Advice for newbie

[krish2487]

Hello to all..
I frequently go through the forums but do not post very often.
I am a engineering undergrad.

i wish to build a high frequency power supply.
But i am lost as to how to get there.

i have built smaller switching power supplies running off 6v and 12 v batteries till about 25 w using the likes of MC34063

now i wish to get serious and build something of a decent power and size and offline.

I go through the forums and i see people with absolute command over the subject.
how do i become like you guys??

do i go through the datasheets and hit on a trial and error method??
or do i first try discrete methods??
go through books and implement what the author has given as examples??

Please help.

[yourownfree]

I am not the best on the subject, but intend to do the same. My problem is money, even a small amount. I can tell you all you need to do is break down any diagram you have seen and then know how it works. This is how I think:
What is the power I want to get out of it full duty. what frequency do I need?
If it is just for lights or electronic equipment too. The reason to me is, from what I understand if you raise the frequency to say 400 Hz then the transformer can be a smaller size one in wattage compared to one needed say for 60Hz. The frequency now needs to be generated, and by how. Many methods, 555 timer with appropriate circuitry to follow to activate the final output mosfets. or maybe use a simple transistor oscillator driving mosfets or even transistors. More power means you need everything in the final output to add up to more than what you need due to efficiency etc. I personally am looking at high power mosfets with a voltage rating high enough for my circuit.
The wattage of my circuit will dictate how many mosfets I will need. The current capability is also a factor. I also will have to keep them cool with a good heatsink. Dont forget the amperage is going to be huge at 12 volts. Use Ohms Law. Dont go overboard for your first real big one. I think you will have to come up with what you think will work looking at other work and the specs to parts that are available to you. That way you can make something with stuff you might already have. Or buy what you need. Build it, test it, and improve on it until you get it right. Then you will have the know how to make a better one. By the trials you come up against is what will make you more knowledgeable. Think about it though. If you want a 400 watt inverter you will need 33 amps available. search the net for power inverter schematics and check them out. what frequency were you thinking about? and what power?

[Itsmee]

My advice would be 'Don't re-invent the wheel', most ideas have already been thought of, look around for what you need.
Most desktop computers have a 500W HF switching PSU, and there cheap, make the required adjustments for control and scale up the driver/output/heatsink for continuous output.
If you want a wideband linear PSU, then you need a good DC amplifier, an amplifier is a controled PSU, and PSU's are oftern amplifiers. and yes, I'ts how you look at it, as to what it is, or what it will be.

[krish2487]

thank you itsme and yourownfree

i am presently a trainee in a power electronics company
i have a little experience in PIC MCUs
My present aim is to build a power factor corrected DSP based high frequency sine wave inverter for capabilities upto 5000 Watts.

My hands on working knowledge is almost good for nothing in power electronics at these power ratings
hence i wanted to go one step at a time

first i wanted to make a offline high frequency PSU which boosts the line voltage to +-380V.

then create a switching power inverter by modulating a 20Khz or so signal to a 50/60 Hz signal to drive the Mosfets of a H bridge.
First do it with a square wave then slowly make it quasi sine wave and eventually pure sinewave.

then implement Power factor correction

and then implement the battery bank part.

Then after the system is working implement the same functionality using a DSPic.

I am not asking for schematics or websites.
But i do wish to become good at Switched mode power supplies but am lost as to how to get there.

Any suggestions on how do i get to the destination

suggested readings, exercises, products??
anything at all that makes me good at what i am

[krish2487]

correction

anything that makes me good at what i want to be.

[ChrisA]

Originally Posted by krish2487

thank you itsme and yourownfree

i am presently a trainee in a power electronics company
i have a little experience in PIC MCUs
My present aim is to build a power factor corrected DSP based high frequency sine wave inverter for capabilities upto 5000 Watts.

5000W DC to AC inverter? Think about class "D" audio amps.

Make a digital 4 to 6 bit counter that outputs a digital sine wave. The digital value controls the "duty cycle" or pulse width of a high powered switch. Then this is sent to a passive band bass filter.

Fancier versions that are regulated measure the analog output voltage and feed this back the digital controller where the controller can adjust the amplitude or shape of he digital sine wave to cancel error.

[yourownfree]

huga monga holy crud Batman! 5000 watts? OK now. I can see why you dont try, error. but on a small scale you could, to get all the freq's right, and all dialed in then work on the output stage. Start with 500 watts and if it works right then make 10, 500 watt bricks and combine them or 5, 1000 watt. That way if something happens to the units output you could just run on reduced power while you fix one of the plugin units. If you make one big one and it quits, you are done until you fix it. all the stuff you want, can be built as the driver unit section, and the output as the output section, or make as many sections as you want. If one quits, you just unplug and replace. Makes sense to me anyway. You need to turn yourself into a computer and gather all the info you can on the subject until you feel you are ready to take the training wheels off.

[krish2487]

well thank you yourownfree..


will do it that way.....

any particular references i should get hold of??
books, papers, etc...

[Itsmee]

Ditto ChrisA '5000W DC to AC inverter? Think about class "D" audio amps.'

Is it an amplifier or is it a PSU

[Itsmee]

Take a look at this link.

Home > Forums > Amplifiers > Power Supplies 5000w Smps

You could also take a look at AM RF transmitters, lots of power, simple circuits