INSULATION IMPEDANCE DETECTION CIRCUIT FOR ON-BOARD CHARGER AND INSULATION IMPEDANCE DETECTION METHOD

Disclosed is an insulation impedance detection circuit (100) for an on-board charger (200) and an insulation impedance detection method (600). The insulation impedance detection circuit (100) comprises a voltage division circuit (10), a biasing circuit (20), an impedance matching circuit (30), a voltage sampling circuit (40) and a controller (50). Terminals of the voltage division circuit (10) are connected to a first AC terminal and a second AC terminal of the on-board charger (200) respectively, and are connected selectively to a first terminal of the impedance matching circuit (30) via a switch (K1). A second terminal of the impedance matching circuit (30) is connected to a first terminal of the biasing circuit (20), a second terminal of the biasing circuit (20) is grounded, and a third terminal of the impedance matching circuit (30) is connected to an input terminal of the voltage sampling circuit (40). An output terminal of the voltage sampling circuit (40) is connected to the controller (50) for outputting an insulation impedance detection signal (Vm) to the controller (50). The controller (50) is configured to determine whether there is an insulation impedance abnormity or not depending on the insulation impedance detection signal (Vm).