Design and experimental verification of a real-time insulation monitoring module for electric vehicle high-voltage systems

Maintaining an adequate insulation level between the high-voltage system and the vehicle chassis is important for both user safety and the reliability of electronic equipment in electric vehicles. This thesis presents the design of an insulation test device intended to evaluate the insulation condition of a 124 V DC high-voltage line and to provide a warning under critical conditions. In the proposed system, the high-voltage and low-voltage sections are separated by a Flyback converter and an optocoupler-based galvanic isolation structure. The condition information from the high-voltage side is transferred to the low-voltage decision stage through the Q3 PC817 optocoupler without establishing a direct electrical connection. The isolated signal is evaluated by an LM358 comparator according to the reference level adjusted by the R13 trimpot. When an alarm condition occurs, the DS1 LED and LS1 buzzer are activated through the Q4 driver stage. In addition, the physical separation between the high- and low-voltage sections is supported by an isolation slot incorporated into the PCB design. In this study, the galvanic isolation provided within the device and the insulation resistance between the high-voltage line and the vehicle chassis are considered as two distinct concepts. The resulting design combines safe transfer of insulation-related information, threshold-based evaluation, and visual-audible warning within a single hardware structure. However, detailed experimental validation is still required to determine the exact alarm thresholds and to assess compliance with relevant automotive standards.