How to apply PWM signal to H-Bridge made of MOSFETS

[Mrunal Ahirrao]

Hi,
I am working on multilevel inverters using cascaded H-bridge topology. But I am confused on how to apply a PWM signal to H bridge for this application. As it is multilevel inverter so the signal voltage should increase step by step so PWM should be used. But I am confused that do I need to apply PWM to all MOSFETS or only one PWM needed as used in L293D(motor speed control application) but for L293 got Enable signal but how to do that in H-bridge made of mosfet?

 

[FvM]

In a multilevel inverter, each switch is controlled by different waveforms according to the implemented multilevel scheme. It's unlikely that the same PWM is applied to different switches.

As a first step, try to understand how the chosen multilevel scheme is expected to work.

 

[Mrunal Ahirrao]

OK so I need to apply different PWM signals to all mosfets?

I am using this circuit.I found it on internet which is used for motor controlling

 

[FvM]

I am using this circuit

But how is it related to multilevel? It's a regular H-bridge, in this case wired for bipolar (2-level) PWM.

 

[KlausST]

Hi,

The circuit will not function like expected.

The low side FETs are O.K.
But the high side N FET s need a higher gate voltage than the bridge supply.
In your case this means a lot of voltage drop in high side fets. Motor will be slow. A lot of power dissipation in the high side fets.

Not what you want.

Klaus

 

[Mrunal Ahirrao]

I am using P channel mosfet in high side. And I am using cascaded H bridge multilevel inverter topology. So I am using H bridge.

 

[KlausST]

Hi,

but your shown schematic shows N channel FETs.

Is your problem solved?
Or do you still need assistance?

Klaus

 

[Mrunal Ahirrao]

Actually this schematic was for motor control and I am using it for multilevel inverter by replacing Highside N channel MOSFET by P channel MOSFET. And yes my problem is solved.This is the modified schematic:View attachment Switch board - Project.pdf