| 摘要 |
<p>A DC power switching circuit connecting a load to a DC power source while suppressing arcing across a relay in the network. A normally open relay has its energizing coil connected to the control input of the circuit, the opposite end of the coil being connected to the gate of a silicon controlled rectifier. The SCR has its principal current conducting path connected between the load and the DC power source, for conducting current between the load and the power source during a first delay interval, thereby reducing the potential difference between the contacts of the relay so as to prevent its arcing during the closure of the contacts. An FET device has its principal current conducting path connected between the load and the DC power source and has its gate connected to a timer. The timer has a control input connected to the control input of the circuit so that it turns on the FET for a duration of a second delay interval in response to an off signal at the control input for the circuit so that the relay contacts are shunted while they are opening from a closed state, thereby preventing arcing across the contacts. In this manner, the relay is protected from arcing both on opening and closing of its contacts.</p> |
