Eliminating High-Voltage Pre-Charge Circuits in Electric Vehicles Using Bidirectional DC-DC Converters

Pre-charge circuit ensure the safety of the electric vehicle. During start up, the pre-charge circuits are critical for managing the initial connection between the high voltage battery and the power electronic system in all electric vehicles. Pre-charge circuits typically consist of resistors and contactors that gradually charge the input capacitors of inverters and DC-link systems to prevent sudden inrush currents that could damage components or trigger faults. However, traditional pre-charge solutions present several limitations like increased component count and system complexity, thermal losses due to resistor dissipation, mechanical wear of contactors over time, Slower start-up response, added cost and potential failure points. This paper introduces a novel method to eliminate conventional pre-charge circuits by utilizing bidirectional DC-DC converters to manage the pre-charge function. Through controlled ramp-up of voltage from the low-voltage system to the high-voltage bus, the bidirectional converter replicates the functionality of the pre-charge circuit while reducing system complexity and hardware requirements. The proposed approach is validated through simulation, testing, and controlled experimental scenarios. Key parameters such as inrush current suppression, voltage ramp profile, and system protection behaviour are analysed. Results demonstrate that bidirectional DC-DC converters not only meet the safety and functional requirements of pre-charge circuits but also enhance system reliability, packaging efficiency, and overall powertrain robustness, making them highly suitable for next-generation EV architectures.