Active Clamp Forward Step-by-Step Guide

Transcription

1 Active Clamp Forward Step-by-Step Guide Input specifications: Output specifications: Input voltage: 18 VDC to 75 VDC Output voltage: 0.5 VDC to 12 VDC Switching frequency: 100 KHz to 600 KHz Output current: 1 A to 40 A Output power: 0.5 W to 480 W 1

2 Step 1 Design Requirements Enter your own design input and output specifications. For the input specifications, the minimum, typical, and maximum input voltages can be filled out. The output specifications consist of the output voltage, output current, and switching frequency. The Next button and the Create Design button serve the same function and either one can be clicked once all General Parameters are completed. 2

3 Step 2 Device Selection From the inputs entered in Step 1, Step 2 shows a recommended list of MOSFET solutions for primary, active clamp, and secondary switches. Click to select Primary, Secondary, or Active Clamp. Up/Down arrow buttons sort by FET parameters 3

4 Click to download datasheet and see the details of MOSFET specification Step 3 Analyze The calculated values of the power components, based on the inputs from Step 1, are recommended and these values can be modified based on your own design. And, it is possible to change each MOSFET driving voltage & current and dead time. Click on Run Steady State to simulate your design so that the tool displays a dynamic waveform calculator, Webscope. Waveforms can be manipulated here (e.g., like an oscilloscope). Click here on System Circuit to change simulation circuits. Click on Help for more detailed information of the simulation model. The purpose of the System Circuit tab is to simulate the operation of active clamp forward without the parastic parameters. The Switching Circuit tab contains the parastic parameters such as MOSFET s parastic capacitances & inductances and PCB inductances to show more actual waveforms close to your board conditions. User adjustable transformer pop-up shows primary and secondary turn User adjustable MOSFET pop-up shows FET quantity and PCD parasitic inductance User adjustable primary gate driver pop-up for dead time and driver sink/source capabilities 4

5 User adjustable secondary gate driver pop-up for dead time and driver sink/source capabilities. Simulation results contain input filter, primary switches, secondary switches, and output filter voltage and current waveforms. Click the tab to analyze each of the waveforms. Users can utilize cursor by adjusting the arrow button on the graph or by expanding the waveform using the scope. Waveforms: Use check markers to display/hide particular waveforms, or use the four black buttons: Hide All, Show All, Move Down, Move Up (to expose a waveform hidden behind another). You can zoom into a waveform by clicking on Marquee Zoom, then rubber-band a box around the area you want to expand. To return to full view, hit Reset Zoom (second button from the top). Drag the markers (vertical cursors) to narrow the time interval for waveform calculations below. 5

6 Switching Frequency: To display the switching frequency, drag the markers to enclose exactly one switching period, then change the first drop-down menu from Δt to 1/ Δt. The first number listed below is the switching frequency; the rest remain the differences between the waveform values at the two markers. Cursor Reading: Cursor reading, in the drop menus, (M) means between markers ; otherwise the calculation is performed on the entire displayed waveform. Marker value includes RMS, AVG, MIN, MAX, Peak to Peak and Slope. Marquee Zoom Cursor reading Switching frequency Step 4 Efficiency Step 4 shows total efficiency and power loss graphs and loss pi-chart of each MOSFET. They show the total efficiency and power losses by the increase of the output current as well as by the minimum, typical and maximum 6

7 input voltages from inputs in Step 1. The loss pi-chart is calculated at conditions of typical input voltage and maximum output current. Total efficiency and power loss graphs as increasing the output current have three lines of minimum, typical and maximum input voltage from inputs of Step 1. Power loss calculations of each MOSFET at typical input voltage and maximum output current are broken down. Click here to change the core parameter of transformer. 7

8 Transformer core selection table shows the current core parameters of transformer. It is possible to change the core parameters based on your own transformer conditions. Once entering the new values, click Recalculate Efficiency button to update the efficiency & power loss graph and MOSFET power loss pi-chart. Click here for recalculation when entering new values. 8

9 Step 5 Summary Step 5 summarizes the selected MOSFETs, operating conditions, BOM, schematic, simulated waveforms and calculated efficiency & power loss graph. You can save your design, on our server to return at a later time, and resume working with it. Your design is confidential, accessible only with your login. Click on the PDF button to generate a summary of your design and download or print the summary tab. 9

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