| 摘要 |
PURPOSE:To maintain preferably the synchronizing accuracy of controlling to follow up the frequency with a phase locked loop by correcting the frequency characteristics of an impednace element of a phase shift circuit interposed between an inverter and a phase comparator. CONSTITUTION:The output of an inverter 4 is supplied to a load tank circuit 5 which has a heating coil L, and a power factor compensating capacitor C, and the output frequency of the inverter 4 is followed up to the intrinsic vibration frequency of the load tank circuit 5 by controlling with a phase locked loop using a phase comparator 13, and a voltage controlled oscillator 15 becoming zero in the phase difference between the output voltage 6 and the output current 7. The frequency followup accuracy is improved by providing a frequency-to- voltage converter 16 which converts the output frequency of the oscillator 15 into the output voltage proportional to the frequency and a circuit 17 which compensates the frequency characteristics of an impedance element circuit such as a phase shift circuit 12 of a followup circuit by the output in a transistor inverter device. |
