| 摘要 |
PROBLEM TO BE SOLVED: To protect a converter against excessive current at the time of start-up when AC input is recovered by providing an input current phase controlling circuit which generates input voltage in phase with the current detected by a current detector at the time of start-up of the converter. SOLUTION: An input current feedback 22 is connected to a phase controlling circuit 52 of an input current phase controlling circuit 51. When AC input is recovered and feedback current is present, the inputs of switching circuits 53a-53c are switched to the phase controlling circuit 52 side. The outputs of the switching circuits 53a-53c are used as phase references for allowing the input voltage to be in phase with the input current feedback 22 before a converter is started up. After the converter is started up, the inputs of the switching circuits 53a-53c are switched to the output sides of a PLL circuit 19 and then the converter is controlled as usual. By this method, the converter can be started up rapidly and smoothly when AC input is recovered. |
