| 摘要 |
The invention relates to a flyback-type switched-mode power supply operating in continuous mode, comprising (a) a transformer (10) provided with primary and secondary windings (A, B, C) the power being transferred through the transformer from the primary to the secondary, (b) a first switch (SW1) in the primary circuit, the first switch chopping the primary current flowing through the primary winding (A) of the transformer; (c) an adjustment circuit (13) controlling said first switch, the adjustment circuit adjusting the output voltage of the power supply by pulse width modulation by varying the ratio between the lengths of the ON and OFF periods of the switch (SW1), and (d) a rectifying switch (SW2) provided in the secondary, said switch being caused not to conduct at an energy-charge stage when energy is being charged in the transformer (10) and to conduct at an energy-discharge stage when energy is being discharged from the primary to the secondary. To provide a simple and reliable control, an output signal (Up) from the adjustment circuit, which controls said first switch, is functionally connected as a control signal (Ut) for the rectifying switch (SW2) through an inverting means (14) so as to switch the rectifying switch alternately between a conducting and non-conducting state. <IMAGE> |
