Switching overlap protection by control gate impedance monitoring
AssigneeWestinghouse Electric Corp.
InventorEric J. Stacey
Life of this patent
Estimating the term…
Abstract
In a power converter switching system, the instantaneous blocking ability of semiconductor switching elements is determined by monitoring the reverse blocking ability of a control junction in each switching device. A gate firing circuit applies negative turn-off drive to the control junction. The control junction impedance is monitored and switch recovery is indicated by a change in the magnitude of the impedance. A switch recovery logic signal is then generated and used to initiate the firing of the next successive switch element. When switches are combined in multipulse groups, the recovery signals may be logically combined to provide proper switching coordination, emergency protection and diagnostic information.
Claims6
Solid state switching circuitry comprising:
- a first solid state switching device having a control electrode connected to a control junction and a main conduction path that passes or blocks current flow in response to control current in said control junction, said main conduction path being connected to switch current between an input terminal and an output terminal;
- a first driving means for selectively applying positive and negative control current through said first device control junction;
- means for monitoring the impedance of said first switching device control junction, said impedance exhibiting a change from a first magnitude to a second magnitude upon completion of the turn-off period of said first switching device following a transition of polarity of control current supplied by said first driving means;
- and
- a second driving means for initiating a turn-on signal for a second solid state switching device in response to said change in impedance of said first device control junction wherein said means for monitoring the impedance of said first device control junction includes a branch circuit including a resistor and a light emitting diode connected in series, said branch circuit being connected across said first device control junction such that said light emitting diode emits light in response to said change in impedance of said first device control junction.
Dependencies are inferred from the claim text.