Solution for large inrush currents

Status
Not open for further replies.
L

Landsbytosse

Newbie level 3
Joined
Jul 8, 2010
Messages
3
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Location
Sweden
Activity points
1,303
Hi there,

I have a power supply with a filter, diode bridge and a large cap to hold the voltage close to DC. A NTC is mounted to minimise inrush but this is not enough due to its lose (Thinking Green )

When powering up large inrush currents are seen. Is there a cheap and easy way to elimnate this problem.

Using Relays acroos the NTC is not an option due to pysical sice of components.

Can i use a Triac triggered byt my 5V supply or uP? Or is a SCR the way to go? If anyone has a active solution or ider im all ears.

Cheers
 

Inrush Limitier

A relay is usually smaller than a triac, considering the required heat sink. A triac has a least 1 V drop, it's losses can't be
actually expected lower than of a NTC.

A couple of "oversized" MOSFET in an anti-serial circuit can work as an almost ideal electronic switch.
 
Inrush Limitier

Hi,
You should use a relay and upon power up, use the microcontroller or control circuit to isolate the load from the supply using the relay for a specified time, x seconds, after which you turn the relay on.

You could use a triac or SCR, but I think the relay is a better choice.

Hope this helps.
Tahmid.
 

Re: Inrush Limitier


The problem with this solution is size, i will not fit inside the case. So its not an option.

I thinkt the optimal solutions would be a MOSFET used as a relay to short a resister after X mS, but i have yet to get it to work when coupled up to the 5V supply insted of a microprocessor.
 

Inrush Limitier

You should mention the circuit's current rating. A reasonable solution depends on it, particularly required power component sizes. I also wonder where you get 5V DC. Do you use an additional transformer power supply?
 

Re: Inrush Limitier

I draw around 0.9A.

I have a microprocessor and 5V to control start of different fans. No trafo is used just a SMPS.

But the large cap needed after the filter to supply these fans draws very large current killing off Relays used to power the system on/turn it off.
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…