CC/CV Benchtop Power Supply Topology Question

[nike9307]

I see, that's an interesting part that I had no idea existed. You also explain it a lot clearer than the app notes I read today about it.

While I was still designing a linear stage, I was trying to battle the saturation problem with components on the inputs and feedback that wouldn't allow for the amps to saturate, but that turned to be rather complex.

For now I'm reevaluating my design requirements given that I have just 2W loss budget. So far I think I'll leaning towards a switching regulator and have some ripple. The alternative is to leave the linear stage, but have less output power.
Nowadays I think that for a general purpose power supply, the output power is more important than noise and as long as the final user understands the tradeoffs and the equipment capabilities, that's ok.
When I'm designing sensitive analog stuff that requires a noise free supply, I tend to generate it on the board, so input noise is not a huge problem.

[David Hess]

While I was still designing a linear stage, I was trying to battle the saturation problem with components on the inputs and feedback that wouldn't allow for the amps to saturate, but that turned to be rather complex.

It gets complicated quickly, so most designs do without even if there would be some performance improvement.  Sometimes you can find example circuits under the subject of "anti-windup".

Plenty of regulators with 50 microfarads or more of output capacitance per amp do not require clamping, but as the output capacitance is lowered, it becomes important.

For now I'm reevaluating my design requirements given that I have just 2W loss budget. So far I think I'll leaning towards a switching regulator and have some ripple. The alternative is to leave the linear stage, but have less output power.
Nowadays I think that for a general purpose power supply, the output power is more important than noise and as long as the final user understands the tradeoffs and the equipment capabilities, that's ok.

2 watts is beyond realistic even for a 30 volt 3 amp switching regulator.  Without heatsinking, a TO-220 package is good for about 2 watts.

When I'm designing sensitive analog stuff that requires a noise free supply, I tend to generate it on the board, so input noise is not a huge problem.

That is usually the way to go.  Or for development purposes, a low noise 500 milliamps or less, isolated +/-20 volt dual tracking bench supply is useful.  I have a couple of old Tektronix PS503As for this purpose.  If I need higher power for a single supply voltage, like for motors, then I use a frame power supply.

[PCB.Wiz]

Currently my biggest problems is the loss budget. Given that its only around 2W, I'm considering going to a fully switched architecture, without a linear stage. This will add output ripple, but it will stay small and quiet.

Some parts have a pin to select PWM or PFM mode, and TI have some that spec a loop designed for additional ferrite bead filter, that should lower noise more.
You could also have a lower current LDO in the box, not intended for continual high power, but useful for A/B noise comparison.


Addit : Here is TI link
https://news.ti.com/2020-10-21-Industrys-first-low-noise-buck-converters-with-integrated-ferrite-bead-compensation-simplify-high-precision-designs
Seems they have only 17V in switchers, models from 2A thru 8A, plus a couple of integrated inductor modules 2A & 3A using those parts.

[nike9307]

Some parts have a pin to select PWM or PFM mode, and TI have some that spec a loop designed for additional ferrite bead filter, that should lower noise more.
You could also have a lower current LDO in the box, not intended for continual high power, but useful for A/B noise comparison.


Addit : Here is TI link
https://news.ti.com/2020-10-21-Industrys-first-low-noise-buck-converters-with-integrated-ferrite-bead-compensation-simplify-high-precision-designs
Seems they have only 17V in switchers, models from 2A thru 8A, plus a couple of integrated inductor modules 2A & 3A using those parts.

I took a look at those. They look pretty awesome, but the low voltage rating is not going to work for me. I need 24V