SLYT819 October   2021 BQ25980

 

  1. 1 Introduction
  2. 2 Delivering over 100 W power with USB PD
  3. 3 High-efficiency switched-capacitor DC/DC converters
  4. 4 Output impedance
  5. 5 Switching losses
    1. 5.1 Turnon switching loss
    2. 5.2 Turnoff switching loss
    3. 5.3 Gate driving loss
  6. 6 Dual-phase interleaved switched-capacitor converter
  7. 7 High-power-density switched-capacitor converter
  8. 8 Switched-capacitor converter application: fast charging for portable devices
  9. 9 Conclusion
  10. 10Related Websites
  11. 11Important Notice

5.3 Gate driving loss

Gate driving loss is also part of the switching loss (see Equation 10):

Equation 10. P G A T E = 1 2 Q G S V G A T E f s w

where, the QGS is the gate-to-source charge of the switch, VGATE is the gate turnon voltage and fsw is the switching frequency.

Equation 11 calculates the overall power loss of the switched-capacitor converter, also plotted in Figure 5-1:

Equation 11. P S C = P O U T + ∑ P G A T E + ∑ P D S

The slow switching impedance is inversely proportional to the switching frequency, while the switching loss is proportional to switching frequency. There is an optimized switching frequency for the switched-capacitor converter after determining the topology and capacitor.

Figure 5-1 Overall power loss of the 2-to-1 switched-capacitor converter