Electronic fuse device for semiconductor switches as protection against overcurrent

摘要

To protect semiconductor switches, an electronic overcurrent protection device is specified which monitors the current of the semiconductor switch to be protected by means of a detector and, in the case of an overcurrent, instantaneously commutates the switch current to a parallel branch by opening a protection switch. For this purpose, the cathode of the protection switch is automatically brought to a negative potential by means of a peak-value rectification and repolarisation of the voltage dropped across the semiconductor switch. The charging process of a quenching capacitor, which starts when the fuse is operated, which capacitor is also a component of the negative bias voltage generation at the cathode of the protection switch, produces an automatic quenching of the latter as a result of which, at the same time, the overcurrent in the circuit is disconnected. Compared with the known protection devices for semiconductor switches, this invention provides the following essential advantages: - protection of the semiconductor switch independently of the structure of the circuit, - no additional current rise limiting measures are required for the fault case, - the semiconductor switch can be loaded with the rated currents without risk, without restriction by the design of the fuse device; even when the maximum disconnectable current is only slightly above the rated current. <IMAGE>