Switching converter with spike limiting circuit

Claim 1

A switching circuit comprising: (a) means for providing a DC voltage; (b) a transformer having a pair of inductively coupled, serially connected, primary windings; (c) means for electrically coupling the DC voltage means across a first one of the pair of windings during a first portion of a cycle and for inducing a voltage in a second one of the pair of windings during such first portion of the cycle, and for electrically coupling the DC voltage means across the second one of the pair of windings during a second, subsequent portion of the cycle and for inducing a voltage in the first one of the pair of windings during such second portion of the cycle; (d) means, responsive to an excess voltage corresponding to a level of the voltage induced in the pair of windings exceeding a predetermined voltage, for directing energy related to said excess voltage back to the DC voltage means, said directing means comprising: a capacitor fed by the excess voltage; inductive means for storing energy; switching means, responsive to a control signal, for electrically coupling the capacitor to the inductive means to transfer energy corresponding to the excess voltage stored in the capacitor to said inductive means, for electrically decoupling the capacitor from the inductive means to the DC voltage means to transfer the energy stored in the inductive means to the DC voltage means; and means for controlling the switching means comprising: a voltage divider connected in shunt with the capacitor, fed by the excess voltage, to provide a voltage proportional to the excess voltage stored in the capacitor; and means, coupled to the voltage divider and fed by a reference voltage, for producing the control signal in response to changes in the excess voltage stored in the capacitor relative to said reference voltage.