Simplified AC PWM Controller

Thread Starter

nekojita

Joined Nov 19, 2010
130
Hi,

In an earlier post for an AC PWM controller, there was a lot of great commentary and feedback. As I showed in one of my last posts, I did create a working prototype.

In moving this into KiCAD to begin a layout, I realize that there are simply too many components for the space that I have to work with.

Looking back at some of the articles that I found while researching the AC PWM controller, I found one that has a similar circuit to the final circuit that the thread mentioned above but with many fewer components.

The circuit and output are shown below:
1610393168229.png
1610393220175.png
Simulating this circuit in LTSPICE does not give the same results. Attached is my LTSPICE version and the complete article.

If anyone in the Forum has any thoughts or comments, they would be greatly appreciated.

Thanks,

Neko
 

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Thread Starter

nekojita

Joined Nov 19, 2010
130
Hi Danko,

Thanks for pointing out those changes. My wife says that there is a Cantonese saying that goes, "Some people have eyes but they can't see." :)
A couple of comments and questions on your mods to the original circuit:

• The transformer inductances are an order of magnitude higher than what I had. Do they really need to that high?
• I just grabbed the LTC4442 gate driver from the LTSPICE Power Library because it was available. May use some other gate driver. Thoughts?
• A VDD of 20V is high. Could this be reduced by increasing transformer secondary inductance? (or reducing primary inductance)
• Did you test the circuit over a range of PWM duty cycles? The reference paper suggests that 10-90% DC can be achieved with transformer coupling.

Please let me know your thoughts on these points.

Thanks,

Neko
 

Danko

Joined Nov 22, 2017
1,019
Hi Danko,

Thanks for pointing out those changes. My wife says that there is a Cantonese saying that goes, "Some people have eyes but they can't see." :)
A couple of comments and questions on your mods to the original circuit:

• The transformer inductances are an order of magnitude higher than what I had. Do they really need to that high?
• I just grabbed the LTC4442 gate driver from the LTSPICE Power Library because it was available. May use some other gate driver. Thoughts?
• A VDD of 20V is high. Could this be reduced by increasing transformer secondary inductance? (or reducing primary inductance)
• Did you test the circuit over a range of PWM duty cycles? The reference paper suggests that 10-90% DC can be achieved with transformer coupling.

Please let me know your thoughts on these points.

Thanks,

Neko
Hi Neko,
I think, you have only one big problem: to design wideband (0.1 Hz - 10 MHz) transformer.
Or you can use miniature HF transformer, as @Bordodynov suggested in this post.
You are designer, so it should be your choice.
 

Thread Starter

nekojita

Joined Nov 19, 2010
130
Hi Danko,

Transformers are always a tough one. I haven't tried to dial in a wideband transformer for this application. As my colleague always reminds me, "There's no free lunch."

Due to the transformer design limitations, my thought is to go to the circuit in Figure 6 of the research paper. Using your simple DC-DC converter circuits previously posted but in a single positive voltage as shown in Figure 6, this comes in between the last Danko circuit (prototype tested) and the very simplified circuit last posted.

What do you think? What are the perils and pitfalls?

Thanks,

Neko
 

Thread Starter

nekojita

Joined Nov 19, 2010
130
Hi Danko,

This version starts adding parts back in, but still probably easier than dealing with the wideband transformer.

I think I hve it drawn correctly but there is only a very small output. Do you see what I am doing wrong?

Thanks,

Neko


1610662787844.png
 

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Danko

Joined Nov 22, 2017
1,019
This version starts adding parts back in, but still probably easier than dealing with the wideband transformer.
I think I hve it drawn correctly but there is only a very small output. Do you see what I am doing wrong?
Hi Neko,
You can start with this circuit:
1610709687521.png
1610709800761.png
ADDED:
Pay attention to short circuit current through chain of M1, M2, M3, M4.
In real circuit this current may be much bigger:
1610735360227.png
 

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