Adapters are power supply devices that change the electric-network voltage (in most cases) to values and type, suitable for the operation of various electronic appliances. Practically all the electronics that surrounds us works with much lower than the mains voltage and as there are no low-voltage electrical systems in our houses, we need to use devices that reduce the voltage from 220VAC to the suitable voltage planned for the operation of consumer electronics. Whether it’s a TV, a mobile phone, a PC, a laptop or a tablet, we need a mediation device to achieve low and often constant voltage. Sometimes the adapter is located in the electronic device such as a TV or a computer, and sometimes it is separated from it, such as a laptop, a phone, etc. and can be easily changed, if burned.
Adapters are divided into transformer and switching, stabilized and non-stabilized, adjustable and non-adjustable, adapters converting the mains voltage and adapters which are plugged in the cigarette lighter of the car and work with 12VDC constant input voltage. There are AC / AC adapters, DC / DC adapters and AC / DC adapters. AC / DC adapters are rectifiers which, according to the principle of operation, are divided into two main groups: linear and switching. AC / AC adapters are usually transformer and they don’t change the format and frequency of the input voltage. They change only the value of the output voltage. DC / DC adapters are used when we want to plug in a device designed to operate at 12VDC, which is the voltage supplied from the battery of the car, lorry, bus or ship, where the voltage is 24VDC. Adapters can be wired or wireless.
Adapters that provide the plugged-in devices with the necessary voltage but they cannot charge them are also called power supply devices, or just power supplies. There is another type of adapters that can charge the battery of a laptop, the battery of a wireless phone or wireless headphones. They are called chargers. Chargers are adapters which are non-stabilized. This means that at idle running the output signal will be about 20-30% higher than the signal for which they are designed. In other words, if we have a stabilized adapter which provides 9VDC at its output, at idle running we can measure 12 or even 14-15VDC at its output. Only when we connect load (consumer), its voltage will become close to the nominal one.
This type of adapter, as already mentioned, is called charger adapter. Chargers of this type have the function to switch-off after charging the battery, to which they are connected. This prevents the battery from overcharging which is harmful for it and shortens its life considerably. There are also stabilized power supplies, which are not equipped with the function to switch-off after charging the battery. They can be used as chargers, but must be monitored and disconnected in time, before the battery is overcharged.
The main parameters of adapters include their maximum power, which is usually indicated in amperes on their housing, the largest operating current, at which they can operate for long periods without overheating and damage, and their polarity. Adapters are interchangeable, but you must keep the following principle: an adapter with maximum current 1A can be replaced by an adapter with the same or larger maximum current, but not smaller. Adapters are also divided into ones with “+” in the center of the connector and “–” at the periphery and vice versa.
There are also multi-purpose adapters, whose connectors are detachable, and can change their polarity. You must be careful when using a multi-purpose adapter in the place of another one, which isn’t multi-purpose. You need to keep the polarity of the consumer, because if the polarity is wrong, this can damage the device, which will be powered by the adapter. You can measure the polarity of the consumer with a multi-meter to verify that the connector of the multi-purpose adapter is positioned so as to supply electricity with the same polarity. Adapters whose secondary voltage can be selected by turning a miniature switch through a screwdriver or a slider are very suitable for daily use.
So an adapter can supply power to a lot of devices. In order to become multi-purpose, an adapter is equipped with a series of terminals that can be replaced. Another trick used by manufacturers of electronics to make their power supplies multi-purpose, regardless in which country they will be used, is to expand enormously the allowed primary voltage to which the power supply of a laptop can be connected, for example. We know that in the US, England, Japan, Canada and other countries, the electric-network voltage isn’t 220VAC, but around 110VAC, depending on the country, as discussed in detail in the article “Convectors”.
In order to avoid the use of convectors, the voltage of the power supply of laptops is made so that they can be plugged in the entire range from 110 to 240VAC. Many of these adapters have different plug caps. This avoids the use of transitional adapters for switching from one standard to another (from European to American or English or vice versa).