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A Supplement to Advantage Business Media
February 2012
www.ecnmag.com
25-Watt AC-DC Power Supply
Comes In a Chassis Mount CaseConTech introducedthe CM25 Seriesof
AC/DC switch-ing power supplies.The supplies offer 25Watts of fully
regu-lated output power
in a chassis mount case. The easily accessibleterminal block and
output voltage adjustmentpotentiometer give it the versatility to
be usedas a power solution in a large assortment ofapplications.
The CM25 Series has a universalinput voltage range of 88 V to 264
VAC. Theseries offers output voltages of 5 V, 12 V, 24 Vand 48 VDC,
with efficiencies up to 83 per-cent. The CM25 Series has protective
featuressuch as, short circuit, over voltage, and over-load
protection. The metal cage type chassismount case is designed for
free air convectioncooling. The series is rated for 3000 VAC
iso-lation, is RoHS compliant, and has UL 60950approval
pending.
ConTech, 877-302-4411,www.contech-us.com
POWER
INSIDE:
- What Type of LED Driver or Power Supply Do I need?
- Making Power Protection Smarter and Greener
- Energy Harvesting Enables Ultra-Low Power Applications- Is
Digital Power the Right Choice?
- New Products
USB Controlled Power MeterOperates Over 9 kHz to 3 GHz
Teseq has introducedthe new model PMU6003 to its power
meterproduct range. Theinstrument is designed
for a variety of applica-tions over the frequency range of 9 kHz
to3 GHz. Features include a large dynamicrange of more than 65 dB,
a high measure-ment speed of
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By Mel Berman, TDK-Lambda Americas,
www.us.tdk-lambda.com
C
onventional AC-DC power supplies and DC-DCconverters provide an
output that is regulated to
provide a constant-voltage. However, LEDs work
most efficiently and safest with a constant-current drive. As a
result,many new devices have been developed to provide this type of
LED drive.LED power sources that provide a constant-current output
have typically
been referred to as LED drivers. In the past, AC-DC power
supplies that
provided a regulated constant-voltage to LEDs were referred to
as LEDpower supplies. Today, the terms LED driver and LED power
supply are
used interchangeably. The important thing to keep in mind is
whether theoutput of the power device provides a constant-voltage
or a constant-
current as is required by the LED device that is receiving the
power.
When Do I Need a Constant-voltage LED Driver?Most commercially
available LED light modules are constructed by con-
necting a number of LEDs in series or parallel to form cluster
or string
configurations. In cases where these light modules include a
constant-cur-rent driver as part of the assembly, an external
constant-voltage driver
or power supply is required. Low cost LED circuits control the
currentflowing through the LED with a simple resistor. This is
another case where a
constant-voltage power source is required. Other examples where
constant-voltage supplies have been employed include backlit ad
signs, traffic infor-
mation signs and large screen high definition LED displays, such
as thosedescribed in this article:
http://www.ledsmagazine.com/products/20877.
Constant-voltage drivers come in many differ-
ent forms. They can look like a conventionalpower supply or they
can be enclosed for
moisture and environmental protection.
When Do I Need a Constant-current LED Driver?
In cases where a manufactured cluster or string of LEDs does not
includean internal constant-current driver, an external LED driver
or power sup-
ply that provides a constant-current is required.
Constant-current LED
drivers are available in many different package configurations,
rangingfrom integrated circuits to enclosed moisture-proof
packages, dependingon the application and the required output
power.
Series and Parallel LED Configurations
Depending on the application, LEDs can be connected in series
and/or
parallel configurations. Obviously, when LEDs are connected in
series the
forward voltage drop of each LED in the string are additive. For
example,if you put 15 LEDs in series and each one has a voltage
drop of 3 V (at its
nominal current), you need to provide a voltage source of 45 V
(15 x 3 V =45 V) to drive the required current. This is why
constant-current drivers
always include in their specs the output voltage range that it
is capable of
providing to overcome the LED voltage drops. In order to limit
the drivevoltage to reasonable levels, multiple strings of
series-connected LEDs canbe placed in parallel and driven by
multi-output constant-current drivers.
How is LED Dimming Accomplished?
The light output of LEDs can be controlled by varying the amount
of
current flowing through the LED (within defined limits) or by
turning theLED on and off via pulse-width-modulation (PWM). LED
drivers like the
ALD6 Series have the capability of providing dimming by both of
thesepopular methods.
The drawing above shows the two methods of light dimming that
areincluded in the ALD6 LED driver. It is permitted to use a
combination of
both of these methods simultaneously. The Rbr is an external
variable
10k ohm resistor input. By varying this potentiometer from 1 k
to 10 kohms, an analog dimming control is achieved. In this case,
the maximum
LED brightness occurs when the pot is set to 10k ohms. This same
inputcan operate with variable analog voltage ranging from 1.6 V to
3.8 V. In
some applications, this input can be connected to a temperature
sens-
ing device that could reduce the current flow through the LEDs
as thetemperature rises, thus providing a means for temperature
compensation.
The Vpwm is a Pulse-Width-Modulation input that controls the
LED
brightness by varying the duty-cycle of the input signal from 1
percent to100 percent. Typical PWM frequencies can range from 180
Hz to 270 Hz.
It is permitted to use a combination of both of the methods of
lightdimming that are included in the ALD6 LED driver
simultaneously. The
Rbr is an external variable 10 k resistor input. By varying this
poten-tiometer from 1 k to 10 k, an analog dimming control is
achieved.
In this case, the maximum LED brightness occurs when the pot is
set to10. This same input can operate with variable analog voltage
ranging
from 1.6 V to 3.8 V. In some applications, this input can be
connected to
a temperature sensing device that could reduce the current flow
throughthe LEDs as the temperature rises, thus providing a means
for tempera-
ture compensation. The Vpwm is a Pulse-Width-Modulation input
that
controls the LED brightness by varying the duty-cycle of the
input signalfrom 1 percent to 100 percent. Typical PWM frequencies
can range from180 Hz to 270 Hz.
More information about LED drivers, LED power supplies, and
applica-tions can be found at the following web link:
http://www.us.tdk-lambda.
com/lp/products/ledsigns.htm
What Type of LED Driver orPower Supply Do I Need?
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Power
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S4
02/2012 www.ECNmag.com
By Frank DeLattre, President, VYCON, www.vyconenergy.com
Clean, uninterrupted power is the goal of every facil-
ity, data center manager and executive overseeing
continuous business operations and processes.
With brownouts and blackouts occurring more often than
ever, businesses need critical power protection. According to
the ElectricalPower Research Institute (EPRI), power disturbances
cost U.S. industry
as much as $188 billion per year in lost data, material and
productivity. In
order to minimize these losses, annual spending on backup power
systems
exceeds $5 billion worldwide, according to industry analysts at
the Darnell
Group.
Traditionally, these systems include uninterruptible power
systems
(UPSs) with valve-regulated lead acid (VRLA) batteries to
provide energy
during short-term power disturbances, diesel generators
(gensets) for lon-
ger-term outages, and control electronics to bridge the two.
However, fly-
wheels and battery/flywheel combinations are common purchases
amongfacility mangers and data center managers looking to enact to
sustainability
initiatives and reduce total cost of ownership (TCO) expenses,
while still
maintaining high-9s of availability.
Flywheel Basics
A flywheel system works like a dynamic battery that stores
energy kineti-
cally by spinning a mass around an axis. Electrical input spins
the flywheel
rotor up to speed, and a standby charge keeps it spinning 24/7
until called
upon to release the stored energy. The amount of energy
available and its
duration is proportional to its mass and the square of its
revolution speed.
In the flywheel world, doubling mass doubles energy capacity,
but dou-
bling rotational speed quadruples energy capacity.
During a power event, the flywheel will provide backup power
seamless-
ly and instantaneously. Its important to know that EPRIs
research shows
that 80 percent of all utility power anomalies/disturbances last
less than
two seconds and 98 percent last less than 10 seconds. In the
real world,
the flywheel energy storage system has plenty of time up to a
couple of
minutes to gracefully hand-off to the generator.
From 40 kVA to multimegawatt, flywheel systems are increasingly
being
used to assure the highest level of power quality and
reliability in a diverse
range of applications. The flexibility of these systems allows a
variety ofconfigurations that can be custom-tailored to achieve the
exact level of
power protection required by the end user based on budget, space
available
and environmental configurations. In any of these
configurations, the user
will ultimately benefit from the many unique benefits of
flywheel-based
systems, including:
No down time for regular maintenance (no bearings to
replace)
High-power density, small footprint
Scalable / Parallel capability that allows for future
expansion
Fast recharge (under 150 seconds)
No special facility requirements No special / additional cooling
required
Low maintenance
20-year useful life
Simple installation
N+1 redundancy options
Quiet operation
Wide temperature tolerance
Flywheel implementations comply with the highest international
stan-
dards for performance and safety, including those from UL and
CE. They
also incorporate a host of advanced features that users expect
to make the
systems easy to use.
Best of Both Worlds
Hybrid flywheel/battery UPSs give users who need more backup
time the
reliability and green aspects of the flywheel system with
minutes of extra
runtime from the batteries. The flywheel is the first line of
defense against
power disturbances saving the batteries for prolonged power
outages. By
absorbing the power glitches, the flywheel can significantly
increase battery
life by handling over 98 percent of the discharges that would
normally have
shortened the batterys useful life.
Because of the extended runtime advantage, the flywheel/battery
hybrid
gives users further peace of mind for applications including
those withautomatic transfer switch (ATS) time delays and/or
synchronization time
requirements for multiple generators. Additionally, for hybrid
systems
requiring higher power, systems can be paralleled for longer
autonomy
and/or redundancy.
VYCONs hybrid system connects to the DC bus of a UPS.
Receiv-
ing charging current from the UPS, the hybrid system provides
clean DC
power to the UPS during discharge. VYCONs 99.4 percent efficient
system
includes patented technology consisting of a flywheel hub formed
from
aerospace-grade steel, a high-speed permanent magnet motor
generator,
a contact-free magnetic levitation system, and a touch-screen
display thatprovides vital information on system performance.
Innovative patented
technology enables the flywheel to charge and discharge at very
high
rates for countless cycles without degradation throughout its
20-year life.
Moreover, unlike other flywheels on the market, VYCON flywheels
do
not require replacement of bearings saving customers
approximately
$18,000 per flywheel every few years in maintenance costs and
eliminated
the six- to eight hours of downtime per flywheel needed to
change out the
bearings.
ConclusionThroughout the U.S. and around the world, data
centers, broadcasters,
hospitals, casinos, airports, industrial processes, military
facilities and other
critical applications are introducing clean flywheel energy
storage to their
UPS systems. Flywheels offer a green choice in protecting
critical opera-
tions, while providing the industry with a truly reliable DC
power solution.
Making Power ProtectionSmarter and Greener
Because of the extended runtime advantage, the
flywheel/battery hybrid gives users further peace
of mind for applications including those with
automatic transfer switch (ATS) time delaysand/or
synchronization time requirements for
multiple generators.
Power
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could harvest
energy from the
vibrations on the
bridge created by
moving vehicles.
A WSN powered
from a primarybattery requires
periodic main-
tenance. For
example, replac-
ing thousands
of batteries on a bridge would be a very costly (and dangerous)
endeavor.
Energy harvesting, in conjunction with a rechargeable battery or
capaci-
tor, could realize a perpetually-powered system. For a system
that uses a
primary battery, energy harvesting could extend the systems run
time and
reduce maintenance costs.Figure 1 is a typical system diagram of
a WSN, which consists of five
major components: the energy harvester, the energy storage
element and
power management circuitry, sensor, ultra-low power
microcontroller,
and low-power transceiver. The energy storage element is
required in
order to accumulate the energy for usage when the energy
harvester is not
harvesting energy, for example a solar panel system during the
night. The
S5
Energy Harvesting EnablesUltra-Low Power Applications
S5
Figure 1. Anatomy of a wireless sensor network incorporating
an
energy harvester.
Power
CHECK OUR INVENTORY AT:
www.fusesunlimited.comCALL: (800) 255-1919
The Circuit Protection SpecialistISO 9001:2008 Registered
FERRAZ SHAWMUT
By Brian Lum-Shue-Chan and Karthik Kadirvel, Texas Instruments,
www.ti.com
There are a variety of systems and applications that could
benefit
from energy harvesting (EH). Energy harvesting refers to the
tech-
nology by which ambient sources of energy such as light,
thermal
gradient, and vibration can be harvested and stored then applied
later for
doing useful work. Examples of systems that could benefit from
EH in-clude wireless sensor networks (WSNs), smoke alarms, wireless
keyboards
and mice. Each application is untethered to the power grid and
requires lo-
cal energy storage, such as batteries. EH enables a longer run
time, reduces
maintenance and in some cases, eliminates a battery altogether.
This article
explores a few applications where EH can be an enhancement.
As the name implies, WSNs are a network of sensors that
communicate
wirelessly and are self-powered. An example of a WSN is a
collection of
sensors that monitor a bridges structural integrity. The network
can be
distributed over a large area covering several square
kilometers. The in-
frastructure to provide wired communication with the sensors and
powerdistribution does not exist. It would be costly and
impractical to provide
this infrastructure. However, using energy harvesters allows
each sensor
node to be self-powered.
There are two types of energy harvesters that could be used for
this
application solar panels and/or vibration harvesters. Solar
panels could
harvest energy from the sunlight whereas a vibration-based
harvester
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By Bruce Haug, Linear Technology Corporation, www.linear.com
Experienced digital power users are normally well aware of the
benefits
of digital power system management. However, for those who are
con-
sidering whether it makes sense for their products, its benefits
may not
be so obvious. Typical questions being asked are: Will our
time-to-market
be longer when incorporating digital power? How difficult is it
to imple-
ment? How long is the learning curve? What is the additional
cost? Will ourcustomers value digital power? Will this technology
open up new markets?
Will we be left behind if we dont incorporate digital power into
our product
portfolio? The answers to these questions need to be understood
to help
determine if digital power is a good choice in the end
application.
Having digital control over analog power supplies with a simple
PC con-
nection is especially valuable during the development stage
where designers
PowerS6
02/2012 www.ECNmag.com
Is Digital Power the Right Choice?
Figure 1. LTC3880 applications schematic. Figure 2. Block
diagram on how to control 15 rails via an I2C/PMBus.
need to get their systems up and running quickly. There can be
as many as 30
point-of-load (POL) voltage rails and users need to be able to
easily monitor
and adjust supply voltages, sequence supplies up/down, set
operating voltage
limits, and read parameters like voltage, current and
temperature as well as
energy storage element must be rechargeable. The power
management is
critical as it interfaces to the harvester, charges the storage
element, and
provides power to the system. Sensor data is recorded and
processed by
the microcontroller. Finally, the data is transmitted to a
central host by thetransceiver.
Smoke and carbon monoxide detectors also can benefit from EH.
Cur-
rently, most of these devices are powered by primary batteries.
Replacing
these batteries is labor intensive and a huge annoyance because
usually
they are located in difficult to reach areas and are problematic
to change
at night. What often happens is that the detector is left
disabled which
creates a safety hazard!
Consumers definitely will benefit from the advantages that EH
will
bring to these detectors. Solar panels are a suitable source of
energy to
power a smoke detector. Smoke detectors use systems similar to
WSNs,except that they dont need a transceiver, and an audible alert
is required.
By incorporating EH, a more intelligent power management
architecture
is required so that maximum energy is extracted from the solar
panel and
charging and managing the rechargeable storage element is
provided. The
rest of the system can remain the same.
Another example of enabling an ultra-low power application with
EH
is for computer mice and keyboards where wireless communication
and
power from computer keyboards and mice is highly desirable. This
allows
for a cleaner, more organized desktop with flexibility in
movement and
placement of the components. Because the keyboard and mouse are
unte-
thered, they require a local source of power and wireless
communication.This is very similar to the requirements found in a
WSN.
As in our previous examples, battery replacement is an annoyance
and
adds cost to the lifetime usage of the product, and is not a
green solution.
Most computer equipment is operated in a home or office
environment
where ample light is available. This light can be harvested for
usage with
a solar panel integrated into the keyboard and mouse. Motion
also occurs
with both the keyboard and mouse. Harvesters can extract energy
from
this motion to power both devices.
In each of these applications, an integrated circuit (IC) that
can extract
the energy from the harvester and manage the storage element is
required.The BQ25504, a boost charger IC, can be used in these
systems. It has a
unique interface which maximizes the energy from solar or
thermoelec-
tric harvesters. This allows the system designer to use a
smaller (cheaper)
harvester since more energy is available for a given area or
volume. It also
has an industry leading quiescent current of 330 nA that enables
longer
application run time.
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access detailed fault logging via a digital interface. High
accuracy is extremely
important in these systems to maintain tight control over the
rails andachieve the maximum performance.
In data centers, a key challenge is to reduce overall power
consumptionby rescheduling the work flow and moving jobs to
underutilized servers,
thereby enabling shutdown of other servers. To meet these
demands, it isessential to know the power consumption of the
end-user equipment. A
properly designed digital power management system can provide
the user
with power consumption data, allowing for smart energy
management deci-sions to be made.
Knowing the condition and operating status of a voltage
regulator isperhaps the last remaining blind spot in todays modern
electronic systems,
since they normally do not have the means for directly
configuring or
remotely monitoring key operating parameters. It can be critical
for reliableoperation that a regulators output voltage drift over
time or an over tem-perature condition be detected and acted on
before a potential failure event
occurs. A well designed digital dower system can monitor the
performance of
a voltage regulator and report back on its health in so that
corrective actioncan be taken prior to it going out of
specification or even failure.
In order to protect expensive ASICs from the possibility of an
over voltagecondition, high-speed comparators must monitor the
voltage levels of each
rail and take immediate protective action if a rail goes out of
its specified safeoperating limits. In a digital power system, the
host can be notified when a
fault occurs via the PMBus alert line and dependant rails can be
shut downto protect powered devices such as an ASIC. Achieving this
level of protec-
tion requires excellent accuracy and very fast response
times.
Digital power management is being adopted because of its ability
to pro-vide accurate information about the power system and its
ability to autono-
mously control and supervise dozens of voltages with ease. It
can be verydifficult to probe around and monitor 30 POL voltages on
a complex system
board. System designers dont have to write a single line of code
unless theywant their host processor to read telemetry and do
simple fault intervention.
It is clear that manufacturers need to provide cost-effective
parts tailored andtargeted at specific niches that can be easily
implemented by new, as well as
experienced users.
Digital Power Done Right
Recently released dual output high efficiency synchronous
step-downDC/DC controllers are available with an I2C-based PMBus
interface for
digital power system management, and combine desirable analog
switchingregulator performance with precision mixed signal data
conversion for ease
of power system design and management. Software development
supportincludes an easy-to-use graphical user interface (GUI).
Linear Technologys LTC3880 and LTC3880-1, for instance, allow
fordigital programming and read back for real-time control and
monitoring of
critical point-of-load converter functions. Programmable control
param-
S7
www.ECNmag.com 02/2012
Power
Figure 3. LTC2978 controlling an external DC/DC converter.
eters include output voltage, margining and current limits,
input and output
supervisory limits, power-up sequencing and tracking, switching
frequencyand identification and traceability data. On-chip
precision data converters
and EEPROM allow for the capture and nonvolatile storage of
regulatorconfiguration settings and telemetry variables, including
input and output
voltages and currents, duty cycle, temperature and fault
logging.The LTC3880/-1 has an analog control loop for best loop
stability and
fastest transient response without the quantization effects
commonly found
in slower digital control loops. This device can provide two
independentoutputs or be configured for a two phase single output.
Up to six phases
can be interleaved and paralleled for accurate sharing among
multiple ICs,minimizing input and output filtering requirements for
high current and/or
multiple output applications. An integrated amplifier provides
true dif-
ferential remote output voltage sensing, enabling high accuracy
regulation,independent of board IR voltage drops. Figure 1 shows a
typical applicationusing the LTC3880 to develop 1.8 V at 20 A and
3.3 V at 15 A from a 12-V
bus voltage.
Configurations are easily saved to internal EEPROM over the
devices I2Cserial interface using GUI-based development software.
Onboard memory
allows for specific user settings. In addition, this controller
can power upautonomously without burdening the host processor.
Default settings can be
optionally configured by external resistor dividers for output
voltage, switchingfrequency, phase and device address. The
LTC3880/-1 has an onboard 16-bit
ADC that provides best in class programmability and telemetry
read-back.
Digital System Management for Real-Life Applications
A large multirail power board is normally comprised of an
isolated inter-mediate bus converter, which converts a 48 V, 24 V
or other voltage from
the backplane to a lower intermediate bus voltage (IBV),
typically 12 V that
MFG. CO. INC
800-542-3355www.calex.com
e-mail: sales @ calex.com
From Factory
Standards
to Custom Designs
Innovative DC/DC Solutions
from 1 to 800 Watts
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02/2012 www.ECNmag.com
Power11.1-V, 2.6-Ah Battery Pack withIntegral Charger Suits
Mobile Apps
Globtek offers a battery pack consisting of
three Samsung Li-Ion cells in a 3S-1P con-
figuration providing 28.86 WHr (2.6 AHr)of power to mobile
applications and other
applications requiring battery backup with
simple, cost effective charging. The GS-
1907 battery pack includes battery charger
circuits, thermal cut-outs and dedicated
safety circuit, and it can run stand alone power from GlobTeks
GT-41062
of GT-41080 18VDC external power supplies. It is configured in a
soft
pack with shrink wrap. The battery pack is compliant with
UL1642, UL
2054, UN38.3, and CE standards. Customizations including
connectors,
custom plastic enclosures, and alternate cell configurations and
quantitiesare available upon request.
Globtek,201-784-1000, www.globtek.com
Voltage Comparator Touts FastResponse Time, Low Current
Consumption
STMicroelectronics introduced a high-
speed voltage comparator with what it
asserts is the markets best ratio of cur-
rent consumption to response time. This
high-speed voltage comparator addresses
applications where fast response time is
critical, such as in data communications
equipment. When a noise occurs in the signal, for example,
minimized
delay helps ensure instant data recovery and thus maintain
failure-free
communication traffic flow. Fast-response comparators can also
find use
in pulse-width modulation for audio amplifiers or as output
buffers in
oscilloscopes and analog-to-digital converters. The TS3011
single com-
parator achieves a propagation delay of 8 ns while consuming 470
A of
supply current at 5 V.
STMicroelectronics, 781-861-2650,www.st.com
Lithium-Ion Battery-ChargingControl IC Supports USB Charging
Renesas Electronics Corporation
announced a charging control integrated
circuit (IC), the R2A20055NS, that achieves
further miniaturization and safe charging
control for single-cell lithium-ion batteries
used in portable devices. In addition to thefull complement of
protection features nec-
essary for portable equipment, including battery overvoltage
protection
and charging timers, the new IC includes functions that
implement the
charging profiles stipulated by JEITA, which allow the
R2A20055NS IC to
implement safe charging control. It provides control pins for
each block to
limit the input current. Current limit options are 100 mA, 500
mA, or no
limit; thus, it can perform battery charging according to the
USB power
available. The R2A20055NS input pins have high withstand voltage
of 25 V,
and the company has added new overvoltage protection functions
to the
input pins. These can protect application systems from the
overshoot thatoccurs when a power adapter or USB cable is
connected. The IC imple-
ments the functions in a 2.0 2.5 millimeter (mm)
ultra-miniature, high
thermal dissipation, 10-pin HUSON package, and thus can
contribute to
further miniaturization in portable equipment.
Renesas Electronics Corporation,
408-382-7500,http://am.renesas.com
is distributed around the PC card. Individual point-of-load
(POL) DC-DC
converters step down the IBV to the required rail voltages,
which normally
range from 0.6 V to 5 V with currents ranging from 0.5 A to 120
A. Figure
2 shows how a multi-rail system can be controlled with various
controllers
and DC/DC converters. The point of load DC/DCs can be
self-containedmodules, monolithic devices or solutions comprised of
DC-DC controller
ICs with associated Ls, Cs and MOSFETs. These rails normally
have strict
requirements for sequencing, voltage accuracy, over current and
over voltage
limits, margining and supervision.
Clearly, the sophistication of power management is increasing
and its
not uncommon for a circuit board to have over 30 rails. These
types of
boards are densely populated, and the digital power system
management
circuitry must not take up too much board space. It must be easy
to use and
be able to control a high number of rails. Linear Technologys
LTC2978, for
example, combines all the necessary features to work in
conjunction with theLTC3880/1 and LTC2874 to control up to 72
voltages on a single segment of
an I2C bus. The LTC3880/-1 controls, monitors and generates up
to two high
current rails. The LTC2978 controls and monitors up to eight
rails, and the
LTC2974 controls and monitors up to 4 rails. Such solutions must
operate
autonomously or communicate with a system host processor for
command,
control and to report telemetry. Figure 3 shows an example of
one channel of
an LTC2978 controlling a DC/DC converter.
The PMBus command language was developed to address the needs
of
large multirail systems. In addition to a well-defined set of
standard com-
mands, PMBus compliant devices can also implement their own
proprietary
commands to provide innovative value-added features. The
standardization
of the majority of the commands and the data format is a great
advantage to
OEMs producing these types of system boards. The protocol is
implemented
over the industry-standard SMBus serial interface and enables
programming,
control, and real-time monitoring of power conversion products.
Command
language and data format standardization allows for easy
firmware devel-
opment and reuse by OEMs, which results in reduced
time-to-market for
power systems designers. For more information, see
http://pmbus.org.
With over 75 PMBus standard command functions, users can take
full op-
erational control of their power system using one of the most
popular open
standard power-management protocols. Users can also generate
interruptrequests for the system controller by asserting an ALERT
pin in response to
supported PMBus faults. Linear Technologys LTpowerPlay GUI gives
users
easy access to the LTC3880/-1s operations and settings.
Conclusion
Digital power creates a new design environment for power
supplies which
adds value in several areas. First, having digital control over
analog power
supplies with a simple PC connection is valuable during the
development
stage enabling designers to get their systems up and running
quickly. Design-
ers of high rail count systems need an easy way to monitor,
control andadjust supply voltages, limits and sequencing.
Production margin testing is
easier to perform than traditional methods since the entire test
can be con-
trolled by a couple of standard commands over an I2C/PMBus
bus.
Power system data can be sent back to the OEM about the power
sup-
plies health, effectively opening up the blind spot with regards
to a DC/DC
converters well being. If a board is returned, the fault log can
be read back to
determine which fault occurred, the board temperature and the
time of the
fault. This data can be used to quickly determine root cause, to
determine
if the system was operated outside of its specified operating
limits or to
improve the design of future products.
A properly designed digital power management system provides the
user
with power consumption data, allowing for smart energy
management
decisions to be made, which can be used to reduce overall power
consump-
tion. Digital power is not all things to all people; however,
for high rail count
complex systems and OEMs who want to keep track of their power
systems
status it is a very powerful tool.
