CPU-

PCB Design Files: Miniature Programmable Power Supply

This directory contains the primary hardware design and layout files for the Miniature Programmable Power Supply (Team TUE-20). These files translate our proposed system architecture into a manufacturable Printed Circuit Board (PCB) designed to replace bulky lab benchtop supplies with a portable, USB-C powered alternative.

Directory Contents

• design.kicad_sch (Master Schematic): Contains the logical circuit design, component symbol definitions, and netlists. It details the wiring between the USB-C power delivery network, the switching regulators, the microcontroller interface, and the digital potentiometers used for feedback loop control.
• design.kicad_pcb (Board Layout): The physical 2D layout of the PCB (1.6mm standard thickness). This file defines component placement, copper trace routing, via stitching, and dedicated ground/power planes required for stable DC-DC conversion.

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System Architecture & Hardware Specifications

The board is engineered to take standard mobile charger inputs and step them up/down to provide clean, adjustable output voltages for breadboard prototyping.

Input Stage:

• Source: Standard USB-C Interface
• Rating: 5V DC @ 2A (Max)

Output Stages:

1. Programmable Single Output:
   • Range: 0V to 12V DC
   • Max Current: 0.5A
   • Topology: Buck-Boost Converter
2. Programmable Dual Output:
   • Range: ±12V to ±15V DC
   • Max Current: 0.2A
   • Topology: Boost and Inverting Configurations

Key Components Implemented:

• MC34063ADG: Primary DC-DC switching regulators driving the step-up and inverting output stages.
• MCP4162-104E/SN (Digital Potentiometer): Controlled via SPI from the central microcontroller to dynamically adjust the analog feedback loops, enabling the "programmable" aspect of the power supply.

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PCB Design Considerations & Engineering Choices

To ensure reliable operation and clean power delivery, the following design constraints were implemented in the board layout (design.kicad_pcb):

• Current Handling & Trace Widths: High-current pathways—specifically from the USB-C input to the inductors and out to the load terminals—are routed with widened traces calculated to safely handle up to 2A of continuous current without excessive temperature rise.

• Thermal Management: Extensive copper pours and via stitching are utilized around the MC34063ADG switching regulators to dissipate heat effectively during heavy loads.

• Noise Isolation (Signal Integrity): Switching power supplies inherently generate noise. We deliberately separated the high-frequency switching nodes of the DC-DC converters from the sensitive analog ADC feedback traces and the digital SPI communication lines to prevent parasitic coupling and ensure stable output regulation.

• Voltage Monitoring: Dedicated ADC feedback paths are routed directly to the microcontroller to allow closed-loop monitoring and real-time adjustment of the output voltages.

  Project Pivot: Overcoming Fabrication Constraints

Our original system architecture relied heavily on a custom-designed printed circuit board (PCB) to integrate an STM32 microcontroller with a digital potentiometer for software-controlled voltage regulation. We successfully completed the complete schematic and board layout for this design.

The Challenge: During the final submission phase, a miscommunication regarding the final PCB fabrication deadline with a TA resulted in our team missing the manufacturing window. Although our design files were complete, we were unable to obtain the physical custom boards required to mount our microcontroller and surface-mount components.

Attempted Workarounds: Without the custom PCB, utilizing our microcontroller-based digital feedback loop became a significant challenge. Under the guidance of Ankur Sir, we initially attempted to migrate our design to standard breakout boards. However, the complexity of the digital-to-analog routing and the high-frequency switching noise of the power stages made a reliable breadboard/perfboard integration of the STM32 and digital potentiometer unfeasible.

Final Resolution & Direct Implementation: To ensure we delivered a functional power supply that met the core voltage requirements of the problem statement, we executed a hardware pivot. We abandoned the unavailable digital control loop and opted for a direct analog implementation.

We procured standalone buck-boost IC modules and directly implemented them to handle the power conversion. While this meant sacrificing the digital LCD interface and rotary encoder functionality we had programmed, it allowed us to successfully demonstrate the core power-delivery mechanics of the project (stepping a 5V USB input to the required variable output voltages) using a robust, alternative prototype.