Sine wave power inverter

[psdayama]

Hello!
I already informed U in pvt mail that U have to use either Pulse txrs or
opto isolators for driving. Bridge driver ICs don't work more than 100volts.
All U have to do is put the txrs/optos in output of Ur circuit or use simple
bridgedriving ICs and txrs. In case of Opto's U have to steal driving current
with high resistors and zeners and use 1more transistor/gate to make fail-safe. Means when signal the FET remains off. I think that in this respect
the pulse transformers are ideal solution and cost no more than Rs.12-15 each. U can also borrow some technic and keep the gate reverse biased
during off period.
Many circuits are available on Fairchild's website as they have most the
driving ICs and POWER mosfets.

[sougata]

Hi Dayama,

I am sorry I couldn't be in touch as I am under terrible pressure handling some railway projects. I am a one-man army as you know.

Back to the topic:

1. Any improvement or innovative idea is welcome.

2. My sinewave inverter is running successfully (24VDC-240AC~50Hz) but cannot share the schematic and code as I am commercially bound.

3. Should there be any PIC related problem I will surely try to help within my knowledge boundaries.

4. I have already done a PIC16F676 based squarewave UPS design (inspired by a forum member) and currently testing it.

5. I am working with PIC16F73 to port my design of sinewave inverter into a small offline UPS.

6. Double conversion is okay but generally more complicated and may be expensive in terms of ROI. What I have found is that boosting the voltage from 24VDC to 384VDC (to create a 240V AC) is less efficient. May be due to my limited knowledge on designing sm transformer. A 48V DC based boost converter gives better result.

7. I would be working on a different technology from June onwards that promises to deliver sinewave output using a single stage and ferrite transformer. I don't know whether I would be successful there as it is my own project and have limited funding. If I can spent time and get some fruitful results I will post them here.

8. Regarding MOSFET drive what I have realised is that a soft turn-on reduces harmonics and a fast turn-off is necessary to cope for switching losses. Also ringing should be well controlled otherwise bursts for no apparent reason. And never use the Microchip drivers. They are real crap. I followed every guideline and got terrible results. IR, Toshiba great. In fact I asked in the Master's conference that why Microchip is using IR gate drivers on their dSPIC motor control board when they have there own product line.

[psdayama]

Dear Saugata,
thanks for writing. It has been long time to see U or some posts.
We all understand that U are helping the forum but U have Ur own army
to care and feed :-)

Now about Ur points:
1.& 2. We would never ask U to divulge Ur commercial secrets for FREE!
3. I have yet to commence the exploration of PIC. As I told U I am
doing all prokects in other world but ultimately it is a 8bit and uC thing.
So just nomeclature changes but basic things are same. I find that ATMEL
has also put up ARM type which are just as good as PIC and I don't have to change the assembly language. But sure will ask about PIC in few days after
finishing old projects.
4. I am also thinking about same PIC16F73 but I think other 676 has more PWM outputs which can of great help.
6.Ferrite transformer design is no big deal if U have designed iron core one.
There are many websites which have actual examples.Also if U can convert
48V to 300+ volts then 12-24 V to same is also not differrent. Just have some
more conductors and that helps for high frequency. For example I had make
primaries of 11SWG but instead I used 2 conductors in parallel of 14SWG.Nice thing about ferrites is that U need only few turns as turns/volt are as much as
40times less.
7. am hoping to know what 'new technology" U are talking about. Surely it will be very interesting for the thread of "sine wave inverter"
8. U have correctly stated the position of fast and slow turn on. Everybody
has to make decision about switching losses and surge supression and cost off higher voltage device. As far as Bridge drivers i hate those and I rely solely
on pulse transformers or opto couplers.
regards,
psdayama