Current output

A current output apparatus adapted for electrical connection to a load to output an electrical current thereto, comprising:

• a current output terminal for connecting to a first terminal of the load to pass an electrical current thereto;
• a current input terminal for connecting to a second terminal of the load to receive said electrical current returned from the load;
• a voltage regulator operable to supply to the current output terminal an electrical voltage regulated to differ from an electrical voltage applied to the current input terminal by an amount sufficient to cause said electrical current to flow from the current output terminal to the current input terminal via the load;
• wherein the voltage regulator is operable and arranged to supply to the current output terminal an electrical voltage of positive polarity or of negative polarity for supplying said electrical current to a load presenting to the current output terminal a voltage of positive polarity or of negative polarity, respectively;
• and
• a synchronous rectifier arranged to rectify an AC voltage signal supplied by a first transformer winding coupled thereto, and to supply the rectified voltage to the voltage regulator;
• wherein the synchronous rectifier comprises field-effect transistors (FETs) and a control unit arranged to synchronously control the conductivity of the transistors to supply to the voltage regulator a DC electrical voltage of negative polarity.