| 摘要 |
A power supply apparatus for use in electroplating includes an input-side rectifier (32). A rectifier output is converted into high-frequency signals in inverters (38a, 38b), which are transformed in transformers (48a, 48b). When the transformed high-frequency signals from the transformers are of positive polarity, they are rectified by a diode (50a or 50b) to cause a positive current to be supplied to a load (60). When the transformed high-frequency signals are of negative polarity, they are rectified by a diode (50c or 50d) to thereby cause a negative current to flow through the load. A first IGBT (54a) is connected in series with each of the diodes (50a, 50b) and is rendered conductive and nonconductive at a frequency lower than the high-frequency signal. Also, a second IGBT (54b) is connected in series with each of the diodes (50c and 50d) and is rendered nonconductive when the IGBT and nonconductive at the lower frequency. When the first IGBT is rendered conductive, the second IGBT is rendered nonconductive, and vice versa. The inverters (38a, 38b) are controlled in synchronization with the firs t and second IGBTs (54a, 54b) in such a manner that the high-frequency signal can have a larger magnitude when the second IGBT (54b) is conductive than when the first IGBT (54a) is conductive.
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