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TFX12V Power Supply Design Guide
Thin Form Factor with 12 V Connector
Version 2.0
10
2 Electrical
The following electrical requirements must be met over the environmental ranges as defined in Section 5
(unless otherwise noted).
2.1 AC Input
Table 1, 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 auto-ranging. 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 1. AC Input Line Requirements
Parameter Minimum Nominal* Maximum 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
*Note: Nominal voltages for test purposes are considered to be within ±1.0 V of nominal.
2.1.1 Input Over Current Protection
The power supply shall incorporate primary fusing 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.
1
2.1.2 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.
2.1.3 Input Under Voltage
The power supply shall contain protection circuitry such that the application of an input voltage below the
minimum specified in Section 2.1, Table 1, shall not cause damage to the power supply.
1
For Denmark and Switzerland international safety requirements, if the internal over current protective devices exceed 8A
for Denmark and 10A for Switzerland, then the power supply must pass international safety testing to EN 60950 using a
maximum 16A over-current protected branch circuit, and this 16A (time delay fuse) branch circuit protector must not open
during power supply abnormal operation (output short circuit and component fault) testing.