multilevel PWM signals

[mess123]

Hi,
What is the true meaning of multilevel PWM?? How do I generate multilevel PWM?? Can we get a constant duty cycle (not sinosoidal) multilevel PWM??
Is there any reference paper for this?

Thanks in advance.

 

[RCinFLA]

It is exactly what the name implies. There is PWM operating between two voltage levels and the voltage levels leep frog in several bands.

You have power supplies of different voltages.

The benefit is it requires less filtering.

Multi-level sigma delta analog digital to analog converters operate the same way.

A Comparative Modelling Study of PWM Control Techniques for Multilevel Cascaded Inverter from Leonardo Journal of Sciences

 

[mess123]

Thank you RCinFLA for this quick reply.
I haven't understood how does duty cycle (%) relate with this multilevel PWM??
In two level PWM, it is understood well, that it is Ontime/total time??? So in multilevel too, it is the average_on/full period??
I hope to get kind reply again... thanks in advance

 

[RCinFLA]

Same as two level, just breaking the two level PWM into individual stacked sub-segments of the larger voltage range.

Only trick is the sublevels need to range from 0 to 100% duty cycle to have proper crossover linearity, unless overlapping power supplies are used.

 

[mess123]

Thank you once again... Is there any reference for verilog code to do this project (i.e. generation of say 3 level 3 phase PWM using FPGA)... I want to generate the PWM signals through Altera DE2 board.