USB CHARGER USING SENSOR-LESS CURRENT LIMIT

摘要

A universal serial bus charger comprises a universal serial bus connector for providing a connection to a voltage source. An output voltage connector provides a charging voltage to a connected battery. A switching voltage regulator generates the charging voltage responsive to the voltage source. Control circuitry monitors an actual charging current applied to the connected battery and provides a programmed current signal enabling the actual charging current to operate at a programmed level if the actual charging current does not exceed a programmed charging current level. The control circuitry provides a charging current limit signal enabling the actual charging current to operate at a predetermined charge current limit if the actual charging current exceeds the programmed charging current level. PWM control circuitry generates switching control signals to control operation of the switching voltage regulator responsive to the control circuitry.

主权项

1. A method for charging a battery through a universal serial bus (USB) connection having a USB voltage and a maximum USB current value, comprising:
coupling the USB connection to a switching voltage regulator; the switching voltage regulator generating a battery charge current; generating a reference signal for the battery charge current; generating a limit signal for the battery charge current based on at least the USB voltage, the maximum USB current value, and a battery voltage; generating a control signal corresponding to a lower of the reference signal for the battery charge current and the limit signal for the battery charge current; and a control circuit controlling the switching voltage regulator and the battery charge current responsive to the control signal.