3KW Full Bridge Converter

[bayya]

Hello
I am new to this forum. This is my first post.
I want to use UCC2895 controller for 3KW full bridge phase shift design (90V-150V input & 130V/20A output). It is a battery charger.
Will it be OK?
Any feedback from members regarding the possible problem areas?

 

[goldsmith]

Dear bayya
Hi and welcome to the EDA board .
What is your problem accurately? do you want know , is it possible , with your values ? if yes , yes ,it is possible , and it is simple. And the driver , that you selected , is very good choice .
Good Luck
Goldsmith

 

[Tahmid]

It is possible to use UCC2895 as the controller for your application. You need to decide on the driver circuit for the full-bridge. A lot of problems can pop up while designing. This will depend on your previous experience and your skill in designing SMPS circuits. Is this the first time you are making an SMPS circuit? If yes, then, you should start with a small power level, like 50-100W, learning, understanding, testing, debugging and perfecting every part before you move on to make it 3kW.

Hope this helps.
Tahmid.

 

[bayya]

It is possible to use UCC2895 as the controller for your application. You need to decide on the driver circuit for the full-bridge. A lot of problems can pop up while designing. This will depend on your previous experience and your skill in designing SMPS circuits. Is this the first time you are making an SMPS circuit? If yes, then, you should start with a small power level, like 50-100W, learning, understanding, testing, debugging and perfecting every part before you move on to make it 3kW.

Hope this helps.
Tahmid.

Thanks Goldsmith & Tahmid.

This is not the first SMPS design for me. I did a 800W full bridge, but that was from 230V AC input followed by active PFC (400V) followed by full bridge. Since the input voltage was quite high (400V constant), the switch current was low. And it was not phase shifted design.
This is my first phase shift design.
The present design has much lower input and higher power. I expect around 35A to 40A switch current. For low ON time losses, I need to connect 2 MOSFETs in parallel for each leg- low Rds type. That will give very high gate charge and may need to supply 3A to 4A peak drive current. Since I will be using gate drive transformers, I expect some trouble there.
Am I right in assuming the above factors? I feel that the drive transformer waveform will not be a sharp rectangular one at that high gate charge.
Is it a must to use a drive transformer?
I assume, by using UCC2895, I don't need a balancing capacitor in series with the primary of the power transformer. Am I right? I can't think of finding a capacitor with such high current rating.

I hope there is clarity in what I expressed.

bayya

 

[Tahmid]

What is the reason you chose to use a drive transformer? Why not high-low side driver ICs? Then, you don't face the problem of distorting the wave form if you use a "powerful" driver. Since you're using full-bridge, you don't need the balancing capacitor.

Hope this helps.
Tahmid.

 

[goldsmith]

Dear bayya
Hi
I'm agree with Tahmid . a simple float driver , will be ok for your purpose. the transformer driver , will have some problem , and you should add some components , to improve , that. but a float driver , is ok and it's behavior is linear ( transformer , as a driver , can become , nonlinear ).
Best Wishes
Goldsmith

 

[bayya]

Dear bayya
Hi
I'm agree with Tahmid . a simple float driver , will be ok for your purpose. the transformer driver , will have some problem , and you should add some components , to improve , that. but a float driver , is ok and it's behavior is linear ( transformer , as a driver , can become , nonlinear ).
Best Wishes
Goldsmith

Yes, Tahmid is right. The reasons why I thought of transformer drive is- I thought of placing the PWM controller on the output side and apply the output voltage sense directly to the PWM IC.
Because, the charger output has to be changed at 3mV/degC per cell for VRLA batteries and I wanted get that by using the IC's error amplifier and changing the reference voltage. Making a transformer looked simple.

Since you're using full-bridge, you don't need the balancing capacitor.

Balancing cap is still needed if I use voltage mode control. No?

bayya

 

[Tahmid]

A high-low side driver would give you a lot of accuracy, probably more accurate than a gate drive transformer.
I'm not exactly sure but I think you can make do without a balancing cap even in voltage mode control, in full-bridge converters. Need to take a look here.

 

[goldsmith]

Again Hello my friend.
According to the pressman's book , you should use that capacitor . ( it will do some act at your circuit , that some of one is safety from over Duty cycle , current)
Best Wishes
Goldsmith

 

[Tahmid]

It's better but I think you can avoid it due to the high current requirement and these also tend to be expensive.
https://www.edaboard.com/threads/224262/#post959290

I've seen some full-bridge designs without it that work successfully. I guess it's all up to you in the end.

---------- Post added at 16:39 ---------- Previous post was at 16:38 ----------

https://www.edaboard.com/threads/226314/#post965191

 

[goldsmith]

Dear Tahmid
Hi
How are you today?
That capacitor can increase the efficiency , and it can improve some specifications of the circuit , but i have seen some smps without that capacitor too.
Best Wishes
Goldsmith

 

[Tahmid]

I'm fine. How are you? Yes, the capacitor improves the circuit. But like we both said, we've seen circuits without it. You'll probably be able to build a good circuit without it.

 

[bayya]

Hello Tahmid and goldsmith
Thanks for the continuous inputs.

A high-low side driver would give you a lot of accuracy, probably more accurate than a gate drive transformer.

I think I should place PWM IC on the input side and use gate driver ICs.

Yes, the capacitor improves the circuit. But like we both said, we've seen circuits without it. You'll probably be able to build a good circuit without it.

Since the IC has current mode control, I will go without the series cap.

bayya

 

[Tahmid]

Yes, the PWM IC provides the input to the gate driver ICs.
You can avoid the series cap, like I mentioned before.

 

[Nilesh Sailor]

Hello Sir..
I M in final year electrical..and i m making a project on full bridge converter using microcontroller..
can u sujest me idea about this..

 

[bayya]

Hello Sir..
I M in final year electrical..and i m making a project on full bridge converter using microcontroller..
can u sujest me idea about this..

Hello Nilesh,
What is the basic idea?
What output voltage and power are you planning?
Where do you want to use microcontroller?
Do you want to build full bridge converter or a microcontroller based project?

-bayya

 

[Tahmid]

Hello Sir..
I M in final year electrical..and i m making a project on full bridge converter using microcontroller..
can u sujest me idea about this..

Is the microcontroller going to be doing the PWM? Or is it going to control the PWM chip? --- This you have to decide. If you don't have any idea about this, you need to research about PWM, common PWM chips (like TL494, SG3524, SG3525, etc), their functions and uses. You then need to research on advantages/disadvantages of using the microcontroller instead of the PWM chip. Then, you need to take the decision.

You also need to provide us the specifications like output voltage and current, how far you have studied/worked on this and what kind of help you require.

 

[s.manikandan]

Is the microcontroller going to be doing the PWM? Or is it going to control the PWM chip? --- This you have to decide. If you don't have any idea about this, you need to research about PWM, common PWM chips (like TL494, SG3524, SG3525, etc), their functions and uses. You then need to research on advantages/disadvantages of using the microcontroller instead of the PWM chip. Then, you need to take the decision.

You also need to provide us the specifications like output voltage and current, how far you have studied/worked on this and what kind of help you require.

hi i m going to design a 3Kw VRLA battery charger for my application.I have chosen dc/dc full bridge converter with pfc boost follower .i designed boost circuit. now i m in the portion of designing fulll bridge converter. the battery charger controlled as you said as microcontroller controls pwm chip and pwm chip for controlling full bridge switching..
i dont know the concept to proceed with that, how to achieve three stage battery charger using microcontroller and pwm chip.

what does microcontroller do..? what are the processes it takes..? how to acheive constant current and constant voltage mode according to battery voltage level...?

just give some inputs as much as you know...