Customized PWM/ Waveform

General
1

Hello,

How can I generate waveforms like these? I am working on a Multilevel Buck Converter (aka FCML Buck/ Switched Capacitor Buck). The period is 10us. Each switch is ON for 2us. I have attached a picture of the circuit. Please share some valuable insight!

Screenshot 2025-12-08 003423
Screenshot 2025-12-08 0034232108Ă—710 40.5 KB

Screenshot 2025-12-07 234202
Screenshot 2025-12-07 234202781Ă—854 5.64 KB

2

Use two pulse generators with proper phase shift and OR them together:

doublePulseGen.plecs (6.0 KB)

1 Like
3

Hello,

Thank you so much. This is exactly what I was looking for. In your doublePulseGen.plecs file, could you please explain how you generated four pulses using only two pulse generators?

4

Hi Arnob,

Oliver has vectorized the pulse generator by setting the “Phase delay” parameter to be a vector. See below:

image
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By setting the phase delay as a 4 element array, the pulse generator will generate 4 pulses each with the associated phase delay determined by the index.

Hope this helps!

1 Like
5

Hello Munadir,

Thank you so much for the explanation. I am a new PLECS user. One thing I am confused about is that I need to drive 4 MOSFETs. But here, all 4 gate driving pulses are coming from one source. My question is, how can I drive 4 MOSFETs with the same PWM sequences?

6

Hi Arnob, as a new user I would recommend a few things to help you get up and running.

  • PLECS tutorials: while these are a little dated they are still a fantastic resource for new users to get up and running. Tutorials | Plexim has a whole list of tutorials for all of our products but since you are a new user I would stick with base PLECS for now. I would at the minimum go through “PLECS: Introduction to PLECS Standalone”, “PLECS: Modeling a Switched-Mode Power Supply”, and “PLECS: Thermal Simulation of a Buck-Converter”
  • Video tutorials: on our Youtube page you will find a host of useful videos to help you get up and running with PLECS. As a new user I would recommend starting with the playlist “PLECS tutorial videos”.

Now to get back to your question of how to drive individual MOSFETs. As I mentioned, the solution Olivers provided vectorizes the pulse generator using the phase delay. So the output of the Pulse generator is 4 signals lumped into one line. To get the individual signals out you can use a demultiplexer that converts the vectorized gate signal into individual gate pulses that you can then send to your MOSFETS. As an example, have a look at the “2-Level MOSFET Conv.” PLECS component. If you right click on the component, expand the Subsystem menu option and select Look Under Mask you will see an example.

Hope this helps!