| 摘要 |
PROBLEM TO BE SOLVED: To provide a high frequency power supply with less loss at lower cost. SOLUTION: A primary coil 26a of a high frequency transformer 26 is connected in series to IGBTs 27, 28 passing a current in the opposite direction thereto between the terminals of an AC power supply 22 and diodes 29, 30 are connected in antiparallel to the IGBTs 27, 28, respectively. A voltage detecting circuit 35 is formed to apply the collector voltages of the IGBTs 27, 28 to a common resistance voltage-dividing circuit via the diodes and a high-pass filter 40 derives resonance frequency components from a voltage Vb detected by the voltage detecting circuit 35. A timing setting circuit 43 compares a voltage Vh output by the high-pass filter 40 with a reference voltage Va to set ON-timings of the IGBTs 27, 28 and an output control circuit 46 further sets OFF-timings. The IGBTs 27, 28 are driven at a common gate voltage Vg by a driving circuit 47. |
