Regulator Input Waste Cross-Scan - Electronic Circuits XIII: Power, Rectification, and Regulation Step by Step

Extra input voltage becomes waste power at fixed load current. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Linear-regulator waste is input minus output times load current

The checked source uses seven volts in, five volts out, and two amps. Input power splits into ten watts of load power plus four watts of waste.

7\ \text{V}\cdot2\ \text{A}=10\ \text{W}+4\ \text{W}

Extra input voltage increases waste while load power stays fixed

The output voltage and load current stay fixed. Raising input voltage raises input power and waste power, not load power.

\begin{array}{c|c|c|c}V_{\text{in}}&P_{\text{in}}&P_{\text{load}}&P_{\text{waste}}\\6\ \text{V}&12\ \text{W}&10\ \text{W}&2\ \text{W}\\7\ \text{V}&14\ \text{W}&10\ \text{W}&4\ \text{W}\\8\ \text{V}&16\ \text{W}&10\ \text{W}&6\ \text{W}\\\end{array}