Volts and amps combine to confuse.
Yes — with a couple of caveats, of course.
If it’s not made specifically for your particular computer, getting the right power supply is important and involves matching voltage, amperage, and polarity.
Each has different constraints.
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For power supplies or chargers:
- The voltage must match.
- The amperage must match or exceed that required by the device.
- The polarity of the connection must be correct.
The input line voltage (wall or “mains” power) must be supported, but is unrelated to compatibility with the device being charged or powered.
The voltage provided by your charger must match that expected by the device being charged.
When replacing a charger, this is easy to determine: it’ll be listed on the old charger. In your case, the old charger supplied 19 volts, so your replacement must also be 19 volts.
It’s very important to get the right voltage. Some devices are tolerant of variations and work just fine. Others, unfortunately, do not. Depending on how different the supplied voltage is from what’s required, the device may simply fail, it may work “kind of”, or it may appear to work at the cost of a much shorter lifespan.
If the voltage is off by enough, it can damage your device.
And here’s the problem: there’s no way to say what’s enough or too much. It varies from device to device. Some may tolerate a wide range of input voltages, while others are extremely sensitive to even the smallest error.
Sidestep all those unknowns and make sure to get exactly the right voltage from the start.
The amperage provided by your charger must match or exceed what the device being charged requires.
The amperage rating is the maximum amount of power it can supply.
A device being charged will only take as much amperage as it requires. If your device needs 0.5 amps to charge, and your charger is rated at 1.0 amps, only 0.5 amps will be used.
The problem, of course, is the reverse: if your device needs 1.0 amps, but your charger is rated at only 0.5 amps, then any of several problems could result:
- Charging may not work at all.
- The device may charge extremely slowly.
- The power supply may overheat.
- The device being charged may be damaged.
Thus, as long as you replace your power supply with one capable of providing as much or more amps than the previous, you’ll be fine. To be clear: there is nothing wrong at all with having a charger capable of providing more amps than needed.
The polarity of the connection between your charger and device must be correct.
Most power supplies provide their output on two wires: one labeled (+) or positive, and the other (-) or negative. Which wire is which is referred to as polarity.
Polarity must match.
Here’s the catch: just because the physical plug fits into your device does not mean that the polarity is correct.
Particularly when it comes to popular circular power connectors, make sure the expectations match. If the device expects the center connector to be positive and the outer ring to be negative, your power supply’s connector must match. There’s no getting around this.
Failure to get it right at best just doesn’t work, but at worst can damage the device.
Look carefully for indicators on both the power supply and the device.
The good news here is that there are some standards where the polarity is always correct. USB power supplies, for example, are the same no matter what.
Input voltage — aka “mains” or line-voltage — is, of course, critical. Plug a device expecting 110 volts into a 220 volt socket, and you’ll probably see sparks followed by darkness as the circuit breaker trips. You’re also likely to damage the device.
Most of the time.
When it comes to modern power supplies, however, almost anything works.
If you look closely at the small print on many power supplies, you’ll see they’re rated for anything from 100 to 250 volts. This means most can work worldwide with nothing more than an adapter to account for the physical plug differences — no voltage transformer needed.
Check your power supplies before you travel, of course, but it’s very, very convenient.
Important: the input voltage and amperage ratings are unrelated to the charger’s compatibility with your device. What matters for your device are the output voltage and amperage ratings.