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

3.1.2 A Wide VIN/VOUT Capable LLC

To simplify designs for wide input/output voltage applications, IPPC or Input Power Proportional control was introduced at the end of 2023. The real power of IPPC is that it removes the switching frequency from the feedback loop which means for the same power level, you have the same control point.

No IPPCFigure 3-6 No IPPC
With IPPCFigure 3-7 With IPPC

Here you can see with and without IPPC, when in the constant current (CC) phase the switching frequency is 170kHz when the charging power is 373W, but in the constant voltage (CV) phase the switching frequency is 105kHz. What is different is that without IPPC the switching control feedback control voltage is a function of both input power and the switching frequency.

Equation 4. F B = f n P I N , f S W

IPPC removes the impact of the switching frequency leaving it as only a function of input power or

Equation 5. F B = f n P I N