Chargers and power supplies come in a wide variety of configurations. Choosing the right one is important. I'll look at a few of the parameters.
With a couple of caveats, of course.
Getting the right power supply – if it’s not made specifically for your particular model of computer – involves matching voltage, amperage, and polarity.
And each have different constraints.
Let’s start with the simplest.
The voltage output by your charger/power supply should match as closely as possible. In your case, you’ve got that covered: you had 19 volts before and your replacement candidate is also 19 volts.
When replacing an external charger for a battery-based device like a laptop or netbook, it’s important to get the right voltage. The device may work with voltages that are close, but often at the cost of shortening the lifespan of the batteries being recharged.
When replacing an external power supply, the same rule applies – except that you may be shortening the lifespan of the device by not getting the same voltage.
Or you may not.
Some devices are quite tolerant of voltage variations and will work just fine. Others, not so much.
Because there’s no easy way to know which category your device falls into, it’s best to simply get the right voltage from the start, if at all possible.
Many people are confused by amperage ratings and what they mean when it comes to power supplies and replacements.
One easy way to look at it is this:
- Voltage is provided by (or pushed) by the power supply.
- Amperage is taken by (or pulled) by the device being powered.
In other words, while the voltage is a constant and should match, the amperage is something that varies based on the devices need. Your computer will “pull” more amps when it’s working hard than when it’s not. The voltage will remain the same regardless.
The amperage rating of a power supply is the maximum number of amps that it’s able to provide if needed.
Thus, as long as you replace your power supply with one that is capable of providing as much or more amps than the previous supply, you’ll be fine.
If you replace the power supply for some reason with one that has a maximum amperage rating that is less than the previous and less than what your device actually requires, then you may end up with a burnt out or (at least) overheating power supply, and the device itself may not function, or may not do so well.
This one catches many people by surprise, especially when replacing simple or small power supplies with generic replacements.
Most power supplies provide DC (direct current) power via two wires labeled positive and negative. Polarity refers to which wire is which.
Just because the physical plug into your device matches doesn’t mean that the positive and negative connections are hooked up the right way. In fact, there’s often no real standard.
Particularly when it comes to popular circular power connectors, make sure that 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. If the device expects it the other way, the connectors must still match. There’s no getting around this.
Often, you’ll see some kind of indication on the power supply that will show which connector is negative or positive.
If you’re replacing a power supply that uses a custom connector used only by one manufacturer, then typically you don’t have to worry. Similarly, if the device is powered over a USB connector, that standardizes the connection, too.
In short, when replacing an external power supply or charger:
- Make sure that the voltage matches as closely as possible.
- Make sure that the new supply is rated to provide the same amperage or more.
- Make sure that the connectors match, both in physical form and in polarity.