Patent ID: 8093829

Claim:
A lamp driving device with an open voltage control, comprising: a DC power source for providing a DC signal to a square wave switch; the square wave switch for converting the DC signal from the DC power source into a square wave signal and outputting the square wave signal to an LC resonant circuit; the square wave switch also receiving a control signal from a square wave controller to control an amplitude of the square wave signal; the LC resonant circuit for converting the square wave signal from the square wave switch into a sinusoidal wave signal and then outputting the sinusoidal wave signal to a driver transformer; the driver transformer for converting the sinusoidal wave signal to drive the lamp; a current detector disposed between a secondary side of the driver transformer and the square wave controller for detecting an abnormal operation of the lamp, if the lamp operates abnormally, the current detector outputting a control signal to a PWM control pin of the square wave controller; and the square wave controller for receiving the control signal from the current detector through the PWM control pin and adjusting the square wave signal of the square wave switch based on the control signal, wherein the current detector uses a switch element to detect the current flowing through the secondary side of the driver transformer and the lamp, if the lamp operates abnormally, then the switch element is set to be open-circuit to let the current flow to a capacitive element instead and to charge the capacitive element, when a voltage of the capacitive element exceeds a reference voltage of a comparator, the comparator outputs the control signal to the square wave controller.