Patent ID: 7130201

Claim:
A power supply device for outputting stable programmable power supply, comprising a rectify/filter circuit, a transformer, a secondary filter circuit, and a DC output terminal; said rectify/filter circuit being coupled to an AC power supply and comprised of a capacitor and an inductor to constitute a full wave rectify circuit for rectifying and filtering said AC power supply to obtain a stable DC power supply, and said transformer being coupled to said rectify/filter circuit to reduce the voltage of said DC power supply after being rectified and filtered, and to output a direct current from said DC output terminal after a secondary filter by said secondary filter circuit; wherein said power supply device comprises a clamp circuit, and said clamp circuit is coupled to a Another Aspect Circuit of said transformer, such that said clamp circuit reduces a high voltage produced when a MOSFET is turned off and releases energy of said transformer caused by a magnetic leakage and an induction and then stored in said transformer, thereby reducing the high voltage borne by said MOSFET and enhancing the reliability of said MOSFET; and wherein said clamp circuit releases energies by converting an original reverse bias voltage into a forward bias voltage when the MOSFET is turned off, so that said clamp circuit by itself releases and eliminates the energy if the voltage exceeds a referenced normal rated reverse voltage and a Zener diode is also set to a reverse bias voltage to prevent said transformer from being saturated.