External power supplies: New standards drive new design priorities

Power efficiency becomes central to reducing environment impact worldwide


ue to the ever-increasing impact humans are having on the environment, it is important that our

devices work to counter the adverse effects that can result from everyday life and business. External power supplies (EPSs) have a unique opportunity to positively impact this effort. Contained and operating separately from the devices they power, electric power supplies contribute substantially to total global electricity consumption. Because of this, resolving the inefficiencies of power conversion can add tangible environmental value across the globe, for example cutting energy consumption and reducing CO2 emissions. Competitive value follows as well, with EPS designers empowered to redirect saved kilowatts into different applications. Newer, more eco-friendly systems can differentiate a product, ultimately increasing market share. EPS designers must embrace the regulations and energy conservation initiatives at play and plan for continued evolution of ecological concerns worldwide.

Understanding new and developing standards A number of new, often parallel, regulations are advancing energy conservation in EPS design, formally recognising the relationship between today’s lifestyles and electrically powered devices. Overall, the goal is to ensure the EPS features a high average energy efficiency and minimum no-load power consumption. Level VI standards, regulations developed by the U.S. Department of Energy (DOE), went into effect in 2016. The European Union (EU) followed suit with its Tier 1 and Tier 2 Code of Conduct (CoC) standards, established by the European Commission Joint Research Centre; these standards are currently voluntary and anticipated to become binding in the future.

Decreasing energy consumption via Level VI standards Two key performance criteria are defined by the DOE’s Level VI regulations: no-load

44 May 2019

power consumption and minimum average efficiency limits in active mode. These are measured at 25 per cent, 50 per cent, 75 per cent and full load, and span a broad range of products including: • Single-voltage external AC-DC power supply, basic-voltage (output voltage 6 V) • Single-voltage external AC-DC power supply, low-voltage (output voltage below 6 V) • Single-voltage external AC-AC power supply, basic-voltage (output voltage 6 V) • Single-voltage external AC-AC power supply, low-voltage (output voltage below 6 V) • Multiple-voltage external power supply Table 1 features minimum average

efficiency thresholds and the maximum standby power EPSs falling into the above classes. The DOE’s Level VI legislation is more stringent than previous regulations, incorporating an entirely new category of multiple-voltage EPS options as well as a new output power level threshold of 250W. Table 1 defines a multiple-voltage EPS as ‘an external power supply designed to convert line voltage AC input into more than one simultaneous lower voltage output,’ while the ln(Pout) designation refers to the natural logarithm of an output power. The DOE ruling also differentiates between direct and indirect operation EPSs. For example, direct options are external power supplies capable of operating a consumer product that is not a battery charger, without the assistance of a battery. The majority of EPSs falling into the direct operation category shall comply with the parameters illustrated in Table 1. The new standards (Level VI) apply to direct operation EPSs only, but not all of them have to be compliant as the standards state certain exceptions. An indirect operation EPS cannot

power a consumer product (other than a battery charger) without the assistance of a battery. For example, if an end-use product only functions

Components in Electronics

when drawing power from a battery, the EPS associated with that product is classified as an indirect operation EPS. DOE developed this method to distinguish between direct and indirect

operation EPSs., which requires manufacturers to determine whether an EPS can operate its end-use product once the associated battery has been fully discharged.

Table 1

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