JAJU732C June   2019  – July 2022

 

  1.   概要
  2.   Resources
  3.   特長
  4.   アプリケーション
  5.   5
  6. 1System Description
    1. 1.1 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Highlighted Products
      1. 2.2.1  UCC21530
      2. 2.2.2  AMC1311
      3. 2.2.3  AMC3302
      4. 2.2.4  AMC3306M05
      5. 2.2.5  LM76003
      6. 2.2.6  LMZ31707
      7. 2.2.7  OPA320
      8. 2.2.8  ISO7721
      9. 2.2.9  SN6501
      10. 2.2.10 SN6505B
      11. 2.2.11 TMP235
      12. 2.2.12 LMT87
      13. 2.2.13 TL431
      14. 2.2.14 LMV762
      15. 2.2.15 TMS320F280049 C2000 MCU
      16. 2.2.16 TMDSCNCD280049C
    3. 2.3 System Design Theory
      1. 2.3.1 Dual Active Bridge Analogy With Power Systems
      2. 2.3.2 Dual-Active Bridge - Switching Sequence
      3. 2.3.3 Dual-Active Bridge - Zero Voltage Switching (ZVS)
      4. 2.3.4 Dual-Active Bridge - Design Considerations
        1. 2.3.4.1 Leakage Inductor
        2. 2.3.4.2 Effect of Inductance on Current
        3. 2.3.4.3 Phase Shift
        4. 2.3.4.4 Capacitor Selection
        5. 2.3.4.5 Soft Switching Range
        6. 2.3.4.6 Switching Frequency
        7. 2.3.4.7 Transformer Selection
        8. 2.3.4.8 SiC MOSFET Selection
      5. 2.3.5 Loss Analysis
        1. 2.3.5.1 Design Equations
        2. 2.3.5.2 SiC MOSFET and Diode Losses
        3. 2.3.5.3 Transformer Losses
        4. 2.3.5.4 Inductor Losses
        5. 2.3.5.5 Gate Driver Losses
        6. 2.3.5.6 Efficiency
        7. 2.3.5.7 Thermal Considerations
  8. 3Circuit Description
    1. 3.1 Power Stage
    2. 3.2 DC Voltage Sensing
      1. 3.2.1 Primary DC Voltage Sensing
      2. 3.2.2 Secondary DC Voltage Sensing
    3. 3.3 Current Sensing
    4. 3.4 Power Architecture
      1. 3.4.1 Auxiliary Power Supply
      2. 3.4.2 Isolated Power Supply for Sense Circuits
    5. 3.5 Gate Driver
      1. 3.5.1 Gate Driver Circuit
      2. 3.5.2 Gate Driver Bias Power Supply
      3. 3.5.3 Gate Driver Discrete Circuits - Short-Circuit Detection and Two Level Turn Off
  9. 4Hardware, Software, Testing Requirements, and Test Results
    1. 4.1 Required Hardware and Software
      1. 4.1.1 Hardware
      2. 4.1.2 Software
        1. 4.1.2.1 Getting Started With Software
        2. 4.1.2.2 Pin Configuration
        3. 4.1.2.3 PWM Configuration
        4. 4.1.2.4 High-Resolution Phase Shift Configuration
        5. 4.1.2.5 ADC Configuration
        6. 4.1.2.6 ISR Structure
    2. 4.2 Test Setup
    3. 4.3 PowerSUITE GUI
    4. 4.4 LABs
      1. 4.4.1 Lab 1
      2. 4.4.2 Lab 2
      3. 4.4.3 Lab 3
      4. 4.4.4 Lab 4
      5. 4.4.5 Lab 5
    5. 4.5 Test Results
      1. 4.5.1 Open-Loop Performance
      2. 4.5.2 Closed-Loop Performance
  10. 5Design Files
    1. 5.1 Schematics
    2. 5.2 Bill of Materials
    3. 5.3 PCB Layout Recommendations
      1. 5.3.1 Layout Prints
    4. 5.4 Altium Project
    5. 5.5 Gerber Files
    6. 5.6 Assembly Drawings
  11. 6Related Documentation
    1. 6.1 Trademarks
  12. 7Terminology
  13. 8About the Author
  14. 9Revision History

2.3.3 Dual-Active Bridge - Zero Voltage Switching (ZVS)

During the transition from interval one to two, there exists a small dead time where the inductor-stored energy discharges the output capacitances of the MOSFETs and holds them close to zero voltage before they are turned on. This phenomenon, where the voltage across the MOSFET is close to zero at turn on, is referred to as zero voltage switching (ZVS). This is a major advantage with this topology, where due to the natural lagging current in one of the bridges, the inductive stored energy causes ZVS of all of the lagging bridge switches and some of the switches of the leading bridge. This depends on the stored inductive energy (EL = 0.5LI2) available to charge and discharge the output capacitances of MOSFETs (EC = 0.5CV2).

When transition happens from interval one to two, the primary side switches Q1 and Q5 continue conduction, whereas in the secondary, Q6 and Q7 turn off and Q5 and Q8 turn on. Initially the voltage across Q6 and Q7 is zero when they are conducting, and Q5 and Q8 block the entire secondary voltage. During dead time, when all of the switches in the secondary are off, the inductor-stored energy circulates current which discharges the capacitor across MOSFETs Q5 and Q8 to zero and charges the capacitor across MOSFETs Q6 and Q7 to the full secondary voltage. The current commutation is shown in Figure 2-11.

GUID-2CBB9DD1-5F1E-4D12-9FBA-215E42EEDAA0-low.gifFigure 2-11 ZVS Transition in Secondary Side - Capacitor

Once the capacitors have been charged and discharged, the current must continue to flow. The current will flow through the diodes D5 and D8, thereby clamping the voltage across MOSFETs Q5 and Q8 to zero as shown in Figure 2-12. During the next interval, MOSFETs Q5 and Q8 are turned on at zero voltage, thereby reducing turn on losses completely. The arrow close to the diode indicates that the diode is conducting and the MOSFET is off.

GUID-E31EB112-A6C7-455C-BC51-0A4B37ABC589-low.gifFigure 2-12 ZVS Transition in Secondary Side - Diode

Similarly, zero voltage switching across the switches of the primary during the transition from interval 2 to 3 is explained in the following section. When transition happens from interval two to three, the secondary side switches Q5 and Q8 continue conduction, whereas in the primary, Q1 and Q4 turn off and Q2 and Q3 turn on. Initially, the voltage across Q1 and Q4 is zero when they are conducting, and Q2 and Q3 block the entire secondary voltage. During dead time when all of the switches in the primary are off, the inductor stored energy circulates current, which discharges the capacitor across MOSFETs Q2 and Q3 to zero and charges the capacitor across MOSFETs Q1 and Q4 to the full primary voltage. The current commutation is shown in Figure 2-13.

GUID-AC01100B-2BAE-40C8-882D-0FD3F986F280-low.gifFigure 2-13 ZVS Transition in Primary Side - Capacitor

Once the capacitors have been charged and discharged, the current must continue to flow. The current will flow through diodes D2 and D3, thereby clamping the voltage across MOSFETs Q2 and Q3 to zero as shown in Figure 2-14. During the next interval, MOSFETs Q2 and Q3 are turned on at zero voltage, thereby reducing turn on losses completely. The arrow close to the diode indicates that the diode is conducting and the MOSFET is off.

GUID-C7750ED3-E2D3-43DB-A9FF-0CA7234073BC-low.gifFigure 2-14 ZVS Transition in Primary Side - Diode