Control device for choppers parallel between a DC power source and a load for producing balanced chopper currents

Claim 1

A control device for an apparatus having a plurality of choppers connected in parallel between a DC power source and a load, said apparatus supplying a voltage to said load, each of said choppers including a semiconductor switch, said control device comprising: a plurality of DC current detection circuits, each connected to one of said plurality of choppers for detecting a chopper current of one of said plurality of choppers, respectively; a first circuit connected to said plurality of DC current detection circuits for generating an average value of said plurality of chopper currents; a plurality of second circuits, each connected to one of said DC current detection circuits and to said first circuit for comparing one of said chopper current detected by one of said DC current detection circuits with said average value to derive deviation values, respectively; a third circuit for detecting an output voltage of said apparatus; a fourth circuit connected to said third circuit for comparing said output voltage of said apparatus with a predetermined voltage reference and for generating a voltage control signal based on a comparison result so that said output voltage is controlled to be equal to said predetermined voltage reference; a plurality of fifth circuits, each connected to said fourth circuit and one of said second circuits for adding a value of said voltage control signal and one of said deviation values to produce a modified voltage control signal, respectively, so that the values of said plurality of chopper currents are substantially equal to each other; an oscillator circuit for generating a pulse signal; a plurality of phase shifters, each connected to said oscillator circuit and one of said plurality of fifth circuits for shifting a phase of said pulse signal based on said modified voltage control signal, respectively; a plurality of pulse amplifier circuits, each connected to one of said plurality of phase shifters and one of said choppers, for isolating and supplying an output signal of one of said plurality of phase shifters to one of said semiconductor switches of one of said choppers, respectively, each of said semiconductor switches being controlled to be switched ON and OFF based on one of said output signals of said plurality of pulse amplifier circuits, respectively; and a plurality of limiter circuits, each connected to one of said second circuits for limiting said deviation value and for supplying said limited deviation value to one of said fifth circuits as said deviation value, respectively.