Electric lamp and discharge devices: systems – Current and/or voltage regulation – Automatic regulation
Patent
1998-08-06
1999-06-08
Wong, Don
Electric lamp and discharge devices: systems
Current and/or voltage regulation
Automatic regulation
315224, 315291, 315DIG4, G05F 100
Patent
active
059107138
ABSTRACT:
A current flowing through a discharge lamp 4 is detected by a current detecting circuit 5, and the detected current is outputted as a lamp current signal A to a feedback control circuit 7 where a difference between the lamp current signal A and the dimming control signal B is obtained and amplified, and then a amplified signal D is outputted to an adder 12 which adds the amplified signal D to the dimming control signal B to constitute a control signal E. The control signal is fed back to a high frequency power supply 2. When a comparing circuit 15 detects that the light level of the dimming control signal B with respect to the full light becomes higher than or equal to 40% to 60%, the feedback circuit is disconnected by operating a switch 13 provided between an error amplifying circuit 9 and an adder 12 to stop the feedback control. When a light level of a discharge lamp 104 is smaller than or equal to a predetermined value, first and second reference voltage 108a and 108b are switched by a two-stage switching circuit 109. A comparator 107 compares a detection voltage 106 of the discharge lamp 104 with the first reference voltage 108a, or the detection voltage 106 with the second reference voltage 108b. When the voltage of the discharge lamp 104 becomes high, a control circuit 110 supplies to a high frequency power supply 102, a control signal 112 for interrupting, or reducing an output of the high frequency power supply 102.
REFERENCES:
patent: 4870327 (1989-09-01), Jorgensen
patent: 5198726 (1993-03-01), Van Meurs et al.
patent: 5449981 (1995-09-01), Auld, Jr. et al.
Arai Takeshi
Bunya Jun
Eguchi Kentaro
Nagai Satoshi
Nishi Kenichiro
Mitsubishi Denki & Kabushiki Kaisha
Mitsubishi Lighting Fixture Co., Ltd.
Philogene Haissa
Wong Don
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