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EPS2U Power Supply Design Guide, V2.1
5.4 AC Line Dropout
STATUS
Required
An AC line dropout is defined to be when the AC input drops to 0 VAC at any phase of the AC line for any length
of time. During an AC dropout of one cycle or less the power supply must meet dynamic voltage regulation
requirements over the rated load. An AC line dropout of one cycle or less shall not cause any tripping of control
signals or protection circuits. If the AC dropout lasts longer than one cycle, the power supply should recover and
meet all turn on requirements. The power supply must meet the AC dropout requirement over rated AC voltages,
frequencies, and output loading conditions. Any dropout of the AC line shall not cause damage to the power
supply.
5.5 AC Line Fuse
STATUS
Required
The power supply shall incorporate one input fuse on the LINE side for input over-current protection to prevent
damage to the power supply and meet product safety requirements. Fuses should be slow blow type or
equivalent to prevent nuisance trips. AC inrush current shall not cause the AC line fuse to blow under any
conditions. All protection circuits in the power supply shall not cause the AC fuse to blow unless a component in
the power supply has failed. This includes DC output load short conditions.
5.6 AC Inrush
STATUS
Required
The power supply must meet inrush requirements for any rated AC voltage, during turn on at any phase of AC
voltage, during a single cycle AC dropout condition, during repetitive ON/OFF cycling of AC, and over the
specified temperature range (T
op
). The peak inrush current shall be less than the ratings of its critical components
(including input fuse, bulk rectifiers, and surge limiting device).
STATUS
Recommended
An additional inrush current limit is recommended for some system applications that require multiple systems on a
single AC circuit. AC line inrush current shall not exceed 40 A peak for one-quarter of the AC cycle, after which,
the input current should be no more than the specified maximum input current from Table 2.
5.7 AC Line Transient Specification
STATUS
Recommended
AC line transient conditions shall be defined as “sag” and “surge” conditions. Sag conditions (also referred to as
“brownout” conditions) will be defined as the AC line voltage dropping below nominal voltage. Surge conditions
will be defined as the AC line voltage rising above nominal voltage.
The power supply shall meet the requirements under the following AC line sag and surge conditions.
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