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AC/DC converter + Totem-Pole

Thread starter #21
Hmm, is possible to only use voltage sources with PWM to control the switches instead?
That would be easier I think, cause now its too complicated for me..I am not an experience user of LTspice.
 
Thread starter #23
I do not have the time to start over from scratch I think, cause I really need to make sure that this totem-pole converter is working somehow...
This totem-pole is already selected, so I need to simulate it.

I found this on another thread, but its looks so complicated I think, at least for me..
 

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ronsimpson

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#25
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Thread starter #26
Hmm I see. Maybe someone else on this forum I have some experience with Totem?
Yes, I was using with interleaved for a while, but thats was the wrong way to go.
 

ronsimpson

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Most Helpful Member
#27
You must choose a different IC. This one needs to see the power line voltage. I think all do that. (full wave rectified power line) Maybe there is a cleaver way.
 

ChrisP58

Well-Known Member
#28
You need to make sure that the control IC matches the power architecture that you want to use.

You can't just go swapping them back and forth without going through all of the steps necessary to make the conversion. While that can certainly be done, it takes a deep understanding of the fundamental operating principals of the circuits involved to be successful.
 
Thread starter #29
I talked with an teacher, he said if I can't find a PFC IC for totem-pole, it would may be good enough to connect two voltage sources that are controlling the switches.

--Edit--
I found a another controller PFC LT1509, it seems to control two switches, would that might work you think?
 
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ronsimpson

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#31
Look at the data sheet! They make data sheets for a reason. Look at the example circuits! Look at the SPICE examples for this part!
In red you will see how to make PFC using this part. It is a one MOSFET circuit where you started.
upload_2018-4-16_7-56-55.png
it is working quite alright.
It is not working! You can not drive the top MOSFET like that. (we talked about that)
There are two PWMs in the IC and you are using both.
You do have have experience. You need to find a simple PFC circuit and make only small changes.
 
Thread starter #32
It is not working! You can not drive the top MOSFET like that. (we talked about that)
I remember the VCVS, I guess I need to implement it for two of them since I have two PWMs.

There are two PWMs in the IC and you are using both.
What I understand, I am suppose to use both PWMs. one for one MOSFET, and one for the other one.
Yes, I am trying to find a simple PFC.
 

ChrisP58

Well-Known Member
#33
I remember the VCVS, I guess I need to implement it for two of them since I have two PWMs.


What I understand, I am suppose to use both PWMs. one for one MOSFET, and one for the other one.
Yes, I am trying to find a simple PFC.
Only one of the PWM circuits in the LT1509 are for PFC control. The other is for an integrated, yet separate, DC to DC converter.

You cannot use the two PWM outputs together to drive the upper and lower mosfets in a totem-pole configuration.
 
Thread starter #34
Only one of the PWM circuits in the LT1509 are for PFC control. The other is for an integrated, yet separate, DC to DC converter.

You cannot use the two PWM outputs together to drive the upper and lower mosfets in a totem-pole configuration.
Oh, I missed that information. Thank you. Hmm, so would you suggest an another IC PFC ? I have tried to looking for one that can suit a totem-pole configuration.

--edit--
Or is it possible to only use one PWM for two switches?
 
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Thread starter #35
Do anyone have some suggestion how I can simulate an totem-pole PFC configuration?
I just want to make it so simply as possible. I assuming that I need to have two PWM output from the IC in order to control two switches.

I need to finish the simulation soon as well..so its very stressful these days:(
 
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ChrisP58

Well-Known Member
#36
Do anyone have some suggestion how I can simulate an totem-pole PFC configuration?
I just want to make it so simply as possible. I assuming that I need to PWM output from the IC in order to control two switches.

I need to finish the simulation soon as well..so its very stressful these days:(
I don't know of any chips that do totem-pole PFC. Particularly, none that have LTspice simulation models. It's quite probable that someone out there makes one, just not Linear/Analog (that I know of.)

Your next option to do simple is to do just that. Find a PFC controller from LT and use it strictly as it was intended to be used. With a 4 diode bridge rectifier at the front. With a single inductor and mosfet for the boost. Find one that let's you easily change it's switching frequency, or live with what it runs at.

Although it may look simple, PFC is a fairly complex process. To get it done right, you need to let the chips work the way they were designed, in the topology they were designed to run.

I think that you've spent too much of your time trying to force parts to do things they weren't designed to do, with poor results.
 
Thread starter #37
Yeah, I think you are right. I have tried to contact Linear.com but they don't reply.

Yes, I feel it is quite complex to get it right. I have tried to, I have just adjust some parameters, but I realize that I can't use my calculated components value for the simulation, its not the same thing. As you said, I have to adjust the components for the simulation.

I heard from a supervisor that he suggested to implement an adjustable duty cycle that is varying with time for the two PWM that are controlling the switches for the totem. Do you know a good way to adjust the duty cycle with time some how? and do you how a way to build up your own IC-circuit?
 

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ChrisP58

Well-Known Member
#38
Building you own IC would be making a circuit with all of the functionality that needs to be in the chip. Look at the block diagram for one of the PFC ICs. And that's just a simplification. Coming up with the actual, discrete circuitry to do everything needed would be quite a task.

What is it about the totem-pole configuration that makes it important for your application?
 
Thread starter #39
I just to simplify the totem-pole as much as possible. It doesn't need to be complexed.
I need it cause it have a compact design for my charger. My charger is suppose to be so small and lightweight as possible.
 

alec_t

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Most Helpful Member
#40

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