Output circuit having electronic overload protection

摘要

The output circuit having electronic overload protection is a universal output stage which is composed of logic or processor circuits, is voltage-controlled by means of the 5 V digital signals, produces output signals of an order of magnitude of 20 to 30 V, and can at the same time cope with current overloads up to 2 A. The essential feature of the invention is that a resistor is connected in series in the emitter-collector circuit of a transistor (T3), in order to sample the magnitude of the output current, as a result of which the majority of the voltage drop takes place on the resistor (R1) and not on the transistor (T3). No forced cooling of the transistor is therefore required, and its life is thus also extended. A further transistor (T2) and a diode (D2) carry out the function of a current limiter. A capacitor (C1) with resistors (R6 and R7) delays the resetting of a flipflop (M) so that the circuit is not unnecessarily disconnected if only a random and brief overload occurs at the output. The signalling with the aid of a light-emitting diode (LD1) indicates the output state of the circuit according to the invention, but has no significant influence on correct operation of the circuit itself. The frequency of the output state sampling, if defects occur, is 2 Hz, which is sufficiently low to avoid unnecessarily loading the circuit. However, the correct operation of the circuit depends on ... Original abstract incomplete. <IMAGE>