How can I convert a 17vinDC to 20vout DC?

Hi Fella's

I was wondering again if there is any schematics here that I can use to convert a 17in to 20v out DC-DC converter? Kindly send me a link please.


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lemonie6 years ago

(Another cryptic "try to guess what it is that I'm talking about" question)

What is this 17V thing?
What is the 20V thing?
What are you trying to do with them, i.e. what is the problem?

(I hope this is not a "I have this many LEDs..." thing)

mitchiko (author)  lemonie6 years ago
Hi Lemonie,

I have a solar panel that has a 17v output but in order to use it to charge my laptop I would need at least 20v output. So, I need to step up the 17v to 20v but the problem is I don't know how to do it nor do I see any of it in the DiY shop. I would like to seek your help if you could help me so that I can convert my Laptop to a Solar Laptop because in my provincial house we don't have a continuous supply of electricity.

Do you have any schematics or suggestions how I can do it?

iceng mitchiko6 years ago
It is a great deal easier to Buy or build a second solar panel

and put in series with the first !!   See the image.

Solar 1720V.JPG
mitchiko (author)  iceng6 years ago
Hi Iceng,

The problem is I only have 2 types of solar panel one has a maximum output of 17v and the other is 9 volts if that so I will have 26v should I connect it in series. My Laptop requires 19-20v input, won't it burn my laptop if I connect a 26v?

Or, Can you suggest How can I lower down that 26 volts to the desired voltage?

iceng mitchiko6 years ago
Covering part of the array will let you reduce the total voltage.

mitchiko (author)  iceng6 years ago

Honestly I don't want to do it that way because i could still have the potential to use that 9 volts instead of covering it. But, I would request if you have any other suggestion or Idea where I won't have to do as you say? Cause, I think there would be a lot more potential use instead of covering that panel and reduce its productivity.

I can do some works if you have a design.

iceng mitchiko6 years ago
How much current does your laptop need at 20  VDC  & i can regulate
from 28 to 20.VDC


mitchiko (author)  iceng6 years ago
Hi Iceng,

One of my laptop requires 19v 3.2A and my smaller one needs 19v 1.58 A. I would like to ask for both since I use them both on the province.

I could have different schematics that I can work with should you have the design or it would be best if we can make it in one. I really appreciate your help with me on this and I am happy to have someone like you to help me with my problem.

Thank you again in Advance.
iceng mitchiko6 years ago
The power needed by your lap top is over 60 Watts
Assume 80 Watts to up-verter to 20VDC.

Your solar panel must be approximately 32" x 32" area with an
optimum current 4.5ADC @ 17.5 VDC and weigh 16  LBs with the
support frame.

This is the minimum you will need to power a small up converter to power
the 61 watt lap top ( 19V 3.2A ).

If you have such a panel let me know and we can continue.

mitchiko (author)  iceng6 years ago
Hi Iceng,

Any word about my request?

iceng mitchiko6 years ago
Sorry for the delay.
Here is an inverter I simplified for only your smaller 30 watt lap top from
the 50 watt solar panel at full sunlight.  Can not do 80 or 60 from a 50 w.

Here is a 30 Watt inverter circuit using minimum number of components.
Here use a CD 4047 IC from Texas Instruments for generating the 100 Hz
pulses and two 2N3055 transistors for driving the load. The IC1 Cd4047
wired as an astable multivibrator produces two 180 degree out of phase
100 Hz pulse trains.

These pulse trains are preamplified by the two TIP122 transistors.The out
puts of the TIP 122 transistors are amplified by four 2N3055 transistors  to
drive the inverter transformer.The 20V AC will be available at the
secondary of the transformer. Nothing complex just the elementary
inverter principle and the circuit works great for small loads like a lap top.

  • Notes:

    1. A 17 V solar panel is the source.
    2. Use the POT R1 to set the output frequency to50Hz.
    3. For the transformer get a 12-0-12 V , 5A xfmr.
    4. The modified primary becomes a 20V  secondary.
    5. The allowed out put power is reduced to 30W.
    6. Use a 5 A fuse in series with the battery as shown in circuit.
    7. Mount the IC on a IC holder.
    8. This is a low cost circuit meant for low scale applications.

Design tips:

  1. The maximum allowed output power of an inverter depends on two factors.
  2. The maximum current rating of the transformer primary and
  3. The current rating of the driving transistors
  4. These are only rough calculations and enough for this circuit.
mitchiko (author)  iceng6 years ago

Do I need two solar panels for this since now I only have one 50w solar panel. And this is really a very good stuff I will make this as soon as I am back from my vacation.

Many thanks
iceng mitchiko6 years ago
Yes, but that inverter was modified to power just the low power lap top
when you double the solar capacity, I have to make a more powerfull
up-verter (probably a mosfet higher fq toroid design)...   A
iceng mitchiko6 years ago
Can you rewind a primary ?
Since the output is only 20 volts winding is not critical at all.
Your specifics voltage and current requirements precluded a boost
device or a standard transformer.
It may be easier to wind a toroid transformer, but one must have the core
B-H curve to calculate.

mitchiko (author)  iceng6 years ago

I have 50watt solar panel that has 17v out and 2.87A 670mmx630mm, do you think this could do it? I could still acquire one more of this.

Hi man - thanks for the reply. I was partying yesterday and now I'm very tired - stick with iceng he knows what's what...

seandogue6 years ago
I won't provide schematics, but I will suggest a method.

You can use a voltage doubler to achieve 34V, from which you can step down to 20V.
That's a very narrow range to try and boost. What are you actually trying to do ?