Moving toward the most efficient use of power

Moving toward the most efficient use of power

Improvements in energy efficiency and power conversion play an important role in reducing global energy consumption

BY JEFF UDEN
Newark
Chicago, IL
http://www.newark.com

The increasing importance of being energy efficient from an environmental standpoint, coupled with rising energy costs, is making efficiency one of the headline specifications for commonly used power management devices such as regulators, ac/dc power supplies, and dc/dc converters. The emergence of voluntary and mandatory regulations concerned with raising the power-efficiency standards in our country underscores this raised profile and focus.

Minimizing power consumption and maximizing efficiency has always had a relatively high degree of importance in industrial electronics equipment, particularly in fixed, mains-powered products where energy costs constitute a significant element of overall expenditure incurred by a business.

Now, as the general public becomes more environmentally conscious, in terms of how the human race is impacting the planet and consuming natural resources, the spotlight is also falling on the energy efficiency of consumer electronics. The price volatility of domestic energy supplies is, you might say, just adding fuel to the fire!

Minimizing power consumption and efficient power management are also important in battery-powered products. Unfortunately, battery technology has not really advanced in the same prolific way as other areas of electronics, and so, to the designer’s displeasure, battery packs often still make up a significant portion of the overall weight and size of their portable products. Furthermore, long duty cycles are an important selling point for portable products, so getting the most from the battery is of major importance to designers.

The power sector of the electronics industry has been asked to produce devices and modules that provide power management with the utmost efficiency. At a system level, it is also important that end-product designers use energy-efficient architectures.

Strong technical advances in the power electronics sector in recent years have helped include higher efficiency in specification improvements. The scene is set for this to continue with significant amounts of inherent industry knowledge and new technology. This is being galvanized by new federal legislation and the voluntary Energy Star program.

System-level design for maximum efficiency

Although the stand-alone efficiency of a product’s power supply, conversion, or regulation element is very important, it is also important for designers to minimize losses and maximize efficiency of the overall product. Different system architectures can have a significant bearing on overall efficiency, so it is key for the designer to make the right choices.

Early collaboration, either directly with the power product manufacturers or with distributors able to provide technical guidance, can help ensure that the best power management choices are made. This approach can often mean that standard products rather than more expensive, often less efficient, custom or modified-standard modules may be specified.

A general point that should also be considered is that higher-cost power components (assuming this correlates with higher quality) will often lead to an overall more economical design. This is because better-quality, more-efficient components generate less waste energy and therefore less heat needs to be dissipated. The management of excessive heat can mean that anything from heat sinks to power-hungry cooling fans may be needed.

Module and device-level efficiency

Companies such as Powerex are using the latest semiconductor technologies plus a host of other innovative features and processes in their latest power supplies, dc/dc converters, and other power management products.

Fig. 1. Products like the Powerex IGBT use cutting-edge semiconductor technologies for power products.

Example technologies include multilayer heavy copper PCBs, synchronous rectifier topologies, and planar magnetics. These all lead to increased efficiency and higher power density and support feature-laden products in small footprint packages.

The link between small-form-factor design and higher efficiencies is strong, but without careful design, modules with high component densities can be more prone to thermal issues. This potential problem needs to be managed carefully so that the good work done improving efficiency and power consumption at the module level is not undone by a necessity to consider additional thermal management.

Quoting efficiency at load

For comparison, the efficiency of power management products is usually quoted at full load. However, most industrial and consumer electronic equipment actually spends very little time in this state. Efficiency at other loads is equally if not more important. The different load conditions are:

Active mode . This can be defined as the full operational state of the equipment being powered, but is not usually 100% of the power supply’s rated load.Sleep mode . A lower power state than active but one from where the equipment can quickly respond to inputs. Automated sleep modes have become a common feature of power supplies and give significant energy savings.Standby mode . From an environmental standpoint, much industrial and consumer electronics equipment unnecessarily spends most of its life in this state. Although not active, a small amount of power is still being drawn. Various tests and studies conducted around the world suggest that consumer appliances in standby mode use approximately 5% of all residential electricity used.“Hard-off” mode : In this state a switch interrupts power to the front of the power supply so energy consumption is zero.

Voluntary and mandatory power regulations

As part of the Energy Independence and Security Act of 2007, mandatory efficiency levels have been established for external power supplies (EPS) that supersede any other recent regulations on the state level, most notably in California. The effective date for this legislation was July 2008. These federal levels are considered to be minimum compliance levels, and mirror existing standards already set out by California and Energy Star.

California and Energy Star are expected to tighten their current standards for EPS later this year. The voluntary Energy Star program, which was established in 1992 by the EPA and the Department of Energy, has finalized the specifications for EPS Version 2.0, which will require as much as 87% average active-mode efficiency, up from 80% from that mandated in its Version 1.1. Taking effect November 1, Version 2.0’s other key differentiations include:

1. Reduced no-load power max limits.

2. Power factor correction requirement added for power supplies with input power ≥ 100 W.

3. No-load requirements for ac/dc and ac/ac are separated.

While voluntary, Energy Star is now such a powerful consumer brand, many manufacturers follow it as if it were law. It also serves as the basic specification for many state and even country regulations.

If a company meets Energy Star regulations, especially its Version 2.0, it is likely to meet international standards, which are typically voluntary in nature. Two examples are the China Energy Conservation Project and the European Code of Conduct.

In July 2007, the California Energy Commission made mandatory what were essentially Energy Star’s voluntary regulations. More stringent regulations are expected to be passed by the state this summer.

For more on power efficiency, visit http://www2.electronicproducts.com/Power.aspx.