SDAA195 January   2026 LMG3522R030

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Operating Principles in a Flying Capacitor Switching Cell
    1. 2.1 Switching Pattern of a 3-Level Flying Capacitor Switching Cell
  6. 3Design Considerations of a Flying Capacitor Switching Cell
    1. 3.1 Conduction and Switching Losses
      1. 3.1.1 AC Conduction Losses
      2. 3.1.2 AC Switching Losses
    2. 3.2 Passive Components Design
      1. 3.2.1 Boost Inductor Design
      2. 3.2.2 DC Link High Frequency Ripple
      3. 3.2.3 Flying Capacitor Design
    3. 3.3 Layout Considerations
    4. 3.4 Pre-Charging Network
  7. 4Experimental Results
    1. 4.1 Pre-charging of the Flying Capacitor of TIDA-010957
    2. 4.2 Steady State Operation
  8. 5Summary
  9. 6References

4.1 Pre-charging of the Flying Capacitor of TIDA-010957

Precharging Sequence of the Flying Capacitor-Grid Voltage and Grid CurrentFigure 4-2 Precharging Sequence of the Flying Capacitor-Grid Voltage and Grid Current

Precharging Sequence of the Flying Capacitor-DC link Voltage, Flying Capacitor Voltage and Voltage Stress of the External Transistor

Figure 4-3 Precharging Sequence of the Flying Capacitor-DC link Voltage, Flying Capacitor Voltage and Voltage Stress of the External Transistor

In Figure 4-2 and Figure 4-3, waveforms associated with the precharging sequence are provided. The following waveforms are shown:

  • Current on phase L1
  • Voltage on phase L1
  • DC link voltage
  • Flying capacitor voltage
  • Voltage stress of external transistors

In this test, the converter under test has been connected to the grid. Note that a grid voltage is present immediately on the terminal of the converter. Once the grid voltage is established a grid inrush current is generated. Voltages across the FETs are effectively clamped to 520V by the zener diodes.