Safety torque off device for interrupting the generation of torque by an elevator installation drive machine supplied by a power supply device

A safety torque off device for interrupting a generation of torque by an elevator installation drive machine supplied by a power supply device, wherein the power supply device includes a power input, a power output, a plurality of power switches connected to the power input and to the power output, and a driver circuit controlling the power switches, wherein the power supply device operates such that an electrical power applied to the power input is at least partially passed on to the power output under control of the driver circuit and the power switches as a function of signals applied by a signal generator device from a plurality of first signal outputs to a plurality of first signal inputs of the driver circuit, the safety torque off device comprising:

• a control input, a plurality of second signal inputs and a plurality of second signal outputs, wherein each of the first signal outputs of the signal generator device is connected to an associated one of the second signal inputs and each the first signal inputs of the driver circuit is connected to an associated one of the second signal outputs;
• wherein the control input is electrically connected to a first control unit and a second control unit, the first control unit being controlled by a control signal applied to the control input to switch first signal transmission switches between the conductive switching state and a non-conductive switching state, and the second control unit being controlled by the control signal applied to the control input to switch second signal transmission switches between the conductive switching state and the non-conductive switching state;
• and
• wherein each of the first and second signal transmission switches is a normally conductive semiconductor switch that, in an absence of a control voltage at a gate terminal thereof, establishes an electrical connection between an associated one of the second signal inputs and a ground potential and, when the control voltage is applied to the gate terminal, interrupts the electrical connection between the associated second signal input and the ground potential, and wherein the first and second control units apply the control voltage to the gate terminals of the first and second signal transmission switches respectively as a function of the control signal applied to the control input.