SL12 8R003-A

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Inrush Current Limiters (ICLs) are devices that limit the peak current of an electrical system on power-up. SL12 8R003-A is a device that belongs to this group. This application note explains its field of application and its working principle.

SL12 8R003-A is typically used in DC power supply circuits to prevent large inrush current into the system transformer due to sudden energization of the input capacitor. The device is a monolithic structure integrated with high burnout voltage resettable fuse, a resistor, and several thermal disconnect circuits. Its fast response and excellent protection characteristics effectively detect and interrupt surge currents. High safety and reliability are also ensured because the device’s overload protection level is set below the rated load current of the system voltage.

SL12 8R003-A’s working principle is simple and effective. A small surface mount resistor is included to limit the current at startup. This resistor is connected in series with the main input capacitor on the power supply board. When power is applied, the resistor will limit the amount of current drawn by the capacitor. Since the resistor\'s current rating is high enough to create a high voltage drop across it, the voltage across the power supply\'s input capacitor will also remain relatively low which provides protection from inrush current. However, if the resistor fails, then the capacitor can be damaged by the large inrush current.

As an additional layer of protection, the SL12 8R003-A is equipped with a thermal disconnect device. This device will detect when the resistor’s resistance has exceeded the safe current rating and will essentially shut down the power supply until the resistor’s heat has dissipated. This will protect the power supply from overloading and potential damage.

SL12 8R003-A is an excellent solution for applications where inrush current protection is needed. It is important to note that it may not perform optimally in applications where the circuit exceeds the suggested tolerance range of the device or where the circuit requires minimum start-up current levels. Before using the SL12 8R003-A, users should always consult with the manufacturer’s documentation to make sure the device is suitable for the intended application.

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