Overvoltage protection circuit with thermal fuse, zener diode, and posistor
First Claim
1. An electronic device protection circuit for inhibiting a voltage exceeding a rated voltage of an electronic device from being applied to the electronic device, comprising:
- a current-increasing device that increases a current when the voltage applied to the current-increasing device is greater than the rated voltage;
a current-inhibiting device that inhibits the current by increasing an electrical resistance in response to one of an increase in current and a rise in temperature, wherein the current-inhibiting device and the current-increasing device are connected in series and are connected in parallel with a battery on the protection circuit, and wherein the current-increasing device and the current-inhibiting device are arranged to conduct heat to each other, and applying an overvoltage greater than the rated voltage causes a current resulting from the overvoltage to flow through the current-increasing device, so that the current-increasing device generates heat, and the current resulting from the overvoltage is bypassed from the current-increasing device and the current-inhibiting device to reduce the current flow through the electronic device.
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Accused Products
Abstract
An electronic device protection circuit inhibits a voltage exceeding the rated voltage of the electronic device, which may include a secondary battery, from being applied and includes a positive temperature characteristic device and a diode that are connected in series and arranged in proximity to each other. The thermal fuse, the posistor, and the zener diode are arranged to conduct heat to each other, so that applying an overvoltage greater than the rated voltage to input terminals of the electronic device causes the current resulting from the overvoltage to flow through the zener diode that causes it to generate heat that accelerates the fusion of the thermal fuse.
78 Citations
35 Claims
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1. An electronic device protection circuit for inhibiting a voltage exceeding a rated voltage of an electronic device from being applied to the electronic device, comprising:
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a current-increasing device that increases a current when the voltage applied to the current-increasing device is greater than the rated voltage;
a current-inhibiting device that inhibits the current by increasing an electrical resistance in response to one of an increase in current and a rise in temperature, wherein the current-inhibiting device and the current-increasing device are connected in series and are connected in parallel with a battery on the protection circuit, and wherein the current-increasing device and the current-inhibiting device are arranged to conduct heat to each other, and applying an overvoltage greater than the rated voltage causes a current resulting from the overvoltage to flow through the current-increasing device, so that the current-increasing device generates heat, and the current resulting from the overvoltage is bypassed from the current-increasing device and the current-inhibiting device to reduce the current flow through the electronic device.
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2. An electronic device protection circuit for inhibiting a voltage greater than a rated voltage of an electronic device from being applied to positive and negative voltage input terminals of the electronic device, comprising:
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a posistor that increases an electrical resistance in response to an increase in current, an end of the posistor being connected to one of the voltage input terminals of the electronic device;
a thermal fuse having characteristics that a flow of current therethrough caused by applying a voltage exceeding a rated voltage causes a rise in temperature resulting in a fusion of the thermal fuse, an end of the thermal fuse being connected to an other voltage input terminal of the electronic device;
a zener diode having characteristics that applying a voltage exceeding a breakdown voltage thereof that is set to greater than the rated voltage of said thermal fuse results in an increase in the current, the zener diode being connected to an other end of the posistor and to an other end of the thermal fuse, wherein the thermal fuse and the zener diode conduct heat to each other;
applying an overvoltage greater than the rated voltage to the voltage input terminals of the electronic device causes the current resulting from the overvoltage to flow through the zener diode such that the zener diode generates heat that accelerates the fusion of the thermal fuse;
the current resulting from the overvoltage is bypassed to the zener diode and the posistor to reduce the current through the electronic device; and
when the electrical resistance of the posistor increases the increased electrical resistance reduces the current through the zener diode and the posistor to one of equal to and less than rated currents of the zener diode and the posistor.- View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. An electronic device protection circuit for inhibiting a voltage greater than a rated voltage of an electronic device from being applied to positive and negative voltage input terminals of the electronic device, comprising:
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a zener diode having characteristics that applying a voltage exceeding a breakdown voltage thereof that is set to greater than a rated voltage results in an increase in a current, an end of the zener diode being connected to one of the positive and negative voltage input terminals of the electronic device;
a thermal fuse having characteristics that a flow of current therethrough caused by applying a voltage exceeding a rated voltage causes a rise in temperature resulting in a fusion thereof, an end of the thermal fuse being connected to an other voltage input terminal of the electronic device;
a posistor having characteristics of increasing an electrical resistance thereof in response to an increase in current, having a Curie point set higher than the thermal fuse fusion temperature and being connected to an other end of the zener diode and an other end of the thermal fuse, wherein the thermal fuse, the posistor, and the zener diode conduct heat to each other;
applying an overvoltage greater than the rated voltage to the voltage input terminals of the electronic device causes the current resulting from the overvoltage to flow such that the zener diode and the posistor generate heat, thereby accelerating the fusion of the thermal fuse;
the current resulting from the overvoltage is bypassed to the zener diode and the posistor to reduce the current through the electronic device; and
when the electrical resistance of the posistor increases the increased electrical resistance reduces the current through the zener diode and the posistor to one of equal to and less than the rated currents of the zener diode and the posistor.- View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. An electronic device protection circuit for inhibiting a voltage exceeding a rated voltage of an electronic device from being applied to the electronic device, comprising:
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a zener diode having characteristics that applying a voltage greater than a breakdown voltage thereof that is set to greater than a rated voltage results in an increase in current and is connected in parallel to the electronic device; and
a posistor connected in series with the zener diode and having characteristics of inhibiting a current by an increase in an electrical resistance thereof in response to one of an increase in current and a rise in temperature, and wherein the electrical resistance of the posistor increases in response to the rise in temperature;
the zener diode increases the current when the voltage greater than the breakdown voltage is applied, causing the zener diode to generate heat;
the zener diode and the posistor conduct heat to each other; and
when an overvoltage greater than the rated voltage is applied to the electronic device the zener diode generates heat that accelerates an increase in the electrical resistance of the posistor.- View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34, 35)
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Specification