| 摘要 |
PROBLEM TO BE SOLVED: To provide a controller for a DC-DC converter which outputs a high-resolution PFM signal while using a low-cost CPU. SOLUTION: In a PFM signal generating circuit 12 which changes switching frequency, reference clocks of 5MHz are inputted into CPU30 so as to enable the operation of an operation part 31. Moreover, the internal counter 32 of the CPU30 counts clocks n times as many as those of the cycles stipulated by the switching frequency, by counting the reference clocks, and generates a signal which has frequency components one-nth the switching frequency synchronously with the finish of the count operation. Then, a PFM signal is generated which has switching frequency components by multiplying a count output signal in a multiplicator 40. COPYRIGHT: (C)2004,JPO&NCIPI
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