Shunt-foldback voltage source

Claim 1

A programmable power supply having an output terminal adapted for connection to a device under test, the programmable power supply comprising: A. a foldback power supply, having an output port, for providing a predetermined output voltage at its output port until the current drawn by its load reaches a predetermined maximum, the foldback supply reducing both its output voltage and its output current when the predetermined maximum current is exceeded; B. switch means connected between the output port and the output terminal and operable by application of control signals thereto selectively to complete and interrupt electrical connection between the output port and the output terminal; C. a shunt circuit connected in parallel with the power supply and operable by application of control signals thereto to tend to draw more than the predetermined maximum current from the current-limited power supply; and D. a control circuit, connected for application of control signals to the switch means and the shunt circuit, for first applying signals to operate the shunt circuit to tend to draw more than the rated current from the foldback power supply to cause the supply voltage to drop to a low value and for then applying control signals to the switch means to open it to disconnect the foldback supply from any device under test connected to the output terminal.