TIDUF68 February   2024

 

  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 Design Considerations
    3. 2.3 Highlighted Products
      1. 2.3.1 LMG2100
      2. 2.3.2 INA241A
      3. 2.3.3 LMR38010
  9. 3System Design Theory
    1. 3.1 Three-Phase GaN Inverter Power Stage
      1. 3.1.1 LMG2100 GaN Half-Bridge Power Stage
    2. 3.2 Inline Shunt Precision-Phase Current Sensing With INA241A
    3. 3.3 Phase Voltage and DC Input Voltage Sensing
    4. 3.4 Power-Stage PCB Temperature Monitor
    5. 3.5 Power Management
      1. 3.5.1 48V to 5V DC/DC Converter
      2. 3.5.2 5V to 3.3V Rail
    6. 3.6 Interface to Host MCU
  10. 4Hardware, Software, Testing Requirements, and Test Results
    1. 4.1 Hardware Requirements
      1. 4.1.1 TIDA-010936 PCB Overview
      2. 4.1.2 TIDA-010936 Jumper Settings
      3. 4.1.3 Interface to C2000™ MCU LaunchPad™ Development Kit
    2. 4.2 Software Requirements
    3. 4.3 Test Setup
    4. 4.4 Test Results
      1. 4.4.1 Power Management and System Power Up and Power Down
    5. 4.5 GaN Inverter Half-Bridge Module Switch Node Voltage
      1. 4.5.1 Switch Node Voltage Transient Response at 48V DC Bus
        1. 4.5.1.1 Output Current at ±1A
        2. 4.5.1.2 Output Current at ±10A
      2. 4.5.2 Impact of PWM Frequency to DC-Bus Voltage Ripple
      3. 4.5.3 Efficiency Measurements
      4. 4.5.4 Thermal Analysis
      5. 4.5.5 No Load Loss Test (COSS Losses)
  11. 5Design and Documentation Support
    1. 5.1 Design Files [Required Topic]
      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
  13. 7Recognition

4.5.3 Efficiency Measurements

The efficiency testing was done at 27°C lab temperature using a HIOKI PW6001 Power Analyzer and HIOKI CT6872 current transformer. The TIDA-010936 was powered with 48V DC and a high-power servo motor was used as load (72V, 21A). A dynamometer supplies high load in the motor. The PWM carrier frequency was set from 40Hz to 80kHz. The motor speed is 600RPM. Figure 4-20 shows a picture of the test setup and block diagram for wiring.

For all of these tests neither a heat sink nor a fan were used, hence only natural convection of the TIDA-010936 PCB applied.


GUID-20240220-SS0I-0927-0LGK-Z8K0KBHLKD1P-low.jpg

Figure 4-20 TIDA-010936 Test Setup for Inverter Efficiency Analysis

GUID-20240220-SS0I-HS5M-ZHQD-CFTK9G6X2Q3T-low.svg

Figure 4-21 TIDA-010936 Wiring Block Diagram for Inverter Efficiency Analysis

Figure 4-22 shows the TIDA-010936 power losses versus the three-phase motor load current in ARMS. These numbers do not include the power losses of the C2000 MCU LaunchPad development kit.


GUID-20240220-SS0I-Q4PR-HB2X-QHZJS3LRJLZW-low.svg

Figure 4-22 TIDA-010936 Board Losses at 48V Input Versus 3-Phase Output Current

The TIDA-010936 board power losses at maximum load current of 14.8ARMS were 9.66W at 40kHz PWM and 10.5W 80kHz PWM. The TIDA-010936 power losses are dominated by the losses in the GaN FETs (LMG2100) and the losses in the 1mΩ shunt resistors.

The theoretical maximum peak efficiency at 48VDC with a maximum phase-to-phase voltage of 19.5VRMS (Space Vector PWM with 3rd harmonics) and a power factor of 0.9 is 99.3% at 40kHz PWM and 99.2% at 80kHz PWM, as shown in Figure 4-23.

Observe that while the PWM switching frequency increases, the power losses of the board do not increase significantly. This also reflects the very low switching losses of the LMG2100R044 GaN-FETs to help to achieve very high efficiency even at higher PWM switching frequencies.

GUID-20240220-SS0I-LFVM-VHTR-4JNLVMW7PGJ6-low.svg Figure 4-23 Calculated Maximum Peak Efficiency at 48VDC and 40, 60, and 80kHz PWM