In rechargeable mobile devices, the charging IC is an essential component. With the increasing popularity of portable devices such as smartphones, tablets, and cameras, people are demanding power and the ability to use these devices while charging. requirements are increasing day by day. Higher power requirements have increased the need for batteries with high power density and excellent charging capabilities.

The charging IC is based on the difference in the connection between the battery and the system load. The system load can be powered by the input power supply, by the battery, or by both. Then the battery IC must have the power management function to realize the selection of the system load power source.

NVDC dynamic path management is one of the power management strategies commonly used in mobile devices. The system load is directly connected to the system bus VSYS. The system load can be directly powered by the battery through the Battery FET, or the input power can be powered by the front-end DC/DC .

When the input power is not connected, the Battery FET is fully turned on, and the battery directly supplies power to the system load. When there is input power, the voltage of the system bus is regulated by DC/DC, while the system bus charges the battery through the Battery FET. But the system load has a higher priority for power consumption. The charging IC will preferentially supply power to the system according to the capability of the input power supply and the demand of the system load, and the remaining power is used to charge the battery.

During the charging process, when the total system load demand exceeds the capacity of the input power supply, the system bus voltage will drop, and the charging IC will reduce the charging current to ensure that the total load power will not continue to increase, thereby stabilizing the system voltage and will not drop. , to maintain the smooth operation of the system load.

If the input power supply still cannot meet the system load demand after the charging current is reduced to zero, the system bus voltage will continue to drop until it is lower than the battery voltage. At this time, the battery will supply power to the system through the Battery FET, which is called the battery supplementary power supply mode. At this time, the input power supply and the battery provide power to the system at the same time.

When there is input power and the battery is over-discharged, the charging IC will regulate the system bus voltage to a minimum supply voltage value that the system load can accept. When the system voltage is below a certain threshold, the charging current will decrease. When the battery is reversely discharged, the charging IC controls the Battery FET to work in the saturation region according to the battery voltage to avoid a large inrush current flowing into the over-discharged battery. This smooth entry and exit of the battery supplementary power supply mode is usually called Battery Ideal diode mode of FET.

In ideal diode mode, the Battery FET behaves like a diode as it operates in the saturation region while the battery is discharging. When there is input power and the system voltage is lower than a certain value of the battery voltage, the charging IC regulates the gate of the Battery FET to control the voltage difference between the battery and the system voltage to a certain value. When the battery discharge current continues to increase, the gate voltage of the Battery FET increases to reduce the impedance of the Battery FET, thereby ensuring that the voltage difference between the battery and the system remains at the design value until fully turned on. Conversely, if the discharge current decreases, the gate voltage of the Battery FET decreases to increase the impedance of the Battery FET, thereby regulating the voltage difference between the battery and the system to maintain the design value.

Dynamic power path management employs an additional set of detection modules that measure system voltage or input current, monitor total power demand in real-time, share AC adapter current between system and battery charging, and automatically reduce charging current as system load increases. Adjust the distribution relationship between the charging current and the system current to ensure the normal operation of the system to the greatest extent. Once the power demand exceeds the preset value, reduce the charging current through the charger to ensure that the output power of the adapter is constant and not overloaded.