Closed-Loop Buck Converter

Power electronics

A synchronous step-down converter with a continuous-time $L$ – $C$ state solver and switching-ripple reconstruction. Sweep duty cycle, source voltage, load, inductance, capacitance, and carrier frequency; the laboratory identifies conduction mode, efficiency, ripple, and transient settling in real time.

Live circuit continuous conduction, 7.50 V out

Drag a value tag to change that part. Click a wire to clip a probe on.

Oscilloscope

A switch node PWM 48 % at 120 kHz
B i_L 1.25 A avg, 0.89 A p-p

2.5 µs/div, three switching periods

Conduction regime CCM inductor current stays above zero

Readouts

V_{\mathrm{out}}=\htmlData{math-slot=output}{\mathtt{00.000}}\,\mathrm V\quad V_{\mathrm{ideal}}=\htmlData{math-slot=ideal}{\mathtt{00.00}}\,\mathrm V

I_{\mathrm{load}}=\htmlData{math-slot=load}{\mathtt{0.000}}\,\mathrm A\quad i_L=\htmlData{math-slot=inductor}{\mathtt{0.000}}\,\mathrm A

\Delta i_L=\htmlData{math-slot=value}{\mathtt{0.000}}\,\mathrm{A_{pp}}

\Delta v_o=\htmlData{math-slot=value}{\mathtt{00.0}}\,\mathrm{mV_{pp}}

\eta_{\mathrm{est}}=\htmlData{math-slot=value}{\mathtt{00.0}}\%

Causal signal trace paused

Sample demand The controller compares feedback against the regulation target.

t_{\mathrm{stage}}=\htmlData{math-slot=value}{\mathtt{0.00}}\,\mathrm{s}

Step 1 / 5 Sample demand

Notebook: 12 parts and 15 wires, modelled as continuous-time averaged state space

Recommended lab 6 of 18

Predict averaged buck-converter output and recognize conduction-mode boundaries.

Builds on: Dynamic RC Low-Pass Filter

Predict, then test

In continuous conduction, increase $D$ while $V_{in}$ stays fixed. What should $v_o$ do?

Commit before the explanation appears. This is a prediction, not a quiz score.

Governing model

\dot i_L = \dfrac{D V_{in}-v_o}{L},\quad \dot v_o = \dfrac{i_L-v_o/R}{C}

Parts

PWM feedback controller
PMOS high-side switch
Schottky freewheel diode
$L$ – $C$ output network

Limits of the model

$V_{in}: 5$ – $36\ \mathrm V$
$f_{sw}: 20$ – $500\ \mathrm{kHz}$
CCM / BCM / DCM classification

Diagnosis challenge The fault is hidden. Work it out from the changed outputs first.

Notebook: 12 parts and 15 wires, modelled as continuous-time averaged state space

In continuous conduction, increase DDD while VinV_{in}Vin​ stays fixed. What should vov_ovo​ do?

In continuous conduction, increase $D$ while $V_{in}$ stays fixed. What should $v_o$ do?