Power Electronics

Assignment Part A - SMPS Investigation & Analysis Introduction

You are required to investigate and analyse a particular type of SMPS converter. Each student will be given their own unique circuit to analyse. This information is provided in a table 1 below. There are three types of converter under investigation:
- Buck converter
- Boost converter
- Buck-Boost converter
For the investigation and analysis the following tasks need to be undertaken
- Description of operation (switch open and switch closed with formulas developed), function of each component (include all schematic's)
- Modelling of a switch
- Waveforms from your analysis
- Duty cycle, Vout/Vin ratio
- Are components consistent with design formula? (Show calculations)
- Are components used correct? Explain.
- Are correct voltages and currents achieved through simulation? Give explanation if not.
- What is the effect of altering duty cycle? Show.
- How duty cycle is changed? Show.
- Ripple voltage investigation on output - what parameters effect the ripple voltage? Investigate and show.
- What are the effects of capacitor ESR?
- What are the effects of altering the switching frequency? Show.
- All waveforms need to be included, correctly formatted and explained for all of these aspects listed above.

Table 1 - Parameter Assignments

Assignment Part B - Switched Mode Power Supply (SMPS) Design

The aim of the exercise is to design a DC-DC converter using either the buck, boost or buck- boost circuit topologies. You will be assigned a design specification for one of the circuit topologies in table 2. All converters are to be capable of providing 0 to 500 mA to a resistive load. The ripple specification is 1 % of the output voltage.

Table 2 - Design Specifications

A central aim of the project is to learn and understand the SMPS design process. Show all calculations and verify your design using LTSpice. Show all relevant plots and state any assumptions made. Plots to be shown include
- Imax and Imin
- Vout
- VL
- VRipple
- Duty cycle control Calculations to be shown include:
- Inductor value
- Capacitor value
- Resistor value
- Imax & Imin
- Duty Cycle
- Inductor voltage

- If any simulated values do not fully correspond to calculated values indicate possible reasons for this and make adjustments to your design to compensate. Show all plots and calculations for adjustments made also.
- Indicate relevant parameters of components that need to be taken into consideration when specifying a component and apply them to your design.
- Investigate the use of initial conditions and apply them to your simulation.

WEBENCH
- Create an account with Texas Instruments. Using WEBENCH Designer, create a design using your design specifications.
- Pick a device that closely matches your design specification.
- Export the design schematic to your report. Explain the function of each component and explain why each are suitable for the design.
- Export the operating point values and compare with calculated values where possible.
- Export and examine the efficiency graph. Comment. What parameter/parameters affect the efficiency?
- Run a thermal simulation on the design. What information can be taken from this?
- Examine the datasheet for the IC used for your design. Summarize its features.
- Generate a bill of materials and costing for the design.

Screencast

As part of this assessment a screencast will also be required to be given by each student on either their converter analysis or design. This should be 10 minutes long and should be used to demonstrate your understanding of the task undertaken.

Ensure the screencast is timed correctly and is clearly audible.