Hi Saugata,
I think that for controlling the amplitude a hardware approach is better
as so many delays and errors can creep in. There is a Buck Boost circuit with
two mosfets and an inductor and few diodes. The DC input to H bridge can be
controlled with B/B circuit with reqd. time delays generated by Micro output(which doesn't have to be so fast as changing per cycle of sinewave)
The shape and frequency then can be generated by normal 2 PWM outputs(Actually one is enough just route the output to another branch with a gate and this also have dead time built in).
I still wonder why anybody is not responding about my querry of transformers. The output of Inverter is serries of pulses at high frequencies with polarity reversal at 50-60 Hz. So is the transformer used designed for
50 Hz operation or high frequency like say 20KHz? There is huge difference
in size of transformers.
regards,
purushottam dayama



Quote Originally Posted by sougata
Hi Suded,

If I have understood right then you are suggesting that I build a hf oscillator around the SG3524 then use the PIC18F452 to supply the closed loop control voltage to the SG3524 (the PIC HWPWM acts as a DAC).

Now the issues are,

1. I already have two HWPWMs built into the PIC

2. The SG3524 allows dead-time programming through a simple resistor but while switching phases I again need a few logic chips to get it done.

3. I have designed the software around interrupts. I am doing an AD-Oversampling which bruce, tim and melanie suggested in the MELAB forum.For a pulse by pulse current limiting (so that the MOSFETs don't blow up) I am using a comparator to sense the current and generating an INT to turn off the MOSFET drives.(Heh! Heh! a digital copy of the SG3524 current limit scheme).
So why use the SG3524 as the ad-sample and dac conversion will add up to the loop error.

The only thing that concerns me is the THD introduced while driving inductive loads as my routines are not so fast to correct that in realtime. I tried but the results are erratic (thats because of lack of knowledge from my side). The PIC is running at 40MHz (10MIPS,10MHz@HSPLL). Now I am concentrating on reducing noise on the AD line, using interrupt based AD (PBP tends to waste time while doing AD).

BTW can anybody shed some light on the time consumed by LCDroutines. Because while processing interrupts with PBP I found glitches while the LCD was being updated.

Thanks to psdayama and doctor for the links. As far as PSPICE goes I am not sure whether my knowledge is sufficient to handle them (I don't have an engineering background)

Regards
Sougata