Abstract: A zero voltage switching circuit for controlling current to a serially arranged load and AC voltage source including first and second photosensitive silicon controlled rectifiers having a gate, anode, and cathode terminals, the anode-cathode terminals being arranged to be connected in inverse parallel across the load and AC voltage source, apparatus for applying input signals to generate light to enable the first and second photosensitive silicon controlled rectifiers, apparatus for providing a voltage range within which the photosensitive silicon controlled rectifiers operate, apparatus for clamping the gate terminals of each of the photosensitive silicon controlled rectifiers to its cathode in the absence of input light signals to the photosensitive silicon controlled rectifiers, and apparatus for opening the circuit between the gate and rectifier of each photosensitive silicon controlled rectifier in the presence of input light signals.

Abstract: In solid state relay circuit including a metal oxide field effect transistor connected for switching current to a load circuit, a latch circuit including first and second transistors connected to monitor a voltage caused by current in the load circuit and to shunt current away from the field effect transistor in response to current overload in the load circuit, the first and second transistors having temperature characteristics such that they turn on in response to different voltages at different temperatures, the improvement including a second means for turning on the latch to shunt current away from the field effect transistor in response to the voltage caused by current in the load circuit, the second apparatus including temperature compensating apparatus for matching the temperature characteristics of the first and second transistors of the latch circuit whereby the latch turns on at the same voltage in the load circuit over the typical operating range of the device.

Abstract: In a solid state relay circuit using a power semiconductor as the output circuit switching device and having protection against current overload and short circuits, an indicator circuit for signaling that overload currents have occurred in the switching device comprising circuitry for sensing that current overload protection has occurred, and switching circuitry responsive to the sensing that current overload protection has occurred for operating a current overload indicator.

Abstract: In a solid state relay circuit including a power semiconductor for switching power to a load circuit and having circuitry for disabling the power semiconductor to protect against current overload or short circuits, such disabling means including a silicon controlled rectifier for short circuiting the input to the power semiconductor, apparatus for sensing the presence of transient voltages in the load circuit, and apparatus for disabling any short circuit caused by the silicon controlled rectifier due to such voltage transients.

Abstract: A solid state relay circuit including a power semiconductor for the switching device, the power semiconductor having gate, source, and drain terminals, the source and drain terminals being adapted to be connected across a load circuit, switching circuitry providing a normally non-conducting path between the gate and source terminals, and circuitry for switching the switching device to a conducting condition in response to the appearance of voltage spikes in the output circuit having a value sufficient to cause the power semiconductor to conduct before the power semiconductor can be caused to conduct.

Abstract: A solid state relay circuit is provided which controls the application of power to multiple loads in a manner which prevents the simultaneous application of power to more than one load. Photovoltaic diode arrays along with phototransistors are employed to control MOSFET output switching devices.

Abstract: A control circuit for protecting a metal oxide semiconductor field-effect power transistor from current overloads is disclosed in one embodiment of the control circuit. A silicon controlled rectifier is used to remove the bias voltage from the MOSFET in the event of a current overload. In another embodiment of the invention a bipolar transistor in combination with a second MOSFET is used to turn off the power MOSFET in the event of a current overload. The voltage appearing across the power MOSFET is used as an indication of a current overload condition.

Abstract: A circuit for controlling one or more light emitting diodes is disclosed. The circuit is designed to supply current to the diodes from an input voltage source in response to a control signal. The circuit provides a predetermined level of current to the diodes which is substantially independent of the magnitude of the input voltage. The circuit also includes a switching function which operates to switch off the diode current when the control signal exceeds a first level of control voltage. When the control signal is reduced below a second level of control voltage, the diode current is switched to the predetermined level of current.

Abstract: An improved zero voltage switching AC relay circuit is disclosed which includes two photo sensitive silicon controlled rectifiers (photo-SCRs) connected in inverse parallel as the active switching elements. The photo-SCRs are triggered into conduction by a light source including two light emitting diodes. Zero voltage switching circuitry is also provided which prevents the photo-SCRs from being triggered into conduction by the light source except when the value of the AC voltage being controlled is within a predetermined limit of zero volts. This is accomplished by using the collector-emitter circuit of a transistor to shunt the gate-cathode circuit of each photo-SCR. A transistor is provided for each photo-SCR, and the bases of the transistor are connected to each other by a single current limiting resistor.