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A S P E C I A L S U P P L E M E N T T O E D N
N O V E M B E R 2 0 0 5
A S P E C I A L S U P P L E M E N T T O E D N
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www.power-one.com 800.678.9445 805.987.8741
A Digital Power RevolutionA Digital Power Revolution
Z-One Digital IBA Integrates Power Management and Conversion System-level component count reduction improves cost, reliability, and power density.
GUI configuration and simulation dramatically simplifies power system development.
Industry-leading power conversion and management capabilities include programmable
output voltages, sequencing, tracking, and protection limits.
Vout 1 Vout 2 Vout 3(Up to 32 Outputs)
48V
I2C Bus
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IBA
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Z-Series Digital Power Manager Programs and manages Z-POL converters.
Monitors intermediate bus, accepts externalinterrupts, and initiates crowbar protection.
Facilitates Z-POL performance telemetry forremote monitoring and fault management.
Z-POL (Point-Of-Load) Converters Programmable 0.5 to 5.5VDC outputs
using 3.0 to 13.2VDC inputs.
Current densities up to 39 amps/in2.
Real-time reporting capabilities includevoltage, current, and temperature.
90% Reduction in Components, PCB Traces, and Development Time
Power-One and the Power-One logo, Z-One, ZIOS, Z-POL, and the Z Digital IBA logo are trademarks or registered trademarks of Power-One, Inc.
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A L L T H I N G S E L E C T R O N I C S T A R T W I T H M I C R O C H I P
The Microchip name and logo, the Microchip logo and PIC are registered trademarks of Microchip Technology Incorporated in the USA and in other countries. PICkit is a trademark of Microchip Technology
Incorporated in the U.S.A. and other countries. 2005 Microchip Technology Incorporated. All rights reser ved.
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Reed Business Information225 Wyman Street, Waltham, MA 02451
Phone: (781) 734-8000www.edn.com
EDNWorldwideStephen Moylan, President,
Boston Division/Publishing Director
Phone: (781) 734-8431Fax: (781) 290-3431
Cindy Fitzpatrick, Director
EDNCustom Publishing Services
Phone: (781) 734-8438Fax: (781) 290-3438
Heather Wiggins
Web/CPS Production Coordinator
Phone: (781) 734-8448Fax: (781) 290-3448
Contributing Editors:
Linnea C. BrushSenior Research Analyst
Jeremiah BryantResearch Analyst
Jeff ShepardPresident
A D V E R T I S E R I N D E X
American Power Design . . . . . . . . . .P24
Bear Power Supply . . . . . . . . . . . . . .P24
Bel Fuse . . . . . . . . . . . . . . . . . . . . .P19
Darnell Group . . . . . . . . . . . . . . . . . .P6
Digi-Key Corporation . . . . . . . . . . . . . .P3
Fairchild Semiconductor . . . . . . .Cover 4
Gaia Converters . . . . . . . . . . . . . . . .P30
International Rectifier . . . . . . . . . . . .P11
Intersil . . . . . . . . . . .P8, 21,26, Cover 3
Kepco Inc . . . . . . . . . . . . . . . . . . . .P29
Linear Technology Corporation . . . . . .P25
Martek Power . . . . . . . . . . . . . . . . .P15
Micrel . . . . . . . . . . . . . . . . . . . . . . .P28
Microchip Technology Inc . . . . . . . . . .P4
National Semiconductor . . . . . . . . . . .P7
Norvell Electronics . . . . . . . . . . . . . .P23
Power Integrations Inc . . . . . . . . . . .P12
Power-One . . . . . . . . . . . . . . . . .Cover 2
Spellman High Voltage . . . . . . . . . . .P20
Vicor . . . . . . . . . . . . . . . . . . . . . . . .P31
PART FOUR: EMBEDDEDPOWER 6Letter from the Editor
9Embedded PowerSupplies Reach New Heights
13CASE STUDY:
LINEAR TECHNOLOGY CORPORATION
How to Provide a Full-featured
Embedded POL DC/DC Converter
16AC Powering
Semiconductor Growth
18CASE STUDY:
TEXAS INSTRUMENTSScalable Power Systems Meet the Needs
of Configurable Blade Servers
22CASE STUDY:
FAIRCHILD SEMICONDUCTOR
PFC/PWM Combo IC Enables Best Power and
Board Space Efficiency in LCD TVs
27CASE STUDY:
POWER-ONE, INC.
Which Voltage Bus is Best?
Review the EDN Embedded Power
and Control Online Source List atwww.edn.com/supplements
NOVEMBER 2005 EDN POWER TECHNOLOGY P5
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6/36P6 EDN POWER TECHNOLOGY NOVEMBER 2005
A S P E C I A L S U P P L E M E N T T O E D N
P A R T F O U R : E M B E D D E D P O W E R
he market for embedded ac-dc power supplies and dc-dc converters is currently being driven by a number of technologies,including blade servers, Power-over-Ethernet (PoE), and the intermediate bus architecture (IBA). Combined with digital powermanagement and control, opportunities are emerging for higher wattage converters.
Blade servers are seeing growth that is more than three times faster than the server market as a whole, and their growth isone driver pushing the IBA. As a result, large original equipment manufacturers that were reluctant to move towards the IBA are
now employing it in their higher performance systems. In this issue, Texas Instruments discusses how they helped a customer design ascalable power system to meet the needs of configurable blade servers.
Both space and cooling are at a premium in networking systems powered via a 48V backplane. Therefore, it is extremely important forpoint-of-load converters to be both compact and efficient. Linear Technology provides a case study on supplying a POL dc-dc converter forembedded systems that meets or exceeds the multiple constraints of limited space and cooling within a given enclosure.
Powering challenges on the ac input side are equally demanding, with power factor correction (PFC), hot swappability, and pulse widthmodulation (PWM) posing special challenges. Semiconductor companies are providing products for this side of the house that range fromdigital PWM to One Cycle Control for PFC.
PFC, in particular, is gaining attention as new harmonic standards become mandatory in Europe and Japan, and efficiency programs(such as Energy Star) prescribe limits to power consumption. To address PFC regulations, Fairchild Semiconductor designed a PFC/PWMcombo integrated circuit to enable power and board space efficiency in LCD televisions.
As regulations change, and as digital power moves into the commercial mainstream, opportunities will emerge for power supplymanufacturers to increase efficiency and reduce costs. Power-Ones case study looks at how they helped a customer choose the rightintermediate bus voltage by using a digital power management system. The variety of solutions being offered, and the standards to supportthem, ensure that embedded power supplies will remain one step ahead of system needs.
LINNEA C. BRUSHSenior Research AnalystDarnell Group
LETTER from the EDITOR
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National Semiconductor Corporation, 2005. National Semiconductor, , and LLP are registered trademarks of National Semiconductor Corporation.
All rights reserved.
New Alternatives for Next-GenerationDC-DC Conversion
Alternative 2:LM5033 Intermediate Bus Converter (IBC)
Isolated step-down converter stage feeds multiplenon-isolated point-of-load (POL) converters
Each output is independently regulated
No feedback opto-coupler required
Integrated start-up regulator
Low primary component count Tiny, thermally enhanced LLP packaging
Buck stage regulates input to push-pull or
full-bridge isolation stage Accommodates wide input voltage range
No output filter inductors required
Lower voltage stress and switching loss inpush-pull switches
Ideal for multiple high-power outputs
Optimized for synchronous rectification
Alternative 1:LM5041 Current-Fed Converter
For FREE samples, evaluation boards,
datasheets, and more, visit us today at:
power.national.com
Or call 1-800-272-9959
Whatever Topology You Choose, National Has the Power Management Solution
LM5041 Current-Fed Converter
LM5033 IBC
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Intersil High Performance Analog
Intersil Switching Regulators
Intersil Switching Regulators for precise power delivery.2005 Intersil Americas Inc. All rights reserved. The following are trademarks or services marks owned by Intersil Corporation
or one of its subsidiaries, and may be registered in the USA and/or other countries: Intersil (and design) and i (and design).
The first line of defenseagainst heat is athermally-efficient HTSOP-28package, which utilizes an
exposed thermal padunderneath the IC to spreadheat through the PCB.
The VTJ pin is a
formula-based, accurate
indicator of the internal
silicon junction temperature.
If all else fails and the
temperature sensor indicates
a junction temperature above
135C, the PWM Regulatorwill shut down.
Key Features:
4A (EL7554) and 6A (EL7566)
continuous output current
Up to 96% efficiency
Built-in 5% voltage margining
3V-to-6V input voltage
0.58 in2 (EL7554) and 0.72 in2
(EL7566) footprint with
components on one side
of PCB
Adjustable switching frequency
to 1MHz
For more information and samples,
go to www.intersil.com/edn
Easy-to-use simulation tool also
available. Modify switching frequency,
voltage ripple, ambient temperature
and view schematics waveforms,
efficiency graphs and complete BOM
with Gerber layout.
www.intersil.com/iSim
Whats Black, White,and Cool All Over?Maintaining IC temperatures doesnt have tobe a riddle. Intersil's new high currentIntegrated FET Regulators have the industry'sonly true Thermal Protection with auto shutdown at 135C.
Intersil's EL7554 and EL7566 DC-DC buck regulators with internal
CMOS power FETs operate from 3V-to-6V input voltage and are
capable of up to 96% efficiency. But what's really cool about these
devices is ground breaking features like built-in Thermal Protection
and Voltage Margining for actual in-circuit performance validation.
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number of trends are converging that
are pushing embedded ac-dc power
supplies and dc-dc converter modules
towards higher wattages. Rapidly grow-
ing blade servers, Power-over-Ethernet (PoE) equip-
ment and several other devices are driving power
requirements higher. Shifting bus architectures have
an even larger effect on the embedded power supply
market. These shifts range from the growing usage of
the intermediate bus architecture (IBA), to alternative
powering trends, to the biggest potential change
digital power control and management. Combined,
these trends are driving opportunities for higher
wattage converters.
Gains made by the IBA and its hallmark busconverters are a primary driver of this trend. While
the IBA is clearly not new, the market acceptance of
the IBA is continuing to grow. Large OEMs that were
reluctant to move towards the IBA are now employing
it in their higher performance systems. Blade servers
are seeing growth that is more than three times faster
than the server market as a whole. Currently blades
account for a small portion of the server market, their
growth is one driver pushing the IBA.
Recently, a number of companies have released
new bus converters that illustrate growing interest in
the IBA. Power-One added a 46A quarter-brick bus
converter to its product line that delivers 441W. Tyco
Electronics introduced the QBK033 bus converter,
which the company claims
was the first 400W quarter-
brick power module. Artesyn
Technologies increased the
wattage of its highest power
quarter-brick bus converter to
450W, a 150W improvement
over its earlier generation
quarter-brick bus converter.
Similarly, the growing
usage of the IBA is driving
sales of Point-of-Load (POL)converters. The worldwide
non-isolated dc-dc converter
market, including POLs and
voltage regulator modules, is
outpacing the dc-dc converter
market as a whole. According
to the Darnell Group, rev-
enues in this market are projected to rise from $760
million in 2005 to $1.4 billion in 2010. A number of
new product offerings from companies in the Point-of-
Load Alliance (POLA) illustrate this trend.Ericsson Power Modules recently introduced 17
POLA-interoperable POLs in three platforms with cur-
rent ratings from 6A to 60A. One of these POL fami-
lies, the PMM series, is aimed at current-thirsty high-
end computer applications. It delivers 60A, while
achieving a 96% peak efficiency. Artesyn has devel-
oped 50A and 60A POL converters for the telecom
and datacom markets including blade servers, data
storage switches and voice-processing systems.
Texas Instruments has introduced the PTVxx010 8A
and PTVxx020 18A families of POLA compatibleplug-in power modules. While POLs are not specific
to the IBA, the growth of POLs coupled with the
A S P E C I A L S U P P L E M E N T T O E D N
P A R T F O U R : E M B E D D E D P O W E R
Embedded PowerSupplies Reach New Heights8 byJEREMIAH BRYANT
500W
2005 2010
2000
1500
1000
500
0
Worldwide DC-DC converter module market by wattage(millions of dollars)
Figure 1: Artesyn increased the power ofits latest Typhoon quarter-brick bus
converters to 450W
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expanding bus converter market illus-
trates the growing usage of the IBA.
While the IBA is creating architectur-
al power shifts within the system's box,
PoE is changing power requirements out-
side of the box. Like the IBA, PoE is
changing the power distribution mecha-
nism from the wall plug to the load. In PoE, power sourc-
ing equipment (PSE), typically either a PoE endspan inte-
grated into an Ethernet switch or a PoE midspan, deliver
power to a powered devices (PD), such as a VoIP phone,
Wi-Fi access point, flat panel PC and so on.
The PoE strategy increases power requirements
for the centralized PSE, especially for ac-dc front
ends, but typically replaces the power supplies for the
PDs with discrete components. Currently, PoE deliv-
ers only a maximum of 15.4W per port, which limits
the type of PDs that PoE can power and also limits
the power requirements of the PSE. However, the
IEEE has formed a study group that is examining
PoE-Plus, with the goal of at least doubling the power
level to 30W per port and possibly as high as 100W.
If PoE-Plus gains steam, ac-dc front ends will see a
greater opportunity, as will dc-dc converter modules.
Trying to capitalize on the growing PoE market,Astec Power has introduced the DS657, a 657W
power supply for PoE implementations. Phihong has
introduced a 275W power supply with integrated 24-
port PoE injection. Power Integrations has designed
new solutions for the PoE market, as they expanded
their DPA-Switch family
of ICs to include an option
for PoE.
The growing IBA mar-
ket is also yielding opportu-
nities for digital power con-trol and conversion
because systems that use
this architecture are going
to be the early digital
adopters. Thus far there
have been two primary dig-
ital implementation strate-
gies. The first strategy is
Power-One's proprietary Z-
One Digital IBA which is
a complete digital product line for the IBA. The sec-ond approach stems from the PMBus which
defines a standard way to communicate with power
converters using the SMBus in
order to configure, control and
monitor PMBus compatible
devices, such as converters or
power supplies. However, the
PMBus is only a communica-
tions standard and companies
are still developing complete digital power conversion
product lines. While there are a number of differences
between the two approaches, the primary difference
stems from the communications protocols and the
manner in which the parameters are set.
Power-One has two digital strategies. The first
strategy is the I2C pro-
grammable Z-7000 POLs
which are programmed
using the company's pro-
prietary software and can
be reprogrammed at any
time. Power-One's addi-
tional strategy is the one
time programmability
found in the Z-1000 No-
Bus POLs. These POLs
provide power management capabilities without hav-ing to implement external controllers and other asso-
ciated components.
Another digital communications approach origi-
nated from a collaborative open standardthe PMBus.
So far, Texas Instruments, Zilker Labs and Silicon Labs
have digital power controllers, but PMBus-complaint
digital dc-dc converters are just now hitting the market.
Several new digital products were unveiled at the
Digital Power Forum or shortly after. Artesyn Tech-
nologies announced a PMBus-compliant digitally pro-
grammable dc-dc converter. The DPL20C is a non-iso-lated POL that features digital configuration, monitor-
ing and diagnostic facilities accessible via the PMBus
interface. The 20A POL provides a programmable out-
put voltage from 0.6V to 5.5V, programmable sequenc-
ing, tracking and margining and real-time voltage, cur-
rent and temperature monitoring. Astec's first offering
from its Digital Power Initiative is the PMBus-complaint
DTX dc-dc converter. The DTX features integrated dig-
ital control with bi-directional PMBus communications
and includes self-diagnostics, efficiency optimization
and output impedance control in addition to dynamic
P10 EDN POWER TECHNOLOGY NOVEMBER 2005
A S P E C I A L S U P P L E M E N T T O E D N
P A R T F O U R : E M B E D D E D P O W E R
Figure 3: Power-One has expanded itsZ-1000 No-Bus family to include 7A,
15A and 20A POLs
(Embedded Power continued on P33)
Figure 4: Astec Powers first offering from itsDigital Power Initiative is the 50W DTX dc-dcconverter, which features integrated digital
control with bi-directional PMBuscommunication
Figure 2: Ericsson power modulesintroduced 17 POLA-interoperable POLs
capable of delivering 6A to 60A
-
8/14/2019 EDN 0504 Supplement
11/36Enter xx at www.edn.com/infoEnter xx at www.edn.com/info THE POWER MANAGEMENT LEADER
CAN YOUR BRICK DO THIS?
for more information call 1.800.981.8699 or visit us atwww.irf.com/dcdc
IRs DC Bus Chipset Enables Bricks With 48Vin, 9.6Vout, 330W at 97% Efficiency
International Recti f ier s new power
management DC Bus converter chipset
delivers 48V in , 9.6Vou t, over 330W at
97% efficiency for networking and
telecommunications systems.
Single DirectFET MOSFET can replace
two SO-8 devices
Reduces component count by > 45%
Achieves up to 1.5% better efficiency
compared to industry standard quarterbrick form factors
Reduces temperatures up to 40C
Board space reduced by 29% vs. quarter
brick form factors
Industry Best RDS(on) for IRF6644 (13m),
IRF6646 (9.5m), IRF6635 (1.8m)
Design Services available at www.mypower.com
New DC-DC Chipset Solution from International RectifierDirectFET MOSFETs
Part # Package VDSS RDS(on) max QG QGD
@ VGS=10V Typical TypicalIRF6644 Medium can 100V 13m 35nC 11.5nC
IRF6655 Small can 100V 62m 8.7nC 2.8nC
IRF6646 Medium can 80V 9.5m 36nC 12nC
IRF6613 Medium can 40V 3.4m 42nC 12.6nC
IRF6614 Small can 40V 8.3m 19nC 6.0nC
IRF6635 Medium can 30V 1.8m 47nC 17nC
Control IC
Part # Package Voltage Rating Description
IR2085S SO-8 100VPrimary-side half-bridge control IC,fixed 50% duty cycle, self-oscillating
IR2086S SO-16 100VPrimary-side full-bridge control IC,
fixed 50% duty cycle, self-oscillating
#
#
#
# IR product featured in Full-Bridge Bus Converter reference design above
Full Bridge DC Bus Converter
98
96
94
92
90
88
86
84
820 5 10 15
Load Current (A)
Full-Bridge Bus Converter Chipset (IRF6646, IR2086S, IRF6635 )48Vin/ 9.6Vout/ 175kHz
ElectricalEfficiency
(%)
20 25 30 35
4 x (80V) IRF6646 Primary2 x (30V) IRF6635 Secondary
97%
IR's proprietary DirectFET technology is covered by US Patent 6,624,522 and other US and foreign pending patent applications.DirectFET is a trademark of International Rectifier.
ReferenceDesignsAvailable
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A S P E C I A L S U P P L E M E N T T O E D N
P A R T F O U R : E M B E D D E D P O W E R
thesolutionFeature Rich IC Allows Optimum Flexibility
The penalty for poor tracking or sequencing is often
irreparable damage to devices in an embedded
system. FPGAs, PLDs, ASICs, DSPs
and microprocessors typically have
diodes placed between the core and
I/O supplies as a component of ESD
protection. If supplies violate the track-
ing requirements and forward bias the
protection diodes, the device may be
damaged.
Voltage sequencing, tracking, and margininghave become popular features in dc-to-dc convert-
er modules; however, these functions are less com-
monly found in dc/dc controller ICs. Linear
Technologys LTC3770 is an ideal solution for POL
dc/dc conversion needs and is also distinguished by
its fast transient response, a phase-locked loop
(PLL) that allows synchronization to a system clock,
and a highly accurate reference. Capable of operat-
ing from a 4V to 32V input, the current-mode con-
troller can produce a stepped down output at cur-
rents up to about 25A, see Figure 1.The LTC3770s constant on-time, valley cur-
rent-mode architecture, combined with a very low
minimum on-time (50ns typical), allows the control
loop to respond quickly to load steps. The LTC3770
can perform RDS(ON) current sensing by sensing the
voltage drop across the synchronous power MOS-
FET. Or for systems requiring more-precise control
of output current, a conventional sense resistor can
be used in the source of the lower MOSFET. In
either case, the current limit is user-programmable.
The controller can operate at very low dutycycles. In the extreme case, an output as low as 0.6V
can be supplied from input voltages as high as 32V -
New ICs Simplify Embedded POLDC/DC Converter Designs
8 byTONY ARMSTRONG, PRODUCT MARKETING MANAGER,
POWER PRODUCTS GROUP, LINEAR TECHNOLOGY CORPORATION
thechallengeMost embedded systems are powered via a 48V back-plane. This voltage is normally stepped-down to a lower
intermediate voltage of either 12V or 5V to allow power
to the racks of boards within the system. However,
most of the sub-circuits or ICs on these boards are
required to be powered at voltages ranging from 0.8V
to 3.3V at currents ranging from tens of milliamps to
tens of amps. As a result, a point-of-load (POL) dc/dc
converter is needed to step down the 12V or 5V to the
desired voltage and current level required by the sub-
circuits or ICs.
Since space and cooling are at a premium in
these systems, it is extremely important for any POLconverters to be both compact and efficient.
Furthermore, many microprocessors and digital signal
processors (DSPs) need a core power supply and an
input/output (I/O) power supply which must be
sequenced during start-up. Designers have to consider
the relative voltage and timing of core and I/O voltage
supplies during power-up and down operations to
comply with manufacturers specifications. Without
proper power supply sequencing, latch-up or excessive
current draw may occur that could lead to damage to
the microprocessors I/O ports or the I/O ports of a sup-
porting device, such as memory, programmable logicdevices (PLDs), field programmable gate arrays
(FPGAs), or data converters. To ensure that the I/O
loads are not driven until the core voltage is properly
biased, tracking of the core supply voltage and the I/O
supply voltage is necessary.
Although start-up and shutdown tracking can be
implemented externally for any given DC/DC converter,
the power supply sequencing requirements will vary
from system-to-system. These solutions include appli-
cation specific standard products (ASSPs) that can be
configured via a programmable interface or by external
components; programmable microcontroller-based
solutions and FPGA solutions.
CUSTOMERPROFILEA WORLDWIDELEADER INNETWORKINGSOLUTIONS FORTHE INTERNET
CASE Study
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A S P E C I A L S U P P L E M E N T T O E D N
P A R T F O U R : E M B E D D E D P O W E R
Figure 1. The LTC3770 steps down a 12V input to a 2.5-V output at 10 A
even under no-load conditions. In the applications
where such low output voltages are required, the pre-
cision of the chips voltage reference becomes signifi-
cant. The LTC3770 specifies an output voltage accu-
racy of 0.5% at room temperature and 0.67% from
0C to 85C. Across the devices full operating tem-perature range (40C to 85C), the total error on out-
put voltage is still only 1%.
The controllers operating frequency can be select-
ed by a single external resistor. For applications that
require stringent constant-frequency operation, a PLL
(phase lock loop) allows the LTC3770 to be synchro-
nized to an external clock, which helps reduce EMI.
In normal operation, the top MOSFET is turned
on for a fixed interval determined by a one-shot timer.
When the top MOSFET is turned off, the bottom
MOSFET is turned on until the current comparatorICMP trips, restarting the one-shot timer and initiating
the next cycle, refer to Figure 2. Inductor current is
determined by sensing the voltage between the
SENSE+ (PGND on the SSOP package) and SENSE-
(SW on the SSOP) pins using a sense resistor or the
bottom MOSFET on-resistance. The voltage on the ITHpin sets the comparator threshold corresponding to
inductor valley current. The error amplifier EA adjusts
this voltage by comparing the feedback signal VFBfrom a reference voltage set by the VREFIN pin. If the
load current increases, it causes a drop in the feed-back voltage relative to the reference. The ITH voltage
then rises until the average inductor current again
matches the load current.
At low load currents, the inductor current can
drop to zero and become negative. This is detected
by the current reversal comparator IREV which then
shuts off M2, resulting in discontinuous operation.
Both switches will remain off with the output capaci-
tor supplying the load until the ITH voltage rises abovethe zero current level (0.75V) to initiate another cycle.
Discontinuous mode operation is disabled by com-
parator F when the PFB pin is brought below 0.6V,
forcing continuous synchronous operation.
The operating frequency is determined implicitly
by the top MOSFET on-time and the duty cycle
required to maintain regulation. The one-shot timer
generates an on-time that is proportional to the ideal
duty cycle, thus holding the frequency approximately
constant with changes in VIN. The nominal frequency
can be adjusted with an external resistor RON.Over-voltage and under-voltage comparators OV
and UV pull the PGOOD output low if the output feed-
back voltage exits a 10% window around the regu-
lation point after the internal 25s power bad mask
timer expires. Furthermore, in an over-voltage condi-
tion, M1 is turned off and M2 is turned on immedi-
ately and held on until the over-voltage condition
clears.
Foldback current limiting is provided if the out-
put is shorted to ground. As VFB drops, the buffered
current threshold voltage ITHB is pulled down andclamped to 0.9V. This reduces the inductor valley
(New ICs Simplify continued on P32)
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mbedded power is used in a wide range
of distributed power architectures with
much of the design focus going to the
dc output side. Challenges on the ac
input side are equally demanding, however, including
power factor correction (PFC), hot swappability, and
pulse width modulation (PWM). Semiconductor com-
panies are providing products for this side of the
house that range from digital PWM (DPWM) to OCC
(one cycle control) for PFC.
PFC (power factor correction) is gaining attention
as new harmonic emission standards become manda-
tory in Europe and Japan. Other countries are at vari-
ous stages in accepting these standards which means
power supplies could be subject to more stringentrequirements. High minimum power factors are no
longer limited to high-power applications, for instance.
Newer norms and standards apply to products dissi-
pating as little as 75W or 26W for lighting devices.
Low PF results in poor electrical efficiency creat-
ing the need for larger generators, transformers and
other distribution devices that would otherwise not be
necessary. Other PF conditions include overloads,
voltage distortions, noise, parasitic harmonics in the
network, and
reciprocal inter-ference in the
system.
Analog-based
PFC control
methods have
long been used
in power sup-
plies. One PFC
control method
gaining in pop-
ularity is to usean analog controller with a discontinuous conduction
mode, such as Fairchild Semiconductors FAN7527B
and FAN4812. The company also introduced its new
FSAB20PH60 PFC smart power module which
implements the partial PFC switching converter cir-
cuit topology, switching at twice the line frequency of
the traditional PFC topology. The partial-switching
method is popular for 1kW to 3kW air conditioners.
International Rectifier introduced the IR1150
family of PFC integrated circuits for ac-dc PFC
circuits. IR utilizes its licensed OCC approach in the
IR1150 to deliver the perform-
ance of continuous conduction
mode (CCM) PFC with the sim-
plicity, reliability, and low compo-
nent count of a discontinuous
current mode circuit for PFCapplications. The company
claims that the patented OCC
technique radically alters tradi-
tional thinking about PFC solu-
tions. Its a form of CCM PFC
using a new integrator with reset
control block.
Companies are also looking at full digital power
factor correction, although these solutions can have
higher costs associated with them. Fairchild offers an
approach that features a control method based on amodified sinusoidal pulse width modulation.
Fairchilds proposed method does not need to sense
a line current or voltage, and can be implemented by
using one of their low-speed and low-priced conven-
tional microcontrollers.
Power Factor One Inc. uses its patented control
methods including constant pulse proportional cur-
rent, analog reset system, start enforcer and non-
linearity correction to significantly simplify the con-
verters circuit and improve the controllers perform-
ance. The company states that their PF484x PWMcontroller circuits include near-unity PFC circuits
that meet all international standards for electronic
P16 EDN POWER TECHNOLOGY NOVEMBER 2005
AC PoweringSemiconductor Growth8 byLINNEA BRUSH
Figure 2: TheGPTC110X series
from Green PowerTechnologies controlsPFC stages operating
under continuousconduction mode
conditions
Figure 1: International Rectifiers IR1150 family ofPFC ICs for ac/dc power factor correction circuits
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ballast and off-line power conver-
sion applications.
A modular approach for PFC is
provided by Green Power Tech-
nologies Ltd. The company claims
that their plug-and-play products
enable quick and easy integration of
critical components into OEM prod-
ucts with a resulting minimal bill of
materials that reduces costs. The
GPTC110X series is designed to con-
trol the PFC stages operating under
continuous conduction mode condi-
tions. It provides near-unity power factor for a univer-
sal input line (85Vac-265Vac) with no need for sens-
ing the input voltage. GPT is also finalizing develop-
ment of a digital power management module that
incorporates a PFC stage which is expected to be
commercially available within the next year.
A new PFC/PWM controller from ON
Semiconductor with integrated standby and high-
voltage start-up capabilities. The NCP1603 combines
a PFC controller chip and a PWM control chip in a
single, 16-pin SOIC package. Under light load condi-
tions the NCP1603 PWM controller disables the PFCfunction saving in the range of 200mW of power.
Another company looking at digital implementa-
tion is C&D Technologies. They recently presented a
paper at the Digital Power Forum that introduced a
digital/analog power-controlled 5500W rectifier with
three-phase ac input and high power factor. The
topology uses three FET PFC boost
switches and tolerates a wide input
range. Fault detection and control is
monitored by a microprocessor. The
generation of the control reference
for PFC correction is handled both
on an analog level and a micro-
processor level.
Zilker Labs has introduced the
ZL2005, a mixed-signal, power man-
agement and digital PWM IC that
integrates a compact, efficient buck
controller, high-current adaptive
drivers and full power and thermal management
functions in a single package, eliminating the need
for complicated power supply manager chips and
numerous discrete components.
Digital PWM control is also being slowly intro-
duced as a way of enabling high-frequency PWM
converter applications. Texas Instruments introduced
the UCD9501 high resolution DPWM controller
which is part of its Fusion Digital Power family of
products and can achieve up to 150 picoseconds
DPWM resolution.
Silicon Labs debuted the Si8250 DK, a develop-ment kit that includes tools for designing digital power
supply controllers. The kit includes a digital power
supply and PMBus adapter along with software
that the designer uses to describe the desired func-
tions of the controller. The code is synthesized, com-
piled, then put into the chip.
Companies like Roal Electronics are looking at
front-end power supplies with combined digital and
analog control. The company has a single output dig-
ital power front end with a patent-pending multi-
phase digital PFC. A single 8-bit microcontroller isused to manage the PFC, VBULK regulation, alarms
and signal monitoring. An interleaved two-transistor
forward converter PWM control is achieved by using
a standard, low-cost, 10-pin analog IC with direct dig-
ital integration for power management.
Ac powering may not be the primary focus of
many power supply design engineers, but the
demands of distributed power architectures will make
it a challenging area in the next few years. As regu-
lations change, and as digital power moves into the
commercial mainstream, opportunities will emergefor power supply manufacturers to increase efficien-
cy and reduce costs.
A S P E C I A L S U P P L E M E N T T O E D N
P A R T F O U R : E M B E D D E D P O W E R
Figure 3: ON Semiconductors NCP1603combines a PFC controller chip and aPWM control chip in a single, 16-pin
SOIC package
Figure 4: The Si8250DK is a development kit from Silicon Labs thatincludes tools for designing digital power supply controllers
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18/36P18 EDN POWER TECHNOLOGY NOVEMBER 2005
thesolutionTraditionally, configurable servers have been built
based upon an industry standard rack capable of hold-
ing up to 42, 1U (1.75 inches) servers. Since ac power
is bused through the server rack, each horizontally-mounted 1U server module requires one isolated ac to
dc power supply, or two if redundancy or
load sharing is required, and its own cooling
source. Consequently, a fully-configured 42,
1U rackmount server can house as many as
84 individual power supplies.
Blade servers are mounted vertically
into a 3U rack unit.
Each blade is really
nothing more than a sin-
gle board computer
complete with memory,
processor, and network
connections. By sliding
the blades into a com-
mon vertical enclosure, a larger number of
servers can fit into a smaller allowable spaceresulting in higher computing power density
compared to horizontal rackmount servers.
As many as 250 blades can be installed into
a single PCI based industry standard rack.
Unlike the 1U horizontal rackmount
servers, dc power in a blade server is distrib-
uted from one or more power supply mod-
ules through the PCI cabinet and to each of
the individual blades. Distributing dc power
means that the ac to dc isolation only has to
occur once through an intermediate busconverter. Since the blades themselves do
not have an on-board isolated power supply
or fan, bus power and cooling distribution
can be thought of as shared system resources. Blade
server power supply modules can now be paralleled
and hot-swapped for greater system flexibility and scal-
ability. In their earliest development, blades contained
only a single processor so power dissipation was not a
serious issue. However, the current trend is to pack as
many as four power-hungry processors onto a single
blade which greatly increases cooling demands. And,because the blades themselves are now dissipating so
Scalable Power Systems Meet the Needsof Configurable Blade Servers
8 bySTEVE MAPPUS, TEXAS INSTRUMENTS
CASE Study
thechallengeBlade server computing systems must be highly configurable to
meet a variety of application needs. As a result, blade servers
are bought and sold primarily based upon a desired amount of
processing power required to meet the needs of a specific task.
Ironically, one of the least considered, and yet most important,
components of a blade server is the power supply. After all, it
can be easily argued that a systems reliability is only as good
as the power supplied to it.
Texas Instruments recently worked with a customer wanting
to design a 1.5kW, highly-efficient, isolated power converter
module for a blade server application. This customer relies heav-
ily upon a well-known power module supplier for meeting his
power needs. Power converter modules offer many advantages,
but the foremost must be ease of implementation. However,there are several disadvantages with this approach, particularly
in blade server applications. Server systems are designed to be
highly-configurable in terms of available processing power. To
handle a variety of scalable power requirements, a configurable
server needs to be optimally matched to a compatible power sys-
tem. As a primary obligation, the customer desired more flexibil-
ity by closely matching their power needs and processor require-
ments. Secondly, because of specific supervisory and power
management requirements, the power modules themselves do
not make up a complete power system. And finally, the cus-
tomer emphasized the need to reduce overall power system
costs. Faced with a certain cost increase associated with out-sourcing a custom power converter design for their blade server
applications, this customer boldly decided to do the unthink-
able design his own custom power supply.
CUSTOMERPROFILEA LEADINGMANUFACTUREROF CONFIGURABLEBLADE SERVERCOMPUTINGSYSTEMS
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much additional power, there is an ever-increasing
demand to push for higher power supply efficiency.
Because the customer specializes in high-per-
formance computing systems with little to no previous
power supply design experi-
ence, designing an applica-
tion specific, custom power
supply was a significant chal-
lenge. TI worked closely with
the customer to first under-
stand their immediate power
requirements. The 1.5kW
converter needed to operate
from an off-line power factor
correction (PFC) regulated
boost converter. Initially, the
UCC38500 combination
PFC/pulse width modulation
(PWM) controller was con-
sidered, however this ap-
proach was eliminated
because it was limited to sev-
eral hundred watts of power.
A version of the full-bridge
power topology was really theonly practical choice and for
maintaining absolute highest
efficiency the UCC3895
phase shifted full bridge
(PSFB) PWM controller was
chosen along with a
UCC3817 PFC boost pre-
regulator. The PSFB control
technique differs from the
traditional PWM full bridge in
two ways. First, an intention-al delay time is introduced
where, under the right oper-
ating conditions, zero voltage
switching (ZVS) occurs
which would be essential for
meeting the customers need
for high efficiency. Secondly,
the duty cycle of each pri-
mary bridge MOSFET is fixed
at 50 percent, so instead of
the pulse width being controlmodulated it is the phase
shift (or phase overlap) that is controlled. For a compa-
rable component count, the PSFB offers ZVS, EMI and
performance benefits unmatched against the tradition-
al hard-switched full bridge technique.
EDN POWER TECHNOLOGY P19
A S P E C I A L S U P P L E M E N T T O E D N
P A R T F O U R : E M B E D D E D P O W E R
Dont let multiple source voltage designs slow you down! From SMT
point-of-load converters, to multi-phase VRMs and bus converters
for intermediate bus architecture, Bel has your DC/DC converter
modules in stock, and in volume! Our full lines are
engineered to optimize PCB space (8A in
0.2 x 0.2 footprint) and thermal perform-
ance (up to 94% efficiency) in 2.5V to
48V, and 1A to 200A applications.
Offered in low-profile and SIP packages,
our POL, step down, non-isolated, and
boost converters provide the features
todays networking, computing and
telecom designs demand. Regardless of
your requirements, Bel gets competitively
priced products to market faster.
DC/DC CONVERTERS
www.belpower.comTel:800/235-3873 Selector
Guide Available
Modules for 2.5V to 48V ApplicationsSpeed Time-to-Market
07CR Series of 1/8
Brick Bus Converters
-
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Optimizing the converter for high efficiency de-
pends upon a thorough understanding of parasitic cir-
cuit elements, such as MOSFET junction capacitance
and transformer leakage inductance. Even once these
nonlinear elements are defined, the ZVS critical timing
must be precisely adjusted to fully realize the convert-
ers efficiency benefits. Leveraging TIs expertise in ZVS
power topologies, the burden of climbing an otherwise
steep learning curve was
avoided. Throughout the
entire development cycle, TI
provided extensive design
support with specification and
design reviews, component
recommendations and sup-
port of initial hardware
debugging. Within nine
months, the customer had its
first in-house custom
designed power system
ramping into production.
A short time later, this
customer again consulted TI
to discuss their specifications
for a 200W dc to dc convert-
er design. Since favorable
results with the 1.5kW PSFB
design had been achieved,
the customer naturally con-sidered using a scaled-down
200W version. The PSFB
would undoubtedly meet their
requirements of high efficien-
cy and reduced cost, but was
it the best choice? The single-
ended forward converter with
active clamp transformer
reset offers many of the same
advantages found in the
PSFB topology, but at re-duced power levels. Where
the PSFB can be designed to
operate at tens or even hun-
dreds of kilowatts, the active
clamp forward is limited, in a
practical sense, to about
400W. Once the performance
and cost trade-offs were pre-
sented, the customer agreed
to proceed with an active
P20 EDN POWER TECHNOLOGY
A S P E C I A L S U P P L E M E N T T O E D N
P A R T F O U R : E M B E D D ED P O W E R
(Scalable Powercontinued on P33)
With Every SpellmanBertan brand High Voltage Supplyyou get something extra inside:The Know How of the High Voltage People.
For more than 50 years, Spellman is the innovator of the High Voltage industry. With ourrecent acquisition of the respected Bertan High Voltage brand, we offer the worlds mostcomprehensive line of generators, rack instruments, modules and Monoblock X-Ray Sources.
APPLICATION KNOW HOW:
Whether your field is X-Ray Analysis, Semiconductor Processing,Security Detection, Medical Imaging, Electron Microscopy, or MassSpectrometry, we make a high voltage supply to meet your needs.
ENGINEERING KNOW HOW:We have the largest engineering team in the business and one of themost innovative design libraries in our industry.
MANUFACTURING KNOW HOW:
We maintain world-class ISO9001 production facilities in the US,Europe and in Mexico.
The High Voltage People of Spellman: responsive, professional and situated globally to supportyour high voltage needs. For more information, call us or visit our website www.spellmanhv.com
475 Wireless Blvd.Hauppauge, NY 11788
tel: +1-631-630-3000fax: +1-631-435-1620
e-mail: [email protected]
www.spellmanhv.com
USA EUROPE JAPAN MEXICO CHINAMONOBLOCK is a registered trademark of Spellman High VoltageElectronics Corp.
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Running OutOf Room?We Suggest
Fewer Chips.Reduce your board size and increaseefficiency with Intersil's multiple outputDC/DC Switching Regulators. Get upto 20A of output current and fourregulated outputs from a single VINranging from 3.3V to 24V.
Datasheet, free samples, and more information available at www.intersil.com/edn
Design has never been so easy, with a variety of
combinations of linears and PWMs, Most devices are
available in thin scale packages to maximize real estate.
Intersil High Performance Analog
Intersil Switching Regulators
Intersil Switching Regulators for precise power delivery.2005 Intersil Americas Inc. All rights reserved. The following are trademarks or services marks owned by Intersil Corporation
or one of its subsidiaries, and may be registered in the USA and/or other countries: Intersil (and design) and i (and design).
Intersil's Family of Multiple Output DC-DC Solutions
4
3
2
# of Outputs
ISL6521
ISL6455
ISL6455A
ISL6537
ISL6532A
ISL6441ISL6443
ISL6227
ISL6440
ISL6539
ISL6530/1
ISL6528
ISL6529
Device
1
1
1
2
1
22
2
2
2
2
1
1
Regulators
PWMs
3
2
2
2 + Ref
2
11
0
0
0
Ref
1
1
Regulators
Linears
5
3.3
5
2.5, 12
5, 12
4.5 to 244.5 to 24
4.5 to 24
4.5 to 24
5 to 15
5
3.3, 5
3.3 to 5, 12
VIN(V)
SOIC-16
QFN-24
QFN-24
QFN-28
QFN-28
QFN-28QFN-28
SSOP-28
QSOP-24
SSOP-28
SOIC-24, QFN-32
SOIC-8
SOIC-14, QFN-16
Package
Int.
FETs
20
0.6
0.6
20
20
610
16
10
8
1
15
15
IOUT(max) (A)
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8/14/2019 EDN 0504 Supplement
22/36P22 EDN POWER TECHNOLOGY NOVEMBER 2005
thesolutionA major TV manufacturer asked Fairchild
Semiconductor, to help them design the power supply
system for a 40 digital TV set. The challenge was to
design a power supply system that was small andhighly efficientboth constraints being dictated by
the appliances thin form factor. The power supply
system had to have efficiency
above 85% in normal opera-
tion and meet the Energy Star
requirement of
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A S P E C I A L S U P P L E M E N T T O E D N
P A R T F O U R : E M B E D D E D P O W E R
(24V/8A, 192W) will power the LCD back light invert-
er block, Output 2 (5V/0.5A) will power the logic
block, Output 3 (5V/2A) will power the tuner block
and Output 4 (12V/3A) will power the audio amplifier
block. This adds up to a
total power of 243W in nor-
mal operation with a stand-
by power of less than 1W.
The strategy we adopted
to meet both normal and
stand-by operation was to
divide the entire system into
two sub-systems, a main
power supply sub-system for
normal operation and an auxil-
iary one for stand-by (Figure 2).
Stand-by Operation
In stand-by mode, the main
power is disconnected from
the ac line. We used a relay
and only the stand-by power
supply built around
Fairchilds FSDM311 SMPS
power switch to power thelogic block. The FSDM311
consumes very little power
thanks to its high-voltage
start-up switch and the
advanced burst mode opera-
tion to reduce switching loss.
Normal Operation
In normal operation, the
devices main power supply
was built around FairchildsFAN4800 PFC/PWM mono-
lithic combo controller IC,
which achieves high effi-
ciency using ZVS (zero volt-
age switch) ASHB (asym-
metric half bridge) topology
and utilizes the FAN7382
for high side MOSFET drive.
The patented Leading-Edge
Modulation (LEM) PFC/TEM
Trailing-Edge Modulation(TEM) PWM synchroniza-
tion method reduces ripple
current in the storage capacitor between the PFC and
PWM sections. This results in higher efficiency and
smaller component size. Thanks to these features,
the measured total efficiency at 85Vac was over 85%,
Sometimes looking for the right power supply can be a hassle.Thats why Norvell has developed Power Supply Solutions. This unique
tool will respond to your specifications quickly by accessing severalmanufactures and providing multiple power solutions. Its just thatsimple. Go to norvell.com/pss and experience Norvells newestway to service your needs. Just plug it in, order it and power up!
power up
The quickest way to find the power you need.
www.norvell.com/pss
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A S P E C I A L S U P P L E M E N T T O E D N
P A R T F O U R : E M B E D D E D P O W E R
including the PFC section, and met the customers
demand.
PFC
The FAN4800 meets the PFC regulations thanks to its
high-performance average current mode PFC control
block. As an added bonus, the devices current fed
gain modulator produced excellent noise immunity.
Conclusion
The diffusion of large-sized flat panel television sets is
adding new dimensions to the challenge of power
management and power conservation. Regulatory
agencies have so far focused on power conservation in
stand-by and are just beginning to tackle regulation of
AC LINE
D5SB60
FAN 4800:
LCD
BacklightPS
24V/8A 12V/3A
5V/60mAFSDM311:
Stand-By PS
FAN5234:
DC-DC
5V/2A Tuner
5V/0.5A Logic
FSCQ0765:
Audio PS
Fig. 2. 40 LCD TV Power Supply System
(PFC/PWM continued on P34)
* Output Power from 1 to 10 Watts* Single Outputs to 1000Vdc* Dual Outputs to +/- 500Vdc* 1000Vdc Isolation* Input Ranges (9-36Vdc, 20-60Vdc, 36-72Vdc)* Low Profile Packages (0.8 x 1.25 x 0.52 & 1 x 2 x 0.4)* Typical Efficiency 82%* Pricing starts at $25/1K
For more information, call American Power DesignPhone 888/894-4446 , Fax 603/894-4291
Email [email protected]
S Series High Voltage DC/DC Converters
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High Power Buck-Boost
97% Efficient Single Inductor Buck-Boost Controller
, LTC and LT are registered trademarks and SwitcherCAD is atrademark of Linear Technology Corporation. All other trade-marks are the property of their respective owners.
www.linear.com
Literature: 1-800-4-LINEAR
Support: 408-432-1900
The LTC3780 is Linears latest addition to our growing family of true buck-boost regulators. This wide input voltage range,high power controller is capable of delivering efficiencies of up to 97% for a 12V, 5A output from an input voltage range of4V to 36V. Its current mode topology and single inductor architecture enable simpler solutions than traditional SEPIC ortransformer-based designs. With up to 400kHz operating frequency, compact, high power density designs are easily achieved.
5
100%
95%
90%
85%
80%
75%
70%10
SEPIC Converter
LTC3780
VIN(V)
Efficiency
(%)
15 20 25 30 35
LTC3780 Efficiency vs SEPIC(VOUT = 12V, ILOAD = 5A)
Info & Online StoreFeatures
VIN Above, Below or Equal to VOUT Single Inductor 4-Switch
Synchronous Operation
Selectable Low CurrentOperating Modes
200kHz to 400kHz ConstantFrequency Operation,Phase-Lockable
VOUT Disconnected from VINDuring Shutdown
24-lead SSOP and5mm x 5mm QFN-32
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Datasheet, eval kit with USB
interface, free samples, and
more information available at
www.intersil.com/edn
ISL6299 Key Features:
Dual-Input charger for single-cell Li-ion/
Polymer Batteries for Cradle and USB
Low Component Count
Integrated Pass Element
Fixed 380mA USB Charge Current
Programmable Cradle Charge Current
Charge Current Thermaguard for
Thermal Protection
28V Maximum Voltage for the Cradle Input
Charge and Adapter Presence Indicators
Less than 0.5A Leakage Current off the
Battery when No Input Power Attached
Programmable end-of-charge current with
latch for Cradle Input
No External Blocking Diode Required
Pb-Free Plus Anneal Available
(RoHS Compliant)
Unshackle YourHandheld DeviceFrom Its CradleIntersils ISL6299 is a fully integrated low-cost Li-ionor Li-polymer battery charger that accepts both USBport and desktop cradle charger.
Intersil High Performance Analog
Intersil Battery Charger ICs
Intersil Switching Regulators for precise power delivery.2005 Intersil Americas Inc. All rights reserved. The following are trademarks or services marks owned by Intersil Corporation
or one of its subsidiaries, and may be registered in the USA and/or other countries: Intersil (and design) and i (and design).
Programmable end of charge optimizes
end-customer applications. High input
voltage tolerance protects the device when
used with low cost unregulated supplies or
in under input transient conditions.
Cradle input. The max input voltage tolerance is 28V. Programmablecharge current up to 1A and programmable end of charge current. Theincluded end of charge latch is the default input source.
USB input. Takes input from USB port or other low voltage supply. Fixedcharge current at typically 380mA. Only charges when cradle source isnot connected.
The ISL6299 is a low component count solution that features
programmable cradle charge current, charge indication, adapter
present indication, and programmable end-of-charge (EOC) current
with latch. All these advanced features, along with Intersils Therma-
guard technology for an added measure of thermal protection, are
delivered in this single chip available in a tiny 3x3 mm DFN package.
ISL6299 System
Fast-charging rates of an AC
adaptor for when you have
access to cradle.
Sync-up and fuel-up directly from your
laptop with convenient USB charger.
28V tolerant cradle with
overvoltage protection.
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8/14/2019 EDN 0504 Supplement
27/36NOVEMBER 2005 EDN POWER TECHNOLOGY P27
A S P E C I A L S U P P L E M E N T T O E D N
P A R T F O U R : E M B E D D E D P O W E R
thesolutionThe concept is illustrated in Figure 2. The isolated
dc/dc Converter is an isolation transformer used to
convert the higher input voltages to a lower interme-
diate bus voltage (IBV), and the efficiency does notappreciably change with the voltage differentials
across the device.
The POLs are not isolated and do not employ a
transformer to convert the IBV to the output voltage,
hence the efficiency of the device varies with the volt-
age differential between the input and the output.
This means that the POL operates more efficiently
with lower voltage differentials across the device.
The printed circuit board (PCB) trace resistances
are constant and the power is a multiple of voltage and
the square of the current (I2R). When delivering power
to a load, it is desirable to raise the distribution voltage
to the highest level feasible so as to lower the current
and minimize the trace voltage drops.
As power requirements in a system
vary, the load currents of each POL, and
thus the total IBV current varies, affect-
ing the PCB trace voltage drops.
At low power requirements the IBV
can be lowered in order to reduce the
voltage drops and increase the efficien-cy of the individual POL converters.
At higher system power require-
ments the IBV can be increased in order to reduce
the PCB current and reduce the trace (I2R) power
losses.
Within a range of varying system power require-
ments, there is an optimum IBV where the efficiency
is maximized.
Analysis calculations, using actual copper cir-
cuit board trace resistances, indicated that even
though the power dissipation in the POLs was higher,at the high required currents, the higher bus voltage
resulted in a slightly better efficiency of 80% for the
12 Volt bus vs. 78% efficiency for the 5 Volt bus.
Which Voltage Bus is Best?8 byLOU PECHI, POWER-ONE, INC.
CASE Study
thechallengeTo meet the design goals of the equipment, the cus-
tomer needed not only to reduce the size of his new
design, but also reduce the material cost while at the
same time increase the functionality of the power con-
version and management functions.
The customer required 8 distinct voltages rangingfrom 0.75 Volts and up to 3.3 Volts at currents rang-
ing from low 3.7 Amp and up to 10 Amp. Besides
sequentially powering each output, in order to assure
proper system operation,
the rate of turn on and
turn off had to be differ-
ent for each output.
To optimize the system
power dissipation the cus-
tomer was faced with the
problem of choosing the
right bus voltage. At low
bus voltages at same over-all power, the current and
the associated I2R dissi-
pation in the circuit board
traces is higher, while at
higher voltages due to the
lower currents the dissipa-
tion is lower. Additionally,
converting higher inputs
to the low outputs at the
point of loads (POLs), the dissipation in the POL itself is
higher. The dissipation in the isolated dc/dc converter
that converts the 48 Volt input to the bus voltage does
not change appreciably due to different isolation trans-former turn ratios, with the output voltage. Thus the
choice of the bus voltage needs to be made based on the
best balance between the circuit board trace and the
POL losses.
CUSTOMERPROFILEA LEADINGDEVELOPER OFNEXT-GENERATIONOPTICAL ULTRA-HIGH-SPEED
TRANSMISSIONTRANSPORTPRODUCTS.
Figure 1. SystemBlock Diagram
Figure 2. Power Dissipation Block Diagram
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8/14/2019 EDN 0504 Supplement
29/36Enter xx at www.edn.com/infoEnter xx at www.edn.com/infoEDN POWER TECHNOLOGY P29
A S P E C I A L S U P P L E M E N T T O E D N
P A R T F O U R : E M B E D D E D P O W E R
Solution Implementation
Simulation of the two intermediate bus voltages con-
firmed the theoretical calculations. The customer
chose the Power-One QBC11ZH-NT isolated con-
verter that met the require-
ments of converting the
wide input worldwide tele-
com bus voltages of 36 to
75Vdc to a 12V bus at 11A.
For the POLs the cus-
tomer had a choice to use
the ZY7007 (7 Amp) and
the ZY7010 (10 Amp) for
the lower currents, and the
ZY7115 (15 Amp) for the
higher output currents.
In order to minimize the
number of different compo-
nents, the customer chose
the ZY7115 intelligent, fullyprogrammable step-down
POL converters, even though
some of the output current
requirements were below the
capabilities of the device.
Besides reducing the num-
ber of different part numbers,
operating way below the
rated output current capabili-
ties of the POLs increased the
overall system reliability.To manage and control
the 8 POLs his choice was
the ZM7108 Digital Power Manager (DPM).
The eight Point of Load Converters (Z-POLs)
were programmed and managed by the eight channel
ZM7108 as shown in Figure 3.
Figure 3. Chosen DPMand Z-POLs
131-38 Sanford Avenue, Flushing, NY 11352 USATel: (718) 461-7000 Fax: (718) 767-1102
Email: [email protected]
www.kepcopower.com
You need to use the right tools to get the jobdone. Kepco provides you with these tools inour broad line of instrumentation and modularpower supplies.
Kepco, Inc., an ISO 9001 company, has beenmaking precision-stabilized power suppliessince 1946. We specialize in analog-controlledfast-programmable d-c products, capable ofproducing 1, 2 or 4- quadrant (bipolar) outputs.Digital control is supported under GPIB(IEEE 488.2), RS232 and VXI, using SCPIand CIIL. VXI plug&play capability is availablefor more than 50 models ranging up to 1200
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SERIES KLP
voltage, current and power-limitedoperating boundaries1200 watts
GPIB, RS 232 & isolated analogcontrol standard. True 1U height - full power operation
with no spacing between units. Wide range a-c input with active PFC.
www.kepcopower.com/klp.htm
SERIES BOP HIGH POWER
d-c bipolar power1KW Source & sink, 4 quadrant operation.
Fast analog programming. Precision stabilization:
0.001% source, 0.002% load. Digital programming. Built-in arbitrary waveform generator.
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SERIES RTW
d-c modular power50-100 watts
Wide range a-c input with active PFC.
Low profile,optional coverfactory installed.
FCC Class B conducted andradiated emissions.
www.kepcopower.com/rtw.htm
POWERTOOLS
RoHSCompliant
-
8/14/2019 EDN 0504 Supplement
30/36Enter xx at www.edn.com/infoEnter xx at www.edn.com/info
The DPM bi-directionally communicates with the 8 Z-
One POLs and with the main system through a standard two
wire I2C Bus.
The DPM, besides communicating with the main sys-tem, can set through a graphical user interface (GUI) I 2C
interface each Z-POL converters parameters such as,
output voltage, sequencing, tracking, protection type and
thresholds, frequency, fault propagation, interleave and
feedback loop compensation. The DPM constantly moni-
tors each Z-POL converters output voltage, current and
temperature, while the Z-POLs monitor and report their indi-
vidual status of, over and under voltage protection (OVP &
UVP), and power good high and low (PGH & PGL). Data,
such as output voltage, output current, and temperature, are
constantly updated and stored in the DPMs shift registerand can be accessed in case of system failure. Such teleme-
try data can also be used to monitor the temperature at each
POL location.
Fault management between the Z-POL converters can
be programmed to act differently when faults occur. If no
fault propagation is required, the protection, depending on
fault severity, shuts down just the faulty Z-POL in a latching
or non-latching mode (hiccup with a 130ms period). Fault
propagation within a group of Z-POLs, besides shutting
down the failed Z-POL, shuts down all the Z-POLs within the
group and assures that the group is synchronously turned
P30 EDN POWER TECHNOLOGY NOVEMBER 2005
A S P E C I A L S U P P L E M E N T T O E D N
P A R T F O U R : E M B E D D E D P O W E R
Figure 5. Turn on Simulation
Figure 6. 50% Load Transient Simulation
(Which Voltage Bus is Best? continued on P34)
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33.5.57.92.12.80
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