When designing power systems with multiple SMPS units, one common challenge is load sharing—ensuring each power supply contributes equally. If one SMPS does all the work, it overheats and fails early, while others sit idle. Smart load sharing boosts efficiency, extends life, and keeps things cool.

The Problem: Uneven Load Distribution

Without proper load sharing, even identical SMPS units may not share current evenly due to slight output voltage mismatches. This results in one overloaded SMPS, while others operate under capacity or idle.

The Solution: Passive or Active Load Sharing

The easiest method is passive sharing, where small-value ballast resistors (e.g., 0.1Ω) are added to each SMPS output. This helps balance the current by absorbing small voltage differences. For more precision, active load sharing circuits using op-amps or dedicated ICs monitor and adjust current flow in real-time.

Practical Example: Dual 5V 10A SMPS Setup

Let’s say you use two 5V/10A SMPS units in parallel. If one outputs 5.1V and the other 5.0V, the higher one will carry most of the load. By adding a 0.1Ω resistor in series with each output, the load distributes more evenly, reducing the burden on a single unit.

Sample Calculation :

If each resistor drops 0.1V at 1A:

R=IV​=1A0.1V​=0.1Ω

Product Suggestion: Resistors & Power MOSFETs

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