voltage-time-sets-current-change - Electronic Circuits XIII & XIV: Power Supplies and Switching Energy Step by Step

A voltage-time-sets-current-change scan holds the inductance and interval fixed and varies the voltage across three rows, checking that the current ramp delta-I = V * delta-t / L scales with voltage row by row. The arithmetic is exact only for the stated voltages, times, inductances, current changes, and rows in the ideal inductor model. Real circuits add winding resistance, core saturation, parasitics, switching transients, probe/calibration limits, finite precision, and measurement uncertainty.

A constant inductor voltage over a finite interval fixes the current ramp. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

The ramp starts with one fixed inductance

The inductor is 2 H. A constant voltage over a declared interval gives a finite current change.

V=L{\Delta I\over \Delta t}\quad\Rightarrow\quad \Delta I={V\Delta t\over L}

More voltage gives a larger current change

The inductance and interval stay fixed, so the current-change rows scale with applied voltage.

\begin{array}{c|c|c|c}L&V&\Delta t&\Delta I\\2\ \text{H}&2\ \text{V}&1\ \text{s}&1\ \text{A}\\2\ \text{H}&4\ \text{V}&1\ \text{s}&2\ \text{A}\\2\ \text{H}&6\ \text{V}&1\ \text{s}&3\ \text{A}\\\end{array}

Voltage times time sets the inductor current change

The interval is a declared constant-voltage training interval, so the checked ramp is finite and exact.

\Delta I={V\Delta t\over L}=6\ \text{V}\cdot1\ \text{s}/2\ \text{H}=3\ \text{A}