I have a small Acer laptop whose mains transformer output is rated at 19 volts and 2.15 amp. This transformer has gone missing.
But i have another transformer for a Toshiba laptop whose output is the same 19 volts but is rated 3.42 amps. They both have the same socket and polarity.
Could I use the Toshiba transformer (even though it has the bigger amperage) on the Acer without doing any likely damage to it?
Yes.
As long as your replacement PSU is of the same voltage, which it is, then there is no problem, as long as it has a higher current capacity, which it has.
The only issue would have been if the replacement couldn't have supplied enough current, as it is you may find that the PSU runs a little cooler than before as you are under running it a bit, which is a good thing.
>Most probably yes as they are normally regulated to the correct voltage anyway. Its not like the old regulated bricks we used to have these days, its most likely switch mode and the charging circuit is in the laptop itself. Brian
Yes, the higher rating just means it's *capable* of supplying more current, not that it will try to force that much out. And if it's 19V then as has been mentioned I'd expect the regulation is done within the lappy.
It will take the same current as before and the transformer will run cooler.
You have to bear in mind "regulation" of Transformers.
Not as in rules, but the voltage output varies with the current drawn. Smaller currents drawn result in higher voltages out. Quite significant with small transformers. So check the open circuit and under load voltages. It will probably be OK.
Unfortunately the volts and current are shown in different ways in different patrs of the world. Some it's voltage at that current. And others it's the max voltage and the max current, (you don't get both at the same time)
The "transformer" is virtually certain to be an SMPSU, rather than a simple transformer, designed to cope with a wide range of input voltages and power requirements across a range of Tosh laptops.
But, these devices are not transformers. With ac in and dc out, they are power supplies. Hopefully they are properly regulated.
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So that would be a: ' yes you can safely use it'... ?
It would.
Check the label on the Tosh PSU. Typically it will specify input as a range e.g. 100-240 volts AC, 50-60Hz. To cope with that variation of input voltage the PSU *has* to have output voltage regulation.
It's not a "transformer", its a mains charging brick (SMPSU). That
2.15A rating is unusually small for a laptop. I suspect your "small Acer laptop" is in fact a "netbook" rather than a "notebook".If you're using it with a "small Acer laptop", it's probably just sufficient to power it with a small reserve of power available to slowly charge the battery at the same time. The higher rated charger will allow the battery to be charged at a higher rate under this condition of use (possibly at the maximum charge rate allowed that's otherwise only possible when the laptop is plugged in for charging alone.
As has already been said many times, it's the voltage that matters. The current rating is a maximum that the "transformer" will allow the load (your laptop in this case) to draw before it goes into current limiting mode[1].
Although it's perfectly true that the power management in the laptop itself takes care of generating the various internal DC supplies (5v,
3.3v and so on) as well as managing the battery charging current. The "transformers" are very tightly voltage regulated to meet the laptop makers' synthetically applied input voltage restriction to a specified "transformer" voltage, usually to within a tolerance of +/- 0.5v to 0.75v.The switch mode converters inside the laptop would in most cases be quite capable of using any voltage from 12 to 24 volts except for the fact that the laptop makers take the same attitude the inkjet printer makers have in regard to inkjet refill cartridges (a cash cow earner of extra revenue) and fit additional circuitry to exclude, in this case all voltages less than 18.5 and all voltages greater than 19.5 as being invalid.
It depends on the efficiency of the "transformer". Generally for the same efficiency class( typically class IV), the higher output "transformer" will also be physically larger so have a greater surface area through which to dissipate its waste heat. The effect of 'under running' a higher output rated supply will also help by reducing I^2 R losses.
Even so, it's definitely not a good idea to hide the charger under a fold or two of bed covers when using it in bed as my son discovered with a Sony laptop charger a couple of years back. Luckily for him, the overheat protection saved the charger from permanent damage by shutting down (it had gotten so hot as to be untouchable by a bare hand!).
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As has already been said many times, it's the voltage that matters. The current rating is a maximum that the "transformer" will allow the load (your laptop in this case) to draw before it goes into current limiting mode[1].
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Sorry! I forgot to add note[1].
[1] The constant current mode is the first stage of the current overload protection that guards against short cicuit faults on its output.Most laptop power management circuits (Dell and some HP models excepted) monitor for the resulting drop of voltage to control the battery charging whist the laptop is booted up and in use.
The power demand by the laptop varies from moment to moment depending on what tasks are running. The battery charging current is varied to hold the output of the charger in this 'Twilight Zone' of constant current operation to maximise the charging rate whilst the laptop is being used on a low power charger.
With a high power charger, this constant current condition will never arise and the charging circuit will be applying a fast charging profile optimised to the battery rather than attempting to 'make the best of it' with what's left over from a lower wattage charger.
If the charger is driven into this current limiting mode by a fault, the voltage will rapidly collapse due to the 'current foldback' kicking in below a set voltage threshold (probably a half volt or so below its normal output voltage setting).
Once the voltage has dropped below this critical voltage, the value of this constant current limiting becomes proportional to the output voltage resulting in a positive feedback process that rapidly ends with close to zero volts and a short circuit current of mere milliamps.
Simply disconnecting the fault condition from the charger's output will be sufficient, in most cases, to create a positive feed back condition whereby the voltage is rapidly restored to normal. Some units might require the mains input to be shut off/disconnected before it unlatches out of the overload shutdown condition (it depends on the philosophical attitude that happened to be in the designer's mind at the time).
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