Battery charging circuit with undervoltage current control
AssigneeMotorola, Inc.
InventorsJohn E. Herrmann, Ashok R. Patil
Life of this patent
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Abstract
This invention includes a charging circuit employing an off-the-shelf battery protection circuit. The invention offers an improvement to the battery protection circuit by providing means to accommodate trickle charging during undervoltage conditions. A pass transistor is provided with a trickle resistor coupled in parallel. The pass transistor is driven by a drooping voltage circuit that causes the pass transistor to open in undervoltage conditions, thus forcing charging current through the trickle resistor. Indicating means are also included to tell the user whether the circuit is in trickle mode or normal charging mode.
Claims5
In a battery protection circuit having at least one rechargeable cell, a voltage sensing means, a charge control transistor and a discharge control transistor, the improvement comprising:
- a. a pass transistor coupled serially with the at least one rechargeable cell;
- b. a trickle resistor coupled in parallel with the pass transistor;
- and
- c. a drooping voltage circuit coupled to the protection circuit;
- wherein when the discharge transistor opens, the drooping voltage circuit causes the pass transistor to open, thereby causing any charging current to flow through the trickle resistor.
Dependencies are inferred from the claim text.