60v to 12v and 9v PSU

[praveen_khm]

Hi,

I generally work on AVR boards which require 5v. However, one of our client asked if we could design him a power supply unit. Haven't agreed anything as I am not sure of the working. Can anybody tell me if below requirement is feasible? If yes, any help is appreciated:

1. Input Voltage: 60V 5A (DC)
2. Output Voltage: 12V and 9V (two different outputs) and load would be up to 3A (DC)
3. He does not want me to use a transformer
4. Does not want any high end stuff as he wants cost to be low (so, slight variation and heat dissipation is accepted)

Thanks,
Praveen

[praveen_khm]

Bump!!!

[Skimask]

Are you really going to use a transformer on 60 VDC?

And did you really bump your own thread after only 50 minutes?

[madires]

I think he'd like to check for some switcher chips supporting around 75V input voltage and 3A output current.

[mariush]

later edit: your thread title says 12v and 9v, but message says 12v and 5v. what's the deal with that?

60v in makes it harder to find cheap regulators, most can accept only up to about 48v.  What's not clear is if you want 12v @ 3A AND 5v @ 3A or just one of them is 3A.

It would be a bitch to solder by hand (ideally you'd use solder paste and hot air gun from the other side of pcb would reflow the large center pad)  but this would do the job for 12v 3A : http://uk.farnell.com/micrel-semiconductor/mic28510yjl-tr/buck-4-5v-to-75vin-4a-adj-28mlf/dp/2096042 
For powering the AVR board (5v at something like 10-50mA) you could use a plain linear regulator like 1117 to keep everything simple. The arduino board may even have something built in.

There's other regulator chips out there, some easier to use (regular soic or through hole) but the majority either do only up to 1-2A or they can only handle 50-60v (which would be too close to your 60v dc input voltage)

[praveen_khm]

later edit: your thread title says 12v and 9v, but message says 12v and 5v. what's the deal with that?

My mistake. I really need both 12V and 9V (and not 5V)

For powering the AVR board (5v at something like 10-50mA)

My AVR knowledge was not really relevant to my question as I am not using this on AVR microcontrollers. Added that stuff to tell you all that I have not had much experience with circuits above 5V.

Are you really going to use a transformer on 60 VDC?

This was the criteria he mentioned though I am not sure. I have used transformer to convert 220V AC and reduce it to 12V. Not sure on DC-DC.

I think he'd like to check for some switcher chips supporting around 75V input voltage and 3A output current.

Yes. Precisely.

[Richard Crowley]

There are plenty of DC-to-DC power supplies out there, even on the surplus market. It depends on the budget whether one of those off-the-shelf solutions would work.

DIY switchmode power supplies (SMPS) are not that easy and generally not recommended without significant experience.  Although there are an increasing number of easier to use ICs for SMPS design.

The 60V source is rather a sticky point. There are plenty of solutions for 48V because that is traditional telco technology.  What kind of an environment has only 60VDC power available?

[mariush]

later edit: your thread title says 12v and 9v, but message says 12v and 5v. what's the deal with that?

My mistake. I really need both 12V and 9V (and not 5V)

So if you need both 12v @ 3A and 9v @ 3A then the easiest solution would be to use two of those switching regulators, like the one I recommended. It may be possible and cheaper to work at making a dc-dc converter that does like 12v @ 6A and then use a linear regulator to get 9v @ 3A out of 12v ... the problem is you'd waste 9 watts (3v x 3A) as heat so you'd need a heatsink for the linear regulator(s) but on the other hand you won't have a second switching ic, large inductor, diodes etc.

BTW. Might want to make a free account at ti.com and then use their Webbench software : http://www.ti.com/lsds/ti/analog/webench/overview.page  It makes designs based on what you input and based on TI made ICs but it's a good starting point... for example for 50-70v in, 12v @ 3.2A (3a with some margin), the system recommends LM5088 and LM5116 , both reasonably cheap ICs and easy to solder and work with.

But you should really encourage your friend to work with a DC input that's lower, let's say maximum 48v. It would make your power supply much, much cheaper as you'll have lots of parts to choose from.

[Kalvin]

TI has simple switcher line of products. For example LM5576 http://www.ti.com/product/lm5576 is rated for 75V input and 6V to 70V output @ 3A for $2.60 in volumes. Other manufacturers may have similar products.

[Zero999]

3. He does not want me to use a transformer

Why not?

A transformer is often part of a switched mode regulator. An oscillator drives the primary and the duty cycle is varied to regulated the output voltage.

Does the secondary side need to be regulated? If not, you could use a Royer oscillator with two secondary windings: one for 9V out and another for 12V out.
http://en.wikipedia.org/wiki/Royer_oscillator

If it needs to be regulated, a buck converter could be added to the secondary side of the Royer oscillator.