Hi everyone,
I want charge a 35v electrolyte capacitor around 1000 uF by switching a MOSFET like irf840 between 0 to 20 volts of an 220v AC power. I don't want use micro controllers to measure AC voltage and switch the MOSFET.
I khow I have to protect the MOSFET by a 0.5 ohm, 5 watts resistor after a full bridge using 1n4007 diodes but I don't know how without coding on micro controllers.
The porpus is charging the capacitor 100 times per second on the 20 volts.

Thanks a lot.

 

This is a dangerous and foolish plan.

If You would explain the whole end-goal of the project.
I'm sure that You would receive many, better thought-out, and much less dangerous, suggestions.
.
.
.

 

This is a dangerous and foolish plan.

If You would explain the whole end-goal of the project.
I'm sure that You would receive many, better thought-out, and much less dangerous, suggestions.
.
.
.

Thanks for your quick reply...
I Wana a 400 ma, 5 volts transformer less power supply. I have a very small space and around 1$ cost.

 

Thanks for your quick reply...
I Wana a 400 ma, 5 volts transformer less power supply. I have a very small space and around 1$ cost.

Fuhgeddaboudit. Contradictory and unrealistic requirements.

 

Fuhgeddaboudit. Contradictory and unrealistic requirements.

I won't give up...

 

This is a dangerous and foolish plan.

If You would explain the whole end-goal of the project.
I'm sure that You would receive many, better thought-out, and much less dangerous, suggestions.
.
.
.

Forget about it's danger! I Wana improve my knowledge, at least.
Could you please learn it to me?

 

That's a great attitude to have,
but You, or someone else, could wind-up DEAD because of it,
so care must also be exercised.

There have been many great Engineers, that have come before all of us here,
that have come up with ingenious ideas, that are practically free for the taking.
You really should take advantage of this fact,
because so far, You know just enough to be dangerous.
Wait ~10-years and You will start to realize how true this is.
.
.
.

 

That's a great attitude to have,
but You, or someone else, could wind-up DEAD because of it,
so care must also be exercised.

There have been many great Engineers, that have come before all of us here,
that have come up with ingenious ideas, that are practically free for the taking.
You really should take advantage of this fact,
because so far, You know just enough to be dangerous.
Wait ~10-years and You will start to realize how true this is.
.
.
.

Thanks a lot for your kind alerts bro. I understand how many experiences are behind your knowledge to stay safe. But I'm not that much noob! I'm working with AC power for more than 20 years since I was just a kid. I use epoxy resin to cover all parts of transformer less power supply to protect humans and also use varistors and fuses to protect boards.
Any way I'll find the way.
Thanks again

 

What's so terrible about using a High-Frequency-Switching-Power-Supply with Transformer Isolation
like everybody and their grandmother currently uses ??????
For less than ~$1.oo each.
.
.
.

 

What's so terrible about using a High-Frequency-Switching-Power-Supply with Transformer Isolation
like everybody and their grandmother currently uses ??????
For less than ~$1.oo each.
.
.
.

The competitive advantages of my new product are: low weigh, low cost and small size.
Good luck

 

The competitive advantages of my new product are: low weigh, low cost and small size.
Good luck

Your product will need to adhere to the Product Safety standards of the market it is sold into as well as transient, ESD, EMC, etc. IEC 61000 standards for the EU, similar for India and others, UL and FCC for the U.S.A. and Canada.

An example test is IEC 61000-4-5 Surge where a typical test is 1 kV line-to-line from a low-impedance waveform generator. 2 kV line-to-GND.

https://www.ametek-cts.com/know-how...rical,from switching and lightning transients.

Product compliance testing runs into thousands of dollars and tends to act as an entry barrier for small companies without deep pockets.

 

Tha

Your product will need to adhere to the Product Safety standards of the market it is sold into as well as transient, ESD, EMC, etc. IEC 61000 standards for the EU, similar for India and others, UL and FCC for the U.S.A. and Canada.

An example test is IEC 61000-4-5 Surge where a typical test is 1 kV line-to-line from a low-impedance waveform generator. 2 kV line-to-GND.

https://www.ametek-cts.com/know-how/iec-transient-pulse-immunity/iec61000-4-5-surge#:~:text=This test is for electrical,from switching and lightning transients.

Product compliance testing runs into thousands of dollars and tends to act as an entry barrier for small companies without deep pockets.

Thank you for your nice information dear dovo.
First I have to made it, right? Those are next steps.
It was easy for me to hire a freelancer to do the job, but I came here to learn some new analogue techniques.... wrong idea!
However I'll reply the answer here to help someone else to find out the technical answer.
Thanks everyone

 

I remain less than sanguine about your prospects, and hopefully that will save you some peril and grief.

 

I Wana a 400 ma, 5 volts transformer less power supply. I have a very small space and around 1$ cost.

Use this one 5 V 500 mA for $ 0.26 ($ 0.63 shipping)


Or that for $ 0.47 (($ 0.40 shipping))

 

I remain less than sanguine about your prospects, and hopefully that will save you some peril and grief.

You are so kind bro....
"If People Are Not Laughing At Your Idea, Then It's Not Big Enough!"

 

Use this one 5 V 500 mA for $ 0.26 ($ 0.63 shipping)
View attachment 322948

Or that for $ 0.47 (($ 0.40 shipping))
View attachment 322950

Thanks for your suggestions...
I know this modules. The price and performance are ok but it's bigger than my space. I tried old tiny iPhone charger too, even without the case but that wasn't also small enough.
There's some good news, It seems I'm finding the way

 

400 mA is very high for a transformerless supply. Normally, a capacitor is used to drop the voltage. For 400 mA, that capacitor will not be small.

What you are talking about is a buck converter running off the line directly, not the usual transformerless supply.

Why 20V if you need 5V? To drop 20V to 5V at 400 mA with a linear regulator, you will need to dissipate 6 Watts. The heat sink will be bigger than modules and will require air space around it.

As stayed, I don’t think your idea is practicle.

Also, it is not just the power supply that needs to be insulated from the user, it is anything powered by it.

 

Such a switch-mode supply is commercially available. Check DigiKey