| 摘要 |
A switching control IC (81) conducts an on-off control of a first switching element (Q1). A second switching control circuit (61) is installed between a high-side driving winding (nb2) of a transformer (T) and a second switching element (Q2). The second switching control circuit (61) discharges electricity from a capacitor (Cb2) in the negative direction with a constant current, while the first switching element (Q1) is ON, and charges the capacitor (Cb2) in the positive direction with a constant current, after the second switching element (Q2) has turned ON. A transistor (Q3) controls the ON period of the second switching element (Q2) so that the ratio of the ON period of the second switching element (Q2) with respect to the ON period of the first switching element (Q1) will always be nearly constant, in accordance with the ratio of the charging current value with respect to the discharging current value. |
