Intel ATX 3.0, Design Manual

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Electrical
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to meet a 240VA Energy Hazard Safety Requirement, most power supplies are not
currently designed to meet this requirement.
4.5.8 Overall Power Supply Efficiency Levels
The efficiency of the power supply should be tested at nominal input voltage of
115 VAC input and 230 VAC input, under the load conditions defined in the
Generalized Test Protocol for Calculating the Energy Efficiency of Internal Ac-Dc and
Dc-Dc Power Supplies document. This document defines how to determine full load
criteria based on the label of each rail of the power supply. The loading condition for
testing efficiency represents fully loaded systems, typical (50%) loaded systems, and
light (20%) loaded systems.
The Efficiency requirements listed below are applicable to AC Input voltage of 115V.
Table 4-13: Efficiency versus Load Minimum Requirements
Loading
Full Load
(100%)
Typical
Load
(50%)
Light
Load
(20%)
REQUIRED Minimum Efficiency 70% 72% 65%
Low Load Efficiency
Computers have decreased Idle power greatly since 2005, to where PSU loss is a big
concern for overall AC power of a computer in Idle Mode. The lowest DC load for
computers at this Idle Mode is determined to be 10 Watts for mainstream computers
and could go lower. Computers with PSU larger than 500 Watts are also expected to
have more components and therefore the Idle Mode will be at a higher DC Load. A
PSU above 500 Watts will use the Low Load Efficiency set at the 2% level. The Low
Load Efficiency requirements are shown in Table 4-14 : Low Load Efficiency
Requirements.
Table 4-14: Low Load Efficiency Requirements
Low Load Efficiency 10W / 2%
Required 60%
Recommended 70%
The 10-Watt load conditions are defined in the Desktop Platform Form Factors Power
Supply Test Plan (# 338448 ).