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What is Zero volt switching (ZVS)? Why is the loss reduced by ZVS?


AC/DC ConverterFunction

Zero volt switching (ZVS) means the operating condition of FET switching.

FETs are used as switches which are turned on and off by forcing voltage difference between the gate and source.  When the voltage difference between the drain and source of FETs is zero volt, the voltage between the gate and source is changed by a circuit, in this case, the operation is called as zero volt switching.

In general switching, the voltage between the drain and the source of FETs is not zero volt.  Therefore when the FETs turn on and off, a through current is generated, which causes a loss.

In the zero volt switching, there is no through current and high efficiency can be achieved.

What is ZVS Control?

Synchronous Buck DCDC Converter

Synchronous Buck DC/DC Converter

A is the ideal waveforms of voltage (Vds) and current (Id).

B is the actual waveforms of Vds and Id at FET switching. When the FETs turn on/off, there are losses due to voltage and current overlap.

C is the waveforms of Vds and Id using the edge resonance control of ZVS, which can eliminate any overlap between voltage and current, and minimize losses.

Typically, fast switching operation generates high frequency noise that can lead to system noise and EMI issues; however, using Ricoh’s R1700 can significantly reduce switching noise and EMI.

A. Ideal Switching Operation

[A] Ideal Switching Operation

B. General Switching Operation

[B] General Switching Operation

C. ZVS Switching Operation

[C] ZVS Switching Operation

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