Portable USB Charger ASIC
This ASIC is a Power Management Unit (PMU) designed for Portable USB Charger application. It has six major functional blocks: USB Passer, Battery Charger, Output Converter, Torch LED Driver, Status Display LED Driver and Thermal Control.
An Example Chip :
Invention : New Current Estimation Scheme
In most of Portable USB Charger application, a current sensing resistor is needed to determine the amount of charging current by measuring the voltage drop across this resistor connected in series with the charging current path. However, such a current sensing scheme is dissipative and not power efficient.
In view of large battery charging current (> 2A) and the accuracy limitation of this current sensing scheme, the battery charging will usually be stopped with charging current at around 80mA.
Hence, Portable USB Charger with this current sensing scheme is usually unable to charge low energy device, like bluetooth headset, earphone, smart watch, etc.
We have invented a new current estimation scheme by which the current sensing resistor is eliminated.