| 摘要 |
<p>A full-wave bridge rectifier (12) has its input (14) connected directly across a 115 volt RMS alternating current line operating at 60 Hz wherein the output of the bridge provides 120 Hz pulsating direct current at 161 peak volts. A pair of transistors (20 and 30), switching on and off in alternating fashion, continuously apply to a low power requirement load (18) only a leading edge portion and a trailing edge portion of each of the 120 Hz direct current pulses. The resultant direct current voltage, e.g. 11.3 peak volts, across the load (18) is thus substantially reduced to a desirable level as compared to the voltage, 161 peak volts, of the pulsating direct current provided at the line driven bridge output. In another embodiment, the function of the transistors (20 and 30) is provided by a pair of operational amplifiers (50 and 60) which control the switching of a field-effect transistor (70) in series with the load (18). Thus inefficient and bulky inductive elements are unnecessary.</p> |
