Patent ID: 7394209
Filing Date: 2008-07-01
Classification: H02M,H05B,Y02B

Abstract:
1. A liquid crystal display system comprising: a liquid crystal display panel; a cold cathode fluorescent lamp for illuminating said liquid crystal display panel; a secondary transformer winding coupled to said cold cathode fluorescent lamp for providing current to said cold cathode fluorescent lamp; a primary transformer winding coupled to said secondary transformer winding for providing magnetic flux to said secondary transformer winding; a first switch coupled to said primary transformer winding for allowing a forward-biased DC current to pass through said primary transformer winding; a second switch coupled to said primary transformer winding for allowing a reverse-biased DC current to pass through said primary transformer winding; a sense resistor electrically coupled to said cold cathode fluorescent lamp and electrically coupled to ground for providing a voltage feedback signal representing current through said cold cathode fluorescent lamp; a feedback control loop circuit coupled to said cold cathode fluorescent lamp and electrically coupled to said sense resistor for receiving a said voltage feedback signal and controlling power supplied to said cold cathode fluorescent lamp when said voltage feedback signal is above a predetermined threshold; and an input selector pin coupled to said feedback control loop circuit for selecting between linear mode power control and pulse width modulation power control.