Cirrus-logic AN364 Manuel d'utilisateur télécharger pdf (Page 3)

AN364

AN364REV3 3

2 Introduction

This application note is a guide to designing a Solid State Lighting (SSL) LED lamp circuit using Cirrus Logic's

CS1610/11. The first half of the document presents a step-by-step design procedure for calculating the required

components for each stage of the system. The second half of the document supports the design effort by showing

an example of a CS1611 design. The CS1611 example will be based on the Cirrus Logic CRD1611-8W reference

design. See the CS1610/11/12/13 TRIAC Dimmable LED Driver IC data sheet for more details about the CS1610/11

IC. See the CRD1610-8W 8 Watt Reference Design and CRD1611-8W 8 Watt Reference Design data sheets for

more details regarding the reference design.

2.1 Definition of Symbols

2.2 Definition of Acronyms

Symbol Description

Switching frequency

TT Switching period

T1 Primary FET ‘ON’ time

T2 Secondary rectifier diode conduction time

T3 Time when the FET and diode are OFF

D Duty ratio (T1/TT)

Reflected

Voltage across secondary winding reflected onto primary

CLAMP

Primary clamping voltage above boost output voltage (V

BST

)

PK(FB)

Peak current in primary-side FET

FBGAIN

A resistor used to program the switching period TT

Sense

Primary current sense resistor

PK(BST)

Maximum boost inductor current

Flyback transformer primary inductance

BST

Boost inductance

BST

Boost output voltage

Flyback transformer turns ratio N

OUT

Secondary output voltage DC = the LED string supply voltage

OUT

Load power = Power to the LED string

 Power stage efficiency

Acronym Description

PFC Power Factor Correction

OVP Overvoltage Protection

eOTP External Overtemperature Protection

OCP Overcurrent Protection

iOTP Internal Overtemperature Protection

OLP Open Loop Protection

LED Light Emitting Diode

TXF Transformer

TRIAC

TRIode for Alternating Current, which is an electronic component that can conduct current in

either direction when it is triggered. It is formally called a bidirectional triode thyristor.

SSL

Solid State Lighting. Refers to a type of lighting that uses semiconductor LEDs as a source of

illumination rather than electrical filaments, plasma, or gas.

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