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 below table.
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 Test Plan (#338448).