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Coupled Inductor Lossless Snubber Circuit for a Transistor Switching Converter

IP.com Disclosure Number: IPCOM000041899D
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Sathe, MM: AUTHOR

Abstract

The circuit illustrated reduces turnoff switching losses and increases efficiency by transferring uncoupled energy (due to transformer primary leakage inductance) to the input DC source, unlike conventional snubbers which dissipated energy in the circuit. The figures disclose a coupled-inductor lossless turnoff snubber circuit developed to reduce the transistor switching losses in a forward averaging switching mode power supply. The circuit consists of a capacitor, a diode and an energy feedback winding provided in the output transformer T1. In this design the trapped inductive energy in the transformer primary is transferred to the capacitor C, during the turnoff switching transition of the transistor Q1. This energy transfer is associated with a current pulse I1 (Figs. 4, 7) flowing to capacitor C.

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Coupled Inductor Lossless Snubber Circuit for a Transistor Switching Converter

The circuit illustrated reduces turnoff switching losses and increases efficiency by transferring uncoupled energy (due to transformer primary leakage inductance) to the input DC source, unlike conventional snubbers which dissipated energy in the circuit. The figures disclose a coupled-inductor lossless turnoff snubber circuit developed to reduce the transistor switching losses in a forward averaging switching mode power supply. The circuit consists of a capacitor, a diode and an energy feedback winding provided in the output transformer T1. In this design the trapped inductive energy in the transformer primary is transferred to the capacitor C, during the turnoff switching transition of the transistor Q1. This energy transfer is associated with a current pulse I1 (Figs. 4, 7) flowing to capacitor C. Capacitor C sinks all the uncoupled inductive energy available at the transformer primary without allowing the transistor to exceed the maximum voltage limit. It slows down the turnoff switching time of Q1 and thus reduces the turnoff switching loss. The inductive energy thus stored in the capacitor C is further transferred to the input primary DC source (current I2 in Figs. 5, 7) through the coupled inductor energy feedback (CIEF) winding. The transformer core demagnetizing current (I3 in Figs. 4, 5) flows through the CIEF winding during the turnoff period of Q1. The ideal expression for the capacitor discharge current I2 (Figs. 5, 7) through the CIEF winding is

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