1. Home
  2. Electronics Design
  3. soft start on 1000W switch mode PSU?

soft start on 1000W switch mode PSU?

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:

formatting link
formatting link

Reply to
megoodsen
Loading thread data ...
** Hotshit Groper Alert !!

** Get a grip on yourself - f*****ad.

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

Reply to
Phil Allison

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

Reply to
Paul Mathews

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.