Hi everyone, I've recently tried boost converters with 3.7v li-on batteries. It will boost the output until you put some load on it, 1k ohm will drop the voltage terribly. So now I've tried it with a power supply. It's not boosting at all. I'm using a 555 timer with 10k var and 4.7k fixed resistor and 10nf and 100nf caps. The boosting part is using 2000uH inductor and shottcky diode with BC337 transistors ... Never mind about the schematic. Whatever I change I get same results. Any help ? I can buy boosters but I hate when I fail making my own stuff.

 

Never mind about the schematic

We need to see schematics to see how components are connected before anyone can help.

 

Never mind about the schematic

Then never mind any help.

 

 

What are the output voltages you are measuring with and without a load?
You 555 is running at a low frequency and the inductor may be saturating.
What is the current rating of the inductor?
Try reducing the 100nF cap to 50nF or less and see if that changes anything

 

Hello,

In the openings post you state that you want to boost an 3.7 Volts Li-ion battery.
In the schematic you show 5 Volts.
The minimum voltage for a bipolair 555 is 4.5 Volts, so the Li-ion battery will not work.

Bertus

 

..... and Vgs(thr) for an IRF540 can be as high as 4V, so the FET may not be turned on fully, or even at all; especially as the bipolar 555 output voltage is always a volt or more below the supply voltage.

 

The schematic shows "one" of the experiments I did. The input is 5.25 and the output is 5.14. The inductor I'm using is the one in pic, idk exactly it's inductance

 

Hi

Why not use a real boost converter chip instead of a 555?

 

Hi

Why not use a real boost converter chip instead of a 555?

I already said that, I love to make my own stuff not to buy them. But now I think I should buy them already

 

I already said that, I love to make my own stuff not to buy them. But now I think I should buy them already

Well.. you would still have to design and build it, except you would use a boost converter chip instead of a 555 chip.

 

http://www.kr4.us/lipower-boost-converter.
html

 

Boost converters don't work well without feedback and your 555 circuit has no feedback.

 

Ok, I've been working the last 3 days on converters and now I think we should use PCBs instead of building converters. I've seen enough fails for now, time to pay some money

 

Hello,

Have a look how it is done on this page:
http://www.dos4ever.com/flyback/flyback.html

Bertus