Hi Swagatam, I finally completed the your circuit on a PCB. I checked the wave form and frequency and it seems to be working. The clock input is 1.08 KHz and the PWM frequency is 60 Hz at each diode junction.
I told you in a earlier conversation that I had previously built a DC/AC Inverter which ran off of a Square wave circuit using the 4069 CMOS Hex Inverter circuit I have attached above. In that diagram the person who designed it used two pairs of MOSFETS, each pair consisting of a PNP and a NPN Mosfet.
In mine, I just used two pairs of all NPN Mosfets and it runs perfectly at 130V 60Hz and powers about 500w .
Now the Problem that I'm having is that when I replace that Square wave circuit with the completed NEW PWM circuit it does not want to work properly.
I had originally used SUP90N08 Mosfets and IRF540 Mosfets and both sets worked perfectly with the Square wave circuit, the SUP90's being the more powerful.
I first tried the IRF540 Mosfets with your circuit and it BLEW each one of the IRF540's up ! Then I tried the SUP90's but I was a little wary of having these Mosfets Blow up on me so I turned on the Inverter just briefly but did not hear the useuall HUM , so I quickly turned it OFF trying not blow up any more Mosfets.
I retested your circuit after the IRF540's blew up and it is functioning properly,I checked the Wave Form and it was exactly the same as the screen shots I sent you and the Output Frequency at the Diode junctions is 60.04 Hz
So the Big question is, why is it not working properly when I put it in place of the square wave circuit????
What function do Diodes D17 & D18 perform at the transformer?
Sorry for all the questions,
Your friend Ali
Did you join the diode junctions to R3, R5 of your square wave inverter stage? If the mosfet output stage is working well with the oscillations from the gates of IC 4069, there's absolutely no reason why it won't handle the clocks from the diode junctions of our modified sine wave circuit.
I would recommend you to built the output stage exactly as shown in the diagram i.e. include R3, R5, TR1, TR2 and the mosfets TR3, TR4, TR5, TR6 and connect the diode junctions from ICs 4017 to R3 and R5.
Thanks and Regards.
Hi Swagatam, thank you for replying so quickly. I have attached a diagram of how I have my Output stage connected to the Diode Junctions of IC1 & IC2. I have eliminated resistors R4 & R6.
Is the way I have it connected OK or NOT
I think there's something wrong with the output stage, it should behave like a push-pull manner, so I think PN mosfets will be also required.
I think if there's so much of confusion we better follow the working model i.e. include R3, R5, TR1, TR2 and the mosfets TR3, TR4, TR5, TR6 and connect the diode junctions from ICs 4017 to R3 and R5.
I am pretty sure that if the square wave version is working with this output configuration then it will do absolutely the same with our circuit also.
Hi Swagatam, I performed a few voltage checks on our PWM circuit . I check the voltage with the Clock circuit and the PWM circuit disconnected from each other, at the clock circuit output, the voltage is + 6.45 V.
When both circuits are connected, the output voltage at the Diode Junctions of IC1 & IC2 is + 5.93V.
Thats a voltage drop of Half a Volt, is that OK. Or is that the problem.
When my Square wave circuit is running the inverter, the voltage at the Gate of the Mosfets on bank #1 is +6.08V and the voltage at the Gate of Mosfets on bank #2 is +6.45V. Not sure why there is a difference.
Maybe the + 5.93V at the Diode junctions is not enough to turn ON the Mosfets.
I have attached two Data sheets ,one for the SUP90N08 which is what is running in the inverter circuit right now , and the other is for the STP140NF55 which I have 4 of them on hand. Based on the Data sheets,which Mosfets do you think are better to use.
Sorry for bombarding you with all this info, but I feel if I can give as much information as I can , you being an Electronic Engineer,we should be able to solve this.