Constant current regulator using igbt's with simplified timing

Abstract

A constant-current AC regulator comprises a switching network including two pulse-width modulator (PWM) transistors and two half-cycle transistors, a PWM transistor driver circuit, a main power transformer with two primary windings, a current sensing network, and an electronic control unit. The control unit generates a multiple pulse train signal with pulse widths based on the difference between the instantaneous load current and a predetermined design load current. The PWM transistor driver converts the pulse train signal into voltage signals appropriate for driving the PWM transformers of the switching network. The instantaneous load current is measured by the current sensing network Each set of a PWM transistor plus a half-cycle transistor carries current during a portion, e.g. half of the AC cycle. Only one primary winding is energized at any instant. Each transistor is preferably an IGBT transistor, and each pair of PWM transistor plus half-cycle transistor may comprise a dual IGBT chip. A constant current is expressed by the varying pulse widths with a high number of pulses per cycle. In one embodiment,