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

2.2.1 Isolated AC/DC Power Supply Design

The isolated AC/DC power stage is a multiple output winding flyback stage based on the UCC28742 device. The UCC28742 controller provides constant-voltage (CV) using an optical coupler to improve transient response to large-load steps. Constant-current (CC) regulation is accomplished through primary-side regulation (PSR) techniques. This device processes information from the optocoupled feedback and an auxiliary flyback winding for precise high-performance control of the output voltage and current. Figure 2-2 shows the system block diagram for the power supply design of the TIDA-010239 and TIDA-010939. The power supply is separated between both boards to enable the TIDA-010939 to be used from a single 12V supply without the need of the TIDA-010239. Together with the TIDA-010239, the whole system can be supplied by a single or three-phase high-voltage input. The design parameters are shown in Table 2-1.

These are the main components of the power supply:

  • A three-phase input flyback with synchronous rectification supplies three voltages: 12 V (power) and ± 14V (low power)
  • Two buck converters (based on TPS563211) and one dual-LDO (TPS7A3901) take the power from the flyback and supply further 5 V, 3.3 V, and ±12 V on the TIDA-010939
  • Two supercapacitors, 2.5 μF each are connected in series and are charged by means of a 120-mA constant current linear regulator, setting the charging voltage to 7.8 V
  • A boost converter with TPS55330 supplies all voltages as soon as mains power is missing
  • A further 12-V input port on the TIDA-010939, protected against overcurrent and reverse polarity, is managed by the eFuse TPS259470. This way the whole system can be supplied without the need of single or three-phase high-voltage input useful during debug or if the TIDA-010939 is used standalone.
  • An inverting buck-boost converter generates ±14V for the dual-LDO during energy storage discharge, taking power from the regulated 5-V rail located on the TIDA-010939
TIDA-010239 Isolated AC/DC Power Supply Block Diagram Figure 2-2 Isolated AC/DC Power Supply Block Diagram
Table 2-1 Design Parameters
PARAMETER NOTES AND CONDITIONS MIN NOM MAX UNIT
INPUT CHARACTERISTICS
Input voltage,VIN 85 115, 230 460 VRMS
Maximum input current VIN = VIN(min), IOUT = IOUT(max) 0.8 ARMS
Line frequency 47 60, 50 63 Hz
Desired capacitor bulk voltage, VBULK(desired) 85 V
No load input power consumption VIN(min) ≤ VIN≤ VIN(max), IOUT = 0 A 500 mW
OUTPUT CHARACTERISTICS
Output voltage, VOUT1 VIN(min) ≤ VIN≤ VIN(max) 11.4 12 12.6 V
Output current, IOUT1 2.2 A
Output voltage, VOUT2 VIN(min) ≤ VIN≤ VIN(max) 10.5 12 12.1 V
Output current, IOUT2 0.1 A
Output voltage, VOUT3 VIN(min) ≤ VIN≤ VIN(max) –10.5 –12 –12.1 V
Output current, IOUT3 0.1 A
Total output power, POUT 28.8 W
Output voltage regulation Line regulation: VIN(min) ≤ VIN ≤ VIN(max),
IOUT1 ≤ IOUT1(max)		 0.1%
Load regulation: 0 A ≤ IOUT1 ≤ IOUT1(max) 0.2%
Output voltage ripple VIN(min) ≤ VIN≤ VIN(max),
0 A ≤ IOUT1≤ IOUT1(max)		 100 mVpp
Total output overcurrent, IOCC VIN(min) ≤ VIN≤ VIN(max) 2.4 A
Minimum output voltage, CC mode VIN(min) ≤ VIN≤ VIN(max), IOUT = IOCC 5 V
Brown-out protection IOUT = IOUT(max) 49.9 55.9 61.8 VRMS
Transient response overshoot IOUT = IOUT(max) to 0-A load transient 0.2 V
Transient response time IOUT = IOUT(max) to 0-A load transient 5 ms
SYSTEMS CHARACTERISTICS
Switching frequency, fSW 1.2 40 kHz
Average efficiency 25%, 50%, 75%, 100% load average at nominal input voltages 84.8 85.5 86.2 %
Operating temperature 25 °C