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WEBENCH® Tools/LM5022: lm5022

user5368470
Intellectual 530 points
Part Number: LM5022
Other Parts Discussed in Thread: CSD19537Q3, CSD19534Q5A

Tool/software: WEBENCH® Design Tools

please give me calculation of parameters  excel file， my design: VIN=16~40VDC, voutput=8V, IOUT=1.25A; isolated ; thanks

  • 0
    Genius 4910 points
    Hi user,

    Could you please elaborate on the above question with what exact parameters and the excel file you are referring to ?.

    Thanks and Regards,
    Atul
  • 0 in reply to Atul_Kulkarni
    Intellectual 530 points
    ex: how to chose Transformer and mos? and i will design Consideration flyback.
  • 0 in reply to user5368470
    Genius 4910 points

    Hi User,

    Please use the below Webench link to create the design for LM5022 for your conditions.

    https://webench.ti.com/webench5/power/webench5.cgi?origin=pf_panel&VinMin=16&VinMax=40&O1V=8&O1I=1.25&base_pn=LM5022&AppType=POWER&Flavor=None&Topology=Flyback&op_TA=30&lang_chosen=en_US&optfactor=3

    You can also create design for the other input output conditions using the panel in the homepage. 

    The details of the transformer and mosfet are provided in the BOM list.

    Thanks and Regards,

    Atul

  • 0 in reply to Atul_Kulkarni
    Intellectual 530 points

    hi  Atul Kulkarni23 ,

    I know the WEBENCH ,  but  also  I had checked the transformer( the recomand by WEBENCH), the datasheet of  the transformer  notes the inductan base is 9.7uH, but  WEBENCH  notes  Lp is 38.8uH, so  I have no idear ,   so  I just want to know how to design the transform。

  • 0 in reply to user5368470
    Genius 4910 points

    Hi User,

    Sorry for the delayed reply.

    Please find the below equation for calculating inductance.

    Lprim = Vin * Dutycycle/(fsw *  Delta_IL)

    where Delta_IL = In_Average/Dutycycle

    In_Average = Pin/Vin

    Regarding the datasheet of the transformer please note that for the current design configurable transformer (749196531)is selected wherein the primary inductance of the transformer can be changed by changing the connections at the primary side.

    For example if 12 and 2 are connected then the total inductance is Lprim*2^2.

    Since Lprim = 9.7uH the total inductance calculated is 9.7*4=38.8

    Transformer design involves iterations and lot of variables like calculation of AWG, choosing appropriate flux density, Number of turns,  Layers, Strands, Kg(core geometry factor), WEBENCH designer runs an algorithm to calculate the above parameters for a calculated inductance value.Currently we don’t have excel file for these calculations.

    Thanks and regards,

    Atul Kulkarni

  • 0 in reply to Atul_Kulkarni
    Intellectual 530 points

    hi Atul ，

    so happy to receive your reply,  this is very useful to me, thanks . best regards.

  • 0 in reply to Atul_Kulkarni
    Intellectual 530 points
    HI Atul,
    if 12 and 2 are connected then the total inductance is 38.8, and what about NP/NS? since DATESHEET is 1:1:1:1:1:1， if 12 and 2 are connected then the NP/NS calculated is 2:1？？？is it right?
  • 0 in reply to user5368470
    Genius 4910 points

    Hi,

    The secondary to primary turns ratio information is provided in the Webench under transformer BOM .

    Thanks and Regards,

    Atul

  • 0 in reply to Atul_Kulkarni
    Intellectual 530 points
    Hi Atul,
    the transformer (749196531)is not sold，I will choose transformer （749196541），Since Lprim = 7.6uH， 12 and 2 are connected then the total inductance is Lprim*2^2=30.4uH, is this ok？
    from Lprim_min = Vin_min * Dutycycle/(fsw * Delta_IL)=16*0.45/400k/1.736=10.36uH-----VIN_MIN=16V, dutycycle_max=0.45, fsw=400khz,
    Delta_IL = In_Average/Dutycycle=0.78125/0.45=1.736, In_Average = Pin/Vin_min=12.5/16=0.78125A, Pin=PO/η=10/0.8=12.5W.
    is it right? calculating inductance is 10.36uH, but actual choose 30.4uH, so other parameter by Webench need to change??
    for example RT? mos? Cout? do you have user guide of LM5022 about flyback technology? not boost technology.
    best regards
  • 0 in reply to user5368470
    Genius 4910 points

    Hi,

    Yes you are correct regarding the primary inductance calculation of 749196541 transformer.

    You can contact the vendor for 749196531 transformer on findchips.com regarding the order.

    We are using VinMax in calculating the primary inductance. So updating 16V with 40V comes around 26uF in your calculation.

    Currently we do not have user guide for LM5022 flyback. Kindly apologise.

    Thanks and Regards,

    Atul

  • 0 in reply to Atul_Kulkarni
    Intellectual 530 points
    hi Atul,
    the webench tools create the design for LM5022 for my conditions, the Nmos is CSD19537Q3(the recomand by WEBENCH), Regarding the datasheet of the NMOS, Qg=16~21nc,ton=5ns,tr=3ns, the I_driver calculated is 21/(5+3)=2.625A; but also Regarding the datasheet of the LM5022, the max I_driver is 1A. so can you give me some suggestion about how to choose? thanks. best regards
  • 0 in reply to user5368470
    Intellectual 530 points
    Regarding the datasheet of the BSC190N15NS3G by infineon , Qg=31nc, ton=15ns,tr=53ns, the I_driver calculated is 31/(15+53)=0.456A; This NMOS matches the drive capability of LM5022， am I right?
  • 0 in reply to user5368470
    Genius 4910 points
    Hi,

    We have set of equations derived to calculate Mosfet parameters like Ids,Vgs and Vds depending on frequency and given input output conditions after which Mosfet is selected. The other parameters such as Coss,Qg,rds are by products of selected mosfet.

    Thanks and Regards,
    Atul
  • 0 in reply to Atul_Kulkarni
    Intellectual 530 points

    hi Atul,

    so happy to receive your reply . calculate Mosfet parameters   VDS=VIN_MAX+Vor+Vleg ,  Vor=n*(vo+vf);  n=vin_min*Dmax/{(vo+vf)*(1-Dmax)}=16*0.4/(8+1)*0.6=1.185---choose  n=1.2; so vor=1.2*(8+1)=10.8V,

    and also  VDS=40+10.8+Vleg=50.8+Vleg---choose  VDS=100v;   According  the formula  :Pout=η*VIN*D*Ids*0.5  (η=0.8, Dmax=0.4, VIN_min=16V)---Ids_max=3.9A--choose Ids_max =10A； so  CSD19537Q3 (100V, 9.7A) and  CSD19534Q5a (100V, 10A)  meet  VDS and Ids,  now just  calculate Idrive capability of  NMOS ,  CSD19537Q3 datasheet  parameter Qg=16~22nC, t=ton+tr=9+14=23ns, I=Qg/t=16/23=0.6956A.;  L

    The LM5022 provides an internal gate driver through the OUT pin that can source and sink a peak current of 1 A   to control external, ground-referenced N-channel MOSFETs.  SO choose CSD19537Q3 . am I right?

    the second question :  I will choose  transform  Np/Ns: 1.25:1; and Np:Nau:1.11:1;  so  the auxiliary winding  is Vau=(Np/Ns)/(Np/Nau)*(vo+vf)=1.25/1.11*(8+1)=10.135V,  the LM5022 VCC=Vau-0.5=9.635V, according the LM5022 VCC( External voltage at V CC) is 7.5V~14v,  so the auxiliary winding votlage is ok,  am I right.  

  • 0 in reply to user5368470
    Genius 4910 points
    Hi ,

    Regarding mosfet selection , the selection routine runs taking voltage rating, current rating and thermal considerations into the account. Currently rise time and fall time are not considered during selection.
    The transformer calculations provided by you are correct. Could you please let us know the reason why turns ratio (1.25:1 and 1.11:1) is chosen.

    Thanks and Regards,
    Atul
  • 0 in reply to Atul_Kulkarni
    Intellectual 530 points
    hi Atul,
    The transformer calculations n=1.2 , because no suitable transformer can be found, only choose n=1.25； and the third winding pride to VCC（external 7.5VDC~14VDC），
    so need 7.5/9=0.833 <VCC/vout<14/9=1.55, 0.834<Nau(the third winding)/Ns(the vout winding)<1.55, Np/Ns=1.25, Np/Nau=1.11, then Nau/Ns=(Np/Ns)/(Np/Nau)=1.25/1.11=1.12.

    Verify VCC voltage： 9*1.12=10.13V --match the VCC supply 7.5V ~ 14V； Dmax=(VO+VF)*n/{(VO+VF)*n+VIN_min}=9*1.25/(9*1.25+16)=0.4128, vor=n*(vo+vf)=11.25.

    The transformer 750311385 ：L=15uH Ist=6.75A

    the first calculate: fsw=400k delta_Ip=VIN_min*Dmax/f*L=1.1008A .

    the second calculate: fsw=400K, Pin=POUT/η=12.5w, Iav_max=Pin/Vin_min=12.5/16=0.78125A, Ip=Iav/D=0.78/0.4128=1.89A

    so The transformer 750311385 is suit for my design.

    do you agree with my calculate？
  • 0 in reply to user5368470
    Genius 4910 points
    Hi ,

    All the calculations looks fine. Please note the change in calculation of Ipeak.

    Ipeak = Iavg/D + Ipp/2.
    So in this case Ipeak comes out to be
    Ipeak = 1.89 + 1.1008/2 = 2.4404A.

    Thanks and Regards,
    Atul
  • 0 in reply to Atul_Kulkarni
    Intellectual 530 points

    hi Atul,

    thanks,  I have begin to design schemtatic. best regards.