The safety catch for an electronic short-circuit fuse

摘要

1301030 Protective arrangements KOMBINAT ZENTRONIK VEB 29 Jan 1970 4421/70 Heading H2K A regulating and short circuit protective device for a voltage regulating unit (not shown) comprises a transistor Tr having its emitter and collector electrodes connected across a source of auxiliary voltage +UH, -UH, through respective first and second resistors W5, W7, the resistor W7 providing an input signal to the regulating unit, the base of the transistor being connected to a voltage divider W1 ... W3 and diode Gr, the divider being connected to the auxiliary source -UH through a resistor W6 and the diode being connected to the output - Uaus of the regulating unit, and a capacitor C2 being connected between the auxiliary source -UH and the emitter of the transistor to prevent incorrect operation when a load (indicated at CL) is initially switched on. Normally the transistor Tr is non-conducting, but should a short-circuit occur (as indicated by C1) the base of the transistor is caused to go negative by the auxiliary source -UH. The transistor Tr conducts to control the regulating unit. When switching on the load CL, any initial short-circuiting effect of the load does not cause the transistor to conduct, as the capacitor C2 initially functions to short-circuit the emitter to the auxiliary source -UH, so causing the emitter to be more negative than the base until this capacitor is charged.