Circuit for switching power supplies of external power source and lithium battery

Abstract

Disclosed is a circuit for switching power supplies of an external power source and a lithium battery. The circuit comprises the external DC power source, the lithium battery, and switch paths respectively corresponding to the external DC power source and the lithium battery. In a first switch path, the external DC power source is connected with the lithium battery through a charging management chip, a first switch tube is arranged to be connected between the lithium battery and a system power supply, and the external DC power source is connected with the control pole of the first switch tube; and in a second switch path, the external DC power source is connected with the system power supply through a second switch tube and a third switch tube which are in pipe connection, at the same time, the external DC power source is connected with a fourth switch tube through a boost charge pump, the external DC power source is connected with the control pole of the fourth switch tube, and the output end of the fourth switch tube is respectively connected with the control pole of the second switch tube and the control pole of the third switch tube. According to the invention, in case that the external power source is pulled out or abnormally fails, the backup lithium battery can rapidly supply power to a system, such that the system stability and the power supply reliability can be ensured.

Description

[0001] technical field [0002] The invention relates to the technical field of system power supply, in particular to a switching circuit that can be widely applied to an external power supply and a lithium battery in portable devices such as tablet computers and notebook computers with backup batteries. Background technique [0003] At present, portable electronic products have spare lithium batteries. When the external power supply is normal, the external power supply should be used for power supply; Automatically switch to external power supply, during the switching process, the system cannot be abnormal or restarted. Some lithium battery charging management chips integrate power switching control functions inside, but most low-end lithium battery charging management chips still need to design an external switching circuit. There are also some chips specially used to meet switching functions, but due to their high price, they are not suitable for most products that have ...

AI Technical Summary

Problems solved by technology

Some lithium battery charging management chips integrate power switching control functions inside, but most low-end lithium battery charging management chips still need to design an external switching circuit

There are also some chips specially designed to meet switching functions, but due to their high price, they are not suitable for most products that require cost

Some designers often use two Schottky diodes in parallel to realize the switching function, but because the Schottky itself has a voltage drop, and when the supply current reaches the ampere level, there will be a certain loss, so this method has certain limitations

Images