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Full-bridge inverter for discharge lamp lighting device with varied transistor zero voltage period

  • US 5,434,479 A
  • Filed: 09/22/1993
  • Issued: 07/18/1995
  • Est. Priority Date: 09/22/1992
  • Status: Expired due to Term
First Claim
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1. A discharge lamp lighting device comprising a DC power source having first and second terminals, a first series circuit including first and second switching elements and connected between said first and second terminals of said DC power source, a second series circuit including third and fourth switching elements and connected between said first and second terminals of said DC power source, a load circuit connected between a first connecting point connecting said first and second switching elements and a second connecting point connecting said third and fourth switching elements and comprising at least an LC resonance circuit and a discharge lamp as a load, and control means for variably altering ON/OFF timing of said first and second switching elements of said first series circuit in a range from an in-phase state to a 180 degrees phase-shifted state with respect to the ON/Off timing of said third and fourth switching elements in said second series circuit, said control means comprising means for alternately turning ON and OFF said first and second switching elements with a first zero-voltage period interposed for preventing said first and second switching elements from simultaneously turning ON, means for alternately turning ON and OFF said third and fourth switching elements with a second zero-voltage period, different from the first zero voltage period, interposed for preventing said third and fourth switching elements from simultaneously turning ON, wherein the ON/OFF cycle of said first series circuit is substantially identical to the ON/OFF cycle of said second series circuit, and means for generating a first ON period ratio of said first and second switching elements and for a generating a second ON period ratio of said third and fourth switching elements, the second ON period ratio being different from the first ON period ratio.

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