SLUAAH0 February   2022 UCC14130-Q1 , UCC14131-Q1 , UCC14140-Q1 , UCC14141-Q1 , UCC14240-Q1 , UCC14241-Q1 , UCC14340-Q1 , UCC14341-Q1 , UCC15240-Q1 , UCC15241-Q1

 

  1.   Trademarks
  2. 1 Introduction
    1. 1.1 Pin Configuration and Functions
  3. 2 Three-Phase Traction Inverter
  4. 3 Gate Drive Bias Requirements
    1. 3.1 Gate Drive Bias Architectures
    2. 3.2 IGBT vs. SiC
    3. 3.3 Determining Required Bias Supply Power
    4. 3.4 Input Voltage Requirements
    5. 3.5 Output Voltage Requirements
  5. 4 Single Positive Isolated Output Voltage
  6. 5 Dual Positive and Negative Output Voltages
  7. 6 Dual Positive Output Voltages
  8. 7 Capacitor Selection
  9. 8 RLIM Current Limit Resistor
    1. 8.1 RLIM Functional Description
    2. 8.2 RLIM Dual Output Configuration
      1. 8.2.1 CVEE Above Nominal Value CVDD Below Nominal Value
      2. 8.2.2 CVEE Below Nominal Value CVDD Above Nominal Value
      3. 8.2.3 Gate Driver Quiescent Current: IQ_VEE > IQ_VDD
      4. 8.2.4 Gate Driver Quiescent Current: IQ_VEE < IQ_VDD
      5. 8.2.5 CVEE Above Nominal Value CVDD Below Nominal Value: IQ_VEE > IQ_VDD
      6. 8.2.6 CVEE Below Nominal Value CVDD Above Nominal Value: IQ_VEE < IQ_VDD
    3. 8.3 RLIM Single Output Configuration
  10. 9 UCC14240-Q1 Excel Design Calculator Tool
  11. 10Thermal Considerations
    1. 10.1 Thermal Resistance
    2. 10.2 Junction-to-Top Thermal Characterization Parameter
    3. 10.3 Thermal Measurement and TJ Calculation Example
  12. 11Enable (ENA) and Power Good (/PG)
  13. 12PCB Layout Considerations
  14. 13Reference Design Example
  15. 14Summary
  16. 15References

3.3 Determining Required Bias Supply Power

Once a bias architecture is decided, the first step for designing the bias supply is determining the power required according to the IGBT or SiC power module gate charge, QG. Table 3-1 highlights some key parameters comparing two 1.2-kV IGBT vs SiC modules.

Table 3-1 IGBT vs SiC Parametric Comparison
VCE, VDS (V) IC, ID (A) VGE, VGS (V) VGE/S(th), (V) QG (µC)
6-pack IGBT 1200 380 -8/15 5.2 1.75
6-pack SiC 1200 400 -5/15 3.25 1.32

Knowing QG, VGE(ON), VGE(OFF) and the switching frequency, FSW, the required power, due to dynamic switching, can be calculated according to Equation 1.

Equation 1. PSW=QG×VGE/SON-VGE/SOFF×Fsw

There is also power required to support the product of the total bias voltage and gate drive quiescent current, IQ. The quiescent current for a given driver can be obtained from the manufacturers data sheet. Some gate driver IC data sheets specify IQ_VDD and IQ_VEE separately but others can only specify IQ_VDD. For calculating quiescent power, the larger IQ value should be used and the power can be calculated according to Equation 2.

Equation 2. PIQ=VGE/SON-VGE/SOFF×IQ

The total required bias power is then given as:

Equation 3. PBIAS=PSW+PIQ

For the purpose of comparison, assume a gate driver such as the UCC21732-Q1 is used for the IGBT and SiC. From the UCC21732-Q1 data sheet, the maximum IQ_VDD is given as 5.9 mA. If both are operating at 20 kHz and switching over their full range of QG, the required gate drive bias power for each of the modules listed in Table 3-1, is given by Equation 4 and Equation 5 as:

Equation 4. PBIAS(IGBT)=15 V--8 V×1.75 μC×20 kHz+5.9 mA=941 mW
Equation 5. PBIAS(SiC)=15 V--5 V×1.32 μC×20 kHz+5.9 mA=646 mW

In addition to the well-known, dynamic switching and thermal benefits gained from SiC modules, their lower gate charge and ΔVGS offers a less recognized, secondary benefit of a 31.4% reduction in required bias power compared to a similar rated IGBT module.