Patent ID: 7808188

Claim:
A driving circuit for driving at least one lamp, comprising: a power switching circuit connected with a power source to generate an input current; a first transformer connected between the power switching circuit and the lamp and having a primary winding connected with the power switching circuit, a secondary winding for transforming the input current to drive the lamp, and at least one induction winding for inducing a voltage in response to a current which drives the lamp; and a feedback control circuit having a terminal connected to the induction winding so as to measure a voltage variation of the primary winding through the induction winding and output a power control signal, wherein the power switching circuit adjusts the current for driving the lamp according to the power control signal, wherein the feedback control circuit comprises: a voltage transforming circuit connected to the primary winding of the first transformer to measure the voltage variation and output a feedback voltage; and a power control circuit connected with the voltage transforming circuit to receive the feedback voltage and output the power control signal, wherein the power switching circuit adjusts the current for driving the lamp according to the power control signal; wherein the voltage transforming circuit comprises a filter connected with the primary winding; wherein the filter comprises: a capacitor having one terminal connected with the primary winding; and a resistor connected with the other terminal of the capacitor; wherein the voltage transforming circuit further comprises a voltage stabilizer connected with the filter; wherein the voltage stabilizer comprises: a first diode backward connected with and between a ground and the filter; and a second diode forward connected with the filter.