TIDUF63A December   2023  – June 2024

 

  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. 3.2.2.3 Modulation scheme
      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 Test
      2. 4.2.2 DC/AC Test
    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
  13. 7Revision History

1 System Description

Energy sustainability and security are accelerating the demands for renewable energy like solar and energy storage systems. In residential use cases, micro inverters present a good trade-off in terms of costs and efficiency together with a simple end-user installation. Conversely, the energy storage system becomes a challenge in existing micro inverters due to the lack of a bidirectional converter in this end-equipment.

This reference design is intended to show a possible implementation of a 4-channel micro inverter with fully bidirectional power flow to combine PV input functionality with a 48-V BESS.

The design contains three main stages:

  • PV or Battery input with DC/DC converter with individual MPPT functionality
  • Isolated Capacitor-Inductor-Inductor-Inductor-Capacitor (CLLLC) converter
  • Totem-pole DC/AC converter

Each stage is based on GaN technology to achieve high power density and efficiency.

The design containins four input DC/DC converters, one isolated CLLLC converter and a totem-pole DC/AC converter. All DC/DC conversion stages in the board are based on top-side cooled GaN devices from TI and are placed on the bottom side of the board. This enables dissipation of the power losses into the heat sink.

The DC/AC part contains DC link electrolytic capacitors, a totem-pole DC/AC converter, pre-charging circuit and EMI filter. The high-frequency branch of the totem-pole DC/AC is based on top-side cooled GaN devices from TI.

The board is mounted above an aluminum heat sink which is connected by means of thermal interface materials to the GaN FETs. The design is supposed to work in static cooling condition and the the board size is 28mm × 200 mm × 200 mm. Overall system dimension is 40 mm × 200 mm × 200 mm, thus leading to a volume of 1.6 liter. The calculated power density is equal to 1 kW/liter.