| 摘要 |
PROBLEM TO BE SOLVED: To reduce a conduction loss generated on an energizing path of a switching element by making it possible to control the driving timing of the switching element that is turned on after the supply of a current from a DC power supply to a coil is cut off, without providing a resistor on the energizing path of the switching element, in a DC-DC converter. SOLUTION: In the DC-DC converter 10, the timing to turn on a MOSFET 12 provided on a charging path B to a capacitor C2 is so controlled that a conduction loss when a current is caused to flow only by a parasitic diode D2 may be larger than the one when a current is caused to flow by turning the MOSFET 12 on. For this purpose, a control circuit 20 calculates a ripple current that indicates an amount of change in coil current and calculates a peak current from the ripple current and an input current, and then calculates a duration required until the peak current drops to a predetermined switching current to find a switching duration to the time when the MOSFET 12 is turned on after a MOSFET 11 is turned off. COPYRIGHT: (C)2011,JPO&INPIT |
