Circuit and method for balancing battery cells
Embodiments of the invention provided circuits and methods for balancing battery cells. According to a first embodiment, a cell balancing circuit includes an auxiliary current path for controlling a conductance status of a shunt path. According to a second embodiment, a cell balancing circuit utilizes a total voltage of multiple neighboring cells in a battery pack to generate a current. Based on the current, a voltage drop is generated to conduct a shunt path corresponding to one cell of the neighboring cells. According to a third embodiment, a cell balancing circuit utilizes a total voltage of multiple neighboring cells in a battery pack to generate a current. Based on the current, a voltage drop is generated to conduct a shunt path corresponding to one cell of the neighboring cells. The cell balancing circuit can turn on multiple internal switches at the same time to balance multiple neighboring cells simultaneously.
1. A cell balancing circuit comprising:
a shunt path coupled to a cell for enabling a bypass current of said cell;
an auxiliary current path coupled in parallel with said shunt path;
a third current path coupled in parallel with said auxiliary current path; and
a controller operable for conducting said third current path to enable a current flowing through said third current path if said cell is unbalanced,
wherein said auxiliary current path is conducted to enable a current flowing through said auxiliary current path in response to said current flowing through said third current path,
wherein said shunt path is conducted to enable said bypass current in response to said current flowing through said auxiliary current path.
2. The cell balancing circuit of claim 1 , further comprising:
a resistor coupled between said auxiliary current path and said third current path,
wherein a current flows through said resistor to generate a voltage drop on said resistor if said third current path is conducted, and
wherein a conductance status of said auxiliary current path is determined by said voltage drop on said resistor.
3. The cell balancing circuit of claim 1 , wherein said auxiliary current path comprises a first switch and a first resistor, wherein a current flows through said first resistor to generate a voltage drop on said first resistor if said third current path is conducted, wherein a conductance status of said shunt path is determined by said voltage drop on said first resistor.
4. The cell balancing circuit of claim 3 , wherein said shunt path comprises a second resistor and a second switch, wherein a conductance status of said second switch is determined by said voltage drop on said first resistor.
5. The cell balancing circuit of claim 1 , wherein said third current path is inside said controller, and wherein said shunt path and said auxiliary current path is outside said controller.
6. A method for balancing a cell, said method comprising:
conducting a first current path to enable a first current flowing through said first current path if said cell is unbalanced;
conducting a second current path in parallel with said first current path in response to said first current to enable a second current flowing through said second current path; and
conducting a shunt path in parallel with said second current path to enable a bypass current flowing from a first terminal of said cell through said shut path to a second terminal of said cell in response to said second current.
7. The method of claim 6 , further comprising:
generating a first voltage drop across a first resistor based on said first current; and
conducting said second current path in response to said first voltage drop.
8. The method of claim 6 , further comprising:
generating a second voltage drop across a second resistor based on said second current; and
conducting said shunt path in response to said second voltage drop.
9. A cell balancing circuit comprising:
a current path coupled in parallel with a plurality of neighboring cells comprising a first cell and a second cell;
a shunt path coupled in parallel with said first cell;
a controller operable for conducting said current path to generate a current flowing through said current path according to a total voltage of said plurality of neighboring cells if said first cell is unbalanced; and
a resistive element coupled between said current path and said first cell,
wherein said current flows through said resistive element to produce a voltage drop on said resistive element, and wherein a conductance status of said shunt path is determined by said voltage drop.
10. The cell balancing circuit of claim 9 , wherein said current path comprises a first switch coupled in parallel with said first cell and a second switch coupled in parallel with said second cell, wherein said controller is operable for turning on said first switch and said second switch simultaneously to generate said current.
11. The cell balancing circuit of claim 9 , wherein said current path comprises a switch coupled in parallel with said plurality of neighboring cells, wherein said controller is operable for turning on said switch to generate said current.