| 主权项 |
1. An insulated DC power supply comprising:
a voltage transformer comprising a primary winding, a secondary winding, and an auxiliary winding; a switching device causing current to flow intermittently through the primary winding of the transformer; and a primary-side regulating circuit receiving a voltage proportional to a current flowing through the primary winding of the transformer, and a voltage proportional to a voltage induced in the auxiliary winding of the transformer to generate and output a drive pulse for turning on or off the switching device, the primary-side regulating circuit comprising:
a voltage detector circuit giving ON-timings for the switching device with reference to a voltage across the primary winding of the transformer, the voltage induced in the auxiliary winding, or the voltage proportional to the voltage induced in the auxiliary winding;a current detector circuit giving OFF-timings for the switching device with reference to the voltage proportional to the current flowing through the primary winding of the transformer;an ON/OFF signal generator circuit generating signals for turning on or off the switching device with reference to signals from the current detector circuit and the voltage detector circuit;a first timer circuit starting up in synchronization with the ON timing of the switching device, starting to measure the ON time of the switching device, and then expiring upon lapse of a predetermined primary side maximum ON time; anda second timer circuit starting up upon expiration of the first timer circuit, starting time measurement, and then expiring upon lapse of a predetermined maximum demagnetization time, wherein the switching device is turned off upon expiration of the first timer circuit, and the ON/OFF signal generator circuit does not generate a signal for turn-on of the switching device when the second timer circuit expires. |
