Looking for schematic for a power adapter circuit

[Ionvs]

Hello Friends,

Could someone here please direct me to the correct forum for posting the following, thank you:
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I'm looking for a schematic for a power adapter circuit to power/charge a netbook pc via a 12vdc battery, like one of those power bricks made for powering your laptop from your car or boat. One with a fixed, unchanging output voltage, but which allows a range of input voltages.

Input: 11.0 to 16.0vdc or so.
Output: 19vdc, max current 1.58 amps.

Does anyone know of a well-tested stable circuit like this that stays relatively cool under load? And if possible, please let me know what component(s) should be changed (in the supplied schematic) to limit current to the above spec.

Thanks,
John

[boguslaw]

You need to build DC to DC converter.Sorry, can't help much, but I'm also interested how to make one.... Hmm..maybe try this : Cheap Switch-Mode DC-DC Converter | EEWeb

[torpex]

Hi all,

Yes, it would be a dc-dc converter.
I recently worked on a couple of them. Based on the MC34063.
I make a couple of pictures and I'll post it shortly.

[torpex]

Hi all,

This is the schematic that I have followed:


Here the changes for 19v (in spanish)
Cacharreo • Ver Tema - Convertidor DC-DC 12v-19v

I hope that it will help.

[mikrovolt]

you could purchase something like a p2140 for $120
or just buy a ac power inverter for $25 that plugs into the cigaret lighter of a car.

In theory you should'nt need to convert to ac 120V first however cost is related to mass production. going further anyway involves hacking the inverter.

[ewizard]

You'll probably find it far cheaper and easier to just buy something like this (only $19 and I didn't even try finding a cheaper one) on ebay: here on eBay

That will cover exactly what you want even though the potential output current is higher most laptops should have an internal limit for current otherwise there would be a high risk of fire/explosion of Li-Ion batteries by just plugging in a wrong adapter. If concerned about that though you could just throw an LM337T chip across the output and adjust the voltage. That chip will limit current to about 1.5 amps.

Module Properties: Step-up / Boost DC-DC Converter
Input Voltage: DC 10 ~ 60 V
Output Voltage: DC 12 ~ 80 V ( adjustable, O/p Voltage > I/p Voltage by 2V )
Output Current: 10A Max
Input Current: 15 A Max( Under normal circumstances please 12A Current )
The minimum voltage difference: 2V
Output Power: input 12V Max 120W, in 24V Max 240W, in 60V Max 600W ( P=U * I )
Efficiency: 95% Max ( eg input :30V output: 40V 5A n: 93% )

OR Here is one for $7.50 that already has a 2.5 Amp current limit and still covers your voltage I/O needs. Here

[Ionvs]

Hello everyone, and thank you for your kind input; I now have some good info to proceed with.

Admittedly, I like the idea of buying one of those off-the-shelf converters like the $7.50 one suggested by ewizard. Thanks. I do have a more fundamental question though, about that general type (LM2577 or similar) of Dc-Dc Converter: While they accept a range of input voltages, does the output voltage remain fixed even while the source (12Vdc battery) drains, or does the output need tweaking now and then to keep up with a draining source. I do intend to maintain the charge in the input battery (planning to build Alexkor's self-charging circuit with 2SC3552 & UF5408) so there shouldn't be much fluctuation in the supply to the proposed Dc-Dc Converter. I am mostly trying to understand the dynamics of this kind of circuit. Thank you for you kind help.

-John

[plasmahunt3r]

Voltage Doubler using 555

I found this circuit on the internet. You can use a 555 timer as a voltage doubler and then use 7805 regulator circuit with a 14v zener on the #2 pin to regulate 19v out.

When using a zener on the #2 pin, you add the zener voltage to the 5v standard regulator voltage. You are fooling the 7805 regulator.