A circuit protection scheme for DC power supply Design Description:
Protection application:
For a product equipped with an external AC power adapter, a DC voltage (usually 5VDC to 18VDC) can be used for power supply. Electrical threats include lightning surge, electrostatic discharge and overcurrent (short circuit or overload).
The solution shows that:
As shown on the left, the fuse or PTC can be used for short-circuit and overload current situation. For surge and ESD protection, pressure sensitive resistors (such as LA Series) or transient suppression diodes (such as P4KE or P4SMA Series) can be used.
Supporting solutions:
Note that when alternative solutions are considered, the magnitude of the transient surge should be taken into account. For example, if the surge current is too large, a C-III or UltraMOV varistor, or a higher power diode (such as 600W, 1500W), can be selected. If the only threat comes from electrostatic discharge, the multilayer chip varistor can be selected.
Regulatory issues:
If the problem of electrostatic discharge is considered, IEC 61000-4-2 can be consulted to obtain the test method and the information that should be used for transient waveform.
Characteristics: not applicable.
Application warning: not applicable.