SPRADK6 September   2024 TMS320F280039 , TMS320F280039-Q1 , TMS320F280039C , TMS320F280039C-Q1 , TMS320F280049 , TMS320F280049-Q1 , TMS320F280049C , TMS320F280049C-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Challenge of Implementing LLC Control in MCU
    1. 2.1 Frequency Changing Requires Multiple PWM Configuration update
    2. 2.2 No Fixed Timing Relationship Between Control and Switching Frequency
  6. 3Corner Cases and Real-Case Challenges
    1. 3.1 Software Workaround
    2. 3.2 CLB-Based Hardware Workaround
  7. 4Summary
  8. 5References

1 Introduction

With higher requirement of power rating and efficiency in power applications like server and telecom PSU, resonant converters like LLC have become the prioritized option of DC/DC stage in more and more new designs. Comparing with traditional full-bridge topology, LLC is easier to achieve soft switching due to resonant operation, leading to better EMI performance, higher efficiency and less stress on power stage.

Plot of Gain vs. Frequency Figure 1-1 Plot of Gain vs. Frequency

Normally the LLC converter works under variable frequency but fixed duty cycle. The typical gain curve of a LLC converter is shown in the following picture. The converter works near frand adjust switching frequency through the control loop to stabilize the output voltage.