| 摘要 |
PROBLEM TO BE SOLVED: To provide a DC-DC converter in which switching loss is not increased even in the case of a light load. SOLUTION: In a DC-DC converter for turning an NMOS 36 on by detecting the bottom of a pulsating ringing voltage, turn ON timing is quickened in the case of a light load and the switching loss is increased. Resistance of a variable resistor 46 generating a voltage signal corresponding to the ringing voltage is varied as the time elapses through a time constant circuit 49 and a function converting circuit 50. Since the timing for detecting the fact that the ringing voltage has reached a desired level is shifted at a comparison circuit 47, the NMOS 36 can be turned on at the second bottom of the ringing voltage, for example, and thereby the switching loss is not increased.
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