An auxiliary quasi-resonant dc tank (AQRDCT) power converter with fast
current charging, voltage balancing (or charging), and voltage clamping
circuits is provided for achieving soft-switched power conversion. The
present invention is an improvement of the invention taught in U.S. Pat.
No. 6,111,770, herein incorporated by reference. The present invention
provides faster current charging to the resonant inductor, thus
minimizing delay time of the pulse width modulation (PWM) due to the
soft-switching process. The new AQRDCT converter includes three tank
capacitors or power supplies to achieve the faster current charging and
minimize the soft-switching time delay. The new AQRDCT converter further
includes a voltage balancing circuit to charge and discharge the three
tank capacitors so that additional isolated power supplies from the
utility line are not needed. A voltage clamping circuit is also included
for clamping voltage surge due to the reverse recovery of diodes.