| 摘要 |
The invention relates to a device for protecting an integrated circuit against overload and short circuit currents. The integrated circuit functions such that it is alternatively switched to an ON or an OFF state, and when in the ON state a supply current (IM) is amplified by a Darlington - connected transistor step (Q20,Q21) and is supplied to the output (OUT) of the circuit across a load resistor (RLOAD). For an OFF state of the integrated circuit no current is led to the output (OUT). The device in accordance with the invention is a protective circuit (S) comprising a detection resistor (RSENSE) connected in series with said load resistance (RLOAD), a differential step (D) for sensing a voltage (VSENSE) across the detection resistor (RSENSE) and a thyristor (T). Short circuit or overload on the output (OUT) causes an overcurrent to pass through said transistor step (Q20,Q21) and through the detection resistor. The increasing voltage (VSENSE) across the detection resistor due to the overcurrent is sensed by the differential step (D) which thus energises the thyristor (T) so that the supply current (IM) is taken through the thyristor (T) instead of through the transistor step (Q20,Q21). The transistors (Q20,Q21) are thus pinched off, resulting in that the overcurrent is very quickly extinguished. The integrated circuit may be a final step in a semi-conductor relay, for example. |
