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Zero-voltage-switching switched capacitor converter (ZSC)

Infineon's zero voltage switching switched-capacitor converter (ZSC) topology ¨C delivering high efficiency and power density for 48 V input systems

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Overview

Infineon's two-stage 48 V/54 V ZSC architecture for high-performance processors (CPU, GPU, SoC, AI accelerator card, ASIC, etc.) offers flexibility in implementation and scalability for different power levels without compromising on performance.

Benefits

  • High efficiency
  • Excellent power density
  • Simplicity in design
  • Flexibility in implementation
  • Scalable architecture
  • Robust system design

Block diagram

About

Zero voltage switching switched-capacitor converter (ZSC)

The 48 V power distribution architecture can significantly reduce I2R losses, but also poses many challenges, such as efficient voltage conversion and system stability. With the introduction of proprietary ZSC and HSC topologies, Infineon is successfully addressing those challenges.

The ZSC topology provides a 12 V unregulated rail from 48 V bus voltage, and primarily relies on switches and capacitors to transfer the energy from a higher voltage rail to a lower one. The topology inherently ensures zero voltage switching operation, enabling high switching frequency and high power density. This means that the switches in the converter turn on and off when the voltage across them is zero, which minimizes switching losses and improves efficiency. Additionally, since the converter operates at a high frequency, it can use smaller magnetic components such as inductors and transformers, which saves space and reduces cost.

By using Infineon's ZSC topology for your designs, you can effectively tackle the challenges of 48 V power distribution architecture and ensure that your system is efficient and cost-saving.

ZSC topology operation

ZSC is a resonant switch converter that operates in an over-resonant fashion. The inductor and capacitor (L-C) networks generate current and voltage waveforms that vary in a sinusoidal manner in each switching period. Optimum efficiency occurs when the switching frequency matches the LC resonant frequency so that switching is both zero voltage and zero current. While a perfect match is impossible, the ZVS inductor compensates the mismatch to force the voltage to zero before each MOSFET is switched on.?

In this scheme, the dominant contributors to loop inductance are the MOSFETs, specifically the clips, bond wires, and lead frame of their packages and the capacitors. The PCB also contributes to inductance around the loop. Due to the over-resonant operation and the addition of the ZVS inductor, perfect PCB layout is not required. However, for optimum efficiency, power shape routing should be robust to minimize I2R losses while having small commutation loops to minimize AC losses.?

Interested? Infineon offers PCB design recommendations to guide your physical design process to ensure peak performance and efficiency. Check them out below.

ZSC topology features

The main advantage of using ZSC in your designs is its ability to achieve high efficiency and density.?

This is achieved by the use of low voltage FETs with better Figure-of-Merit (Vout , 2 x Vout). The ZSC topology uses low voltage MOSFETs with a better figure-of-merit (FOM) to achieve higher efficiency, reduce switching losses, and enable high-frequency operation. To further minimize switching losses, ZSC uses soft-switching operation regardless of component tolerances and input voltage variation (LZVS provides soft-switching capability).

Furthermore, ZVS switching enables high switching frequency operation. By switching at zero voltage, the MOSFETs can handle higher frequencies, contributing to higher power density. The inherent drop current sharing feature simplifies the parallel operation and ensures that each ZSC contributes to the power transfer function, to increase the power output.

When choosing Infineon's ZSC in your designs, there is no need to use power magnetic components in the main current path. The LC resonant network provides the power transfer function, eliminating the large, expensive transformers, reducing the size and cost of the circuit.

Zero voltage switching switched-capacitor converter (ZSC)

The 48 V power distribution architecture can significantly reduce I2R losses, but also poses many challenges, such as efficient voltage conversion and system stability. With the introduction of proprietary ZSC and HSC topologies, Infineon is successfully addressing those challenges.

The ZSC topology provides a 12 V unregulated rail from 48 V bus voltage, and primarily relies on switches and capacitors to transfer the energy from a higher voltage rail to a lower one. The topology inherently ensures zero voltage switching operation, enabling high switching frequency and high power density. This means that the switches in the converter turn on and off when the voltage across them is zero, which minimizes switching losses and improves efficiency. Additionally, since the converter operates at a high frequency, it can use smaller magnetic components such as inductors and transformers, which saves space and reduces cost.

By using Infineon's ZSC topology for your designs, you can effectively tackle the challenges of 48 V power distribution architecture and ensure that your system is efficient and cost-saving.

ZSC topology operation

ZSC is a resonant switch converter that operates in an over-resonant fashion. The inductor and capacitor (L-C) networks generate current and voltage waveforms that vary in a sinusoidal manner in each switching period. Optimum efficiency occurs when the switching frequency matches the LC resonant frequency so that switching is both zero voltage and zero current. While a perfect match is impossible, the ZVS inductor compensates the mismatch to force the voltage to zero before each MOSFET is switched on.?

In this scheme, the dominant contributors to loop inductance are the MOSFETs, specifically the clips, bond wires, and lead frame of their packages and the capacitors. The PCB also contributes to inductance around the loop. Due to the over-resonant operation and the addition of the ZVS inductor, perfect PCB layout is not required. However, for optimum efficiency, power shape routing should be robust to minimize I2R losses while having small commutation loops to minimize AC losses.?

Interested? Infineon offers PCB design recommendations to guide your physical design process to ensure peak performance and efficiency. Check them out below.

ZSC topology features

The main advantage of using ZSC in your designs is its ability to achieve high efficiency and density.?

This is achieved by the use of low voltage FETs with better Figure-of-Merit (Vout , 2 x Vout). The ZSC topology uses low voltage MOSFETs with a better figure-of-merit (FOM) to achieve higher efficiency, reduce switching losses, and enable high-frequency operation. To further minimize switching losses, ZSC uses soft-switching operation regardless of component tolerances and input voltage variation (LZVS provides soft-switching capability).

Furthermore, ZVS switching enables high switching frequency operation. By switching at zero voltage, the MOSFETs can handle higher frequencies, contributing to higher power density. The inherent drop current sharing feature simplifies the parallel operation and ensures that each ZSC contributes to the power transfer function, to increase the power output.

When choosing Infineon's ZSC in your designs, there is no need to use power magnetic components in the main current path. The LC resonant network provides the power transfer function, eliminating the large, expensive transformers, reducing the size and cost of the circuit.

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