Discharge lamp driving circuit having resonant circuit defining two resonance modes

Publication Date
1999-06-22Filing Date
1997-06-19Inventor
Lee, Fred C.
Yamauchi, Tokushi
Qian, Jinrong
Metadata
Show full item recordAbstract
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.
Assignee
Virginia Tech Intellectual Properties, Inc.
Matsushita Electric Works, Ltd.
Patent Number
5914572
Application Number
8878821
Primary/U.S. Class
315/307
Other/U.S. Class
315/209R
315/DIG4
315/DIG7
CPC Class
H05B41/28
H05B41/2858
H05B41/3921
Y10S315/04
Y10S315/07
Patent Type
utility
Collections
- Virginia Tech Patents [687]