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Kchula-Rrit

19V laptop adapter as TI power?

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I've been mulling this idea for a while to power a TI.

 

I have several 19V power bricks, including some 12V car adapters, from deceased laptops.  If I could set a ground at +6V relative to the negative lead, I could use a LM7905 to generate the -5V.  The +6V "ground" would give me 13V to feed a LM7812 to give me +12V, and a LM7805, maybe through a dropping resistor, to get +5V.  A diode bridge would drop the voltage, hopefully without generating so much heat.

 

Do power bricks have floating outputs?

 

K-R.

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Good point.  I think the 78XX/79XX requires a couple of volts difference between input and output to work.  Sigh.  If I could find a +12V to -5V converter, that would take care of the headroom problem.  I'm poking around the Digi-Key site anyway, so I can take a look...

 

K-R.

 

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13 hours ago, Kchula-Rrit said:

I've been mulling this idea for a while to power a TI.

 

I have several 19V power bricks, including some 12V car adapters, from deceased laptops.  If I could set a ground at +6V relative to the negative lead, I could use a LM7905 to generate the -5V.  The +6V "ground" would give me 13V to feed a LM7812 to give me +12V, and a LM7805, maybe through a dropping resistor, to get +5V.  A diode bridge would drop the voltage, hopefully without generating so much heat.

 

Do power bricks have floating outputs?

 

K-R.

Take a look at TI’s line of LDO voltage regulators. They come in a wide variety of capacities and features like low ripple. 
 

Use an op amp in inverting configuration. This gives you a virtual ground and Vout = -Vin 

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On 7/20/2020 at 10:15 AM, FarmerPotato said:

Take a look at TI’s line of LDO voltage regulators. They come in a wide variety of capacities and features like low ripple. 
 

Use an op amp in inverting configuration. This gives you a virtual ground and Vout = -Vin 

I found a LM675 power op-amp on the Digi-Key Web site.  It puts out 3 amps.  Have to order a few for experiments.

 

They also stock regulators that have a 0.75V drop-out.

 

K-R.

 

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