TIDUF86A January   2025  – July 2025

 

  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 System Overview
    3. 2.3 Highlighted Products
      1. 2.3.1 LMG3100
      2. 2.3.2 LMR38010
      3. 2.3.3 TMP61
      4. 2.3.4 TPS7B81
      5. 2.3.5 OPA4323
  9. 3System Design Theory
    1. 3.1 Power Stage Design: Three-Phase Inverter
    2. 3.2 LMG3100 GaN-FET Power Stage
    3. 3.3 Power Management
    4. 3.4 Current-Sensing Circuit
    5. 3.5 Overcurrent Protection Circuit
    6. 3.6 Phase Voltage and DC Input Voltage Sensing
    7. 3.7 Power-Stage PCB Temperature Monitor
    8. 3.8 Interface to Host MCU
  10. 4Hardware, Testing Requirements, and Test Results
    1. 4.1 Hardware Requirements
      1. 4.1.1 TIDA-010276 PCB Overview
      2. 4.1.2 TIDA-010276 Jumper Settings
    2. 4.2 Test Setup
    3. 4.3 Test Results
      1. 4.3.1 Power Management and System Power Up and Power Down
      2. 4.3.2 GaN Inverter Switch Node Voltage
      3. 4.3.3 Switch Node Voltage Transient Response
      4. 4.3.4 Impact of PWM Frequency to DC-Bus Voltage Ripple
      5. 4.3.5 Efficiency Measurements
      6. 4.3.6 Thermal Analysis
  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

4.3.5 Efficiency Measurements

The efficiency testing was done at a 27°C lab temperature using a HIOKI® PW6001 power analyzer and HIOKI® CT6872 current transformer. The PWM carrier frequency was set from 20Hz to 80kHz. The voltage is 36V and the motor speed is 600rpm, with the motor running in current mode to test the power loss. Figure 4-24 shows a picture of the test setup. For all of these tests neither a heat sink nor a fan were used, hence only natural convection of the TIDA-010276 PCB is applied.


TIDA-010276 Test Setup for Inverter Efficiency Analysis

Figure 4-24 Test Setup for Inverter Efficiency Analysis

Figure 4-25 shows the TIDA-010276 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.


TIDA-010276 TIDA-010276 Board Losses at 36V Input vs 3-Phase Output Current

Figure 4-25 TIDA-010276 Board Losses at 36V Input vs 3-Phase Output Current

The TIDA-010276 power losses are dominated by the losses in the GaN FETs (LMG3100) and the losses in the 0.5mΩ bus current shunt resistor and three 0.5mΩ low-side FET shunt resistors. The theoretical maximum peak efficiency at 36VDC with a maximum phase-to-phase voltage of 14.69VRMS (Space Vector PWM with 3rd harmonics) and a power factor of 0.9 is 99.16% at 20kHz PWM, 99.01% at 40Hz PWM, 98.58% in 80kHz, according to the calculation results shown in Figure 4-26.

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 LMG3100R17 GaN FETs to help to achieve very high efficiency even at higher PWM switching frequencies.


TIDA-010276 Calculated Maximum Peak Efficiency at 36VDC and 40kHz, 60kHz, and 80kHz PWM

Figure 4-26 Calculated Maximum Peak Efficiency at 36VDC and 40kHz, 60kHz, and 80kHz PWM

The TIDA-010276 design and an e-bike motor were used for system testing. Testing determined that increasing the switching frequency also improves the overall efficiency of the motor drive. Table 4-3 details the TIDA-010276 motor system efficiency test results.

Table 4-3 TIDA-010276 Motor System Efficiency Test Results
PARAMETER 20kHz (DEAD TIME 1μs) 80kHz (DEAD TIME 16.6ns)
PIN 49.8W 48.2W
POUT(Inverter) 49.2W 47.5W
η (Inverter) 98.70% 98.50%
Speed 480rpm 480rpm
Torque 0.68Nm 0.68Nm
Pmech 34.178W 34.178W
η (motor) 68.63% 70.90%
η (total) 67.7% 69.9%