Please rate this psu design

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I'm no electronics expert, but i do have a couple of ideas/tips, whatever you want to call them:


1) I think that bypassing the adjustment pots with some caps may well help with bringing down the noise (as per the LM317/337 datasheet

2) Arent those 100V caps just a *bit* overkill, given that you have a maximum of 48V DC? I'm thinking that some 63V caps would work just fine before the regs, and some 35-50V ones after, and this would be based on bulk and cost.



Chris
 
Hi,
the floating three pin regs (317 etc) can work at much higher than 35V. That is the input to output pin limit.
The problem is at start up when the output is discharged (zero V) and the input suddenly rises to maximum in a few mS. A big cap on the output makes this worse.
Similarly, the adjustment could take the output pin very low and exceed the differential limit.
 
Yes Andrew quite correct,
I also saw that they tend to specify a delta V different to a normal vin
Max. The 317HV will do 60V but the 337 will only do -50 V which is a bit close to the -48V input.
In short the design seems a bit stressed (also considering the not unsubstantial dissipation the pass elements are subjected to).
 
Disabled Account
Joined 2006
I agree that it needs adjusting as has been stated above (... lower input voltage to regulator for lower volt drop across [and hence lower dissipation in] the regulator, adjust the cap values, add a cap across the adjustment resistor). Also the regulators and op-amps may need heat-sinks.

However, the overall concept is right.
 
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