| 摘要 |
The purpose of the present invention is to protect elements (14, 15) in a resonant inverter circuit (1) when the resonance frequency of the resonant inverter circuit (1) has changed, and not to stop the resonant inverter circuit (1) excessively. This resonant inverter circuit (1) includes two or more switch elements (14, 15). A detector (17) detects the output current of the switch elements (14, 15). A resonance frequency determination unit (22) determines a resonance frequency error in the resonant inverter circuit (1) if a prescribed number of times no less than two, the absolute value of the current detected by the detector (17) when turning off the switch elements (14, 15) is greater than or equal to a threshold value during a determined period which is at least twice as long as the switching period of the switch elements (14, 15). A control unit (23) stops the switching operation of the resonant inverter circuit (1) if the resonance frequency determination unit (22) determines a resonance frequency error in the resonant inverter circuit (1). |
