The application of the dynistor diode to off-on controllers

A new semiconductor device, called a Dynistor diode, has been developed which can be used in control circuits to provide high output power with a minimum number of devices. The V-I characteristic of the Dynistor diode is shown. When biased in the reverse direction, the Dynistor blocks the flow of current until the breakdown voltage VB is reached. When the breakdown voltage V
_B
and breakdown current fu are exceeded, a sharp voltage breakdown occurs and the device voltage drops to a very low value. When the Dynistor current is reduced below its sustaining value (IS), breakdown ceases and the device reverts to its blocking condition. When applied to off-on controllers, the Dynistor is used as a power switch in a low-voltage, high-current circuit. A lowpower control circuit, which supplies a voltage in excess of the Dynistor breakdown voltage, controls its switching action. Since the Dynistor turn-on time is less than 0.1 microsecond, either dc or very short pulses can be used for control. When half-wave rectified ac is used for the power source, the device turns off automatically once each cycle. The characteristics of the Dynistor diode which make it particularly suitable as a power switch include high breakdown voltage, low hyperconductive drop, inherent bistable action, short switching time, and high current carrying capacity. Unlike the transistor, the Dynistor diode requires control power only while it is switching and the control power required is determined by the device breakdown characteristics alone, regardless of load current. Since Dynistors have been made which block voltages in excess of 200 volts, circuits can be designed where the power Dynistor switches an output relay at the line potential thereby eliminating the need for a 60-cycle transformer capable of carrying the load current.