Patent ID: 7054168

Claim:
In a power converter for converting an input DC voltage into an output DC voltage at first and second output terminals and including synchronous rectification on a secondary side of said converter, an undershoot eliminator circuit for discharging an energy storage element in an auxiliary supply on said secondary side of said converter, comprising: a transistor having a gate terminal, a source terminal, and a drain terminal, the drain terminal of the transistor connected to said storage element, the source terminal of the transistor connecting to the said first output terminal; means for trapping charge on the gate terminal of said transistor while said converter is on; and means for coupling the voltage on said first output terminal to said gate terminal, such that, when said converter goes off and said output voltage begins to drop, the trapped charge causes the gate-to-source voltage of said transistor to increase until the gate of said transistor is sufficiently saturated to cause said transistor to turn on for a sufficient time to cause said storage element to discharge.