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Power Supplies Basics: How To Replace A Notebook, Laptop, Netbook or Tablet Power Supply Adapter

Updated on June 23, 2013

Portable Computing Options

Laptop, netbook or tablet? All options offer computing capabilities on the go, but there are differences between their characteristics.
Laptop, netbook or tablet? All options offer computing capabilities on the go, but there are differences between their characteristics. | Source

Batteries

The battery of a small factor laptop, better known as "netbooks". All portable computers need batteries as their source of power.
The battery of a small factor laptop, better known as "netbooks". All portable computers need batteries as their source of power.

Popularity Of Portable Computing

Portable electronic devices are very common among people nowadays. Smartphones, music or video players, portable computers such as notebooks, tablets or netbooks are extremely popular since they provide computer and other capabilities on the go. Businessmen, computer geeks or 'gadget people" are not the only ones who choose to carry their device with them wherever they go nowadays, as a result the digital electronics market of this particular field is on the blossom and will stay for many years to come, as new technologies, features and added connectivity methods appear.

Such electronic devices will of course include batteries as their operating power source. Though the batteries kinds, capacities and power will differ between devices, one is sure: all batteries need to be charged often by an outside power source, usually typical power electricity grid (110V or 230V depending on where you live) or DC power source, such as 12V car battery (when the device is carried or used often inside car) or 5V power supply, for example a typical USB socket of a desktop computer running from the electricity grid.

A typical power supply adapter.
A typical power supply adapter.

Power Supply Explanation

For this reason, portable computers come with a power supply from the manufacturer. Power supplies or power adapters, as often called, are usually large black "boxes", typically rectangular, which store sophisticated electronic circuit designed to convert AC (alternating current) electricity, like the one used by all home appliances, to DC (direct current) electricity which will charge the batteries. Such conversion is always required on any kind of battery charger which will run off electricity grid, because batteries always supply DC voltage. The power supply includes a wire which is at the DC side and therefore ends up at the charging socket of the device, and a wire for the AC side, which ends to a typical electricity socket.

Size Of Power Supplies

The size of the power supply, meaning the sealed closed box with the electronic conversion circuit, is relative to the power needed by the device and its batteries. Large portable computer, such as large screen and large form factor notebooks come with a big power supply, typically the size of a thick wallet. A large factor box is needed because as power requirements go up, there is need of larger transformer and coolers to dissipate the heat. A laptop commonly consumes 90-120W of electricity, which, in electronic terms, means high current and eventually need of thicker electricity wiring inside the supply.
Netbooks typically have smaller power requirements, most will consume 40-60W of electricity. As a result, their power supplies are way smaller, only slightly larger than a typical phone charger. Tablets also include smaller batteries, have less power consumption and come with small power supply.

A power supply (charger) made by Sony. The tag clearly states the input and output voltage and current, along with other identification serial numbers and country of origin.
A power supply (charger) made by Sony. The tag clearly states the input and output voltage and current, along with other identification serial numbers and country of origin.

Power Supply Characteristics

Power supplies always have a tag which indicates a model number, country of assembly, other identifications numbers and the most important: voltage and current. On a power supply tag you will be notified of the primary voltage and current (primary is the AC side) and the secondary voltage and current (secondary is the DC side where the wire connects to the portable device). Some power supplies also mention the power; even if your adapter doesn't state it, however, you can easily calculate the power it can handle by multiplying secondary voltage by secondary current.
For example, a supply adapter which provides 18V and up to 4A current at secondary can be used for devices consuming up to 72W.

A typical universal power supply will include a switch to choose the required Volts and many different tips to be able to substitute most laptop original chargers.
A typical universal power supply will include a switch to choose the required Volts and many different tips to be able to substitute most laptop original chargers.

What To Look For When Choosing A Replacement Power Supply

Many companies offer power supplies which can be used for various portable computers. These power supplies are typically called "universal" or "compatible" and can be of great use to anyone who has lost or damaged the original power adapter (for example burnt due to a power surge, overheating or physical damage).

When choosing a universal power supply, you need to double-check a couple of things so you can be sure that it is compatible and a good replacement for the original. Here are the things you ought to check:

  • Secondary Voltage: you must choose a universal power supply which can be adjusted to provide the exact voltage that the original supplied.
  • Secondary current: the compatible supply should be able to provide at least the current the original provided. If the new one outputs higher current than the original, then it is a great choice. Do not worry that you might burn the computer or damage the battery by choosing a supply with higher current; reason is simple, power supplies output the current they are "asked" to output. That means that battery will decide how much current it needs at any given time, and it will "ask" the adaptor to supply that current. If the adaptor can only supply less than what the battery needs, it will be working at its peak limit, generating much heat and eventually will burn out. That is why we ought to choose a universal power supply with higher current than the original. Besides, it will be functioning more effectively and for longer, with less heat, because it will not be working at its limits.
  • Last but not least, check the tip ends provided with the charger. The chosen supply should include a tip which is 100% compatible with the laptop power receptacle. Never use a tip which isn't exactly same to the original tip. And yes, though it might be weird to not choose a power supply because its tip isn't 100% same, you would be on the safer side if you just choose another one which comes with the exact tip for your computer.

Finally, if the store allows it, opt to bring your portable computer to the store so you try the charger before buying it. Some stores allow such, but still you should make all checks mentioned earlier; a seller could be pushing for sale a power supply which makes more profit to him, but will not be the ideal or safe choice for you.

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    • lesliebyars profile image

      Buster Johnson 3 years ago from Alabama

      This was very informative!!! I voted up and useful.

    • CyberFreak profile image
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      CyberFreak 3 years ago

      Thank you lesliebyars for your time and vote.

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