Digital Lamp Balance System With Individual Lamp Current Control Capability for an LCD TV

A digital lamp balance system that equalizes lamp current of liquid crystal display (LCD) backlight is implemented in this letter. The proposed digital balance circuit consists of a balance switch which is in series with the lamp and a dc-blocking capacitor which also acts as a ballast capacitor for parallel lighting. The parasitic capacitance of the balance switch is used as parallel impedance which makes the lamp current decrease. Microcontroller unit controls each lamp current by changing the pulsewidth modulation duty ratio of a balance switch. The specified circuit, analysis, balance principles, and experimental results of the proposed system will be presented for a 46-in LCD TV.