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LM2577 Insanity...

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Rescue1

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Hello all,

So I am messing around with a few of the pre made lM2577 regulator boards from ebay, and they are quite cool and work well. I came up with another unrelated project idea and wanted to incorporate the LM2577 onto the board instead of have a separate premade unit..

So I tried first to perf board this circuit and have had no luck. I followed the spec sheet to the T, and then tried the very slight changes in components the Ebay boards had. I have checked, rechecked, then checked again all traces and wiring, and all I get is a 2577 that gets hot. I've also tried new 2577s with no change. All leads were kept as short as possible, shorted than what was on the premade board. I even tried to remake everything, and again no luck. I am pulling my hair out. I understand it's a hard thing to answer if my circuit isn't in front of you, but if anyone has any experience with building these or other switching power supplies please give any tips.. Thanks for all the help in advance...:)
 
If the thing is getting hot, then check your output for shorts.. The other thing is to check you aren't pulling too much current... Also make sure you have a fast schlocky diode... What voltage are you ramping from and to....
 
Thank you for the replies,

As far as a diode goes I am using a 1N5822 Schottky which was on the datasheet for use with the 2577. I also tried an SS34 Schottky that was used on the premade units and still didn't have any luck.

And in case I didn't mention it the LM2577 is the ADJ model.

The inductor I am using is a ELC-15E101L, 100uH. I also tried the 330uH version of that and the SMD 100uH inductor that was on the premade.

My initial intention was 12 Volts in, and 28 Volts out, but I figured I had better start with smaller voltages to make sure things are working properly and I don't let out the magic blue smoke. So I have 5volts going in, less than that out because something isn't working. I am also not seeing any sort of oscillation on the scope. One would deduce from this statement that something is shorted or wired wrong, but I can't stress enough how many times I have checked. Still scratching my head... :-/
 
Just an update for anyone still perplexed like I am...

So I removed a known working 77 chip from a pre made unit and put it into my board, and viola it worked perfectly and as expected..

So looking at the case there are some slight differences in the font and layout, which makes me wonder if the ones I bought are some China knockoff junk. This has happened to me before with some 2N5686 transistors and they didn't hold their spec'd amperage. They were however from ebay, so you kinda expect things like this. The LM2577's I purchased were from Mouser, which is a very reputable supplier, so I am still left kinda confused. I will probably just drop the whole idea and go with another component as there are many. Any ideas would be appreciated, and thank you all for the help... :)
 
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