To obviate the need for resistance for resonance prevention and reduce loss by carrying out control mainly based on a current control loop.
A PID amplifier 34 compares a half-bridge output current I1 with a reference current IR and amplifies and inputs the result of comparison to a PWM circuit 10. The PWM circuit 10 compares the output of the PID amplifier 34 with the output of a PWM carrier generator 38 and generates PWM signals G1, G2 to drive switching elements 11, 12. A PID amplifier 35 compares a half-bridge output current I3 with the sum of the reference current IR and the output V36 of a PID amplifier 36 from an integrated control unit 28 and amplifies the result of comparison. At a PWM circuit 27, the output of the PID amplifier 35 is compared with the output of the PWM carrier generator 38 and PWM signals G3, G4 are generated to drive switching elements 23, 24. The voltage of a capacitor 19 that provides a bias power supply is controlled by driving the switching elements 23, 24.
SATO YASUAKI
SUZUKI MASUO
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