EP0399835A1 - Stromversorgungsschaltungen für Entladungslampen - Google Patents

Stromversorgungsschaltungen für Entladungslampen Download PDF

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Publication number
EP0399835A1
EP0399835A1 EP90305695A EP90305695A EP0399835A1 EP 0399835 A1 EP0399835 A1 EP 0399835A1 EP 90305695 A EP90305695 A EP 90305695A EP 90305695 A EP90305695 A EP 90305695A EP 0399835 A1 EP0399835 A1 EP 0399835A1
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.)
Granted
Application number
EP90305695A
Other languages
English (en)
French (fr)
Other versions
EP0399835B1 (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 supply circuits for discharge lamps.
  • the invention relates to supply circuits which are powered by an A.C. supply, for example an A.C. mains supply.
  • A.C. supply for example an A.C. mains supply.
  • flicker at the frequency of the supply can cause considerable annoyance.
  • Such flicker generally arises from asymmetries in either the supply waveform, the construction and operation of the lamp itself or in the associated circuitry.
  • 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.
  • a supply circuit for a discharge lamp powered by an A.C. supply including a variable impedance for connection in series with said lamp, means for monitoring the amplitude of the supply frequency component of the power driving the lamp, and means for using the amplitude to control the variable impedance so as in use to reduce substantially the amplitude of the flicker of the lamp.
  • the amplitude of the supply frequency component of the power of the lamp is monitored optically.
  • the amplitude of the supply frequency component of the power of the lamp is monitored by monitoring the D.C. current through the lamp.
  • the voltage across the variable impedance is used to power the circuitry which monitors the amplitude of the supply frequency component of the power through the lamp.
  • 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 50HZ 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 50HZ.
  • 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 are 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 23 includes a series arrangement of a charge subtraction circuit 24 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 to the photodiode within the unit containing the circuitry contained within the box 24.
  • a J-K flip-flop 35 is connected via a Schmidt 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.
  • the invention finds particular application to supply circuits for discharge lamps which are connected to an A.C. supply via an inductive ballast, the invention is relevant to lamp circuits which do not contain inductive ballasts, for example a lamp circuit incorporating an electronic ballast which does not include correction for flicker in itself.
  • 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)
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
GB8912129 1989-05-26
GB898912129A GB8912129D0 (en) 1989-05-26 1989-05-26 Supply circuits for discharge lamps
GB8919731 1989-08-31
GB898919731A GB8919731D0 (en) 1989-05-26 1989-08-31 Supply circuits for discharge lamps

Publications (2)

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

Family

ID=26295403

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90305695A Expired - Lifetime EP0399835B1 (de) 1989-05-26 1990-05-25 Stromversorgungsschaltungen für Entladungslampen

Country Status (3)

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

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114567943A (zh) * 2022-02-10 2022-05-31 浙江大华技术股份有限公司 一种补光灯

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2417594A1 (de) * 1973-04-13 1974-11-07 Matsushita Electric Works Ltd Flimmerfreie gasentladungslampenanordnung
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

Patent Citations (3)

* 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
DE2417594A1 (de) * 1973-04-13 1974-11-07 Matsushita Electric Works Ltd Flimmerfreie gasentladungslampenanordnung
DE3723971A1 (de) * 1987-07-20 1989-02-02 Ultralight Ag Stromversorgungsschaltung fuer eine gasentladungslampe

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114567943A (zh) * 2022-02-10 2022-05-31 浙江大华技术股份有限公司 一种补光灯
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

Also Published As

Publication number Publication date
DE69013398D1 (de) 1994-11-24
EP0399835B1 (de) 1994-10-19
DE69013398T2 (de) 1995-05-11
ATE113156T1 (de) 1994-11-15

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