| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply which consumes less power at the time of turn-off. SOLUTION: In a switching power supply wherein a field-effect transistor Q1 serially connected to a primary winding 1a of a transformer 1 is on/off- controlled by the output of an auxiliary winding 1b of the transformer 1 and the AC output is obtained at the secondary winding 1c side of the transformer 1, when turning on the field effect transistor Q1 by the output of the auxiliary winding 1b, a switching transistor Q2 connected between the gate and the source of the field-effect transistor Q1 conducts until the output voltage of the auxiliary winding 1b becomes a specified voltage and then becomes a non-conducting state when the output voltage of the auxiliary winding 1b becomes the specified voltage and the output voltage of the auxiliary winding 1b is applied to the gate of the field-effect transistor Q1. By this method, this power supply conducts at a low on-state voltage and does not consume much power and therefore can save power. |
