A circuit interrupter includes a first electrical conductor, a second electrical conductor, separable contacts, an operating mechanism configured to open and close the separable contacts, and a trip circuit including a trip actuator configured to cooperate with the operating mechanism to trip open the separable contacts. The circuit interrupter also includes a ground fault detection circuit configured to sense a difference between currents through the first and second electrical conductors and to output an output signal based on the sensed difference, a power supply configured to convert alternating current power from the first and second electrical conductors to a direct current power, and a processor configured to receive the direct current power and the output signal. The processor is also configured to determine whether a characteristic of the power supply is present in the output signal and to control the trip circuit based on the determination.