Charging a Laptop from a Car Battery - DC Laptop Charger Circuit

The following post explains a simple circuit which may be incorporated for charging a laptop while driving in car or some other vehicle. The circuit runs without incorporating an inverter or inductors in its configuration Let's learn more.

The good thing about this circuit is that it does not  rely on an inductor topology for the required actions, making the design simpler, and yet effective.

As we all know a laptop runs using a DC potential from an in built Li-Ion battery just as our cell phones do.

Normally we utilize a AC DC adapter for charging a laptop battery in homes and offices, these adapters are actually SMPS power supplies rated with the required and matching specs of the laptop battery.

However the above power supply units work only with AC supplies, and in places where an AC outlet may be available. These units will not work in places where an AC source is not present such as in cars and other similar vehicles.

A novel little circuit presented here will allow a laptop battery to be charged even from a DC source such as a car or truck batteries (12V). It's a very simple, cheap, versatile and universal circuit which may be dimensioned for charging all types of laptops by adjusting the relevant components provided in the circuit. It's a simple plug and play charger circuit.

Normally most of the laptop adapters are rated at 19V/3.5Amps, however some may be rated at higher currents for facilitating fast charging.

The discussed circuit has a voltage adjustment features (via PWM) which may be suitably adjusted as per the required  specs.

The current may be suitably safeguarded by adding a 3 ohm 5 watt resistor at the output positive terminal.

As can be seen in the circuit diagram, the design is basically a powerful DC to DC voltage doubler circuit which utilizes a push pull mosfet stage for the required boosting of the voltage.

The circuit requires an oscillator stage for initiating the proposed operations which is configured around IC1a.

The components R11, R12, C5 along with the two diodes becomes a neat little PWM controller which sets the duty cycle of the entire circuit and can be used for adjusting the output voltage of the circuit.

Typically the circuit would generate around 22V from a 12V source, by adjusting R12 the output may be tailored to an exact 19V, which is the required laptop charging voltage.

Swagatam Majumdar

Hi Friends, Welcome to my site, a place where you will discover a massive collection of electronic circuit ideas, mostly requested by the dedicated readers and exclusively designed by me for their customized application needs. I have posted more than 1100 circuit designs in this site, if you have a personalized circuit requirement you may feel free to request it through the comment box, if it seems feasible to me then surely you may find it published here with your credentials attached in the post, thanks and please keep reading>

1. a long ago i had asked you for this circuit idea... thank you .

1. yes I remember, the article is inspired by your suggestion only.

2. Can you please post the mobile charger circuit with 12v&5w solar panel...
I've the circuit but if you give one more circuit I'll be more confident about that project sir...
Thankyou sir...

1. you may try the following circuit, it will work:

3. Is this suitable for all kinds and sizes of laptops?

1. yes all laptops with voltage around 19V.

4. would u be able to design a circuit for 16 volt IBM thinkpad laptops?

1. R12 in the above circuit may be suitably adjusted for getting any required voltage between 15V and 22V

5. thanks for the circuit... :P

Maybe It will take some time to make it as i am confused with some symbols... :/

1. you are welcome

6. thanks for the circuit, but ic3 40106 is not available in our local market. Please help me

1. you can try 7414 IC, but it will require 5v for operating so replace R1 with 7805 IC

7. I am facing problem in assembling this circuit... many of the ICs have 3 connection in the picture but actually there are 8...

I am so confused... Plz help...

1. use only those pins which are used in the diagram, and leave the rest which are not used.

8. Hi
Great circuit, exactly what I am looking for to power a laptop in a boat, does anyone out there have a PCB design before I go through the pain of designing one ?

Ian Sturland

1. Thanks!

I would suggest that you first build it over a veroboard or a breadboard and verify the circuit functioning, after this you can go for the final PCB designing.

9. hi..sir
i am from indonesia

keloko86@gmail.com

1. No PCB layout for this, sorry.

10. Hi Swagatam

What are the functions of C3 and C4?
Isn't 100uF for C2 enough? C3 & C4 in parallel with C2 will just increase the capacitance by 200nF,

1. Hi Abu-Hafss,

Smaller value capacitors quickly charge and discharge, so are better suited for high frequency disturbances, therefore all these caps have slightly different roles as far as filtration is concerned.

11. Hi am designing Charging control circuit for laptop using solar panel & 12V battery ..so can you briefly explain the curcuit you shared which may help my design..

1. You can use the above circuit for your application, a detailed explanation can be seen here:

Alternatively you can also try the following circuit for the same:

2. Do you think i can replace battery with some cap..since i wanted to reduce the system cost..

3. what kind of cap??

4. Electrolytic

5. how can a capacitor be used in place of a battery...i did not understand your point.

12. Capacitor also functions as Storage device..if we use large value of Cap can't we replace battery with that ..

1. you will require millions of microfarads, and spend thousands of rupees to make a 12V 7.5ah equivalent capacitor battery.

13. Hi Swagatam

Here is modified Voltage Doubler circuit, the output is about 19V.

https://dl.dropboxusercontent.com/u/20969135/Voltage%20Doubler.gif

When a load (laptop) is applied the voltage drops to less than the input voltage.

Can you please explain why we could not get high current output when the original 13.5V battery source is directly connected to the diode D1?

1. Hi Abu-Hafss

The voltage doubling is entirely the function of the capacitor reactances and input power sources.
Therefore if the load calls for relatively higher current would result in an instant drop over the excess voltage being achieved from the cap reactance and in turn will result in a voltage level just equal to the supply, in fact about 1.2V less if schottky diodes are not used.

14. if the parts list is provided it would be very helpful.

1. please click the diagram to enlarge, all the parts are indicated in the diagram itself.

15. Great creativity comes from the minds of great people.

If you do not mind, I need some help.
I need a dc dc converter schematic for a project to install a PC in my car.
In other words, the ATX PSU 12VDC input.
If possible, Schematic and Part List.

1. Thanks Zukarnai,

I could not correctly understand your requirement, are you referring to an inverter circuit that would allow 12V to 220V conversion, for operating your PC??

please clarify this, I'll try to provide an appropriate link for the same.

16. I have tried to simulate this circuit on Proteus but it couldn't be able to simulate due to complexity in circuit ! Anyone one of you have tried this circuit in vero board if yes then I'll go for it as well

17. I just me or rezistor R2 is missing?

1. yes R2 appears to be missing or differently numbered, I think R11 should have been R2...never mind the circuit is not affected anyway by this typo