Battery charging and discharging by using a bi-directional transistor
AssigneeMicrosemi Corporation
InventorBruce R. Ferguson
Life of this patent
Estimating the term…
Abstract
A battery charger for an electronic device receives current limited power from an external power source, such as a Universal Serial Bus power interface. The battery charger can linearly regulate a charging current to an internal battery and limit the charging current so as not to demand current in excess of what the external power source can provide. A bi-directional pass element coupled between a system power terminal and the internal battery controls the charging current and effectively isolates the internal battery from a system load during charging of the battery while providing a low impedance path from the internal battery to the system load during discharging of the battery.
Claims23
A battery charger comprising:
- a first input configured to accept DC power from an AC adapter;
- a second input configured to accept DC power from a Universal Serial Bus power interface;
- a first output configured to provide power to a system load;
- a second output configured for connection to a battery;
- a first isolation circuit coupled between the first input and the first output to prevent current flow in a reverse direction to the first input;
- a second isolation circuit and a current sensing circuit coupled in series between the second input and the first output, wherein the second isolation circuit prevents current flow in a reverse direction to the second input, and the current sensing circuit measures the current flow from the Universal Serial Bus power interface;
- a bi-directional pass element coupled between the first output and the second output, wherein the bi-directional pass element conducts a charging current in a first direction to the second output during charging of the battery and conducts a discharging current to a second direction from the second output during discharging of the battery;
- and
- a charging controller configured to linearly regulate the charging current of the bi-directional pass element based on the current flow from the Universal Serial Bus power interface.
A battery charger comprising:
- a dual input source selector with a first input coupled to a primary power source and a second input coupled to a secondary power source, wherein the dual input source selector selectively couples the primary power source or the secondary power source to a system power terminal of an electronic device;
- a current sensor coupled between the secondary power source and the system power terminal to measure a supply current from the secondary power source;
- and
- a battery controller coupled between the system power terminal and a battery of the electronic device, wherein a bi-directional device in the battery controller conducts a charging current in a first direction from the system power terminal to the battery during charging of the battery and conducts a discharging current in a second direction from the battery to the system power terminal during discharging of the battery.
A battery controller comprising:
- a bi-directional pass element coupled between a system power terminal and a battery terminal;
- a battery control loop that senses a voltage difference between the system power terminal and the battery terminal, wherein the battery control loop outputs a feedback control signal based on the voltage difference;
- and
- a pass element driver that accepts the feedback control signal, wherein the pass element driver configures the bi-directional pass element to conduct a charging current in a first direction when the voltage of the system power terminal is greater than the voltage of the battery terminal or to conduct a discharging current an opposite direction when the voltage of the system power terminal is less than the voltage of the battery terminal.
A Universal Serial Bus battery charger comprising:
- means for selectively coupling a Universal Serial Bus power interface to a system power terminal of a portable device;
- means for charging and discharging a battery through a bi-directional element that couples the battery to the system power terminal;
- means for sensing an input current at the Universal Serial Bus power interface;
- and
- means for linearly controlling the current conducted by the bi-directional element to ensure that the input current is less than a predetermined limit.
Dependencies are inferred from the claim text.