ATX12V Power Supply Design Guide
Version 2.0
3.2.4. Power Limit / Hazardous Energy Levels
Under normal or overload conditions, no output shall continuously provide 240 VA under any conditions of load including output short circuit, per the requirement of UL 1950/CSA 950 / EN 60950/IEC 950.
3.2.5. Efficiency
3.2.5.1. General
The power supply required minimum is 70% efficient under “Full” load, 70% under
“typical” load, and 60% in a “light” load or idle condition. The efficiency of the power supply should be tested at nominal input voltage of 115VAC input and/or 230VAC input, under the load conditions defined in Table 7 and Table 8, and under the temperature and operating conditions defined in Section 5. The loading condition for testing efficiency shown in Table 8 represents a fully loaded system, a ~50% (typical) loaded system, and a ~20% (light) loaded system.
Table 7. Minimum Efficiency Vs Load
| Loading | Full load | Typical load |
| Required Minimum Efficiency |
|
|
| 70% | 70% | |
|
|
|
|
| Recommended Minimum Efficiency |
|
|
| 75% | 80% | |
|
|
|
|
Light load
60%
68%
17