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UC2856-Q1: Controller for Two switch forward converter controller

Karthik karri
Prodigy 235 points
Part Number: UC2856-Q1
Other Parts Discussed in Thread: UCC27212A-Q1, UCC2897A

Tool/software:

 Hello Ti Team,

I am looking for PWM controller to drive two switch forward converter like shown below picture.

Does UC2856-Q1 supports two switch forward converter ???

Because (HI,LI ) outputs of the controller should be high at the same time because outputs (HI,LI)should be non-complementary as both switches of the two-switch forward converter should be turned -on at the same time.

or 

Can you suggest the recommended AEC-Q qualified PWM controller which drives the two switch forward converter.. 

Thanks ,

Karthik.

  • 0
    TI__Mastermind 32775 points

    Karthik,

    Since the high and low-side switches are turning on/off at the same time, any single output, general purpose, 8-pin, PWM controller can be used to drive a 2-switch forward converter. For example you might consider a controller from UCC28C5y-Q1 family which has many different UVLO/Duty options. In this case you simply connect the two gate driver inputs together to then accept a single PWM input signal. Otherwise you may be able to find a simpler single input, dual output gate driver. All we really require from the gate driver is the level shift (bootstrap) for developing the high-side drive and that the two gate driver outputs are synchronized in phase. Once you have this, you set up the controller, design the power stage and compensate as if it were a single switch forward converter.

    Reference Design Examples shown below and more can be searched here:

    1. PMP30183
    2. PMP10215

    Please download and use TI Power Stage Designer for help to design the power stage.

    Regards,

    Steve

  • 0 in reply to Steven Mappus1
    Prodigy 235 points

    Thanks Steven for the suggestion ,

    Option 1:

    As you said i will can go like below picture ,

    UCC28C5x-Q1 which  connect the two gate driver inputs together to then accept a single PWM input signal +UCC27212A driver which drives the two switches of the two switch forward converter at the same time.

    I think this will be ok ..what is your opinion on it Steven???

    Option 2:

    Otherwise please you can suggest any AEC-Qualified   single input, dual output gate driver.

  • 0 in reply to Karthik karri
    TI__Mastermind 32775 points

    For gate driver IC support, please submit a new E2E thread and it will be directed to the gate driver team.

  • 0 in reply to Steven Mappus1
    Prodigy 235 points

    Ok ,i will drop in new thread for gate driver|

    what about option 1 as shown below, is it fine Steven or you find any error in it???

     

    if it is ok means i will proceed for it

  • 0 in reply to Karthik karri
    TI__Genius 15416 points

    Karthik,

    Steve is in time bank today. As he mentioned, any general PWM controller works, so you can connect the output to both low side and high side driver inputs.

    Thank you

  • 0 in reply to Manuel Alva Hernandez
    Prodigy 235 points

    Thanks Manuel,

    Then i am proceeding like above mentioned picture  in my design  UCC28C5x-Q1(controller ) + UCC27212A-Q1(half bridge driver) which drives the two switch forward converter.

    thanks,

  • 0 in reply to Karthik karri
    Prodigy 235 points

    Hello Steven Mappus,

    Point1:

    i have doubt to select which topology in my application in the forward converter either Active clamp forward converter or two switch forward converter can you given your suggestion on it..

    I am getting input supply  after PFC block .

    Input voltage to my DC-DC forward converter is  Vin_min=210 V and Vin_Max= 260V. 

    Output voltage =28v + 10% ,output load current =8A

    We Need efficiency of around = 90 to 95 % in between to achieve from forward converter.

     can you give some comparison steven   what  are the advantages and disadvantages of  high side active clamp forward converter and in the same way  advantages and disadvantages of the two switch forward converter  and low side active active clamp forward converter .

    The three topology comparison 

    Point 2:

    i have seen steven your Ti forum post on forward converter i am attaching that also but in that no comparison for active clamp and two switch forward converter.

    \

    I observed  the in active clamp forward converter the voltage stress of the MOSFET is more a ( VMOSFET= Vin/(1-D )) but in two switch forward it less (VMOSFET=Vin).

    but i am not sure about other  advantages and disadvantages of active clamp and two switch forward converter comparison.

    our main objective is to achieve high efficiency around 90 to 95%  with less losses (like conduction and switching losses  ) 

    So in both active clamp forward converter and two switch forward converter which is best topology  to consider and achieve high efficiency  in my application ( input and output voltages ,load current are mentioned in the above conversation for you reference)

    Thanks in advance Steven!!

  • 0 in reply to Karthik karri
    TI__Mastermind 32775 points

    Not sure what is the answer for your specific case. You need to do the study yourself and then let me know? TI Power Stage Designer is a good tool for comparing power stage performance. Also, I wrote a Power Topology presentation many years ago that was presented to PSMA. There is some high level comparisons and guidance related to forward converters included. This material is not TI but I can share it because it is on public domain on the web.

    Steve

  • 0 in reply to Steven Mappus1
    Prodigy 235 points

    Ok thanks for the reply Steven ,i will do study and give you the answer which is right pick.

  • 0 in reply to Steven Mappus1
    Prodigy 235 points

    Hello  Steven,

    Had done study ,  Active clamp forward converter suits my application and gives better efficiency compared to two switch forward converter.

    But one more doubt  i have Steven, due to AEC-Q qualified controller for active clamp forward converter .  We have to use only Automotive qualified AEC-Q components in our designs or projects  due to some constraints.

    UCC2897A fits my requirement but it is not AEC-Q qualified and i have checked there is no AEC-Q  qualified  active clamp forward converter  controller in TI.

    So my doubt is now,

    is there any option to go with Ti normal  PWM Controller + Ti Half bridge driver which can drive the active clamp highside forward converter operation.

    As two MOSFETS operate complimentary in active clamp forward converter ,with  general Half bridge driver can we drive it or is there any limitation to Active clamp forward converter?

    is there any Ti normal  PWM Controller + Ti Half bridge driver,  what is your suggestion please check and let me know Steven.

  • 0 in reply to Karthik karri
    TI__Mastermind 32775 points

    Active clamp forward is mostly popular for telecom/industrial/consumer markets and this is where the controller development was focused. No automotive versions are available.

    Steve