Patent ID: 6438004
Filing Date: 2002-08-20
Classification: H02M,Y02B

Abstract:
A power conversion apparatus including:at least a pair of main switches composed of serial-connected first and second main switches, one of the ends of said first main switch being connected with the positive side of a DC power supply, one of the ends of said second main switch being connected to the negative side of said DC power supply; a diode connected in parallel with each of said main switches so as to become reverse biased with respect to said DC power supply; a main-switch snubber capacitor connected in parallel with each of said main switches; a load connected with the junction between said pair of main switches; and a control circuit for forming a switching signal for controlling the switching operation of said main switches by using a load voltage and/or a load current as an input thereof, wherein said main switches are controllably switched according said switching signal from said control circuit so as to generate an output, said power conversion apparatus comprising: a first auxiliary resonant circuit including serial-connected first and second auxiliary switches and a resonant inductor connected in series with said second auxiliary switch, said first auxiliary resonant circuit being connected with each of the positive side of said DC power supply and the junction between said pair of main switches; a diode connected to each of said first and second auxiliary switches so as to become reverse biased with respect to said DC power supply; and voltage detecting means for detecting the voltage across each of said main switches and auxiliary switches; wherein said control circuit is applied with a voltage signal as an input representing said voltage across each of said main switches and auxiliary switches from said voltage detecting means; said control circuit being adapted to provide a turn-on signal to said first and second auxiliary switches according to said input before a turn-on signal as the switching signal is provided to said first main switch; said control circuit being adapted to provide the turn-on signal to said first and second auxiliary switches when the load current passes through said diode connected in parallel with said second main switch, so as to turn on said first and second auxiliary switches to direct the current from said DC power supply to said resonant inductor; whereby a resonant circuit is formed by said resonant inductor and said snubber capacitors connected in parallel with said main switches when the current of said resonant inductor goes up approximately to the load current; wherein said control circuit is adapted to output a signal for turning on said first main switch when the voltage across said first main switch goes down approximately to zero through the resonance in said resonance circuit.