This reference design detects mA-level AC and DC ground fault currents. An auto-oscillation circuit is implemented using a DRV8220 H-bridge that drives the magnetic core in and out of saturation. In addition, an active filter circuit is implemented to identify fault current signal and level.

• Low-cost discrete AC and DC ground fault detection circuit
• Designed to sense fault current thresholds of 6 mA DC, 30 mA_RMS AC based off IEC62752 and IEC62955
• Detection-to-response time < 25 ms (not including relay delay time)
• Adjustable AC and DC trip thresholds via software
• Auto-oscillation feedback circuit can drive different magnetic core materials with minimal changes to hardware
• Active low-pass filter optimized to attenuate auto-oscillation frequency and amplify fault current signal