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AC-DC Switching Power Supply by 9I3NA0


									Switching Power Supply
         ECE 445
     Project Proposal

         Tony Lin
      Hsin-Cheng Yao
I.   Introduction

     Title: Switching Power Supply
           Switching power supply has its dominant role in the era of ever
     advancing technology. Power is needed in every electronic device and
     switching power supply is a crucial component in many electronic devices
     such as computer and its peripherals. Switching power supply has the
     advantage in its small size, light weight, high efficiency, and the capability
     of taking a wide range voltage input.

          As the technology advances, people often find themselves traveling
     with many portable devices such as a laptop computer, cell phone, and a
     digital camera. These devices all require power and some might find it
     really inconvenient to travel with many cords and chargers. Sometimes
     people might just forget to bring one of the chargers. Our switching power
     supply will serve as a one-fit-all AC-DC converter for all the above devices
     to solve the problem and save the trouble. Due to its multiple DC output
     voltages, our switching power supply can be used for more than one
     device depends on its rating.

         Our project is to design and build a high efficient switching power
     supply at about 80% efficiency. It takes a wide range AC input
     approximately from 90V to 130V at 60 Hz and converts it to multiple DC
     output voltages. This wide range AC input voltage rating is designed for
     customers traveling abroad. Our switching power supply will deliver a
     regulated 12V and 5V DC output at 2A for loads with 24W and 10W

         Benefits to End Customers: Multiple Output Ratings
                                     High efficiency
                                     Wide voltage input range
                                     Small in size
         Product Features: AC wall plug
                          On-off switch
                            Fuse for safety protection
                            Adjustable output rating
                            PWM chip
II.   Design
      1. Block Diagram

      2. Block Descriptions
             AC Input – the AC input is simply the commercial AC power
              supply, a plug is connected to our device input for users to simply
              connect the switching power supply to outlets on the wall.

             Rectifier – A rectifier is to take AC input and rectifies the
              negative sine wave AC voltages to positive waves. It is a process
              of converting AC voltage to DC voltage. It is built with four diodes
              called a “bridge rectifier.”

             Filter – The filter takes the rectified voltage and smooth out the
              waves to make it a constant DC voltage. This is done by a
              capacitor constantly charging and discharging.

             Transformer – The transformer is a part of the DC-DC converter
              that takes input from the output of the filter and transforms the
              DC voltage to our desired DC voltage. The number of turns of the
              wire is to be calculated. There are other elements in addition to
              the transformer. The components will be chosen to dissipate little
              power as possible. For example, the switch will be an nMOS
              transistor with low impedances.

             PWM – The Pulse Width Modulator chip is to control the on-time
              of the transistor switch to regulate the duty cycle to control and
              adjust output voltage to the desired value. It compares the output
              voltage with the reference voltage and increases or decreases
             the duty cycle as necessarily to produce the proper output

            Optical Coupler – Also called the optoisolator, is to isolate the
             primary (input end) and the secondary (output end) circuits. It
             also serves also a path for feedback signals from the load to the
             PWM for voltage stabilization.

            Load – The load can be any electronic device that takes our
             ratings of 24W or 10W.

    3. Performance Measurement
            Effectiveness to 90V to 130V AC input range
            Regulated 12V output voltage at 2A
            Regulated 5V output voltage at 2A
            80% efficiency

III. Verification
     1. Testing Procedures
        AC Input – an adjustable AC input device is needed to test our circuit’s
        reaction to various AC input voltages.

        Reification and Filtering – measurement and graphs should be
        recorded to test our rectifier and filtering circuit.

        Duty Cycle – measurements should be taken at the gate to ground on
        our nMOS transistor switch to obtain graphs of transistor on-time and
        off-time in order to calculate different duties in reaction to different
        loads. In this test, an adjustable load device is needed.

        Efficiency – testing the efficiency by using a wattmeter to measure the
        input power and the output power of the circuit and calculate it by using
        the equation, efficiency = (Pout / Pin) * 100%.

      DC Output – testing the DC output by using a voltmeter across the
      output node of the circuit. Load across the output circuit will be varied
      with an adjustable load machine.
     2. Tolerance Analysis
        The component that most affects the performance of the circuit is the
        nMOS transistor that will be used as a switch. We should keep an eye
        on the power dissipation and its duty cycle control function in reaction
        to different loads.

IV. Cost and Schedule
    1. Cost Analysis
         ($50/hr) * 2.5 * 2 people * (12 weeks * 10 hrs/wk) = $ 30000

  Part Name          Vendor        Part Number   Quantity    Price      Sub Total
     Plug           Any Vendor                      1        $0.5         $0.5
ON/OFF Switch       Any Vendor                      1        $0.5         $0.5
     Fuse           Any Vendor                      1        $.0.4        $0.4
Bridge Rectifier     Fairchild       KBU6J          1        $1.33       $1.33
  Integrated         Fairchild     UC3842AN         1        $1.90       $1.90
                      Texas          TL431          1        $0.50       $0.50
  Transistor       International    FB9N60A         1        $1.70       $1.70
Fixed Resistor      Any Vendor       Varies        ~15       $0.10       $1.50
  Adjustable        Any Vendor         1k                    $0.5         $0.5
   Capacitor        Any Vendor       Varies        ~15       $0.20       $3.00
   Inductor         Any Vendor                      1        $0.10       $0.10
    Diode           Any Vendor       Varies         5        $0.20       $1.00
 Transformer        Any Vendor      Self-Built      1        $5.00       $5.00
  PCB Board         Any Vendor                      3         $3         $9.00
  IC Socket         Any Vendor        8 pin         2        $0.30       $0.60
  Heat Sink         Any Vendor                      1        $0.10       $0.10
  Parts Total                                                           ~$30.00
               *Price Source: Newark InOne Electronic Component Distributor

         Total Cost: $30,030
       2. Schedule
Week       Task                                Member Involved
9/13       Research                            Tony and Hsin
           Work on proposal
           - intro, design, and verification   Tony
           - cost and schedule
9/20       Research                            Tony and Hsin
           Initial schematic design            Tony and Hsin
           Ordering parts                      Hsin
           Prepare for design review           Tony and Hsin
9/27       Design Review                       Tony and Hsin
10/4       Circuit design layout               Tony
           PCB layout                          Hsin
           Circuit assembly                    Tony and Hsin
10/11      Circuit assembly                    Tony and Hsin
10/18      Circuit assembly                    Tony and Hsin
10/25      Testing and debugging               Tony and Hsin
           Prepare for mock-up demo            Tony and Hsin
11/1       Mock-up demo                        Tony and Hsin
11/8       Testing and debugging               Tony and Hsin
11/15      Testing and debugging               Tony and Hsin
11/22      Prepare for demo                    Hsin
           Prepare for presentation            Tony
11/29      Demo and presentation               Tony and Hsin
           Final paper                         Tony and Hsin

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