DC Power Supply - Phase 2

gilamonsterbirdsElectronics - Devices

Nov 24, 2013 (3 years and 6 months ago)

87 views

Multiple
-
Output, Variable
-
Output

DC Power Supply
-

Phase 2


May 04
-
08

http://seniord.ee.iastate.edu/may0408/

Multiple
-
Output, Variable
-
Output DC Power Supply


Client


Senior Design


Dr. Lamont


Prof Patterson


Advisors


Dr. Potter


Dr. Ajjarapu


Team Members


Benjamin Voetberg, EE


Fares Karadsheh, EE


Trung Nguyen, EE


Darrell Long, EE

Senior Design :: May 04
-
08

Overview


Project objectives & guidelines


Create low cost dc power supply


Range of voltages


Design Approach


ac to dc


End Result


What the team accomplished


Budget


Price comparison


Layout of cost


Schedule


Project Evaluation


Risk and Risk Management

Senior Design
::

May 04
-
08


Project Objectives & Guidelines



The project is to design a DC power supply that provides
power at various voltages


+/
-

voltages will include 5V, 6V, 12V, 18V


+/common voltages will include 1.5V, 3.0V, 3.2V, 3.3V,
4.5V, 5V, 6V, 7.5V, 9V, 12V, 15V, 18V, 24V


Voltmeter and Ammeter to display output values


Between 2 to 4 output terminals.

Senior Design
::

May 04
-
08


Project Objectives and
Guidelines Cont.


Operating Environment


Indoor use for senior design projects


Intended users/uses


Students enrolled in EE/CprE senior design


Possibility for use in freshman and sophomore level
labs


Used to test senior design projects that require DC
voltage


Assumptions/Limitations


Powered by a 120V, 60Hz wall outlet


+/
-

1% ripple output voltage


Function with +/
-

5% of wall outlet voltage


Output current not to exceed 1A on each terminal

Senior Design
::

May 04
-
08


Design Approach Definitions



PWM : Pulse Width Modulation




Duty Ratio (D) : Time ON divided
by the total time



Lm : Magnetizing Inductance of a
transformer



For the simulation, 2 choice:



Pspice: Available and have a lot of
parts


Electronic Work Bench : Easy and
more visual






Senior Design
::

May 04
-
08


Sample from the
simulation

Electronic Work Bench was
used to simulate the design


Design Approach Buck Converter


Convert ac to dc using
bridge rectifier


Buck converter is used to
vary the voltage to get
desired voltage output


Buck converter output

Vo=Vs*D


Buck converter diagram

Simple ac/dc conversion

Design Approach Flyback
Converter





Not able to make 1.5
-
24
volts directly from 120 V



Use a flyback converter



Flyback converter output
equation


Vo=Vs(D/(1
-
D)) N2/N1

Senior Design
::

May 04
-
08


Design Approach PWM


Output equations:



Vo=Vs(D/(1
-
D)) N2/N1


(Flyback)



Vo=Vs*D ( Buck )



PWM : Generate a
square wave.
(see figure)


Trig.source

Comparator

Senior Design
::

May 04
-
08




The Reason behind using Flyback then a
__
buck converter is to create an isolation.


Design Approach Taken


A commercial power supply to replace


bridge rectifier


flyback converter.


Power supply eliminates problems


Current and the voltage regulation


Difficulty finding transformer


Saved time


Even with changes still functions as the
simulation


Buck converter still used to vary voltage to get
desired output

Senior Design
::

May 04
-
08


The new design

Senior Design
::

May 04
-
08


Power Supply

120 VAC

Wall outlet


48VDC

Fixed Buck
Converter

High Freq.
Switch

TL499
ACD

25VDC

Variable
Outputs

Variable Buck
Converter


End Product Options

# of +/
-

terminals

# of +
terminals

Meters

Option #1

1

1

Ammeter

Voltmeter

Option #2

1

2

Ammeter

Voltmeter

Option #3

2

2

Ammeter

Voltmeter



Client wants for power

supply




Low cost system



Useful to senior

design teams




Portable Power

Supply

Senior Design
::

May 04
-
08


Commercial Power Supply


Astrodyne ® Power Supply


Regulated Output


85
-
265 VAC input


Overload Voltage protection


Short Circuit Protection


EMI Filter

Senior Design
::

May 04
-
08


Fixed Buck Converter


Switch components


Motorola SG3527A Pulse Width Modulator Control Circuit


Fixed duty ratio, 44 VDC to 25 VDC


Sends square wave to MOSFET DRIVER


Maxim MA4428 Dual High
-
speed 1.5A MOSFET Driver


Drivers both a N
-
channel and P
-
channel MOSFET to achieve
the desired switching speed

Texas Instruments TL499A circuit

Wide
-
Range Power
-
Supply Controllers


R1, R2, R3 create a
comparison voltage


Voltage varied by changing
potentiometer


Minimum output voltage is
2.5 volts.


Maximum output voltage is
24 volts

Digital Display


Maxim ICL7107 3 1/2
Digit A/D Converter


Connected across the
output


Displays output
voltage to 1/10
accuracy


2 double digit 7
segment LED displays

Future Work Recommendations


A phase to finalize the project


Necessary future work


Negative voltages


Voltage regulation


Circuit protection


Other future work


Variable current


Voltage zero at start up


Auto zeroing voltmeter

Senior Design
::

May 04
-
08


Financial Comparison

Senior Design
::

May 04
-
08



Agilent 3631a triple output power supply


80 watts


+

25 V at 1 A


+6 V at 6 A


$ 1200


Proam universal ac
-
dc adaptor


9 watts


+ 1.5, 3, 4.5, 6, 7.5, 9, 12 V at .5 A


$ 9.00


Our design now


24 watts


2.5 to 24 V at 1 A


$ 120


Personal Time Commitment

Senior Design
::

May 04
-
08


Paper

work

Research

Design

Construction

Total

Darrel

Long

25

41

42

24

134

Fares

Karadsheh

20

48

47

14

131

Trung

Nguyen

22

41

43

24

132

Benjamin

Voetberg

25

51

45

14

137

Total

90

184

195

65

534

First Semester Schedule

Senior Design
::

May 04
-
08


Second Semester Schedule

Senior Design
::

May 04
-
08


Project Evaluation


Identify possible designs to implement, completed


and choose one
















Design hardware





completed



Hardware specifications




completed



Circuit simulations




completed












Test hardware





almost complete











Documentation





completed








Senior Design
::

May 04
-
08


Lessons Learned


What went well


Communication


Within the team


With company representatives


Teamwork


What didn’t go well


Unspecific project, time constraint for meeting with
clients


Simulation of the circuit


Hardware implementation


Technical knowledge gained


Simulation experienced gained


Power electronics knowledge

Senior Design
::

May 04
-
08


Risk and Risk Management


Anticipated risks


Team scheduling


Loss of team member, advisor, or clients


Unanticipated risks


Simulation complications


Hardware implementation


Unable to use certain designs because of cost

Senior Design
::

May 04
-
08


Closing Summary


Variable dc output of 2.5 to 24 volts


Meets client specifics


Provides extra voltage values


Digital voltmeter


Accurately provides output voltage


Design is a solid base to further expand


Negative voltages


Circuit protection


Voltage regulation

Senior Design
::

May 04
-
08


Questions?

Senior Design
::

May 04
-
08