Rate of change of current limitation circuit for transistor - has load current premagnetised saturable choke which is unsaturated when freewheeling diode current is zero

摘要

The rate of change of current in an h.v. transistor operating at a high frequency can be limited by including a saturable choke (Lb) which is magnetically biased by the load current. This bias is arranged so that the choke is unsaturated when the current through the freewheel diode (F) across the load reaches zero. The choke (Lb) may be additional to the normal limiting choke (La). The operation of the load current biased choke is to reduce the transient voltages on the diode. As the additional choke acts to protect the diode the latter need no longer have an RC snubber circuit in parallel and thus the efficiency of the circuit is improved.