| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply, preventing a cost increase and efficiently controlling switching two switching elements according to the variation of an input voltage.SOLUTION: A low-side switching element Q1 is connected in series with a primary winding np. A high-side switching element Q2 and the primary winding np form a closed loop. The high-side switching element Q2 is switched on by the application of a voltage induced at a high-side drive winding nb2. A transistor Q3, which is switched on and off according to the charge voltage of a capacitor C2 charged by the voltage induced at the high-side drive winding nb2, is connected to the gate terminal of the high-side switching element Q2. When the capacitor C2 is charged to switch on the transistor Q3, the high-side switching element Q2 is switched off. During the ON period of the low-side switching element Q1, the capacitor C2 is discharged by the voltage induced at the high-side drive winding nb2. |
