Battery charging safety circuit for simultaneous startup and rapid surge current clamping
First Claim
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1. A safety circuit for protecting a battery against an over-voltage condition associated with a voltage at an output terminal of a charging circuit, comprising:
- a coupling circuit wherein the coupling circuit is coupled between the output terminal of the charging circuit and an input terminal of the battery, and wherein the coupling circuit is configured to produce an IR drop in response to the over-voltage condition such that the voltage at the output terminal of the charging circuit is increased;
a control transistor wherein a source of the control transistor is coupled to the output terminal of the charging circuit, wherein the control transistor has an associated gate-to-source voltage (VGS), and wherein the control transistor is configured to provide a first activation signal when the increased voltage at the output terminal of the charging circuit increases the magnitude of the control transistor VGS beyond a conduction threshold of the control transistor; and
a regulator wherein the regulator is coupled to the output terminal of the charging circuit, wherein the regulator is activated in response to the first activation signal such that the voltage at the output terminal of the charging circuit is lowered.
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Abstract
A safety circuit monitors a charging signal supplied by a charging circuit for charging a battery. Damage to the battery may occur when the voltage at the input terminal of the battery rises above the safe level for the battery. A voltage drop across a coupling circuit is used to generate an activation signal. The activation signal causes a power amplifier to lower the voltage of the charging signal before the charging signal can drive the inductances associated with the battery input terminal and leads to the point where damage to the battery may occur.
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Citations
20 Claims
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1. A safety circuit for protecting a battery against an over-voltage condition associated with a voltage at an output terminal of a charging circuit, comprising:
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a coupling circuit wherein the coupling circuit is coupled between the output terminal of the charging circuit and an input terminal of the battery, and wherein the coupling circuit is configured to produce an IR drop in response to the over-voltage condition such that the voltage at the output terminal of the charging circuit is increased; a control transistor wherein a source of the control transistor is coupled to the output terminal of the charging circuit, wherein the control transistor has an associated gate-to-source voltage (VGS), and wherein the control transistor is configured to provide a first activation signal when the increased voltage at the output terminal of the charging circuit increases the magnitude of the control transistor VGS beyond a conduction threshold of the control transistor; and a regulator wherein the regulator is coupled to the output terminal of the charging circuit, wherein the regulator is activated in response to the first activation signal such that the voltage at the output terminal of the charging circuit is lowered. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for protecting a battery against an over-voltage condition of a charging signal supplied by a charging circuit, comprising:
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increasing the voltage of the charging signal across an IR drop provided by a coupling circuit; applying the increased voltage to a source of a control transistor such that the magnitude of the control transistor VGS is increased; providing a first activation signal in response to the magnitude of the control transistor VGS increasing beyond a conduction threshold of the control transistor; and reducing the voltage of the charging signal in response to the first activation signal. - View Dependent Claims (11, 12, 13, 14, 15)
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16. An apparatus for protecting a battery against an over-voltage condition of a charging signal supplied by a charging circuit, comprising:
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means for increasing the voltage of the charging signal across an IR drop provided by a coupling circuit; means for applying the increased voltage to a source of a control transistor such that the magnitude of the control transistor VGS is increased; means for providing a first activation signal in response to the magnitude of the control transistor VGS increasing beyond a conduction threshold of the control transistor; and means for reducing the voltage of the charging signal in response to the first activation signal. - View Dependent Claims (17, 18, 19, 20)
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Specification