Battery charger circuit and control schemes

摘要

Described is a battery charger circuit for charging a battery. The battery charger circuit comprises a control element having a first input configured to receive an input from a reference source, a second input configured to receive an input from the battery and an output, said control element having an output current response characteristic which varies with respect to the battery input such that said control element implements a saturating function that causes the charging current of the battery to automatically transition between a constant current operating mode and a constant voltage operating mode or a constant voltage operating mode to a constant current operating mode.

主权项

1. A battery charger circuit having first and second terminals coupled to respective terminals of a battery, the battery charger circuit comprising:
a control element having at least first and second inputs with a first one of the inputs coupled to a corresponding terminal of the battery charger circuit, said control element comprising a low-power detector circuit coupled to the first one of the inputs of said control element, said low-power detector circuit configured to sense and detect changes in a battery voltage signal, said control element configured to receive a reference voltage signal corresponding to a predetermined voltage target level of the sensed battery voltage signal at a second one of the inputs and generate a control element current signal at an output thereof in response to the sensed battery voltage signal and the reference voltage signal, said control element having an output current response characteristic which varies with respect to the sensed battery voltage signal such that said control element implements a saturating function that causes charging current provided to the first and second terminals of the battery charger circuit to automatically transition between one of: a constant current operating mode and a constant voltage operating mode; or a constant voltage operating mode to a constant current operating mode; and an end-of-charge detection circuit having at least first and second inputs with a first one of the inputs adapted to couple to the control element output, said end-of-charge detection circuit configured to receive the control element current signal at the first one of the inputs and a reference current signal at a second one of the inputs and in response thereto said end-of-charge detection circuit compares the control element current signal with the reference current signal to detect end-of-charge at the first and second terminals of the battery charger circuit, wherein said control element is implemented as an operational transconductance amplifier (OTA) and the output current response characteristic of said control element has a shape corresponding to the shape of a hyperbolic tangent function, the output response characteristic of said control element utilized to transition the charging current between the constant current operating mode and the constant voltage operating mode.