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

1 Introduction

Power supply designed for outdoor use need to excel in their thermal performance to give headroom enough to handle high environment temperatures. Outdoor power supplies operate often in higher temperatures than normal indoor 25°C. One way to design for high thermal performance is to aim for the highest possible efficiency. Small size is an important factor to minimize the environmental foot print in package size and weight. It is also a selling factor that appeals the customers. TIs new GaN FETs is a new technology that help designers to reach higher efficiency in their AC/DC converter designs.

LLC resonant controllers have become more and more popular in power electronics because this topology can meet the demanding performance requirements that modern power supply designs have. LLC resonant controllers reduce switching loss through zero-voltage switching (ZVS)

LLC controller traditionally are optimized to run at approximately 100kHz with the limitation being able to detect the switch node slew rate. TI’s recent series of LLC controllers the UCC2566x family breaks the speed barrier and allows resonant operation up to 750kHz allowing applications to utilize GaN FETs fast switching capacity and support ha larger output voltage range.

LLC resonant controllers used in charging applications is extra challenging due to the required dynamic output voltage range. The broad output voltage regulation impacts the switching frequency of the LLC stage.