if you attempt to operate your i5160 on 65watt ac adapter, your note may or may not boot, but mobo mosfet voltage reg's will burn up

there is a certain similarity between your question and the control room at chernobyl ...

Well...I thought that may be the case. In the interim, I looked at the maximum rating on the bottom of the notebook, and it's maximum is twice that of the maximum supply ratings on the 65W adapter.

I wonder why they added it to the box? Thanks for the info.

Carl

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@kwokPC wrote:

if you attempt to operate your i5160 on 65watt ac adapter, your note may or may not boot, but mobo mosfet voltage reg's will burn up

there is a certain similarity between your question and the control room at chernobyl ...

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Ugh. The charging MOSFETS will NOT burn up. Supplying insufficient wattage to the charging circuits will simply not power the laptop and may cause a warning. Nothing will burn up.

Comparing a notebook charging unit to a fission reactor core is silly, and you know it. They don't operate even a little alike.

Show me some sort of evidence that an undercurrent situation will cause the MOSFETs to burn up. The vast majority of of MOSFET based circuits sold today include overheat protection of some sort, and these are only needed when there is an OVERcurrent condition, not an undercurrent condition.

Having experience in high FR gaming tells me nothing about the overheat conditions of a MOSFET. I do, however, have 10 years experience working with radio controlled devices, all of which use MOSFETs extensivly in the speed controls. In that time, i have never seen a MOSFET burn up due to low battery current. Know why that is? because the physics don't say that they will. Its a transistor at heart - it either passes current or not. If its too little, the device just wont operate.

I would love to see documented somewhere that a low current situation will cause MOSFET failure and overheating.

Using a underpowered adapter with the notebook probably won't hurt anything. It won't power your laptop, but it wont burn up either.

Message Edited by mattcowger on 11-08-2004 04:17 PM

engineerCarl & kwokPC can play abit, but your post encourages others to try undersized ac adapter while traveling w/ their notebook - and the joke needs to stop now...

I have worked with TI then start-up Intel & have also lectured in semiconductor design - let's not compare backgrounds

we are discussing switching type ac to dc converter with closely regulated output - FYI  universal voltage adapter is designed for max ac mains of 240volts 13amps - not merely 120volts 5amps

we are discussing specific condition - appliance (notebook) requires minimum input of 19.5vdc/120watts and ac adapter is rated maximum output of 19.5vdc/65watts

for regulatory compliance (UL CSA CE etc) the crowbar protective circuit is located in ac adapter not notebook mobo - when you create under-current condition at appliance (output side) of ac adapter, first thermal limit sensor will call up voltage limit increase (dc) to compensate for current demand of appliance (120watts/19.5vdc needed - only 65watts/19.5vdc available) then high thermal limit reached due to overheating mosfet junctions, begin shutdown of dc output (thermal contact set opens - however, if high temp spike is rapid, crowbar circuit on ac input side will see as mains short and immediate clamp ac input side

while this has been taking place in the switching power supply circuits of the ac adapter, the on-board appliance (notebook) mosfet based power supply (dc to dc converter) is seeing rapidly falling dc voltage level - rapidly increasing current demand from cpu/chipset/ram/hdd - with subsequent increase in mosfet frequency to compensate - mosfet junction(s) thermal limits reached immediately with permanent damage resulting  -  all BEFORE ac adapter thermal & short circuit protective circuits function  -  and there is significant emf kickback toward notebook

A Gradually Discharging Battery Absolutely Does Not Act This Way!

 

 

 

 

I'm not suggesting you don't have an EE background, only that a notebook PS will not burn up the charging circuit.

Show me ONE instance in which this has happened, and I'll listen to you. It may be possible under the VERY limited and not very common circumstances you gave, but all notebooks have protections against this.

Again, show me where it has happened, and I'll believe you.

matt,

notebook design is driven  by cost & "reasonable operating conditions"  -  further to control all-up-weight, there are stringent circuit power requirements  -  there is an unbreakable linkage between voltage and current  -  notebook mobo on-board power supply circuits are minimized to control case interior temp rise and are completely dependent on external ac adapter providing adequate dc voltage + wattage 

"reasonable operating conditions" implies that a 19.5vdc/120watt i5160 should tolerate a 19.5vdc/90watt ac adapter Without sustaining permanent circuit damage  -  however, to attempt to use 195vdc/65watt ac adapter is deliberate user misuse/abuse and is not within the design brief or product liability laws  -  so the on-board mosfet junctions will v. badly overheat  -  dell and compal (odm) are not obligated to prevent this and do not

the only obligation is to prevent a "continuous short circuit state" in ac adapter and this is provided

manufacturers of mosfet devices clearly discuss allowable thermal "rise time limits" within which permanent damage will not occur - if these are exceeded, junction interface electron depletion/junction interface lattice damage/lattice voids will occur, permanently damaging mosfet