JPS5713977A - Controlling for pwm inverter - Google Patents

Abstract

PURPOSE:To maintain the content of higher harmonic components at low value in a PWM inverter output wave by a methd wherein the pulse width ratio is kept constant at each of the multiple rectangular pulses generated during a half wave period. CONSTITUTION:A basic pulse generating circuit 2 receives clock pulses from a clock pulse generating circuit 1 and transmits rectangular pulses (c) whose width is different from the received clock pulses to an integration circuit 3. The integration circuit 3 changes the received rectangular pulses (c) into triangular pulses (d) of different height and transmits them to an amplitude variable circuit 4. The amplitude variable circuit 4 converts the received triangular pulses into ones of the same height and different bases and transmits them to a composite circuit 6. Output of the composite circuit 6 is subjected to sequential switching by timing signal forming circuit 5 timing signals and is received by a comparing circuit 7 in which a comparison is made to a reference voltage EO. During the period of a level higher than EO, gate signals are supplied to a singal forming circit 9, causing switching signals X, -X, and Y to be outputted. This method results in a decrease of higher harmonics in an inverter output.