In DC power systems, reverse current is a hidden threat—especially on 24V rails used in industrial or automation setups. If two supplies are paralleled or a load backfeeds power, current can flow in the wrong direction, damaging sensitive power sources or components.

The Problem :

Imagine connecting a backup battery or secondary power supply to a 24V line. If the main supply shuts off, current could flow backward into it, causing overheating or failure.

The Solution :

Use a P-channel MOSFET or Schottky diode for reverse current protection. A P-MOSFET with its source to the power rail and drain to the load allows current only when the gate is pulled low—blocking reverse flow.

Practical Example :

Let’s say you use a P-MOSFET rated for 30V and 20A. Add a gate pull-down resistor of 10kΩ to ensure it turns on when needed. For faster switching, add a 100Ω gate resistor to limit inrush.

Sample Calculation  :

If the load draws 5A and your MOSFET’s Rds(on) is 0.05Ω,

Power loss = I² × R = 5² × 0.05 = 1.25W,

which is much lower than a diode’s drop (≈0.7V × 5A = 3.5W).

Product Suggestions :

• MOSFET

• Schottky diode

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