EP0399835B1 - Stromversorgungsschaltungen für Entladungslampen - Google Patents

Stromversorgungsschaltungen für Entladungslampen Download PDF

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Publication number
EP0399835B1
EP0399835B1 EP90305695A EP90305695A EP0399835B1 EP 0399835 B1 EP0399835 B1 EP 0399835B1 EP 90305695 A EP90305695 A EP 90305695A EP 90305695 A EP90305695 A EP 90305695A EP 0399835 B1 EP0399835 B1 EP 0399835B1
Authority
EP
European Patent Office
Prior art keywords
lamp
supply
supply circuit
circuit according
flicker
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
EP90305695A
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English (en)
French (fr)
Other versions
EP0399835A1 (de
Inventor
Ian Macdonald Green
Everard Joseph Mascarenhas
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.)
TLG PLC
Original Assignee
TLG PLC
Thorn EMI PLC
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
Priority claimed from GB898912129A external-priority patent/GB8912129D0/en
Application filed by TLG PLC, Thorn EMI PLC filed Critical TLG PLC
Publication of EP0399835A1 publication Critical patent/EP0399835A1/de
Application granted granted Critical
Publication of EP0399835B1 publication Critical patent/EP0399835B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • H05B41/16—Circuit arrangements in which the lamp is fed by dc or by low-frequency ac, e.g. by 50 cycles/sec ac, or with network frequencies
    • H05B41/20—Circuit arrangements in which the lamp is fed by dc or by low-frequency ac, e.g. by 50 cycles/sec ac, or with network frequencies having no starting switch
    • H05B41/23—Circuit arrangements in which the lamp is fed by dc or by low-frequency ac, e.g. by 50 cycles/sec ac, or with network frequencies having no starting switch for lamps not having an auxiliary starting electrode
    • H05B41/231—Circuit arrangements in which the lamp is fed by dc or by low-frequency ac, e.g. by 50 cycles/sec ac, or with network frequencies having no starting switch for lamps not having an auxiliary starting electrode for high-pressure lamps

Definitions

  • This invention relates to a supply circuit for powering a discharge lamp from an a.c. supply, the circuit including an inductive ballast and an impedance for serial connection with the lamp.
  • One known method of alleviating the problem of flicker is to drive the lamp from a high frequency voltage derived from the A.C. supply via appropriate circuitry, for example power FETs. While such an arrangement has the advantage of considerable reduction in flicker together with increased efficiency the circuitry required is, at present, relatively expensive. Furthermore there are problems in controlling the high voltages needed to start the lamp and subsequently drive it using such high frequency voltages.
  • DE-A-2417594 discloses a supply circuit of the general kind defined in the first paragraph.
  • This known circuit powers at least two discharge lamps in such a manner that flicker therefrom occurs at different phases, so that, overall, flickerless operation is achieved.
  • a supply circuit as defined in the first paragraph is characterized in that the impedance is controllable and in that the circuit further includes monitoring means for monitoring the amplitude of the component of the power consumed by the lamp which is at the frequency of the a.c. supply, and means for controlling the variable impedance and thereby changing the rate of change of current in the inductive ballast in the course of each cycle of the a.c. supply in dependence upon the output of the monitoring means to substantially reduce the relative amplitude of said component and thereby the flicker of the lamp at said frequency.
  • the monitoring means comprises light sensing means.
  • the monitoring means may be arranged to monitor the D.C. current through the lamp.
  • the circuit is arranged so that the voltage across the controllable impedance is used to power the circuitry of the monitoring means in operation.
  • the circuit shown is a typically conventional supply circuit for a high pressure discharge lamp.
  • the circuit comprises the high pressure discharge lamp 1 connected across an A.C. supply 3, typically a 50 Hz 240 volt mains supply.
  • a ballast inductor 5 is connected in series on the live supply rail between the supply 3 and the lamp 1, a starting circuit 7 being connected across the lamp 1.
  • a power factor correction capacitor 9 is connected across the supply 3.
  • the starting circuit 7 causes the lamp 1 to strike by inducing high voltage spikes. The voltage across the lamp 1 then falls to the normal running voltage.
  • the lamp light output from such a circuit is of the general form shown in this figure although the magnitude of the flicker has been slightly exaggerated for the sake of clarity. It will be seen from this figure that the lamp light output reduces in magnitude at time intervals corresponding to every other half cycle of the supply voltage, resulting in a 50 Hz flicker component which is highly visible, this being due to asymmetries within the circuit or the lamp.
  • the purpose of the instant invention is to substantially eliminate the supply frequency of flicker that is at 50 Hz.
  • the timing and duration of the opening of the switch 15 is critical in the reduction of flicker.
  • the phase of the flicker varies by 17 degrees dependent on when, within a half cycle of the mains waveform the switch 15 is operated across a half cycle of the mains.
  • the magnitude of the flicker also varies slightly dependent on the timing of the opening of the switch 5 within the AC half cycle.
  • two vectors are combined, one being approximately minimum phase and the other maximum phase.
  • the maximum phase vector is generated by opening the switch 15 when the current is close to zero.
  • the length of this vector is proportional to the length of time the switch 15 is left open.
  • the second circuit in accordance with the invention to be described operates on the same principle as the first circuit.
  • the two zener diodes 11, 13 of the first circuit however are replaced by a single zener diode 17 connected across the output of a rectifier in the form of a diode bridge 19.
  • the diode bridge 19 ensures that although the current through the lamp changes sign, the current across the zener 17 is always in one direction. Thus the voltage across the switch 15 is always of one polarity, making the control of this voltage easier.
  • the switch 15 is suitably constituted by a VMOS FET 21 which is driven by a low power integrated circuit 23.
  • the integrated circuit 23 controls the FET 21 to be open for at least a small part of each half cycle of the supply voltage. This ensures that some rectified 10 volt pulses appear across the zener diode 17 with these pulses powering the integrated circuit 23.
  • the timing of these pulses suitably is arranged to be at current zero-crossing times since power consumed will then be a minimum, a trigger input to the integrated circuit 23 allowing mains synchronisation.
  • the integrated circuit includes a series arrangement of a charge subtraction circuit 34 comprising four transistors 25, 27, 29, 31 and a photodiode 33 connected across the outputs of the rectifier 19 i.e. the voltage rails Vdd, Vss.
  • the photodiode 33 is aranged such that it is responsive to light emitted by the lamp 1, a suitable viewing window being provided adjacent the photodiode within the unit containing the circuitry contained within the box 24.
  • a J-K flip-flop 35 is connected via a Schmitt trigger circuit 37 to the node between the photodiode 33 and transistor arrangement 25, 27, 29, 31.
  • the flip-flop 35 has outputs Q and Q which are arranged to address the gates of the four transistors 25, 27, 29, 31, the flip-flop 35 being clocked by a system clock 38.
  • the four FETs 25, 27, 29, 31 thus switch small capacitors 39, 41 between the photodiode 33 and the ground rail Vss alternately. Every time Q and Q change, this being dependent on the value of the JK inputs to the flip-flop 35 one of the capacitors 39 or 41 is discharged to ground and the other capacitor 41 or 39 is charged up to the voltage of the photodiode 33.
  • the output of the flip-flop 35 alternates at a frequency which is directly proportional to the intensity of the light falling on the photodiode 33.
  • a counter (not shown) connected to the integrated circuit 23 would display a count proportional to the light falling on the photodiode 33 integrated over a chosen counting period.
  • a voltage derived from the flicker component in the output of the flip-flop 35 is used to control the conductance of the FET 21 to thereby reduce the 50 Hz flicker in the lamp 1.
  • the clock rate of the flip-flop 35 is determined by the necessity to measure flicker accurately. It is found however that the system clock rate can be kept down to around 1 MHz. Such a clock rate will allow a light count of a few thousand over a quarter of a mains cycle and will minimise the power consumption of the integrated circuit 23.
  • additional photodiodes (not shown) may be connected in parallel with the photodiode 33.
  • different values of small capacitors 39, 41 may be switched in.
  • different light mountings or dirt on the sensing window to the photodiode it would be advantageous if this could be performed automatically dependent on the light count using an appropriate feedback circuit.
  • the lamp is a high pressure discharge lamp
  • the invention is applicable to other types of gas discharge lamps as long as the flicker is not spacially variant over the lamp, or, where there is some spatial variation in flicker, if light from the part of the lamp giving rise to a different flicker component can be shielded from the light sensing means.
  • circuits for monitoring the amplitude of the supply frequency component of the power of the lamp described herebefore is a digital circuit
  • an analogue circuit may be used instead. It is however particularly advantageous to use a digital implementation as an analogue implementation is likely to require more components which can not be incorporated in an integrated circuit. Furthermore an analogue implementation will be more prone to outside interference.

Landscapes

  • Circuit Arrangements For Discharge Lamps (AREA)
  • Circuit Arrangement For Electric Light Sources In General (AREA)

Claims (10)

  1. Schaltung zur Stromversorgung einer Entladungslampe (1) aus einer Wechselstromquelle (3), die ein induktives Vorschaltgerät (5) und eine Impedanz (11, 13, 15, 17, 19; 17, 19, 21) in Reihenschaltung mit der Lampe enthält, dadurch gekennzeichnet, daß die Impedanz steuerbar ist, und daß die Schaltung ferner Überwachungsmittel (25, 27, 29, 31, 33, 35, 37, 39, 41) zur Überwachung der Komponente des von der Lampe verbrauchten Stroms, die die Frequenz der Wechselstromquelle hat, aufweist, sowie Mittel (23) zur Steuerung der veränderbaren Impedanz, und damit zur Änderung der Änderungsrate des Stroms in dem induktiven Vorschaltgerät im Verlaufe jeder Periode der Wechselstromquelle in Abhängigkeit vom Ausgang der Überwachungsmittel, um die relative Amplitude der Komponente, und damit das Flackern der Lampe mit der genannten Frequenz nennenswert zu vermindern.
  2. Stromversorgungsschaltung nach Anspruch 1, bei der die Überwachungsmittel Lichtsensormittel (33) umfassen.
  3. Stromversorgungsschaltung nach Anspruch 2, bei der die Überwachungsmittel Mittel enthalten, um beim Gebrauch der Lampe von dieser Licht auf die Lichtsensormittel (33) zu übertragen.
  4. Stromversorgungsschaltung nach Anspruch 2, bei der die Lichtsensormittel (33) aus einer Photodiode bestehen.
  5. Stromversorgungsschaltung nach Anspruch 3 oder 4, bei der die Mittel zur Übertragung von Licht von der Lampe aus einer durchsichtigen Fluoreszenz-Faser bestehen.
  6. Stromversorgungsschaltung nach einem der vorhergehenden Ansprüche, die so ausgebildet ist, daß die Spannung an der steuerbaren Impedanz dazu verwendet wird, die Schaltung der Überwachungsmittel im Betrieb mit Strom zu versorgen.
  7. Stromversorgungsschaltung nach einem der vorhergehenden Ansprüche, bei der die steuerbare Impedanz als Parallelanordnung einer einzelnen ZENER-Diode (17) und eines steuerbaren Schalters (15; 21) vorgesehen ist, wobei die Parallelanordnung an dem Ausgang eines Gleichrichters in Form einer Diodenbrücke (19) liegt.
  8. Stromversorgungsschaltung nach Anspruch 1, bei der die steuerbare Impedanz als Parallelanaordnung von zwei gegensinnig verbundenen ZENER-Dioden (11, 13) und einem Schalter (15) vorgesehen ist.
  9. Stromversorgungsschaltung nach Anspruch 7 oder 8, bei der der steuerbare Schalter aus einem MOSFET (21) besteht.
  10. Stromversorgungsschaltung nach Anspruch 1, bei der die Überwachungsmittel so angeordnet sind, daß sie die Gleichstromkomponente durch die Lampe überwachen.
EP90305695A 1989-05-26 1990-05-25 Stromversorgungsschaltungen für Entladungslampen Expired - Lifetime EP0399835B1 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB898912129A GB8912129D0 (en) 1989-05-26 1989-05-26 Supply circuits for discharge lamps
GB8912129 1989-05-26
GB898919731A GB8919731D0 (en) 1989-05-26 1989-08-31 Supply circuits for discharge lamps
GB8919731 1989-08-31

Publications (2)

Publication Number Publication Date
EP0399835A1 EP0399835A1 (de) 1990-11-28
EP0399835B1 true EP0399835B1 (de) 1994-10-19

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Family Applications (1)

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EP90305695A Expired - Lifetime EP0399835B1 (de) 1989-05-26 1990-05-25 Stromversorgungsschaltungen für Entladungslampen

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EP (1) EP0399835B1 (de)
AT (1) ATE113156T1 (de)
DE (1) DE69013398T2 (de)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114567943B (zh) * 2022-02-10 2023-10-31 浙江大华技术股份有限公司 一种补光灯

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU493941A1 (ru) * 1973-03-09 1975-11-28 Каунасский Политехнический Институт Устройство дл питани газоразр дных ламп от сети переменного тока
DE3723971A1 (de) * 1987-07-20 1989-02-02 Ultralight Ag Stromversorgungsschaltung fuer eine gasentladungslampe

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Publication number Publication date
DE69013398D1 (de) 1994-11-24
EP0399835A1 (de) 1990-11-28
DE69013398T2 (de) 1995-05-11
ATE113156T1 (de) 1994-11-15

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