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DPS3003 Power Supply - AC/DC Converter + Output Filter
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MAntunes:
Hi guys,

I'm designing a small bench power supply using the DPS3003 module.
I have a 24VAC transformer and some big capacitors and I want to use them so I'm designing an AC to DC converter using a LM317.
I'm regulating the output to 32V so I can use the full DPS3003 module's voltage range.
I don't think I'll be using currents higher than 1A but do you think I should add series pass transistors to handle higher currents, just to be safe? The datasheet recommends a 2N2905 and a TIP73, but are there any alternatives? My local electronics store does not have these.
The current schematic is in attachment.

Also, I'd like to design an output filter to remove the higher frequencies of the switching converter, but I don't know where to start. A LC filter would be enough? Or would an active filter be better?

I'll be posting the updates in this thread so everyone can check on this project's progress.

Thank you,
Miguel
StillTrying:
"I have a 24VAC transformer and some big capacitors and I want to use them so I'm designing an AC to DC converter using a LM317.I'm regulating the output to 32V so I can use the full DPS3003 module's voltage range."

The first 3 sites I looked at all say the DPS3003 can have up 40VDC input, so I don't see how the LM317 is needed, just the bridge and caps ?
thedoc298:
Skip all that and just connect the bridge>cap to the dps3003 input and let it do the rest. As StillTrying also mentioned.
spec:
Hi MAntunes: interesting PSU project.


--- Quote from: MAntunes on December 28, 2018, 11:07:34 pm ---I'm designing a small bench power supply using the DPS3003 module.
I have a 24VAC transformer
--- End quote ---
What is the secondary current rating of your transformer?


--- Quote from: MAntunes on December 28, 2018, 11:07:34 pm ---and some big capacitors and I want to use them so I'm designing an AC to DC converter using a LM317.
--- End quote ---
As the other members say, an LM317 stage is not required. In fact it would limit your output voltage range considerably and would add heat and unnecessary complication. I like your nice neat schematic though. :)


--- Quote from: MAntunes on December 28, 2018, 11:07:34 pm ---I'm regulating the output to 32V so I can use the full DPS3003 module's voltage range.
--- End quote ---
Afraid you will not be able to get an output of 32V with a 24V AC transformer. If you let us know the secondary current rating of your transformer and the maximum PSU output current that you want, I will work out what your maximum output voltage can be.


--- Quote from: MAntunes on December 28, 2018, 11:07:34 pm ---I don't think I'll be using currents higher than 1A
--- End quote ---
Can we take it that the maximum current you want is 1A?


--- Quote from: MAntunes on December 28, 2018, 11:07:34 pm ---Also, I'd like to design an output filter to remove the higher frequencies of the switching converter, but I don't know where to start. A LC filter would be enough? Or would an active filter be better?
--- End quote ---
There are standard techniques to reduce switching noise. I would not think that an active filter would be necessary or desirable.

The 1N400x type rectifier diodes in your schematic are not the best for this application. I can recommend a better type if you like.
nsrmagazin:
I don't mean to offend you, some consider this description right, but its very wrong to me.

Please don't do this: "I have 24VAC and 32VDC". The right way would be: I have "230VAC RMS" lowered by a transformer to "24VAC RMS", from where I get "24*1.4 = 32VDC". When I remove the voltage drop over the diodes and other components I get.......

Also please provide a circuit, so we can tell you more. The voltage regulator is useful, but you may need to make LM317 as a current and voltage regulator setup. Sometimes the load can drain a large current and burn your circuits. You will certainly need a heatsink for the LM317 for this current. You have "3V over the LM317 * 1ADC == 3W".

EDIT:
The transistors that you are looking for are 2n3055(NPN) and 2n2955(PNP). You should calculate will they need a heatsink.
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