A novel insulation resistance monitoring device for Hybrid Electric Vehicle

A new type insulation resistance on-line monitor has been designed for hybrid electric vehicle (HEV). It is mainly composed of a proportional circuit and data sampling, processing module. The device detects insulation resistance by sampling DC bus voltage and voltage between positive line and chassis. The voltages sample is controlled by electronically controlled unit (ECU). These voltages are isolated by opto-coupler Isolation amplifier and transmitted to ECU. The value of insulation resistance is calculated in ECU. The hardware circuit, software realization and insulation resistance calculation formula have been given. The device has been tested in laboratory, test results show the device can accurately and instantaneously detect all kinds of insulation condition, and give an alarm when the insulation is destroyed. The device do not need voltage and (or) current sensor, and use a high voltage switch to control sampling. So it reduces the cost and is convenient for engineering realization.