soft start on 1000W switch mode PSU?

[megoodsen]

Hi,

I'm using a Cosel PBA1000F 5V 1000W switch mode PSU, and I really want
to be able to soft start it, both to bring up the 200A 5V DC available
gently, and reduce the quoted 40A inrush current.
I've done this in the past on linear PSU's, usuing a simple R in the AC
line that is switched out when DC gets up to voltage, but I suspect
this won't work on a switcher, especially one such as mine with very
wide AC input voltage.

This particular PSU does have some control pins which may be usable
(see below links) but I would prefer a generic switcher approach.

Can anyone suggest a fairly simple circuit/approach?

Thanks.

links to Cosel PBA1000 data:
http://www.cosel.co.jp/en/products/parts_products/se_pba1000f.pdf
http://www.cosel.co.jp/en/products/parts_products/me_pba.pdf

 

[Phil Allison]

** Hotshit Groper Alert !!

I'm using a Cosel PBA1000F 5V 1000W switch mode PSU, and I really want
to be able to soft start it, both to bring up the 200A 5V DC available
gently, and reduce the quoted 40A inrush current.

** Get a grip on yourself - fuckhead.

Even a 30cm colour TV has an inrush current typically more than 40 amps.

So do most electronic appliances rated over 200 VA due to transformer
primary surges alone.

What is your problem ??????






........ Phil

 

[Paul Mathews]

Hi,

I'm using a Cosel PBA1000F 5V 1000W switch mode PSU, and I really want
to be able to soft start it, both to bring up the 200A 5V DC available
gently, and reduce the quoted 40A inrush current.
I've done this in the past on linear PSU's, usuing a simple R in the AC
line that is switched out when DC gets up to voltage, but I suspect
this won't work on a switcher, especially one such as mine with very
wide AC input voltage.

This particular PSU does have some control pins which may be usable
(see below links) but I would prefer a generic switcher approach.

Can anyone suggest a fairly simple circuit/approach?

Thanks.

links to Cosel PBA1000 data:
http://www.cosel.co.jp/en/products/parts_products/se_pba1000f.pdf
http://www.cosel.co.jp/en/products/parts_products/me_pba.pdf

Switching power supplies generally have 2 surges:
1) Inrush current to charge primary filter capacitors (on the mains
side)
2) Current to charge secondary capacitors (on the secondary side)

The resistor in series will limit #1, and it is not uncommon to use a
power resistor and a shunting relay or thyristor this way. To limit
inrush to 100 amps peak with 220 volt mains, you'd use about 4 ohms and
close the shunt after 10 to 20 milliseconds. You can also consider
using Negative Temperature Coefficient (NTC) power resistors for this
purpose (instead of relay and resistor). NTCs have a cold resistance
several times their hot resistance, so limit power-up surges for cold
starts. They fail to limit surges once hot, though.
The second surge will most likely be under electronic cycle-by-cycle
current control at the switching frequency, including a soft-start
sequence, so usually not a problem.
Paul Mathews