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Original question:

LM5155: LM5155 Boost Output to 200V+/-10%

LM5155: LM5155/56 Flyback Controller Calculation sheet verification

Mahammadirfan Saiyed
Prodigy 30 points
Part Number: LM5155


Hello,

HelloI want to make 200V ,10-30mA max from battery with minimum 3V operating worst case.

Hello,

I already discussed few things with below link:

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1573617/lm5155-lm5155-boost-output-to-200v--10?tisearch=e2e-sitesearch&keymatch=LM5155#

As that thread closed and I want to do more deep dive for better understanding in simulation and circuit to be functional. I have attached the conclusive sheet with all my details of design in it for your verification and input.

I have selected the parts as follows:

LM5155_56_Excel_Quickstart_Calculator_for_Flyback_Regulator_Design_16102025.xlsx 

To match the output requirement duty cycle changed to 87% from 40% initail, Inductor current ripple ration changed to 200% from 60% so peak primary current becomes 1.03A <1.3A saturation current of coupled inductor.

Rs and RSL updated to 34mohm from 2mohm initial and 2.384Kohm so Actual peak inductor current limit falls below Isat = 1.3A.

Rcomp, Ccomp and CHF kept same : 1.2kohm, Ccomp = 220nF, 720pF.

I am not adding any other part other than shown below in schematic. 

https://www.coilcraft.com/en-us/products/power/coupled-inductors/1-n-shielded-coupled/lpr/lpr6235/lpr6235-253l/

As I am using the LPR6235-253L coupled inductor with mosfet, diode and cap to make 200V output using Non-Isolated single stage flyback output.

Mosfet: IPD60R360P7ATMA1

Diode: FR1M

 

image.png

I hope it works without any issue.

Please verify and provide your feedback.

 

Thanks

  • 0
    TI__Mastermind 18295 points

    Hi Mahammadirfan,

    Thanks for using E2E.

    Please make sure you select a MOSFET that can fully turn on with 3V. The one you selected is not suitable. It does not need to be 600V rated. 50V is enough.

    Also ~90% duty cycle is very high for a flyback. The problem is, that the time to deliver the energy to the output in the off-phase over the diode is very short. 

    But as you have very low power, it could work. 

    Best regards

    Moritz

  • 0 in reply to Moritz
    Prodigy 30 points

    Hi Moritz,

    Thanks for your feedback.

    I am trying to build the circuit on the GPB first but unable to get the output voltage which is only 1V.

    I have shorted the VBIAS=VCC=9V , UVLO=9V , Fsw =250KHz has been set.

    Please find the waveforms for Gate and Drain pin switching of Mosfet. Let me know what can be done further or what is wrong ?

    I haven't connected any load yet.

    Thanks,

  • 0 in reply to Mahammadirfan Saiyed
    TI__Mastermind 18295 points

    Hi Mahammadirfan,

    Can you please share the schematic you built as aPDF? The hand drawn version is very hard to read. 

    Also what do you mean with GPB? Did you not build a PCB? Can i please see a picture of your setup?

    Best regards

    Moritz

  • 0 in reply to Moritz
    Prodigy 30 points

    Dear Mortiz,

    We first wants to evaluate it on GPB (General Purpose PCB ) and not on PCB so we can do minor modification if needed.

    Please find the attached PDF of schematic. Kindly check and provide your feedback on this. Meanwhile I will also update from my end.

    ThanksPower Suppy-200V_SCH_New.pdf

  • 0 in reply to Mahammadirfan Saiyed
    TI__Mastermind 18295 points

    Hi Mahammadirfan,

    I dont think that the desig will wrk properly on a GPM. The layout and small loops wth low paasiics ae important in SMPS designs.

    From the schematic it looks like the MOSFET  is conected in the wrong way? The gate pin of the FET has to be connected to the gate pin ot he IC. The drain of the FET has to be connected to the inductor.

    The rest of the schematic looks ok.

    Bestregards

    Moritz

  • 0 in reply to Moritz
    Prodigy 30 points

    Dear Mortiz,

    Thanks though the schematic connection is a typo and in reality its a correct connection.

    The circuit works after changing compensation network and snubber circuit.

    Do you have the similar chip which has a low cost and same functionality ?

  • 0 in reply to Mahammadirfan Saiyed
    TI__Mastermind 31580 points

    Hi Mahammadirfan,

    Moritz is out of office today, so I will take over in the meantime.

    LM5155 is already a very low cost solution and I am not aware of any cheaper devices within our portfolio.

    Best regards,
    Niklas

  • 0 in reply to Niklas Schwarz
    Prodigy 30 points

    Dear Niklas,

    Thanks

  • 0 in reply to Mahammadirfan Saiyed
    Prodigy 30 points

    Dear Mortiz,

    We have made Custom PCB and during the load testing we are facing an issue of heating on Inductor and other parts as well as output Voltage drops from 200V to 110V and decreasing continuously even at 10mA load.

    Input - Battery 3.7V

    Load : 10k/4W

    Output voltage at No load : 200V stable.

    Output Voltage at said Load : 109V and output current is 10mA and both decreasing continuously.

    What can be the issue ? Please share your email Id so I can share the design file for your review.

    Thanks,

    Mahammadirfan

  • 0 in reply to Mahammadirfan Saiyed
    TI__Mastermind 18295 points

    Hi Mahammadirfan,

    Can you please fill out the excel calculator? Also please attach the transformer datasheet. 

    Aslo please send scopeshots of Vin, Vout, switchnode and CS signal foor me to analyze?

    Best regards

    Moritz