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Power Supply Topic: Estimate Amount of Heat Produced

FAQ No. FAQ01858

Question

What is the best way to estimate the amount of heat produced by the Power Supply?

Answer

The Power Supply's internal loss becomes heat energy (internal loss = heat produced).

Equations:

Internal loss (W)

= Effective input power - Output power

= Output power/Efficiency - Output power

Note: Reducing the load rate is an effective way to reduce the amount of heat produced.

Example Calculating the Heat Produced by a 100-W S82K Switch Mode Power Supply

Power rate: 80%

Output power: 24 V × 4.2 A = 100.8 W
Effective input power: Output power/Efficiency = 100.8 W/80% = 126 W

Internal loss (heat produced): 126 W - 100.8 W = 25.2 W
To convert the internal loss to calories:

By Joule's law, 1 W = 0.24 cal/s,

so 25.2 W = 25.2 × 0.24 cal/s = 6.05 cal/s

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