Don’t ignore zero standby for effective power reduction
An important trend in power management, often overlooked, is standby power minimization in consumer products, appliances, portable electronics and computer systems. It may be thought that the standby power consumption of electronic equipment is trivial compared with active power consumption.
However, this is far from the truth. Several studies have shown the total energy consumed by electronic equipment and their power adapters while in standby or under no-load is very significant.
According to the U.S. Department of Energy, the total amount of electricity that flows through internal power supplies and external power adapters is nearly 470 billion kWh per year. In the typical household, electricity consumption derives from a large number of appliances, each with its own power supply (e.g. TVs, computers, video players, cellphones etc.).
Most appliances are left permanently plugged into the mains and spend a large proportion of the day on standby or, in the case of cellphone chargers, left plugged into the mains while the phone is elsewhere.
The Lawrence Berkeley National Lab estimates that the waste in electricity resulting from standby and no-load consumption costs U.S. households over $5 billion each year; 5 to 15% of household electricity consumption worldwide is wasted in standby mode (International Energy Agency).
There are clearly enormous benefits to be gained by reducing this waste to as close to zero as possible. Regulatory authorities around the world have not been idle in this respect, and standards have been and continue to be progressively tightened. As an example, for TV receivers many programs including Energy Star and EU Eco-Label now mandate a maximum standby consumption of 1W.
However, it is not the regulatory authorities that are leading the pace. In many brand name consumer product companies, managers are taking a serious view of global energy consumption. Many are demanding power consumption characteristics significantly better than the government- mandated specifications require.
For example, several major OEMs producing TVs and monitors have set a de-facto standard of 100mW maximum standby consumption—10 times lower than the national requirement.
Following a study by Nokia, which found that up to two-thirds of energy consumed by cellphones was wasted by chargers left plugged in, the world’s top cellphone manufacturers (Nokia, Samsung, Sony Ericsson, Motorola and LG Electronics) and the European Commission Integrated Policy Program produced a star rating system for chargers (Table 1 below).
Table 1: Star rating system for cellphone chargers were introduced in November 2008.
You would be forgiven for taking the view that OEMs may be cynically exploiting green issues to gain a marketing advantage. But these OEMs seem to make little or no mention of this in their product promotion. They focus instead on the more traditional user features and the value of their products.
The issues of ultra-low standby consumption are something worked on quietly between their developers and the suppliers of power supply components. One should conclude there is a genuine commitment to drive down energy consumption within the electronics industry and certainly among the major OEMs.
They are making the change because it is the right thing to do. It also helps that reducing standby power is really a matter of careful design and appropriate power IC choice. It costs little more than the will to change and an innovative attitude to have green standby performance.
Energy efficiency measures do make a difference. Dr. Arthur Rosenfeld, now retired, was a long-serving Commissioner to the California Energy Commission and a tireless campaigner for of energy efficiency. California’s low electricity per capita growth since 1973 (Figure 1, below) has been largely credited to him and has been dubbed the Rosenfeld Effect. The Rosenfeld Effect is the empirical fact that electricity use per capita in California has been almost flat from 1973 to 2006, whereas use in the U.S. has gone up 50 percent.
Figure 1: Energy efficiency measures do make a difference (Source: California Energy Commission 2007). [To view larger image, click here]
Achieving ultra-low standby or no-load consumption is not a trivial task, and considerable attention to detail is required. Losses in EMI circuits, decisions related to startup time, transient response, and other design trade-offs mean that care must be taken in external component choices, not just the IC.
The ultimate in standby power consumption is of course zero. We are now seeing products announced that achieve this. VoltStar Technologies Inc. of Illinois produces a charger for cellphones and other portable devices that switches to zero consumption when charging is complete.
AT&T has announced a similar product, the ZERO Charger. The challenge now is to achieve near-zero standby consumption for all electronic systems, not just chargers, without any cost penalty or compromise in user convenience, to take the ultimate step in standby power.
(Doug Bailey is vice president of marketing at Power Integrations, Inc.)