| 摘要 |
<p>The supply circuit, for an electric razor with a choice of mains voltages, has a blocking oscillator with a transformer whose primary is coupled via a controllable semiconductor switch to the mains supply. The secondary is connected to the load e.g. an electric motor. The semiconductor switch is controlled by a control circuit. The semiconductor switch is turned on by positive feedback but turned off depending upon the current in the primary (nl) and the voltage (U1) of the mains (3,4). The primary current and the mains voltage determine the length of time for which the switch is closed.</p> |
