A Resonant Switched-Capacitor based 48-to-12 V Bus Converter Achieving 2500 W/in 3 Power Density and 99.0% Peak Efficiency Zichao Ye Robert Pilawa-Podgurski Introduction This work presents a new type of hybrid switched-capacitor based power converter, named cascaded resonant converter, which can have significantly higher efficiency than the state- of-the-arts. This disruptive technology has the potential to greatly reduce the energy loss in the power delivery system of data centers. Why Hybrid Switched-Capacitor Converter C 1 S 1 C 2 R esr R out R load V in S 1A S 1B L + V out _ C o V x S 1a S 2a S 1b S 2b C 1 V in R load C o Hybrid switched-capacitor converters use both capacitors and inductors in the power transfer process. The inductor behaves like a current source and can help recover the charge sharing loss, through an operation called soft charging. Capacitors have a energy density that is up to 100x higher than inductors. However, the inherent charge sharing loss mechanism significantly undermines this advantage. Switched-capacitor converter Buck converter Cascaded Resonant Converter S 1B S 2B S 1A S 2A C fly V in I L V sw S 1B S 2B S 1A S 2A C fly V in I L V sw Good balance of active and passive components. Good component tolerance, repeatability and reliability. Cascading basic 2-to-1 ReSC converters to achieve higher conversion ratio. Two-phase interleaved design C mid needs to provide a stiff voltage. The combined input current of the second stage closely matches the inductor current of the first stage. This way C mid can be reduced dramatically. Zero Voltage Switching Help improve light-load efficiency by up to 50%. Hardware Implementation Dimensions (one phase): 1.38 x 0.46 x 0.22 inch (3.5 x 1.17 x 0.56 cm). Note: limited C in and C out are included Experimental Results Full load with fan cooling only Open-loop load regulation 10 A to 30 A load step resonant operation zero voltage switching Comparison with buck converter loss breakdown 48-to-12 V

A Resonant Switched-Capacitor based 48-to-12 V Bus ... · A Resonant Switched-Capacitor based 48-to-12 V Bus Converter Achieving 2500 W/in3 Power Density and 99.0% Peak Efficiency

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Page 1: A Resonant Switched-Capacitor based 48-to-12 V Bus ... · A Resonant Switched-Capacitor based 48-to-12 V Bus Converter Achieving 2500 W/in3 Power Density and 99.0% Peak Efficiency

A Resonant Switched-Capacitor based 48-to-12 V Bus Converter Achieving 2500 W/in3 Power Density and 99.0% Peak Efficiency

Zichao YeRobert Pilawa-Podgurski

IntroductionThis work presents a new type of hybrid switched-capacitor based power converter, named cascaded resonant converter, which can have significantly higher efficiency than the state-of-the-arts. This disruptive technology has the potential to greatly reduce the energy loss in the power delivery system of data centers.

Why Hybrid Switched-Capacitor Converter

Resr

RoutRload

Vin

S1A

S1B

+Vout

_Co

S1a S2a

S1b S2b

C1VinRloadCo

Hybrid switched-capacitor converters use both capacitors and inductors in the power transfer process. The inductor behaves like a current source and can help recover the charge sharing loss, through an operation called soft charging.

Capacitors have a energy density that is up to 100x higher than inductors. However, the inherent charge sharing loss mechanism significantly undermines this advantage.

Switched-capacitor converter

Buck converter

Cascaded Resonant Converter

S1B S2B

S1A S2A

CflyVin

Vsw

S1B S2B

S1A S2A

CflyVin

Vsw

Good balance of active and passive components.