concept understanding: Inrush current limit circuit working

balasubramani r

Other Parts Discussed in Thread: TIDA-01495, TIDA-010015

Hi Everyone!

I recently come to visit this active inrush current limit circuit but curious how it is working . Please feed me some info regarding the working .

Ref image added here:

is there any application notes available for this setup, i have searched but i couldnt found nearby sch itself. Suggestion and inputs are welcome.

over 5 years ago

0 LeonardEllis over 5 years ago

TI__Guru 71526 points

Hello balasubramani r,

There are a number of AppNotes related to Inrush Current, depending on what the application is:

Managing Inrush Current (Rev. A)

Taming linear-regulator inrush currents

Limiting DDR Termination Regulators’ Inrush Current and Capacitor Selection

Combining Inrush Current Limiting with PFC for White Goods Motor Applications

94.5% Efficiency, 500-W Industrial AC/DC Reference Design

Please review these, if there are still questions, please provide more information on what the application is, what is the overall circuit your schematic sections were derived from.

Regards,

~Leonard

0 balasubramani r over 5 years ago in reply to LeonardEllis

Expert 1170 points

Hi Leo,

Thanks for the notes. Will go through the note and come back to you soon.

And by the way this circuit will be used in smps for inrush current limit.

I have seen many application just using NTC in series at the input ,of course heat dissipation considered here and this NTC was replaced with mosfet and fixed resistor . What im curious is why it is connected in series with High voltage capacitor. How this is working here and logic behind the connection with capacitor?

0 LeonardEllis over 5 years ago in reply to balasubramani r

TI__Guru 71526 points

Hi balasubramani,

Had not heard back from you, just checking on the status and your research. Let me know where we can assist once you have the requirements further defined.

And do you have an example schematic of the NTC/cap circuit you described?

Regards,

~Leonard

0 balasubramani r over 5 years ago in reply to LeonardEllis

Expert 1170 points

Hi Leo,

The following notes not exactly describing the required information. If we took this TIDA-010015,TIDA-01495 we have this inrush protection circuit but not well defined description in the design notes. It least want to know how this resistor and mosfet section done and how this mosfet triggered with respect to initial power ON condition.

Kindly let me know further information. Im eager to know how this setup will work.

0 Salil over 5 years ago in reply to balasubramani r

TI__Expert 3860 points

Hi Balasubramani,

The circuit consists of a comparator and a MOSFET switch. While the power supply is initially turned on, the bulk capacitor will get charged through RF1 (which is a high inrush capable, fusible resistor). This will limit the inrush current to a safe limit. When the bus voltage is built to a sufficiently high level, the U13 comparator will bypass this resistor by turning on Q10.

Regards,

Salil

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concept understanding: Inrush current limit circuit working

Managing Inrush Current (Rev. A)