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While the human race moves farther into the 21st century, projections are being made that the worldwide population will exceed 9 billion people by the year 2050. As these new inhabitants embrace technology and the power it consumes, the world will enter into an unprecedented energy crisis. There are two forces at work that must be considered. The first is the increase in the overall world population plus longer life spans due to better nutrition and medical advances. But the second is an increased adoption rate of technology such as cellular phones, personal music players, television (especially high definition), and in some countries simply electric lights by those who today do not have these devices. This generates an exponential growth in the projections of electrical consumption.
Additionally, all of these new technologies require infrastructure and, on a global scale, will consume electricity beyond what is currently being produced. With the projected growth, it is estimated that by 2030, over 300 new 1 gigawatt power plants will need to be constructed to meet this growing need. This number does not take into account the additional transmission lines required to carry the power to where it is needed. In the United States it is easier to build a wind farm for electrical generation (typically an 18 month process) than it is to build the high-voltage transmission lines to deliver the power (typically 5 years). The bottom line is that demand is continuously working against capacity and it's only going to get worse.
Both governments and consumers are now realizing the importance to improve the efficiency of the systems we use and also those we export to stem the rising rate of consumption. Engineers are challenged every day to lower the energy consumption of the machines they design. Components and subsystems are now required to use the least amount of energy for the function they perform. To make better choices during the design process, metrics that provide information on this efficiency are needed.
National Semiconductor is the first analog chip supplier to define a set of metrics that define how much energy is used to complete a certain function. Additionally, National has used these metrics to qualify an entire family of devices with world class power-to-performance — the PowerWise family of components.
Why metrics are created
Following World War II, automobiles were coming of age. The interstate highway system of the United States, Europe, and other developed nations were being expanded to allow for increased traffic as prices for automobiles declined. Gasoline was inexpensive, so the rule of the day was bigger and faster (while safety was not even a concern yet — no one had ever seen an airbag). However, as we entered into the 1970s, the Arab oil embargo sent fuel prices soaring and the U.S. experienced gasoline lines and fuel shortages. Prior to that period, consumers of automobiles generally did not consider the fuel efficiency of the model they purchased.
But following the "energy-crisis" 1970s, smaller more efficient automobiles (mainly Japanese imports at the time) dramatically increased in sales. Here, the American household embraced its first efficiency rating — the humble miles per gallon or MPG rating. Because of the variability of how the rating was measured, many of these early metrics were uncorrelated and could not be directly compared across automobile manufacturers. So, standards were implemented to make sure all MPG ratings were calculated in the same way. Now consumers could directly compare these rating to assist them in their purchase.
According to the U.S. Department of Transportation, automobiles of the 60s had average fuel economies of roughly 12 miles per gallon. Today, modern automobiles MPG ratings have improved roughly 50% over the 1960 models and high efficiency models exceed 30 miles per gallon (the Toyota Prius Hybrid is rated at 55 MPG). This trend was driven by shortages and rising fuel costs which are still present today. There is a direct parallel with the automotive manufacturers and the modern electronics industry. When electricity is inexpensive and plentiful, design considerations are mostly driven by features and price. When there is no longer an unlimited supply of power, efficiency becomes a higher valued design criteria.
With continued rising fuel costs, electricity costs have also continued to increase. This trend provided the next stop for the average household on the road of metrics with the EnergyStar rating — a measure on how much electricity an appliance would typically consume. Again, along with a unified method on how to measure the consumption, this rating allows consumers to compare two similar appliances, such as refrigerators, and see which one would cost less to run. The handy label on the appliance shows estimated annual electrical consumption and cost (assuming an average price for electricity). For an end product, this makes the decision much easier for consumers allowing direct comparisons between similar devices.
Efficiency metrics for the design engineer
History tends to repeat itself, and so it has been with the current expansion of our technological world. This time, shortages and rising energy costs are not only driven by supply, but our insatiable appetite for entertainment, information and communication. As part of modern electronic systems, overall power consumption is now a primary competing factor. Consider server farms where thousands of computers host websites that deliver everything from electronic commerce to streaming video. Saving 10 watts of power per server in a large complex could save over 1.75 million kilowatt-hours of power in a year. Add in the savings in air conditioning costs, and the increased cost of the more efficient equipment is quickly amortized.
With these considerations, what is the best method for selecting components used in systems being developed today? Until recently, no semiconductor manufacturer had standardized a set of criteria to easily illustrate the efficiency of their components. National Semiconductor is the first to introduce efficiency metrics to provide design engineers an additional tool for selecting the lowest power consuming device. These are called the PowerWise Rating Metrics and can be found on the over 300 PowerWise devices from National. But how are they defined and what advantage do engineers have in using them? Let's take a look at an example.
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