Fault detection circuit

The utility model discloses a fault detection circuit for residual current formula electric fire monitoring detector's body of detector, the detector still includes the mutual -inductor, fault detection circuit include with body of detector's sub circuit that the input number is equal and test output circuit, every the sub circuit includes test switch circuit and back pressure protection circuit, the test switch circuit connection test current input reaches the input of back pressure protection circuit switches on or breaks off route between the input of test current input and back pressure protection circuit, the output of back pressure protection circuit is connected body of detector's corresponding input, test output circuit's input is connected body of detector's leakage detection output, test output circuit's output fault detection result. When fault detection circuit switches on at the route between test current input and the back pressure protection circuit, can export the fault detection result via te