INSULATION RESISTANCE DETECTION SYSTEM FOR ELECTRIC VEHICLE AND INSULATION RESISTANCE DETECTION METHOD THEREOF

An insulation resistance detection system (1) for an electric vehicle (300) is used to detect a positive insulation resistance (RP) between a positive electrode (200+) of a battery (200) of the electric vehicle (300) and an equipment grounding point (GND), and detect a negative insulation resistance (RN) between a negative electrode (200-) of the battery (200) and the equipment grounding point (GND). The insulation resistance detection system (1) includes a negative detection circuit (10), a positive detection circuit (20), and a control unit (30). The control unit (30) controls the negative detection circuit (10) to be charged to generate a first capacitor voltage (VC1), and controls the positive detection circuit (20) to be charged to generate a second capacitor voltage (VC2). The control unit (30) determines whether the negative insulation resistance (RN) is abnormal according to the first capacitor voltage (VC1) and a battery voltage (VPN) of the battery (200), and determines whether the positive insulation resistance (RP) is abnormal according to the second capacitor voltage (VC2) and the battery voltage (VPN).