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Need suggestions for SMPS ICs for a DIY Lab power Suipply

H

hrh1818

Jan 1, 1970
0
I am looking for suggestions for SMPS ICs for a DIY Lab Power Supply.
Required outputs are:

Output 1
Adjustable over the range of 2 to 15 VDC
0 to 2 amps load current
Adjustable current limiting
18 to 24 VDC input
Output 2
Adjustable over the range of -2 to -15 VDC
0 to 2 amps load current
Adjustable current Limiting
18 to 24 VDC input
Output 3
5 VDC
0 to 5 amps load current
Adjustable current limiting
18 to 24 VDC input
Output 4
3.3 VDC
0 to 5 amps load current
Adjustable current limiting
18 to 24 VDC input

Load Regulation plus and minus 0.5%
Line Regulation plus and minus 0.5%
Through hole mounted ICs preferred

I ask this question because there is an over whelming number of SMPS ICc and maybe another member of the sci.electronics.deign group has some favorite SMPS ICs for this type of application.

Howard
 
R

Robert Macy

Jan 1, 1970
0
I am looking for suggestions for SMPS ICs for a DIY Lab Power Supply.
Required outputs are:

Output 1
    Adjustable over the range of 2 to 15 VDC
    0 to 2 amps load current
    Adjustable current limiting
    18 to 24 VDC input
Output 2
    Adjustable over the range of -2 to -15 VDC
    0 to 2 amps load current
    Adjustable current Limiting
    18 to 24 VDC input
Output 3
    5 VDC
    0 to 5 amps load current
    Adjustable current limiting
    18 to 24 VDC input
Output 4
    3.3 VDC
    0 to 5 amps load current
    Adjustable current limiting
    18 to 24 VDC input

Load Regulation plus and minus 0.5%
Line Regulation plus and minus 0.5%
Through hole mounted ICs preferred

I ask this question because there is an over whelming number of SMPS ICc and maybe another member of the sci.electronics.deign group has some favorite SMPS ICs for this type of application.

Howard

wow, 2A at 15Vdc

If you want great performance and not have to concentrate on the
design, I'd use SMPS followed by the variable SMPS's, followed by
'tracking' LDO followed by the most humongous RFI/EMI filtering you've
ever seen. That way you have efficiency and quiet. Note the tracking
LDO means transitory inefficiency. Once you set the Vdc, the tracking
takes the LDO up near the value and you keep the efficiency but gain
over 10:1 on the output noise.

If you're going to use this as a lab supply, I'd not free run the
SMPS, but use sync mode and then vary the frequency while watching the
effects on the breadboard as a check to make usre the PS is NOT the
problem. It gives you a 'handle' to work with.

I may be preaching to the choir, but WATCH OUT FOR MAGNETIC PICKUP!
Use small loops, copper tape shielding etc. Noise goes around all your
filtering by either capacitive pickup [which pepole understand] or by
magnetic pickup [which most forget about]

I'd concentrate on the vendor:
First, I lean towards Linear as a source of IC's that have support.
LTC1871 use LTspice to see what's going on. Completely simulate the
supply and store with your documentation. LTC1871 I think they have
AppNotes that take these up to 10A.

2nd: National has LM3668, which only goes to 1A, they're support I
found anemic, with their online simulation. To me, I lose control of
the design using tools provided only online.

If you're really brave look at the TI line, I found high quality, and
now they're going after high performance like some really knock your
socks off LDO's.

I hope you come back and share the project with all of us. May be post
it on the DIY website too.
 
H

hrh1818

Jan 1, 1970
0
Hello Robert,

Thank you for sharing your experience and knowledge. However, it is not obvious to me why you recommend using a SMPS with a fixed output as a pre-regulator and connecting the inputs of the variable output SMPS to the output of the fixed SMPS. What advantages are gained by adding a pre-regulator to this DIY Lab supply.

Howard
 
R

Robert Macy

Jan 1, 1970
0
Hello Robert,

Thank you for sharing your experience and knowledge. However, it is not obvious to me why you recommend using a SMPS with a fixed output as a pre-regulator and connecting the inputs of the variable output SMPS to the outputof the fixed SMPS.  What advantages are gained by adding a pre-regulatorto this DIY Lab supply.

Howard

vary the output of the second one.

with the first one fixed, the second one's range of output is
lessened:
input Vac +/15%, including 'brownout'?
input ratio 1.35
output 2:15Vdc?
output ratio 7.5:1

no fixed 'input' ratio is then over 10:1
Yes, not sure why tandem occurred to me, but, this is a lab supply,
one of a kind, and the overall efficiency suffers with two in series,
but blocks with simpler requirements in a system are easier to design
seems better to have a lower ratio, you can count on what's going on.
Especially when you get into current limiting.

Plus, the filtering at the output won't need to get rid of AC mains
modulation, well as much.

When you do design your filtering, watch out for the Zseries to spike
at 'cross-over' The damage that can do is to make you 'think' you have
an excellent filter because the noise you look at on the scope is so
low. But, when you attach an active load with some clock harmonics
right on top of that Z spike; you no longer have a low Zimpedance
looking back into your power supply, you have something like over 10
ohms! and now you can't understand why the BBD is acting wonky. Easy
to use LTspice to see the effect. I've often had to NOT follow the
parts list given in vendors' AppNotes, because that effect was not
looked at. Make your own filtering, and watch out for PCB layout
getting in there. A little bit of magnetic field coupling can undo
your best filtering.
 
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