| 摘要 |
<p>The circuit is applicable to a supply with a transistor switching the prim. side of a transformer supplied with rectified mains voltage. The presence of a regulatory control signal is detected by a pulse-shaping circuit (74) and flip-flop (89) which inhibit a very low-frequency oscillator (82) from establishing a succession of periodic cycles. A high-frequency oscillator (64) produces square waves for a pulse duration modulator (78). A comparator (88) allows bursts of chopping signal during a first phase only of each VLF cycle whose duration lies between the periods of the HF and VLF oscillators.</p> |
