Semiconductor switching element drive circuit

摘要

A semiconductor switching element drive circuit includes a semiconductor that passes main current between first and second terminals when voltage is imposed to a gate terminal, and an over current protection circuit that decreases the main current when the main current is judged to become over current for a certain period when exceeding a predetermined current value when current value or voltage value proportional to an amplitude of the main current exceeds a threshold value. The circuit also includes a short circuit protection circuit that decreases gate voltage imposed to the gate terminal earlier than a fall of the main current produced by the over current protection circuit when the main current becomes larger than the over current in a period shorter than the certain period, and a threshold value change circuit that decreases a threshold value when the short circuit protection circuit decreases the main current.

主权项

1. A semiconductor switching element drive circuit comprising:
a semiconductor that passes main current between a first terminal and a second terminal thereof when voltage is imposed to a gate terminal thereof; an over current protection circuit that judges that the main current is judged to become over current exceeding a predetermined current value for a certain period when one of current value and voltage value proportional to an amplitude of the main current exceeds a threshold value, and then the over current protection circuit decreasing the main current; a short circuit protection circuit that decreases the gate voltage imposed to the gate terminal earlier than a fall of the main current produced by the over current protection circuit; and a threshold value change circuit that decreases the threshold value when the short circuit protection circuit is activated to decrease the main current, wherein the threshold value change circuit includes:
a plurality of resistances that divide the gate voltage to obtain the over current threshold value voltage; anda first comparator that compares the over current threshold value voltage to sense voltage proportional to the main current to output an output signal for activating the over current protection circuit when the sense voltage exceeds the threshold value voltage and for prohibiting an action of the over current protection circuit when the sense voltage is lower than the over current threshold value voltage.