JAJU732C June   2019  – July 2022

 

  1.   概要
  2.   Resources
  3.   特長
  4.   アプリケーション
  5.   5
  6. 1System Description
    1. 1.1 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Highlighted Products
      1. 2.2.1  UCC21530
      2. 2.2.2  AMC1311
      3. 2.2.3  AMC3302
      4. 2.2.4  AMC3306M05
      5. 2.2.5  LM76003
      6. 2.2.6  LMZ31707
      7. 2.2.7  OPA320
      8. 2.2.8  ISO7721
      9. 2.2.9  SN6501
      10. 2.2.10 SN6505B
      11. 2.2.11 TMP235
      12. 2.2.12 LMT87
      13. 2.2.13 TL431
      14. 2.2.14 LMV762
      15. 2.2.15 TMS320F280049 C2000 MCU
      16. 2.2.16 TMDSCNCD280049C
    3. 2.3 System Design Theory
      1. 2.3.1 Dual Active Bridge Analogy With Power Systems
      2. 2.3.2 Dual-Active Bridge - Switching Sequence
      3. 2.3.3 Dual-Active Bridge - Zero Voltage Switching (ZVS)
      4. 2.3.4 Dual-Active Bridge - Design Considerations
        1. 2.3.4.1 Leakage Inductor
        2. 2.3.4.2 Effect of Inductance on Current
        3. 2.3.4.3 Phase Shift
        4. 2.3.4.4 Capacitor Selection
        5. 2.3.4.5 Soft Switching Range
        6. 2.3.4.6 Switching Frequency
        7. 2.3.4.7 Transformer Selection
        8. 2.3.4.8 SiC MOSFET Selection
      5. 2.3.5 Loss Analysis
        1. 2.3.5.1 Design Equations
        2. 2.3.5.2 SiC MOSFET and Diode Losses
        3. 2.3.5.3 Transformer Losses
        4. 2.3.5.4 Inductor Losses
        5. 2.3.5.5 Gate Driver Losses
        6. 2.3.5.6 Efficiency
        7. 2.3.5.7 Thermal Considerations
  8. 3Circuit Description
    1. 3.1 Power Stage
    2. 3.2 DC Voltage Sensing
      1. 3.2.1 Primary DC Voltage Sensing
      2. 3.2.2 Secondary DC Voltage Sensing
    3. 3.3 Current Sensing
    4. 3.4 Power Architecture
      1. 3.4.1 Auxiliary Power Supply
      2. 3.4.2 Isolated Power Supply for Sense Circuits
    5. 3.5 Gate Driver
      1. 3.5.1 Gate Driver Circuit
      2. 3.5.2 Gate Driver Bias Power Supply
      3. 3.5.3 Gate Driver Discrete Circuits - Short-Circuit Detection and Two Level Turn Off
  9. 4Hardware, Software, Testing Requirements, and Test Results
    1. 4.1 Required Hardware and Software
      1. 4.1.1 Hardware
      2. 4.1.2 Software
        1. 4.1.2.1 Getting Started With Software
        2. 4.1.2.2 Pin Configuration
        3. 4.1.2.3 PWM Configuration
        4. 4.1.2.4 High-Resolution Phase Shift Configuration
        5. 4.1.2.5 ADC Configuration
        6. 4.1.2.6 ISR Structure
    2. 4.2 Test Setup
    3. 4.3 PowerSUITE GUI
    4. 4.4 LABs
      1. 4.4.1 Lab 1
      2. 4.4.2 Lab 2
      3. 4.4.3 Lab 3
      4. 4.4.4 Lab 4
      5. 4.4.5 Lab 5
    5. 4.5 Test Results
      1. 4.5.1 Open-Loop Performance
      2. 4.5.2 Closed-Loop Performance
  10. 5Design Files
    1. 5.1 Schematics
    2. 5.2 Bill of Materials
    3. 5.3 PCB Layout Recommendations
      1. 5.3.1 Layout Prints
    4. 5.4 Altium Project
    5. 5.5 Gerber Files
    6. 5.6 Assembly Drawings
  11. 6Related Documentation
    1. 6.1 Trademarks
  12. 7Terminology
  13. 8About the Author
  14. 9Revision History

2.3.5.3 Transformer Losses

This section provides an estimate of the different components of transformer loss. The transformer for this design was completed with the help of Payton Planar Magnetics®. This reference design focuses only on the loss of numbers and not the actual design process of the transformer. To select the core for this transformer, the area product approach is considered. The area product of the transformer is calculated by Equation 28.

Equation 28. GUID-F282D080-7CC8-40A2-AEA5-5BD59CBF270F-low.gif

where

  • kf is the waveform factor
  • ku is the utilization factor
  • FSW is the switching frequency
  • Bm is the maximum flux density
  • J is the current density
  • V1 is the primary voltage
  • I1.avg is the primary average current
  • V2 is the secondary voltage
  • I2.avg is the secondary average current

Substitute the values for flux density as 0.2 T, switching frequency as 100 kHz, and utilization factor as 0.3 as this is a planar design. With a waveform factor of 4 and current density as 400 A/cm2, the area product is calculated as 18 cm4. Choosing a core with area product greater than the calculated value, E64/18/50 ferrite DMR44 core was chosen.

Next, the number of turns required for the primary and secondary side is calculated. The number of primary turns is calculated using Equation 29.

Equation 29. GUID-10D98B4F-9D88-425F-9066-46745D638CEA-low.gif

From the data sheet for the core, the effective core area, Ae, is 516 mm2. By substituting this value, the number of turns is approximately 22. In a practical implementation, the number of turns selected in the primary was 24. By using the required conversion ratio of 1.6 between the primary and secondary, the number of secondary turns, Ns, is 15 turns.

Figure 2-24 shows the parameters of the core obtained from the data sheet. The core loss per unit of volume, Pv, at 100°C is approximately 300 mW/cm3. The core volume, Ae, is 81.9 cm2. Therefore, the total core loss at 100 kHz is given by Equation 30.

Equation 30. P C o r e _ l o s s = P v A e l e = 24   W
GUID-0B349ED8-6FC3-41E0-AD01-F873A46D0B5C-low.png Figure 2-24 Transformer Core Data

From the data sheet of the manufacturer, the primary and secondary winding DC resistances were 43 mΩ and 16 mΩ, respectively. The copper losses in the windings were calculated as per Equation 31.

Equation 31. GUID-0A8F353F-EEEB-460F-84CC-02B3D72952FF-low.gif

Losses due to the AC resistance at high frequencies are also arising as a result of the skin effect. At 100 kHz, Figure 2-25 shows that the AC resistance is approximately 12.5 mΩ. These contribute 8 W of loss due to current flowing in the primary and secondary windings.

GUID-9D038850-3EF5-4EBB-863A-4D3B0BD94CD2-low.png Figure 2-25 AC Resistance
Equation 32. GUID-FCC6FB0B-682C-4A2A-9EA9-01A40CC525D7-low.gif

The core loss, copper losses, and skin effect losses together contribute 50 W of transformer loss. The 10-kW planar transformer designed with Payton is summarized in Table 2-2:

Table 2-2 Transformer Specifications
Functional specifications Ratings
Total output power 10 kW (500 V/20 Adc)
Operating frequency 100-200 kHz
Input voltage of transformer 800 V (Vout = 500 V), Bipolar Square waveform;
Volt-second product 8000 V μs – for Vout = 500 V, 100 kHz;
Primary-to-secondary ratio 24:15
Primary current maximum 13.5 Arms (20 A peak) – for Vout = 500 V;
Secondary current maximum 20 Arms (30 A peak) – for Vout = 500 V;
Estimated power losses 50 W – for Vout = 500 V, 100 kHz;
Primary winding DC resistance 43 mΩ
Secondary winding DC resistance 16 mΩ
Leakage inductance

34 µH
Magnetizing inductance 720 µH

More details of this transformer are available from Payton.