April 4, 2009
How to Measure Efficiency of a Multiple-Output Power Supply
On March 27, 2009, the US Department of Energy (DOE) published an amendment to its test procedures for battery chargers and external power supplies (EPS). The amendment includes provisions for measuring standby mode and off mode energy consumption and adds a test procedure for testing switch-selectable external power supplies. Since the document basically clarifies existing test procedures, which DOE originally could not formulate clearly, it is mainly clerical and would not be worth noting if not for one funny thing. The amendment still does not include a test procedure for multi-output power supplies because of "the number of stakeholder comments and the limited timeframe for this rulemaking." OK, here is a little background. The Energy Independence and Security Act of 2007 (EISA 2007) set Federal efficiency standards for certain types of adapters and single-output EPS for consumer electronics. DOE has a test procedure to verify this efficiency. However, this procedure [which is basically: multiply output volts times amps and divide by the input power under various loading conditions] was written for single-output power supplies. It has therefore left out a significant group of products, powering applications such as radio transceivers, video game consoles, and printers. On August 15, 2008, DOE proposed a procedure for the testing of multiple-voltage external power supplies. On page 6 of the Proposed Rule we read: "DOE is not aware of any existing test procedure developed specifically to measure the efficiency or energy consumption of multiple-voltage external power supplies." Huh? Millions of multi-output power supplies both external and internal including PC PSUs are being built around the world and tested for Energy Star® and 80 PLUS® efficiency compliance. Folks, how about this: take a 5th grader, ask him/her to add up volt-amps of all outputs, divide by the input power, and you are done! Seriously, the main obstacle for DOE seems to be the loading profile. The PSU's nameplate power is often smaller than the sum of the nameplate power of each individual output. So what's the big deal? Derate (scale down) the loads of all the outputs proportionally, so that their sum does not exceed the limit for the entire power supply. Of course, it would not be the worst case efficiency (which you would probably encounter if you shift the bulk of the load onto the lowest voltage outputs), but it would be kind of typical efficiency. Back in 2006, at the APEC conference, EPRI Solutions and Ecos Consulting presented their Enhanced Proportional Allocation Method for Loading Power Supply. Their method is incorporated by Intel in its PC power supply guides. DOE did propose to adapt the ‘‘proportional allocation’’ method. Nevertheless, the DOE 2009 final rule still reads: "Due to the limited time provided by EISA 2007 and limited resources available prior to the publication of this final rule, DOE was unable to address the large number of stakeholder comments received and decided to defer action on multiple-voltage EPSs to a 2009 rulemaking." In a private sector usually a new power supply will be designed, built and tested in this timeframe or in a shorter one. It's entertaining to watch how long will it finally take for US DOE to make up their mind on how to test the efficiency and to move to something else.
January 28, 2009
California Emission Standards
President Obama has directed EPA to re-examine whether California and other states should be allowed to set their own auto emission standards that are tougher then federal standards. New EPA administrator Lisa Jackson was quoted as already saying she would “very, very aggressively” review CA’s application.
For reference, the 2007 U.S. Energy Bill raises mileage standards to 35 MPG and reduces CO2 emissions from autos by 30% by 2020. The California regulations require car makers to meet the same standards, but four years earlier- by 2016.
Of course, the reduction of air pollutions is long overdue – we all need this. However, allowing individual states to set standards tougher then federal ones is simply illogical. If Obama and EPA believe that meeting CA regulations by 2016 is technically possible and economically feasible, why not simply incorporate CA standard into a national standard? If CA's timeline is doable, why not to enforce it nationwide to sooner reduce the emissions in all states?
Since Obama and EPA did not state their intention to harmonize national standards with CA regulations, they apparently are not so confident that the automakers can meet CA's timetable. Indeed, it was estimated that implementation of the original federal rules by 2020 would cost the auto industry $115 billion. It would cost even more to meet these rules four year sooner. Where are US car makers going to get this additional money when they need billions of dollars just to stay afloat? Proponents of accelerated regulations say the automakers are in trouble because they don't make competitive cars. This is partially true. However, right now people don't buy enough cars not because the cars don't meet particular emissions and not even because they don't feature particular mpg. We already have high mpg hybrids. Right now, the reason why people are not buying cars is that they can't afford them, or can't get a loan. Besides getting car loans flowing again, the only thing that could boost car sales and revive the industry at this moment is lowering the upfront cost for the buyers. IMHO this would require freeze on all new regulations and of course, concessions from the unions. Note that according to GM's Vice Chairman Lutz, the CA waiver would add to the cost of the cars $4,000 to $5,000 on average. And at $2/gal, going from 28mpg to 35mpg will save us only $1429 over 100K miles.
But maybe California Air Resources Board (CARB) knows what it is doing? Well, the outcome of another California emission regulations -- the regulation of off-road engines [that particularly included emergency electric generators] is worth noting. When CARB began introducing these regulations, the Diesel Technology Forum, a non-profit educational organization, warned that when real lives are at stake and businesses are at risk, this is not the time to try to impose more stringent limits on emergency generators. CARB did not listen. They must have thought that once a regulation is enacted, the compliant products will magically appear. Not so. If you browse generators' for sale sites, you will see that many residential generators in the US market still state "not CARB-compliant, not for sale in CA." If EPA will accept CA emission waiver, a similar thing may happen with cars. Some automakers or some models may meet the new standards by 2016 and some might not. As automakers warned, they would have to produce two sets of vehicles (assuming they will not go belly up). As a result, residents of CA and those states that join them may experience a shortage of the new cars. This would additionally drive their cost up besides those extra $4K-$5K.
Everything has an appointed season, and there is a time for every matter. A time to enact regulations and a time to freeze regulations; a time to reduce emissions, and a time to reduce the cost...
For reference, the 2007 U.S. Energy Bill raises mileage standards to 35 MPG and reduces CO2 emissions from autos by 30% by 2020. The California regulations require car makers to meet the same standards, but four years earlier- by 2016.
Of course, the reduction of air pollutions is long overdue – we all need this. However, allowing individual states to set standards tougher then federal ones is simply illogical. If Obama and EPA believe that meeting CA regulations by 2016 is technically possible and economically feasible, why not simply incorporate CA standard into a national standard? If CA's timeline is doable, why not to enforce it nationwide to sooner reduce the emissions in all states?
Since Obama and EPA did not state their intention to harmonize national standards with CA regulations, they apparently are not so confident that the automakers can meet CA's timetable. Indeed, it was estimated that implementation of the original federal rules by 2020 would cost the auto industry $115 billion. It would cost even more to meet these rules four year sooner. Where are US car makers going to get this additional money when they need billions of dollars just to stay afloat? Proponents of accelerated regulations say the automakers are in trouble because they don't make competitive cars. This is partially true. However, right now people don't buy enough cars not because the cars don't meet particular emissions and not even because they don't feature particular mpg. We already have high mpg hybrids. Right now, the reason why people are not buying cars is that they can't afford them, or can't get a loan. Besides getting car loans flowing again, the only thing that could boost car sales and revive the industry at this moment is lowering the upfront cost for the buyers. IMHO this would require freeze on all new regulations and of course, concessions from the unions. Note that according to GM's Vice Chairman Lutz, the CA waiver would add to the cost of the cars $4,000 to $5,000 on average. And at $2/gal, going from 28mpg to 35mpg will save us only $1429 over 100K miles.
But maybe California Air Resources Board (CARB) knows what it is doing? Well, the outcome of another California emission regulations -- the regulation of off-road engines [that particularly included emergency electric generators] is worth noting. When CARB began introducing these regulations, the Diesel Technology Forum, a non-profit educational organization, warned that when real lives are at stake and businesses are at risk, this is not the time to try to impose more stringent limits on emergency generators. CARB did not listen. They must have thought that once a regulation is enacted, the compliant products will magically appear. Not so. If you browse generators' for sale sites, you will see that many residential generators in the US market still state "not CARB-compliant, not for sale in CA." If EPA will accept CA emission waiver, a similar thing may happen with cars. Some automakers or some models may meet the new standards by 2016 and some might not. As automakers warned, they would have to produce two sets of vehicles (assuming they will not go belly up). As a result, residents of CA and those states that join them may experience a shortage of the new cars. This would additionally drive their cost up besides those extra $4K-$5K.
Everything has an appointed season, and there is a time for every matter. A time to enact regulations and a time to freeze regulations; a time to reduce emissions, and a time to reduce the cost...
August 25, 2008
First Generic Power Supply Standard
Despite the fact that practically every electronic device needs a power supply unit (PSU), its requirements have not yet been standardized. Although some industries do have power supply standards (such as PICMG spec 2.11 for CompactPCI Power Interface and Power Supply Design Guide for Desktop PCs), these standards are for specific applications and do not have general usage.
IPC standard IPC-9592 is the electronic industry's first attempt to come up with a generic power conversion standard. The draft was initially developed by the IPC Power Conversion Subcommittee that included Dell, IBM, Lenovo, Hewlett Packard, Cisco Systems, Alcatel Lucent and Apple. This document standardizes the performance parameters for power conversion devices for various applications such as computers and telecommunications. It sets the requirements for design, qualification and conformance testing, manufacturing quality processes, and regulatory requirements. The document particularly lists applicable EMI standards and provides components derating guidelines. Although this standard is not mandatory (just like all IPC standards), due to the participation and support of major power supply users, one can expect its widespread acceptance.
In preparation for the standard release, IPC is planning a conference on November 6, in Irving, Texas, to discuss the details of the specification and outline the ideas that went into developing this standard.
Note that unlike Intel's Computer PSU Guides, IPC-9592 does not include any functional requirements such as voltages, currents, timing, connectors, etc. This is actually good for us, power supply designers. If our fellow digital engineers and system integrators would come up with a scalable power supply standard and would design their systems around standard PSU "bricks", OEM power supplies would become a commodity and would be primarily designed and built in the Far East. As a result, many of us designers, would have to become salespersons. But for as long as our fellow engineers choose to design their systems the way they please and then look for a custom PSU because their electrical and mechanical requirements can't be satisfied by off-the-shelf models, we, designers are in business. (-:
IPC standard IPC-9592 is the electronic industry's first attempt to come up with a generic power conversion standard. The draft was initially developed by the IPC Power Conversion Subcommittee that included Dell, IBM, Lenovo, Hewlett Packard, Cisco Systems, Alcatel Lucent and Apple. This document standardizes the performance parameters for power conversion devices for various applications such as computers and telecommunications. It sets the requirements for design, qualification and conformance testing, manufacturing quality processes, and regulatory requirements. The document particularly lists applicable EMI standards and provides components derating guidelines. Although this standard is not mandatory (just like all IPC standards), due to the participation and support of major power supply users, one can expect its widespread acceptance.
In preparation for the standard release, IPC is planning a conference on November 6, in Irving, Texas, to discuss the details of the specification and outline the ideas that went into developing this standard.
Note that unlike Intel's Computer PSU Guides, IPC-9592 does not include any functional requirements such as voltages, currents, timing, connectors, etc. This is actually good for us, power supply designers. If our fellow digital engineers and system integrators would come up with a scalable power supply standard and would design their systems around standard PSU "bricks", OEM power supplies would become a commodity and would be primarily designed and built in the Far East. As a result, many of us designers, would have to become salespersons. But for as long as our fellow engineers choose to design their systems the way they please and then look for a custom PSU because their electrical and mechanical requirements can't be satisfied by off-the-shelf models, we, designers are in business. (-:
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