Reverse charger protection
AssigneeNational Semiconductor Corporation
InventorGregory J. Smith
Life of this patent
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Abstract
A method and apparatus is provided for protecting voltage regulation circuits and battery cells (“cell”) when a cell is reverse-coupled to a charger. When a charger is reverse-coupled to the cell, parasitic devices in voltage regulation circuits become forward-biased. When the parasitic devices become forward-biased, the parasitic devices may carry a current that is sufficiently large to damage the voltage regulation circuits. A shunt regulator is used to detect the presence of a reverse-coupled charger (“reverse charger”) and to shunt current to a ground potential such that potentially damaging currents are prevented from flowing through the parasitic devices.
Claims22
An apparatus for protecting a battery charger against a reverse-coupled cell, comprising:
- a charge input circuit arranged to provide a charging signal;
- a body diode that is located within an over-voltage protection circuit;
- and
- a reverse-voltage protection circuit that is arranged to detect the reverse-coupled cell and to prevent the charging signal from causing the body diode in the over-voltage protection circuit to conduct.
A method for protecting a charge input circuit from a high current flow that results when a reverse-voltage is applied to the charge input circuit, wherein the reverse-voltage results when a charger is reverse-coupled to a cell, comprising:
- comparing a voltage associated with the charging signal to a maximum-allowable reverse-voltage;
- and
- reducing the reverse-voltage of the charging signal when the maximum-allowable reverse-voltage is exceeded.
An apparatus for protecting a charge input circuit from a high current flow that results when a reverse-voltage is applied to the charge input circuit, wherein the reverse-voltage results when a charger is reverse-coupled to a cell, comprising:
- means for comparing a voltage associated with the charging signal to a maximum-allowable reverse-voltage;
- and
- means for reducing the reverse-voltage of the charging signal when the maximum-allowable reverse-voltage is exceeded.
Dependencies are inferred from the claim text.