ATX/ATX12V Power Supply Design Guide
Version 1.1
Page 9
3. Electrical
The electrical requirements that follow are to be met over the environmental ranges
specified in Section 5 unless otherwise noted.
3.1. AC Input
Table 2 lists AC input voltage and frequency requirements for continuous operation. The
power supply shall be capable of supplying full-rated output power over two input voltage
ranges rated 100-127 VAC and 200-240 VAC rms nominal. The correct input range for
use in a given environment may be either switch-selectable or autoranging. The power
supply shall automatically recover from AC power loss. The power supply must be able to
start up under peak loading at 90 VAC.
Table 2. AC Input Line Requirements
Parameter
Min.
Nom.
(1)
Max.
Unit
V
in
(115 VAC)
90
115
135
VAC
rms
V
in
(230 VAC)
180
230
265
VAC
rms
V
in
Frequency
47
--
63
Hz
(1)
Nominal voltages for test purposes are considered to be within ±1.0 V of nominal.
3.1.1. Input Overcurrent Protection
The power supply shall incorporate primary fusing for input overcurrent 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.
3.1.2. Inrush Current Limiting
Maximum inrush current from power-on (with power on at any point on the AC sine) and
including, but not limited to, three line cycles, shall be limited to a level below the surge
rating of the input line cord, AC switch if present, bridge rectifier, fuse, and EMI filter
components. Repetitive ON/OFF cycling of the AC input voltage should not damage the
power supply or cause the input fuse to blow.
3.1.3. Input Undervoltage
The power supply shall contain protection circuitry such that the application of an input
voltage below the minimum specified in Section 3.1, Table 2, shall not cause damage to the
power supply.
