TIDUF63 December   2023

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 PV or Battery Input With DC/DC Converter
    2. 1.2 Isolation and CLLLC Converter
    3. 1.3 DC/AC Converter
    4. 1.4 Key System Specifications
  8. 2System Design Theory
    1. 2.1 Boost Converter Design
    2. 2.2 MPPT Operation
    3. 2.3 CLLLC Converter Design
      1. 2.3.1 Achieving Zero Voltage Switching (ZVS)
      2. 2.3.2 Resonant Tank Design
    4. 2.4 DC/AC Converter Design
  9. 3System Overview
    1. 3.1 Block Diagram
    2. 3.2 Design Considerations
      1. 3.2.1 DC/DC Converter
        1. 3.2.1.1 Input Current and Voltage Senses and MPPT
        2. 3.2.1.2 Inrush Current Limit
      2. 3.2.2 CLLLC Converter
        1. 3.2.2.1 Low-Voltage Side
        2. 3.2.2.2 High-Voltage Side
      3. 3.2.3 DC/AC Converter
        1. 3.2.3.1 Active Components Selection
          1. 3.2.3.1.1 High-Frequency FETs: GaN FETs
          2. 3.2.3.1.2 Isolated Power Supply
          3. 3.2.3.1.3 Low-Frequency FETs
        2. 3.2.3.2 Passive Components Selection
          1. 3.2.3.2.1 Boost Inductor Selection
          2. 3.2.3.2.2 Cx Capacitance Selection
          3. 3.2.3.2.3 EMI Filter Design
          4. 3.2.3.2.4 DC-Link Output Capacitance
        3. 3.2.3.3 Voltage and Current Measurements
    3. 3.3 Highlighted Products
      1. 3.3.1  TMDSCNCD280039C - TMS320F280039C Evaluation Module C2000™ MCU controlCARD™
      2. 3.3.2  LMG3522R050 - 650-V 50-mΩ GaN FET With Integrated Driver
      3. 3.3.3  LMG2100R044 - 100-V, 35-A GaN Half-Bridge Power Stage
      4. 3.3.4  TMCS1123 - Precision Hall-Effect Current Sensor
      5. 3.3.5  AMC1302 - Precision, ±50-mV Input, Reinforced Isolated Amplifier
      6. 3.3.6  AMC3330 - Precision, ±1-V Input, Reinforced Isolated Amplifier With Integrated DC/DC Converter
      7. 3.3.7  AMC1311 - High-Impedance, 2-V Input, Reinforced Isolated Amplifier
      8. 3.3.8  ISO6741 - General-Purpose Reinforced Quad-Channel Digital Isolators with Robust EMC
      9. 3.3.9  UCC21540 - Reinforced Isolation Dual-Channel Gate Driver
      10. 3.3.10 LM5164 - 100-V Input, 1-A Synchronous Buck DC/DC Converter with Ultra-low IQ
  10. 4Hardware, Software, Testing Requirements, and Test Results
    1. 4.1 Hardware Requirements
    2. 4.2 Test Setup
      1. 4.2.1 DC/DC Board
      2. 4.2.2 DC/AC Board
    3. 4.3 Test Results
      1. 4.3.1 Input DC/DC Boost Results
      2. 4.3.2 CLLLC Results
      3. 4.3.3 DC/AC Results
  11. 5Design and Documentation Support
    1. 5.1 Design Files
      1. 5.1.1 Schematics
      2. 5.1.2 BOM
    2. 5.2 Tools and Software
    3. 5.3 Documentation Support
    4. 5.4 Support Resources
    5. 5.5 Trademarks
  12. 6About the Author

3.2.3.3 Voltage and Current Measurements

The measurement of the AC grid voltage was done using the AMC3330. This device is a precision voltage-sensing reinforced isolated amplifier with integrated DC/DC. This IC has ±1-V input voltage range optimized for voltage measurement with high input impedance. The AC voltage is passed through a voltage divider, thus leading to a linear range of the measurement ±401 V, see Figure 3-14.

GUID-20231204-SS0I-PZLG-HCRS-NJKPMHMJ1XN3-low.svgFigure 3-14 AC Voltage Measurement
GUID-20231204-SS0I-GDGW-QBMZ-2XKZXQZM7MKS-low.svgFigure 3-15 DC-Link Voltage Measurement

The measurement of the DC-link voltage was done with AMC1311, see Figure 3-15. This device is a precision voltage sensing reinforced isolated amplifier without integrated DC/DC. This IC has +2-V input voltage range optimized for voltage measurement with high input impedance. The DC voltage is passed through a voltage divider, thus leading to a linear range of the measurement between 0 V and 441 V. Since the IC does not include a power supply on the high-voltage side, the GaN power supply was used for this purpose.

The measurement of the DC-link current was done with AMC1302. This device is a precision current sensing reinforced isolated amplifier without integrated DC/DC. This IC has +50-mV input voltage range optimized for current measurement with low input impedance. The DC current is passed through a 2-mΩ shunt, thus leading to a linear range of the measurement ±25 A.

GUID-20231204-SS0I-T5WS-6XL8-F0Z3BWGR60QD-low.svgFigure 3-16 DC-Link Current Measurement
GUID-20231206-SS0I-KSN9-QT84-MV9K3NRZR59M-low.svgFigure 3-17 AC Current Measurement

The current in the grid is measured by means of a Hall-based current sensor TMCS1123 which allows measurement of the current into the Point of Common Coupling (PCC) with high accuracy. This design allows a reinforced isolation between the grid and the MCU.