Patent ID: 7126833

Claim:
An auxiliary quasi-resonant dc tank converter, comprising: an ac power supply and an ac bus; a dc power supply for providing dc current to a dc bus; an inverter having at least one phase leg connected to said ac bus and connected across said dc bus, said inverter having at least one main switching device per phase leg; a quasi-resonant dc tank circuit coupled in parallel with said dc power supply for generating a quasi-resonant voltage across said dc bus, said quasi-resonant dc tank circuit including, an upper resonant capacitor and a lower resonant capacitor connected in series as a resonant leg, a first dc tank capacitor, a second dc tank capacitor, and a third dc tank capacitor connected in series as a tank leg, an auxiliary quasi-resonant circuit coupled across the junction of said upper and lower resonant capacitors, the junction of said first and second dc tank capacitors and the junction of said second and third dc tank capacitors, said lower resonant capacitor being coupled across said dc bus, said resonant leg being coupled across said tank leg, and a first clamping means coupled across said upper resonant capacitor, said auxiliary quasi-resonant dc tank converter further comprising a charge circuit coupled across the junction of said first and second dc tank capacitors and the junction of said second and third dc tank capacitors, wherein said charge circuit further comprises a transformer coupled across said resonant inductor feeding a diode bridge to charge said second tank capacitor.