Protecting 24V Rails from Reverse Current Damage
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).
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