminals H1 and H2 for accommodating a discharge lamp, and the discharge lamp La. The transformer L3 in this embodiment performs the function of electrode heating transformer as well as the function of inductive element. A common junction point of the switching elements S1 and S2 is connected to a first side of capacitor C1. A further side of capacitor C1 is connected to a first end of primary winding P of transformer L3. A further end of primary winding P is connected to a first side of capacitor C4. A further side of capacitor C4 is connected to input terminal 2. The further end of primary winding P is also connected to a first end of electrode E11 of discharge lamp La. Electrode E11 is shunted by a series circuit of coil L1, capacitor C1, and secondary winding Sec1 of transformer L3. A first end of electrode E12 of the discharge lamp La is connected to input terminal 2. Electrode E12 is shunted by a series circuit of coil L2, capacitor C2, and secondary winding Sec2.
    The operation of the circuit arrangement shown in Fig. 1 is as follows.
    When the input terminals 1 and 2 are connected to the anode and cathode, respectively, of a DC voltage source, the control circuit I renders the switching elements S1 and S2 conducting and non-conducting with a high frequency f. As a result, a high-frequency current with frequency f flows through the load branch. A high-frequency current with frequency f also flows through the two branches which shunt the secondary windings Sec1 and Sec2 of the transformer L3. When the lowest adjustable frequency of the control signal has been set by means of the dimmer circuit II, the discharge lamp La dissipates approximately its rated power and the luminous flux of the discharge lamp La has the maximum value which can be set. The load branch is so dimensioned that the frequency f has a higher value than the resonance frequency of the load branch, so that the load branch is an inductive impedance at the frequency f. In addition, the branches shunting the secondary windings Sec1 and Sec2 of transformer L3 are so dimensioned that the resonance frequencies of these branches are higher than the frequency f. The impedances of these branches as a result are capacitive. Now when the frequency of the control signal, and thus the frequency f of the high-frequency current in the load branch, is increased through the dimmer circuit II, the impedance of the load branch increases. As a result, the current through the load branch decreases, and accordingly also the current through the discharge lamp La. An increase in the frequency f, however, also leads to a decrease in the impedance of the branches shunting the two secondary windings Sec1 and Sec2. The electrode heating currents flowing through these two branches are increased as a result. Conversely, the currents through the branches shunting the secondary windings Sec1 and Sec2 of the transformer L3 decrease when the discharge current is increased. Thus an increase in the electrode heating current is achieved at a decrease in the discharge current through the lamp such that the temperatures of the electrodes E11 and E12 of the discharge lamp have such a value at every adjustable luminous flux of the discharge lamp that the electrode life is comparatively long and that substantially no blackening occurs at the ends of the discharge vessel.
    In Fig. 2, the electrode heating current is plotted on the vertical axis in mA. The discharge current is plotted on the horizontal axis in mA. The discharge lamp for which the relation between discharge current and electrode heating current as shown in Fig. 2 was measured, was a low-pressure mercury discharge lamp of the PL-L type, make Philips, with a power rating of 55 W. The curve K1 shows the measured relation between the discharge current and the electrode heating current. Points A and B on the curve K1 mark the limits of the adjustment range of the discharge current: 50 mA and 600 mA, respectively. Curves K1 and K3 give the empirically determined maximum and minimum values, respectively, of the electrode heating current for each value of the discharge current, at which the electrode life of the discharge lamp is comparatively long. Fig. 2 shows that the electrode heating current lies between the minimum and the maximum value throughout the entire adjustment range of the discharge current.

    Claims (3)

    1. A circuit arrangement for high-frequency operation of a discharge lamp (LA), comprising
      input terminals (1,2) for connection to a supply voltage source,
      a load branch provided with terminals (H1, H2) for accommodating the discharge lamp (LA) and with an electrode heating transformer (L3) provided with a primary winding (P) and secondary windings (Sec1, Sec2), each secondary winding being shunted by a branch comprising an electrode (EL1, EL2) of the discharge lamp (LA),
      at least one switching element (S1,S2) for generating a high-frequency current through the load branch from a supply voltage delivered by the supply voltage source,
      a control circuit (I) for generating a control signal for rendering the switching element (S1, S2) conducting and non-conducting with high frequency,
      a dimmer circuit (H) coupled to the control circuit for adjusting the frequency of the control signal,
      characterized in that each branch shunting a secondary winding of the transformer (Sec1, Sec2) comprises inductive means (L1, L2) and capacitive means (C1, C2) and has a resonance frequency which is different from the resonance frequency of the load branch.
    2. A circuit arrangement as claimed in Claim 1, characterized in that the load branch comprises an inductive element, in that the resonance frequency of the load branch has a lower value than the resonance frequencies of the branches shunting the secondary windings, and in that the frequency of the high-frequency current through the load branch is higher for each luminous flux value of the lamp which can be set than the resonance frequency of the load branch and lower than the resonance frequencies of the branches shunting the secondary windings of the electrode heating transformer.
    3. A circuit arrangement as claimed in Claim 2, characterized in that the inductive element and the electrode heating transformer are integrated in one component.
    EP19930203448 1992-12-16 1993-12-09 High frequency inverter for a discharge lamp with preheatable electrodes Expired - Lifetime EP0602719B1 (en)

    Priority Applications (1)

    Application Number Priority Date Filing Date Title
    EP19930203448 EP0602719B1 (en) 1992-12-16 1993-12-09 High frequency inverter for a discharge lamp with preheatable electrodes

    Applications Claiming Priority (3)

    Application Number Priority Date Filing Date Title
    EP92203942 1992-12-16
    EP92203942 1992-12-16
    EP19930203448 EP0602719B1 (en) 1992-12-16 1993-12-09 High frequency inverter for a discharge lamp with preheatable electrodes

    Publications (2)

    Publication Number Publication Date
    EP0602719A1 EP0602719A1 (en) 1994-06-22
    EP0602719B1 true EP0602719B1 (en) 1998-10-21

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    Application Number Title Priority Date Filing Date
    EP19930203448 Expired - Lifetime EP0602719B1 (en) 1992-12-16 1993-12-09 High frequency inverter for a discharge lamp with preheatable electrodes

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    Families Citing this family (13)

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    Publication number Priority date Publication date Assignee Title
    DE19501695B4 (en) * 1994-10-13 2008-10-02 Tridonicatco Gmbh & Co. Kg Ballast for at least one gas discharge lamp with preheatable lamp filaments
    DE19520999A1 (en) * 1995-06-08 1996-12-12 Siemens Ag Circuit arrangement for filament preheating of fluorescent lamps
    BE1009717A3 (en) * 1995-10-20 1997-07-01 Philips Electronics Nv Shifting.
    DE19634850A1 (en) * 1996-08-28 1998-03-05 Tridonic Bauelemente Electronic ballast for gas discharge lamps
    EP0848581A1 (en) * 1996-12-12 1998-06-17 Oy Helvar Cathode filament heating circuit for a low-pressure discharge lamp
    US5973455A (en) * 1998-05-15 1999-10-26 Energy Savings, Inc. Electronic ballast with filament cut-out
    DE19923083A1 (en) * 1999-05-20 2001-01-04 Hueco Electronic Gmbh Adapter for low pressure discharge lamps has bridge circuit outputs connected to primary coil winding and to first secondary coil, second output or negative pole to second secondary coil
    WO2002032195A2 (en) * 2000-10-12 2002-04-18 Photoscience Japan Corporation Discharge lamps preheating
    DE10053803A1 (en) * 2000-10-30 2002-05-08 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Lighting system with gentle preheating of gas discharge lamps
    DE20114623U1 (en) * 2001-09-04 2004-02-12 Wilken, Wilhelm, Dr. Distal adapter for T5 fluorescent lamps with retrofit ECG
    DE10304544B4 (en) * 2003-02-04 2006-10-12 Hep Tech Co.Ltd. Electronic ballast
    US8115421B2 (en) * 2007-02-19 2012-02-14 Panasonic Electronic Works Co., Ltd. Discharge lamp lighting device, illumination device, and liquid crystal display device
    AT11177U1 (en) * 2008-12-19 2010-05-15 Tridonicatco Gmbh & Co Kg HEATING CIRCUIT FOR AN OPERATING DEVICE FOR GAS DISCHARGE LAMPS

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    DE3140175A1 (en) * 1981-10-08 1983-04-28 Licentia Gmbh Transistor ballast apparatus
    US4682080A (en) * 1984-08-17 1987-07-21 Hitachi, Ltd. Discharge lamp operating device
    US4686427A (en) * 1985-08-13 1987-08-11 Magnetek, Inc. Fluorescent lamp dimming switch
    DE4218959A1 (en) * 1991-07-11 1993-01-14 Bosch Gmbh Robert CIRCUIT ARRANGEMENT FOR OPERATING A FLUORESCENT LAMP

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    Publication number Publication date
    EP0602719A1 (en) 1994-06-22

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