A quick discharge circuit for a pacer's nuclear power supply. A pacer capable of implantation within the body of a patient and capable of being powered by at least one nuclear battery is disclosed. Voltage from a single nuclear battery is increased by a factor of about 25 to 30 in order to provide a voltage level adequate to power pacer circuitry. A restartable DC-DC converter is used for this purpose. But if the converter malfunctions the load voltage must be reduced below a certain level for the converter to be automatically restarted. The present invention relates to means for reducing the time from converter malfunction to resumption of converter operation in order to reduce the corresponding inoperative pacer time period.