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

4.2 Steady State Operation

This reference design was tested in four different operating modes:

  • Inverter operation: power converted from the DC to the grid.
  • PFC operation: power converter from the grid to the DC.
  • Inverter plus Capacitive Power Compensator: active power is injected together with reactive power into the grid.
  • Inverter plus Inductive Power Compensator: active power is injected and reactive power is drained from the grid.

The data collected during the experiments were collected and are shown in Figure 4-4 through Figure 4-11. In these pictures, switching node voltage, grid current and grid voltage for all the four operating points are shown.

Experimental PFC Operation: Line Current, Line Voltage, and Switching Node Voltage (Figure A)Figure 4-4 Experimental PFC Operation: Line Current, Line Voltage, and Switching Node Voltage (Figure A)

Experimental PFC Operation: Line Current, Line Voltage, and Switching Node Voltage (Figure B)

Figure 4-5 Experimental PFC Operation: Line Current, Line Voltage, and Switching Node Voltage (Figure B)
Experimental Inverter Operation: Line Current, Line Voltage, and Switching Node Voltage (Figure A)Figure 4-6 Experimental Inverter Operation: Line Current, Line Voltage, and Switching Node Voltage (Figure A)

Experimental Inverter Operation: Line Current, Line Voltage, and Switching Node Voltage (Figure B)

Figure 4-7 Experimental Inverter Operation: Line Current, Line Voltage, and Switching Node Voltage (Figure B)
Experimental Inverter Plus Capacitive Compensation: Line Current, Line Voltage, and Switching Node Voltage (Figure A)Figure 4-8 Experimental Inverter Plus Capacitive Compensation: Line Current, Line Voltage, and Switching Node Voltage (Figure A)

Experimental Inverter Plus Capacitive Compensation: Line Current, Line Voltage, and Switching Node Voltage (Figure B)

Figure 4-9 Experimental Inverter Plus Capacitive Compensation: Line Current, Line Voltage, and Switching Node Voltage (Figure B)
Experimental Inverter Plus Inductive Compensation: Line Current, Line Voltage, and Switching Node Voltage (Figure A)Figure 4-10 Experimental Inverter Plus Inductive Compensation: Line Current, Line Voltage, and Switching Node Voltage (Figure A)

Experimental Inverter Plus Inductive Compensation: Line Current, Line Voltage, and Switching Node Voltage (Figure B)

Figure 4-11 Experimental Inverter Plus Inductive Compensation: Line Current, Line Voltage, and Switching Node Voltage (Figure B)

At first, it can be observed that the switching node voltage shows three distinguished levels when considering the electrical frequency grid period. This is because half of the period a duty cycle lower than 50% is required and the other half of the period a duty cycle higher than 50% is required. Having three voltage levels plus doubling of the equivalent switching frequency permits the grid current to have a low ripple current as can be seen from the previous figures. Secondly, note that from these results that this topology can operate on all the operating points by keeping still the same performances because no worsening in the ripple current or efficiency were observed. In this reference design, by using LMG3522R030 a peak efficiency of 98.9% at 18kW was measured when having a mean junction temperature of 105°C. The junction temperature was derived from the device using the integrated temperature sensing feature.