OFF TOPIC: Hardware question --> DC / AC converter

[Student]

Hi!

Becuse im using CCS C compiler i thout it would be good idea to ask such question on this forum, and becuse there is no hardware forum part of the CCS i have to post it here...

Hardware:
Im testing one battery so the DC output comes from battery and not from car acu or marine battery. There is a charge pump after dc output.

Idea:
I want to make DC to AC converter with some PICMICRO MCU.
Input DC is in range from min. 12 - max. 95V and output should be 220V ~ at 50 hz.

Questions:
1.) Is this possible and which chip should i use for such project

2.) Costs and time used for development

3.) Is there maybe some schematics ( with picmicro ) for such devices.

Sorry for this off topic question, but i know that someone in this forum has done such things so all comments are most welcome !

Best regards !

[Student]

I forgot to write... there is no costs for programming. So, just HW parts.

[Douglas Kennedy]

Many on this board are A students unfortunately I'm not one of them.
If this is homework tell your instructor to give any of your responders an A.
It's not that this board doesn't help students it is just that unless the questioner makes a substantial effort to find the solution this board is slow to respond.

[Guest]

[SherpaDoug]

I can think of two ways of doing this, and neither of them would use any microprocessor at all. This is not a software project or even a digital project. It is all power and thermal management. What power level are you thinkg of? Tell us more about the application.
_________________
The search for better is endless. Instead simply find very good and get the job done.

[Student]

[JED]

Hi Student,
I’m currently working on a similar project myself. For a possible microprocessor solution you can use a PIC with pulse width modulation hardware like an 18F4431. You can then create a sin lookup table that is cycled thru periodically varying the duty cycle. This output can switch a DC bus voltage using IGBT’s to generate the analog signal. If you have an o-scope you can do this with just an output pin and a RC filter to observe that the theory works with 5V. Microchip has some great application notes if you look under AC induction motor control, variable frequency drive, or inverter. I think obtaining 230V will be a challenge requiring some sort DC to DC conversion possible a “boost power supply.” I’m certainly no expert so take anything I say with a grain of salt.
Regards,

[skrubol]

There are a few ways you could do this. By far the simplest, and possibly the least expensive is going to involve using an off the shelf power inverter. Inverters for 120v 60Hz are pretty cheap online and even in department stores. A quick look at ebay shows the same is true of 220 inverters. Inverters take about 12v input, but have some range to allow for running off battery or alternator. The one I looked at has a range of 10-15v. So basically now all you have to do is get your 12-95vdc down to 10-15vdc. The bottom range of your supply is comfortably higher than the bottom range for the inverter, so you can use a buck converter. This DC-DC power supply topology can reduce voltage (and increase current) with high efficiency. There are basically 4 parts in the power side of such a device: a switch (transistor, generally a FET,) an inductor, a capacitor (most likely you'll want a second capacitor on the input) and a diode. For control, if you're usig a PIC, you could theoretically get away with only that and 2 resistors to form a voltage divider to get the 12v output down to something the PIC's AD converter can read. You'd also need something to supply the PIC with a voltage it could operate at. A 5v linear regulator would work fine for this, and they only cost a buck or so and are just one 3 terminal part. Any PIC with PWM and AD should work. To keep things simple having an internal oscillator would be a bonus.
I'm not going to try and explain the layout or theory of a buck converter. This post is already too long. You can google the term or look it up on wikipedia to get a basic working knowledge of it.

[Student]

Thank you guys for your replay and for explanation.

Before i start with chip programming... does someone knows some good electronic forum for such things ?

Thank you in advance !

[ckielstra]

[newguy]

You can also check the Circuit Cellar design forums at http://bbs.circuitcellar.com/phpBB2/