TIDUFC8 July   2025

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Introduction
      2. 2.2.2 Basic Operation Principles and ZVS Requirements
    3. 2.3 Highlighted Products
      1. 2.3.1 UCC27288
      2. 2.3.2 UCC23513
      3. 2.3.3 TMS320F2800137
      4. 2.3.4 TLV9062
      5. 2.3.5 INA181
      6. 2.3.6 TPSM861252
      7. 2.3.7 AMC0311R
  9. 3System Design Theory
    1. 3.1 Design Theory
      1. 3.1.1 Resonant Tank Design
      2. 3.1.2 Full-Range ZVS Realization
      3. 3.1.3 Total Control Algorithm
      4. 3.1.4 Resonant Tank RMS Current Analysis
    2. 3.2 Hardware Design Theory
      1. 3.2.1 Resonant Capacitors
      2. 3.2.2 Power Stage
      3. 3.2.3 Voltage Sensing
      4. 3.2.4 Current Sensing
  10. 4Hardware, Software, Testing Requirements, and Test Results
    1. 4.1 Hardware Requirements
    2. 4.2 Software Requirements
      1. 4.2.1 Simulation
    3. 4.3 Test Setup
    4. 4.4 Test Results
  11. 5Design and Documentation Support
    1. 5.1 Design Files
      1. 5.1.1 Schematics
      2. 5.1.2 BOM
      3. 5.1.3 PCB Layout Recommendations
        1. 5.1.3.1 Layout Prints
    2. 5.2 Tools
    3. 5.3 Documentation Support
    4. 5.4 Support Resources
    5. 5.5 Trademarks
  12. 6About the Author

3.1.2 Full-Range ZVS Realization

This section discusses how to achieve a full-range of ZVS under this DBSRC, related content is now filed for a U.S. patent.

Figure 3-1 and Figure 3-2 provide separate topology schematics and waveforms. In Figure 3-2, θ is the phase angle between Q1 and Q3. According to the analysis in the previous section, to achieve the zero voltage opening of the four switches on the primary and secondary side, t1 must be in the range of 0θ.


TIDA-010966 Topology Schematics

Figure 3-1 Topology Schematics

TIDA-010966 Topology Waveforms

Figure 3-2 Topology Waveforms

Conventional single-phase-shift (SPS) control, as a single-degree-of-freedom control, θ is often used to control power transmission, so this is difficult to make sure that the soft-switching implementation conditions can be met in the full range. Based on this, another degree of freedom, switching frequency, is introduced into this design to provide the realization of a full range of soft switching, which is analyzed in detail in the rest of this topic.

Figure 3-3 shows the bridge voltage VA, VB and resonant current i_res, which is analyzed using the fundamental harmonic analysis (FHA) method, that is, only the fundamental waves of VA and VB are analyzed and normalized. After normalization, the expressions for VA and VB are respectively:

Equation 2. vA_pu(t)=4πsinωt
Equation 3. vB_pu(t)=4Mπsinωt-θ

where

  • M = VBattery / nVbus = voltage gain
  • Resonant current = Equation 4
Equation 4. ires_pu(t)=vA_pu(t)-vB_pu(t)Xres

where

  • Xres is resonant tank impedance

In Figure 3-2, ires_pu(t1) = 0. From the previously discussed analysis, to make sure all switches achieve zero voltage switching, be sure the t1 value is as expressed in Equation 5.

Equation 5. 0<t1<θ

After considering the accuracy of the FHA and the margin to achieve the ZVS, let t1 = 1/2θ; therefore, Equation 6 is obtained.

Equation 6. ires_pu(t1)=ires_pu(θ2)=0

TIDA-010966 Bridge Voltage Resonant Current

Figure 3-3 Bridge Voltage Resonant Current

Figure 3-3 shows the resonant tank is LC series resonant, so placing the switching frequency at a frequency greater than the resonant frequency fr can make the resonant tank located in the inductive region, so the resonant voltage vres is 90° ahead of the current ires, that is, Equation 7.

Equation 7. vres_pu(θ2+π2)=0

Because vres_pu(t) = vA_pu(t) – vB_pu(t), Equation 8 is true.

Equation 8. vA_pu(θ2+π2)-vB_pu(θ2+π2)=0

From Equation 8, solve θ;

Equation 9. θ=2·arctan(1M)

By doing this, make sure there is enough current to achieve ZVS for switches in both primary and secondary sides.