TIDUFD2 May   2025

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Terminology
    2. 1.2 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Input Capacitors Selection
      2. 2.2.2 DC Side
      3. 2.2.3 AC Side
    3. 2.3 Highlighted Products
      1. 2.3.1 TMDSCNCD28P55X - controlCARD Evaluation Module
        1. 2.3.1.1 Hardware Features
        2. 2.3.1.2 Software Features
      2. 2.3.2 LMG2100R026 - 100V, 53A GaN Half-Bridge Power Stage
      3. 2.3.3 LMG365xR035 - 650V 35mΩ GaN FET With Integrated Driver and Protection
      4. 2.3.4 TMCS1123 - Precision 250kHz Hall-Effect Current Sensor With Reinforced Isolation
      5. 2.3.5 TMCS1133 - Precision 1MHz Hall-Effect Current Sensor With Reinforced Isolation
      6. 2.3.6 INA185 - 26V, 350kHz, Bidirectional, High-Precision Current Sense Amplifier
      7. 2.3.7 LM5164 – 100V Input, 1A Synchronous Buck DC-DC Converter With Ultra-Low IQ
      8. 2.3.8 ISO6762 – General-Purpose Six-Channel Reinforced Digital Isolators With Robust EMC
  9. 3System Design Theory
    1. 3.1 Isolation for Solar Inverters
    2. 3.2 Topology Overview
    3. 3.3 Control Theory
      1. 3.3.1 Single and Extended Phase Shift Modulation Technique
      2. 3.3.2 Zero Voltage Switching and Circulating Current
      3. 3.3.3 Optimized Control Method
      4. 3.3.4 Dead-Time Compensation
      5. 3.3.5 Frequency Modulation
      6. 3.3.6 Controller Block Diagram
    4. 3.4 MPPT and Input Voltage Ripple
  10. 4Hardware, Testing Requirements, and Test Results
    1. 4.1 Hardware Requirements
    2. 4.2 Test Setup
      1. 4.2.1 Board Check
      2. 4.2.2 DC-DC Tests
      3. 4.2.3 DC-AC Tests
    3. 4.3 Test 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

2.2.1 Input Capacitors Selection

TIDA-010954 DC Input and Current MeasurementsFigure 2-2 DC Input and Current Measurements

As Section 3.4 explained, in the design needs significant input capacitors to maintain power ripple and low input voltage variation.

In this design, the MPP deviation is defined as 1%, this means that > 99% of the maximum possible power is delivered to the inverter input. PV panels from several top manufacturers change output power for 1% from MPP if the voltage changed for ±4% from VMPP. So input voltage ripple for input capacitors defined as 8%.

The MPP voltage for major 600W panels is more than 40V. This means the input capacitor needs to handle 600W, 100Hz power ripple with 8% voltage ripple.

Use Equation 16 to calculate the required capacitance.

About 15mF of capacitance is needed; therefore, 5 × capacitors, 3300μF, 63V, and 18mm in diameter are selected. The capacitors are installed horizontally to reduce the board height. Total capacitance is 16.5mF and the current ripple is about 2A which is lower than the maximum allowed current ripple for this type of capacitor – 2.6A.