EEE8147- Advanced Power Electronics and Applications FLYBACK DC-DC CONVERTER SIMULATION ASSIGNMENT 1. AIM AND OBJECTIVE: Flyback converters are very popular in low power applications such as phone adaptor and other household appliances. The aim of this simulation exercise is to evaluate the operation of Flyback dc dc converter in various operating modes and to observe the resultant operating waveforms. Some calculations are required to compare the measurements with the idealised theory that is covered in the lectures. Some design considerations are also required to account for some nonidealities in the system. Fig. 1 circuit schematic of isolated Flyback SMPS 2. EXPERIMENTS Students are required to build a simulation model of the Flyback dc dc converter shown in Fig. 1 using PSIM software (other simulation software are also acceptable) and perform the following FIVE tasks: Note: use an ideal transformer with an inductance in parallel with the primary to represent the coupled inductor Task 1: continuous conduction mode (CCM) operation Build the simulation model for a Flyback converter with the following specifications: , varies between140 − 325 , a constant output voltage, = 5 with a maximum ripple of ∆ = 2% and a switching frequency of = 100 . The magnetizing inductance is found to be 5 and the transformer turns ratio, 1/2 = 15 i. Calculate the range of the duty cycle. SW D C VO L o a d VS EEE8147- Advanced Power Electronics and Applications ii. Plot the current AND voltage across the magnetizing inductance (), noting all amplitudes and timing. Compare the value of ∆ obtained from the simulation waveform with the theoretical value. iii. Plot the voltage across the output capacitor. Measure ∆ and compare it with the theoretical value. (comment on your results) iv. Now increase the frequency to 150 and discuss any impact that might have on the converter operation. Task 2: discontinuous conduction mode (DCM) operation Rebuild the simulation model described in task 1. Calculate the critical load resistance (.) that set the boundary between CCM and DCM. i. Plot the inductor current waveform showing the minimum value. ii. Now, use THREE times of . and re-run the simulation model again. Evaluate the following: o Plot the input source current waveform and compare it with the current source in task 1. o Show the voltage waveforms across the output resistance, the main switch and diode 1. Task 3: impact of non-ideal components on the converter operation Rebuild the simulation model as in task 1 using the following parameters: Input source () 325 V Ideal transformer 1/2 = 15 Magnetizing inductance = 5 with a series resistance of 0.1Ω MOSFET switch (model level, ideal) Saturation voltage =2V, transistor resistance = 3mΩ, diode forward voltage = 0.7V and diode resistance = 0.1mΩ Diode 1 forward voltage =0.7V and diode resistance = 0.5mΩ Output capacitor = 100 with an ESR of 0.2Ω Duty ratio = 0.1875 Show the output voltage and magnetizing inductance current waveforms and critically discuss your observation with reference to the results obtained in task 1. EEE8147- Advanced Power Electronics and Applications Task 4: RCD snubber design Use the simulation model of task 3 above and add a small leakage inductance of 3% of the magnetizing inductance in series with the transformer primary winding and 15pF capacitor (to emulate the parasitic capacitance, ) across the MOSFET switch. i. Plot the voltage waveform across the MOSFET, and diode 1. ii. Design an adequate clamping circuit that should limit the peak voltage across the main switch MOSFET, to no more than 450V. (you need to show your full calculation. You may add this to the appendix if you struggled with the space) iii. Re-plot waveform to demonstrate your result. iv. Calculate the power loss attributed to the additional clamping circuit. Task 5: Based on the results obtained from Task 4, generate a simple Bill of Materials (BOM) (i.e. as a table) for the main components of the Flyback converter, support your selection with sensible rationale. 3. THE REPORT* The report is limited to 5 PAGES ONLY (excluding title page and appendix) and should contain only:  Title page.  Results.  Calculations (you need to show your calculation).  Discussion and conclusion.  Appendix – add a copy of your SIMULATION MODEL. (please copy and paste your simulation model as a proof that you have developed the model) END OF ASSIGNMENT * Please refer to “report assessment and format” next page for more information EEE8147- Advanced Power Electronics and Applications EEE8147 simulation exercise report assessment & format 1. Assessment Assessment of your report is focussed on the following areas: Conciseness Is your report within the 5 page limit and does the abstract summarise its contents? Report structure and presentation Does your report contain a cover page with abstract, results with interpretation, calculations and discussion & conclusion? Is your report well presented with a clear numbering system for sections, figures and tables and does it use a suitable font and spacing? Data presentation and interpretation Are graphs clear, all axis labelled, multiple waveforms clearly annotated, tables and diagrams clearly presented and summarised in a title or caption? Is all data clearly interpreted? Use of appropriate technical English language Your report should use professional scientific language. Avoid using colloquial terms (“the results were roughly right, more or less 15V….) Avoid writing in the 1st person (I did, my results were….) Analysis, discussion and general understanding Does your report clearly show that you understood the tasks; this is best evidenced by your analysis and discussion of results. 2. Report format and general requirements:  Plagiarism: Do not copy the report from others. If this is detected then marks will be deducted.  Your report is limited to a maximum of 5 pages (excluding title page and appendix)  Title Page– Clearly showing your name (Surname, First name) course code (EEE8147), School, date of submission and a 1 paragraph abstract.  Numbering System -each section, sub-section, table, graph, and diagram should be properly identified and numbered for cross-referencing.  Labelling System – each trace, graph or table of results should be clearly marked not only with axis units and quantities but also the conditions for which the results apply. Annotate waveforms if there is more than one per graph. EEE8147- Advanced Power Electronics and Applications A good report will contain the following sections 1. Cover page Clearly showing your name (Surname, First name) course code (EEE8147), School, date of submission and a 1 paragraph abstract. 2. Results, analysis and discussion This section will provide evidence that you have completed all of the simulation tasks. Include all simulation traces and calculations (if any). All graphs and tables should have a title or caption and use an appropriate axes and scaling. Graphs and tables should be properly labelled and numbered so that reference can be made in the general text of the report. You must interpret and discuss your results. A mere description of results or characteristics does not constitute discussion. Any conclusions that you have drawn from the simulation exercise should be included in this section. 3. The Appendix – will contain a copy of your simulation model. (please copy and paste your simulation model as a proof that you have developed the model)