Sine wave power inverter

[psdayama]

Has anyone looked into using a DDS IC like the AD9833 for an inverter application? What were the results? How did you achieve PWM from the analog output?

Bryan A. Thompson
[email protected]

I haven't seen the AD9833 datasheet. In analog it is very simple to make
PWM. What U need is to make a reference sinewave oscillator. This U can find
from Opamps Application note of National Semiconductors. Oscillator uses
weign bridge and JFET to stabilise amplitude. Then U need a trinagular wave
of " carrier " frequency i.e. at which frequency U want PWM. U feed the
triangualar wave and sinewave to good comparator and Uget the PWM in output. If U want -ve side PWM also then U use one inverter for sinewave
and feed that to another comparator. And U get the -ve half signal for pwm.
There is interesting article about this on
url:http://www.drbrushless.com/

[batee]

Yes, I understand the ironless / transformerless concept. I also plan to use no transformers (step-up or step-down) or inductors in my design.

An advantage of DDS is that it is programmed via SPI, so a jumper change or RS232 command could make changes to waveform shape and frequency.

Pulse transformers and driver ICs appear to cost about the same here in Midwest US. I chose the driver ICs because they could be driven with logic level inputs regardless of the FET design.

It looks like more research money is going into 250V and 600V FETs and IGBTs than into any other voltage ratings, so that's where I have chosen to focus my designs.

Do you anticipate problems with running a system like this continuously (for months or years at a time)? Even if the FETs were well heatsinked and stay cool, I would anticipate continuous operation would degrade their lifetime.

Good luck guys.

Bryan

[psdayama]

Hi Everybody!
it seems that nobody is interested in this topic now.
I have found one interesting paper and hope everyone will have a look:

http://eprints.iisc.ernet.in/archive...ass_Of_PWM.pdf

In the 4th example circuit is what exactly I have been searching.
Also don't know where is D.K.nagare now. He said he has already made
prototypes and was doing field trials. Now he is vanished from Forum and
also from Yahoo.
Hope to hear from U soon.