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full bridge pwm controller

kubeek

Well-Known Member
Thread starter #1
Hi,
i am looking for recommendations for a good pwm controller that could be used for push-pull or bridge converter. So far I found voltage-mode SG3525, and current mode UC3846 (1846 or 2846 are the same thing).
I would like to use current mode, but cannot find any working model of the 3846 for ltpsice. (found some very old pspice model of SG1846, but it would be PITA to convert it)

Do you have any suggestions for a controller that is not obsolete and has a model that would work in LTspice?
p.s. I am trying to stay out of phase-shift for now, as it is my first high power converter and would like to keep it within what I know and undestand.
 

gophert

Active Member
#2
Hi,
i am looking for recommendations for a good pwm controller that could be used for push-pull or bridge converter. So far I found voltage-mode SG3525, and current mode UC3846 (1846 or 2846 are the same thing).
I would like to use current mode, but cannot find any working model of the 3846 for ltpsice. (found some very old pspice model of SG1846, but it would be PITA to convert it)

Do you have any suggestions for a controller that is not obsolete and has a model that would work in LTspice?
p.s. I am trying to stay out of phase-shift for now, as it is my first high power converter and would like to keep it within what I know and undestand.
I think the PIC microcontroler and their full bridge enhanced PWM is the way to go. No much for simulation but it is all pretty straightforward - I've never needed to simulate.

It is much better to keep the P-channel (high side) on and only modulate only the N-channel (low side of the H). P channel devices generally have higher on resistance and higher switching losses so you are better off just keeping it open until you need to change directions.
 

ronsimpson

Well-Known Member
Most Helpful Member
#3
Do you have any suggestions for a controller that is not obsolete and has a model that would work in LTspice?
Your problem is Linear.com does not really have the part you want. AND There are some nice parts but there is no Linear Spice models for them. I think google has a form with many LT Spice models.

I have made LT Spice ICs (models) but it is not easy and you will have errors. In that the data sheet does not really tell you how things work inside.
 

kubeek

Well-Known Member
Thread starter #4
It is much better to keep the P-channel (high side) on and only modulate only the N-channel (low side of the H). P channel devices generally have higher on resistance and higher switching losses so you are better off just keeping it open until you need to change directions.
Thanks for the tip, however I doubt I could really use that technique with an off-line 3.5kW SMPS ;)
Yeah, that´s the problem with finding something suitable, when an H bridge motor driver swamps all your results for full bridge SMPS, and when one type of chip can be used interchangeably for three different topologies...
I finaly found a candidate from LT, but through google and not their website since the pwm controllers are really hart to sort through there. The hot candidate for now is LTC3721-1, so probably tomorrow I will adapt my simulation from a simple discrete PWM made of behavioral sources to this chip and see how things go.
 

Ian Rogers

User Extraordinaire
Forum Supporter
Most Helpful Member
#5
I needed a Hbridge.. Built one to use a24v 6A motor.... Worked okay, bit sluggish response but hey!! first go I was happy.... Until.. I bought a pololu H bridge with 4 cracking N type MOSFETS... Wow.. I cannot match that.. PWM input and direction... The module even supplies a regulated 5V for your circuit.. I first used Alec's PWM circuit from the article section but ended up with a pic12f1840 driving it!!

https://www.pololu.com/product/757 this is the one I got..
 

kubeek

Well-Known Member
Thread starter #6
God dammit, that stupid LT chip can only do up to 300ns of dead time, which is totally not enough. Any more suggestions?
 

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