| 摘要 |
<P>PROBLEM TO BE SOLVED: To obtain a resonance frequency detection method that can accurately detect a resonance frequency even if the resonance frequency of a series resonance circuit at the secondary side of a transformer largely varies. <P>SOLUTION: A step voltage is applied to a circuit at the primary side of the transformer via an inverter circuit (2) connected to the primary side of the transformer (1). A current that flows in the resonance circuit (5) connected to the secondary side of the transformer has only a component that coincides with a resonance frequency among frequency components transmitted to the secondary side. Accordingly, the current that flows in the resonance circuit at the secondary side becomes a current having a sine waveform equal to the resonance frequency in its frequency. Here in this invention, a current probe (16) is connected to the secondary side, and the zero cross of the resonance current that flows in the series resonance circuit at the secondary side is detected. Then, the zero cross of the detected current is detected (17), and the resonance frequency of the series resonance circuit is calculated on the basis of a cycle T between the zero cross points. As a result, a drive signal of an optimum resonance frequency can be fed to the primary side of the transformer even if the impedance of the the series resonance circuit varies. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
