Anthony Catalano - EEWeb

EEWeb 

PULSE 

EEWeb.com 

Issue 45 

May 8, 2012 

Anthony 

Catalano 

TerraLUX Inc. 

Electrical Engineering Community


Electrical Engineering Community 

Contact Us For Advertising Opportunities 

1.800.574.2791 

advertising@eeweb.com 

www.eeweb.com/advertising

TABLE OF CONTENTS 

Anthony Catalano 4 

TERRALUX INC. 

Interview with Anthony Catalano - Founder and CTO 

Advanced Thermal Control for 10 

Ensuring LED Lifetime 

BY ANTHONY CATALANO 

Learn the root causes of LED light degradation and what factors assure maximum LED 

lifetime. 

Featured Products 15 

Illogical Logic - Part 1: Boolean Algebra 

BY PAUL CLARKE WITH EBM-PAPST 

See how Boolean Algebra allows you to break complex logic to simply the elements that matter. 

A System Perspective on Specifying 21 

Electronic Power Supplies: Efficiency 

BY BOB STOWE WITH TRUE POWER RESEARCH 

How energy conservation, package size and rise in temperature attribute to optimal power 

supply efficiency. 

17 

RTZ - Return to Zero Comic 24 

EEWeb | Electrical Engineering Community Visit www.eeweb.com 3 

TABLE OF CONTENTS

INTERVIEW 

Anthony 

Catalano 

TerraLUX, 

Inc. 

Anthony Catalano - Founder and CTO 

How did you get into electrical 

engineering and when did 

you start? 

I decided I wanted to be a chemist 

in the 6th grade, but got involved 

in electronics in high school by 

building a mass spectrometer 

and other electronic gadgets. I’ve 

always had one foot in electronics 

and another in chemistry. I got my 

undergraduate degree in chemistry 

from Rensselaer Polytechnic 

Institute and went on to receive 

my Ph.D. from Brown University, 

and did a post-doctorate in solidstate 

chemistry. While I was at 

Brown, I made my first LED, which 

really jumpstarted my career in 

electronics. Until then most of my 

solid state work had been done 

on passive materials and here 

was something that generated 

light! However, my career was 

quite separate from LEDs initially 

in that it dealt mostly with solar 

cells. I was on the staff at the 

University of Delaware’s Institute 

of Energy Conversion for several 

years working on Thin Film Solar 

Cells. I went from there to RCA 

Laboratories in Princeton and 

worked with Dave Carlson, the 

inventor of the amorphous silicon 

solar cell. While there, I developed 

the world’s first 10% conversion 

efficiency amorphous silicon solar 

cell, for which I received an award 

and a bunch of job offers in Japan. 

RCA decided it really wasn’t too 

interested in solar cells, and got 

out of the business. A group of 

us—including Dave Carlson—left 

and started a division of Solarex, 

Inc., which was already making 

crystalline silicon solar cells. We 

started the business with a filing 

cabinet a telephone and 30,000 

square feet of warehouse space, 


FEATURED INTERVIEW

INTERVIEW 

and that was the beginning of my 

entrepreneurial experience. I ended 

up turning it into manufacturing 

and R&D space, and the business 

began to grow. 

Solarex was later acquired by 

Amoco, which of course—long after 

I left—was purchased by British 

Petroleum (BP), which now has 

gone full circle and is divesting 

itself and closing down because of 

all of the worldwide competition in 

Photovoltaics. 

After leaving what was then 

Amoco, I came out to Colorado 

to be the Director of the National 

Renewable Energy Laboratory’s 

(NREL) photovoltaic division. We 

were working for The DOE (U.S. 

Department of Energy) to reduce 

the cost of solar energy to allow 

it to compete with other forms of 

electrical generation. 

In 2003 I realized that the white LED 

is really a game-changer. It was 

Craig Christensen from Harvard 

who coined the term “disruptive 

technology,” and if LEDs aren’t 

a disruptive technology, I don’t 

know what is. So I thought about 

exploring this technology, and 

said to myself, “You can stand on 

the sidelines or you can get wet.” 

And I decided to get wet and start 

TerraLUX to commercialize LED 

lighting technology. I really feel that 

LEDs will completely transform 

how lighting is produced during the 

21st Century. Hence our company 

tagline: “Intelligent Lighting for the 

21st Century.” 

I started the jump into LED lighting 

as both an inventor and angel 

investor in TerraLUX—spending 

my own money to get the company 

started—I really wanted (and 

needed!) to have products that I 

could design and sell in fairly short 

order. 

The Company’s first entries into the 

LED lighting market were intended 

to generate revenue quickly. So 

we decided to build retrofits for 

flashlights that were then using 

incandescent bulbs. There were 

very few LED flashlights on the 

Our general 

illumination products 

are little bit less than 

50 percent, but it’s 

rapidly catching up. 

We expect it surpass 

the flashlight & 

upgrade business 

pretty quickly. 

market, and that’s how we got 

started. This all started in my 

garage in 2003. After it took over 

the kitchen, laundry room, garage 

and one of my daughter’s rooms we 

were asked to leave. 

Our flashlight upgrades were a 

considerable improvement to 

incandescent bulbs, and although 

they were expensive, there was a 

rather large market for them. The 

business ended up taking off, and 

really provided the revenue to do 

things like file patents and hire 

people to help us grow. 

The business was going well, but 

my eye has always been on general 

illumination. When I started the 

business, my vision—if I can justify 

that term—was for LED lighting 

to displace all of the then-current 

forms of lighting. It was efficient, 

potentially immortal in terms of 

its longevity, and it had so many 

features that were going to make it 

difficult for anything to stand it its 

way. I still feel that way. 

What are some technical 

challenges for LED lighting to 

be more universally adopted? 

Part of it is of course the present 

state of the economy. There isn’t a 

lot of new construction going on, so 

one of the technical challenges that 

we face regularly is compatibility 

with the existing infrastructure. 

The existing infrastructure in 

buildings—whether residential 

or commercial—involves legacy 

power supplies and legacy 

dimmers. One of the big challenges 

associated with that is making LED 

lighting work to the same level of 

performance that customers are 

used to. Flicker-free performance 

and dimming is an area where we 

have put a very large effort. 

Of course we have an eye to 

the future and want to be at the 

forefront of the technology. While 

the emphasis now is on energy 

efficiency, we are looking forward 

to how we’re going to deal with 

building information systems and 

things like that. We’re trying to see 

the whole universe of possibilities 

for LED lighting backward (in 

terms of compatibility) and forward 

(as regards building information 


FEATURED INTERVIEW

INTERVIEW 

systems). Our customers are not 

the people who are typically buying 

LED light bulbs; we’re selling to the 

original equipment manufacturers 

(OEMs) and some of the major 

lighting fixture manufacturers. 

We’re trying to build features into our 

products—our LED light engines— 

features that will give our customers 

assurance that the products will 

fulfill the lifetime and energy that 

people expect of LEDs . One of the 

signature features of nearly all our 

products is thermal fold back, or 

LEDSense®. As the temperature of 

the LED gets higher, the allowable 

current is lower, so we adjust the 

current through the LED based on 

temperature measurements within 

the drive electronics. We use the 

LED Manufacturer’s LM-80 test data 

to do this. It’s all microprocessor 

based. 

What were some of the 

initial products TerraLUX was 

providing/selling? 

White LED technology in 2003 did 

not quite meet the needs of many 

illumination applications from a light 

output and light quality standpoint, 

so our very first products were in the 

portable space in the form of LED 

upgrade modules for flashlights. 

There are literally many millions 

of quality flashlights sitting around 

in toolboxes and kitchen drawers 

that quickly become obsolete from 

a performance stand-point with the 

introduction of LED technology. By 

offering LED upgrades for many 

popular flashlight models such as 

MAGlite ® and Streamlight ® , we 

gave technicians, mechanics, police 

officers, campers, and consumers 

the ability to “upgrade” their 

flashlight to LED performance for a 

fraction of the cost of buying a new 

LED flashlight. The improvement 

in both light output and run-time is 

significant. The concept quickly 

caught-on, and 

The technology we 

are developing is 

addressing the sector 

of the lighting market 

characterized by 

small form factor, 

high brightness and 

thermally challenging. 

A key element is 

various methods of 

providing protection 

to the LED and circuit 

components that 

ensures a long life. 

we now make upgrades for a wide 

range of flashlights. Eventually, 

we started designing and selling 

our own flashlights, and continue 

to expand our line with unique 

features such as penlights with high 

Color Rendering Index (CRI) LEDs 

for technicians to more clearly 

differentiate wire colors, and even 

flashlights that have been designed 

to accept an upgraded LED 

module in the future—because 

we will continue to see significant 

improvement in LED technology 

and performance for years to come. 

How much of your business 

focuses on flashlights versus 

the other lighting areas you’ve 

mentioned? 

Our general illumination products 

are slightly less than 50 percent, but 

are rapidly catching up. We expect 

it surpass the flashlight & upgrade 

business pretty quickly. 

Exactly what products do you 

sell to the OEMs? 

We have both line voltage and low 

voltage products. The low voltage 

products are MR16 halogen bulb 

replacements. We aren’t actually 

selling LED light bulbs though; what 

we’re selling is what we refer to as 

a light engine. They are form factor 

compliant, which means a little bit 

less than two inches in diameter so 

they can fit into customers’ fixtures 

that have been sized for an MR16. 

While they won’t fit into every fixture 

as is, it’s very easy for our OEM 

customers to adapt their products, 

and we help them do that. 

Most often this means little more 

than designing a small adapter that 

basically forms a thermal bridge 

between our light engine and the 

manufacturer’s fixture. Also, most 

of the lighting manufacturers are 

very skilled metal workers, and it’s 

usually easier for them to make 

it than it is for us. We actually use 

the fixture as a heat sink, which 

is essentially impossible for an 

ordinary LED light bulb because a 

bulb does not integrate mechanically 

and thermally with the fixtures. In 

many cases, that means that an 

ordinary LED bulb in a fixture will 


FEATURED INTERVIEW

INTERVIEW 

reach a destructive temperature. 

At any given time, LEDs must be 

maintained within a safe operating 

temperature range. This is nearly 

impossible for a sealed fixture 

with a LED replacement bulb, but 

fairly straight-forward using one 

of our modular light engines. One 

area where we’ve become pretty 

successful, is landscape lighting. 

Landscape lighting fixtures are 

sealed, and can pretty easily 

accommodate our product. 

We have also developed a more 

versatile spotlight engine for 

applications like track lighting— 

one that can provide light output 

equivalent to a 50 watt halogen as 

well as several output levels below 

that. It also has features to alter the 

beam angle. So now customers 

only have to stock one product and 

change the output based on the 

specifications of the fixture or the 

lighting designer’s requirements. 

This product benefits everyone 

involved. It makes things easier for 

the fixture manufacturer, the lighting 

designer and the end user. 

This month we also started 

shipping our compact 120V linear 

engines as well. These work with 

current dimmers and infrastructure 

and are aimed at 120 to 180 degree 

output applications such as wall 

sconces, ceiling-mounted fixtures, 

and recessed step-lights like 

those found in theatres or outdoor 

landscape environments. Within 

a few months we will also offer a 

flexible voltage version of these 4 to 

8-inch long modules, which can be 

powered with 100-277 Volts AC. 

Do you develop custom 

lighting products for other 

companies if they request it? 

Yes, we’ve actually done that 

for many years. For example, a 

well-known healthcare company 

approached us in 2005—I guess 

because some of the engineers 

there bought our flashlight 

products—and asked us to design 

a product for them that eventually 

found its way into one of the world’s 

first LED medical scopes of its 

kind. That was an OEM product; 

it was proprietary to them and we 

continue to manufacture it for them 

to this day. 

Can you tell us more 

about TerraLUX, Inc. and 

the technology they are 

developing? 

The technology we are developing 

is addressing the sector of the 

lighting market characterized by 

small form factor, high brightness 

and is thermally challenging. A 

key element of our technology are 

the various methods of providing 

protection to the LED and circuit 

components that ensures a long 

life. Our goal is to provide a 

“Plug & Play” solution for both 

the OEM manufacturer and 

retrofit opportunities. Providing a 

completely engineered solution is 

our goal. Many of the OEMs are 

focusing on design and appearance 

and have few resources to devote to 

a product that requires expertise in 

electrical, optical, mechanical and 

thermal engineering. We do that so 

they don’t have to. 

We are now introducing a line 

voltage (100-277VAC) dimmable 

series of linear light engines that 

are completely integrated and have 

the necessary UL, FCC and other 

approvals. Although the product is 

effectively a luminaire by itself, it’s 

intended for OEMs to include in 

sconces, ceiling lights and other 

fixtures they manufacture. It can 

also be used in retrofits of existing 

luminaires in the field. Because it is 

truly Plug & Play, it only requires 3 

wire nuts and a screwdriver to install. 

I say this from personal experience; 

I’ve installed them in outdoor 

sconces at home. It’s almost a DIY 

product. We have a low voltage 

(12 VAC) product coming onto 

the market that produces the light 

output equivalent of a 50 W halogen. 

This product has variable beam 

angle and adjustable brightness 

levels that can be set. In essence, a 

lighting manufacturer can stock one 

SKU and with little effort either the 

lighting designer or manufacturer 

can change beam angle and light 

output either on the factory floor 

or in the field. It’s also dimmable 

using our microprocessor-based 

Dynamic Transformer recognition 

(DTR) and contains a high level 

thermal fold-back feature that is tied 

to the LED’s LM-80 data. It’s a pretty 

sophisticated product. 

What direction do you see 

your business heading in the 

next few years? 

Lighting is, from a small company 

perspective, a semi-infinite market. 

Maintaining focus during a period of 

extraordinary growth is the greatest 

challenge. That said, we have very 

ambitious goals and expectations of 

continuing to expand our portable 

product (flashlight) business while 

also realizing explosive growth with 

our LED engines for the general 

illumination market. Interestingly 


FEATURED INTERVIEW

INTERVIEW 

enough, we’ve found the 

technology development for these 

two different markets to be very 

complimentary. For example, we 

initially developed our LEDSense® 

Thermal Management technology 

for flashlights, which allowed us to 

realize significant light output from a 

flashlight with minimal heat-sinking 

during the typically short “ontime” 

that a flashlight experiences, 

while also ensuring that the system 

does not overheat or degrade the 

LEDs if left on for a longer period 

of time—either purposely or by 

accident. Now we use LEDSense® 

technology in our illumination 

engines to assure long-term lumen 

maintenance in potentially adverse 

conditions such as a landscape 

lighting fixture being accidentally 

covered in dirt and not able to 

dissipate heat. With LEDSense®, 

the system will simply pull back on 

power until the fixture us uncovered. 

We expect to continue to leverage 

core technology like this in more 

and more lighting applications, 

leading to significant growth for 

many years to come. 

What challenges do you 

foresee in our industry? 

The legacy infrastructure for 

lighting is quite diverse and 

complex. The various dimming 

schemes and power sources (both 

line and low voltage) represent a 

huge challenge. LEDs react nearly 

instantaneously, which is often a 

curse. The slow response time of 

incandescent sources prevents 

many problems from becoming 

apparent. When LEDs are used the 

often messy state of the electrical 

infrastructure becomes evident. The 

LED light source is usually faulted. 

We as an industry must figure out 

how to ensure an experience which 

is cost-effective and satisfying. 

Do you have any tricks up 

your sleeve? 

We have a lot of technology we have 

not deployed in products. There 

are methods of LED control that get 

to the basic physics of how LEDs 

operate that would be exciting 

to implement, but it’s probably 

too soon. Other features such as 

making the light source part of 

the information superhighway are 

exciting. Since LEDs are very 

controllable, and require drive 

electronics anyway, taking the next 

step of integrating lighting into a 

building information system is not 

a significant stretch. This can offer 

significant new features from tuning 

light to meet the demands of the 

users to a higher level of control for 

the purpose of conserving energy. 

By integrating technology such 

as wireless control into our LED 

engines and modules, we can even 

bring these new features to older 

buildings. 

Is there anything that you 

have not accomplished yet, 

that you have your sights on 

accomplishing in the near 

future? 

I think we as a team want to see 

TerraLUX recognized as a leader 

in LED lighting. As my high school 

physics teacher implied, we need 

to turn our “potential” into “kinetic.” 

Personally, having started the 

Company back in 2003 it has been 

very satisfying to see the original 

vision turned into products, patents 

and perhaps most importantly-jobs. 

■ 


FEATURED INTERVIEW

Avago Technologies 

Tri-color High Brightness 

PLCC6 SMT LEDs 

gives you a reliable, 

long life product for 

ease of design in full 

color interior and 

exterior signs 

Tri-color High Brightness SMT LEDs 

from Avago Technologies 

Avago’s PLCC-6 SMT LEDs are high 

brightness, high reliability, high 

performance, IPX6 compliant and 

are water and dust proof. They are 

designed with a separate heat path for 

each LED die, enabling it to be driven at 

higher current. They deliver super wide 

viewing angle at 120° together with 

the built in reflector pushing up the 

intensity of the light output. 

Applications 

• Indoor and outdoor full color display 

• LED advertisement panels 

• Decorative lighting 

AvagoTechnologies LED Lighting Solutions 

One LED. Infinite colors. 

World’s first waterproof package. 

Features 

• Water-resistance (IPX6*) per IEC 60529:2001 

• Very small PLCC6 package dimensions – 

3.4 x 2.8 x 1.8mm 

• In-line RGB dies configuration 

• Available inWhite Surface, Black-Surface 

and Full Black-Body 

• Wide operating temperature range: 

-40° to +110° 

For more information or to 

request a sample please go to: 

www.avagoresponsecenter.com/led

Background 

Advanced 

Thermal Control 

for Ensuring LED Lifetime 

White light emitting LEDs have proven to be a disruptive 

technology challenging all older forms of light generation. 

The potential for: 1) very long life (>35,000 hrs), 2) 

extremely high efficacy (theoretically ~250 Lumens/ 

Watt) and 3) low temperature operation has taken the 

lighting market by storm. These great expectations of 

the technology have lead LED manufacturers and the 

industry as a whole to devise testing standards to ensure 

lighting products embody the performance that is 

expected by consumers, whether they be the end user or 

the OEM manufacturer. Unlike ordinary filament-based 

incandescent lamps, LEDs do not “burn out” but instead 

may gradually experience a decrease in light output 

depending on operating conditions. 

Why Do LEDs Degrade? 

LEDs are complex solid state devices. Figure 1, 

illustrates a cross-section of a typical device, showing 

the various structures that comprise a packaged LED. 

Anthony Catalano 

Founder and CTO TerraLUX Inc. 

For simplicity we will categorize the components into 

3 areas. First, a semiconductor device containing a 

p/n junction that, in the case of conventional white 

LEDs, actually generates blue light at a wavelength of 

approximately 450 nm. Second is a phosphor layer that 

absorbs the blue light and coverts it to a broad band of 

colors that the eye perceives as white in much the same 

manner as a fluorescent tube. Lastly, there are a series 

of clear layers that encapsulate the semiconductor and a 

lens that collimates the exiting light. Each of these three 

regions may participate in the degradation of the device, 

albeit through different mechanisms. 

The Semiconductor Junction. LED manufacturers hold 

dear their process and composition of the semiconductors 

that comprise the diode’s p/n junction. However, at 

present, all devices are comprised of materials classified 

as III-V materials: Ga, In, or Al combined with N, P, As from 

the respective columns 3 and 5 of the Periodic Chart. 

Virtually all commercial devices are heterojunctions, 

meaning they are combinations of dissimilar chemical 

EEWeb | Electrical Engineering Community Visit www.eeweb.com 10

PROJECT 

Figure 1: Simplified Cross-section of an LED illustrating the 

important components associated with degradation. 

E N 

E C 

E V 

Photon 

Defect 

Lens 

Encapsulant 

Phosphor 

Semiconductor Die 

Conduction 

Band 

Valence 

Band 

- electron 

- hole 

Figure 2: Band Diagram Illustrating radiative emission and nonradiative 

recombination via defects. 

compounds. Moreover, they are single crystal structures 

relying on epitaxial growth via chemical vapor 

deposition for their formation. These layers are grown 

on substrates such as sapphire or silicon carbide. Often 

they are complex layered structures,-so called “quantum 

wells” that carefully manipulate electronic processes to 

maximize the conversion of electrical charges into light. 

One consequence of these combinations of dissimilar 

materials are defects that arise due to mismatches in 

the atomic lattice dimensions and thermal expansion 

coefficients among the layers. The consequence of 

these imperfections are atomic defects in the lattice 

structure, both in the bulk of the material as well as at the 

interfaces between the different materials. To create light 

electrons injected from the majority carrier, n-type doped 

layer recombine with holes injected from the p-type 

contact within the junction to form blue light. However, 

not all electrons and holes recombine to generate light, 

otherwise we would have vastly higher performance! 

Non-radiative recombination of carriers may happen via 

several mechanisms, but the most important from the 

standpoint of reliability occurs at these defects within 

the semiconductor. Because these defects lie at a lower 

energy level than the conduction and valence band of the 

semiconductor, they act as a means by which electrons 

and holes recombine non-radiatively, giving off heat 

instead of light. This energy can be quite large, on the 

order of the energy of the chemical bonds and thereby 

creates more defects through the displacement or 

rupture of chemical bonds. This initiates a “snowballing 

effect” that accelerates with time. Figure 2 illustrates a 

simplified band diagram of the semiconductor showing 

the various recombination processes. 

Phosphors. Phosphors convert the 450 nm blue light from 

the LED to the various colors of the visible spectrum to 

create white light. They do so by absorbing the blue light 

and losing a portion of the photon’s energy in a controlled 

fashion, down-converting the blue to red, green and blue 

over a broad band of wavelengths. These phosphors are 

often complex rare-earth silicates or oxides, and may 

be doped to ensure specific wavelengths of emission. 

While these materials are polycrystalline and already 

contain numerous atomic defects, recombination as 

described in the previous section is active here too. 

In addition chemical processes such as reaction with 

water vapor or other chemical compounds can lead to 

degradation. Because these effects are highly dependent 

on the chemical composition of the phosphors, and the 

phosphors used are part of proprietary designs, there 

may be considerable variation among LEDs. Often even 

within a manufacturer’s product line different phosphors 

are used, or they are applied in a different fashion that 

results in a particular behavior. 

Lens & Encapsulant. The clear lens that acts to collimate 

light emanated from the semiconductor die-phosphor 

structure and the protective encapsulant material must 

remain highly transmitting throughout the life of the 

LED. Because LEDs operate at elevated temperature 

and humidity, degradation may occur here as well. In 

addition, the blue light exiting the LED phosphor also 

may play a role in the darkening process. Once more, the 

specific chemical composition and structure of the lens 

will determine its behavior under normal and adverse 

circumstances and is highly process and composition 

dependent. 

Conclusion. The complex electrical and chemical 

processes that occur during the operation of an LED 

and give rise to decrease in light output are difficult 

to quantify via a simple analytical expression. While a 


FEATURED PROJECT

PROJECT 

mathematical description might be possible for one or 

two of these processes, the complex overlapping and 

interdependence of the processes makes it impossible 

at this time. 

Standards: LM-80 and TM-21 

The Illumination Engineering Society (IES) has 

developed standards for testing LEDs so performance 

and reliability can be characterized in a consistent 

fashion to assess their practical life. One standard, 

LM-80, provides a description of the method to be used 

in determining the “Lumen Maintenance” of LEDs, that 

is the light output as a function of time. The essential 

features specified by the testing protocol are: 

• Ambient and LED Case Temperature and Orientation 

• Drive Voltage, Current and Waveform 

• Instrumentation 

The standard calls for measurement of light output 

at an ambient air temperature of 25 o C, but LED case 

temperatures of 55 o C, 85 o C and another temperature 

selected by the manufacturer. The drive current is 

specified by the manufacturer as this varies with the 

die area of the LED. Measurements take place over a 

minimum of 6000 hrs of operation (10,000 hrs is preferred) 

and at intervals of at most 1000 hrs. It is common practice 

among first-tier manufacturers to employ several different 

drive currents. As we shall see later this is very important 

to our method of ensuring LED lifetime. 

Although LM-80 provides a uniform method for measuring 

light output over time under standardized conditions, in 

practice LEDs may be used at temperatures that differ 

substantially from the LM-80 values. Moreover, because 

this is not an accelerated testing method, very long times 

are needed to reach a conclusion on reliability. Another 

more recent IES Standard, TM-21 helps solve this 

dilemma. The standard is effectively an “ad hoc” model 

of LED degradation that allows the interpolation of timetemperature 

data between temperatures and formalizes 

the extrapolation of data into the future to predict output 

over extended times. The major points of the standard 

are: 

• Exponential Decrease in Light Output (LOP) is 

assumed 

• LOP May be Extrapolated Maximum of 6x in Time 

• Interpolation Between Temperatures Are Based on 

“Activation Energy” 

In mathematical terms the decrease in light output can 

be stated as, 

L(t) B[e ] 

t -a 

= 

where L(t) is the Lumen output at time t, B is the 

normalized light output at 0 or 1 hours, and α is the 

decay rate, which is a function of temperature. The value 

of α varies with temperature according to the Arrehenius 

expression, 

a(T) 

= Ce 


E /kT a - 

where Ea is the activation energy, k is Boltzmann’s 

constant and T is the temperature in degrees Kelvin, and 

C is a constant. The TM-21 standard only allows for the 

interpolation of temperature data, so for two temperatures 

T 1 and T 2 we can calculate the activation factor, E a /k as, 

a1 

ln[ a2 

] Ea 

= ( ) 

1 1 k 

[ - ] 

T2 

T1 

Once the activation factor is known then it is 

straightforward to calculate the decay rate from the 

Arrehenius expression for the intermediate temperature 

and the resulting time dependence. Figure 3 shows 

a graph of both real LOP data and the extrapolated 

and interpolated values based on these calculations 

(reference: Mark Richman LEDs Magazine). 

Normalised Light Output 

1.1 

1 

0.9 

0.8 

0.7 

0.6 

105C1 Amp Data 

TM-211 Amp 105C 

85C1 Amp Data 

TM-211 Amp 85C 

0.5 

0 5000 10000 15000 20000 25000 

Hours 

Figure 3: LED degradation data (triangles and diamonds) used to 

extrapolate and interpolate temperature vs time Lumen maintenance 

information. 

FEATURED PROJECT

PROJECT 

The Important Role of Drive Current on 

Lumen Maintenance 

The drive current of the LED plays an important role in 

determining Lumen maintenance. As discussed at the 

outset of this article, recombination in the semiconductor 

leads to the multiplication of defects and a reduction 

of the radiative efficiency. So it stands to reason that 

drive current must play an important role in Lumen 

depreciation. Unfortunately, no current standards 

recommend testing in this regime, and it is left to the 

LED manufacturer to choose the values of current used 

in testing. Fortunately, the top-tier manufacturers have 

chosen wisely and substantial data is available. 

Figure 4 provides a dramatic illustration of the importance 

of drive current, particularly at elevated temperatures. 

In this chart TM-21 has been used to extrapolate the 

Lumen maintenance data for an LED at a semiconductor 

junction temperature of approximately 127 o C. It can 

clearly be seen that there is a very large increase in the 

rate of degradation as the current rises from 0.35 A to 

1 Amp. It can also be seen from this chart that the L70 

value (where light output decreases to 70% of its initial 

value) decreases from over 91,000 hours at 0.35 Amp 

to 22,900 hrs at 1 Amp, a huge reduction in effective 

useable life. (Strictly speaking TM-21 only permits a 

6-fold extrapolation beyond the time-dependent data; I 

have clearly gone beyond this to make a point) 

Normalised Light Output 

1 

0.9 

0.8 

0.7 

0.6 

T j ≈127ºC 

1 Amp Data 

0.7 Amp Data 

0.35 Amp Data 

1 Amp Calc 

0.7 Amp Calc 

0.35 Amp Calc 

0.5 

1000 10000 

Hours 

L 70 =91,400 hrs 

L 70 =52,200 hrs 

L 70 =22,290 hrs 

Figure 4: Chart showing the influence of drive current on LED 

degradation. 

The Importance of LEDSense® Technology 

Given the dramatic reduction in Lumen maintenance 

that results from operation at high current levels, it 

is important that a means be provided in the drive 

electronics to safeguard the operation of LED lighting 

products. Thermal fold-back provides that safety net. 

Thermal-fold back is important because: 

• It allows the maximum brightness and maximum 

lifetime regardless of conditions 

• It provides a “worry-free” solution to OEMs 

• It virtually eliminates the consequences of a bad 

installation in the field 

TerraLUX’s implimentation of thermal fold-back, called 

LEDSense ® , employs a microprocessor-controlled 

constant current driver. Figure 5 illustrates a block 

diagram of the essential features of the LEDSense circuit. 

Various buck or boost topologies are used depending on 

the input voltage range and the length of the LED string 

which determines the required output voltage. The 

temperature of the LED is measured via a thermistor 

which is located in the thermal path of the device so that 

the operating temperature of the LED can be determined. 

The microprocessor, via an A/D converter measures 

this value and compares it to the known operating 

characteristics of the LED via a built-in algorithm. The 

processor then sets the current of the driver through its 

D/A converter. With a properly designed and operating 

luminaire-lightengine combination, the current (and 

temperature) remains at the predetermined safe level. 

If temperature exceeds a preset threshold, an algorithm 

in the processor gradually reduces the current set point 

via the firmware’s algorithm to assure the longevity of 

the LED. The microprocessor is also used to analyze 

the waveform of the power source in order to tailor the 

driver operation to the particular dimmer-transformer 

combination in use, proving additional benefit to the 

OEM manufacturer. 

The resulting performance characteristic is shown in 

Figure 6. This figure compares the drive current to the 

temperature of the LED for two examples of an LED 

lightengine, the first (blue squares) without LEDSense ® 

technology and the other (red circles) with LEDSense ® 

operating. In this example the temperature that is being 

externally controlled is that of the back of the light- 

engine heat sink, but we have plotted the LED’s slug 


FEATURED PROJECT

PROJECT 

temperature; the dashed blue line is meant to illustrate 

the temperature offset that is the result of the thermal 

resistance of the assembly and the drive power level. 

Figure 5: Schematic diagram showing the major functional areas 

of the microprocessor based LEDSense thermal fold back 

Drive Current, (Amps) 

Microprocessor 

ROM 

Current Temperature 

Data 

Digital/Analog 

Converter 

1.1 

1 

0.9 

0.8 

0.7 

0.6 

0.5 

0.4 

25 

Firmware 

Waveform Detection 

Based Dimming Algorithm 

Driver IC 

Analog/Digital 

Converter 

Thermal Foldback 

No Thermal Foldback 

L 70 >326,000 hrs 

Die Temp=123ºC 

LED Slug Temperature (ºC) 

L 70 =30,500 L 70 ~13,900 

35 45 55 65 75 85 95 105 115 125 

Figure 6: Comparison of the projected lifetime of LEDs with and 

without LEDSense based thermal fold back.. 

Also shown is the L70 time calculated for the LED 

according to the TM-21 standard (although once again 

I have extended this beyond the recommended time 

for the low current condition). The case where the LED 

temperature is uncontrolled, but is operated at the 

maximum current shows a dramatically shortened value 

of only 13,900 hours. In contrast, the LEDSense feature 

has reduced current to the extent that it has effectively 

“neutralized” the negative lifetime effect of the existing 

high temperature condition. Although in this instance the 

user will notice significant dimming, less dramatic overtemperature 

conditions may be hard to detect because of 

the eyes’s insensitivity at high brightness. Nonetheless, 

even in the region where there is only a slight overtemperature 

condition, the LEDSense algorithm will 

keep the LED safe. 

Conclusion 

Comprehensive standards have been developed by the 

industry to test LEDs and describe their degradation 

over time. So far however, these standards only allow 

prediction as a function of operating temperature. We 

have shown that the drive current in combination with 

operating temperature has an extremely important 

influence on LED lifetime as defined by L70. Thermal 

fold-back provides a useful method to ensure control 

within the safe operating envelope of LEDs ; TerraLUX’ 

LEDSense® technology has the added benefit of a 

quantitative control algorithm that assures both maximum 

LED lifetime and light output. 

References 

IESNA LM-80-08: “Method for Measuring Lumen 

Maintenance of LED Light Source”, American National 

Standards Institute 

IES TM-21-11: “Projecting Long Term Lumen 

Maintenance of LED Light Sources”, American National 

Standards Institute 

Eric Richman, “The Elusive ‘Life’ of LEDs: How TM-21 

Contributes to the Solution”, LEDs Magazine, November/ 

December 2011 ■ 


FEATURED PROJECT

FEATURED PRODUCTS 

VDD4 

I 2 C 

Multiplexers 

and Switches 

VDD3 

VDD2 

I 2 C 

A/D or D/A 

Converters 

I 2 C 

General Purpose 

I/O Expanders 

PCA9541 

I 2 C 

Master Selector/ 

Demux 

I 2 C 

Serial EEPROMs 

VDD0 

VDD1 

LCD Drivers 

(with I 2 C) 

I 2 C 

LED Controllers 

I 2 C 

Repeaters/ 

Hubs/Extenders 

I 2 C Port 

via HW or 

Bit Banging 

I 2 C 

Bus Controllers 

I 2 C 

Real Time Clock/ 

Calendars 

8 

I 2 C 

DIP Switches 

MCUs 

MCUs 

I 2 C 

Temperature 

Sensors 

VDD5 

I 2 C 

Slave 

Bridges 

(with I 2 C) 

SPI 

UART 

USB 

002aac858 

Ultra Fast-Mode I2C-Bus Controllers 

NXP Semiconductors N.V. introduced the industry’s first highperformance 

I²C-bus controllers capable of handling both Fast-mode 

Plus (Fm+) and the new Ultra Fast-mode (UFm) specification, which 

has transmit-only data transfer rates up to 5 Mbit/s. By providing one very 

large 4.25-kB data buffer per channel and significantly reducing interrupts 

to the host processor, the PCx966x product family has been optimized 

for efficient I²C designs in repetitive data-intensive LED controller and 

stepper motor applications, such as those found in the gaming industry. 

Invented by NXP (formerly Philips Semiconductors) over 30 years ago, the I²C bus has revolutionized chip-to-chip 

communications by replacing complex parallel interfaces with a straightforward yet powerful serial structure using 

a simple two-wire format. The I²C bus continues to be used extensively for system management and control in 

computing and enterprise equipment, and in portable and consumer applications, where it shrinks the IC footprint 

and leads to lower system costs. For more information, please click here. 

Highly Integrated Audio Codec 

STexas Instruments Incorporated introduced the industry’s most highly 

integrated audio codec with embedded miniDSP cores, providing 

echo and noise cancellation at wideband voice sampling rates up 

to 16 kHz. The TLV320AIC3262 integrates five amplifiers and two 

miniDSP cores, and gives designers the ability to interface to up to three 

devices simultaneously, such as application, Bluetooth and baseband 

processors. Audio and voice samples can be received, mixed and 

processed seamlessly within the codec. The inclusion of TI audio and 

voice algorithms, as well as third party algorithms, available on the codec 

and as additional licenses, benefits designers creating multi-purpose 

and high-definition audio designs for mobile devices. For more information, please click here. 

Multi-Gigabit Serial Link Analysis 

Linear Technology introduces the LTM9012, a quad 14-bit, 125Msps 

µModule® analog-to-digital converter (ADC) with integrated fixed 

gain drivers, passive filtering and bypass capacitance. The integrated 

µModule converters offer dramatic reduction in board space for high 

channel-count applications as diverse as medical imaging systems 

and MIMO (multiple input multiple output) 4G base stations. This 

high level of integration enables smaller boards with greater density, 

while eliminating costly layout iterations often required to optimize the 

driver-to-ADC interface. This results in a significant reduction in design 

and debug time and faster time to market. Equivalent implementations require five devices and dozens of passive 

components compared to the LTM9012 in an easy-to-use 15mm x 11.25mm BGA µModule package. For more 

information, please click here. 


FEATURED PRODUCTS

Transform Your iPhone, iPad 

or iPod into an Oscilloscope 

with the iMSO-104 

Begin Your Experience Now 

Experience the iMSO-104 as Joe 

Wolin, co-founder of EEWeb, 

gives you an in-depth look into 

the future of oscilloscopes. 

ELECTRONICS 

ELECTRONICS 

UBM UBM 

2012 

WINNER

Illogical Logic 

Part 1 - Boolean Algebra 

Paul Clarke 

Electronics Design Engineer 

When it comes to logic, we know it’s all supposed to 

make sense. For newcomers, it can also be very confusing 

to wrap your head around these concepts. This is why I 

have decided to do a short series on understanding the 

illogical world of logic! 

For the most part, understanding basic logic gates is easy 

enough. They explain what they are clearly; an AND gate 

just says the output is: logic ‘1,’ then input ‘x’ AND ‘y’ are 

logic ‘1.’ If you’re not 100% on this and other logic gates, 

then a quick read on Wikipedia will help set you straight. 

What becomes confusing is that we use lots of logic gates 

together, like in an FPGA. So, how do you work out what 

you need and why do some people seem to use so few 

gates for such complex tasks? 

Boolean algebra is a way of explaining logic in a written 

form without having to draw out all the logic gates. In 

place of an AND gate, you simply write A.B (note the full 

stop), and for the OR function you use the plus symbol (for 

example: A+B). This means you can turn complex logic 

into one written line of Boolean (Figure 1). 

What’s shown in Figure 1 quickly becomes… 

However, Boolean allows you to do things you cannot see 

or work out from a logic circuit. Boolean allows you to 

apply simple rules that will enable you to break down the 

logic to simply the elements that matter. 

EEWeb | Electrical Engineering Community Visit www.eeweb.com 17

TECHNICAL ARTICLE 

Figure 1 

There are three sets of rules that I 

use to help break down Boolean 

into more simple logic: 

1. Break (or make) the line – 

change the sign (DeMorgan’s 

Theorem) 

If you have a simple logic gate like 

the NAND gate, then you write: 

What you will find is that if you were 

to invert (NOT) the logic levels of A 

and B to get the same logic result 

you would OR the inverted A and 

B lines. By breaking the line above 

the symbol and changing the sign, 

it keeps the logic true: 

2. Disappearing gates 

When a gate has fixed inputs say at 

logic ‘1’ or ‘0’, then the output also 

becomes fixed. That’s because you 

are restricting the combination of 

outputs available. So the following 

allows you to remove gates 

completely from the circuit and 

replace them with either a fixed 

logic level or carry the logic signal 

forward. 

3. Adding fixed logic levels 

This allows for making a logic gate 

have more than n inputs. By adding 

a fixed logic ‘1’ or ‘0’ input, then 

that function of the gate remains 

the same. However, it allows for 

simplification of two gates with 

common inputs (explained in 

example at the end). 

4. The “because it works” rule 

These can be explained, but last 

time I tried it took ages! So, like 

the lecturers and teachers that 

introduced me to Boolean, I’ll say 

“just write these down because they 

work.” 

(And also to say this post would 

become very long!) 

The following is an example of 

breaking down the logic into its 

simplest form: 

Consider the second and third 

terms—the A.B is common to both. 

Now imagine that the third term 

also has a third input. This would— 

for the AND gate to work—have to 

be at logic ‘1’ as explained in my 

third set of rules. This allows you to 

combine the Boolean together into: 


TECHNICAL ARTICLE


You will now see that the C element 

of this Boolean is irrelevant as ORing 

anything with a ‘1’ vanishes. So: 

Again ANDing a ‘1’ also vanishes so 

in this case, we end up with just: 

Don’t believe me – try it! 

Our logic now looks like this: 

Once again we can combine inputs 

in this case with the logic A input to 

get: 

Which then becomes: 

The logic ‘1’ disappears in the AND 

gates leaving us with just: 

We can now see that the logic A 

input has no effect on the circuit and 

can just be removed. 

It’s using these simple rules that 

allows us to reduce complex 

requirements down to simple logic. 

I’m not saying that all logic can be 

reduced this much, being that this 

was an example, but it’s important 

to remove this dead logic. When 

I started electronics it meant 

reducing the numbers of chips on 

a PCB. Now in the modern day of 

high speed electronics it means 

you can reduce switching times 

and the number of gates used in an 

FPGA. In fact, if you are an FPGA 

programmer and wonder why it 

takes so long to generate the logic, 

you can now see why, because it’s 

doing all of this for you. 

I’ve not shown an example using 

my first set of rules, known as 

DeMorgan’s Theorem, however, 

you can use it to great effect on its 

own in many cases. It can also be 

used as a method to generate an 

expression that allows you to apply 

the other rules to it. 


Electrical Engineering Community 

Join Today 

www.eeweb.com/register 

Next time I’ll be looking at Karnaugh 

maps… 

About the Author 

Paul Clarke is a digital electronics 

engineer with strong software skills 

in assembly and C for embedded 

systems. At ebm-papst, he develops 

embedded electronics for thermal 

management control solutions 

for the air movement industry. 

He is responsible for the entire 

development cycle, from working 

with customers on requirement 

specifications to circuit and PCB 

design, developing the software, 

release of drawings, and production 

support. ■ 


TECHNICAL ARTICLE

PWM DC/DC Controllers with VID Inputs for Portable 

GPU Core-Voltage Regulator 

ISL95874, ISL95875, ISL95876 

The ISL95874, ISL95875, ISL95876 ICs are Single-Phase 

Synchronous-Buck PWM regulators featuring Intersil’s 

proprietary R 4 Technology. The wide 3.3V to 25V input voltage 

range is ideal for systems that run on battery or AC-adapter 

power sources. The ISL95875 and ISL95876 are low-cost 

solutions for applications requiring dynamically selected 

slew-rate controlled output voltages. The soft-start and dynamic 

setpoint slew-rates are capacitor programmed. Voltage 

identification logic-inputs select four (ISL95875, ISL95876) 

resistor-programmed setpoint reference voltages that directly set 

the output voltage of the converter between 0.5V and 1.5V, and 

up to 5V with a feedback voltage divider. 

Compared with R 3 modulator, the R 4 modulator has equivalent 

light-load efficiency, faster transient performance, accurately 

regulated frequency control and all internal compensation. These 

updates, together with integrated MOSFET drivers and Schottky 

bootstrap diode, allow for a high-performance regulator that is 

highly compact and needs few external components. The 

differential remote sensing for output voltage and selectable 

switching frequency are another two new functions. For 

maximum efficiency, the converter automatically enters 

diode-emulation mode (DEM) during light-load conditions, such 

as system standby. 

RTN1 

+5V 

March 2, 2012 

FN7933.1 

R FB1 

R OFS1 

GPIO 

C SOFT 

R VCC 

C PVCC 

16 

1 

GND BOOT 

12 

2 

RTN UGATE 

11 

3 

EN PHASE 

10 

4 

SREF PGOOD 

9 

5 

PGND 

FSEL 

15 

LGATE 

FB 

6 

14 

PVCC 

OCSET 

7 

13 

8 

R OFS 

VCC 

VO 

C VCC 

R PGOOD 

R FB 

C BOOT 

Features 

• Input Voltage Range: 3.3V to 25V 

• Output Voltage Range: 0.5V to 5V 

• Precision Regulation 

- Proprietary R 4 Frequency Control Loop 

- ±0.5% System Accuracy Over -10°C to +100°C 

• Optimal Transient Response 

- Intersil’s R 4 Modulator Technology 

• Output Remote Sense 

• Extremely Flexible Output Voltage Programmability 

- 2-Bit VID Selects Four Independent Setpoint Voltages for 

ISL95875 and ISL95876 

- Simple Resistor Programming of Setpoint Voltages 

• Selectable 300kHz, 500kHz, 600kHz or 1MHz PWM Frequency 

in Continuous Conduction 

• Automatic Diode Emulation Mode for Highest Efficiency 

• Power-Good Monitor for Soft-Start and Fault Detection 

Applications 

• Mobile PC Graphical Processing Unit VCC Rail 

• Mobile PC I/O Controller Hub (ICH) VCC Rail 

• Mobile PC Memory Controller Hub (GMCH) VCC Rail 

FIGURE 1. ISL95874 APPLICATION SCHEMATIC WITH ONE OUTPUT VOLTAGE SETPOINT AND DCR CURRENT SENSE 

Q HS 

Q LS 

R OCSET 

Get the Datasheet and Order Samples 

http://www.intersil.com 

L O 

C SEN 

R O 

VIN 3.3V TO 25V 

CIN 

VOUT 0.5V TO 3.3V 

0 

CO 

RTN1 

Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2011, 2012 

All Rights Reserved. All other trademarks mentioned are the property of their respective owners.

TECHNICAL A System Perspective ARTICLEon 

Specifying 

Electronic Power Supplies: 

Efficiency 

A B 

Bob Stowe 

Power Supply Design Consultant 

In the last installment of this series entitled “A 

System Perspective on Specifying Electronic Power 

Supplies,” we discussed the effects of source 

characteristics upon power supply specification. In 

this installment, we will learn about the importance of 

efficiency for your system and how to specify it. 

What is Power Supply Efficiency? 

Figure 1 shows the typical power flow from a source, 

through the power supply, and on to the load. Power 

supplies are not ideal, so not all of the power supply 

input power is transferred to the load as useful power. 

A portion of the input power is instead dissipated to the 

power supply environment as heat — as represented by 

the red highlighting around the power supply. 

Power supply efficiency, then, is a measure of how much 

input power is transferred to the load as useful and 

desirable power, rather than dissipated in the form of 

heat in the power supply. Efficiency is expressed either 

as a percentage figure, or as a decimal figure. When 

expressed as a percentage, 100% is perfect efficiency 

and typical efficiencies for power supplies range 

SOURCE Power In POWER Power Out LOAD 

SUPPLY 

Figure 1 

Waste Power 

To Power Supply 

Environment 

anywhere from 35% to 96% depending on the type and 

application of the supply. When expressed as a decimal, 

1 is perfect efficiency and typical efficiencies range 

anywhere from 0.35 to 0.96. 

The following equation summarizes power flow: 

Pin = Pout + Pwaste 


TECHNICAL ARTICLE


Importance of Efficiency 

The importance of efficiency has three main aspects: 1) 

energy conservation, 2) package size, and 3) temperature 

rise. 

Energy Conservation 

Energy conservation is an important consideration in: 

1. Systems where the source is in the form of stored 

energy such as batteries or ultracapacitors, 

2. Energy harvesting applications. 

3. Green applications. 

With stored energy systems, power supply efficiency 

has a major impact upon battery life or battery and 

ultracapacitor discharge time. A perfect example is how 

long a notebook computer will be able to run while on 

battery. An efficient power supply will maximize battery 

discharge time. 

Energy harvesting is a relatively recent application for 

power electronics whereby energy is “captured” from 

the environment and converted to useful energy. Since, 

with present technology, the rate of capturing energy 

from the environment is relatively low, power supply 

efficiency plays a major role in converting as much of 

that energy as possible into useful power. 

Green applications are a long term vision for transforming 

our culture into responsible users of energy. Efficiently 

transforming energy is a main effort for green design. 

An example is the effort to switch from inefficient 

incandescent light bulbs to efficient flourescent which 

require efficient power supplies. 

Package Size and Temperature Rise 

To the engineer not well versed in power electronics, a 

less obvious effect of efficiency is power supply package 

size and/or power supply temperature rise. In today’s 

design world, the power supply is often thought of as 

a necessary complement to the main function of the 

product in design. But since the power supply is not the 

main function, it often takes a back seat in the design 

process. One of the natural results is that the power 

supply must be unobtrusive with small size. 

However, efficiency is one of the main determiners 

of power supply size. The reason for this is that the 

less efficient a power supply is, the more waste heat 

generated. For a given package surface area, the 

package temperature increases as the waste heat 

increases. Package temperature directly affects 

reliability and life. (An old thumb rule for reliability and 

life vs. temperature is that each 10 degree C increase 

in temperature reduces reliability and life by a factor of 

two.) In other words, for a given package temperature 

which results in a given reliability and life, greater waste 

heat requires greater package surface area or a more 

sophisticated and more expensive waste heat removal 

method. 

As an example, for a given input power, an 80% efficient 

power supply requires twice the surface area to 

maintain the package at a given temperature compared 

to a 90% efficient power supply. Required surface 

area is proportional to the complement of efficiency 

(1-Efficiency) when expressed as a decimal. 

How to Calculate Efficiency 

Calculating efficiency in all cases can be done by 

dividing the power output by the power input: 

Efficiency 


= h = 

P 

P 

Power is simply RMS voltage times RMS current 

multiplied by the power factor if the input is AC, or just 

voltage multiplied by current if the input or output is DC. 

Power factor is the distortion factor multiplied by the 

displacement factor. The distortion factor accounts for 

the effect of a non-linearly changing power supply input 

impedance over one line cycle. The displacement factor 

accounts for an effective phase difference between line 

voltage and line current due to reactance at the input of 

the power supply. 

Linear Regulator Efficiency 

In the special case of a DC input linear regulator, the 

efficiency calculation is simply the output voltage divided 

by the input voltage. 

Switching Power Supply vs. Linear 

Power Supply Efficiency 

In most applications, switching power supplies are more 

efficient than linear power supplies, and therefore offer 

smaller size due to the lesser waste heat. Switching 

out 

in 

TECHNICAL ARTICLE


power supply efficiencies typically range from 70% to 

96%. Linear power supplies efficiencies can be 35% or 

even lower, requiring larger sizes to handle the greater 

waste heat. 

One case where the linear power supply can offer 

comparable or even better efficiency than a switching 

power supply is the case of a low drop-out regulator with 

a relatively high output voltage. In this case, the voltage 

dropped across the regulating pass element is a very 

small part of the input voltage, and the output voltage is 

near the input voltage. Efficiencies can easily be over 

90%. 

How to Specify Efficiency 

Efficiency is best specified for applications requiring 

energy conservation as discussed earlier. Efficiency 

varies depending on input voltage and load current. 

Optimal efficiency should be specified at the operating 

point(s) where the product is most likely to operate. For 

other operating points, a tolerable minimum should be 

specified. 

For other applications not involving energy-limited 

BeStar® 

ACOUSTICS & SENSORS 

PRODUCTS 

Speakers 

Buzzers 

Piezo Elements 

Back-up Alarms 

Horns 

Sirens/Bells 

Beacons 

Microphones 

Sensors 

INDUSTRIES 

Automotive 

Durables 

Medical 

Industrial 

Mobile 

Fire / Safety 

Security 

Consumer 

Leisure 

sources such as batteries, ultra-capacitors, energy 

harvesting, or green applications, it is best not to specify 

efficiency. Instead, other requirements such as package 

size limits, and/or temperature rise limits should be 

specified. Efficiency in these cases should be left to 

the power supply designer as a design variable that 

is determined based on other requirements such as 

package size limits and temperature rise limits that are 

more typically specified by the application demands. 

About the Author 

Bob Stowe is currently working at True Power Research 

as a Power Supply Design Consultant. He has over 21 

years of experience in the various disciplines as related 

to electronic energy conversion, possesses a master’s 

degree in power electronics, and is a member of IEEE 

in good standing. He also has obtained his certification 

in power electronics from the University of Colorado 

(COPEC). Additionally, he graduated from the United 

States Naval Academy in 1984 with a Bachelor’s degree 

in Electrical Engineering and served for five subsequent 

years as a United States Naval Officer. As a former military 

officer, he is familiar with military project requirements. ■ 

Teamwork • Technology • Invention • Listen • Hear 

Preferred acoustic component 

supplier to OEMs worldwide 

bestartech.com | sales@bestartech.com | 520.439.9204 


QS9000 • TS/ISO16949 • ISO14001 • ISO13485 • ISO9001 

TECHNICAL ARTICLE

RETURN TO ZERO 


RETURN TO ZERO

RETURN TO ZERO 


RETURN TO ZERO

Anthony Catalano - EEWeb

Create successful ePaper yourself

Delete template?

Save as template?