# Compact USB-C Switching Power Supply for Test Benches
Developed an open-source switching power supply for bench-testing devices under load (DUT). The unit draws power from USB-C Power Delivery up to 100 W and delivers 0–32 V at 3 A, with voltage ripple <30 mV pp and current ripple <2 mA RMS. Controlled via MCU over USB with a Python library, it supports SCPI and custom algorithms. No galvanic isolation—the focus is on compactness and integration into test benches.
Structurally: USB host (PC or SBC) controls the MCU, which manages the Type-C adapter and DUT load. The PLD connector combines power input/output, USB, and MCU interfaces. Protections: OVP, OPP, OCP (response <10 ms at Iload > 2×Iresp), overtemperature.
Integration into Test Benches
In test benches, the supply mounts inside the fixture. DUT power is delivered via board-to-board connectors or wires. Multiple units can be installed for multi-voltage tests or with an integrated control PC.
Key scenarios:
- Mounting on the rear panel with connector access.
- Cascaded power via cross-boards.
- Multichannel configuration (multiple supplies).
- Built-in PC with USB access on PLD.
Automation: preset algorithms, event triggers, shutdown on current exceedance. No manual controls—minimizes human error in remote production.
Desktop Use
For developers, the unit replaces bulky lab power supplies. Setup via console, Jupyter, or SmuView. Single button for on/off, LED status indicators. Output via 4 mm banana jacks.
Advantages:
- Compactness without a screen (like logic analyzers).
- Setpoint resolution: 10 mV (V), 1 mA (I).
- Setpoint accuracy: <0.1% + 30 mV (V), <0.1% + 5 mA (I).
- Measurements: V, I, P with 10 mV/1 mA resolution, accuracy <0.1% + offset.
Optional: module with display and encoders.
Detailed Specifications
Electrical Parameters
| Parameter | Value |
|----------|-------|
| Input | USB-C PD 100 W |
| Output | 0–32 V, 3 A, 96 W |
| Voltage ripple | <30 mV pp |
| Current ripple | <2 mA RMS |
| Load regulation (10–90%) | V: <0.1% + 20 mV, I: <0.1% + 5 mA |
| Line regulation (±10%) | V: <0.1% + 20 mV, I: <0.1% + 5 mA |
| Recovery time | <200 µs |
| Overshoot at turn-off | <100 mV |
Protections and Control
- OVP/OPP/OCP: adjustable, OCP <10 ms.
- Interfaces: USB-B, SCPI, MCU ports for custom.
- Construction: passive heatsink, threaded holes, USB-C/B, banana, PLD connectors.
Key Highlights
- Bench Stability: load regulation <0.1% + offset, recovery <200 µs—critical for automated cycles.
- Open-Source: hardware/software in Python, MCU firmware mods.
- Compactness: integrates into fixtures without display, multi-unit configs.
- Measurements: <0.1% accuracy for real-time V/I/P monitoring.
- Roadmap: gather feedback, testing, crowdfunding on CrowdSupply, tool series (programmer, DAQ).
— Editorial Team
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