LED Lighting Driver IC Introduction
Robin Liao
January 2011
http://www.richtek.com/LED
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
2
LED Lighting Driver IC Overview
3
LED Lighting Driver IC Overview
Isolated
E26/E27/E17, T5/T8
Par30/Par38, Street light
AC/CC
Non-isolated
GU10, E26/E27/E17
T5/T8, Par30/Par38
LED Lighting
With ET
MR16, AR111
DC/CC
Without ET
Street light, car light, desk
light, freeze light, projector
Emergency light
4
AC input to constant current
LED driver -- Isolated
5
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
6
Secondary side CC/CV controller
AC to CC – Isolated – secondary side CC/CV controller & dimming
RT8456
Single channel CC/CV controller
RT8457
Single channel CC/CV controller with dimming
RT8454
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
7
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
8
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
Dimming
Input
Programmable LED current through
60mV sense resister
Programmable OVP
Easily connected to different kinds
of primary side solutions
SOP-8
9
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
10
RT8454 AC-CC One-Stage Driving Scheme
11
Application Tip: RT8454Channel Number Extension
AC to DC Primary Side Circuit
AC Power Lines
Vaux
Opto-Coupler
12
Applications: Isolated E26/27, T5/T8, PAR30/38…..
•
Primary side solution example
1.
Flyback: R7912 (MOS inside) R7732(MOS ext.)

2.
Low PF, small output current ripple, good efficiency, good for no-PF requirement condition.
Valley-fill PFC+Flyback

3.
For small power (<10W), PF at 0.7~0.9 range. Small output current ripple, good for small
power and PF>0.7 application.
Active PFC+Flyback

4.
High PF (>0.9), lower efficiency, small output current ripple, good for high power design.
PFC single stage

5.
High PF (>0.9), low cost, need big output cap to reduce current ripple. Good for small power,
low cost design.
LLC

6.
High efficiency, high cost. Good for high power, high performance design.
Primary side constant current : R7710

Current accuracy is suffered from transformer accuracy. Good for current accuracy <+/-10%
application
13
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.
14
Valley-fill PFC+R7732+RT8456
15
AC input to constant current
LED driver -- Non-isolated
16
AC-CC non-isolated product roadmap
AC to CC – non-isolated
RT8458
High-side buck CC LED driver
RT8459
MOS
inside
High-side PFC buck CC LED driver
RT8460
High-side PFC inverting buck-boost CC
LED driver
RT8469
RT8468
17
RT8458 floating buck LED driver for non-isolated
application
Unique self-biasing floating buck
driver topology
True average LED current sense
High efficiency (>90% possible)
Cheap and simple external components
Very wide input voltage range
(16V~400V or higher)
Stable LED current over wide input
voltage range
Works with standard series drum choke
inductors
Support OVP & OCP
Small PCB to to fit GU10, E17…..
The best way to drive LEDs from AC power input!!
18
Three RT8458 applications
1.
Typical application


2.
Valley-fill PFC+RT8458


3.
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)
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.
Active PF + RT8458


Advantage
 High PF (>0.95)
 Good for high power, high PF design
Disadvantage
 Higher cost
 Lower efficiency
19
RT8458 typical application circuit
OVP option
Vout>31V
EMI improvement
20
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
21
RT8458 efficiency vs. LEDs
LED current=350mA
22
RT8459 High PF, floating buck LED driver for
non-isolated application
Unique self-biasing floating buck driver
topology
True average LED current sense for
high PF application
Cheap and simple external components
Very wide input voltage range
(16V~400V or higher)
Stable LED current over wide input
voltage range with high PF support
Works with standard series drum choke
inductors
Support OVP & OCP
Small PCB to to fit GU10, E17…..
23
RT8459 typical application circuit
24
RT8459 test result with universal input
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%
** Good line regulation for universal input with high PF support
** NOTED: Higher output current ripple & big output cap. for PFC single stage
design
25
How to choose the driving topology?
Need PFC?
NO
RT8458 typical application
Small output
current ripple?
NO
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
26
DC to CC Solution
27
Richtek’s Product -- DC to Constant Current
Converter
RT8450B
RT8453B
RT8470
RT8471
Controller
RT8452
RT8482
RT8480
RT8488
• Application
•
•
•
•
MR16, AR111
Street light, Desk light, Freeze light
Car light, Projector lamp
Solar lighting, Emergency light
28
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
29
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
(%)
RT8450A
4.5~40+Zener drop
50
UP to 1.5A
> 95
1
Buck,Boost,BuckBoost
RT8450B
4.5~40+Zener drop
50
UP to 1.5A
> 95
1
Buck,Boost,BuckBoost
RT8452
4.5~36+Zener drop
48
External MOSFET
> 95
1
Buck,Boost,BuckBoost
RT8453
4.5~40
38
UP to 1.5A
> 95
1
Buck
RT8480
4.5~40+Zener drop
Limited by
external
MOSFET
External MOSFET
> 93
1
Boost, SEPIC
RT8482
4.5~36+Zener drop
48
External MOSFET
> 95
1
Buck,Boost,BuckBoost
RT8470
7~30
28
UP to 1A
>95
1
Buck
RT8488
7~36+Zener drop
Limited by
external
MOSFET
External MOSFET
>92
6
Boost
LED
String
Topology
30
Applications
31
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
32
Application: MR16 (RT8470 BUCK---a typical low cost design)
33
MR16—RT8470 Buck
CH1: Vin
CH4: Iin
Average LED current will be different
with different ET connected
CH1: LED voltage
CH4: LED current
34
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
35
Application: RT8453 MR16
CH1: Vin
CH4: Iin
CH1: LED voltage
Very stable LED current with different
ET connected
CH4: LED current
36
Applications: Street Light (I)
AC
Power
PFC
+
AC2DC
Primary
Side
Circuit
RT8454
….
Vbase
6 CHs
Opto
Vaux
MCU
FBx6
Dim
Gx6
CSx6
Other
Control
Signals
6 Current
Sources
….
NTC
Sense LED Temp.
37
Applications : Street Light (II)
AC Power
DC 12V~48V
RT8488
PFC AC2DC
Vaux
(Either one or both)
LiFePO3
Batteries
Solar Cell
….
6 CHs
Sense
MCU
Other
Control
Signals
Gbias
Gate
Dim
FBx6
NTC
Sense
LED
Temp.
Gx6
CSx6
6 Current
Sources
….
38
Applications : Street Light (III)
AC Power
DC 12V~48V
RT8480
PFC AC2DC
(Either one or both)
Vaux
Gbias
Gate
Sense
LiFePO3
Batteries
Dim
MCU
PWMO
Solar Cell
Up to
40xLEDs
(160V)
Other
Control
Signals
Thermal
Feedback
IFB
Dimming
Current FB
NTC
Sense LED Temp.
39
Application: Thermal protection
40
Selection guide
41
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
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
Automotive Application
42
http://www.richtek.com/LED