Question about "Turn off display" by Vista Power Plan

I found a problem regarding to turn off display by Vista Power Plan on a
laptop PC:

1. I set the display off after 1 min when AC plugged.
2. I remove AC adapter but keep Battery only.
3. I put system in idle about 1 min.
4. I plug AC adapter again, the display off immediately.

My question is, because I set the display off after 1 min under AC mode, but
actually I've removed the AC adapter, and the DC display off I set to 0
min(disable), so why after 1 min I plug the AC adapter back and the display
off immediately? I supposed that when I plug AC adapter back then the counter
will be reset, and display will be off after 1 min idle but not immediately,
is that Vista design or bug?

Does anyone know this issue?

"lasthero" wrote:

> I found a problem regarding to turn off display by Vista Power Plan on a
> laptop PC:
>
> 1. I set the display off after 1 min when AC plugged.
> 2. I remove AC adapter but keep Battery only.
> 3. I put system in idle about 1 min.
> 4. I plug AC adapter again, the display off immediately.
>
> My question is, because I set the display off after 1 min under AC mode, but
> actually I've removed the AC adapter, and the DC display off I set to 0
> min(disable), so why after 1 min I plug the AC adapter back and the display
> off immediately? I supposed that when I plug AC adapter back then the counter
> will be reset, and display will be off after 1 min idle but not immediately,
> is that Vista design or bug?