Summary - All LEDs are dimmable, the issue is how the driver is designed to be dimmed - Legacy wall dimmers present a unique set of compatibility issues and challenges - New standards are being established like NEMA SSL7 to support new dimmer and bulb designs - “Smart dimmers” can enable dimming for any application without legacy interface issues

1. 1 Confidential Proprietary
Dimmable LED Driver Solutions

2. 2 • Template • Nov-12 Confidential Proprietary2
Basic LED Dimming Concepts
Digital
– Pulse Width Modulation(PWM)
– Can dim <5% depending on driver
– Less wavelength shift (still ∆Tjº)
Analog
– Amplitude Modulation(AM)
– Highest Efficiency
– No Flicker, more color shift
LED “A”
∆CCT = 411K
350-1500mA;
35-105˚C
LED “B”
∆CCT = 31K
350-1500mA;
35-105˚C
OutputCurrent
Time
Source:OSRAM

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Dimming Light Sources
• All light sources shift in color when dimmed
• Many reasons to adjust light level
– Situation control (reading/watching TV/etc)
– Energy saving (Occupancy/Daylight harvesting)
– Color tuning or mixing
• Control Interface key to dim LED Driver
Source: NEMA LSD-60

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Dimming Control Interfaces
• Control part of AC Power
– Leading Edge Control (Triac)
– Trailing Edge Control (MOSFET)
• Control interface separate from Power Delivery
– 0/1-10 V (IEC 60929)
– DALI (IEC 62386) or custom PWM
– Bluetooth/WiFi/Zigbee/Proprietary
– Infra-red
• Integrated Control
– Ambient light sensing
– Occupancy/motion sensing

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AC Line Dimming
• Line dimming especially TRIAC is of high interest for retrofit LED lighting
and TRIAC dominates in US as no special wiring is needed
• Compatibility requires special design effort in LED Driver
– Driver needs to look like a resistive load (high power factor)
– EMI filter has to be designed and optimized, big issue with input surge current
– Driver must present minimum load for driver compatibility
Leading Edge (TRIAC)
ELV Dimmer Wiring
Trailing Edge (ELV)

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Dimmable Bulbs in US Households
• 3 way have 2 dimming steps
– Step 1 – Range 68-85%
– Step 2 – Range 15-32%
Source: CFL Market Profile, September 2010, Energystar
• ~ 150 m installed in North America
• ~ 100 m installed in Western Europe
Dimmer Types in USA

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Review of TRIAC Dimmer Operation
• TRIAC must see a minimum
latching current (Io) to stay on
• Given abrupt turn on of the TRIAC
there is ringing in the dimmer and
the load
• Problem is big since most LED
drivers look capacitive (EMI filter)
• If total load current drops below
holding current (IH), TRIAC will turn
off
Current in
TRIAC with
resistive
load

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TRIAC Latching & Holding Current
Even an incandescent can cause a dimmer to flicker with
added capacitance (100nF Capacitor || 15w Bulb)
Flicker is caused when dimmer fires
multiple times per cycle

9. 9 • Template • Nov-12 Confidential Proprietary9
Designing for TRIAC Dimmer Compatibility
• Step 1: Driver should look as much like a resistive load
– PF ~ 1
– Very little line to neutral capacitance
– Load current must be enough to stay above holding current of Triac
• Step 2: If driver has capacitance due to EMI filter, extra
latching current may be needed to deal with ringing in EMI
filter
• Step 3: Driver may need to switch in artificial load to present
extra holding current to dimmer, dependent on:
– LED Driver Load
– Dimming Curve
– Range of dimmer compatibility

10. 10 • Template • Nov-12 Confidential Proprietary10
Device Application Topology Input Voltage Input Power Power Factor THD
NSIC2030B LED Lighting Linear 100 to 130 Vac 6.7 W 0.98 22%
Design Note DN05046
Parallel to Series on Low Mains (120 Vac)
Phase dimmer compatible
Efficiency ~72% (3 LEDs/string) to 94% (4 LEDs/string)
CREE MX-6S LED, VF = 20 V/LED
Small
Capacitor
2.2 nF

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How Does this Approach Work?
No Dimmer
With Dimmer
100V
MOSFET

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Principle Scales up for 230 Vac Input
all Bipolar Solution, Dimmer Compatible
Design Note DN05047

13. 13 • Template • Nov-12 Confidential Proprietary13
PFC Flyback EMI Filter Optimization
•Excess EMI filter capacitance degrades power factor
•Larger inductors provide filtering with less effect on PF and resistors across
inductors dampen resonance
• Moving transient limiter RV1 after inductors can increase filter effectiveness
•C1 normally controls EMI, but can interfere with TRIAC dimmer so this is can be
reduced in size or eliminated and inductor values L1, L2, and L3 should be increased
•Open magnetic path inductors (drum type) can create audible noise with TRIAC
dimmer so closed-path or shielded inductors should be used

14. 14 • Template • Nov-12 Confidential Proprietary14
NCL30000 TRIAC调光
NCL30000 Triac Dimming
通过改变调光器位置来在350 mA至1.7 mA调光的性能
Dimming performance from 350 mA to 1.7 mA by changing dimmer position
施加电压 Applied voltage
@ 100 V/div
线路电流 Line current
@ 333 mA/div

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Example Design – LV5011
Non-isolated TRIAC dimmable buck-boost
Snubber in input
creates extra current
during input voltage step

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TRIAC Shimmer due to Holding Current
These current levels can be different
causing “shimmer” (50 or 60 Hz content)

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Optional Bleeder can add Holding/Bleed
Current for Low Power Applications
•ACS Comparator senses input
line voltage level
• When input voltage is too low,
external load is added which
presents extra current to
TRIAC

18. 18 • Template • Nov-12 Confidential Proprietary18
LV5029M
MOS
FET
REF
OUT
CS
MOS
FET OUT2
ACS
LV5026MLV5011MLV5012M
HV Vin
◆LV5026
Adjustment Dimmer
・External Bleeder control
◆LV5011
Adjustment Dimmer
・Built-in POWER FET
（LV5026＋POWER FET）
◆LV5012
Adjustment Dimmer
・Built-in Start-UP HV FET
・Built-in TRIAC Stabilized
LV5011LV5026LV5012
HV MOSFET
BLEEDER FET
TRIAC Driver Functional Comparison

19. 19 • Template • Nov-12 Confidential Proprietary19
Unique Features Application DataBenefits
Market & Applications
Others Features
• TRIAC Dimming Light Bulb
• Dimmable LED Downlights
・PWM Topology
・Built‐in Start UP MOSFET
・Built‐in BLEEDER MOSFET
for TRIAC light control
• Holding Current Circuit
Package Information
・Good adaptability
of TRIAC Dimmer
・ Improvement Power factor
・Reduced # of external
components
・Isolation or Non‐Isolation
・Low noise switching System
Step Drive switching & 5 Stage skip Frequency
・Integrated Triac Dimmer Compatibility
・ Improvement power factor
・LED current line regulation ±3% (180V‐264V)
・Built‐in TRIAC holding current function
・Over current protection
・Thermal Shut down (TSD）
LV5012MD
Single Stage (PSR) LED Dimming Controller
MFP14S
Internal
BLEEDER
&HV FET

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“Smart Dimmer” Issues
• Night Light and Smart Dimmers
– MCU steals current from line to stay
powered even when dimmer is off
– LED Driver must provide a current
path all the time for proper operation
Dimmer Operating
ILOAD
Vin
Dimmer Off “60W Bulb”

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Dimmer Compatibility
• Very little standardization in place globally
• LED lamp vendors and dimmer manufacturers have to test
for general compatibility
• For US Market there has been some standards developed
– NEMA SSL-6 … Recommended Dimmer Characteristics
– NEMA SSL-7A … Future Compatibility (New Dimmers/New Lamps)
Philips LED Bulb
Example

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NEMA SSL6 Compatibility
NEMA SSL-6
Bulb A
Bulb B
32% Light
10% Light
• LED drivers can have very different
dimming shapes
• NEMA SSL-6 sets requirements
targeting incandescent shape
• Two bulbs both compliant could
have dramatically different light
output at low conduction angle

23. 23 • Template • Nov-12 Confidential Proprietary23
New 2013 NEMA SSL7A Specification
Establishes Dimming Corner Points for New Dimmers/Bulbs
Note: MLO = Maximum Light Output (no dimmer connected)
• @ 130 degrees, light output must be > 75%
• @ 40 degrees, light output must be < 30%
• @ 45 degrees, there must be “visible” light

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What about “Smart Lighting”
• LEDs are easy to control and dim
• Electronics opens up new functions
– Built-in occupancy sensor
– Power savings based on ambient light
– Wireless interfaces eliminate need to
change switches or wiring
• Power saving techniques
• Convenience and security
Ambient Light
Sensor
“Smart Ready”
Dimmable
LED Driver
Passive IR
Occupancy
Sensor
Wireless
Receiver
IR
Receiver

25. 25 • Template • Nov-12 Confidential Proprietary25
NCL30082 Smart Dimming Interface
• Additional Features
– Smart Dedicated Analog / PWM dimming Input
– Programmable temperature foldback (TF) and over voltage protection (OVP)
OVP
TF
ZCD
CS
GND
VIN
VCC
DRV
SD
DIM

26. 26 • Template • Nov-12 Confidential Proprietary26
NCL30082 Dimming Control Pin Operation
• The DIM pin combines analog and PWM dimming capability.
• If a signal lower than VDIM100 is applied, the controller decreases the
output current proportionally to the applied voltage.
• If a signal higher than VDIM100 is applied to the DIM pin, the controller
enters the PWM dimming mode and enables the drive pulses when
VDIM > VDIMA.
• Can also provide programmable soft start (RC from Vcc)
• PWM and analog dimming can be combined also

27. 27 • Template • Nov-12 Confidential Proprietary27
NCL30082 Analog Dimming
Iout
VDIM
• Iout of 5 LED load (purple), DIM input is ramped down slowly from 3 V to 0.75 V (Green)
• VDIMA 100% level is 2.45V (typical)

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NCL30083 Log-Step Dimming
• Cost free dimming without a special dimmer switch
• Target is control range of a triac < 10%
• Output current decrease in discrete steps each time a
low input voltage condition is detected.
Dimming Step Iout
ON 100%
1 70%
2 40%
3 25%
4 10%
5 5%
Test Results with LEDTarget Output

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How Log-Step Dimming is Done
• The VCC capacitor
must be able to
supply the controller
during a short brown-
out condition (split
supply for VCC)

30. 30 • Template • Nov-12 Confidential Proprietary30
Summary
• All LEDs are dimmable, the issue is how the driver is
designed to be dimmed
• Legacy wall dimmers present a unique set of compatibility
issues and challenges
• New standards are being established like NEMA SSL7 to
support new dimmer and bulb designs
• “Smart dimmers” can enable dimming for any application
without legacy interface issues

31. 31 • Template • Nov-12 Confidential Proprietary31
Appendix

32. 32 • Template • Nov-12 Confidential Proprietary32
Problem Description Driver Response
Flashing/Flickering Repeated flashing, typically at dimmer upper range
Add holding current, reduce
EMI filter size
Poor Control Range
Cannot dim to desired light level, different response
with different dimmers
Accelerated Dimming
Curve, equalizes bad
dimmers
Light Variation
Line and load changes cause bulbs to get brighter or
dimmer
Limitation of constant
power approach, closed
loop current regulation
LED on when
dimmer is OFF
Problem of smart dimmers needing current to keep
memory alive
Active Bypass Path to
Dimmer
Low Frequency
Light Variation
Light “variation” at lower dimmer position
Add shimmer reduction
compensation
Night Light in
Dimmer does not
work
LED Driver does not present a good DC path to the
dimmer
Active Bypass Path to
Dimmer
Common TRIAC Dimmable LED Issues