High-Voltage Inrush Current Limiter Purpose: To limit the surge current while first powering a power converter device with bulk capacitor as the load. Problem: While providing input power to a 400V DC-DC converter with 6000 uF capacitance on the input side, the fuse of the driving power supply was blowing because of huge surge current drawn. Damage to the power supply was also a concern. Figure 1: Experimental MOSFET based (in linear range) current limiter Solution Idea and Experiment: To achieve in-rush current limit, employed the following circuit, which is based on an Application Note by Motorola Semiconductor [1] . Result: 1) The prototype circuit worked reasonably well for bridge rectified Power Supply (Oscilloscope traces shown in Figure 4 below). 2) However, the switching MOSFET had several initial failures when the Power Supply was a switched mode PFC . It is suspected that the excessive amount of EMI generated by the PFC was making the MOSFET fail. The high operating