TIDUF04A December   2022  – December 2025

1.   1
2.   Description
3.   Resources
4.   Features
5.   Applications
6.   6
7. 1System Description
   1.     8
   2. 1.1 EV Charging Station Challenges
      1. 1.1.1 Efficient Relay and Contactor Drive
      2. 1.1.2 Contact Weld Detection
   3. 1.2 Key System Specifications
8. 2System Overview
   1. 2.1 Block Diagram
   2. 2.2 Design Considerations
      1. 2.2.1 Isolated AC/DC Power Supply Design
         1. 2.2.1.1  Input Bulk Capacitance and Minimum Bulk Voltage
         2. 2.2.1.2  Transformer Turns-Ratio, Primary Inductance, and Primary Peak Current
         3. 2.2.1.3  Transformer Parameter Calculations: Primary and Secondary RMS Currents
         4. 2.2.1.4  Main Switching Power MOSFET Selection
         5. 2.2.1.5  Rectifying Diode Selection
         6. 2.2.1.6  Output Capacitor Selection
         7. 2.2.1.7  Capacitance on VDD Pin
         8. 2.2.1.8  Open-loop Voltage Regulation Versus Pin Resistor Divider, Line Compensation Resistor
         9. 2.2.1.9  Feedback Elements
         10. 2.2.1.10 Backup Power Supply
         11. 2.2.1.11 Supercapacitor Selection
         12. 2.2.1.12 Supercapacitor Charger Design
      2. 2.2.2 Relay Drive and Weld Detect
   3. 2.3 Highlighted Products
      1. 2.3.1 UCC28742
      2. 2.3.2 DRV8220
      3. 2.3.3 ATL431
      4. 2.3.4 TL431
      5. 2.3.5 TPS55330
      6. 2.3.6 TPS259470
      7. 2.3.7 TL7705A
9. 3Hardware, Testing Requirements, and Test Results
   1. 3.1 Hardware Requirements
   2. 3.2 Test Requirements
      1. 3.2.1 Power Supply Test Setup
      2. 3.2.2 Weld Detect Test Setup
   3. 3.3 Test Results
      1. 3.3.1 Isolated AC/DC Power Supply Based on UCC28742
         1. 3.3.1.1 Efficiency and Output Voltage Cross Regulation
         2. 3.3.1.2 Output Voltage Ripple Waveforms
         3. 3.3.1.3 Start, Shutdown, Backup Power, and Transient Response Waveforms
         4. 3.3.1.4 Thermal Performance
      2. 3.3.2 DRV8220-Based Relay Drive
      3. 3.3.3 Isolated Line Voltage Sensing
10. 4Design and Documentation Support
    1. 4.1 Design Files
       1. 4.1.1 Schematics
       2. 4.1.2 Bill of Materials
    2. 4.2 Documentation Support
    3. 4.3 Support Resources
    4. 4.4 Trademarks
11. 5About the Author
12. 6Revision History