Patent ID: 6272024
Filing Date: 2001-08-07
Classification: H02M

Abstract:
A d.c.-to-d.c. converter for feeding a load from a d.c. power supply, comprising:(a) a switching device to be connected across a d.c. power supply, the switching device having a stray capacitance;(b) a transformer having a winding to be connected across the d.c. power supply via the switching device, the transformer winding having a leakage inductance and a stray capacitance;(c) a rectifying and smoothing circuit connected to the transformer for rectifying and smoothing an output therefrom;(d) a control circuit for turning the switching device on and off in order to provide a converter output voltage; and(e) a surge suppressor circuit having a serial connection of a surge-absorbing capacitor and a rectifying diode and a resistor, which serial connection is connected in parallel with the winding of the transformer, for absorbing a surge voltage developing in the transformer winding each time the switching device is turned off, the rectifying diode having a predetermined reverse recovery time that is longer than half the cycle of a ringing voltage developing in the transformer winding owing to the leakage inductance and stray capacitance of the transformer winding and to the stray capacitance of the switching device and shorter than an expected minimum nonconducting period of the switching device.