| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a DC power device achieving high efficiency and proper power factor for a low load and achieving high power factor and proper efficiency for a high load while restraining a power supply higher harmonic current by an inexpensive circuit configuration. <P>SOLUTION: A switching means is short-circuited twice for a 1/2 period from a zero-cross point of an AC power supply detected by a zero-cross detecting means when a value of a ratio of a target DC voltage set by a target voltage setting means to a power supply voltage detected by a power supply voltage detecting means is less than a fixed value. First and second short-circuit intervals of the two short-circuits are set at 0.2 to 0.4 ms for a power supply frequency of 50 Hz detected by a frequency detecting means and set at 0.16 to 0.33 ms for a power supply frequency of 60 Hz. The number of short-circuits of the switching means is changed to any number which is more than 2 in response to the value of the ratio and in which the noise frequency of the DC power device does not exceed the operation noise frequency of a motor for assembled equipment when the value of the ratio is larger than or equal to the fixed value. <P>COPYRIGHT: (C)2011,JPO&INPIT |
