Views: 49 Author: Site Editor Publish Time: 2023-12-26 Origin: Site
Have you noticed that most laptops use a 19V AC/DC adapter or a 19.5V AC/DC adapter? The 19V and 19.5V standards have been widely adopted by various laptop manufacturers, ensuring a level of compatibility and interchangeability among adapters. This standardization allows users to use adapters from different manufacturers as long as they meet the specified voltage and current requirements.
Here you will notice that both values of 19V or 19.5V are close to 20V. So why not take an integer and set it to 20V? Why do many laptops run on 19 volts？
The interior of a laptop battery is composed of multiple cells. At present, it is mainly divided into 3 cells, 4 cells, 6 cells, 8 cells, 9 cells, 12 cells, etc. The more cells there are, the longer the standby time is. A polymer cell is nominally 3.7V. The 3-cell battery pack uses three 18650 cells connected in series, which is 3*3.7V=11.1V. A four-cell battery is 3.7V×4=14.8V. A six-cell battery generally has six cells divided into two groups, three in each group. The three cells are connected in series and then in parallel, the voltage is 3.7V×3=11.1V.
Therefore, the battery voltage standard of most laptops on the market is around 14.8V. The charging process requires a certain voltage loss, so a higher voltage is required for charging. There are two DC voltages inside the notebook, one for the display and fan, and one for the entire motherboard. Usually, 12V is used for the display and fan, and 5V is used for the motherboard. To keep the voltage stabilizing circuit inside the notebook at 12V or 5V, the power adapter voltage must be higher than 12V, and 19V is enough to provide sufficient input voltage for the laptop's internal voltage stabilizing module to start the hard drive and discrete components and large LCDs to meet the working requirements of these components.
Laptops are mainly powered by lithium batteries, which are usually rated at 14.4V or 15V. To make full use of battery energy, increasing the battery voltage to 19V can achieve higher battery capacity efficiency.
Laptop motherboards usually adopt low-power designs. To meet the working voltage requirements of various electronic components and reduce power consumption as much as possible, 19V is regarded as a relatively reasonable voltage choice.
The design of laptop power supplies often follows industry standards and guidelines. These standards may recommend or limit the voltage within a certain range to ensure safety, reliability, and compatibility.
For example:
IEC 62368-1
An internationally recognized safety standard that tests and certifies power supplies. An IEC62368-1 power supply can be rated up to 8A for open-circuit output voltages ≤12.5V.
UL 1310
A standard that applies to power supplies within a limited output current and output voltage range. The UL 1310 nameplate rating is limited to 5A when the open-circuit output voltage is ≤20V.
If you keep the voltage at 20 volts or less, safety certification becomes easier. To ensure that it is within the limits of manufacturing tolerances, it is generally reduced by some percentage, setting it to 19V or 19.5V is very reliable.
With the need to ensure safe voltage and computers, why not choose a lower voltage?
If you choose a lower voltage, a higher current is required to ensure the power supply needs of the computer, and a thicker cable is required. The cable is thicker and the device has a greater chance of getting hot. 19 volts provides enough power to run devices efficiently without causing overheating or other issues. Therefore, 19V AC/DC power supply adapter is a safe and environmentally friendly choice.
Not every laptop uses a 19V AC/DC power supply adapter. Depending on the make and model, the voltage of the adapter may vary. Some laptops may require a higher voltage, such as 20 volts or 24 volts, while others may require a lower voltage, such as 16 volts or 12 volts. Therefore, when purchasing a new power adapter, be sure to understand the specifications and voltage requirements of this unit and choose the appropriate adapter.
