ERICSSON POWER MODULES - Mark Allen Group · Ericsson Power Modules has recently introduced a...
Transcript of ERICSSON POWER MODULES - Mark Allen Group · Ericsson Power Modules has recently introduced a...
ERICSSON POWER MODULES
3E – Enhanced performance, Energy Management and increased End-user value with digital DC/DC converters
Trust is a wonderful thing. Your customers trustyou to come up with the goods. And you trustyour suppliers to provide the components thatmake your systems work flawlessly. So let’s talk.Quality and trust are the business that EricssonPower Modules has been in since the beginning.Making the power solutions that make thingswork. Actually, it’s a business that we can’t affordnot to be in. Nor can you. Let's go places together.
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AND THIS IS YOUR SYSTEM
THAT MUST NEVER FAIL
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MAKING SURE THAT
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Ericsson Power Modules has recently introduced a comprehensive set of products that establish an
innovative approach to the goals of end-user value, flexibility and system performance. These new products
contain several unique concepts spanning several disciplines in circuit and system design, all focused on
optimizing performance, flexibility and value for the end-user. Ericsson Power Modules refers to the high-
level end-user benefits of this product approach as “3E”, the 3 Es being:
• Enhanced Performance
• Energy Management
• End-user Value
This brochure describes the initial set of DC/DC converter offerings in this product family, which will be
referred to generically as “3E DC/DC converters”. These converters are intended to be a complement to the
3E Point of Load (POL) regulators described in reference (7).
The next section will describe some of the concepts, terminology and definitions used when working with
the 3E DC/DC converter designs and power system architectures enabled by the new products. This is
followed by a description of the 3E DC/DC converter offerings and then a more detailed treatment of the
benefits to the end-user in the areas of mechanical features, electrical performance, system power and
energy management, and overall value. The last part of this brochure will then expand the discussion of the
3E concept and explore its ramifications for the end-user.
1. Introduction
The internal design of the 3E DC/DC converters uses
digital power control techniques, and some of the op-
tional user implementations of these products can benefit
from utilization of system level digital power and energy
management approaches. While these products can be
successfully applied using the same techniques as with
conventional fully analog converters, it is beneficial for
the customer to become somewhat conversant with the
digital approaches so that he/she can make the optimal
choice for their particular system between conventional
and digital techniques. This section will briefly describe
the distinctions between digital power control and digital
power and energy management. Further information is
available in the cited reference material.
This discussion will assume the usage of a fairly conven-
tional Intermediate Bus Architecture (IBA) such as that
shown in Figure 1, with a board-level Intermediate Bus
Converter (IBC) or DC/DC converter feeding multiple
POL regulators which are located in proximity to the load
circuitry and supply the final operating voltages. The IBC
output voltage, and POL input voltages, will typically be
between 3.3 and 12 Vdc.
Conventional analog DC/DC converters use a Pulse
Width Modulation (PWM) control chip in conjunction
with a multitude of external resistors, capacitors, in-
ductors and active discrete semiconductor devices to
achieve the feedback and control functions needed by
the Board Mounted Power Supply BMPS. The required
time constants are formed with linear analog component
networks. Ericsson Power Modules uses the term “digital
power control” to describe a power converter or regulator
design in which much of the analog control functionality is
replaced with digital circuitry. Typically the digital content
will include the feedback loops, MOSFET gate drive gen-
eration, stability control, and fault detection. The MOS-
FET switches and the main output LC filter are often quite
similar to those in an analog DC/DC converter. The main
point to be made here is that digital power control can be
transparent to the end-user of the BMPS. Two devices,
one implemented digitally and one with analog circuitry,
can be plug-compatible and may even be indistinguish-
able as far as the end-user is concerned. However using
digital techniques internal to a DC/DC converter can
offer significant density and performance advantages to
the end-user as well as drastically increase the DC/DC
converter’s flexibility and configurability.
While digital power control only applies to circuitry
contained within a power supply and is designed and
controlled by the BMPS manufacturer, digital power
management and energy management extends beyond
the physical boundaries of a DC/DC converter or POL
regulator and into the end-use system. This extension
significantly increases the capabilities of the end-use
system, but will also require the power system designer
to participate in the implementation of the digital com-
2. Concepts, Terminology & Definitions
Figure 1 In an Intermediate Bus Architecture (IBA) a board-level Intermediate Bus Converter (IBC) feeds multiple POL regulators which are located in proximity to the load circuitry and supply the final operating voltages.
munications structure. The term “digital power manage-
ment” is used by Ericsson Power Modules to describe a
system in which DC/DC converters and/or POL regula-
tors communicate digitally with each other and/or other
elements in the system for the purposes of monitoring
and controlling the behavior of the power supplies. This
digital communication is typically used for the functions
of power monitoring, fault handling, power sequencing,
and efficiency optimization, and is facilitated by a digi-
tal interface referred to as the power management bus
(PMBus™). While digital power control must operate on
a cycle-by-cycle basis at the power supply’s operating
frequency to control the energy flow, digital power man-
agement usually operates on a slower time scale to react
to changes within the system.
The efficiency of DC/DC converters and POL regula-
tors has always been a key performance criterion. It is
receiving even more attention in recent years as more
emphasis is placed on energy consumption and the
environmental impacts of large scale data processing and
telecom installations. A fortuitous synergy results when
digital power control and digital power management are
combined. Digital power control allows for “on-the-fly”
reconfiguration of operating parameters within a power
supply as a function of system operating conditions.
If a digitally controlled DC/DC converter is operated in
a system with digital power management, the system
status can be used to dynamically program the operating
conditions of the power supply. For example, the power
transistor dead-time, which is the off-time between two
power pulses in the synchronous rectification circuitry,
could be varied as a function of the DC/DC converter’s
input and output voltage and output current to optimize
the real time efficiency over a broad variety of operating
conditions.
Similarly, the intermediate bus voltage provided by an
IBC can be dynamically varied to optimize the overall
efficiency of the combination of IBC and POL losses as a
function of the current system operating condition. Erics-
son Power Modules refers to this combined usage of
digital power management and digital power control for
the purpose of optimizing the overall power efficiency of
the end-use equipment as a function of actual operating
conditions as “digital energy management”. Impressive
savings in total energy consumption can be achieved in
this way. In effect, digital energy management replaces
compromise with optimization. Reference (1) describes
these general possibilities in greater depth while refer-
ences (2) and (3) discuss their application to DC/DC
converters.
2. Concepts, Terminology & Definitions
The fi rst 3E DC/DC converter product introduced by
Ericsson Power Modules is the BMR453 series. These
3E DC/DC converters are designed to complement the
3E POL regulators, and provide outstanding levels of
effi ciency, power density, fl exibility and performance. The
BMR453 is an isolated DC/DC converter capable of
400 W or 33 A of output in a quarter brick form fac-
tor. Unlike other quarter brick DC/DC converters, the
BMR453 achieves this power density while providing
tight +/– 2% output voltage regulation over an input volt-
age range of 36 to 75 V at effi ciency levels in excess
of 96%. The output voltage is variable from 8.5 to
13.5 V. The BMR453 is the fi rst DC/DC converter to offer
this combination of performance and power density,
making it a logical choice for high performance systems
operating with 48/60 V battery backup power architec-
tures. The fl exibility of this product will make it attractive
for a wide range of applications, some of which will be
described in this brochure. The BMR453 is shown in
Figure 2.
The BMR453 technical specifi cation should be consulted
for detailed performance data. The product offers an
extensive set of capabilities and features such as:
• PMBus interface
• Confi gurable OVP, OTP, OCP
• Remote sense
• Switching frequency synchronization
• Active current sharing
• Power good
• Voltage tracking
• Extensive power management programmability
• Optional baseplate
• High reliability
• Low parts count
• Start-up into pre-biased output
The importance of the BMR453 introduction can best be
understood by taking a broader view of the DC/DC con-
verter and IBC market. In recent years this market has
been somewhat segmented. Traditional DC/DC convert-
ers were considered “high performance” products with
tight output voltage regulation. The tradeoff for this more
precise regulation was lower power density and lower
effi ciency when compared with IBCs. The IBC eliminated
the output voltage regulation function in order to achieve
better power density, effi ciency and cost than was
available with DC/DC converter products. The BMR453
combines the best attributes of the traditional DC/DC
converter and the IBC along with the benefi ts of digital
power control and digital power/energy management.
This combination results in a product that is superior to
either the IBC or the traditional DC/DC converter.
Figure 3 depicts the genesis of this new product by
comparing its high level specifi cations to those of con-
temporary high performance DC/DC converter and IBC
products.
3. 3E DC/DC ProductOverview
Figure 2 The BMR 453 ¼-brick is offered in both open-frame and baseplated versions. The product can be used with or without the communications interface connector.
The comparisons are done at an output voltage of 12 V
and an input voltage of 48 V. All three converters shown
are packaged in a quarter brick form factor and are ca-
pable of operation over the 36 to 75 V input range. The
PKM4213CPI DC/DC converter has a maximum output
power of 204 W and a 94% typical efficiency at half load.
The PKM4304BPI IBC product has a maximum output
power of 377 W and a 96% typical efficiency at half load.
The BMR453, with an output power of 400 W and a
typical half load efficiency of slightly over 96% is an im-
provement over either former product, as it provides the
same output voltage regulation as the traditional DC/DC
converter. Consequently it represents an ideal product
for usage in either traditional or IBC converter applica-
tions. This significant advance in performance was made
possible by the use of digital techniques for both power
control and power management. The benefits of this ap-
proach to the end-user will be discussed in the following
section.
Figure 3 The BMR453 combines the tight output tolerance of the traditional DC/DC converter and the high power density and efficiency of the IBC along with the benefits of digital power control and power management.
Intermediate Bus Converter PKM 4304B
Digitally controlled BMR453
Fully regulated PKM 4213C
4.1 MECHANICAL FEATURES
The BMR453 DC/DC converters are configured in a stan-
dard quarter brick package and are available both with
and without a baseplate. A communications pin header is
used for connection to the PMBus. For users who elect
to not use the PMBus interface an optional version of the
converter is available without the communications pin
header. While eliminating the opportunity for system level
digital power management, this option will still provide
the benefits of digital power control internal to the DC/DC
converter.
For the 3E BMPS products Ericsson Power Modules took
a fresh look at the interconnection issues and created a
new optimized communications header design. For the
normal DC/DC converter power input and output pins
carrying large amount of current thick low resistance pins
are used. For other interfaces such as remote sensing
and clock/data lines that conduct minimal current an
industry standard connector header is selected. This se-
lection, in addition to reducing the PCB area needed for
interconnection, results in cost savings to the end user.
The low current connector header is widely used in the
industry with high production volumes and low cost. This
selection also eliminates the technical risk of developing
a new pin design. A diagram showing the PCB footprint
dimensioning and pinouts is provided in Figure 4.
4.2 ELECTRICAL PERFORMANCE
This section highlights some of the electrical performance
characteristics of the 3E BMR453 DC/DC converter
product. As will be seen in the next section, these per-
formance parameters can in some cases be enhanced
when using digital power management and digital energy
management at the system level.
Figure 4 The BMR453 combines the standard size and footprint of the ¼-brick form-factor with the addition of a communications interface connector.
4. 3E DC/DC Benefits
Figure 5 shows the typical efficiency characteristics of
the BMR453 as a function of input voltage and output
current. Note that the curve is relatively flat over a wide
range of output current and extends above 96% for out-
put currents from 10 to 25 A with the most common 48 V
input voltage. This is outstanding efficiency performance.
Even though it is a fully regulated DC/DC converter the
efficiency is higher than that of most IBCs without load
regulation. Later in this brochure it will be shown how the
range of high efficiency operation can be extended over
an even broader range of output current.
Since the BMR453 is a fully regulated DC/DC converter
it provides an output voltage within +/– 2% of the initial
set-point over a broad range of input voltage and output
current as shown in Figure 6. This single product pro-
vides the power density and ultra-high efficiency of an
IBC as well as the wide input voltage range and tight load
regulation of a traditional DC/DC converter. This makes it
very attractive for systems that must use a telecom input
voltage with battery backup or both -48V and -60V nomi-
nal input voltages. Its inherent load regulation also allows
the BMR453 to be used as an IBC in systems where the
intermediate bus voltage directly powers devices such
as hard drives which cannot tolerate the wide variation in
bus voltage provided by a normal IBC.
BMR453 DC/DC converters can be directly connected
without external components in an automatic current
sharing configuration even in systems that do not utilize
the PMBus for digital power management purposes. The
current sharing is balanced within a maximum of 10%
Figure 5 Typical efficiency characteristics of the BMR453 as a function of input voltage and output current for both 12 and 9 Vout.
Figure 6 The digital control system in the BMR453 allows for regulation of the output voltage over line and load within +/-2% of the initial set point.
between the converters resulting in a maximum output
power of up to 720 W for two units. Two paralleled units
will have a typical efficiency of over 96% over an output
load range of 25 to 55 A. The ability to share current
under dynamic load conditions is also important.
Figure 7 shows the load sharing characteristics of two
BMR453 DC/DC converters with a 25% to 75% to 25%
output load transition. These converters are directly con-
nected without any ORing diodes and communicate in-
between each other to actively balance the load without
further need for external control supervision.
Most all DC/DC converters are deployed in a system
environment that requires an EMI filter between them and
the input power source so that the appropriate regula-
tory requirements can be met. Often the applicable
conducted emission standard is EN55022 (CISPR22)
class B, which can be difficult and/or expensive to
meet when using DC/DC converters with high levels of
reflected input ripple current. One of the design objec-
tives of the BMR453 was to minimize the input ripple
current so that the size and complexity of the EMI filter
could be minimized: a so-called “filter friendly” approach.
This objective was achieved by providing the capability to
automatically synchronize the operation of paralleled
DC/DC converters. The synchronization is accomplished
with a direct connection between the two convert-
ers so that no system intervention is needed from the
PMBus. The synchronization is done in a “master-slave”
implementation. The slave converter assumes the same
operating frequency as the master, but with a 90 degree
phase shift between them. This phase shift is critical
for the purpose of minimizing the input ripple current of
the combined converters with the interleaved full-bridge
topology. The effect of this approach on the input ripple
current is dramatic as shown in Figure 8. The maximum
ripple current (and most stringent EMI criteria) for this
topology actually occurs at light load, so the testing was
done with no load on the output. The left trace displays
the input current with the synchronization feature dis-
abled and the right trace the input current with the syn-
chronization featured enabled. The significant reduction in
ripple current in the right trace demonstrates the effec-
tiveness of this solution and allows for a very compact
implementation of the conducted EMI filter.
4.3 SYSTEM POWER AND ENERGY MANAGEMENT
4.3.1 Power Management Methodologies
The 3E BMR453 DC/DC converter offerings are extreme-
ly flexible in terms of available management method-
ologies that can be applied during the life cycle of the
end-use application. In order of increasing functionality
they can be summarized as follows:
1. The 3E BMR453 DC/DC converter can be treated the
same as a conventional converter with internal analog
circuitry. The communications connector could just be
ignored, but there is also a product version in which
it has been completely removed. The footprint and
pin-out would be the same as with an analog converter
– input voltage, output voltage, remote control, etc.
The output voltage would be pre-set during manufac-
turing of the BMPS. This would enable the 3E DC/DC
converters to be utilized in systems that have no need
for a more sophisticated control system or that have
Figure 7 BMR453 DC/DC converters can be directly connected without external components in an auto-matic current sharing configuration. The converters will actively balance the load even under steep load changes.
Current share under load changes
– Traces: Output current (12.5 A/div)– 48 V in and 12 V out– 25–75–25% load step
– Time scale: (2 ms/div)– 2.2 mF output capacitance– No ORing on output
Figure 8 The synchronization feature of the BMR453 may be used to attenuate input ripple current, thus facilitating EMI filter design.
Figure 9a The BMR453 DC/DC converter can be treated the same as a conventional converter with internal analog circuitry.
Figure 9b Dedicated converter to converter connections will allow the units to operate in a current sharing configuration and also enable the synchroni-zation feature without the need for a host controller.
Figure 9c Including a host controller in each board-level power system provides by far the most flexible option in terms of obtain-ing maximum benefit and optimization by means of digital power management.
an existing analog-based control implementation. Note
that with this scenario many of the performance benefits
of the 3E products such as increased efficiency, regula-
tion accuracy and power density could still be realized.
2. A dedicated converter to converter connection can be
used without having the PMBus connected to a host
controller during system operation. This converter to
converter bus will allow the units to operate in a current
sharing configuration and also enable the synchroniza-
tion feature. Both of these features will operate with
the same high level of performance as they would in a
system with a complete PMBus based power manage-
ment implementation.
3. The PMBus can be used for digital communication be-
tween the 3E DC/DC converters and a host controller.
This host controller can be a part of each board-level
power system or can be only a temporary connection
to an external host during the product development
and/or manufacturing process. This is by far the most
flexible option in terms of obtaining maximum benefit
and optimization by means of digital power manage-
ment.
A drawing showing these three levels of control imple-
mentation is provided in Figure 9.
AC input ripple current
– 48 V in and 12 V out– 0 A output– 200 mA/div– 5 ms/div
– 150 kHz– 90º interleaving– No filter on input
4.3.2 The PMBus
The PMBus is a bidirectional serial multi-node interface
that utilizes 4 conductors with the following functions:
• Clock (SCL)
• Data (SDA)
• Control (CTRL)
• Alert (SALERT)
The clock and data lines are used for the bidirectional
transfer of data between the host and the controlled
nodes (3E DC/DC converters in this case) in the network.
The alert line is used by the connected converters to gain
the attention of the host controller.
Individual 3E DC/DC converters are identifi ed to the host
controller by means of an assigned address. These ad-
dresses are physically assigned at each converter used in
the system by means of resistive programming. Two pins
in the communications connector are available on each
BMR453 for this purpose, and chip resistors are con-
nected from these pins to Gnd to establish the program-
ming. Eight pre-defi ned discrete values of resistance are
used per pin, providing a total of 62 combinations, which
is more addresses than enough for most systems. Note
that in a typical system some of these addresses would
be used by other power system unites such as POL
regulators, fans and AC/DC rectifi ers.
4.3.3 Usage of the PMBus
While usage of the PMBus is optional, its use will greatly
increase the fl exibility of the end application’s power
system. If BMPS products with PMBus connectivity are
used in the system, it really only requires the bussing of
the 4 conductors previously identifi ed to a host location
in order to take advantage of the benefi ts of digital power
management. One common misconception is that the
host controller must be resident in the end system. While
this is one option, it is not the only one. The following
three scenarios show how the PMBus could be used
during various phases of the end-use system develop-
ment, manufacture and deployment.
1. The PMBus is used during product development and
evaluation. The host controller in this case could be
an external PC connected to the prototype system or
sub-system. This is an extremely convenient and fast
way to experiment with such things as output voltage
settings, power sequencing routines, voltage margin-
ing, fault handling, etc. without the need for hardware
changes in the system. Ericsson Power Modules has
an evaluation kit for the 3E products that contains an
Confi guration Monitoring and Management (CMM)
software and is an excellent way to begin exploring this
type of capability. No host controller is required in the
system itself.
2. The PMBus is used during system manufacturing and
test, and the host controller could be part of the Auto-
mated Test Equipment (ATE). In this scenario the ATE
could automatically confi gure the 3E DC/DC convert-
ers during the system’s manufacturing process. No
host controller is required in the system itself.
3. Scenario with the most capability and fl exibility is to
include the host controller into each board-level power
system. With this confi guration the same host con-
troller can be used for all three phases of a system’s
lifetime – development, manufacture, and fi eld deploy-
ment. Another misconception is that the host control-
ler needs to be powerful and expensive. In reality, its
specifi cations are very modest and in many systems it
can be as simple as a general purpose microcontroller
or some spare gates of an FPGA that may already be
resident in the system.
4.3.4 Examples of Optimization using
Energy Management
This section assumes that the power system designer
has decided to use the PMBus in one of the implementa-
tions described previously, and will give some examples
of how the power system may be optimized by digital
power management techniques. These are only a very
few of the many possibilities. The reader is encouraged to
think about other ways to use these capabilities in his/her
own systems.
Using the PMBus together with a host controller in the
ATE during the manufacturing process provides fast
and reliable setting of power sequencing routines. This
represents a vast improvement in complexity relative to
traditional systems that used analog-based power con-
trollers for this purpose. The BMR453 series is particu-
larly flexible in this regard. It has a “power good” output
signal to indicate when it is in its regulation band and
operating normally, which is useful for event-based power
sequencing. The voltage tracking feature can be used
to create custom user-defined output voltage ramp-up
profiles based on a control voltage ramp. It is also easy
to implement voltage margin testing during manufactur-
ing to verify system operation over the extremes of the
design space. Fault detection and handling can be easily
optimized. The host controller can be programmed to
set customized limits on each of the fault sensors (tem-
perature, voltage and current) not only for absolute limits
but also for “warning” conditions.
The wide output voltage adjustment range of the
BMR453 can be used to optimize overall efficiency and
energy consumption in a system by means of digital
power management via the PMBus. Conventional analog
DC/DC converters and POL regulators are designed for
maximum efficiency under the most commonly expected
system operating conditions. But each system applica-
tion is unique and any individual system will experience
different operating conditions as a function of installed
features and operating mode. Consequently, the output
current of each BMPS will vary with time as will its ef-
ficiency. With the BMR453 the converter’s output voltage
can be dynamically programmed via the PMBus to opti-
mize either its own efficiency or that of the entire power
system. POL regulators, especially at light loads, are
generally most efficient at lower values of input voltage
(DC/DC converter output voltage). The total system
would then be optimized by using a low value of BMR453
output voltage – perhaps in the range of 9 to 10 V.
But during conditions of high output current the system
power demand may require a higher intermediate bus
voltage in order to increase the power output available
from the DC/DC converter. In this scenario, the con-
verter’s output voltage could be automatically increased
to 12 V or above by sensing the system current demand
and programming the BMR453 via the PMBus. The host
controller, knowing the efficiency curves of the POL regul-
ators and the DC/DC converter, can select the optimal
intermediate bus voltage to maximize the total system
efficiency. This technique can be very useful for system
energy management and can have significant impact on
the cumulative energy usage and power utility costs.
Figure 10 shows the combined efficiency of two paral-
leled BMR453 DC/DC converters as well as the efficiency
curve of a single unit. As noted earlier, the efficiency curve
of the paralleled units is exceptionally broad, exceeding
96% from 25 to 55 A. Note that at output current values
of less than 25 A the single DC/DC converter will be
more efficient than a paralleled pair. For systems in which
there is a very wide range of current demand combined
with a high priority on operating efficiency, digital power
management can be used for efficiency optimization.
The host power controller can automatically switch the
DC/DC converter function from a current shared paral-
leled connection to a single converter when the system
current requirements are low. This communication would
be done via the PMBus. The negotiated switching point
would need to contain a fair amount of “overlap” or
hysteresis so that a single converter would not be oper-
ated near its maximum current rating to avoid overcur-
rent conditions. With this type of automated converter
changeover capability the composite efficiency curve
of the BMR453 is truly impressive, with 96% efficiency
achieved from10 A to 55 A. The efficiency is above 90%
even at loads down to 2.5 A. This approach results in a
significant savings in power losses, since at light system
loads the switching losses of a single converter will be
about half those of two paralleled converters.
Practical implementation of the above automated con-
verter selection capability will require seamless switchover
without disruption of the system intermediate bus voltage
load or generation of any fault conditions. Ericsson Power
Modules has conducted some testing to assess the
performance of the automated reconfiguration, with the
results shown in Figure 11. The oscilloscope trace on
the left shows the effect on the output voltage of switch-
ing from a paralleled converter connection to an individual
converter. The test was done at an initial output load cur-
rent of 20 A, so the operational converter sees an output
current transition from 10 A to 20 A. This current change
results in a slight depression in the output voltage but it
stays within the +/- 2% regulation band.
A more demanding condition occurs when switching
from one converter to a paralleled connection. Synchro-
nous rectification is used in the converters to maximize
efficiency with the output rectification implemented with
MOSFETs, which can conduct current in either direc-
tion. This can create difficulties when starting up into a
pre-biased load, which is exactly the scenario presented
with the startup of the second converter in the paral-
leled configuration. Without proper management of the
startup, the converter could be overstressed by a reverse
current and there could be a significant dip in the output
Figure 10 Active utilization of parallel versus single DC/DC converter operation is a powerful tool that reduces energy consumption by optimization of the efficiency over the full load range.
voltage. ORing diodes could be used as a solution, but
were rejected due to their negative impact on efficiency
and packaging density. Instead, the ORing function is
implemented with intelligent control of the output transis-
tors. This approach would normally require the addition
of a specialized controller IC, but with the digital control
implementation of these converters the startup control
is handled by the existing self-contained microcontroller
without the need for any additional components. The ef-
fectiveness of this approach is demonstrated in the right
oscilloscope trace in Figure 11. The slight dip in the out-
put voltage is due to a very small reversed current during
the start-up going into the second converter, but this
current is at a safe level for the BMR453 product. These
results are very encouraging and represent a meaningful
advancement in the ability to achieve high efficiency over
a very wide range of output current.
Another possible extension of this capability, which could
be useful in some high availability systems, would be to
automatically disable a failed paralleled converter to per-
mit the system to continue operation at a reduced power
level in “limp along” fashion until a repair action could be
accomplished. These examples show just how powerful
the concept of digital power management can be. You
no longer need to accept compromise – you can have
optimization!
Figure 11 Enabling and disabling a second DC/DC converter during current share operation puts tough requirements on dynamic load performance and the ability to start against a pre-biased load.
Current share and pre-biased operation
– Top trace: Output voltage (500 mV/div)– Bottom traces: Output current (5 A/div)– 48 V in and 12 V out– 1 x 20 A or 2 x 10 A output
– Time scale: (1 ms/div)– 2.2 mF output capacitance– No ORing on output
4.4 END-USER VALUE
This brochure has so far concentrated on how the 3E
BMR453 DC/DC converters can provide measurable
benefits to the user in terms of the design, manufactur-
ing and utilization phases of the product lifecycle. These
benefits have been mostly technical in nature, relating
to electrical and mechanical performance. This section
we will explore other benefits of the 3E concept that are
perhaps secondary in nature but still are quite important
to most all designers of contemporary power systems
and create value for the end-user.
The most striking change that is seen when comparing
the BMR453 to a more traditional converter design is the
significant decrease in the number of components. In
addition to the resultant power density enhancements,
this reduced parts count has another significant benefit –
higher reliability. Since the techniques discussed here will
allow for optimization of system operating efficiency, the
average operating temperature of the 3E DC/DC convert-
ers and other system components can be lower. Fewer
parts operating at lower temperatures equates to lower
failure rates and higher system MTBF. This in turn leads
to reduced system maintenance and down time and
most importantly it leads to fewer site visits and lower
total cost of ownership, which means higher customer
satisfaction.
The wide programmable output voltage range of the 3E
DC/DC converters in conjunction with their ability to be
easily paralleled makes them very flexible in terms of the
types of systems and applications that they can service.
A single part number converter can find widespread ap-
plication within a system and across a broad spectrum
of systems at different power levels. Purchasing volume
can then be concentrated on a few part types for maxi-
mal cost savings while logistics management costs are
minimized.
Because of the extreme flexibility of these 3E products
and the programmable nature of the digital power man-
agement concept, Ericsson Power Modules has realized
the need to take a fresh look at the quality assurance and
design/manufacturing verification processes that support
them. In addition to the traditional quality assurance
provisions of a hardware manufacturing process, strin-
gent controls have been instituted on the software and
firmware elements associated with this new manufactur-
ing environment. Ericsson Power Modules’ approach
to these important parts of this product introduction is
discussed in reference (4). The net result is that usage
of these 3E DC/DC converters will provide the user with
pre-validated products. Compared with custom designed
converter solutions, usage of the 3E DC/DC convert-
ers will result in substantially reduced technical risk and
enhanced time-to-market.
The digital power management concept can be a power-
ful tool. While saving a few milliwatts in one small subas-
sembly may not seem terribly important, the cumulative
power savings in a system of even moderate size can
add up quickly. When several of these systems are oper-
ated many hours a day, the resultant energy savings is
substantial. Building heat load and air conditioning costs
go down. The electrical utility bill goes down. Fewer
natural resources are consumed for power generation
purposes. Everyone wins.
As digital power/energy management becomes more
commonplace it will become an enabling technology, with
ramifications beyond the specific system it is installed in.
It can easily become a powerful tool for the purposes of
data collection and analysis. The result will be increased
knowledge of reliability and failure root cause analysis
that will be invaluable in the design of next-generation
systems.
The above examples are a few ways in which the 3E
DC/DC converters can enhance the value of your system
and the value of the design experience when using them.
User value is, after all, one of the key elements of the 3E
concept.
The preceding pages have hopefully conveyed much of
the fl avor of the 3E concept as applied to these new
DC/DC converters and what it delivers to the end-user.
It has been shown that each of the three Es provides
important benefi ts – many of them new or best-of-breed
for the power conversion industry:
The list above is already a long one, and could be added
to. The reader has probably already thought of other ad-
vantages in their end-use application that 3E can provide.
To defi ne 3E more succinctly, it is about fl exibility – more
importantly, user-defi ned fl exibility. It is about optimization
– namely, user-defi ned optimization. Past products have
been based on some degree of compromise. Much of
this compromise is no longer required.
3E = Maximal Confi gurability with Minimal Compromise
5. 3E – Flexibility and Optimization without Compromise
Enhanced Performance
• Signifi cantly higher power and current density than
other fully regulated converters
• Industry-leading effi ciency
• Sophisticated automatic current sharing when
paralleled
• Automatic synchronization for superior
EMI performance
• Excellent feature set for “stand alone” operation
• Many levels of possible power management
solutions
• Flexible fault detection and error handling
Energy management
• Simple low cost PMBus
• Powerful system development tools
• Major advantages during manufacturing and test
• Unparalleled fl exibility during fi eld deployment
• Adaptable systems possible
• Optimization of effi ciency to actual application
• Reduced power dissipation
• Reduced energy consumption
• Reduced utility costs and environmental impact
End-User value
• Reduced number of DC/DC converters to stock
• Enhanced reliability
• Improved system MTBF
• Increased customer satisfaction
• Backed by comprehensive pre-validation
• Reduced technical risk
• Reduced time-to-market
• Enabling technology for data collection and
analysis
This brochure has presented several ways in which the
new Ericsson Power Modules 3E DC/DC converters can
be used to add value to your system while achieving
state-of-the-art performance. Many of these advantages
can be achieved without a commitment to utilize a digital
power management bus in the end application system.
For users who adopt that approach, application of the 3E
DC/DC converters will be quite similar to using conven-
tional analog converters, and the design and testing
process will seem very familiar.
Many users will elect to take advantage of the increased
functionality, flexibility and opportunity for system optimi-
zation that the PMBus offers by using it as an interface
during system development, manufacturing testing or in
the field environment. For some of these users, this will
represent their first power system design using digital
power management techniques. One of Ericsson Power
Modules’ goals is to make the transition from analog to
digital power management systems as convenient as
possible for the end-user by supporting the new products
with a wide variety of applications assistance. In addition
to the references cited earlier in the brochure, references
(5) and (6) are recommended as a source of more gen-
eralized information about digital approaches to power
conversion design.
These 3E DC/DC converters were designed to comple-
ment the 3E POL regulator products. Ericsson Power
Modules is the first to offer a complete range of isolated
DC/DC converters and non-isolated POL regulators using
the PMBus for digital power management capabilities.
To give our customers an opportunity to easily experience
the benefits to be derived from digital power manage-
ment, an evaluation kit that can be used as a develop-
ment platform for the 3E products is introduced in
parallel with the products. This evaluation kit, shown in
Figure 12, consists of a demonstration board with
provision for hosting two BMR453 3E DC/DC convert-
ers, up to 6 pcs of 3E POL regulators, USB cable, CMM
software on CD, device drivers, sample configuration files
and complete documentation. Using this evaluation kit in
conjunction with a PC and commonly available basic lab
equipment will allow the prospective user to conveniently
experiment with the digital development environment.
This evaluation kit is highly recommended as a first step
for customers that may be considering exploring usage
of the Ericsson Power Modules 3E products or designing
a power system configured with a PMBus.
The new Ericsson Power Modules 3E DC/DC convert-
ers will eliminate many of the compromises inherent in
current designs and create exciting opportunities for
power system designers in terms of system performance,
flexibility, configurability, optimization and end-user value.
Furthermore, system design using these products should
be a fun and rewarding experience!
6. Summary
Figure 12 The 3E evaluation kit consists of a demonstration board with provision for hosting BMR453 3E DC/DC converters, 3E POL regula-tors, USB cable and CMM software on a CD together with complete documentation.
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All referenced papers can be found at Ericsson Power Modules’ web site:
http://www.ericsson.com/powermodules
1. Digital Power Forum 2007 – Intelligent Energy Management for Improved Effi ciency
2. APEC 2007 – Implications of Digital Control and Management for a High Performance Isolated DC/DC
3. Digital Power Europe 2007 – Digital Control in a MicroTCA Power System
4. Digital Power Forum 2007 – Qualifi cation and Verifi cation Considerations for Digital Power Supplies
5. Digital Power Forum 2007 - From Digital Confusion to Digital Conversion
6. Digital Power – Technical Brief
7. EN/LZT 146 246 – 3E – Enhanced performance, Energy management and increased End-user value with digital
POL regulators
ATEAutomated Test Equipment
BMPSBoard Mounted Power Supply
CDCompact Disk
CMMConfi guration Monitoring and Management
EMIElectromagnetic Interference
FPGAField Programmable Gate Array
FRUField Replaceable Unit
IBAIntermediate Bus Architecture
IBCIntermediate Bus Converter
ICIntegrated Circuit
MicroTCA™Micro Telecommunications Computing Architecture
MOSFETMetal Oxide Semiconductor Field Effect Transistor
MTBFMean Time Between Failure
PCPersonal Computer
PCBPrinted Circuit Board
PMBus™Power Management Bus POLPoint of Load
PWMPulse Width Modulation
3EEnhanced Performance, Energy Management, End-user Value
7. Glossary
8. References
Ericsson is shaping the future of Mobile andBroadband Internet communications through its continuous technology leadership.
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Ericsson Power Modules is a supplier of world-class DC/DC power modules for distributed power architectures. With its global design, development, manufacturing and sales network Ericsson Power Modules is a leading supplier of power solutions to meet the customer demand for high quality and performance.
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