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Battery pack protection circuit and battery pack including a protection circuit
| Details |
Inventors: Peterzell, Paul E.;
Assignee: Qualcomm Inc. (San Diego, CA)
Primary Examiner: Tso; Edward H.
Assistant Examiner:
Attorney, Agent or Firm: Wadsworth; Phillip, Brown; Charles D.
A battery protection circuit for an external battery pack has a switch for controlling connection of a battery output to a load and a detector for detecting a resistance at a load output terminal. A first comparator compares the detected resistance to a predetermined maximum value, and a second comparator compares the detected resistance to a predetermined minimum value. If the detected resistance is in the range between the minimum and maximum values, a control signal is produced to enable connection of the battery output to the load. If the detected resistance is outside the range, the switch is disabled and no current can flow to the load. |
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DETAILED DESCRIPTION It is an object of the present invention to provide a new and improved protection circuit for an external battery pack, particularly a portable phone battery pack.
According to the present invention, a battery protection circuit is provided, which comprises a switch assembly having an input for receiving a control signal, the switch assembly controlling connection of a battery output to a load, a detector for detecting a resistance at a load terminal, and a control assembly for determining whether the resistance has a value between a predetermined maximum value and a predetermined minimum value, and for generating the control signal in response to the determination, the control signal causing the switch to close if the determination is positive, and causing the switch to open otherwise, so that the battery output is connected to the load only when the detected resistance has a value between the predetermined minimum and maximum values.
Preferably, the control assembly comprises a first comparator for comparing the resistance to the predetermined maximum value and producing a first output signal if the resistance is above the predetermined maximum value and a second output signal if the resistance is below the predetermined maximum value, a second comparator for comparing the resistance to the predetermined minimum value and for producing a third output signal if the resistance is below the predetermined minimum value and a fourth output signal if the resistance is above the predetermined minimum value, and a second detector connected to the outputs of the first and second comparators for producing the control signal to close the switch if the resistance is between the minimum and maximum values.
Preferably, the load to be powered by the battery has positive and negative input contacts for connection to battery positive and negative outputs, respectively, and an ID output to which a predetermined load identifying resistance is applied.
When the battery is connected through the battery protection circuit to the proper load, the ID output is connected to the first and second comparators which compare its resistance to the predetermined minimum and maximum values, and only permit power to be supplied from the battery to the load when the detected resistance is between the minimum and maximum values
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