how would i get started designing an 11V to 15V DC output, AC/DC (wall power) switching power supply? so with a pot I can adjust the output voltage. output current is about 1.5A. drives a motor.
any ideas on how i can get started with this? where to look for circuit possibilities?
Um, you start by buying one, because it sounds like you should be the last person to be playing with mains voltage.
With that range of output voltages you may be able to buy one -- many 'fixed' output supplies will allow some adjustment, you may be able to find a 15V supply that'll squeak down to 11, or a 12V supply that'll go over that range.
-- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" gives you just what it says. See details at http://www.wescottdesign.com/actfes/actfes.html
I found something thats nice, but not AC/DC..its the National LM25576 buck regulator which I can just put an off the shelf 24V supply in front of, and its meant to be adjustable in my voltage output range, and they have the online webbench which built the entire circuit for me and i bought an unassembled kit from!
where do you people come from? how do you think anyone learns how to do anything? you think i would be the first person to try making my own AC power supply?
Designing and building a switcher from scratch is generally not recommended as a "first project". It is definitely _NOT_ a beginning- level project.
Now, if you want to walk before you try to run, you could build a linear supply - get a suitable transformer, rectifier, filter, and, for example, an LM317 with suitable heatsinking and probably a pass transistor.
If your goal is to learn how to build switching supplies, I'd suggest your first step (after you've mastered Basic Electronics) would be to buy a book about it.
If your goal is to have an adjustable bench supply, then either buy one of build a linear.
Good Luck! Rich
I found something thats nice, but not AC/DC..its the National LM25576 buck regulator which I can just put an off the shelf 24V supply in front of, and its meant to be adjustable in my voltage output range, and they have the online webbench which built the entire circuit for me and i bought an unassembled kit from!
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I would suggest looking at some of the Linear Technology parts, and using their "jigs", which are reference circuits for each of their switching regulators or other parts. Examine the waveforms carefully, both during startup and after the output becomes stable. Play with inductor values, frequencies, and various combinations of input voltages and output loads.
Then, when you have a better understanding, you can order some parts and actually build a circuit. You can make it work on a perfboard, especially if the frequency is 50 kHz or less, but a real PCB is better, and layout is all-important and non-trivial. You need to understand how a couple inches of copper can act as a significant resistance and inductance that can cause instability and inefficient operation. There are tradeoffs regarding MOSFET size and RdsOn and gate charge and switching losses due to the gate driver.
I have learned a lot with my recent design of a 12 VDC to 50 VDC at 40 watt switcher, and my latest batch of PC boards still have some problems that are caused by a combination of suboptimal layout, thinner tracks than specified, and inefficiency caused by inadequate gate drive that did not show up in the simulation. I added a hefty gate driver and boosted the efficiency from about 75% to near 90%. The simulation showed about 93% or better.
Your project requires working with AC mains voltages, which can be dangerous not only in terms of shock, but also because of the amount of power that can be supplied to an overloaded component, which can cause an explosion that could put out an eye or cause other bodily harm. Wear goggles and use a low current circuit breaker or fuse to limit the power. Enclose the higher power circuitry in some sort of enclosure.
If you go with a front-end supply of 24 VDC, you will be a lot safer than working directly on the mains. You can get a wall-wart computer supply very cheaply, and then build the rest of the design as you need.
Good luck,
Paul
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s e T . t yThanks Paul! I really appreciate your answer that did not involve "dont do this"! Way to keep this group alive!
Good luck. Don't hurt yourself.
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