Steve Sam Soon, Jean-Michel Redoute

This project involves the design of a PIC controlled DC-DC converter, which converts a 5 V DC input from the USB port to a user-selected 1.5V - 12V DC output: the purpose of this circuit is to charge batteries using the laptop's USB port.  The system uses a Cuk buck-boost DC-DC topology, and is able to handle power ratings up to 2500 mW.  The device works by generating a PWM signal using the PIC18f4550, where the required duty cycle is calculated and sent to a Cuk DC-DC converter using the PWM output on the PIC.  A feedback algorithm was programmed on the PIC by using the ADC ports to monitor the voltage across the load and modify the duty cycle if necessary.  The hardware was implemented on a PCB.  The firmware algorithm was written in C using Mplab from Microchip. The software algorithm was implemented in C# using Microsoft Visual Studio 2010 Express edition. The user can select the desired output voltage through the graphical user interface, which can be installed on any Windows computer platform. Communication between the computer and the power converter is performed through the USB interface.

View a demo movie here: http://www.youtube.com/watch?v=hHt00_JEdnk&feature=youtu.be

Top view of the PCB

 

Schematic