The Crazy World of LED Dimming and Control

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Or…

Why The #@*% Is It Doing That?!

• How LEDs work - understanding the basics

• How LEDs dim - different approaches

• What happens when LEDs dim - color, life, efficiency, flicker, noise

• Matchmaking - how to get LEDs, drivers and controls to work together

• Application do’s and don’ts

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Natalia Lupacheva

Systems Engineer

ETC, Middleton, WI

Greg SmithDirector of Product Development

Tivoli, Tustin, CA

Presented by:Gary DulanskiPrincipal

The Dulanski Group, NYC

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Outline

Gary Dulanski

• Basics of LEDs: how they work, voltages and currents, AC and DC

• Define drivers and power supplies• Dimming retrofit LED lamps versus LED fixtures• Light output vs energy saving when dimming LEDs• LED life when dimming• LED color when dimming

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Outline

Natalia Lupacheva

• Dimmer - Driver - LED interactions• Phase Control dimming - forward and reverse• AC + Control Signal dimming - 0-10v, DALI, DMX• Dimming techniques - Pulse Width Modulation, Constant Current Reduction

• Flicker issues• Turn-On behaviors• Dimmer load restrictions • NEMA SSL-7A Standard

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Outline

Greg Smith

• Visual effects• Range of control, minimum output• What happens to color when you dim LEDs• Advantages when using LEDs vs other sources• Range of LED whites and colors• Variable / Dynamic white color control• Warm shifting• Color tuning• Lumens vs color• Automated controls

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Q & A

• Clarifications anytime

• Big Questions at the end

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Basic Electricity• Conductors

• Insulators

• Voltage = Pressure

• Current = Flow

• Load Has Resistance

• Current = V / R

• Power = V x I

• DC = Direct Current, Current Flows One Way

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AC• AC = Alternating

Current, Current Flows Two Directions

• Frequency Hz

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Diodes• SemiConductor

• Diode Conducts Only One Way

• Threshold Voltage To Conduct

• Rectifies AC

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Light Emitting Diodes

• Electroluminescence

• 1962 Red LED - gallium arsenide phosphide

• Indicator Lights

• Fast - Fiber Optic Telecommunication

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LED Circuit• Threshold Voltage To Overcome ~1-3 V

• Limit Current

• Only DC

• Efficiency; consider loss in the limiter

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Series LED Circuit• Multiple LEDs Connected

• Higher Supply Voltages

• Efficiency, Less Loss

• One Fails = All Go Out

• Think: Turn On Threshold and Dimming

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Parallel LED Circuit

• Multiple LEDs

• One Fails, Others Keep Working

• Think: Lower Voltage, Higher Current

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LED Array

• Series + Parallel Together

• Screen Backlight Vs Individually Controlled LEDs In A Video Display

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Driver• Transform Voltage

• Convert AC To DC

• Drive Correct Current To LEDs

• Smooth Output

• Compensate For Power Fluctuations

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LV Power Supply + Driver

• Line Voltage Converted To Low Voltage Separately, Low Voltage Fed To Fixture

• Driver Circuitry Built Into Fixture

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LED Retrofit Lamp

• Driver Built In

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Dimmable Driver

• Transform Voltage

• Convert AC To DC

• Vary Current To LEDs

• Smooth Output

• Compensate For Power Fluctuations

• Don’t Misbehave

• Line Voltage Dimmers

DIMDIM

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DIMDIM

Dimming Driver

• Transform Voltage

• Convert AC To DC

• Vary Current To LEDs

• Smooth Output

• Compensate For Power Fluctuations

• Don’t Misbehave

• 0-10v, DALI, DMX, 3-Wire Line Voltage

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Light Output vs Power

• Depends on LED and its cooling

• Heat affects efficacy

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Dimming Performance

• Range Of Dimming ?

• Turn On Behavior ?

• Dimming Curve ?

• Flicker ?

• Eye Response: Perceived Light = Square Root of Measured Light

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Light Output vs Time & Temp• See DOE Caliper

Testing Reports

• Heat Degrades

• L90, L70

• Cooler LEDs shift less

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Dimming White LEDs

• Blue + Phosphor

• Lighting Research Center Study: Chromaticity Shifts Due To Different Dimming Methods

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Dimming White LEDs

• Lighting Research Center Study: Chromaticity Shifts Due To Different Dimming Methods

• CCR Chromaticity shift yellow

• PWM Chromaticity shift blue

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Color vs Time

• What The …

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OLED - Organic LED• Organic Semiconductors

• Thin

• Flexible

• Lifespan

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Natalia Lupacheva - ETC

• Dimmer - Driver - LED interactions• Phase Control dimming - forward and reverse• AC + Control Signal dimming - 0-10v, DALI, DMX• Dimming techniques - Pulse Width Modulation, Constant Current Reduction

• Flicker issues• Turn-On behaviors• Dimmer load restrictions • NEMA SSL-7A Standard

Natalia Lupacheva

ETC

1. Coincident AC power and control signal

• Phase-cut dimming

- forward phase

- reverse phase

2. Separate AC power and control signal

• Fluorescent 3-Wire• 0-10V• DALI• DMX512

Dimmers reduce the RMS voltage delivered to the lamp by removing a portion of the AC waveform from forward or reverse phase.

• Dimmers reduce the RMS voltage delivered to the lamp by removing a portion of the AC waveform from the forward phase, or leading edge.

• Designed for resistive (incandescent, halogen) or magnetic low-voltage (MLV) loads. cuts off the front side of the

wave

• Dimmers remove a portion of the AC waveform from the reverse phase, or trailing edge.

• Originally designed to improve the performance of low-voltage halogen lamps operating on electronic transformers. cuts off the back end of the

wave

• Separate AC power and control signal (phase-cut hot control signal)

• Smooth dimming• Stable over long wire runs • Allows for maximum circuit loading

• Impossible to assign individual control to one or many light fixtures without rewiring

• Fairly smooth dimming of LED fixtures

• Control zones can be run separate from power zones (requires two extra low voltage wire runs)

• Long wire runs can affect performance (e.g. dimming range, accuracy)• Two 0-10V standards exist. Use of components complying with different

“standards” results in interoperability problems.• Impossible to assign individual control to one or many light fixtures without

rewiring

0-10V using ANSI E1.3

• Control sources the current• Load sinks the current• 10V = 100% light• 0V is off

0-10V using IEC 60929

• Load sources the current• Control sinks the current• 10V or above = 100% light• 1V or below= minimum light

• Two-way communication • Easy to assign individual control to one or many light fixtures without rewiring

• Simple interface BMS.• Easy modifications

•Many manufacturers have “proprietary” extensions•Requires two low-voltage differential wires •Requires extra commissioning and installation time

• Two-way communication system that brings digital technology to lighting

• DALI defines the commands that ballasts need to recognize in order to be considered DALI ballasts

• Allows for a maximum of 64 fittings on a single network

• DMX512 is a serial protocol used to control lighting equipment like dimmers, stage lighting and theatrical effects (ex: moving lights, color changing lights, fog machines, etc.)

• Controls, luminaires, and wiring have to comply with the standard

• Available in wireless implementations as well (WDMX)

• Two way communication between controller and DMX device (with RDM)

• Requires two low-voltage wires for control

• Addressing of up to 512 channels per data link or “universe”

• Easy to assign individual control to one or many light fixtures (devices) without rewiring

Whether separate or integral, the driver electronics determine the dimming performance of an LED source

Two common methods of dimming LEDs: •Pulse Width Modulation (PWM) •Constant Current Reduction (CCR)

LED sources require a “driver””

A PWM based LED dimming driver pulses the LEDs on and off at a rate of about 240 pulses per second.

• Cameras pick up the pulses - looks like strobing.

• Potentially undesirable flicker• Power supplies are more complex and

expensive to manufacture.• PWM drivers may experience

performance issues if mounted remotely from the light source

• Provide very precise output level – good for color mixing

LED dimmed to approximately 25% using PWM

• No noise generation• Does not create flicker• Longer wire runs between the driver and

the light engines.• Color shift below 40%

CCR (analog) driver sends a varying amount of current to the LED

LED that is reduced to approximately 25% using CCR

• Flickering (hovering)• Flashing/strobing• Pop-on • Drop-out• Dimming smoothness• Popcorn• Audible noise• Dimming range• Dimmer loading

• Premature failure of dimmer

and/or LED load

• Ghosting

100 lamps on a circuit at control level 75%.

• Flashing from dimmed level to Full

• Flashing from dimmed level to Off

• Hovering (flickering, fluttering..)• Acting like non-dim (On or Off)• Full to Off or Off to Full

Problem:

Flashing from dimmed level to Full

Reason:

The load is too capacitive for the FPC (Forward Phase Control) dimmer

Problem:

Flashing from dimmed level to Off

Reason:

Load is not big enough (resistive) for FPC (Forward Phase Control) dimmer.

Problem:

Acting like non-dim (on or Off)

Reason:

1. LED lamp is not designed to dim

2. Not enough load on a circuit

Problem:

Full to Off or Off to Full

Reason:

Not enough load on a circuit

When Voltage amplitude changes dimmer tries to compensate by regulating the turn on time to keep the same RMS voltage.

Problem:

Hovering (flickering, fluttering..)

Reason:

1. Change in Line voltage

2. LED lamp is not designed to dim (or dim well)

Reason: lamps aren’t made the same

• Created by connection to power, occurs once per power-up

• Can be 100’s x Irms

Inrush is 65 times higher than rated RMS current.

• Excessive wear on switch or relay contacts

• Chokes can help to minimize inrush to dimmer

• Created by forward phase-cut, occurs every half-cycle

• Commonly 5-10x Irms; can be much higher

• Major factor determining maximum dimmer loading

• Major contributor to audible noise in light sources and controls

• A very brief spike in voltage (above the instantaneous line voltage) caused by the discharge of energy-storage elements

• Can cause long-term damage to voltage-sensitive components in the dimmer or lamp

• Caused by interaction between dimmer and lamp

• Noise can come from the dimmer itself (If the existing dimmer cost less than $20, try a dimmer that uses a toroidal filter or a densely wound bar choke)

• Noise can come from the lamp (caused by interaction between dimmer and lamp)

• Issue with MR16 lamps retrofits • Two compatibility requirements

• Loading requirements

• Transformers designed for resistive loads

• Interaction between dimmers and LED light engines

• It is not intended to be used to determine compatibility with existing (non-compliant) products

Marking requirementsDimmer•Maximum rated wattage•Minimum load•Type 1/Type 2 compliance•How to set SSL-7A load type•LLE•Minimum light output•Type 1/Type 2 compliance

• LED product evolution is rapid and product generation life is short

• The LED driver determines dimming performance

• Compatibility must be determined BEFORE products are ordered and installed

• Questions to ask: - Is the LED product a lamp or luminaire? - Designed (claimed) dimming performance of the LED? - What type of control signal is LED designed for? - Does LED product have a recommended dimmer list,

control type, dimmer loading requirements, etc…

• Perform Mockups

Dimming quality characteristics such as lack of flicker, smoothness, or a specific minimum dimmed level are best evaluated by observation, which is why mockups are so strongly recommended. If a mockup is not possible, use a proven combination of LED sources and dimmer.

Presented by:Greg SmithTivoli, LLC

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Greg Smith - Tivoli

• Visual effects:• Range of control, minimum output• What happens to color when you dim LEDs• Advantages when using LEDs vs other sources• Range of LED whites and colors• Variable / Dynamic white color control• Warm shifting• Color tuning• Lumens vs color• Automated controls

• Maximum Lumens are dictated by circuit design and operating current

At 350m A – Decisions need to be made…

Higher Lumens by Driving current HigherHigher Lumens by Driving current Higher

Trade Off:•Heat Output•Life and more

Trade Off:•Heat Output•Life and more

• Minimum Output is based on visual illumination point

• Dimmer setting value vs. illumination value percentage

• Low end of output cuts off at 10% to 20%.

• Based on Dimmer setting Value vs. illumination percentage value

Minimum OutputMinimum Output

• Dimming via PWM:

• Maintain color but have an underlying “flicker” or “shimmer” while CCR dimmed LEDs can show a shift in color but remain smooth.

• What applications makes sense for each type of dimming?

• LEDs add a new feature to dimming with adjustable intensity with controlled color

Source: Electrical Contractor

• Incandescent / Halogen• Fluorescent• LED Warm Whites• LED Colors

Sources warm along the Black Body Line as the intensity of the light is reduced.

This has become the model for residential and entertainment lighting that LED technology has been moving towards.

• Have the same adjustable intensity without the color shifting qualities of Incandescent

• Ideal for signage, decorative and constant illumination space applications that LEDs have been able to move into very well.

LED White colors feature•Beautiful High CRI•Tight binning•Even warm 2200ºK color

Same dimming characteristics as White LEDs

Photo Credit: LED Inside

Can we do this with whites?

Defined as illumination that mimic the dimming curve of incandescent light sources.

• Single circuit

• Mimics incandescent sources, warming color shift as light intensity decreases

• There are limitations of this simple set up and the affects on Lumens and Color range

• Set up using 2 colors of LED in the same fixture space

• Dimming is controlled with the Warmer color at 100% illumination at all times

• Dimming control is connected to the Brighter LED circuit

• Work with programmed controllers or IC chips to adjust both colors in a way that mimics the Black Body curve without the color Lumens limitations of the simple Dim to Warm.

Variable White is similar to our simple Dim to Warm set up except that both LED colors are connected to controllable dimming circuits. This can be done in both simple and smart controlled methods.

• Based on 2 color LED mix.

• Low end warm white

• High end cooler white

• Connecting to the 2 LED colors as separate dimming control circuits allows the user to dial in a color based on intensity levels of each circuit.

• Control allows preprogrammed settings that dial in both the color mix and lumens desired for the lighting with a single interface

• 4-circuit control• Offers wider range of color mixing with

variable lumen output and color temperature

• Dynamic whites are based on the use of White, Red, Warm White and Yellow LEDs.

• There can be variances from different manufacturers of what CCT is used for the White and Warm White and even the wavelengths of the Red and Amber LEDs.

• Already available in some down light fixtures

• Includes all of these LED colors and intelligent internal control

• Creates an illumination that directly follows the Black Body line curve

• All Inclusive• Controllable White

Source: CREE – preset Sunset Dimming

• DMX controls creates color contrasts and uniformity between different fixtures within the same space almost regardless of manufacturer and ambient color reflections.

• Knowing the ingredient colors of the Dynamic LED sources and checking that they match between fixtures will help to ensure that uniformity can be achieved.

What is more important?

• Can other control applications like external triggers be the vehicle for changing the color?

• Change in Intensity

• What about Color?

Motion sensors

Photo Cells

Timers

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• How LEDs work - understanding the basics

• How LEDs dim - different approaches

• What happens when LEDs dim - color, life, efficiency, flicker, noise

• Matchmaking - how to get LEDs, drivers and controls to work together

• Application do’s and don’ts

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Panel: Do’s and Dont’s,Questions and Answers

Gary DulanskiThe Dulanski Group

Natalia LupachevaETC

Greg SmithTivoli

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Gary DulanskiThe Dulanski Group

Natalia LupachevaETC

Greg SmithTivoli

Thank You!

Please Fill in Evaluations!

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Flicker, Buzz and Color Change

The Crazy World of of LED Dimming and Control

March 19, 2014