Power switching control circuit with enhanced turn-off drive
AssigneeNorth Electric Company
InventorPatrick L. Hunter
Life of this patent
Estimating the term…
Abstract
A transformer-coupled power switching device control arrangement utilizes an active feedback energy source connected to the primary of the coupling transformer to enhance the turn-off drive to the power switching device. The active feedback energy source produces an output directly dependent upon the magnitude of the power switching device output current and independent of the duration of said output current. When the output current drops to zero, the active feedback source is disabled, and a bias network is connected to the transformer primary. The bias network maintains a reverse voltage at the control electrode of the power switching device and establishes a bias current through the primary suitable for resetting the transformer core flux.
Claims7
A circuit for controlling the conduction state of a power switching device delivering power to a load means, said device including a control electrode and first and second output electrodes, said load means having a first and second terminal, said first terminal being coupled to said first output electrode, said control circuit comprising;
- transformer means including a primary winding, a first secondary winding connected between said control electrode and said second output electrode, a second secondary winding connected between said second output electrode and said second terminal of said load means, said first and second secondary windings mutually poled to provide regenerative current coupling therebetween,
- device turn-off control means,
- current sensing means for proportionately coupling the current flowing in said load means to an input of said device turn-off control means, and
- control switch means, operative in a first switching state to couple said device turn-off control means to said primary winding, thereby enabling said device turn-off control means, in conjunction with said transformer means, to render said power switching device non-conductive, said control switch means further operative in a second switching state to render, in conjunction with said transformer means, said power switching device conductive by substantially isolating said device turn-off control means from said primary winding.
Dependencies are inferred from the claim text.