A switch detection circuit, comprising a controller, a first DC isolation module, a second DC isolation module and a signal conditioning module; wherein an output end of the controller is configured to be connected to a first end of an external switch via the first DC isolation module, a control end of the signal conditioning module is configured to be connected to a second end of the external switch via the second DC isolation module, and an output end of the signal conditioning module is connected to an input end of the controller; the output end of the controller is configured to output a pulse signal, and transmit the pulse signal to the second DC isolation module via the first DC isolation module and the external switch; characterized in that the signal conditioning module is configured to output a feedback signal to the input end of the controller according to an electrical signal output by the second DC isolation module, and the controller is also configured to count the received feedback signal to obtain a count value, and detect a working state of the external switch according to the count value; wherein the first DC isolation module is a capacitor C1, the second DC isolation module is a capacitor C2 and the switch detection circuit further comprises a resistor R1 and a resistor R3; wherein a first end of the resistor R1 is connected to the output end of the controller, and a second end of the resistor R1 is connected to the first end of the capacitor C1; a first end of the resistor R3 is connected to the second end of the capacitor C2, and a second end of the resistor R3 is configured to be grounded; wherein a voltage detection end of the controller is connected to the second end of the resistor R1; and the controller is configured to detect a sampled voltage of the second end of the resistor R1 at rising edge of the pulse signal, and determine whether the external switch has a fault according to the sampled voltage and the count value. wherein an output end of the controller is configured to be connected to a first end of an external switch via the first DC isolation module, a control end of the signal conditioning module is configured to be connected to a second end of the external switch via the second DC isolation module, and an output end of the signal conditioning module is connected to an input end of the controller; the output end of the controller is configured to output a pulse signal, and transmit the pulse signal to the second DC isolation module via the first DC isolation module and the external switch; characterized in that the signal conditioning module is configured to output a feedback signal to the input end of the controller according to an electrical signal output by the second DC isolation module, and the controller is also configured to count the received feedback signal to obtain a count value, and detect a working state of the external switch according to the count value; wherein the first DC isolation module is a capacitor C1, the second DC isolation module is a capacitor C2 and the switch detection circuit further comprises a resistor R1 and a resistor R3; wherein a first end of the resistor R1 is connected to the output end of the controller, and a second end of the resistor R1 is connected to the first end of the capacitor C1; a first end of the resistor R3 is connected to the second end of the capacitor C2, and a second end of the resistor R3 is configured to be grounded; wherein a voltage detection end of the controller is connected to the second end of the resistor R1; and the controller is configured to detect a sampled voltage of the second end of the resistor R1 at rising edge of the pulse signal, and determine whether the external switch has a fault according to the sampled voltage and the count value.