power developer: march 2016
DESCRIPTION
High-voltage Batteries Provide Unprecedented Flexibility for Cutting-edge ApplicationsTRANSCRIPT
March 2016
High-voltage Batteries Provide Unprecedented Flexibility for Cutting-edge ApplicationsInterview with Allen Chen — Texas Instruments
New Wireless Charging Methods
Rethinking Server Power Architecture
EEWeb
Power Developer CONTENTS
TECH SERIES
DC/DC Book of KnowledgeChapter 7: Reliability
PRODUCT WATCH
IDT ZSSC1956 Automotive Battery Sensor
TECH REPORT
Wireless Charging Moves Beyond Induction
Power Density Versus Architecture: What You Need to Know
Rethinking Server Power Architecture in a Post-Silicon World
INDUSTRY INTERVIEW
A Sea-Change in Battery Management TechnologyInterview with Allen Chen of Texas Instruments
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KNOWLEDGE
By Steve Roberts Technical Director for RECOM
DC/DC
Chapter 7
Book of
TECH SERIES
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RECOM´s DC/DC Book of Knowledge is a detailed
introduction to the various DC/DC converter
topologies, feedback loops (analogue and digital),
test and measurement, protection, filtering,
safety, reliability, constant current drivers and
DC/DC applications. The level is necessarily
technical, but readable for engineers,
designers and students.
Reliability
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Reliability PredictionSince the advent of electronics, it has been vital for the user to know how long such devices will work properly. Since no one is able to predict the future, statistical methods to predict the reliability of components, assemblies, or devices have been developed.
One of the earliest systematic approaches to electronic component and assembly reliability was the US Army’s “Military Handbook—Reliability Prediction of Electronic Equipment,” commonly known as MIL-HDBK-217, which consists mainly of a large database of the measured failure rates of various components based on the empirical analysis of a large number of field failures of electrical, electronic and electro-mechanical components carried out by the University of Maryland.
The handbook was continuously updated and improved until 1995, by which the final version was called MIL-HDBK 217 Revision F, Notice 2. While this work is no longer updated, the data and methods are still one the most used today.
The handbook contains two methods of reliability prediction, Part Stress Analysis (PSA) and Parts Count Analysis (PCA). The PSA method requires a greater amount of detailed information and is usually more applicable to the later design phase, when measured data and preliminary results can be inserted into the reliability
models, while the PCS method requires only minimal information such as part quantities, quality level and application environment. The biggest advantage of MIL HDBK 217 methodology is that the PCA method will give a reliability prediction based only on the bill of materials (BOM) and the anticipated use, thus a reliability figure can be given for a product that has not even been built yet:
Where:
Number of Parts (per component type)
Failure Rate of Each Part (base value taken from the database)
Environmental Stress Factor (application-specific)
Hybrid Function Stress (addition stress caused by component interaction)
Screening Level Factor (standard part tolerances or pre-screened)
Maturity Factor (well-known and tested design or new approach)
The calculation will give a figure for each component used. The total reliability can then be found by adding up all of the individual results:
Equation 7.1. Calculation of Failure Rate
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Failure rates are defined either as the time interval between two failures, in hours, Mean Time Between Failures (MTBF) or as the time interval to the first failure—Mean Time To Failure (MTTF). The standard failure rate behavior is described by the widely known “bathtub curve.” Figure 7.1 shows the shape of the curve. The shape of the curve is approximately the same for all components and systems—only the elongation of the time axis is different. It is divided into three main areas: Infant Mortality (I), Useful Life (II) and End of Life (III). MTTF includes regions I and II, while MTBF includes only Region II.
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The calculation will give a figure for each component used. The total reliability can then befound by adding up all of the individual results:
Table 7.1: Example of an MTBF calculation by parts count for a simple DC/DC converter.
Failure rates are defined either as the time interval between two failures - in hours - MeanTime Between Failures ( MTBF) or as the time interval to the first failure - Mean Time ToFailure (MTTF). The standard failure rate behaviour is described by the widely known"bathtub curve". Figure 7.1 shows the shape of the curve. The shape of the curve isapproximately the same for all components and systems - only the elongation of the timeaxis is different. It is divided into three main areas: Infant Mortality (I), Useful Life (II) andEnd of Life (III). MTTF includes regions I and II, while MTBF includes only Region II.
Fig. 7.1: Bathtub Failure rate curve
Section I describes the area of early failures, which is usually caused by latent materialdefects or manufacturing faults which happen not to show up in the final production testingbefore the product is shipped. The infant mortality failure is usually of relatively shortduration- even for complex systems there are rarely early failures past 200 hours of use; inthe case of DC/DC converters, most early failures will occur within the first 24 hours ofoperation. This may sound a short period of time for a converter with a guaranteed 3 yearlifetime, but for a DC/DC converter running at 100kHz, the switching transistors andtransformer will have already been exercised more than 140 million times in the first day ofoperation and any failure due to component defects are likely to have already occurred.
No. Parts Q’ty πP Failure rate[10-6/h] TAMB = 25°C
πP Failure rate[10-6/h] TAMB = 85°C
1 Transistor 2 0.0203 0.06092 Diodes 2 0.1089 0.54433 Resistor 3 0.0370 0.17164 Capacitors 5 0.1699 1.70005 Transformers 1 0.2256 1.92006 PCB, PIN 2 0.0092 0.0092
πP Total Failure rate 10-6/H 0.5708 4.4060MTBF Hours (MIL-HDBK-217F) 1.751.927 226.963
ConditionInput Nominal Input Nominal Input
Output Full Load Full Load
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Table 7.1. Example of an MTBF calculation by parts count for a simple DC/DC converter
Figure 7.1. Bathtub Failure Rate Curve
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The calculation will give a figure for each component used. The total reliability can then befound by adding up all of the individual results:
Table 7.1: Example of an MTBF calculation by parts count for a simple DC/DC converter.
Failure rates are defined either as the time interval between two failures - in hours - MeanTime Between Failures ( MTBF) or as the time interval to the first failure - Mean Time ToFailure (MTTF). The standard failure rate behaviour is described by the widely known"bathtub curve". Figure 7.1 shows the shape of the curve. The shape of the curve isapproximately the same for all components and systems - only the elongation of the timeaxis is different. It is divided into three main areas: Infant Mortality (I), Useful Life (II) andEnd of Life (III). MTTF includes regions I and II, while MTBF includes only Region II.
Fig. 7.1: Bathtub Failure rate curve
Section I describes the area of early failures, which is usually caused by latent materialdefects or manufacturing faults which happen not to show up in the final production testingbefore the product is shipped. The infant mortality failure is usually of relatively shortduration- even for complex systems there are rarely early failures past 200 hours of use; inthe case of DC/DC converters, most early failures will occur within the first 24 hours ofoperation. This may sound a short period of time for a converter with a guaranteed 3 yearlifetime, but for a DC/DC converter running at 100kHz, the switching transistors andtransformer will have already been exercised more than 140 million times in the first day ofoperation and any failure due to component defects are likely to have already occurred.
No. Parts Q’ty πP Failure rate[10-6/h] TAMB = 25°C
πP Failure rate[10-6/h] TAMB = 85°C
1 Transistor 2 0.0203 0.06092 Diodes 2 0.1089 0.54433 Resistor 3 0.0370 0.17164 Capacitors 5 0.1699 1.70005 Transformers 1 0.2256 1.92006 PCB, PIN 2 0.0092 0.0092
πP Total Failure rate 10-6/H 0.5708 4.4060MTBF Hours (MIL-HDBK-217F) 1.751.927 226.963
ConditionInput Nominal Input Nominal Input
Output Full Load Full Load
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Section I describes the area of early failures, which is usually caused by latent material defects or manufacturing faults which happen not to show up in the final production testing before the product is shipped. The infant mortality failure is usually of relatively short duration—even for complex systems there are rarely early failures past 200 hours of use. In the case of DC/DC converters, most early failures will occur within the first 24 hours of operation. This may sound a short period of time for a converter with a guaranteed 3 year lifetime, but for a DC/DC converter running at 100kHz, the switching transistors and transformer will have already been exercised more than 140 million times in the first day of operation and any failure due to component defects are likely to have already occurred.
Since thermal stress is one of the accelerating elements for failure rates, the transition time (T1) from early failure into useful life can be considerably shortened via a burn-in process in a temperature cabinet (Fig. 7.2). If the converters are stressed by running them at full load at elevated temperatures, a burn-in time of around 4 hours is sufficient to detect almost all of the early failures. If early failures still occur in the final application, then the burn-in time can be increased. For high reliability applications such as railways, a burn-in time of 24 hours is more common.
During the useful life, characterized by region II, the failure rate is consistent and stable at a low level. The second transition time (T2) from useful life into end of life is influenced by many factures such as quality of the design and components used, the manufacturing quality of the assembly and the environmental stresses of the application. Region III represents the end of the product life cycle during which performance reduction due to wear-and-tear; chemical degradation of the materials used and sudden failures can be expected.
As most DC/DC manufacturers use a burn-in process to detect the majority of early failures, MTBF figures are more commonly used in the datasheets.
Fig. 7.2. DC/DC converters being tested in a burn-in chamber (TAMB = 40°C)
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Since thermal stress is one of the accelerating elements for failure rates, the transitiontime (T1) from early failure into useful life can be considerably shortened via a burn-inprocess in a temperature cabinet (Fig. 7.2). If the converters are stressed by runningthem at full load at elevated temperatures, a burn-in time of around 4 hours is sufficientto detect almost all of the early failures. If early failures still occur in the final application,then the burn-in time can be increased. For high reliability applications such as railways,a burn-in time of 24 hours is more common.
Fig. 7.2: DC/DC converters being tested in a burn-in chamber (TAMB = 40°C)
During the useful life, characterized by region II, the failure rate is consistent and stableat a low level. The second transition time (T2) from useful life into end of life is influencedby many factures such as quality of the design and components used, the manufacturingquality of the assembly and the environmental stresses of the application. Region IIIrepresents the end of the product life cycle during which performance reduction due towear-and-tear, chemical degradation of the materials used and sudden failures can beexpected.
As most DC/DC manufacturers use a burn-in process to detect the majority of earlyfailures, MTBF figures are more commonly used in the datasheets.
Some manufacturers prefer to use the reciprocal of the MTBF failure rate, based on 109hour, called Failures In Time (FIT):
109
FIT =MTBF
Equation 7.2: Relationship of FIT to MTBF
TECH SERIES
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Some manufacturers prefer to use the reciprocal of the MTBF failure rate, based on 109 hours, called Failures In Time (FIT):
Equation 7.2. Relationship of FIT to MTBF
Environmental Stress FactorsMIL-HDBK-217 contains reliability models based on common military applications. The kind of application in which a DC/DC converter is going to be used has a strong influence on its reliability. For example, if the converter is going to be fitted into a ship, then the corrosive effects of the salty air will reduce its lifetime even if it is used in a dry area.
Table 7.2. Application Classes According to MIL-HDBK-217
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7.2 Environmental Stress FactorsMIL-HDBK-217 contains reliability models based on common military applications. Thekind of application in which a DC/DC converter is going to be used has a strong influenceon its reliability. For example, if the converter is going to be fitted into a ship, then thecorrosive effects of the salty air will reduce its lifetime even if it is used in a dry area.
Environ- πE MIL-HDBK-271F Commercial Interpretationment Symbol Description or ExamplesGround GB Non-mobile, temperature and Laboratory equipment, testBenign humidity controlled environments instruments, desktop PC's, readily accessible to maintenance static telecomsGround GM Equipment installed in wheeled or In-vehicle instrumentation,Mobile tracked vehicles and equipment mobile radio and telecoms, manually transported portable PC'sNaval NS Sheltered or below deck Navigation, radio equipmentSheltered equipment on surface ships or and instrumentation below submarines deckAircraft AIC Typical conditions in cargo Pressurised cabin compart-Inhabited compartments which can be ments and cockpits, in flightCargo occupied by aircrew entertainment and non-safety critical applicationsSpace SF Earth orbital. Vehicle in neither Orbital communications satel-Flight powered flight nor in atmospheric lite, equipment only operated re-entry once in-situMissile ML Severe conditions relating Severe vibrational shock and Launch to missile launch very high accelerating forces, satellite launch conditions
Table 7.2: Application Classes according to MIL-HDBK-217
If the final application is known, then a correction factor for the MTBF calculation can bemade based on Ground Benign (GB) as the reference environmental stress with a factorof 1:
Table 7.3: MTBF Correction Factors according to Environment
For example, a DC/DC converter with a MTBF figure of 1 million hours according to thedatasheet (based on GB conditions) would need to be “derated” to around 610 khoursif used in portable equipment to take into account the additional environmental stressesdue to knocks, bumps, sudden temperature changes, etc. associated with hand heldequipment.
One of the perhaps surprising results of the MIL-HDBK-217 analysis is that space flightis as a benign an environment as ground based. Aboard a satellite or spaceship, theenvironmental conditions are carefully controlled and there is no vibration or airbornepollution, so electronic equipment has a theoretically very long life. In practice, however,cosmic rays can punch holes through semiconductor substrates and cause failures.
Environment πE πE
Divisor Symbol ValueGround Benign GB 0.5 1.00Ground Mobile GM 4.0 1.64Naval Sheltered GNS 4.0 1.64Aircraft Inhabited Cargo AIC 4.0 1.64Space Flight SF 0.5 1.00Missile Launch ML 12.0 3.09
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If the final application is known, then a correction factor for the MTBF calculation can be made based on Ground Benign (GB) as the reference environmental stress with a factor of 1:
Table 7.3. MTBF Correction Factors According to Environment
For example, a DC/DC converter with a MTBF figure of 1 million hours according to the datasheet (based on GB conditions) would need to be “derated” to around 610 khours if used in portable equipment to take into account the additional environmental stresses due to knocks, bumps, sudden temperature changes, etc. associated with hand held equipment.
One of the perhaps surprising results of the MIL-HDBK-217 analysis is that space flight is as a benign an environment as ground based. Aboard a satellite or spaceship, the environmental conditions are carefully controlled and there is no vibration or airborne pollution, so electronic equipment has a theoretically very long life. In practice, however, cosmic rays can punch holes through semiconductor substrates and cause failures.
It is possible to make DC/DC converters with “rad-hard” components with added protection from high-energy radiation, but it is often more reliable to use a simpler circuit without any ICs. A FET can withstand considerable damage from exposure to cosmic rays because the substrate surface is relatively large and tolerant of point defects. Thus a simple push-pull DC/DC converter using only discrete components is often suitable for space applications.
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7.2 Environmental Stress FactorsMIL-HDBK-217 contains reliability models based on common military applications. Thekind of application in which a DC/DC converter is going to be used has a strong influenceon its reliability. For example, if the converter is going to be fitted into a ship, then thecorrosive effects of the salty air will reduce its lifetime even if it is used in a dry area.
Environ- πE MIL-HDBK-271F Commercial Interpretationment Symbol Description or ExamplesGround GB Non-mobile, temperature and Laboratory equipment, testBenign humidity controlled environments instruments, desktop PC's, readily accessible to maintenance static telecomsGround GM Equipment installed in wheeled or In-vehicle instrumentation,Mobile tracked vehicles and equipment mobile radio and telecoms, manually transported portable PC'sNaval NS Sheltered or below deck Navigation, radio equipmentSheltered equipment on surface ships or and instrumentation below submarines deckAircraft AIC Typical conditions in cargo Pressurised cabin compart-Inhabited compartments which can be ments and cockpits, in flightCargo occupied by aircrew entertainment and non-safety critical applicationsSpace SF Earth orbital. Vehicle in neither Orbital communications satel-Flight powered flight nor in atmospheric lite, equipment only operated re-entry once in-situMissile ML Severe conditions relating Severe vibrational shock and Launch to missile launch very high accelerating forces, satellite launch conditions
Table 7.2: Application Classes according to MIL-HDBK-217
If the final application is known, then a correction factor for the MTBF calculation can bemade based on Ground Benign (GB) as the reference environmental stress with a factorof 1:
Table 7.3: MTBF Correction Factors according to Environment
For example, a DC/DC converter with a MTBF figure of 1 million hours according to thedatasheet (based on GB conditions) would need to be “derated” to around 610 khoursif used in portable equipment to take into account the additional environmental stressesdue to knocks, bumps, sudden temperature changes, etc. associated with hand heldequipment.
One of the perhaps surprising results of the MIL-HDBK-217 analysis is that space flightis as a benign an environment as ground based. Aboard a satellite or spaceship, theenvironmental conditions are carefully controlled and there is no vibration or airbornepollution, so electronic equipment has a theoretically very long life. In practice, however,cosmic rays can punch holes through semiconductor substrates and cause failures.
Environment πE πE
Divisor Symbol ValueGround Benign GB 0.5 1.00Ground Mobile GM 4.0 1.64Naval Sheltered GNS 4.0 1.64Aircraft Inhabited Cargo AIC 4.0 1.64Space Flight SF 0.5 1.00Missile Launch ML 12.0 3.09
TECH SERIES
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Using MTBF FiguresMTBF figures cause a great deal of confusion because they are often misunderstood and sometimes deliberately misrepresented by unscrupulous manufacturers. An MTBF figure of 1 million hours does not mean that the product has a lifetime of:
MTBF is simply defined as the inverse of the actual failure rate. So if one DC/DC converter out of 100 fails after 10,000 hours of service:
Alternatively, if the failure rate in the field should be less than 1% per year for a certain installed quantity, then the required MTBF rating of the power supplies should be:
When correctly used, MTBF figures can help accurately determine the maintenance overhead in field conditions, but the MTBF values in thousands or millions of hours causes confusion for those not familiar with them. If we take the first example given above; the converters have an MTBF value of one million hours (equivalent to 114 years) but a single converter failed after only 13 months use. Perhaps a more familiar example may help explain this apparent “miscalculation”: the human lifetime. The average “failure rate” of a 25 year old human is 0.1% i.e., we can expect one 25 year old in a thousand to die. Doing the calculation gives a human MTBF of 800 years! The reason that MTBF figures are so high (and so variable) is that the failure rate in the flat middle section of Useful Life is very, very low. Multiplied over a long time period, this means that tiny changes in the failure rate delta (rate of change of failure rate with time) causes large changes in the calculated MTBF. This also explains why we all don’t live to be 800 years old. At 25, most people are at their healthiest and the primary cause of death is accidents. If we did not age or suffer from diseases, we
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would all live to be 800 years old if the only cause of death was accidental. On the other hand, if a different age was chosen, say 45 years, then a very different human MTBF figure would arise, because we humans start to wear out at a relatively early age.
As the failure rate during the final End-of-Life phase follows an exponential law, reliability can be worked out from MTBF using the following formula:
Equation 7.3. Relationship of Reliability to MTBF
If the time (T) equals the MTBF, then the equation reduces to e1 or 37%. This can be interpreted as meaning that at T = MTBF, only 37% of the converters will still be working or, alternatively, that there is only a 37% confidence that all converters will be still working at T = MTBF.
So far, Chapter 7 of the DC/DC Book of Knowledge has covered various methods for reliability prediction in components, assemblies, and devices. The chapter goes on to cover the process of designing with reliability in mind as well as PCB layout considerations to improve overall reliability. Click here to read the chapter in its entirety.
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Power Developer
IDT’sZSSC1956Automotive Battery Sensor
For today’s EEWeb Tech Lab, we will be reviewing IDT’s ZSSC1956, their automotive intelligent battery sensor, and a battery monitor for lead acid batteries. This intelligent sensor comes with an embedded microcontroller for greatest flexibility.
PRODUCT WATCH
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The device integrates multiple ECU
functions into a single package: a high
voltage circuit, sigma delta ADCs, analog
input stage, digital filtering, and a LIN
transceiver. An ARM M0 processor with
96kB flash memory is embedded with
access to all sensor peripherals, ready
for your firmware code. With the ADCs,
this IC can measure lead-acid battery
voltage and current at a rate of 1kHz or
more and resolution of up to 18-bits with
no missing codes while concurrently
measuring temperature. Simultaneous
measurement of voltage and current
allows for inner resistance calculations
often used for battery state of health
estimation. Using a shunt, this device
is capable of measuring charging and
discharging battery current with a
huge dynamic range from milliamps
KEY BENEFITS
» High-precision 24-bit sigma-delta ADC
» Integrated, precision measurement solution for accurate prediction of battery state of health, state of charge, or state of function.
» Flexible wake-up modes allow minimum power consumption without sacrificing performance
» No temperature calibration or external trimming components required
» Industry’s smallest footprint allows minimal module size and cost
PRODUCT WATCH
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– Josh Bishop, EEWeb Tech Lab
to thousands of amps. Accumulator
registers allow accurately calculating
state of charge even in operating modes
when the microcontroller is asleep.
With the ZSSC1956, you can constantly monitor the most important aspects of your battery’s performance in a very small form factor. In low-power mode, it only draws one hundred microamps, so this information and management comes with practically zero effect on the performance of the system.
The ZSSC1956 isn’t just for automotive applications but also for industrial or medical systems that use lead acid batteries. To find out more information and to see how this can fit in your next application, go to IDT.com.
Click the image below to watch a video overview of the ZSSC1956:
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Power Developer
Moves Beyond InductionBy Michael Nagib Technical Marketing Leader ASIC Solutions Business Unit Si-Ware Systems www.si-ware.com
Wireless Charging
TECH REPORT
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New chipset enables wireless power charging for multiple devices at a distance of 10m
The wireless charging market will see exponential
growth over the next several years. The growing
panoply of mobile devices in the home, increased
interest in wearables, and the gradual evolution of
the Internet of Things (IoT) foreshadow a huge surge
in the number of battery-powered devices in the
home and office. These devices will require recharging
without resorting to a daily routine of plugging in,
battery swaps, or a rat’s nest of cables in every room.
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Power Developer
Wireless Charging: Moving Beyond Induction
Much of the induction-based charging technology we see today has severe limitations in range and freedom of motion. The current standard, induction-based charging, requires either contact or very close proximity (within centimeters) to a mat or transmitter. The drawbacks are evident—you must place your devices on a mat and leave them there to charge.
The Charging Challenge
Si-Ware and Ossia have developed Cota, a fully integrated chipset for a new, RF-based wireless charging approach. Cota can efficiently power devices wherever they are, even roaming in a building, without the constraints of induction or other forms of line-of-sight charging techniques. Ossia’s main requirements for the design included having a commercially viable first-generation chipset that would not only demonstrate the charging technology but also demonstrate the viability of the technology in everyday use. The main functionality of the system is to deliver power to multiple client devices in a dynamically changing environment at a radius of up to 10m. The system needed to overcome line-of-sight dependency yet avoid obstructions, all while charging small devices, even in a hand or purse. Receiver chips had to be small enough to be integrated into almost any device, from a smartphone to an AA battery. More importantly, the transmitter/receiver chipset had to be cost-effective and manufactured using standard CMOS technologies for deployment in cost-sensitive consumer applications.
Si-Ware and Ossia have developed Cota, a fully integrated chipset for a new, RF-based wireless
charging approach.
TECH REPORT
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The Cota solution is a multipath technology, relying on smart micro-
antennas to find multiple optimal paths for delivering RF power from the charger to the client receiver.
Fig. 1. Wireless charging must deliver power to multiple devices in a changing environment at up to a 10-m radius.
Using Smart Antennas for a Massive Multipath Approach
The Cota solution is a multipath technology, relying on smart micro-antennas to find multiple optimal paths for delivering RF power from the charger to the client receiver. Rather than inefficiently blasting out power in hopes of hitting the target devices, multipath technology relies on dynamic location tracking and precise RF signals sent directly to the receiver, avoiding obstructions in the environment.
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Si-Ware’s chipset solution is based on Ossia’s Cota wireless charging concept. Detailed analyses and system-level simulations of overall system operation at frequent intervals led to the development of a transmitter (See Fig. 1. SWS1410) and receiver (See Fig. 2. SWS1420) chipset that supports up to eight simultaneous clients and is produced in standard CMOS technology. An evaluation kit for the Cota technology based on the SWS1410 and SWS1420 will be available in the second half of 2016.
Obstacle Avoidance and Safety
The implementation of the massive multipath technique answered the requirements for obstacle avoidance and human safety but necessitated work on integration and silicon dimensions to satisfy volume production needs. On the safety side, both chipsets have a variety
of special features and error-detection mechanisms to detect and prevent any unexpected behavior in the system in any mode of operation. Both charger and receiver include signal-strength indicators, temperature sensors, and safe power-up infrastructure to monitor and ensure safe operation of the whole system under different operating conditions.
Power Management
Power management begins with optimizing power delivery per client on the system level, proceeding down to efficient extraction of RF power on the client side, and then interfacing to the battery in the most economical way. The SWS1410 charger ASIC has built-in power management features and flexibility that enable dynamic system-level optimization of the power delivered to different devices, enabling the charger
Fig. 2. The SWS1410 MIMO transceiver detects the location of multiple devices simultaneously and transmits RF power to those devices through a multipath approach.
On the safety side, both chipsets have a variety of special features and error-detection mechanisms
to detect and prevent any unexpected behavior in the
system in any mode of operation.
TECH REPORT
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to prioritize charging based on the nature of the device, and battery state-of-charge. On the client side, the SWS1420 has an embedded dynamic MPPT (maximum power point tracking) loop that dynamically enhances the RF-to-DC rectification efficiency. It also has a buck/boost converter that acts as a host-controlled battery interface supporting li-ion battery charging profiles. This enables the client ASIC to directly charge the system battery, reducing the number of additional power-management elements and the associated extra power consumption and inefficiencies.
Streamlining Chip Architecture
The SWS1410 transmitter chip includes its own CPU and RAM to offload the location data calculations and storage overhead from the main system controller. These features enable the SWS1410 ASIC to operate in a completely autonomous
mode and significantly reduces the overall cost and complexity of the complete Cota charger. The SWS1420 client ASIC integrates a complete host-controlled battery interface that is compatible with popular li-ion batteries, to reduce overall integration cost and complexity in the product migration path. Additionally, both chips support a wide range of applications and devices. One key objective was the ability to enable OEM partners—from wearables to smartphone accessory and battery manufacturers—to easily integrate a small Cota receiver chip into their products. To address size and reduce the bill of materials (BOM) on the Cota charger side, the SWS1410 integrates four antenna management units with the location detection and tracking infrastructure—including the functionality of more than 10 RF and digital chips—into a single ASIC. On the client side, a complete power-management solution with MPPT loop and battery interface in the receiver IC is included—also to reduce the BOM—for OEMs integrating chips into their own devices.
Fig. 3. The SWS1420 receiver rectifies and converts RF power into DC power to charge batteries and transmit a beacon signal to assist in client dynamic location tracking.
The SWS1420 client ASIC integrates a complete host-controlled battery interface
that is compatible with popular li-ion batteries.
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Power Developer
Alex Lidow, Ph.D., CEO and Co-founderDavid Reusch, Ph.D., Executive Director of Applications EngineeringJohn Glaser, Ph.D., Director of Applications Engineering
Efficient Power Conversion Corporation
Server Power Architecture
R E T H I N K I N G
in a Post-Silicon World
TECH REPORT
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The demand for information in our
society is growing at an unprecedented
rate. With emerging technologies, such
as cloud computing and the Internet of
Things, this trend for more and faster
access to information is showing no signs
of slowing. What makes the transfer
of information at high rates of speed
possible are racks and racks of servers,
mostly located in centralized data.
centers.
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Power Developer
In 2014, data centers (in the U.S.) consumed about 100 billion kilowatts hours (kWh) of energy [1,2]. According to Sudeep Pasricha, an associate professor in the Department of Electrical and Computer Engineering at Colorado State University; “That’s almost twice the electricity needed to power the whole state of Colorado for a year.” [2]
The power needed to support this rapidly growing demand comes from our electrical grid, and goes through multiple conversion stages before it actually feeds the remaining energy into a digital semiconductor chip. In Figure 1 is an illustration of this “journey.” Also shown in this figure are the losses due to the transmission and conversion of electricity—from the power plant to the computer chip that does all the work.
Multiplying these efficiency numbers shows that the power grid needs to supply 150 watts of power to meet the demands of a digital chip that may need only 100 watts of power. Therefore the combined waste across the U.S. due to power conversion for servers is 33 billion kWh, enough to power over half of the state of Colorado. But the overall wasted energy
Figure 1. Typical multi-stage power conversion architecture used in modern server farms, which takes 150 watts of power from the electrical grid to supply 100 watts to a digital processor used in servers [3,4].
DistributionTransformers
UninterruptablePowerSupplies
(UPS)
AC/DCConversion
DC/DCConversion
DC/DCConversion
DC/DCConversion
DigitalChip13.8kVAC
208VAC 208VAC 400VDC 48VDC 12VDC 1VDC
98%
93%
97% 98% 98% 95% 85%98%
150W100W
Figure1:Typicalmul1-stagepowerconversionarchitectureusedinmodernserverfarms,whichtakes150wa@sofpowerfromtheelectrical
gridtosupply100wa@stoadigitalprocessorusedinservers[3,4].
Figure1
within the server farm is even more, because every watt of power loss through power conversion is actually energy that is converted into heat, and removing this heat demands even more power.
Whereas the electrical grid has been around for more than a century, the various stages of conversion have been built with technologies based on the semiconductors developed post World War II. These semiconductors are based on silicon crystals, and it is the properties and limitations of silicon that shaped the architecture of Figure 1.
In this article, we will demonstrate the benefits of enhancement-mode gallium nitride (eGaN® technology) based power converters in solutions for existing data center and telecommunications architectures centering around an input voltage of 48 VDC with load voltages as low as 1 VDC. We will explore the capability of high performance GaN power transistors to enable new approaches to power data center and telecommunications systems with higher efficiency and higher power density than possible with previous Si MOSFET based architectures.
TECH REPORT
27
eGaN Monolithic Half-Bridge IC based 48 VIN – 1 VOUT POL Converter
Since the adoption of the 12 V intermediate bus architecture (IBA), bus converters are currently approaching about an order of magnitude increase in output power, from around 100W to current designs of around 1 kW in a quarter brick footprint. This means that the amount of current on the 12 V bus to the POL converters has also increased by a factor of 10 and, without reductions in busing resistance, a two order of magnitude increase in busing conduction losses follows. GaN technology-based solutions have already demonstrated significant efficiency improvements compared to silicon based solutions in traditional IBA systems [4].
However, with the increasing conversion losses in the 48 VIN bus converter, the mounting 12 V busing losses on the motherboards, and the higher
performance of GaN technology, different architectures may now be considered, such as going directly from 48 VIN to load using non-isolated POL converters, as shown on the bottom of Figure 2.
To evaluate converting 48 VIN directly to 1 VOUT, an 80 V eGaN monolithic half-bridge IC (EPC2105), embedded in an EPC9041 demonstration board, was selected for the much higher step-down ratio. The total system efficiency and power loss for the eGaN FET based 48 VIN to 1 VOUT buck converter operated at switching frequencies of 300 kHz and 500 kHz are shown in Figure 3. This efficiency is that of the entire system, including the inductor (Würth Elektronik 744 301 033), capacitors, and PCB losses. At 500 kHz, a peak efficiency of over 80% is achieved for the full buck converter system. At 300 kHz, a peak efficiency of 84% is achieved for the full buck converter system, and at 20 A the efficiency is around 83.5%.
Figure 1. Typical multi-stage power conversion architecture used in modern server farms, which takes 150 watts of power from the electrical grid to supply 100 watts to a digital processor used in servers [3,4].
Figure 2. Intermediate bus architecture (IBA) and a direct conversion DC bus architecture.
Figure2
DC Bus48 V 12 V 1 V
POLIBC
Intermediate Bus Architecture
DC BUS 48 V 1 V
POL
DC Bus Architecture
Figure2:Intermediatebusarchitecture(IBA)andadirectconversionDCbusarchitecture.
Figure3
66
68
70
72
74
76
78
80
82
84
86
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32
Effic
ienc
y (%
)
Output Current (A)
fsw=300 kHzfsw=500 kHz
80 V eGaN FET Monolithic HB
VIN=48 V VOUT=1 V L=330 nH
Figure3:EfficiencyforeGaNmonolithicHBICbasedPOLconverter,VIN=48VtoVOUT=1V,fsw=300kHzand500kHz.
Figure 3. Efficiency for eGaN monolithic HB IC based POL converter, VIN=48 V to VOUT=1V, fsw=300kHz and 500kHz.
28
Power Developer
96% 88%
96%x98%88%≈83%
≈250W/in3
DC Bus48 V 12 V 1 V
POLIBC
IntermediateBusArchitecture
fsw=300kHz550W/in3 fsw=1MHz500W/in3
DC BUS 48 V 1 V
POL
DCBusArchitecture83%
≈83%≈300W/in3
fsw=300kHz300W/in3
98%
A comparison of estimated efficiencies and power densities for the single stage 48 VIN to 1 VOUT POL converter, and the traditional two-stage IBA approach using the best GaN technology—based design is shown in Figure 3 and summarized in the table below (Silicon-based solutions are significantly less efficient than these GaN technology-based solutions). The GaN IC-based IBA’s power converters have an estimated 1.5% efficiency improvement over the direct 48 VIN
to 1 VOUT conversion. However, when adding in the losses from the 12 V bus, estimated to be 2% [5]–[7], the total system efficiencies are very similar.
The DC bus architecture also has a cost advantage, since the cost of the IBC can be eliminated and the cost increase of the 48 VIN POL converter over the 12 VIN POL converter will be minimal as they use a similar number of power devices, controllers, and drivers.
Figure 4. Performance comparisons of GaN technology-based 48 VIN intermediate bus architecture and 48 VIN DC bus architecture.
“eGaN devices enable the elimination of an entire stage in the power conversion
journey, reducing total server farm losses by about 7%.”
TECH REPORT
29
Parameter Units 48 VIN IBA 48 VIN Direct Conversion
48 VIN – 12 VOUT
IBC
12 VIN – 1 VOUT POL
48 VIN – 1 VOUT POL
Stage Switching Frequency kHz 300 1000 300
Total Power Devicesa 32 32
System Transformer Isolation Yes No
PCB Complexity High Low Low
Stage Efficiency % 96 88 83
Bus Efficiency % 98 99.9%
Total System Efficiency % 82.8 82.9
Stage Power Density W/in3 (W/cm3) 550 (34) 500 (31) 300 (18)
Total System Power Density W/in3 (W/cm3) 250 (15) 300 (18)
(a) Scaled to 500 W of output power.
Figure 5. eGaN devices enable the elimination of an entire stage in the power conversion journey, reducing total server farm losses by about 7%.
In Figure 5 we revisit Figure 1 while applying the single-stage efficiencies demonstrated with eGaN ICs. The direct savings by eliminating just the last stage in the server farm power architecture is not only a cost reduction, but also a reduction of power consumed by 7%, or a direct savings of 7 billion kWh
Figure5
DistributionTransformers
Uninterruptable2Power2Supplies2
(UPS)
AC/DC2Conversion
DC/DCConversion
DC/DCConversion
Digital2Chip13.82kVAC
2082VAC 2082VAC 4002VDC 482VDC 12VDC
98%
93%
97% 98% 98% 8 %
1402W1002W
Figure5:eGaNdevicesenabletheelimina1onofanen1restageinthepowerconversionjourney,reducingtotalserverfarmlossesbyabout7%.
per year when compared with today’s silicon-based solution. This savings is increased further when air conditioning energy costs inside the server farm are added [10], bringing the total to more than 10% of the 100 billion kWh consumed by servers in the U.S. alone.
30
Power Developer
REFERENCES
[1] Natural Resource Defense Council, http://www.nrdc.org/energy/data-center-efficiency-assessment.asp
[2] http://source.colostate.edu/powering-down-researchers-reducing-energy-usage-at-data-centers/
[3] https://en.wikipedia.org/wiki/Electric_power_transmission#Losses
[4] D. Reusch and J. Glaser, DC-DC Converter Handbook, Power Conversion Publications, 2015. ISBN 978-0-9966492-0-9
[5] A. Naghavi, “Energy Efficiency Becomes the Focus for Data Centre Servers,” Bodo’s Power Systems, pp. 22-25, January 2011.
[6] P. Yeaman, “Datacenter Power Delivery Architectures: Efficiency and Annual Operating Costs,” Darnell Digital Power Forum, 2007.
[7] R. Miftakhutdinov, “Improving System Efficiency with a New Intermediate-Bus Architecture,” Texas Instruments Inc. Seminar, 2009.
[8] K. Yao, “High Frequency and High Performance VRM Design for the Next Generations of Processors,” Ph.D. Dissertation, Virginia Tech, 2004.
[9] Y. Ren, “High Frequency, High Efficiency Two-Stage Approach for Future Microprocessors,” Ph.D. Dissertation, Virginia Tech, 2005.
[10] M. Gregory, “Inside Facebook’s green and clean arctic data center,” BBC News, June 14, 2013. http://www.bbc.com/news/business-22879160
[11] D. Holmes, “As Moore’s Law turns 50, is there any way to save it from dying? Is it worth saving?” Pando, April 21, 2015. https://pando.com/2015/04/21/as-moores-law-turns-50-is-there-any-way-to-save-it-from-dying-and-is-it-worth-saving/
eGaN® FET is a registered trademark of Efficient Power Conversion Corporation.
The impact of eGaN technology in our post-silicon world is even greater than the savings possible in U.S. server farms today and is but one example of the impact that this new, emerging technology makes to the efficient use of electrical power. eGaN technology provides a path to higher performance semiconductors, re-opening the possibilities of Moore’s Law for driving innovation—just as Moore’s Law falls off the tracks [11]. For example, eGaN technology is enabling new applications such as wireless power transmission, 5G cellular, autonomous vehicles, and colonoscopy pills. And, as the electronics industry gains experience and knowledge in the inherent attributes high performance capabilities, the resulting high performance eGaN semiconductor devices will enable many unforeseen applications, just as silicon, its predecessor, brought about in the post-WWII era.
“eGaN technology is enabling new applications
such as wireless power transmission, 5G cellular, autonomous vehicles, and
colonoscopy pills.”
32
Power Developer
What You Need to Know
By Bob Cantrell Senior Application Engineer Ericsson Power Modules www.ericsson.com
Power Density
VersusArchitecture
TECH REPORT
33
Digital power and advanced thermal management combine to overcome today’s power-conversion challenges.
Prolonged exposure to high operating temperatures is known
to be one of the greatest enemies of electronic components.
This tends to accelerate failure of semiconductors and
promotes other wear-out mechanisms such as drying of
wet electrolytic capacitors. For every 10°C rise in operating
temperature, life expectancy decreases by about 50%,
according to the rule of thumb. Conversely, reducing the
temperature by 10°C can double the expected reliability.
Power Density
34
Power Developer
Internal heat dissipation caused by inefficiency in the conversion process is a major contributor to excessive
operating temperature. In effect the equipment operator pays twice for inefficient power conversion: Every watt dissipated is another watt that must be cooled, hence demanding extra air-conditioning or cooling capacity to keep the ambient temperature within specified limits as total system power dissipation increases. Clearly, improving energy efficiency can improve reliability and reduce operating costs by reducing the demand for system cooling.
However, another figure of merit for power converters is current density. Higher current density means smaller devices for a given power rating, which ultimately allows system designers to use more of the expensive board real estate for revenue-generating devices—such as processors, ASICs, or FPGAs—that add functionality. Moreover, small PoL converters, in particular, can be placed closer to the power pins of the main ICs on the board for the best possible transient performance.
Desirable characteristics are for a converter to be simultaneously smaller, more energy-efficient, and with excellent heat-dissipating properties. Dealing effectively with heat is critical to maximizing current density or to power-handling capability. A good analogy is to consider two runners of equal height, weight, and fitness running in hot conditions, such as at midday in the Arizona desert. The only difference is that one is wearing suitable lightweight running gear, while the other is wearing a thermal outfit that prevents heat from leaving the body. On paper, both can achieve the same performance. But the second runner will not be able to shed the heat his body is creating as efficiently as the first and soon will be unable to continue running.
Solving the dilemma, digitally
Digital technology can help to overcome the challenges facing power conversion. For example, digital converters can be smaller because they require fewer components than a conventional analog converter topology. The reduction in component count also helps to boost reliability. In a digital converter, the output voltage is sensed in the same way as in an analog design, but there is no error amplifier. Instead the sensed voltage is digitized by an A/D converter, and the digitized values are input to a control algorithm hosted on a microcontroller. Various algorithms can be used to optimize performance as the operating conditions change. Fig. 1 illustrates the main functional blocks of a digital converter.
Fig. 1. Digital power conversion simplifies circuit design and reduces component count.
IMPROVING ENERGY EFFICIENCY
CAN IMPROVE RELIABILITY AND
REDUCE OPERATING COSTS BY REDUCING
THE DEMAND FOR SYSTEM COOLING.
TECH REPORT
35
Converters such as Ericsson’s 3E single-phase PoLs feature advanced energy-optimization algorithms to enhance efficiency across the load range. Also, with a specific input voltage, output voltage, and capacitive load, these converters permit the control loop to be optimized for a robust and stable operation and with an improved load-transient response. This optimization minimizes the amount of output decoupling capacitors needed to achieve a given load-transient response, optimizing cost and minimizing board space. This effectively simplifies hardware design, reduces overall module size, and helps to boost reliability. Fig. 2 shows how digital converter technology enables designers to boost efficiency at light loads, for which traditional analog converters are often less efficient.
Other aspects of the 3E PoLs that help enhance efficiency include the latest-
generation power MOSFETs, which have low internal capacitances and optimal on-resistance x gate-charge figure of merit (RDS(ON) x Qg) to minimize conduction and switching losses at all times.
The latest converter in the family, the BMR466, can deliver up to 60A and has been shown to achieve efficiency of 94.4% with a 5-V input and a 1.8-V output, at half load. The MTBF of the BMR466 is calculated at 50 million hours based on the industry-standard Telcordia method.
As many as eight BMR466s can be connected, allowing designers to rely on a single part number when powering applications between 60A and 480A. It is also possible to synchronize two or more BMR466s with an external clock to enable phase spreading, which helps lower input ripple current and, therefore, effectively reduces capacitance requirements and efficiency losses.
Fig. 2. Digital power converters can deliver significantly higher efficiency at light loads.
36
Power Developer
Advanced thermal performance
The internal design of the BMR466 is optimized to achieve a low package profile. Its height of 0.276 in. (7mm) minimizes interference with cooling airflow across the board. Moreover, the solder pad distribution of the LGA package gives excellent thermal performance and enables the module to dissipate heat very efficiently while benefiting from an extremely compact footprint of 0.98 x 0.55 in. (14 x 25 mm). The LGA contacts are positioned symmetrically to ensure superior mechanical contact and high reliability after soldering. Internally, the package technology eliminates connecting leads and their associated inductance, and a high number of the LGA contacts are ground pins. Together,
these features ensure excellent noise and EMI characteristics.
Improving thermal performance is the key to minimizing thermal derating, allowing higher output current without sacrificing reliability. Fig. 3 shows thermal derating curves for the BMR466 with an output of 1.0-V, which can deliver the maximum 60A at an ambient temperature of 70°C with natural convection cooling alone. For an ambient air temperature of 85°C, the converter can deliver 48A cooled with natural convection, or 55A with airflow of 1.0 m/s.
The derated current capability of the BMR466 is comparable to that of competing PoLs that have more than twice the surface area and occupy nearly four times the volume, even though
Fig. 3. Thermal derating for BMR466 PoL converter with 1.0-V output.
IMPROVING THERMAL
PERFORMANCE IS THE KEY TO MINIMIZING
THERMAL DERATING, ALLOWING HIGHER OUTPUT CURRENT
WITHOUT SACRIFICING RELIABILITY.
TECH REPORT
37
these have higher maximum current ratings. Consider the derating curves for a competing 80A PoL, seen in Fig. 4, which show that the higher-rated converter has a real-life limit of 62 A for an ambient air temperature of 70°C with natural convection with a 1.0-V output. While this competing converter can deliver up to 60A at 85°C ambient temperature, with 1.0-m/s airflow, this is only marginally higher than the 55A available from the BMR466 operating under the same conditions even though the BMR466 is significantly smaller.
The larger 80A PoL has little more than one-third the current density of the BMR466. Considering that a single computing board for an application such as a data center server may need several—sometimes 10 or more—
Fig. 4. Thermal derating curves for alternative 80-A PoL with 1.0-V output.
high-current PoLs, the cumulative space savings that can be achieved, without derating the maximum current or degrading reliability, are significant and valuable.
In addition, the digital converter can be configured via a GUI such as Ericsson’s Power Designer software to ensure optimal efficiency and performance, the lowest BOM cost, and optimized transient response. This tool gives system architects control over parameters such as switching frequency and threshold settings for input and output under-/over-voltages, output over-/under-current limits, and over-/under-temperature to ensure optimum efficiency under a range of operating conditions. In addition, using phase spreading, the input ripple current can be dramatically reduced, thereby reducing input capacitance requirements and efficiency losses.
38
Power Developer
Interview with Allen Chen – Texas Instruments
High-voltage
Batteries Provide Unprecedented Flexibility for Cutting-edge Applications
INDUSTRY INTERVIEW
39
The move towards portability is becoming a key design element in
today’s electronic devices. With cables and cords disappearing at a
rapid rate, power engineers are moving towards batteries to manage
the power needs in new applications. At the same time, these
applications are adding new capabilities and complexities that create
significant power demands, leading to higher voltages and flexibility in
new battery technology. For Texas Instruments (TI), the battery market
is of key importance in the upcoming years. To address the trends
in the industry, TI has introduced a family of high-voltage battery
management products so customers can adapt to the ever-changing
power requirements by adding simple peripherals to unify the system.
EEWeb recently spoke with Allen Chen of Texas Instruments about the
company’s shift in focus in the battery market and some of the new
high-side FET drivers that are addressing cutting-edge applications.
40
Power Developer
How has TI’s battery offering changed since you arrived at the company?
I have been at TI now for nine years, and I joined the battery management team from the very beginning. Back then, we were really focused on notebook battery fuel gauges and the ICs that go into almost every notebook sold in the world. This helps users understand how much of a charge they have left in their mobile computers.
From there, I moved into business development and product marketing. This department figures out what solutions best fit our customers’ needs and what kind of technology we should be investing in. If you look at our battery management organization as a whole, we have grown tremendously in the nine years that I have been here. We have gone from being very focused on notebooks and mobile phones to going after any portable device.
The battery market in general has seen a sea change in the last five years. People have figured out how to develop really great, high-end battery systems for notebooks and using the same technology to apply
to the industrial and automotive space. As a whole, TI is very much focused in industrial and automotive, and for battery management solutions (BMS), that is a very natural fit for us—everything from drones to energy storage systems.
What is TI focusing on now that is really exciting?
When I first started in this role, everyone was talking about small power tools. We would go off for two years developing one product that was great for going into power tools, but it wasn’t very adaptable for anything other than that. As soon as it was released, we realized that the market had moved beyond this application and everyone was focused on slightly larger battery packs.
We took a step back and re-booted our portfolio back in 2012; we realized that the only way to be successful is to become more versatile in the type of product development that we have. That’s when we embarked on this big transformation and we began to develop a family of devices that worked in concert with each other. Our customers would one day be designing an 18V power tool and the next day would be working on a 36V electric bicycle, and the day after that they might be working on a 48V energy storage system. That is the nature of the battery business today—the technology that started with a simple notebook has started to go higher end, but the fundamental requirements are still the same.
We are now focusing on accurately capturing battery characteristics like
We are now focusing on accurately capturing
battery characteristics
like, voltage, current, and
temperature, and using that
in a meaningful way when you connect it to a
microcontroller.
INDUSTRY INTERVIEW
41
voltage, current, and temperature, and using that in a meaningful way when you connect it to a microcontroller. We re-booted the way we develop these products; instead of creating one device, we decided to create a family of products—a small, a medium, and a large—that monitor the batteries.
In what ways are you addressing optimization and scalability?
We need to be able to scale these power management devices up and down for different types of applications. We decided to create a new category of devices called peripherals. These are devices that not every customer is going to need, but may need down the road because the battery market is so fragmented. In a lot of cases, customers will require this, but perhaps in a few years, they might need to migrate these applications to support these extra-enhanced functionalities.
First, we established the baseline new family of battery monitors and from there, the peripherals allow you to greatly extend the capabilities of those battery packs. When you invest in TI, you are future-proofing your battery platforms because all you need to do is check out our portfolio and take that extra-enhanced solution that sits on top of the existing core products that you already selected. That’s where this new device comes in—our high-side FET driver, bq76200. If you look at the existing offerings on the market today, this is not really a new idea, but we have made this device fit
One of the great things
that happened as a result of
TI’s acquisition of National
Semiconductor was that we
gained access to a whole
new toolbox of new analog
processes.
across our entire portfolio, which is maximized for battery applications.
What is so unique about the new family that TI just released?
This is the first time a truly battery-optimized solution for high-side FET drivers has become available. One of the great things that happened as a result of TI’s acquisition of National Semiconductor was that we gained access to a whole new toolbox of new analog processes. This is one of the things that we consider our core competency—we control the manufacturing aspect and we also are able to leverage our 100V+ analog process.
For the first time, we realized we were able to create this companion device that was previously impossible. If you look at a notebook battery management solution, 100% of them will do high-side battery FET driving. That is primarily there to control charging and
42
Power Developer
discharging of the battery back; each one is in a different direction, so they do a bi-directional back-to-back and they sit on the high side and they are both enabled. There are some situations where you may need to turn off one or the other. In the battery management world, this was a challenge we solved almost 20 years ago because it is a more reasonable challenge to design this type of circuit for a product that is fairly low power and low voltage.
The challenge becomes more complex and interesting when you start talking about how to support the various types of voltages in the battery market that have the same requirements but the problems have scaled up substantially. We were able to access this new technology node that was quite difficult for us to achieve. Then, because we have the new baseline of battery monitors, these solutions paired nicely with those. It is the first time we have been able to create a product that scales anywhere from 8V at the low end up to 75V on the high end. These are nominal operating voltages, and they can survive transients up to 100V, which has not been possible in the past.
We came at this problem from the battery world. We knew that the solution had to be ultra low power if it was going to succeed with the new requirements for batteries. This device needs to be running at all times, so you can consume milliamps of current and quickly discharge the battery. We designed the solution to have the target of 40 microamps or less. This is a result of the expertise that we have in the battery world and catering to the expectations of our customers.
What is TI doing with regards to alternative energy solutions?
Energy storage systems are the future of battery technology. If you look at the market news, the growth that is projected from now until 2020 is huge. Large capacity battery packs and energy storage systems are primarily driving this huge growth. This high-side FET driver, the bq76200 directly addresses the need of a lot of these emerging energy storage requirements. Here, you have a lot of fragmentation in terms of supply voltages that they have to support and capacities that they have to support. Whether you are making a data center backup battery system, or one for your home emergency use, you essentially should be able to design one module and then add additional capabilities from there. That way, you get the best of both worlds and you get the scale that you need for a lot of the larger applications, or you can get something really small that is just for the house.
Engineers should not have to design a new thing every single time, which is where our device comes in. Adding this in gives you the flexibility to support a large variety of capacities and the modularity comes in because you simply use one per battery module to attach or disconnect the individual batteries from the overall installation. It gives the customer and the end user a lot of flexibility in using these batteries in catering to exactly what they need.
Whether you are making a data center
backup battery system, or one for your home
emergency use, you essentially
should be able to design
one module and then add
additional capabilities from there.
INDUSTRY INTERVIEW
43
What new technologies and trends is TI targeting?
The focus that we have right now is on emerging technologies like alternative energy and energy harvesting. For our product line specifically, we have established the building blocks of battery monitors and protectors, and with our peripherals category, we are going to see this expand upwards and outwards - upwards in voltage range and outwards in feature integration. This first part we created, the BQ72600, addressed the idea that we should go to higher voltages. The sophistication level for some of these devices will only increase as customers continue to demand more out of what they have.
There is another technology that is super interesting and will begin to dominate the battery space: active cell balancing. Basically, every single battery pack, when you put in lithium-ion cells, there is a stack of batteries to get the voltages that you need. However, every cell is going to age and degrade at its own pace. Every single time you use a battery, whether it is large voltages that are made up of large batteries stacked on top of each other, it’s going to run out as soon as the weakest one is done. In other words, the full charge is determined by the weakest cell and the discharge is determined by the weakest cell.
There is a concept called cell balancing, which is really a way to condition a battery pack and enable it to be as healthy as possible. The approach that everybody takes today is called passive
The focus that we have right now is on emerging technologies like alternative
energy and energy harvesting.
44
Power Developer
balancing, which means you are moving the charge from a stronger battery cell by heat and heat loss. This is fine and really low cost. The active cell balancing goes along with the green movement and the problem of wasting energy when you really don’t have to. This only becomes viable when you start talking about truly large capacity battery packs, like 100-amp-hours or beyond. The problem here is that you can’t remove the excess charge as heat. With active cell balancing, you can use this heat and energy and pump it back into the battery and back into the weaker portion of the battery stack to prop up the system overall. Reusing unusable energy from a stronger set of cells and putting it into the weaker set of cells also lets the system run longer overall.
What is TI anticipating in the next three years?
The requirements for our customers continues to move along very specific directions. One of these requirements is that they need to extract as much value as they can from their batteries. Batteries are still the most expensive parts of the overall system, so in order to do this, you need to have very high accuracy to capture all of the information about the cells as precisely as you can, which determines tolerance margins. You don’t ever want your battery to exceed a certain voltage otherwise bad things can happen. The tighter you can make those tolerances, the closer you can get to that critical limit in your overall system. That is one of the ways we are able to help customers extract more use out of the existing system.
The other trend we are seeing is that people are going to higher voltages. People were comfortable first with notebook designs, then they were comfortable with small, hand-held power tools, and now people are talking about energy storage systems with high voltage batteries. People are going from 48V solutions to stackable solutions up to 400V. We are seeing cell costs come down and that is really encouraging everyone to use more batteries as much as they can.
As far as our products are concerned, nobody else in the industry has the breadth of products that Texas Instruments does. We create super low-power wearable or smartphone battery protectors and battery monitors that go into notebooks and industrial and automotive applications and we create peripherals and authentication options to prevent users from having counterfeit batteries. We also have an entire team devoted to firmware products and fuel gauges; it is essentially a battery-optimized controller that is running firmware that helps you understand, from a chemical perspective, how much capacity your batteries have and whether it is a healthy battery. I am truly excited to see what new innovations our customers will conjure up using these building blocks that we have developed.
As far as our products
are concerned, nobody else
in the industry has the
breadth of products
that Texas Instruments
does.
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