| 摘要 |
<p>1284964 Overvoltage protection M & T CHEMICALS Inc 6 March 1970 [7 March 1969] 10812/70 Heading H2H [Also in Division H3] A device for protecting circuitry against voltage transients comprises a semiconductor gate controlled rectifier SCR1, diodes D1-DN for providing a bias potential for the rectifier and a series circuit including a resistance R2 and a Zener diode ZNR1 connected to the gate electrode of the rectifier. When a high voltage transient appears across terminals 28, 30, the Zener diode conducts and the potential across the resistor R2 triggers the rectifier SCR1 so that the voltage between the terminals 28, 30 is clamped at the sum of the voltage drops across the diodes D1-DN and the rectifier SCR1. As the transient voltage reduces, the rectifier SCR1 returns to its non conducting state. In modifications, capacitors are connected across the diodes D1-DN and/or the rectifier SCR1 for reducing the effects of the relatively slow switching times of the diodes, for preventing the switching on of the rectifier in the absence of triggering voltages and for preventing high rise time transients, which do not exceed a threshold voltage, from triggering the rectifier. The device may also be used with alternating voltages by connecting it in a full wave diode bridge rectifying circuit or by using discs and a triac in place of the diodes and the rectifier SCR1.</p> |
