| 摘要 |
<p>The invention relates to a circuit for protecting switching regulator, capable of automatically stopping the switching operation of the switching regulator on occurring of an abnormality and automatically resuming the switching operation on recovering to the normal state. A voltage is induced in the secondary winding (22) of a transformer (20) by the operation of a field-effect transistor (30). The voltage is then rectified and smoothed to produce a secondary side output voltage. The difference between the output voltage and a reference voltage is fed back from an error detecting circuit (90) to a pulse width control unit (41) so as to maintain the output voltage constant. In case of abnormality, i.e., too high or low a voltage or too large or small a current of the primary winding (21), an abnormality detecting circuit continues to send abnormality detection signals (S1) as long as the abnormality exists. In accordance with these signals (S1), a re-triggerable timer sends a stop signal (S2) to an AND circuit (42) to stop the switching operation of the transistor (30). On recovering to the normal condition, the switching operation of the transistor (30) is automatically resumed after a predetermined period of time has passed from the time of extinction of the stop signals (S2).</p> |
