| 摘要 |
PROBLEM TO BE SOLVED: To protect a converter against failure by detecting the disturbance of an input voltage waveform when the converter is employed for converting power of an electric vehicle. SOLUTION: In a switching timing control circuit for a converter 4 comprising a switching element for converting an AC power from a stringing 1 into a desired DC voltage, the polarity of an input voltage is detected from the waveform thereof through a resonance filter 8 and compared with the polarity of an input current. Upon abrupt variation in the AC period of input voltage waveform, the reverse phase of voltage and current is detected and the switching elements are turned off entirely thus protecting the switching element against breakdown due to abrupt increase of DC voltage or overcurrent. |
