SLUAAH1 December   2021 UCC24624

 

  1.   Trademarks
  2. 1Introduction
    1. 1.1 LLC Resonant Converter
    2. 1.2 Synchronous Rectification (SR)
      1. 1.2.1 Diode Rectification and Synchronous Rectification
      2. 1.2.2 Power Loss for Synchronous Rectification
      3. 1.2.3 UCC24624 Introduction
  3. 2Configurations of Secondary Rectifier Circuit using UCC24624
    1. 2.1 Typical Configuration
    2. 2.2 Single SR Controller with Paralleled MOSFETs Configuration
    3. 2.3 Dual SR Controllers with Paralleled MOSFETs Configuration
    4. 2.4 Multi SR Controllers with Matrix Transformer Configuration
  4. 3Summary
  5. 4References

2.3 Dual SR Controllers with Paralleled MOSFETs Configuration

The SR controller has limited capability to drive paralleled MOSFETs at higher switching frequency, due to its packaging and thermal constrain. To improve the thermal management of the SR controller UCC24624, a new structure of using a dual SR controller is proposed.

The new structure uses one UCC24624 to drive the SR on each side of a center-tapped transformer. The benefit of this structure is UCC24624 just needs to drive one side of the FETs which could reduce the power dissipation to half. Figure 2-3 shows the proposed structure.

Dual SR controller implementation can effectively divide total driving loss into two separate controllers and it can make each UCC24624 operate within its thermal limit. According to Equation 9, each UCC24624 just needs to handle half of the total driving loss as Equation 11.

Equation 11. PGATE ↑↓=12* 2 * Qg* Vgs* fsw↑* N 

Noted, the introduced additional SR controller UCC24624 increases the static power loss. However, it can be neglected comparing with the overall system power level.

GUID-20211217-SS0I-SLLZ-XXQC-HDQJZRBCGDRB-low.pngFigure 2-3 Dual UCC24624 Application Schematic