Circuit Protection of DC Line Power Supplies
 
Design Notes:
Protection Application:
For products that include an external AC adapter, a DC voltage (typically in the range of 5VDC to 18VDC) will be supplied. The electrical threats include lightning surges, ESD and overcurrent conditions (short circuit or overload).
Solution Description:
As shown at the left, a fuse or PTC can be used for short circuit and overload current conditions. For surge and ESD protection, an MOV (e.g. LA series) or TVS diode (e.g. P4KE or P4SMA series) can be used.
Companion Solutions:
Note that the magnitude of the surge transient should be understood as this can point to alternative solutions. For example, if more severe surges are expected, then C-III or UltraMOV varistors or higher-rated diodes (e.g. 600W, 1,500W) can be selected. If the only threat is expected to be ESD, then multilayer chip varistors can be selected.
Regulatory Issues:
If ESD is a concern, the IEC 61000-4-2 can be consulted to find information on the test method and transient waveform that should be used.
Unique Features:Does not apply.
Application Warnings:Does not apply.
Solutions
Resettable PTCs
14D Line Voltage Operation Radial Leaded Varistor
P4KE 400W Axial Leaded Transient Voltage Supressors
P4SMA 400W Surface Mount Transient Voltage (TVS) Diode - P4SMA

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