DC-DC converter 60V to 5V

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I'm planning to add a 5V output to an audio amplifier to feed a squeezebox attached to it.

The amplifier has a +/- 31V supply (62V) total internally to feed the power stage I'd like to use as power source.

The requirements are:
- 62V input
- 5V 1Amp output
- Insulated from input to output

I've found some modules on digikey (http://search.digikey.com/script...) but they aim for 48V input (max 76V).

Any hints on a good converter module for my application ?

Markus

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Just hook the extended input range 5V out switcher to the 31V positive supply in the amp?

Imagecraft compiler user

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The issue is likely to be isolation.

Linear Tech has a very nice line of modules built from their various switchers. Don't know the details, but that would be one place to look.

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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Do you really want a noisy switcher inside an audio amplifier? I think I'd use a LT3439 slew rate controlled push-pull converter. It does not regulate though, so a post-linear regulator is required. But it will be quiet.

Unfortunately, 32V is a bit too high for it.

Can't you just mount an extra 50/60Hz transformer inside it?

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I understand the issue with the noisy switcher inside, especially as there is no shielding inside. Even the cables going across the entire device to the volume button and back to the power amp are not shielded. But most switchers are operation at higher frequencies the audio, so the impact will be limited.

I could probably mount the original transformer inside, there is probably just enough space. The original power supply is a switcher also, though.

Concerning the 30V vs 60V: I'd like to source the 60V, not one of the 30V halfs. Essentially to avoid charging the power supply asymmetrically.

Markus

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With any modern switcher, the frequency will be far above the audio range and easily decoupled. I once made a modem with a switching regulator and got it through the approvals process no problem. You might want to take care with the inductor, mainly by using a toroid or other closed magnetic circuit instead of something with a radiating air gap. This is a job for iron permalloy in my opinion.

The 60V input requirement will be harder to meet. The LT1076 can do it and the 500kHz frequency is in the permalloy range. You would typically want about 100uH in the inductor and for 1 amp output that's about 50 turns on a Micrometals T68-52 core.

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There is no way I'm going to build a switching power supply from scratch for this. Just too much effort for a single instance.

However, the discussion here did revive my neurons. The amplifier actually has two transformers, a small one for the standby circuit and a large one for the power amp. It switches the mains input to the large transformer with a relay. The easiest solution is to add an internal, switched mains plug and plug a suitable wall-wart with the required voltage and amperage into it.

The main goal of the thing is to switch the squeezebox off, when not in use. Thinking about it, the energy consumption is the same if I use 230V directly of take it from the 60V internal supply.

Markus

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markus_b wrote:
Essentially to avoid charging the power supply asymmetrically.

Why is it a problem to load the supplies assymetrically? Aren't they loaded this way to begin with?

(That is actually a question, as it is something that is still troubling me for my projects. A quick pointer/hint is enough, I don't mean to hijack the thread)

edit: And just to add to the solutions, could this be of any use? http://www.ti.com/product/ptma40...

-Pantelis

Professor of Applied Murphology, University of W.T.F.Justhappened.

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pnp wrote:
Why is it a problem to load the supplies assymetrically? Aren't they loaded this way to begin with?

I think it depends on the order of magnitude of things. In this case there is a single transformer with 2 secondary windings in series, supplying the +30V and -30V. The amplifier provides 2x45W output power, so the power supply delivers 90W. These 90W are taken from the 30V rails against each other. If I use power just on the +30V rail, then it will be saturated/overloaded earlier than the other one, potentially distorting my power signal.
In my case, with me drawing around 5W the effect is probably minimal.
pnp wrote:
edit: And just to add to the solutions, could this be of any use? http://www.ti.com/product/ptma40...

Yes, this is similar to the module I found on digikey. It looks like all modules in this input voltage range are built for 48V telecom power.

Markus

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markus_b wrote:
If I use power just on the +30V rail, then it will be saturated/overloaded earlier than the other one, potentially distorting my power signal
Yeah, it makes sence. Thanks for the explanation! I, too, think that 5W is not going to make that much of a difference. Does the squeezebox have any detailed specs on current consumption? Is 1A the typical or the maximum?

-Pantelis

Professor of Applied Murphology, University of W.T.F.Justhappened.

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Quote:

With any modern switcher, the frequency will be far above the audio range and easily decoupled.

Tell that to Alan To:
https://www.avrfreaks.net/index.p...
Quote:
Umm, I do not want to really get into it the ADC thing because it is my own trade secret I use in my design.

In practice, I am ok with something that switches around 100 khz, but it goes against the philosophy of my design.

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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pnp wrote:
markus_b wrote:
Does the squeezebox have any detailed specs on current consumption? Is 1A the typical or the maximum?

I don't know, the device is has 5V 1A on its label. So it probably useful to have some margin.

Markus