Semiconductor switch

Abstract

There is described a semiconductor switch device having two semiconductor components, the first component receiving drive signals from the second. The first component contains either a single power bipolar switch element for single ended control of the energization of a load or a bridge of such elements enabling energization of a load with different polarities. The switch elements, which may be transistors or darlington multiple transistors, have voltage dropping means connected in the leads to their control bases, so that the drive signals from the second component can be produced by low impedance connection to one or other supply connductor, thereby keeping the power dissipation of the second component to a low value. The voltage dropping means may be a series resistor or a constant current circuit. The first component may have temperature sensitive means, such as a diode, for diverting current from the control base of the or each switching element to terminate its conduction if the temperature of the component becomes too high. The switch device is used in a switching system for a motor vehicle, for example, where central control is required of a plurality of loads at various locations. A central controller transmits coded control signals to local controllers which direct the control signals to the correct switch devices. Status signals representing the functional states of the loads and the outputs of local sensors are sent to the central controller to produce there a corresponding display.