LED Lighting Driver IC Introduction

Robin LiaoJanuary 2011

http://www.richtek.com/LED

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Contents

LED Lighting Driver IC Overview

AC input to constant current LED driver -- Isolated

AC input to constant current LED driver -- Non-isolated

DC to CC Solution

Applications

Selection Guide

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LED Lighting Driver IC Overview

4

LED Lighting Driver IC Overview

LED Lighting

AC/CC

DC/CC

Isolated

Non-isolated

With ET

Without ET

E26/E27/E17, T5/T8 Par30/Par38, Street light

GU10, E26/E27/E17 T5/T8, Par30/Par38

MR16, AR111

Street light, car light, desk light, freeze light, projector Emergency light

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AC input to constant current LED driver -- Isolated

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AC Input Solution -- Isolated

• Application• E27, GU10 …. Bulb, Par 30, Par 38

• T5, T8 …. Light bar, Freeze light

• Street light, Desk light…

• Richtek advantage• High-precision constant current control to limit current accuracy in +/-

5% range on mass production.

• Small package and high integrated solution with less external components to fit into a small bulb or light bar

• Very low quiescent current

• Dimming on secondary side to provide better accuracy

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Secondary side CC/CV controller

AC to CC – Isolated – secondary side CC/CV controller & dimming

RT8456

RT8454

RT8457

Single channel CC/CV controller

Single channel CC/CV controller with dimming

Multi-channel CC/CV controller with dimming

Easily work with any kind of primary side topology.

Provide high precision LED current.

LED current accuracy does not vary with the accuracy of transformer.

OVP support

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RT8456 Secondary-side constant Current Controller

Secondary side LED current regulation

Support LED voltage up to 45V

High accuracy LED current threshold control over wide input voltage and temperature range

0.6mA operation current

Programmable LED current through 60mV sense resister

Programmable OVP

Easily connected to different kinds of primary side solutions

TSOT 23-6

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RT8457: Dimmable secondary side constant current controller

LED voltage up to 45V

Support Triac dimming, PWM dimming, analog dimming

High accuracy LED current threshold control over wide input voltage and temperature range

Programmable LED current through 60mV sense resister

Programmable OVP

Easily connected to different kinds of primary side solutions

SOP-8

Dimming Input

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RT8454 AC-CC 6-Ch Current Regulators

Vcc up to 50V

Programmable channel current

3% current sense amplifier input offset

Easy dimming

Programmable soft start and OVP

Automatic detecting unconnected AND/OR broken channel to avoid output over voltage

Vcc under voltage lockout and Thermal shutdown

One LDO controller embedded

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RT8454 AC-CC One-Stage Driving Scheme

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Application Tip: RT8454Channel Number Extension

Vaux

AC

to DC

Prim

ary Side C

ircuit

Opto-Coupler

AC

Pow

er Lines

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Applications: Isolated E26/27, T5/T8, PAR30/38…..

• Primary side solution example1. Flyback: R7912 (MOS inside) R7732(MOS ext.)

Low PF, small output current ripple, good efficiency, good for no-PF requirement condition.

2. Valley-fill PFC+Flyback For small power (<10W), PF at 0.7~0.9 range. Small output current ripple, good for small

power and PF>0.7 application.

3. Active PFC+Flyback High PF (>0.9), lower efficiency, small output current ripple, good for high power design.

4. PFC single stage High PF (>0.9), low cost, need big output cap to reduce current ripple. Good for small power,

low cost design.

5. LLC High efficiency, high cost. Good for high power, high performance design.

6. Primary side constant current : R7710 Current accuracy is suffered from transformer accuracy. Good for current accuracy <+/-10%

application

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Applications: Isolated E26/27, T5/T8, PAR30/38…..

• Secondary side solution• RT8456, RT8457, RT8454 can work with any kind of primary side

topologies and become constant current LED drivers except (6)

• Maintain current accuracy at +/-5% independent of the variation of transformer

Non-dimmable: Primary side + RT8456 Dimmable: (bleeder)+ Primary side + RT8457

• Support Triac dimming with external bleeder added

• Support PWM, analog, wireless… dimming on secondary side with accurate current control.

• Using MCU for Traic dimming can provide the best compatibility of dimmer.

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Valley-fill PFC+R7732+RT8456

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AC input to constant current LED driver -- Non-isolated

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AC-CC non-isolated product roadmap

RT8458

AC to CC – non-isolated

RT8459

High-side buck CC LED driver

High-side PFC buck CC LED driver

RT8460High-side PFC inverting buck-boost CC LED driver

RT8469

RT8468

MOS inside

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RT8458 floating buck LED driver for non-isolated application

The best way to drive LEDs from AC power input!!

Unique self-biasing floating buck driver topologyTrue average LED current senseHigh efficiency (>90% possible)Cheap and simple external componentsVery wide input voltage range (16V~400V or higher)Stable LED current over wide input voltage rangeWorks with standard series drum choke inductorsSupport OVP & OCPSmall PCB to to fit GU10, E17…..

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Three RT8458 applications1. Typical application

Advantage Very good line regulation. LED current variation between 110V/220V AC input is

minor. (<+/-2%) Small input/Output cap Simple external components Good for application do not need PFC.

Disadvantage Low PF (About 0.6)

2. Valley-fill PFC+RT8458 Advantage

PF at 0.7~0.9 for low power application (<10W) Good for small power, PF>0.7 design

Disadvantage Big cap for high power or high PF application.

3. Active PF + RT8458 Advantage

High PF (>0.95) Good for high power, high PF design

Disadvantage Higher cost Lower efficiency

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RT8458 typical application circuit

OVP option

Vout>31V

EMI improvement

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High-efficiency universal input design

Vin.ac (V) Pin(W) V-LED (V) I-LED (A) Pout (W) Eff. (%)

90 10.25 36.20 0.257 9.303 90.76

110 10.22 36.29 0.257 9.327 91.26

130 10.29 36.19 0.257 9.300 90.38

180 10.19 36.02 0.257 9.257 90.85

220 10.21 36.02 0.257 9.257 90.67

260 10.23 36.06 0.257 9.267 90.59

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RT8458 efficiency vs. LEDs

 

LED current=350mA

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RT8459 High PF, floating buck LED driver for non-isolated application

Unique self-biasing floating buck driver topologyTrue average LED current sense for high PF applicationCheap and simple external componentsVery wide input voltage range (16V~400V or higher)Stable LED current over wide input voltage range with high PF supportWorks with standard series drum choke inductorsSupport OVP & OCPSmall PCB to to fit GU10, E17…..

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RT8459 typical application circuit

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RT8459 test result with universal input

** Good line regulation for universal input with high PF support

** NOTED: Higher output current ripple & big output cap. for PFC single stage design

8459 Vout=44V//200mA/15LEDs

Vin.ac (V) Vo (V) Io (mA) Pin (W) Po (W) PF Eff. (%) current offset (%)

90 43.33 194 9.3 8.41 0.980 90.39 -1.02%

110 43.37 196 9.26 8.50 0.981 91.80 0.00%

130 43.35 195 9.19 8.45 0.985 91.98 -0.51%

180 43.31 191 9.03 8.27 0.972 91.61 -2.55%

220 43.36 194 9.23 8.41 0.955 91.14 -1.02%

264 43.41 196 9.42 8.51 0.932 90.32 0.00%

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How to choose the driving topology?

Need PFC? RT8458 typical applicationNO

Small output current ripple?

RT8459 typical application

Valley-fill PFC+RT8458 good for small power, PF in 0.7~0.9

Active PFC + RT8458, good for high power design or PF>0.9

NO

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DC to CC Solution

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Richtek’s Product -- DC to Constant Current

Converter

Controller RT8480RT8452

RT8450B

RT8482

RT8453B RT8470

RT8488

• Application• MR16, AR111• Street light, Desk light, Freeze light• Car light, Projector lamp• Solar lighting, Emergency light

RT8471

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Richtek’s Product -- DC to Constant Current

• Richtek advantage• Cover wide input/output voltage range and support different

kinds of topology include buck, boost, buck-boost, SEPIC• Accurate output current over wide temperature range• Stable output current vs. input/output voltage change• Easy Dimming : Analog, PWM or PWM Converting to Analog

with One External Capacitor, Triac dimming• Support high-speed PWM dimming up to 50kHz• Better reliability with bipolar process• Cost competitive

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Selection Guide for DC to CC Products

DC Input to Constant Current

Part Number Vin(V) Max Vout(V)LED current per

string (mA)

Max Efficie

ncy(%)

LED String

Topology

RT8450A 4.5~40+Zener drop 50 UP to 1.5A > 95 1Buck,Boost,Buck-

Boost

RT8450B 4.5~40+Zener drop 50 UP to 1.5A > 95 1Buck,Boost,Buck-

Boost

RT8452 4.5~36+Zener drop 48 External MOSFET > 95 1Buck,Boost,Buck-

Boost

RT8453 4.5~40 38 UP to 1.5A > 95 1 Buck

RT8480 4.5~40+Zener dropLimited by

external MOSFET

External MOSFET > 93 1 Boost, SEPIC

RT8482 4.5~36+Zener drop 48 External MOSFET > 95 1Buck,Boost,Buck-

Boost

RT8470 7~30 28 UP to 1A >95 1 Buck

RT8488 7~36+Zener drop Limited by external MOSFET

External MOSFET >92 6 Boost

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Applications

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Applications: MR16

• Major solutions• RT8470 low cost solution

• Lowest cost solution• About 70% Electronic Transformer (ET) compatibility• Different brightness with different ET connected• Very popular in China

• RT8453 high ET compatibility solution• Very high ET compatibility• Keep same brightness with different ET connected

• Special applications• RT8453 dimmable solution

• Dimmable with minor cost added from the previous solution• Same performance as the previous solution without dimmer connected• ET limited• With selected ET, about 50% dimmer can dim pretty well

• RT8453 non electrolytic cap solution• High ET compatibility with square wave output

• RT8453 three-step dimming• Support three-step dimming with three-step dimming controller added• Use ON/OFF break to switch between three steps

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Application: MR16 (RT8470 BUCK---a typical low cost design)

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MR16—RT8470 Buck

CH1: Vin

CH4: Iin

CH1: LED voltage

CH4: LED currentAverage LED current will be different with different ET connected

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Application: RT8453 MR16

Excellent electronic transformer compatibility

High efficiency, stable output LED current

Support Triac dimming with selected ET and Dimmer but no extra cost added

No flicker with most of the ET

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Application: RT8453 MR16

CH1: Vin

CH4: Iin

CH1: LED voltage

CH4: LED currentVery stable LED current with different ET connected

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Applications: Street Light (I)

AC Power

Other Control Signals

MCU

NTC

Sense LED Temp.

Gx6

Vbase

Dim

FBx6Vaux 6 Current

Sources

RT8454

CSx6

….6 CHs

….

PFC +

AC2DCPrimary

SideCircuit

Opto

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Applications : Street Light (II)

PFC AC2DC

Solar Cell

LiFePO3 Batteries

AC Power

Other Control Signals

MCU

NTC

Sense LED

Temp.

Gx6

DC 12V~48V

Gate

Sense

Dim

FBx6

GbiasVaux

6 Current Sources

RT8488

CSx6

….6 CHs

….

(Either one or both)

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Applications : Street Light (III)

PFC AC2DC

Solar Cell

LiFePO3 Batteries

AC Power

Other Control Signals

MCU

NTC

Sense LED Temp.

Thermal Feedback

DC 12V~48V

Gate

Sense

Dim

PWMO

GbiasVaux

Dimming

RT8480

Up to 40xLEDs (160V)

IFB Current FB

(Either one or both)

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Application: Thermal protection

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Selection guide

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LED Lighting Selection Guide Sorted by Application

LED Lighting Selection Guide Sorted by Application

Application Topology Richtek Solution

Solid-State Lighting AC or DC Input

MR16 Buck, Buck-Boost, Boost RT8450B,RT8482,RT8453, RT8470

AR111 Boost RT8450B,RT8482

GU10, E27,PAR30,PAR38 Flyback, non-isolated RT8458, RT8456, RT8457

Office Lamp Boost, Flyback, non-isolated RT8450B,RT8482, RT8456, RT8458

Decoration Light Boost RT8450B,RT8482

Street Light, Solar Light Buck, Boost, flyback RT8450B,RT8482,RT8488,RT8454

Emergency Light Boost RT8450B,RT8482

T5, T8 Light Bar Flyback, non-isolated RT8456, RT8457, RT8458

RGB Light Buck RT8453, RT8470

Freeze Light Buck, Flyback, non-isolated RT8450B,RT8453, RT8456, RT8470, RT8458

Projector Synchronous Buck RT8452

Automotive Application

Interior Light Buck, SEPIC, Buck-Boost RT8450B,RT8482, RT8488, RT8480

Exterior Light Buck, SEPIC, Buck-Boost RT8450B,RT8482, RT8488, RT8480

Automotive Light Buck, SEPIC, Buck-Boost RT8450B,RT8482, RT8488, RT8480

http://www.richtek.com/LED