TIDUF28 November   2023

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Highlighted Products
      1. 2.2.1 LMG3422R030
      2. 2.2.2 ISO7741
      3. 2.2.3 AMC1306M05
      4. 2.2.4 AMC1035
      5. 2.2.5 TPSM560R6H
      6. 2.2.6 TPSM82903
  9. 3System Design Theory
    1. 3.1 Power Switches
      1. 3.1.1 GaN-FET Selection Criterion
      2. 3.1.2 HVBUS Decoupling and 12-V Bootstrap Supply
      3. 3.1.3 GaN_FET Turn-on Slew Rate Configuration
      4. 3.1.4 PWM Input Filter and Dead-Time Calculation
      5. 3.1.5 Signal Level Shifting
      6. 3.1.6 LMG3422R030 Fault Reporting
      7. 3.1.7 LMG3422R030 Temperature Monitoring
    2. 3.2 Phase Current Sensing
      1. 3.2.1 Shunt
      2. 3.2.2 AMC1306M05 Analog Input-Filter
      3. 3.2.3 AMC1306M05 Digital Interface
      4. 3.2.4 AMC1306M05 Supply
    3. 3.3 DC-Link (HV_BUS) Voltage Sensing
    4. 3.4 Phase Voltage Sensing
    5. 3.5 Control Supply
    6. 3.6 MCU Interface
  10. 4Hardware, Software, Testing Requirements, and Test Results
    1. 4.1 Hardware Requirements
      1. 4.1.1 PCB
      2. 4.1.2 MCU Interface
    2. 4.2 Software Requirements
    3. 4.3 Test Setup
      1. 4.3.1 Precautions
      2. 4.3.2 Test Procedure
    4. 4.4 Test Results
      1. 4.4.1 24-V Input Control Supply
      2. 4.4.2 Propagation Delay PWM to Phase Voltage Switch Node
      3. 4.4.3 Switch Node Transient at 320-VDC Bus Voltage
      4. 4.4.4 Phase Voltage Linearity and Distortion at 320 VDC and 16-kHz PWM
      5. 4.4.5 Inverter Efficiency and Thermal Characteristic
        1. 4.4.5.1 Efficiency Measurements
        2. 4.4.5.2 Thermal Analysis and SOA Without Heat Sink at 320 VDC and 16-kHz PWM
  11. 5Design and Documentation Support
    1. 5.1 Design Files
      1. 5.1.1 Schematics
      2. 5.1.2 BOM
      3. 5.1.3 PCB Layout Recommendations
        1. 5.1.3.1 Layout Prints
      4. 5.1.4 Altium Project
      5. 5.1.5 Gerber Files
      6. 5.1.6 Assembly Drawings
    2. 5.2 Tools and Software
    3. 5.3 Documentation Support
    4. 5.4 Support Resources
    5. 5.5 Trademarks
  12. 6About the Author

3.3 DC-Link (HV_BUS) Voltage Sensing

The TIDA-010255 is designed to operate at a nominal DC-link voltage of 320 VDC and a maximum DC-link voltage up to 400 VDC, corresponding to a single-phase 200-VAC to 250-VAC input. Accurate sensing of the DC-link voltage is important to calculate the corresponding duty cycle of the three-phase PWM, monitor for overvoltage and undervoltage, and estimate the amplitude of phase voltages.

Due to the hot-side control architecture, the DC-link voltage can be sensed through a non-isolated delta-sigma modulator AMC1035 with a corresponding high-voltage resistor divider. The AMC1035 has a maximum bipolar input voltage range of ±1.25 V and a linear input voltage range of ±1 V. The high-impedance resistor dividers R1, R2, R3, and R4 are scaled to provide a 1-V signal at the AMC1035 input at 480-VDC bus voltage. R1, R2, and R3 are high-voltage resistors.

The AMC1035 analog input filter is designed similar to the AMC1306M05 in Section 3.2.2. However, the cutoff frequency is initially set to around 23-kHz. The analog input filter is determined by R4, R42, R44, and C65, and can be changed to any desired lower or higher cutoff frequency, for example in systems which monitor the AC voltage ripple on the DC-bus.

The MCE pin is set to low to configure for a bitstream data output at DOUT. Data at DOUT changes with the rising edge of the clock signal present on CLKIN. The line termination and filtering are similar as described in Section 3.2.3. A separate clock signal MCU_CLK_VDC_BUF is provided to allow the same of a different clock rate for DC-link voltage sensing, and is then configured for the three current-sensing modulators AMC1306M05. The AMC1035 supports clock input signals from 9 MHz to 21 MHz. The REFOUT is not used in this design and is terminated with C27 (3.3 nF) and a series resistor R17 (56 Ω).

GUID-20231101-SS0I-LG1B-P0FL-QLD1G13VDH8L-low.gifFigure 3-8 DC-link Voltage Sensing With Non-isolated Modulator Schematic