Bleeding resistors -- why

[blueskull]

Have a question about my new PXI system.

The backplane has about 1A bleeding resistors on 5V, 3.3V and 12V rails on board, plus 1A on 12V using chassis mount resistors. Anyone can explain why did they do that?

My theory is that the PXI is a dynamic environment. Many cards can ramp up power consumption in no time, and since it uses a standard ATX power supply, it may not respond that fast under light load, so the chassis has a bleeding to ensure the PSU is properly loaded and ready to respond.

Don't know if that's the most reasonable explanation, but if that's the case, can I replace the archaic power supply with an Intel Haswell certified (rated for crazy fast di/dt) unit and remove the resistors?

I plan to run the PXI as a remote access box, so I expect it to be constantly powered on, saving a few tens of watts is crucial to me.

Thanks.

[Psi]

1A seems ridiculously large but yes, pre-loading some types of psu's does improve there response time
Sometimes the switchmode controller will go into various lower power switching states under very light loads (or no load) because it's more efficient.

hm.. so 1A  at 5, 3.3 and 12 rails using chassis mount resistors.
So 20.3 watts.
More likely it's part of a heater system to keep everything at a more stable temp. Maybe prevent it ever dropping below 0 C in cold environments.

Did you order the PXI - Antarctica edition?

[AndyC_772]

Minimum load to ensure the PSU remains in regulation even if there's no cards plugged in?