| 摘要 |
PURPOSE:To hold the oscillating frequency of an inverter circuit in response to the variation in the inductance of a load coil to the prescribed value by detecting the resonance point of the circuit by adding a resonance point detector. CONSTITUTION:A load circuit having a series circuit of a load coil 5 and a resonance condenser 6, a switching element 1 and a series inverter circuit 2 are provided. It is detected whether or not the circuit 2 operates in the vicinity of the resonance point by resonance point detectors 11, 12 made of gate circuits for sampling the voltage difference of both terminals of the switching element 2, and the circuit 2 is operated when it is higher or lower than the resonance frequencies of the load circuits 5, 6. In this manner, the oscillating frequency can be held always above or lower than the resonance frequency of the load circuit in response to the variation in the inductance of the load coil. |
