ATX/ATX12V Power Supply Design Guide
Version 1.1
Page 33
8. Safety
The following subsections outline sample product regulations requirements for a typical
power supply. Actual requirements will depend on the design, product end use, target
geography, and other variables. Consult your company’s Product Safety and Regulations
department for more details.
8.1. North America
The power supply must be certified by an NRTL (Nationally Recognized Testing
Laboratory) for use in the USA and Canada under the following conditions:
•
The supply must be Recognized for use in Information Technology Equipment
including Electrical Business Equipment per UL 1950 / CAN/CSA C22.2 No. 950-95,
3
rd
edition, without D3 deviations. The certification must include external enclosure
testing for the AC receptacle side of the power supply (see Figures 4 and 5).
•
The supply must have a full complement of tests conducted as part of the certification,
such as input current, leakage current, hi-pot, temperature, energy discharge test,
transformer output characterization test (open-circuit voltage, short-circuit current, and
maximum VA output), and abnormal testing (to include stalled-fan tests and voltage-
select–switch mismatch).
•
The enclosure must meet fire enclosure mechanical test requirements per clauses 2.9.1
and 4.2 of the above-mentioned standard.
Production hi-pot testing must be included as a part of the certification and indicated as
such in the certification report.
There must not be unusual or difficult conditions of acceptability such as mandatory
additional cooling or power derating. The insulation system shall not have temperatures
exceeding their rating when tested in the end product.
The certification mark shall be marked on each power supply.
The power supply must be evaluated for operator-accessible secondary outputs (reinforced
insulation) that meet the requirements for SELV and do not exceed 240 VA under any
condition of loading.
The proper polarity between the AC input receptacle and any printed wiring boards
connections must be maintained (that is, brown=line, blue=neutral, green=earth/chassis).
Failure of any single component in the fan-speed control circuit shall not cause the internal
component temperatures to exceed the abnormal fault condition temperatures per IEC
60950.
