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
3.2.3.2.1 Boost Inductor Selection

The mission mask for many standards starts at 150 kHz; therefore, selecting a switching frequency below 150 kHz is good design practice. In this design, a switching frequency of 125 kHz was selected for the totem pole DC/AC. By selecting an operating frequency of 125 kHz, the first harmonic does not require significant attenuation but only the successive one as the 2nd, 3rd, and so forth. A current ripple factor of 20 % was selected for the boost inductor, when having 120-VAC output. The inductance value was calculated by using Equation 13 and Equation 14 for a worst-case duty cycle equal to 50%:

Equation 21. I p k - p k = 0.2 × 1600   W ( 110 × 2 )   V =   2.06   A
Equation 22. L =   0.5 × ( 1 - 0.5 ) 2.06   A × 125   k H z × 110 × 2 V = 106   μ H

An inductance value equal to 106 μH was calculated. Bourns 145450 (D6746) was selected and this is an inductor rated 111 μH. In general, the boost inductor contributes to the differential and common mode noise attention.