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

7 High-power-density switched-capacitor converter

Table 7-1 compares the power density among a traditional two-level buck converter, three-level buck converter [5] and switched-capacitor IC with similar input and output voltage ranges.

The power rating of the converters is limited by 1.4-W overall power loss. The DSBGA IC package is used for all of the topologies. The total solution size assumes an extra 20% for board layout in addition to the size of the IC and energy storage components. The switched-capacitor converter has four times higher power density compared to the two-level buck converter and 90% higher power density compared to the three-level buck converter.

Table 7-1 Power density comparison.
Topology Power Rating at 1.4-W Loss IC Die Size Inductor or Capacitor Size Total Solution Size Maximum Height Power Density
Two-level buck [6] 15 W 7 mm2 17.6 mm2 30 mm2 1.2 mm 0.42 W/mm3
Three-level buck [5] 20 W 6.1 mm2 5 mm2 14 mm2 1.2 mm 1.19 W/mm3
Switched capacitor 40 W 9.6 mm2 7.7 mm2 22 mm2 0.8 mm 2.26 W/mm3