FAQ01858 of Power Supplies FAQ

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

Equations:

Internal loss (W)

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