El backlight drive circuit for LCD display

摘要

An EL backlight device drive circuit useful with a camera LCD display. The backlight device is connected to the flash storage capacitor of the camera flash circuit for its energy source. Pulsing of the DC voltage from the storage capacitor is accomplished by a switching transistor coupled across the EL backlight device driven from a fixed duty cycle pulse source via an AC coupled pulse differentiating circuit. The AC coupled circuit reduces the On time duty cycle of the transistor relative to the pulse train duty thereby increasing the ON time duty cycle of the EL backlight device to increase its light output operating efficiency. With increased operating efficiency, a higher value coupling resistor is inserted between the EL backlight device and flash storage capacitor to thereby limit the AC current through the EL backlight device to a predetermined safety operating level.