Patent ID: 8391034

Claim:
A power supply module configured for converting an alternating current (AC) voltage to a first direct current (DC) voltage and applying the first DC voltage to a load, the power supply module comprising: an AC/DC converter for converting the AC voltage to a primary DC voltage; a voltage transforming circuit configured for transforming the primary DC voltage to the first DC voltage, the voltage transforming circuit comprising a transformer, the transformer comprising a primary winding; a feedback circuit coupled to the primary winding of the transformer and configured for sampling a current flowing through the primary winding to generate a feedback signal; and a filtering circuit structured and arranged for filtering any surge voltage transmitted from the feedback circuit to the voltage transforming circuit; wherein the voltage transforming circuit maintains the first DC voltage at a predetermined value according to the feedback signal; the filtering circuit comprises a first capacitor, a first resistor, and a transistor, one end of the first capacitor is coupled between the feedback circuit and the voltage transforming circuit, the other end of the first capacitor is coupled to a base of the transistor, the base of the transistor is grounded through the first resistor, a collector of the transistor is coupled between the feedback circuit and the voltage transforming circuit, and an emitter of the transistor is grounded.