This document discloses a power leakage sensor for a circuit, comprising: a power switch controller circuit coupled with at least one power switch for the digital circuit, the power switch controller configured to control the at least one power switch, to monitor power supply of the digital circuit, and to perform the following: a. in response to the detecting that the power supply to the circuit is powered on, output a power-off signal to the at least one power switch; and b. in response to the measured power supply metric falling below a threshold in response to the power-off signal, output a power-on signal to the at least one power switch. The power leakage sensor further comprises a frequency counter circuit configured to count a frequency of executing steps a. and b., the frequency indicating a proportion of power leakage in the digital circuit.