Drive-interface for a static electronic switch with controlled "off"

A drive interface for a static electronic switch for insertion between a control stage capable of generating a logical control signal (Sc) including blocking and conducting commands and a static switch (3) capable of controlled current blocking, said static switch being of the blocking transistor type or transistors other than discrete transistors having an applied voltage bias at zero collector current and negatively biased base (V.sub.CEX) higher than the applied open base voltage bias (V.sub.CEO), and wherein said static switch further comprises at least one control electrode (3c) and two power electrodes (3a, 3b) and may assume at least a first conducting state characterized by a slight voltage drop across said power electrodes and a second blocking state characterized by a low leakage current between said power electrodes, said states corresponding to different polarities of said control electrode and changes in said states being caused by a change of polarity on said control electrode, said drive interface comprising:

• a detection circuit (5) for sensing the voltage across said power electrodes and comprising means for emitting a two-state voltage signal (St) as a function of said sensed voltage, one state corresponding to a voltage of substantially zero across said power electrodes and the other state corresponding to a voltage other than zero.
• a drive circuit (6) connected to said detection circuit (5) for receiving said voltage signal (St) from said detection circuit and connected to said control stage (2) for receiving said control signal (Sc) from said control stage and establishing the polarity on said control electrode and including means for carrying out a logical function on said voltage and control signals for applying a two-level polarity signal on said control electrode, one of said levels corresponding to a blocking of said static switch and appearing during an OFF command and/or for the control of the voltage state signal corresponding to a voltage other than zero, and the other of said levels corresponding to the conduction of said static switch and appearing during the conduction state of said control signal and for the voltage signal corresponding to a voltage of substantially zero,
• said polarity on said control electrode corresponding to said blocking state when (a) said control signal (Sc) corresponds to an OFF command and/or (b) the voltage across said power electrodes is other than zero, and
• said polarity on said control electrode corresponding to said conducting state when (c) said control signal (Sc) corresponds to a conduction command or (d) the voltage across said power electrodes is substantially zero,
• said detection circuit further including means (8) for generating a reference voltage (r), said reference voltage being very low relative to the maximum voltage across said power electrodes (3a, 3b), and a comparator (9) connected to said power electrodes and to said generating means for emitting said two-state voltage signal (St) as a function of the relative values of said reference voltage and the voltage across said power electrodes.