How to convert AC to specific DC - solar powered laptop

David Kareem: 
 

I'm building a solar powered laptop system and I have a question regarding to elecricity. Solar panel will be source of power which can produce 100W 18-21V 6A of AC. My laptop needs 19,5V 3,33A 65W of DC. How can I connect this two devices and make laptop run on solar power? It would be great to not use any additional battery, because laptop does have its own one.

Thanks for help!

Solar panels usually produce a D.C. output not an A.C. output.

I would use the manufacturer's power supply unit for the laptop to save damaging it. If you can provide  a reliable input Voltage of say 100 Volt to 240 Volts A.C. into the power supply it will automatically provide the laptop with a safe supply Voltage. This can be provided by using a suitable step up transformer if the source is sufficient and can provide sufficient current.

Typical example of a laptop power supply designed for 100 to 240 Volts input A.C.

Or you may be able to get a vehicle power supply unit designed to power the laptop. These may be able to work on 12 to 24 Volts D.C. input  If only A.C. is available then a bridge rectifier will be required to convert the A.C. to unsmoothed D.C. Smoothing may be required by the use of a capacitor, but this will increase the D.C. Voltage somewhat.

Z.

If the panel output really is 18v AC then a normal mains transformer used “backwards” could produce 110 or 240vAC to drive the laptop's existing power unit.

Cost about £25 and exact rating is not critical since most laptop power units work anywhere between 90 and 250v.

Verify the output of the panel with a meter.

 The panel itself will not be AC, but it may have an inverter that converts DC to a chopped waveform that will go through a transformer. It may not be the right waveform or RMS level, an certainly won't be exactly 50 or 60 Hz..

inverting to pseudo mains and then regulating down again is very inefficient.

I'd expect the panel to be stepped down to 12V or 24V battery.

Universal Regulators to supply laptops with the right regulated voltage from  12V vehicle supplies exist.

example here

https://brandedlaptopchargers.com/product/universal-laptop-power-supply-charger-12v-24v-ac-dc-adapter-for-hp-dell-lenovo/

many makers also do a dedicated product.

https://www.lenovo.com/gb/en/accessories-and-monitors/top-tech/65W-USB-C-DC-Travel-Adapter/p/40AK0065WW

mike

Most laptops detect a suitable charger so although its very inefficient, you may have to generate a suitable ac supply as above answers and then use a compatible charger back down to DC

If the panel is rated 100W it will usually produce less, unless you're in a very sunny climate. If the laptop max draw is 65W (what's typical?), then the system is likely marginal, often will produce less power than consumed. So “inefficient” could be bad news. And there's no reason why COTS supplies design for mains or vehicle battery source should cater for less-in-than-out use cases. I guess that charging laptop battery while it's not running is the viable use case, but not actually running the laptop directly off the panel.

I dunno if laptop power use is mostly increased by heavy computing, backlight, or straining wifi?