TIDT277 April   2022

 

  1.   Description
  2.   Features
  3.   Applications
  4. 1Test Prerequisites
    1. 1.1 Voltage and Current Requirements
    2. 1.2 Considerations
    3. 1.3 Dimensions
  5. 2Testing and Results
    1. 2.1 Efficiency Graphs, all Outputs Similar Loaded
    2. 2.2 Load Regulation
    3. 2.3 Cross Regulation and Further Data For Non-Symmetrical Loading
    4. 2.4 Line Regulation at Full Load to all Outputs
    5. 2.5 Thermal Images
  6. 3Waveforms
    1. 3.1 Switching
      1. 3.1.1 Switchnode to GND
      2. 3.1.2 Diode D3
    2. 3.2 Output Voltage Ripple
    3. 3.3 Input Voltage Ripple
      1. 3.3.1 Power Stage Input
      2. 3.3.2 Between L1 and L2
      3. 3.3.3 Input Terminal
    4. 3.4 Start-Up Sequence
    5. 3.5 Shutdown Sequence

Description

This reference design introduces a tiny auxiliary power supply unit (PSU) used to supply automotive insulated-gate bipolar transistor (IGBT) or automotive silicon carbide (SiC) drive. The isolated outputs support three gate controls, each supplied with +17 V and –4 V. To simplify transformer windings, a virtual ground Zener diode which works for symmetrical loading, is implemented.

The LM25184 controller supports primary-side regulation just by controlling the flyback voltage from secondary side and there is no need for an additional auxiliary winding. Furthermore, valley switching is beneficial for efficiency.

To reduce reflected ripple-to-source, a differential input filter is added to this PSR flyback converter.