Energy Star is a joint program established by the US Environmental Protection Agency and the US Department of Energy. Its goal is to aid in enforcing the long-term protection of the environment through encouraging the development of more energy-efficient electronic products and practices. The organisation clams that in the last year alone it has helped the North American populace to avoid greenhouse gas emissions equivalent to those from 27 million cars, and taking $16 billion off their utility bills in the process. With the new standard, power factor correction requirements have been added for power supplies with input power levels of greater than 100W, and the no-load requirements for AC/DC and AC/AC PSUs are now separated. Although compliance will still be on a strictly voluntary basis, there are increasing pressures for OEMs to comply with the guidelines that Energy Star sets, and they are looking to their semiconductor partners to facilitate this.
I spoke with Giuseppe Gattavari, director of the Off-Line Converter Business Unit at STMicroelectronics. "This standard is going to give OEMs serious challenges to overcome. It will be difficult, for sure, but certainly not impossible," he informs. "The efficiency levels at low loads (like 10 and 20%) are going to be particularly tough to achieve, system designers will look to use more advanced topologies like soft switching and improved frequency reduction techniques as a result."
Silicon Valley's Power Integrations has addressed the issues raised in a rather innovative way. Its LinkSwitch-II family of AC/DC switched-mode power conversion ICs offers high accuracy primary-side control. It eliminates the need for all secondary-side constant-voltage/constant-current (CV/CC) and control-loop compensation circuitry, thereby simplifying the system design and reducing the component count. The aim is to enable consumer electronics OEMS to meet these hard-hitting active mode efficiency and no-load power consumption (the power consumed from the wall when disconnected from the appliance) regulations. By only having a single circuit rather than two, the need for opto-couplers to provide electrical isolation is dispensed with. LinkSwitch-II ICs can also help compensate for the voltage drop across the cable. Output CV/CC tolerances of ±5% and ±10%, respectively, are achieved over temperatures ranging from 0 to 100°C.
It succeeds in attaining Energy Star 2.0 compliance by achieving average efficiency levels of up to 75% at 25, 50, 75 and 100% load levels across the entire 115 to 230VAC input range. It uses primary side regulation to accurately control the output current and voltage, eliminating the secondary feedback and compensation components. The LinkSwitch-II devices also offer accurate cable drop compensation, which significantly reduces the cost of the output cable by minimising its copper content (which is an increasingly expensive material to procure), without sacrificing output performance. It also requires a smaller transformer, using less copper and ferrite core materials. Lack of secondary feedback sensing components helps to dramatically reduce the no-load consumption to negligible levels.
But are the guidelines actually aggressive enough? Richard Fassler, manager of Power Integrations' energy efficiency programs, feels that they have certainly played an important part in improving the efficiency of many consumer products, stating, "If you look at where the industry was just five years ago, there were a lot of inefficient linear transformer-based power supplies around that have now been replaced by switched mode designs, so we have participated in a rapid and substantial change in power architectures."
Highly efficient power supply design has now become a vital part of system development – it is no longer just a purely functional affair. It has now become an area for differentiation. The Energy Star program has done a lot to build industry/activist consensus for standby, no load consumption and active mode efficiency in power supply designs across a broad range of energy-using products.
"California's mandatory EPS standard, published a couple of years ago and based on the original Energy Star EPS specification, gained widespread acceptance in the US. With the state representing such a huge economy in its own right, other states followed suit, ultimately resulting in a federal standard EISA2007, which mandates similar efficiency and no-load requirements for EPSs for the entire country. The move to using switched mode supplies has also enabled adapters and power-supplies in many consumer products that operate on all worldwide mains voltages, allowing manufacturers to design cost-effective EPSs to the tightest worldwide standards and specifications, something that will be beneficial once the new Energy Star spec becomes effective later this year," Fassler noted.
Aiming primarily at converter systems ranging from 50 to 150W, the Zetex ZXGD3101 rectifier controller from Diodes Incorporated looks to enable designers to replace out-dated Schottky diode components with surface-mount MOSFETs to achieve power higher efficiency, less heat generation and a reduction in overall power supply size and weight in the process. It accurately senses the point at which secondary current reaches zero, and thus ensures that each MOSFET performs the same function as the diode it replaced while significantly improving efficiency levels. In a 60W laptop adapter, the company claims that losses can be reduced by around 20%, thanks to an efficiency level of 87% and a standby power drain of only 0.5W. Diodes' Marketing Manager Mike Townson confirms, "Energy Star 2.0 is going to cause major upheavals for power adaptor and power supply manufacturers. It means they will have to totally change the topology used in their system designs. This can't be tackled by some minor incremental improvement in the components utilised, it needs a whole new methodology."
The MIPAQ products introduced by German IDM Infineon Technologies are designed to be used in uninterruptible power supply units, industrial drives and photovoltaic power systems, and offer a very high level of system integration. Based on the company's IGBT4 power architecture, these modules provide about 20% lower switching losses than the previous generation of solutions and in addition offer higher power cycling capabilities. These 1200V modules feature an IGBT six-pack configuration and are offered in current rating levels from 50 to 200A.
CamSemi's latest 6W mixed signal controller device, the C2471, is designed to enable the rapid development of simple, low cost, switched mode power supplies (SMPS) for low power consumer applications. It meets the demands of the FCC 68 standard for low power telecommunication equipment as well as Energy Star EPS 2.0, but without the need to employ costly, complex filtering circuitry. The controller is based on a patented resonant discontinuous forward converter (RDFC) topology that maintains virtually EMI (electromagnetic interference) free resonant switching over the full load variation, and removes the need for fast, hard-edged switching that produces considerable emitted and conducted noise. The device delivers 82% average power efficiency levels, and its no-load power is only 160mW. It comes in a compact SOT23-6 surface mount package.
In addition to the new Energy Star directives, the European Union's Code of Conduct (CoC) working group has issued Version 3 updates to the EPS CoC. This will take effect on January 1, 2009. Although adhering to Energy Star 2.0 and the EU CoC are likely to result in additional costs for manufacturers, Gattavari at STMicroelectronics points out that there will be considerable benefits too. The Franco-Italian semiconductor giant has been an active member in the development of both the Energy Star and the EU CoC standards. He states, "The possibility of producing smaller form factor designs should not be underestimated, as it is becoming an important way of gaining a competitive advantage. Then of course there is the increasing cost of the electricity, which is certain to effect how consumers chose which electronics goods to buy. If a manufacturer can show that their products attain higher power efficiency levels than those of its rivals, it will be rewarded." There is also the reliability aspect, as Gattavari explains: "The fact that these designs will be capable of higher efficiencies means they won't be exposed to as much heat, and this will reduce the risk of failure."
However, even if these European and US guidelines are fully respected by electronics manufacturers serving the Western market, and the reductions in energy consumption that these bodies are striving for are actually accomplished, their effect may still only be negligible unless similar efforts are made elsewhere in the world. The increasingly capacious trade in electronics goods in the developing nations in Asia is certain to be where this battle will be either won or lost. The huge unit volumes involved mean that if Far Eastern manufacturers looking simply to exploit the ever growing local market choose to ignore current concerns on energy consumption and concentrate on keeping prices low, then any improvements made here in the West will basically count for naught. With the balance of power now swaying towards China and India, will their almost countless consumers effectively swallow up any anything that Energy Star manages to achieve? If so, does some sort of worldwide legislation need to be put in place to combat this? "I believe that this standard will be taken seriously," states an optimistic Townson, "as on the whole, it is in the interest of the OEMs.
"Though they need to be willing to make a tradeoff between cost and performance," Townson continues, "the additional advantages that can be realised, in the forms of reduced operating temperature and improved reliability, are going to help soften the blow. It will mean that they can produce more compact, sleeker adaptors to go with their goods. There will be companies that will go for higher benchmarks, and there will be those who are concerned only with cost. OEMs in developing countries that are only looking to serve the indigenous market will be driven primarily by cost issues, but with time the need to compete on performance and size will mean that they will be drawn towards the specs defined by Energy Star." He points out, "There isn't really any authority to impose a global directive, but I think that the industry will to some extent be able to police itself here."
Richard Fassler - Power Integrations
Mike Townson - Diodes Inc.
Giuseppe Gattavari - STMicroelectronics
The Infineon MIPAQ IGBT module family.
The Zetex ZXGD3101 rectifier controller IC from Diodes Incorporated.
The LinkSwitch-II power conversion chip from Power Integrations.
