How do smartphone companies do high wattage charging on a small device?
There were times when people used to keep their phones for charging overnight as it used to take hours to be fully charged. With time and technology, the time for charging phones came down, and now many brands are launching phones that can be fully charged in 10 minutes with a powerful 150 Watt charger. But have you ever wondered which technology these smartphone companies use to do such high wattage fast charging on smartphones?
How does fast charging, like full charge in 10 minutes, work?
Currently, fast-charging smartphones range between 18W to 65W worth of power, with charge times from 30 minutes to just an hour. However, some brands like Oppo, realme, and others have announced 150W fast-charging within a few minutes.
Before we dive into the technicals, let's start with the fundamentals.
Every phone has a battery, and the battery delivers power in the same way, either more or less. Like all electronic devices, batteries operate with a specific voltage and can input and output a certain amount of current. More of both means more power and so fast charging. However, batteries have some operating limits regarding voltage, and it must be followed to charge them safely.
The typical charging rate or power value for smartphones is 10W; anything greater than this can be referred "fast Charging." Any smartphone can support fast charging when receiving power from a charging brick at a rate higher than the minimum rate supported by USB standards.
How does fast charging work?
Batteries charge when a current pass through them. Greater current and higher voltages charge them faster, but there is a limit to what batteries can take. The charge controller (IC) controls against dangerous spikes in current.
Because Li-ion batteries may get harmed due to elevated voltage, makers typically bank on high current transfer rates to fast-charge a phone's battery. Fast charging strives to maximize the constant current flow stage's utility to transfer maximum charge to the battery before the voltage reaches its extreme value.
Dedicated circuits inside a smartphone restrict the voltage and current flow. Standard voltage regulators control the voltage without changing the current flow, so older smartphones often heat up while charging. These circuits assure the battery's temperature is maintained below the permissible level and the battery's health is maintained.
Despite the limitations of Li-ion batteries due to voltage, chargers with high power output support employ a high voltage and low current combination. The circuits inside phones step the current up and the voltage down.
Smartphones that feature high voltage charging feature instruments called Buck Converters to convert a high voltage to a low voltage while increasing the current.
It enables smartphone makers to use high current values of up to 20V or even higher to charge a Li-ion battery with a typical voltage of 4.2V. As opposed to a standard regulator, a Buck Converter can efficiently transform the high voltage into a high current without losing much heat energy.
Even in fast charging, the battery charges quickly during constant current and saturation stages and eventually slows down during the topping phase. Smartphone makers often claim to charge 60% of the battery under 20 minutes because the fastest charging occurs in this zone.
Wireless fast charging -
Wireless charging has principles and hurdles, same as wired fast-charging. Smartphones need a fast-chargeable battery and a method for communicating information from the gadget to the charger. Besides, there is the added complication of efficiently transferring a large amount of power over the air.
There is a growing market for much faster proprietary wireless charging standards. To name a few, Oppo boasts 65W wireless SuperVooc, OnePlus has 50W Warp Charge, and Huawei has its 40W technology.
The key to faster wireless charging is using more coils to transfer the current over the air. However, this has the side impact of costing more to implement, taking up more space, and rising charging temperature.
