SOUND RESONATING REMOVAL CIRCUIT FOR HIGH INTENSITY DISCHARGE LAMP

摘要

A sound resonance removal circuit for a HID(High Intensity Discharge) lamp is provided to remove sound resonance by varying a frequency through a sweep of various frequency bands on a real time. A first resistor(R1) and a second resistor(R2) are connected to an output terminal of a SMPS(Switching Mode Power Supply). A first capacitor(C1) is parallel connected to the second resistor. An oscillating decision circuit(10) is connected between the first resistor and the second resistor. The oscillating decision circuit includes a first Schmitt trigger inverter(U2A) and a second Schmitt trigger inverter(U3A). An oscillating circuit(20) includes a third Schmitt trigger inverter(U4A), a third resistor(R3), and a second capacitor(C2). A first buffer(U5A) receives an output voltage of the oscillating circuit. A final supply voltage is applied to a drive IC for driving a lamp through a frequency variable circuit.