Discharge lamp driving circuit having resonant circuit defining

Details Discharge lamp driving circuit having resonant circuit defining Discharge lamp driving circuit having resonant circuit defining

1997-06-19

1999-06-22

Wong, Don

Electric lamp and discharge devices: systems

Current and/or voltage regulation

Automatic regulation

315209R, 315DIG4, 315DIG7, H05B 3702

Patent

active

059145722

ABSTRACT:
An improved discharge lamp driving circuit of a charge-pump type capable of suppressing a ripple in an envelop of a lamp current at the time of dimming the lamp or at a low environmental temperature. The circuit includes an inverter having switching elements Q1 and Q2 for converting a voltage across a smoothing capacitor Ce into a high frequency power which is applied through a resonant circuit to the discharge lamp Ld. A capacitor Cin is connected to one end of the resonant circuit to vary a DC voltage of the output of the rectifier in accordance with a varying instantaneous value of the high frequency current or voltage appearing in the resonant circuit. A control circuit is provided to give a control signal for alternately turning on and off the switching elements Q1 and Q2. A feedback circuit FB is provided to modulate the control signal within a permissible range given to the control circuit in such a manner as to adjust the timing of turning on and off the switching elements Q1 and Q2 in a feedback manner based upon a lamp current detected by a current sensor SI, for reducing the ripple in the lamp current. A mixer MX is included to compensate for the lamp current in consideration of a dimmer signal Dim of dimming the lamp in order to suppress the ripple which would otherwise increase due to the dimming of the lamp.

REFERENCES:
patent: 5371440 (1994-12-01), Liu et al.

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