Project of ECE 3031 Electrical and Computer Engineering Design Isolated Power Supply

Katie McDonald Emma Thomson Brandon Drake

Christian Richard

April 8, 2016

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Table of Contents Abstract……………………………………………………………..…………....………..2 Introduction………………………………………………………...……………..……….3 Preliminary Design……………………………………………………………………..….4 Idea Generation……………………...……………………………………….…...…….....4 Conceptual Design………………………………..………………………….……………5 Detailed Design……………………………………………………………………...…….7 Detailed Calculations…………………………………………………………………..….7 Bill of Materials.................................................................................................................10 Detailed Electrical Circuit..................................................................................................10 Design Verification & Testing..……………………..……………………………..……..11 CSA & UL Standards…………………………………………………………...………..11 Test Plan……………………………………………………………………………....….11 Test Results……………………………………………………………………………....12 Conclusion……………………………………………………………………………….17 Future Work……………………………………………………………………………...18 Appendix A-User’s Manual…………………………………….………………..……....19 Appendix B-References………………………………………………………………….22

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Abstract This report reviews the design processes which lead to the final design and implementation of an isolated dc power supply. The report will go over the five major design stages which are Idea Generation, Conceptual Design, Detailed Design, Design Verification and Testing, and Final Design for Production. The first stage of the design project was Idea Generation, which includes the Needs, Constraints, Attributes/Features, and Engineering Requirements of the product. The second design stage was the Conceptual Design of the product, determining the product’s functions and various concept; this section includes the Morphological Chart, Screening of Concepts, and the Evaluation Process. The third stage was the Detailed Design, also known as Design Embodiment, consisting of Calculations, Simulations, Drawings and Diagrams, Details, Specifications, and Costs. The fourth stage of the design process was Design Verification, which includes Design Optimization, Prototype Development, Simulations, and Testing. The fifth and final stage of the project was the Final Design and Production which entailed Refinements, Production, Quality Assurance, and Documentation.

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Introduction The project involved the design of an isolated power supply, given a number of rather vague design requirements. The given requirements for the product were to implement a regulated power supply with a 120V/60Hz ac input, 15V dc output, and 30W rated load. It was to be electrically isolated between the input and the output, with the use of a transformer. It was required that the power supply be safe, reliable, efficient, and economical. The design team was to apply the concepts of the design process discussed in class to determine the detailed specifications, design the product, implement and test the prototype, and make the power supply work.

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Preliminary Design Idea Generation Design Requirements:

120V/60Hz AC input 15V DC output 30W rated load Regulated power supply Electrically isolated between input and output (transformer) Safe to use Efficient Economical Reliable

Functions of the Product:

Step Down Voltage AC/DC conversion Isolation Regulation Indication Filtering

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House of Quality

Conceptual Design Morphological Chart:

Function Options

Step Down Voltage Transformer DC Chopper

Voltage Divider Op Amp

AC/DC Conversion Full Wave Rectifier

Half Wave Rectifier

Full Wave Rectification with Center Tap Transformer

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Isolation Circuit Breaker

Fuse Transformer

Regulation Zener Diode DC Chopper

Op Amp

Indication LED Audio LCD

Filtering RC Filter RL Filter RLC Filter

Options in red were immediately eliminated before determining the combination options.

Function Combination 1 Combination 2 Combination 3

Step Down Voltage AC/DC Conversion Isolation Regulation Indication Filtering

Transformer Full Wave Rectifier Transformer DC Chopper LED RC Filter

Transformer Half Wave Rectifier Transformer DC Chopper LCD RC Filter

Transformer Full Wave Rectifier Transformer Op Amp LED RLC Filter

The LCD screen was eliminated due to the fact that it would be far too complicated and expensive, and therefore option two was out of the question. The third combination was dropped as well, due to the limited use of the op amp and the RLC filter not being optimal for the design. It was determined that combination 1 would be the best option for the design:

Step Down Voltage: Transformer AC/DC Conversion: Full Wave Rectifier Isolation: Transformer Regulation: DC Chopper Indication: LED Filtering: RC Filter

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Detailed Design Detailed Calculations Calculations for the Red LED (C5SMF-RJS-CT0W0BB2)

From the Red LED datasheet:

Characteristic Value Forward Voltage Drop (VF) Typical 2.1 [V], Max. 2.6 [V] Recommended Forward LED Current 20 [mA] Maximum Forward LED Current 50 [mA] For resistor:

R = 20[mA]15[V ]−V E Rtyp. = 20[mA]

15[V ]−2.1[V ] Rmin. = 20[mA]15[V ]−2.6[V ]

Rtyp. = 645 [Ω] Rmin. = 620 [Ω].

For design purposes, a 680 [Ω] resistor with 5% tolerance (PR01000106800JR500) was chosen and this will result in a forward LED current that is around 18 to 20 [mA]. The total power loss is 0.3 [W] (15 [V] x 20 [mA]) which means that the resistor needs a power rating above 0.3 [W].

Calculations for the Voltage Regulator (LM2576T-15/NOPB)

There is no need for an input capacitor because there is a much bigger capacitor in the bridge rectifier filter. The datasheet of the LM2576 voltage regulator suggested a 1N5820 Schottky diode and 220 [µH] inductor.

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For the output capacitor, the formula used to obtain values is:

[μF ]Cout ≥ L[μH]13300

V out

V (max)in [μF ] 01[μF ]Cout ≥ 13300220[μH] 15[V ]

25[V ] = 1

To be safe, a capacitor of 1000 [µF] (UVR1E102MPD) was chosen.

Calculations for the Voltage Regulator Heatsink

From the voltage regulator datasheet:

Characteristic Value Maximum Safe Operating Temperature (TJ) 110 [°C] Thermal resistance (θJC) 2 [°C/W] Efficiency (n) 88%

Maximum ambient temperature (TA): 40 [°C]

Assumed thermal resistance of the interface (θinterface) : 1 [°C/W]

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Power dissipated by the voltage regulator is given by:

To meet this requirement, the 7109D/TRG Heat Sink was chosen.

Calculations for the secondary side of the transformer

Transformer Design

Step Down Transformer 120 V down to 22 V Primary Side of 475 Turns ( 26 gauge) Secondary Side of 87 Turns (19 gauge) Turns Ratio of .183

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Bill of Materials:

Detailed Schematic:

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Design Verification & Testing CSA & UL Standards CSA and UL standards applicable to the product of our design: UL 1310-Standard for Class 2 Power Units [1] C22.2 NO. 223-15 - Power supplies with extra-low-voltage class 2 outputs [2],[3] http://ulstandards.ul.com/standard/?id=1310 [1] http://shop.csa.ca/en/canada/general-standards/c222-no-223-15/invt/27008392015[2] http://www.ccohs.ca/products/csa/27008391991[3] Test Plan For the testing of the power supply, the following test will be conducted to calculate technical details such as efficiency and voltage regulation. The power supply features will also be tested to make sure that they work. Tests for Technical Details:

1. Open circuit test Measurements to take:

Input voltage Input current Input power Output voltage

2. Specified load test

Measurements to take: Input voltage Input current Input power Output voltage Output current

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Tests for Features: 1) Switch test (does the output voltage go to 0 (V) when the switch is in the off position?) 2) LED test (is the LED on when the output is 15 (V) and is it off when the output is 0 (V)?) Test Results

Vin (V)

Iin (A)

Pin (W)

Vout (V)

Iout (A)

Pout (W)

N (%)

119 0.12 5.25 14.91 0 0.000 0 119 0.168 11.97 14.81 0.374 5.539 46 119 0.18 13.24 14.80 0.449 6.645 50 119 0.197 15.03 14.79 0.548 8.105 54 119 0.217 16.94 14.79 0.655 9.687 57 119 0.235 18.78 14.78 0.754 11.144 59 119 0.255 20.67 14.77 0.853 12.599 61 119 0.275 22.61 14.77 0.958 14.150 63 119 0.293 24.34 14.76 1.047 15.454 63 119 0.305 25.57 14.76 1.109 16.369 64 119 0.323 27.24 14.75 1.203 17.744 65 119 0.344 29.37 14.75 1.304 19.234 65 119 0.374 32.5 14.74 1.459 21.506 66 119 0.392 34 14.73 1.539 22.669 67 119 0.419 36.8 14.72 1.672 24.612 67 119 0.428 38.5 14.72 1.745 25.686 67 119 0.455 41 14.71 1.867 27.464 67 119 0.48 43.5 14.71 1.983 29.170 67 119 0.511 46.8 14.71 2.118 31.156 67 119 0.53 48.9 14.69 2.222 32.641 67

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Time

(minutes) Rectifier Temperature

() Regulator Temperature

() Transformer Temperature

() 2 37.3 32 28.4 4 36 43 37 6 40 42 34 8 32 40 38 10 80 56 41 12 78 50 48 14 71 56 49 16 68 58 51 18 63 58 52 20 65 55 54 22 86 58 54 24 85 62 58 26 88 58 58 28 85 60 57 30 80 61 59

Voltage Regulation:

00% V )/V 00% 14.91 4.71)/14.71 .4%1 * ( out−minload − V out−maxload out−nominalload = 1 * ( − 1 = 1

Line Regulation: 00% V )/(V ) 00% 14.71 4.19)/(126 0) .44%1 * ( out−mininput − V out−maxinput in−max − V in−min = 1 * ( − 1 − 9 = 1

Features Test Results: LED: LED turned ON when the power supply was ON and OFF when there was no output voltage. Switch: When the switch was ON there was an output voltage and the LED turned ON. When the switch was OFF there was no output voltage and the LED turned OFF.

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Thermal Images:

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Conclusion In summary, the final design of our product meets the design specifications and performs as expected. While most technical specifications obtained from testing were satisfactory, it appeared that there was some room for improvement in the efficiency. However this improvement would likely require a different type of voltage regulator, or a different design. Due to the time limiting nature of the project, several key improvements to the design were not completed in this stage. These are detailed in the future work section of the report.

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Future Work To further the design, several measures could be taken. The following is a point form list of possible improvements:

Adding a more complete enclosure to the circuit to improve aesthetic and safety of the design

Using a machine-wound transformer to improve efficiency Minimizing the size of the power supply by using a custom PCB Adding a second output Adding a potentiometer to allow for a variable voltage Having a built in voltmeter and ammeter

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Appendix A - User’s Manual Introduction This manual contains important information and warning about the safe use of the DC power supply. Please read before operating to ensure user safety. This power supply is designed for benchtop use. It has a single output of 15 V supplying a load of up to 30 Watts. Safety Precautions

1. Never ground yourself when taking electrical measurements. 2. Be careful not to touch exposed circuit components while connected to power. Only

the switch and input/output terminals are designed for user interaction. 3. The unit should be stored in a dry and well ventilated place.

Instructions for Use

1. Input and output connection: Input and output are designed to be connected with banana plug cables, with the input connected on the transformer end of the product, and the output on the opposite end. 2. Safety Features: LED: The red LED indicator turns on when there is power to the circuit Switch: To cut off output power, use the switch depicted in the schematic diagram

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Specifications Design Requirements:

120V/60Hz AC input 15V DC output 30W Load Regulated power supply Electrically isolated between input and output (transformer) Safe to use Efficient Economical Reliable

Detailed Design:

Step Down: Transformer AC/DC Conversion: Full Wave Rectifier Isolation: Transformer Regulation: DC Chopper Indication: LED

Red LED:

C5SMF-RJS-CT0W0BB2 680 [Ω] resistor with 5% tolerance

Will result in a forward LED current that is around 18 to 20 mA Total power loss 0.3W meaning the resistor needs a power rating above 0.3W

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Voltage Regulator: LM2576T-15/NOPB No need for an input capacitor as there is a much bigger capacitor in the bridge

rectifier filter Datasheet of the voltage regulator suggested a 1N5820 Schottky diode and 220 [H]

inductor. 1000 [F] capacitor 7109D/TRG Heat Sink

Schematic

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Appendix B - References “ECE 3031 Lab #1 Idea Generation”, 2016 “ECE 3031 Lab #2 Conceptual Design”, 2016 “ECE 3031 Lab #3 Detailed Design”, 2016 “ECE 3031 Lab #4 Design Verification”, 2016 “ECE 3031 Lab #5 Test and Documentation”, 2016 Ulstandards.ul.com, "Standard 1310 - Standard for Class 2 Power Units", 2016. [Online].

Available: http://ulstandards.ul.com/standard/?id=1310. [Accessed: 26- Feb- 2016].

ShopCSA, "C22.2 NO. 223-15", 2016. [Online]. Available: http://shop.csa.ca/en/canada/general-standards/c222-no-223-15/invt/27008392015. [Accessed: 26- Feb- 2016].

Ccohs.ca, "CCOHS: Products & Services: CAN/CSA-C22.2 NO. 223-M91 (R2013) - Power Supplies With Extra-Low-Voltage Class 2 Outputs", 2016. [Online]. Available: http://www.ccohs.ca/products/csa/27008391991. [Accessed: 26- Feb- 2016].