[SOLVED] Simulation of PWM Module SG3524 or SG3525 in Orcad 17.2

[shomikc]

Hello all,

Is it possible to obtain a library for cadence orcad pspice 17.2 that has the modules for either SG3524 or SG3525.

Thanks.

 

[andre_luis]

The SPICE library (.lib) for the SG3524/25 is easy to find on the Web, even though these components are very old. It was not often that I had to make my own component in an environment from an available model, and I recommend doing the same; you may lose less time to learn how to do this than to keep looking for it. There are tutorials on Youtube exaplaining the steps on how to build your own component on Orcad from a known model.

 

[CataM]

You do not need to look for anything since OrCAD 17.2 already has it. They undertook a major increase in their libraries with this new release.
2 ways to find it:
1) Place --> PSpice component --> search --> search for the component you need
2) SG35xx are in the "controller.olb" in the following route: C:\CADENCE\SPB_17.2\TOOLS\CAPTURE\LIBRARY\PSPICE\ADVANLS\

 

[shomikc]

Hello all,

I ran my Voltage mode controlled Buck using UA741 and the simulation worked at 25 kHz switching frequency (or 40 useconds time period).

I made the same simulation using sg3524 but it doesn't seem to converge. Does it have anything to do with the default SG3524 parameters.

 

[andre_luis]

I made the same simulation using sg3524 but it doesn't seem to converge. Does it have anything to do with the default SG3524 parameters

Solving convergence problems, although there are some tricks on the Web explaining how to relieve some parameters of the simulation, it is still an iterative process of trial and error. One of the reasons for convergence error is the use of ideal (non-real) components, and in this case in particular, I would try to add a high-value Pull-down resistor (eg, 1M) to the MOSFET base.

 

[shomikc]

Problem in Pspice simulation using SG3524

Hello everyone,

This is my first post in Power Electronics forum.

I am able to generate the pulse from the SG3524. The circuit I have made is shown below.



The output of the circuit is shown below.



Somehow I think the output is wrong. But I cannot figure out the mistake
Could anyone please help me sort this out.

Thanks. Shomik.

 

[andre_luis]

Somehow I think the output is wrong. But I cannot figure out the mistake

Finding that something is wrong purely based on your intuition does not seem like a reasonable analysis criterion. The above circuit lacks reactive components, sounds like a test circuit purposed to use with real-world devices to see if something is working. Why not to mount in the simulation one of the SMPS circuits suggested in datasheet?

 

[CataM]

Somehow I think the output is wrong.

Waveforms as expected. PIN 11 swings between 0 and 7.5V, as expected.

 

[shomikc]

Hello all,

I am looking for Optocoupler tlp250 or tlp350 in orcad 17.2 but cannot find. Is there an equivalent to this optocoupler. Also is it necessary to have totem pole between optocoupler and MOSFET Gate terminal where the totem pole is connected to the external gate resistance, 22 ohm, 2W.

 

[CataM]

Download them from TOSHIBA's website: https://toshiba.semicon-storage.com/ap-en/design-support/simulation/agree-pspice-download.html

Also is it necessary to have totem pole between optocoupler and MOSFET Gate terminal

The TLP350 is already a MOSFET gate driver with totem pole output stage. If you feel you want more current, choose another driver with higher current capability because adding more stages to the driver can increase the propagation delay.. but it can be considered as well.

 

[shomikc]

Hello everyone,

I am using SG3524 for PWM generation in a simulation of buck chopper. AT first I was using IRF640 from the PWRMOS library but that resulted in convergence issues so I switched to MBreakN3 and now though the convergence issues are gone I am getting a zero output voltage.

 

[CataM]

I am getting a zero output voltage.

Converter not switching, as expected. You can not drive a high side switch with the SG3524, unless you use the output of the SG3524 to drive a high side gate driver, e.g. LTC4440.

- - - Updated - - -

An easier and straightforward way is to use a PMOS instead of the NMOS, which do not needs any additional circuitry and hence you do not need to worry about the pre-charge of the boot cap.

 

[shomikc]

Dear Sir,

Can you please explain "pre-charge of the boot cap". Please can you tell me what is boot cap and where it occurs and also why it needs to be pre-charged and what is the method of pre-charging. If you could point me to some literature on this it would be most helpful.

 

[CataM]

explain "pre-charge of the boot cap"

and also why it needs to be pre-charged and what is the method of pre-charging

You will understand after you undestand how to drive a high side switch using the bootstrap technique. Here shows a nice explanation with example: https://www.edaboard.com/threads/371966/

If you could point me to some literature on this it would be most helpful.

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