Method and apparatus for protecting digital output circuits

摘要

This invention relates to testing and protecting an output module (70). The invention provides a method and apparatus for testing an output channel, the output channel comprising a transistor (801,802) having a gate a source and a drain and driving a load (761) with a load voltage and a load current in dependence upon a gate drive signal applied to said gate, the method comprising the steps of: determining a voltage threshold; determining a current threshold; monotonically varying said gate drive signal from a starting value for a predetermined time interval; monitoring the load current; monitoring the load voltage; and in the event that the load voltage reaches the voltage threshold or the load current reaches the current threshold or the predetermined time interval expires, returning the gate drive signal to said starting value.