On March 7th, the U.S. Department of Energy issued what may be this year’s most important and far-reaching Notice of Proposed Rulemaking (NOPR). The NOPR, Energy Conservation Standards for Battery Chargers and External Power Supplies, not only presents the first mandatory federal efficiency standards for battery charger systems (BCSs), it also significantly tightens and expands the range of the current minimum efficiency requirements for external power supplies (EPSs). The affected EPSs and BCSs can be found in a wide range of consumer applications and products.
The 470-page NOPR isn’t exactly a quick-read and contains a lot of information, so I intend to discuss this document over the next few blogs. We’ll take a quick look at EPSs in this blog. (For those who want to dive into the NOPR on your own, jump to the end of this blog for a link to download a copy.)
Expanding the EPS scope
The U.S. EPS efficiency standard currently in force (part of the Energy Independence and Security Act 2007 (EISA2007)) addresses efficiency only in single output voltage, AC-DC and AC-AC power supplies with an output power nameplate rating of 250 watts and below, similar to other EPS standards around the globe. The DoE currently refers to these as Class A EPSs. The new proposal contains seven product classifications, as shown in Table 1 below. Class A has been changed to Class B and is focused only on those EPSs that “directly” power a product, regardless of the charge condition of a battery if used in an application that includes a battery. In applications where an EPS can’t power a consumer product without the assistance of the product’s battery, the EPS falls into Product Class N. For low voltage EPSs (output voltage < 6V, output current > 550mA), Product Class C and Product Class E have been added for DC and AC outputs, respectively. Finally, the DoE breaks new ground with Product Classes X and H, regulating efficiency in multiple output power supplies and those delivering > 250 W.
Table 1. Proposed EPS Product Classifications (Source: U.S. DoE March 2012 BCS EPS NOPR)
|
Product Class
|
Product Class Description
|
|
|---|---|---|
| B | DC Output, Basic-Voltage | 2.5 (0-10.25 W) |
| 18 W (10.25-39 W) | ||
| 60 W (39-90 W) | ||
| 120 W (91-250 W) | ||
| C | DC Output, Low-Voltage | |
| D | AC Output, Basic-Voltage | |
| E | AC Output, Low-Voltage | |
| X | Multiple-Voltage | |
| H | High-Power | |
| N | Indirect Operation | |
Comparing the NOPR Limits to the EC Ecodesign, et al.
So, how do the NOPR proposed limits compare with the efficiency regulations in force in other parts of the world? The DoE is proposing raising the efficiency bar for EPS manufacturers, in both active mode average efficiency and no-load power consumption. Since most other standards at this time (including the European Commission’s (EC) Ecodesign Directive (Lot 7) for EPSs) are based on ENERGY STAR’s “retired” EPS program efficiency specs, this could ultimately impact the rest of the world. Table 2 compares the limits for the DoE’s direct operation EPS with the other standards.
Table 2. Comparison of Proposed Energy Conservation Standards for Direct Operation External Power Supplies (Source: U.S. DoE March 2012 BCS EPS NOPR)
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|
Proposed DoE March 2012 NOPR (Direct Operation EPS)
|
EC Ecodesign Tier 2 (2011), ENERGY STAR EPS v2, EC CoC v4, China YD/T 1591-20095
|
||
|---|---|---|---|---|
|
|
Standard Voltage PS3
|
Low Voltage PS3
|
Standard Voltage PS3
|
Low Voltage PS3
|
| Nameplate Output Power (Pno) | Minimum Average Efficiency, Active Mode | Minimum Average Efficiency, Active Mode | Minimum Average Efficiency, Active Mode | Minimum Average Efficiency, Active Mode |
| ≤ 1 W | ≥ 0.5 * Pno + 0.16 | ≥ 0.517 * Pno + 0.087 | ≥ 0.480 * Pno + 0.140 | ≥ 0.497 * Pno + 0.067 |
| > 1 to ≤ 49 W | ≥ 0.071 * Ln( Pno ) - 0.0014 * Pno +0.67 |
≥ 0.0834 * Ln( Pno ) - 0.0014 * Pno + 0.609 |
≥ [0.0626 * Ln (Pno)] + 0.622 |
≥ [0.0750 * Ln (Pno)] + 0.561 |
| > 1 to ≤ 51 W | – | – | ≥ [0.0626 * Ln (Pno)] + 0.622 (EcoDesign only) |
N/A |
| > 49 to ≤ 250 W | ≥ 0.880 | ≥ 0.870 | ≥ 0.870 | ≥ 0.860 |
| > 51 to ≤ 250 W | – | – | ≥ 0.870 (EcoDesign only) | N/A |
| > 250 W | 0.875 | 0.875 | N/A | N/A |
| No-Load Power1,2,4 | No-Load Power2,4 | No-Load Power1,2,4 | No-Load Power2,4 | |
| < 50 W | ≤ 0.100 W | ≤ 0.100 W | ≤ 0.3 W / 0.15 W | ≤0.3 W / 0.15 W |
| ≥ 50 to ≤ 250 W | ≤ 0.210 W | ≤ 0.210 W | ≤ 0.5 W | ≤ 0.5 W |
| > 250 W | ≤ 0.500 W | ≤ 0.500 W | N/A | N/A |
Notes:
- AC-AC is ≤ 0.5 W for all power levels
- CoC and YD/T – No-load spec for mobile handheld battery powered apps = < 0.15 W
- Standard voltage power supply excludes low voltage power supplies which are defined as < 6 volts and ≥ 550 mA
- For Ecodesign, power levels are ≤ 51 watts and > 51 watts
- YD/T standard covers only EPS with USB output of 5 V, 500mA to 1500 mA
Table 3 shows some resulting efficiency limits, assuming some typical output powers. These increased requirements should drive some interesting comments and discussions when the DoE holds their next stakeholder meeting.
Table 3. Comparison of Minimum Efficiency Requirements – U.S. DoE Proposed vs. EC Ecodesign Directive Lot 7
|
Nameplate Output Power (Pno)
|
U.S. DoE March 2012 NOPR
|
EC Ecodesign Directive
|
|---|---|---|
|
|
Active Mode Efficiency (Ave.)
|
Active Mode Efficiency (Ave.)
|
| 1 W (standard voltage) | 66% | 62% |
| 1 W (low voltage) | 60.4% | 56.4% |
| 5 W (standard voltage) | 77.7% | 72.3% |
| 5 W (low voltage) | 73.6% | 68.2% |
| 20 W (standard voltage) | 85.5% | 81% |
| 60 W (standard voltage) | 88.0% | 87.0% |
|
|
No-load power consumption
|
No-load power consumption
|
| < 50 W | ≤ 0.100 W | ≤ 0.3 W / 0.15 W |
| ≥ 50 to ≤ 250 W | ≤ 0.210 W | ≤ 0.5 W |
Fast track to effective date
One additional observation – the DoE appears to be on a fast track to get the EPS standards in effect. Even though the department was late in issuing the NOPR, the original planned effective date hasn’t been pushed out. The effective date for all direct operation EPSs is currently July 1, 2013.
For a copy of the NOPR, go to the U.S. DoE page in the Power Integration’s Green Room. (For those who don’t want to wade through the entire document, a summary of the limits and definitions can be found starting on page 461.)
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