A control system (12) for a power supply (14), such as a high voltage power supply, includes a control circuit (16) and a feedback circuit (18, 28, 30). The feedback circuit (18, 28, 30) is configured to produce a feedback signal indicative of the voltage of the power supply output. The control circuit (16) is configured to control the power supply (14) based on the feedback signal and a predetermined voltage value to maintain the output of the power supply (14) at about the predetermined voltage value. A portion of the feedback circuit (18, 28, 30) may be included in an isolation shield (88) to improve the accuracy of the feedback signal.