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Linear bench supply or SMPS as a second unit?

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Elerion

Member
I own an adjustable linear bench supply (0-30V, 3A), with +12 and +5 fixed outputs.
I want to buy another one, so it is easier to get +/- rails for opamp circuits, and to be able to use in series with mine for reaching at least 60V dc (for audio amplifiers, mainly).

I lean towards linear supplies, just because they are quiter, but honestly I'd rather have a switching supply, for its reduced weight and size.

Very few times I've used a computer supply and also a small "wall plugged" switching supply, and had no problems with them. But they were free.

I know that the effects of the noise from a swtiching supply is probably difficult to predict.

This is why I'd like to ask to veterans:

do/would you have one?

Considering the same budget, do you think is it OK to get a switching supply for audio and RF stuff (and digital too; in other word, for pretty much everything :p )?

Thank you!
 

Cicero

Active Member
Personal opinion, but a second variable linear bench supply hands down. It will just give you that extra bit of flexibility and control.
 

JimB

Super Moderator
Most Helpful Member
For use on my workbench, linear every time.

do you think is it OK to get a switching supply for audio and RF stuff
If "RF Stuff" includes receivers, I guarantee that you will regret buying a switching supply.

JimB
 

schmitt trigger

Well-Known Member
I agree for a linear lab supply, as long as you require a moderate output power.

Once that you require power levels of 100 watts or more, (and this is NOT a hard number), you may consider other alternatives, still linear.
  • The first is transformer tap switching, such that at low voltages and high currents your series-pass transistors do not require to dissipate too much heat.
  • Another is a switchmode pre-regulator followed by a linear.
 

ronsimpson

Well-Known Member
Most Helpful Member
I have some bench supplies that have a switcher to get power off the power line. Then a post linear regulator. This way you have the efficiency of PWM and the noise of linear.
Another bench supply I have uses a hand full of relays to jump the bull wave bridge to different taps on the transformer. (to keep the linear regulator from having too much voltage across the transistor) Saves heat!
 

Elerion

Member
I was expecting that linear supplies would win.

I have some bench supplies that have a switcher to get power off the power line. Then a post linear regulator. This way you have the efficiency of PWM and the noise of linear.
Do you mean a SMPS whose output is regulated using a linear regulator?
I suppose this will still be offensive for things such as receivers.

If "RF Stuff" includes receivers, I guarantee that you will regret buying a switching supply.
 

schmitt trigger

Well-Known Member
There are ways to minimize noise in switchmode power supplies, like operating in the discontinuous or resonant modes.
I would go for the transformer tap change mode.
 

Reloadron

Well-Known Member
Most Helpful Member
I own an adjustable linear bench supply (0-30V, 3A), with +12 and +5 fixed outputs.
Since you are not looking at major current I would duplicate or closely duplicate what you already have. 0 to 30 VDC 3 to 5 Amp linear supplies are relatively inexpensive.

Ron
 

Elerion

Member
Since you are not looking at major current I would duplicate or closely duplicate what you already have. 0 to 30 VDC 3 to 5 Amp linear supplies are relatively inexpensive.
Sure, they are not expensive. It is a matter of weight and size.

I would go for the transformer tap change mode.
I understand. But I'm not talking about building my own power supply (which I do sometimes) but to buy a readily available one. Mine has some kind of relay (I haven't opened ot yet) which triggers at certain output voltages. Maybe it is switching to another transformer tap?
 

Reloadron

Well-Known Member
Most Helpful Member
Sure, they are not expensive. It is a matter of weight and size.
I agree but in your original post you mentioned you had a 0 to 30 Volt 3.0 Amp linear supply. You wanted another similar supply. With a low current supply like this and using this supply as a basic example we are looking at about 16 Lbs (about 7.3 Kilograms) of weight which is hardly heavy and the dimensions of units like this are far from being large.

Size: 11.5" x 6.5" x 5.5"
Weight: 16 lbs

Now if another of what you already have is too heavy or large go with a switch mode supply. I like the linear for low current applications and what you describe.

Ron
 
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