CL88020 datasheet(17/47 Pages) MICROCHIP

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CL88020

120 VAC OFFLINE LED DRIVER

EVALUATION BOARD USER’S GUIDE

 2017 Microchip Technology Inc.

DS50002611A-page 17

Chapter 2. CL88020 120 VAC Offline LED Driver

Evaluation Board Installation and Operation

2.1

INTRODUCTION

CL88020 120 VAC Offline LED Driver Evaluation Board User’s Guide is intended to

drive a long string of low-current LEDs directly from the AC mains. A basic driver circuit

consists of CL88020, six resistors and a bridge rectifier. Two to four additional compo-

nents are optional for various levels of transient protection, also with a low-price NTC

to assure remote overtemperature protection (OTP). No capacitors, EMI filters or

power factor correction circuits are needed.

A string of series/parallel LEDs is tapped at four locations. Four linear current regula-

tors sink current at each tap through a single control point and are sequentially turned

on and off. High efficiency is achieved by shutting off upstream regulators when down-

stream regulators achieve regulation. This makes controlling overall input current eas-

ier than trying to control multiple current paths, thereby tracking the input sine wave

voltage. Voltage across each regulator is minimized when conducting, providing high

efficiency. It implements a self-commutation technique using only the tap currents; this

technique inherently provides smooth transitions from one regulator to the next, without

relying on tap voltages or the rectified AC to coordinate the transitions. The current

waveform can be tailored to optimize for input voltage range, active line/load regulation,

output power/current, efficiency, power factor, THD, dimmer compatibility and LED uti-

lization. With the addition of an RC network, the driver is compatible with a wider range

of phase-cut dimmers. The data sheet includes a description of how the driver

operates, with design guidelines and examples.

2.1.1

CL88020 LED Driver Evaluation Board Features

The CL88020 LED Driver Evaluation Board (ADM00766) has the following features:

• Input Voltage: 120 Vrms +/-15%, 50/60 Hz

• Typical Output Capability: up to 130 mA

• Efficiency: Over 83%

• Max Output Power: 8.5W (depends on the cooling provided)

The CL88020 LED Load Board (ADM00767), has the following features:

•Contains 10 LEDs (GW P9LR31.EM) grouped in 4 taps

• An 8-wire flat cable input connector

• One NTC for overtemperature protection

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