STDA011 September   2025 UCC25661

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Benefits of GaN In LLC Resonant Converter
    1. 2.1 Higher Efficiency
    2. 2.2 Faster Switching Speeds
    3. 2.3 Reduced Parasitic Capacitances
    4. 2.4 Improved Power Density
    5. 2.5 High Thermal Conductivity
    6. 2.6 Lower Junction Temperatures
  6. 3LLC Resonant Converter
    1. 3.1 The Relationship Between Output Voltage (VOUT) and Switching Frequency (fS) in an LLC Resonant Controller
      1. 3.1.1 The LLC Charging Challenge
      2. 3.1.2 A Wide VIN/VOUT Capable LLC
  7. 4Practical Application of LLC Converters for a Battery Charger Leveraging GaN Switches
    1. 4.1 Requirements and Scope
    2. 4.2 Charging Curve for Lithium-Ion Battery
    3. 4.3 How to Support Wide VOUT Range in an LLC Design for Battery Chargers
    4. 4.4 The Prototype Hardware
  8. 5Summary

3 LLC Resonant Converter

An LLC resonant converter is a frequency-controlled topology (see Figure 3-1). The output voltage is regulated by varying the switching frequency of the inverter stage. The converter uses a resonant tank (series inductor (LR) resonant capacitor (CR) and a magnetizing inductance (LM) ) that filters the switching waveform and transfer energy to the output.

In this section, a 5S battery charger that support wide Output Voltage (VOUT) = 15,0 – 28,0V is used to explain how the switching frequency changes with VOUT and why GaN FETs are a good alternative to use in this application to reach high efficiency.

LLC Converter Circuit Figure 3-1 LLC Converter Circuit