SDAA145 October   2025 TPSI31P1-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2System Challenge on DC-Link Capacitor Pre-charge
  6. 3System Approach
    1. 3.1 Isolated Switch Driver
    2. 3.2 Active Pre-charge Controller
    3. 3.3 Discrete High Voltage Buck Design
    4. 3.4 Independent Isolated DCDC Boost Design
    5. 3.5 Integrated Pre-charge Design
      1. 3.5.1 Bidirectional High-Voltage to Low-Voltage (HV-LV) DCDC
      2. 3.5.2 Battery Heater
  7. 4Summary
  8. 5Terminology
  9. 6References

Abstract

In hybrid electric vehicles and electric vehicles (HEV/EV), pre-charging the DC-link capacitor is essential. Traditional pre-charge circuits incorporate costly electromechanical relays (EMR) and substantial high-power resistors, which contradict requirements for high-power density and reduced bill of materials (BOM) cost. This application note presents several alternative pre-charge designs, including isolated switching drivers, active pre-charge controllers, high voltage (HV) buck converters, and isolated DC/DC converters, along with respective control methodologies. These designs demonstrate distinct comparative advantages regarding power density, component costs, and functional safety parameters.