| 摘要 |
PROBLEM TO BE SOLVED: To provide a synchronous rectification type and non-isolated type switching power supply device that suppresses both switching loss and electromagnetic noise.SOLUTION: A control circuit for a switch SW1 turns on the switch SW1 when a voltage Vlx of a node LX rises to bring a potential difference across the switch SW1 to a first threshold or less, and turns off the switch SW1 when a first on time passes after the switch SW1 is turned on. The first on time becomes longer as an output voltage is lower than a reference voltage. A control circuit for a switch SW2 turns on the switch SW2 when the voltage Vlx of the node LX drops to bring a potential difference across the switch SW2 to a second threshold or less, and turns off the switch SW2 when the switch SW2 is on and when a reverse current flows through an inductor L1 enough to raise the voltage Vlx of the node LX until the potential difference across the switch SW1 becomes equal to the first threshold or less after the switch SW2 is turned off. |
