| 摘要 |
PROBLEM TO BE SOLVED: To provide a signal processing circuit for a step-up type DC-DC converter improving switching efficiency in a step-up-down operating mode by using the same switching frequency even in all operating modes of a step-up operation, a step-down operation and the step-up-down operations. SOLUTION: The signal processing circuit is composed of a voltage-level shift appliance 11 generating a first comparison voltage and a second comparison voltage from an error voltage and a waveform generator 12 generating a first waveform signal and a second waveform signal whose phase is an inverted phase of the first waveform signal. The signal processing circuit is further composed of a plurality of comparators 21 to 24 comparing the first and second waveform signals and the first and second comparison voltages respectively and outputting comparison signals and a logical circuit 30 makes an intermediate logical output on the basis of these comparison signals. A switch unit 4 is controlled on the basis of the intermediate logical output from the logical circuit 30, and any of the step-up operation, the step-down operation and the step-up-down operations is conducted. COPYRIGHT: (C)2009,JPO&INPIT
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