LM5001: LM5001

Durgaprasad Hitlalli

Part Number: LM5001
Other Parts Discussed in Thread: LMP8646,

Hello Team,

Attaching you the simulation from the webbench for my design.

I have a source of 24V and I cannot draw more than 2.4W from the same. This means I cannot draw a current more than 100mA from this supply. Alongside boost converter, it also has some other circuits to supply to. Therefore I would want to charge the output capacitor slowly. This means I want my input current to be limited to at around 40mA.

From the design, you can see that I have got big output capacitance of 2.5mF. Because of which, I have high inrush current while charging these capacitor.

Could you please help me slow down the charging time so that I can limit input current from the 24V power supply? Please suggest your methods that I can try.

P.S.: I cannot reduce the output capacitance as I would want to store the energy and keep in that for dedicated operation.

over 4 years ago

0 EM over 4 years ago

TI__Genius 11215 points

Hello,

Thanks for reaching out. Would you mind sharing your specs (Vin, Vout, Iout, switching frequency)? I cannot see the webench file/link but only an image attached to your thread. The inrush current is equal to I = C * dV / dT, where V is your output voltage and dT is the soft start time. To slow down the charge of the output caps you can increase the soft start time for example. Let me know if I can help you furthermore.

Kind regards,

0 Durgaprasad Hitlalli over 4 years ago

Prodigy 10 points

0 EM over 4 years ago in reply to Durgaprasad Hitlalli

TI__Genius 11215 points

Hello,

Thanks for your reply. Would it be a problem for your circuit to have a longer soft start time to reduce the inrush current?

Kind regards,

0 Durgaprasad Hitlalli over 4 years ago in reply to EM

Prodigy 10 points

I am completely fine with the start time even upto 60 seconds. Please suggest me methods to achieve longer start time with lower inrush currents.. Thanks.

0 EM over 4 years ago in reply to Durgaprasad Hitlalli

TI__Genius 11215 points

Hello,

In your schematic, the soft start capacitor is Css, to increase the soft start time you might want to increase the value of this capacitor.

Kind regards,

0 Durgaprasad Hitlalli over 4 years ago in reply to EM

Prodigy 10 points

I tried by increasing the SS cap value but it did not help!

0 EM over 4 years ago in reply to Durgaprasad Hitlalli

TI__Genius 11215 points

Hello,

Thanks for the feedback. In this case, since increasing the soft start cap did not help as expected, I would suggest the use of a current limiter like the LMP8646 https://www.ti.com/product/LMP8646?keyMatch=LMP8646&tisearch=search-everything&usecase=GPN

Kind regards,

0 AnBer over 4 years ago in reply to EM

TI__Mastermind 30110 points

Hi EM,

->Is softstart simulated in Webench?
May be it could help to assess what max current could be achieved with the max soft start.
can you confirm this type of simulation would work?

LMP8646 is quite expensive.
->Do you think that the below IC could be use for this specific LM5001 use case? Could you propose a schematics that would work with LM5001?
TPS1H100 40-V, 100-mΩ, Smart High-Side Switch as Current Limiter Reference Guide (Rev. B)

I look as well at the eFuse that could limit current:
https://www.ti.com/power-management/power-switches/efuse-hotswap-controllers/products.html#
->Do you think it can be an option?

Also there is an app note about Inrush current in general:
Managing Inrush Current (Rev. A)

Thanks in advance!

0 Brigitte over 4 years ago in reply to AnBer

TI__Guru 65170 points

Hello AnBer,

For a lower cost inrush current limit, please refer to this app note: https://www.ti.com/lit/an/slva912/slva912.pdf

Best regards,
Brigitte

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