When you design a project that works with a battery you have two alternatives to choose:

  • non rechargeable battery
  • rechargeable battery

In this article we want to talk about projects that use rechargeable batteries, in details , lithium rechargeable batteries.

When you choose this type of battery and you want to recharge it, you obviously must choose a charger designed for lithium battery but after this choice you have another to do:

Linear battery charger or switching battery charger?

LINEAR BATTERY CHARGER

The main advantages of a linear battery charger are:

  • Cheap solution: in terms of number and type of components and consequently in terms of total price
  • Low circuit complexity
  • minimal space on board

The main disadvantages or better, the limitations of this type of charger are:

  • Low charging current, typically some hundreds of mA
  • During the project phase you must pay more attention to the power dissipated by the charger

You can find this type of charger on small electronics devices that consume very low current for example wrist bands, or different type of sensors so in systems that mount small battery or anyway in systems that need low current charge for the battery.

Here a photo that represents a linear battery charger, look at it simplicity

 

SWITCHING BATTERY CHARGER

The main advantages of a linear battery charger are:

  • Very high charging current
  • The IC that control charging is often full of different options to control it, via serial comunication or simply adding some components.

The main disadvantages are:

  • expansive solution : the IC itself cost more than an linear charger IC and needs more components to works that increase final price
  • more space taken on the final board
  • Higher complexity of the circuit

You can find this type of charger into for example smartphones, and they can handle typical current like 1 A or 2 A, but there are some switching charger that can charge battery also at higher current.

Here a photo that represents a switching battery charger

This circuit is based on BQ24250 , an IC that can handle up to 2A and that can be controlled with an I2C serial comunication.

Via I2C you can set, for example, the charging current at the value that you need or read different registers that give you informations about fault conditions, state of charging and so on.

In the next articles we talk about these 2 circuits, starting with the linear charger based on AAT3681A and then talking about the switching charger based on BQ24250,so we will learn how to cover a wide range of applications that use rechargeable lithium battery.

keep following!!