Patent ID: 9166429
Filing Date: 2015-10-20
Classification: H02J

Abstract:
1. A universal serial bus charger, comprising: a universal serial bus connector for providing a connection to a voltage source; an output voltage connector for providing a charging voltage to a connected battery; a switching voltage regulator for generating the charging voltage responsive to the voltage source and PWM switching control signals, wherein the switching voltage regulator includes a plurality of switching transistors, and at least one switching transistor of the plurality of switching transistors is connected directly to the universal serial bus connection; analog control circuitry for monitoring an actual charging current applied to the connected battery and generating a reference charge level signal at a non-zero level, the analog control circuitry determining a difference between the actual charging current and the reference charge level signal, the analog control circuitry including a comparator for comparing the actual charging current with a charging current limit level and determining if the actual charging current exceeds the charging current limit level, and responsive to the determining, the analog control circuitry generating the reference charge level signal at a first value if the actual charging current does not exceed the charging current limit level and generating the reference charge level signal at a second value if the actual charging current exceeds the charging current limit level, the second value associated with the charging current limit level, wherein the analog control circuitry includes an analog divider circuit for receiving an input voltage from the voltage source, a battery voltage of the connected battery, and a current limit value associated with the voltage source, and generating the charging current limit level as an analog signal based on the input voltage from the voltage source, the battery voltage of the connected battery, the current limit value associated with the voltage source, and a predetermined efficiency value associated with a power conversion of the switching voltage regulator; and a PWM control circuit for generating the PWM switching control signals to control operation of the switching voltage regulator responsive to the difference between the actual charging current and the reference charge level signal at the first value when the charging current does not exceed the charging current limit level and responsive to the difference between the actual charging current and the reference charge level signal at the second value when the charging current exceeds the charging current limit level.