STM32 Buck Converter

STM32-Controlled Synchronous Buck Converter

MATLAB and Simulink models of a 12 V to 5 V synchronous buck converter. The project includes averaged and PWM switching power-stage models, a digital PI-controlled averaged model, and a reproducible load-transient test. The digital-control target is an STM32G431RB.

Project status: This is a design-only project validated with MATLAB, Simulink, and automated error-level KiCad ERC/DRC checks. No physical converter prototype has been built or hardware-tested. All waveforms, plots, and performance values in this repository are simulation results, not bench measurements.

Design values

At 12 V input with a 5 Ω load, the open-loop models settle close to 5 V and 1 A. The startup ringing is from the LC output filter.

Simulation results

Averaged model

PWM switching model

Three closed-loop switching cases were checked independently from the averaged model. Their steady-state inductor-current ranges are 0.5970-1.4357 A at 12 V/5 ohm, 1.7332-2.2652 A at 10 V/2.5 ohm, and 1.4900-2.5089 A at 14 V/2.5 ohm. The 2.5089 A value is the simulated worst-case peak. Exported waveforms are restricted to the common time support of every source signal; the validation rejects nonfinite data, extrapolation, or current magnitude of 10 A or more.

Closed-loop load transient

The averaged closed-loop model commands 5 Ω from 0–15 ms, 2.5 Ω from 15–35 ms, and 5 Ω from 35–50 ms. The settled operating points are approximately 5 V/1 A, 5 V/2 A, and 5 V/1 A. Maximum load current is 2.105 A.

Measured voltage response:

See Documentation/load_transient_validation.md for the measurement method and detailed results.

Control analysis

The averaged duty-to-output plant has a complex pole pair at −1739.849 ± j14526.197 rad/s and an ESR zero at −500000 rad/s. With the manual PI gains Kp = 0.02 and Ki = 60, the nominal averaged loop has 73.877° phase margin and a 2359.620 Hz gain crossover frequency.

See Documentation/control_analysis.md for the derivation, limitations, and generated numerical data.

The manual averaged controller's deliberately severe line test produces a 1.144 V undershoot for 12 V to 10 V and a 2.597 V overshoot for 10 V to 14 V. Both responses remain finite and settle, but they show that line feedforward or a different large-signal control strategy would be needed for a hardware-oriented design.

KiCad validation

KiCad CLI 10.0.4 reports zero schematic ERC errors, zero PCB DRC errors, and zero PCB unconnected items. The full PCB report intentionally retains warning findings for missing courtyards, silkscreen over copper, installed-library comparison, and schematic/PCB field or flat-net-name parity. No DRC category is ignored. See Documentation/kicad_design_notes.md for exact counts and limitations.

Running the models

1. Run MATLAB/buck_parameters.m.
2. Open a model from the Simulink folder.
3. Run the simulation and open the voltage and current scopes.

To reproduce the configured load profile and validate every Simulink model:

addpath('MATLAB')
run('MATLAB/buck_parameters.m')
configure_load_transient_model
report = validate_project(true);

validate_project(true) updates and simulates every .slx model, checks recorded signals for finite values, validates the three load operating points, measures both voltage transitions, and regenerates Results/load_transient_response.png. Simulink cache and code-generation files are redirected to the system temporary directory.

To run the complete project validation—including control analysis, every Simulink model, averaged and switching closed-loop operating cases, transient tests, and optimization-assisted PI tuning—start a clean MATLAB session and run:

addpath('MATLAB')
report = run_all_validations();

For one persistent, uninterrupted MATLAB R2025b record, run this command from the repository root in PowerShell:

& 'C:\Program Files\MATLAB\R2025b\bin\matlab.exe' -logfile 'Results\full_validation_log.txt' -batch "addpath('MATLAB'); report = run_all_validations();"

A successful run exits normally and ends the log with FULL_VALIDATION_PASS. The checked-in log is a software-validation record, not a hardware test log.

The models were made in MATLAB R2025b using Simulink and Simscape Electrical.

Repository files

• MATLAB/buck_parameters.m: design calculations and workspace values
• MATLAB/configure_load_transient_model.m: reproducible load-profile setup
• MATLAB/control_analysis.m: averaged plant and manual-PI loop analysis
• MATLAB/validate_project.m: all-model simulation and result generation
• MATLAB/run_all_validations.m: one-command complete validation
• MATLAB/run_switching_validations.m: switching cases and export sanity checks
• Simulink/buck_average_open_loop.slx: averaged converter model
• Simulink/buck_average_closed_loop.slx: PI-controlled averaged model
• Simulink/buck_average_load_transient.slx: validated load-step model
• Simulink/buck_switching_open_loop.slx: PWM switching model
• Firmware: portable STM32G431RB control core and integration notes
• KiCad: editable schematic/PCB, BOM, reports, and viewable exports
• Documentation: specifications and test notes
• Results: calculated values, CSV datasets, plots, and full validation log