High Performance, Variable Power Supply, Team Energy Efficient

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1 Project Overview

The DC Power supply is a very important tool for students studying in electrical engineering. Students can use the power supply to power their electronic devices and test the electric circuit they plan to build. The School of EECS provide power supplies in lab for student purposes, but there are a limited amount of tools. Some students can only access the equipment by attending another lab session or by getting a key card from taking a professional electrical engineering class. The price for power supplies are expensive and students are not able to afford the cost. In order to encourage Electrical and Computer Engineering students at Oregon State University to learn more about electrical engineering outside lab, the School of EECS would like to have an inexpensive high current and efficient variable power supply for every student.

To meet the needs for the School of EECS, our team, Energy Efficient, will be designing a low cost high current and efficient variable power supply. Considering that it is for student use, the School of EECS has requested that the power supply will need to be able to supply 0-25V DC and up to 10 Amps. Secondly, the power supply must be safely equipped, so that it will not environmentally cause harm to the student. The School of EECS would prefer the power supply to be designed at a low cost so that students can afford. Since the product will be for students in the future, a PCB with board layout is highly desired, so that the system can be easily mass manufactured to give to students.

1.1 Minimum Requirement set by Customer Needs

We had a meeting with our sponsor, Don, on Friday, October 16 and we had a brief discussion about the features he would like to be implemented on the variable power supply. The power supply needed to convert the electric power from the wall outlet to a usable form for the user. We took notes on what the customer needed and tried to discuss about the impacts on cost. After reviewing the notes, we were able to compile a list of expectations from the customer in the form of a list. The following list shows our customer's requirement that we must meet to successfully carry the project to completion.

*The power supply should be easy to use. Users should be able to safely use all features with minimal training.
*The system must be safe to use The power supply will not cause harm to the user or the device itself under normal operating conditions.
*The power supply should be readily reproducible The final product should include comprehensive CAD designs, schematics, and board layouts, so that more can be manufactured in the future.
*The power supply needs two channels, each able to supply 10 amps at 24 volts. The power supply will include two channels, one supplying negative voltage, the other positive. Both channels will be capable of supplying power simultaneously.
*The device must have a user interface. The customer wants a user interface on the power supply, so that users can easily interact with the power supply.
*The system must be cost effective. Since the product will be for students in the future, the customer wants the power supply to be cost effective.

1.2 Project Scope/Goal

Project Objective: The variable switched power supply will be designed and implemented on a budget of $400 and will be presented at the Engineering Expo in May 2011.

Because of the high cost of energy efficient, high current power supplies, the School of Electrical Engineering and Computer Science here at Oregon State University needs a safe and reliable yet inexpensive power supply to provide high current often required by many student projects. To meet this need, our team, Energy Efficient, will implement a switch mode power supply with two independently variable channels: each capable of supplying 1 to 24 Volts DC. Both channels will be adjustable up to 10 Amps independently. Additionally, our product will be optimized for size and portability; only small, solid state switching converters will be used in lieu of less efficient and bulky linear converters. Per our client's requirements the system will also have both constant voltage and constant current capabilities with a high efficiency. Lastly, the power supply will include a digital interface, controlled by a microcontroller, that will allow both accurate and simple control of voltage and current with a simple, easy to read display.

Our system will be constructed as follows:

• 120 VAC power will be used as the source of power. An AC/DC converter will be used to step down the voltage to a 36V internal distribution line
• The output power will be processed using one variable DC/DC converter per channel
• Another DC/DC converter is used to supply power to the microcontroller, the control electronics, and to power the LCD
• An LCD will show the actual values for both voltage and current in both channels
• All relevant circuit elements will be mounted to individual heatsinks and a cooling fan will also be included for further heat management
• A circuit breaker will act as a safety device to stop the power supply from being damaged from an overcurrent situation
• The system will be manufactured on a series of printed circuit boards

2 Background Research
3 System Requirements and Desired Features
4 Design Solutions
5 Top Level Block Design

5.1 Primary Regulator
5.2 Microcontroller
5.3 HighLevelCode
5.4 Encoder
5.5 LCD Display
5.6 Adjustable Voltage Regulator
5.6 Positive Voltage Regulator
5.7 Negative Voltage Regulator
5.8 Positive Voltage Sensor
5.9 Negative Voltage Sensor
5.10 Positive Current Sensor
5.11 Negative Current Sensor

6 Testing
7 Project Timeline
8 System Test Evidence
9.Project Improvement
10.Expo Materials

Project Video

Team Members

From left to right: Yiwei Li, Alex Ridley, Jerry Vang

Jerry Vang, vangy@NOSPAM.orst.edu replace NOSPAM with onid
Alex Ridley, ridleya@onid.orst.edu
Yiwei Li, liyi@onid.orst.edu

Responsibility Contract

Sponsor/Mentor

School of Electrical and Computer Science: Don Heer

References