| 摘要 |
<p>A power supply (10) of the buck regulator type converting an unfiltered rectified d.c. input voltage 'Vin' into a regulated stepped down d.c. output voltage 'Vout' includes a PWM switching regulator (12), which controls the duty cycle of an N-channel FET power switch (14) in response to a feedback path (48), which has its source (S) connected to a Schottky flyback diode (16) and a LC output filter (30). The regulator (12) includes a 555 timer (68) operating with an RC timing network in a modulated as table mode and has an output lead 'OUT' connected to the gate 'G' of the FET (14) with the source 'S' of the FET (14) serving as the 'ground' for the regulator (12). The feedback path (48) includes a diode (44) in series to a sampling capacitor (46) supplying feedback via a voltage divider (50 and 52) and another diode (54) to the timer (68) allowing the regulator circuit (12) to fly with the FET (14).</p> |
