PWM, H-Bridge and NCO - PIC16F18446

[Ioannis]

Hope this draw clarifies a bit the problem.

Ioannis

[richard]

so where does the 1khz fit in ?


i expected more like this

[Ioannis]

You are right, I just didn't want to clutter the draw.

Ioannis

[amgen]

looking at your diagrams, seems like you could ..... set up the PWM module for 1KHZ as normal, for the 20HZ part, set up a timer interrupt for the low freq maybe with a couple of roll overs for lower freq.... then on tmr int, only need to switch the Q's and add a little dead time on each switchover.

[Ioannis]

Alain:
The PWM is controlled by a Pot. I could also make a variable power supply and control directly the voltage on a SMPS circuit instead of PWM. More complicated.

Amgen:
It is easier on the unipolar mode. But gets difficult on bipolar drive having software to control both PWM, low freq signal and the control of the 4 MosFets transitors. Including deadtime.
Better, most if not all of this be done on hardware using NCO, CWG, CLC etc.

I believe that it is possible to do this as Richard is confident too. I just need more reading to understand how all these modules will work together.

Ioannis

[amgen]

did you get someone for your h-bridge circuit ?? have a couple thoughts if not

[Ioannis]

The above seemed too complicated.

I think I better use this design route:

1. Use an PWM, NCO, CWG, CLC capable MCU like the ...K42 one. These chips may drive the PWM signal to the desired pin, so I can control the H-Bridge operation at will, according to the needs of the load.

2. On the H-bridge use Gate the IRS2890 driver that has also current limiting capability.

3. Use the MCU to control the upper Mosfets of the bridge as PWM to regulate the voltage required to the load

4. Use the MCU to control the lower Mosfets of the bridge to control the On/Off of the 0-50 Hz signal

On the above scheme, CLC may not be needed.

On Monday I will order the required parts to assemble a prototype. Though it will be mostly on air I hope it will work good enough to verify the idea.

Unfortunately the IRS2890 is available only in SMD but anyways...

Have found MosFets that should cover the SOA that is needed.

Any ideas welcome,
Ioannis