DC - DC convertor

[michelrietveld]

Just thought it would be interesting to share this.
I have a blue 1 W which has a driver that powers the laser (analog) and feeds the tec cooler.
For 1 W output i have to supply 5.75 Volts.

At the moment i use a 5 V power supply which can be adjusted +/- 5% with a potentiometer but this is not enough to supply the needed voltage.

Since i also have +12V and +/-24V availlable i thought of the following solution.

There is a dc - dc converter availlable for about 12 euros

Type number : OKR-T/6-W12-C
http://nl.mouser.com/ProductDetail/M...sBJ0tQnQ%3d%3d


I have 12 V and need 5,75 (V out)

According to the datasheet the formula is:

R trim (K ohm) = 1,182 / (V out - 0,591)

(5,75 - 0,591) = 5,159

R trim (K ohm) = 1,182 / 5,159 = 0,2291 K ohm = 229 ohm

So if i put two E24 resistors in parallel

240//4k7 = 228,3 ohm

240//5k6 = 230 ohm

This could be a solution to my needs.

Agreed? Suggestions?


Michel
Utrecht
Netherlands

[dilbert]

If your powering a blue & TEC with this make sure 3A is enough...... What does the TEC pull?

[Solonar]

I would just select a common R value that gives you >5.75V rather than trying to get that exact value. 220 ohm should do it.

[steve-o]

Dropping from 12 to 5.75V @3A will give you 18.75 Watts which exceeds the device's design limit unless I missed something.

[dilbert]

Thats my point - while OK for just the blue I doubt it can do the TEC at the same time as most tecs are quite current hungry.

Dropping from 12 to 5.75V @3A will give you 18.75 Watts which exceeds the device's design limit unless I missed something.

[steve-o]

Maybe a buck converter. Those are pretty efficient, and come in various flavors.

[j4cbo]

Dropping from 12 to 5.75V @3A will give you 18.75 Watts which exceeds the device's design limit unless I missed something.

The module he linked is a step-down buck converter, not a linear regulator. Take a look at the datasheet.

It's rated for 6A output but 30W max, so at 5.75V out you'd not want to pull more than 5A or so. Whether that's enough depends on your particular TEC.

[steve-o]

I didn't say that it was a linear regulator. I stated that the design parameters might be exceeded and the device might fail the needs of the application, depending on the power requirements.

[michelrietveld]

i will measure the current at 5V to see how much the tec and driver need.

Michel

[j4cbo]

I didn't say that it was a linear regulator.

Uh, the calculation you gave ((Vi - Vo) * I = Pd) is only applicable to linear regulators.