# DC amplifier

Discussion in 'General Electronics Chat' started by dcwildcats, Jan 4, 2014.

1. ### dcwildcats Thread Starter New Member

Jan 4, 2014
2
0
Greetings,
I am new to this forum and this is my first post and I need some assistance.

I have a variable DC voltage source which is 18 volts and 5A nominal. The voltage varies from 16V to 22V with a corresponding change in current (90W). The voltage needs to be boosted by a factor of 2 to 2.5.

Can anyone give me some guidance on what needs to be done?

2. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,500
511
DC-to-DC converter?

3. ### inwo Well-Known Member

Nov 7, 2013
2,435
315
First thought is to start over and redesign the source.

Linear supply?

4. ### matty204359 Member

Apr 6, 2011
105
3
ignoring inefficiency the power will remain constant.

so

P(t) = V*I

P =V(2) * (I/2)

so 36 Volts @ 2.5 Ampere is best case scenario.... assuming no power losses.

if that is acceptable dc-dc converters are available.

5. ### bountyhunter Well-Known Member

Sep 7, 2009
2,498
507
That is the best approach.

6. ### dcwildcats Thread Starter New Member

Jan 4, 2014
2
0
The problem is that this is a solar PV collector and I need to increase the voltage to reach the minimum voltage of the inverter.

Is there a list of sources for DC - DC converters which will have an output which is a multiple of the input voltage rather than a fixed output voltage?

7. ### #12 Expert

Nov 30, 2010
16,664
7,311
That's so strange that the answer is probably "no".
I'd have to ponder a while to think of how to to that.

Edit: Just chop it into square waves and run it through a transformer.

8. ### matty204359 Member

Apr 6, 2011
105
3
that would be the easiest way, but wouldn't there are switching losses on both sides? rectifying to dc and than using an inverter to bring it back to AC seems kinda lossy. PV's aren't exactly known for their efficiency to begin with.

9. ### #12 Expert

Nov 30, 2010
16,664
7,311
Absolutely correct, except you forgot to mention the loss in the transformer.

A little more pondering might come up with a boost converter that responds to the input voltage instead of a steady reference.

10. ### matty204359 Member

Apr 6, 2011
105
3
a multiple of the input voltage seems arbitrary, a cloudy day and it might dip below the threshold of the inverter. I'd recommend a boost converter with an output of what ever voltage is appropriate for the inverter.

and if you really needed a fixed multiple you could use a sensor on the input to change the set point of the output to correspond with what ever multiple is deemed necessary.

Last edited: Jan 5, 2014
11. ### #12 Expert

Nov 30, 2010
16,664
7,311
Cloudy days are going to happen, and night will happen, too. There must be a shut down feature.