| 摘要 |
<p>In a regulated power supply, particularly a pulse-width-modulated supply, the on-off control is located in the feedback path between the supply output terminal and the pulse-width-modulator. Transformer coupled polling pulses sense both the state of the on-off control and the magnitude of the feedback error signal. A power source 10 is connected through an input filter rectifier 12 to a modulating switch 14 feeding the primary winding of a power transformer 18 whose secondary winding output is fed through a rectifier 20 and filter 22 to an output terminal 24. The voltage at the terminal 24 is fed to a differential amplifier 25 where it is compared with a reference voltage from 26. The output of the amplifier 25 is fed to a variable resistance FET 38 connected in series with an ON-OFF control 40. The FET 38 is coupled to the secondary winding of an isolation transformer 44, whose primary winding is coupled through a transistor switch 42 to an oscillator 30. An output detector 48 responds to changes in the primary winding current due to changes in the secondary winding current as the impedance of the FET 38 changes, and signals a pulse with modulator 16 which controls the pulse width of the switch 14. <IMAGE></p> |
