High power-factor converter for motor drives and power supplies

Claim 1

A high power factor converter for use with motor drives and power supplies to convert an a.c. input voltage to a d.c. output voltage comprising: first conversion means for providing a d.c. output voltage having pre-selected voltage characteristics and for performing a voltage conversion during a portion of the input voltage cycle in which the input voltage level exceeds that of the output voltage level, said first conversion means being a "buck" type voltage converter and including first semiconductor means; second conversion means connected to said first conversion means for providing said output voltage and for performing a voltage conversion during a portion of the input voltage cycle in which the output voltage level exceeds that of the input voltage level, said second conversion means being a "boost" type voltage converter and including second semiconductor means; rectification means connected between the input voltage source and said first conversion means; and, control means responsive to the relative levels of the input and output voltages to control operation of said first and second semiconductor means and thereby operate the first and second conversion means on a time sharing basis, said control means including steering logic means responsive to the instantaneous relative voltage levels of the input and output voltages to switch said second semiconductor means into and out of conduction, and for controlling operation said first semiconductor means on a pulse width modulated basis, and said control means further including means sensing for the actual voltage characteristics of the output voltage, means for storing a pre-selected set of output voltage characteristics, and means for comparing the sensed actual voltage characteristics with the pre-selected set thereof.