Author Topic: Specialized Power Supply - Ideas for Design  (Read 843 times)

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Offline LoveLaikaTopic starter

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Specialized Power Supply - Ideas for Design
« on: April 29, 2020, 02:26:44 am »
Hi, first post here. I saw EEVblog's forum, and I wanted to ask for some help. I'm trying to develop a specialized power supply with one output providing 5 volts and another output providing -9.5 V. Each voltage output should be able provide a maximum of 1 amp each, though the load for each output will most likely draw less than that. The input is a 15 volt source, and the output should have 100 mV ripple or less.

When I first designed this, I was thinking of using the LM317 and LM337 for simplicity. However, it became very evident that the two modules wouldn't be able to handle the maximum current load, most likely overheating. After some research, I looked into using some buck-regulators to provide the voltages I need, specifically the LM2596. They seem pretty common, so I designed a schematic based around that, shown in the attachment, if I can get it to work.


I took the base design and added a current limiting feature to the positive voltage. Using a sense resistor, I use some op-amps to read the current going to my load, and a comparator circuit adjusts the feedback pin of the LM2596, lowering the voltage in order to match the current limit given by a voltage source. I'm trying to do the same to the negative output voltage part, but I don't know where to start. Adding a sense resistor as small as 1 ohm causes the output voltage to not remain consistent.

I'm not sure if this is the best design, but it's what I came up with so far. I'm open up to new ideas that would help in improving the design, but so far, this is what seems to work. As a new user, I was wondering if you guys had any suggestions or alternatives that could improve the design?


« Last Edit: April 29, 2020, 05:31:38 am by LoveLaika »
 

Offline Etesla

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Re: Specialized Power Supply - Ideas for Design
« Reply #1 on: April 29, 2020, 02:38:48 am »
Getting .1mV of ripple at full load with a switching power supply in real life is pretty much impossible without extra filtering on the output, and even then that's a pretty crazy specification. Are you sure you need that little ripple?
 

Offline LoveLaikaTopic starter

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Re: Specialized Power Supply - Ideas for Design
« Reply #2 on: April 29, 2020, 05:32:49 am »
Getting .1mV of ripple at full load with a switching power supply in real life is pretty much impossible without extra filtering on the output, and even then that's a pretty crazy specification. Are you sure you need that little ripple?

Sorry, that was a typo. I meant 100 mV, or 0.1 V. I corrected it on the original post.
 


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