Circuit for alternating current and direct current leakage detection

A circuit for detecting an alternating current (AC) leakage current and a direct current (DC) leakage current, comprising:

• an low dropout regulator (LDO) module, configured to convert an external input power supply voltage into a voltage for detecting a leakage current;
• a frequency division module, configured to divide a frequency of a high-frequency clock signal;
• a logic control module, configured to drive a Metal-Oxide-Semiconductor (MOS) transistor and control switching of different operation modes;
• a MOS transistor driving module, configured to drive an external leakage current detection coil;
• a leakage current detection coil, configured to induce an AC leakage signal, a DC leakage signal, and a leakage current self-inspection signal;
• a sampling resistor, configured to convert a current signal flowing through the leakage current detection coil into a voltage signal;
• a programmable gain amplifier (PGA) module, configured to amplify a sampled signal;
• a gain control module, configured to control a magnification of the PGA module;
• an analog-to-digital conversion (ADC) module, configured to convert conversion of an amplified sampled signal from digital to analog;
• a digital signal process (DSP) module, configured to process the AC leakage signal, the DC leakage signal, and the leakage current self-inspection signal;
• and
• a current limiting module, configured to limit a current flowing through the leakage current detection coil;
• wherein the logic control module is configured to drive the MOS transistor and control switching of different operation modes, during DC leakage current detection, the logic control module controls four MOS transistors M1 to M4 to be turned on cyclically according to a square wave signal with a frequency inputted by a control signal FB;
• during AC leakage current detection, the logic control module controls MOS transistors M5 and M2 to be turned on and MOS transistors M1, M3, M4 and M6 to be turned off according to an active level of a control signal SM;
• and during self-inspection, the MOS transistor M6 is turned on, the MOS transistor M5 is turned off, and the MOS transistors M1 to M4 are turned on cyclically according to an active level of a control signal ZJ, and a leakage self-inspection signal is generated on the sampling resistor by means of inductive shunt;
• wherein the logic control module is further configured to control logic of driving signal g1 to g4 of gates of the MOS transistors is configured to ensure that the MOS transistors M1 and M3 are not turned on simultaneously, and the MOS transistors M2 and M4 are not turned on simultaneously;
• wherein the MOS transistor driving module comprises six MOS transistors comprising MOS transistors M1 to M6, and is configured to drive the leakage current detection coil;
• the logic control module drives the six MOS transistors to be turned on or off;
• wherein during the DC leakage current detection, the MOS transistors M1 to M4 form an H-bridge driving circuit, to generate a positive square wave and a negative square wave for driving the leakage current detection coil, and the MOS transistors M5 and M6 are turned off;
• during the AC leakage current detection, the MOS transistors M2 and M5 are turned on, the MOS transistors M1, M3, M4 and M6 are turned off, and the leakage current detection coil detects an alternating residual current between a neutral wire and a live wire by means of electromagnetic induction, to generate a voltage drop on the sampling resistor R1;
• and during self-inspection, the MOS transistors M1-M4 are turned on cyclically, the MOS transistor M6 is turned on and the MOS transistor M5 is turned off, the leakage current detection coil generates a self-inspection signal by means of inductive shunt to detect whether a leakage current detection link is good.