According to the Energy Star website, more than 1 billion external power supplies (ac-to-dc converters) are shipped per year, and the average American family has five to 10 of these components powering devices in their homes. A joint program of the U.S. Environmental Protection Agency and the U.S. Department of Energy, Energy Star has already rated numerous product categories for the ability to operate efficiently and now has these devices in its sight. Environmental labeling, initially pioneered by Germany’s Blue Angel almost 30 years ago, offers industry and trade companies the opportunity to document their environmental competence in a simple and inexpensive way for all to see. These labeling efforts have become a driving force for more efficient products.
There are three types of ac-to-dc power supplies: adapters/external power supplies (EPS), front-end power supplies (FES), and central power supplies (CPS). EPS and FES provide bus voltage to be used as an input to downstream dc-to-dc converters which provide the load voltages. Central power supplies’ output provides direct load voltages. Due to proliferation of portable equipment and emergence of the distributed power, there will be higher growth in EPS and FES. According to Mohan Mankikar, president, Micro-Tech Consultants, a marketing research firm, “The trend for ac-dc power supplies has moved towards providing a source for dc-to-dc converters.” The ac-to-dc converter frequently provides a higher output dc voltage that is distributed within the system. And, there are many different voltages including 48V, 12V and for portable applications, 9V.
For dc-to-dc power sources the situation is more complex. There are four dc-to-dc categories: isolated power supplies or bricks, Voltage Regulator Modules (VRMs), non-isolated point of load (POL), and the newest classification — Voltage Regulator-Down (VRD) supplies used in computers. The VRDs can frequently be created with an integrated circuit and a few extra components. The trend that Mankikar sees in this area is going from power supply strength to semiconductor strength. Supplier expertise for ac-dc converters comes primarily from the Far East. Once the dc voltage exists in the system, semiconductor suppliers form the core for dc-to-dc conversion.
“There are quite a few things going on in the power supply industry pretty dramatic things,” observes Arnold Alderman, president of Anagenesis, a technical marketing firm that focuses on power electronics technologies. “One of the biggest ones is the conversion from analog control to digital control.” From a cost standpoint digital power is becoming competitive with the analog approach. There has been a transition since the mid-90s in the power supply industry with supplies moving from analog control to analog control with digital supervisory activity such as housekeeping. Regarding the possibility of going completely digital, there are two camps says Alderman. One camp insists that digital cannot be cost competitive so its acceptance will be limited. The other side points out the increased capabilities that digital power supplies provide. Alderman says the acceptance will come from the people who design the power systems and the power systems’ architecture.
Alternate Energy Sources: Fuel Cells
Fuel cells continue to make significant progress as an alternate energy/power source. For example, portable fuel cell power systems supplier Jadoo Power Systems Inc. was recently awarded a General Atomics, Space Power Division to develop an advanced fuel canister for use with hydrogen fuel cells. Jadoo’s N-Stor intelligent digital fuel interface already provides power for a number of applications including professional movie cameras.
With its Mobion micro fuel cell technology already replacing batteries as the energy source in some applications, MTI MicroFuel Cells Inc. (MTI Micro), recently announced it achieved an energy density of over 1.3 Watt hours per cc of fuel on a 30-W laboratory test unit. The 30 percent plus increase in fuel efficiency takes MTI Micro a step closer in the development of products for a range of applications targeted for the military market.
The goal is to provide up to 30W of continuous power in a portable, light-weight, power-pack to eliminate the need to carry multiple battery types. This would allow soldiers to use a variety of portable electronic devices such as communication radios, laptops and GPS devices for longer periods of time.