US 7,009,850 B2 · Soft switching converter using current shaping

Abstract

A converter topology that eliminates reverse recovery losses in its output rectifying semiconductor devices employs an AC injection voltage source in series with a power transformer primary winding. Input semiconductor switches in the converter's primary circuit are controlled to provide in the power transformer secondary a voltage across the winding or windings in a first direction forward biasing one of the output rectifying devices followed by a lower level reverse biasing voltage produced by the injection voltage. This lower level voltage across the secondary turns off the previously conducting rectifier device and drives carriers out of its semiconductor junction or junctions to eliminate reverse recovery losses occurring when the secondary applies a higher level reverse bias across the non-conducting rectifier device. The injection voltage source can be a transformer in addition to the power transformer having a primary winding in series with the primary winding of the power transformer and a secondary winding connected to ground through a capacitor. In addition to preventing reverse recovery losses in the rectifying devices in the secondary, the injection voltage transformer also injects an AC triangular waveform current into the current in the converter primary input circuit to the junction of the semiconductor switches where they are connected in a bridge circuit supplying the power transformer primary. By this, the injection voltage source assures zero voltage switching of the semiconductor switches even at light loads.

Claims41

Dependent claims

A power conversion circuit having a power transformer, four semiconductor switching elements connected as a bridge across an input to the power conversion circuit and connected to a primary winding of the power transformer to reverse current through the primary winding, a split secondary winding on the power transformer, a first unidirectional current conducting device connected from one end of the split secondary winding to an inductor, a second unidirectional current conducting device connected from a second end of the split secondary winding to the inductor, the inductor and a connection to an interconnection between two halves of the split secondary winding being connected to an output of the power conversion circuit, an injection voltage source connected to the primary winding of the power transformer for applying an injection voltage to the primary winding in addition to an input voltage to the primary winding via the semiconductor switching elements connected as a bridge.

A power conversion circuit having a power transformer with at least one primary winding and at least one secondary winding, a primary circuit connected with the primary winding and adapted to deliver a main primary current alternating in direction through the primary winding, a secondary circuit connected to the secondary winding and adapted to receive a main secondary current from the secondary winding and to deliver electrical power to a load, at least one semiconductor unidirectional current conducting device in at least one of the primary and secondary circuits and adapted alternately to conduct a main current passing through an associated one of the windings of the power transformer;

the improvement comprising:
an injection voltage source connected to apply a supplemental reverse bias voltage to the semiconductor unidirectional current conducting device sufficient to terminate forward conduction in the device and to deplete carriers in the device at times prior to each reverse biasing of the device by an alternating of the main primary current causing a reversal of voltage across the associated power transformer winding.

A power conversion circuit having a power transformer with a primary winding and at least one secondary winding, an input circuit connected to the primary winding, an output circuit connected with the at least one secondary winding and having a semiconductor rectifying means coupled in current conducting relation with the at least one secondary winding, an inductor coupled in current conducting relation between the semiconductor rectifying means and an output load connection;

the improvement comprising:
means for applying a first, relatively low reverse bias voltage to the semiconductor rectifying means to halt forward conduction and deplete carriers in the semiconductor rectifying means prior to each application to the semiconductor rectifying means of a reverse bias larger than the first, relatively low reverse bias voltage.

Dependencies are inferred from the claim text.

Soft switching converter using current shaping

Life of this patent

Soft switching converter using current shaping

Life of this patent

Abstract

Claims41