| 摘要 |
<p>A switching power supply comprises first switching circuit (4) for making an input voltage on and off, a transformer (3) having a primary winding (3a) connected in series with the first switching circuit (4), first rectifying and smoothing circuit (7, 9) connected to a secondary winding (3c) of the transformer and a second switching circuit (8) for releasing the output of the rectifying and smoothing circuit (7, 9) back to the secondary winding (3c) of the transformer (3) during the off-period of the first switching circuit. The switching power supply may further comprise a control circuit (10) for controlling on or off the second switching circuit (8) in response to the output of the first rectifying and smoothing circuit. The power supply may alternatively comprise a second rectifying and smoothing circuit (60, 61) connected to additional secondary winding (3f) to control on or off of the first switching circuit. Thus a stabilized switching power supply is provided with lower power loss, higher efficiency and lower noise.</p> |
