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

6 Dual-phase interleaved switched-capacitor converter

Part of the slow switching power loss is consumed in the switches as extra conduction loss because of the current spikes when connecting two different voltage capacitors. The current spikes increase the current root-mean-square (RMS) value and cause extra conduction loss. Increasing the switching frequency is one way to reduce the RMS current; however, the switching loss increases.

A dual-phase interleaved topology is one way to reduce the RMS current without increasing the switching loss. A dual-phase topology enables continuous current flow from the input source; therefore, it is possible to reduce the input voltage ripple. Figure 6-1 compares the switching field-effect transistor (FET) current waveforms between single- and dual-phase interleaved using same total flying capacitor in simulation. To deliver the same output current and output power, the current ripple in single phase is significantly larger compared with dual phase; thus, the conduction loss is much smaller in the dual-phase, interleaved switched-capacitor converter under the same device size.

Figure 6-1 Simulated switching FET current waveforms comparison of Q1/Q3 current in single-phase switched capacitor (a); dual-phase switched capacitor (b).