Linear vs Switching Regulators

Problem

A 12 V battery powers a 5 V / 1 A load. Compare a linear regulator vs a switching regulator (assume 88% switching efficiency).

P_{loss} = (12 - 5) \times 1 = 7\,\text{W}

\eta = \frac{5}{12} = 41.7\%

The pass transistor dissipates 7 W as heat. A heatsink is mandatory.

P_{in} = \frac{P_{out}}{\eta} = \frac{5}{0.88} = 5.68\,\text{W}

P_{loss} = 5.68 - 5 = 0.68\,\text{W}

Only 0.68 W lost — the regulator runs cool without a heatsink.

Figure 1. Power loss comparison: linear (red) vs switching (green)

The linear regulator wastes 7 W as heat — needs a heatsink. The switching regulator wastes only 0.68 W — runs cool.