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Application Note

CS1501 & CS1601:

DRIVING THE ZCD PIN FROM THE MOSFET DRAIN

1. Introduction

The CS1601 is designed with ZCD (zero-current detection), providing the controller with the capability to turn on the MOSFET

when the current through the boost inductor is close to zero. This can also be described as valley/zero crossings switching. This

is implemented by adding a sense winding on the PFC choke to detect the current.

If the addition of an auxiliary winding on the boost inductor is a problem due to design or manufacturing constraints, an alternative

method for implementing this function is presented below.

2. Standard ZCD Configuration

The standard configuration for the CS1501 & CS1601 is an auxiliary winding is added to the PFC boost inductor to provide zero-

current detection (ZCD) information.

Figure 1. ZCD Using Auxiliary Winding on PFC Boost Inductor

An auxiliary winding is added to the PFC boost inductor to provide zero-current detection (ZCD) information. The ZCD compar-

ator looks for the zero crossing on the auxiliary winding and switches when the auxiliary voltage is below zero. Switching in the

valley of the oscillation minimizes the switching losses and reduces EMI noise.

For a full description of ZCD operation, see the CS1501 & CS1601 data sheets.

8 1

Boost Diode

Boost

FET

CS1501

CS1601

GDZCD

IFB

GND

CSIAC

VDD

STBY

rect

link

33pF

AN356

APR ‘11

AN356REV1

1 2 3 4

Résumé du contenu

Page 1 - Application Note

Page 2 - 2 AN356REV1

AN3562 AN356REV13. Alternative ConfigurationIt is possible to implement ZCD with a resistor divider from the drain of the PFC MOSFET. See Figure 2.Fig

Page 3 - 4. Summary

AN356AN356REV1 3Figure 3. ZCD Performance — Operation at 100% Load, 108 VACFigure 4. ZCD Performance — Operation at 50% Load, 108 VAC4. SummaryAn al

Page 4 - Revision History

AN3564 AN356REV15. Revision History Revision Date ChangesREV1 APR 2011 Initial Release.Contacting Cirrus Logic SupportFor all product questions and i

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Cirrus-logic AN356 Manuel d'utilisateur

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Résumé du contenu

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