BATTERY CHARGING AND DISCHARGING BY USING A BI-DIRECTIONAL TRANSISTOR
First Claim
1. 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.
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Accused Products
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.
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Citations
23 Claims
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1. A battery charger comprising:
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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. - View Dependent Claims (2, 3)
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4. A battery charger comprising:
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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. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11)
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12. A battery controller comprising:
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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. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A Universal Serial Bus battery charger comprising:
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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.
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Specification