Fast switching circuit for inductive load - has thyristor as load switch controlled by two transistors and diode network

摘要

The switching circuit has the supply voltage of the load generated by a push-pull rectifier and switched via a thyristor between the load and the centre point of the push-pull winding. The voltage used for fast excitation of the load is generated by a rectifier bridge and passed to a capacitor whose positive pole is connected via a pnp transistor to the positive pole of the push-pull rectifier at the same time as the thyristor is turned on and for the duration of turn-on. The negative pole of the capacitor is connected to the thyristor anode via an npn transistor. The fast excitation voltage is applied briefly to turn off the thyristor for de-exciting the load. Current from the load flows back via return diodes to the excitation capacitor.