Automated Hardware-in-the-Loop Validation of a DC-DC Converter

Virtual Instrumentation course, SSIs M.Sc. (BME) · Budapest, Hungary · Dec 2025 · Academic project · Team of two

A LabVIEW test system that switches loads programmatically and validates an LM2596 buck converter against pass/fail criteria using NI USB-6001 DAQ hardware.

LabVIEW
NI DAQ
HIL testing
Power electronics
Test automation

Overview

An automated test bench for an LM2596 buck converter (9 V in, 3.0 V out): the test system applies load combinations, measures the converter's response, and issues pass/fail verdicts per test vector, with everything logged for later analysis.

Technical approach

Four MOSFET-switched parallel load resistors driven from the DAQ digital outputs, giving 16 load combinations down to 1.3 ohms
Differential measurement across a 0.68 ohm sense resistor for input current; referenced single-ended channels for input and output voltage, at 1000 samples per second
LabVIEW state machine stepping through editable test vectors with pass/fail criteria on voltage, ripple, and efficiency
Automatic logging and spreadsheet analysis, with multimeter cross-validation

Results

Measured efficiency of 70 percent at the 10 ohm load point
At maximum load the current limiter engaged and the converter failed the efficiency criterion (62 percent), correctly flagged by the automated system
Multimeter cross-validation agreed within 0.02 V

Media

LabVIEW test sequence results with pass/fail indicator lights — Automated run over the full load sweep: per-vector pass/fail verdicts on input voltage, output voltage, and efficiency. The maximum-load vector correctly fails.

Photograph of the DC-DC converter test PCB — The BME course PCB under test: LM2596 converter, MOSFET-switched load resistors, and sense circuitry.

LabVIEW block diagram of the measurement and pass/fail logic — Measurement and verdict logic in the LabVIEW block diagram: efficiency, input voltage, and output voltage checks against per-vector pass limits.

LabVIEW case structure for load switching — Load-set case structure translating test vectors into MOSFET switch states, from no-load to the 1.31 ohm maximum load.

DAQmx channel configuration panels — DAQmx channel configuration: differential current sensing and referenced single-ended voltage channels at 1000 samples per second.