Apparatus and methods for coupling a case of an electric appliance to an external ground and for detecting leakage current
First Claim
1. An apparatus for coupling a case of an electric appliance to an external ground, which comprises:
- neutral ground generating means for combining signals on first and second AC power lines to produce a neutral ground point;
first detection means for detecting a current flow from the first AC power line to the case of the appliance to generate a first current detection signal;
second detection means for detecting a current flow from the second AC power line to the case of the appliance to generate a second current detection signal; and
ground coupling means for connecting, in response to the first current detection signal, the first AC power line as the external ground to the case of the appliance;
for connecting, in response to the second current detection signal, the second AC power line as the external ground to the case of the appliance; and
for connecting the neutral ground point as the external ground to the case of the appliance when the first and the second current detection signals are absent.
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Accused Products
Abstract
The apparatus for automatically coupling an internal ground of an electric appliance to an external ground, comprises first and second AC power lines for supplying an AC input to a load; a neutral ground generating circuit for combining the first and the second AC power lines to produce a neutral ground point; a first detection circuit for detecting a current flow from the first AC power line to the internal ground to generate a first current detection signal; a second detection circuit for detecting a current flow from the second AC power line to the internal ground to generate a second current detection signal; and a ground coupling circuit for connecting, in response to the second current detection signal, the first AC power line as the external ground to the internal ground; for connecting in response to the first current detection signal, the second AC power line as the external ground to the internal ground; and for connecting the neutral ground point as the external ground to the internal ground when the first and the second current detection signals are absent.
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Citations
14 Claims
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1. An apparatus for coupling a case of an electric appliance to an external ground, which comprises:
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neutral ground generating means for combining signals on first and second AC power lines to produce a neutral ground point; first detection means for detecting a current flow from the first AC power line to the case of the appliance to generate a first current detection signal; second detection means for detecting a current flow from the second AC power line to the case of the appliance to generate a second current detection signal; and ground coupling means for connecting, in response to the first current detection signal, the first AC power line as the external ground to the case of the appliance;
for connecting, in response to the second current detection signal, the second AC power line as the external ground to the case of the appliance; and
for connecting the neutral ground point as the external ground to the case of the appliance when the first and the second current detection signals are absent. - View Dependent Claims (2, 3, 4)
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5. An apparatus for detecting a leakage current, for use in an electric appliance, which comprises:
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switching means for coupling a load of the appliance to first and second AC power lines; ground connection means for coupling a case of the electric appliance to one of the first and the second AC power lines as an external ground; current sensing means for being coupled between the case of the appliance and said one of the first and the second AC power lines, for detecting a current flowing between the case of the appliance and said one of the first and the second AC power lines to generate a current detection signal when the current is greater than a predetermined value; and switch drive means for generating, in response to the current detection signal, a switch drive signal to uncouple the first and the second AC lines from the load. - View Dependent Claims (6)
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7. An apparatus for coupling AC input to a load of an electric home appliance, which comprises:
a ground connection circuit for coupling a case of the electric appliance to an external ground, comprising; neutral ground generating means for combining signals on first and second AC power lines to produce a neutral ground point; first detection means for detecting a current flow from the first AC power line to the case of the appliance to generate a first current detection signal; second detection means for detecting a current flow from the second AC power line to the case of the appliance to generate a second current detection signal; and ground coupling means for connecting, in response to the first current detection signal, the first AC power line as the external ground to the case of the appliance;
for connecting, in response to the second current detection signal, the second AC power line as the external ground to the case of the appliance; and
for connecting the neutral ground point as the external ground to the case of the appliance when the first and the second current detection signals are absent; and
leakage current shielding means for detecting a leakage current, comprising;switching means for coupling a load of the appliance to the first and the second AC power lines; current sensing means for being coupled between the case of the appliance and one of the first and the second AC power lines which is connected to the case of the appliance as the external ground, for detecting a current flowing between the case of the appliance and said one of the first and the second AC power lines to generate a current detection signal when the current is greater than a predetermined value; and switch drive means for generating, in response to the current detection signal, a switch drive signal to uncouple the first and the second AC lines from the load. - View Dependent Claims (8, 9, 10, 11)
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12. A method for coupling a case of an electric appliance to an external ground, the method comprising:
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combining signals on first and second AC power lines to produce a neutral ground point; detecting a current flow from the first AC power line to the case of the appliance to generate a first current detection signal; detecting a current flow from the second AC power line to the case of the appliance to generate a second current detection signal; in response to the first current detection signal, connecting the first AC power line as the external ground to the appliance case; in response to the second current detection signal, connecting the second AC power line as the external ground to the appliance case; and when the first and second current detection signals are absent, connecting the neutral ground point as the external ground to the appliance case. - View Dependent Claims (13)
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14. A method for detecting a leakage current, for use in an electric appliance, the method comprising:
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coupling a load of the appliance to first and second AC power lines; coupling a case of the appliance to one of the first and second AC power lines as an external ground; with a current sensing means coupled between the case of the appliance and said one of the first and second AC power lines, detecting a current flowing between the case of the appliance and said one of the first and second AC power lines to generate a current detection signal when the current is greater than a predetermined value; and in response to the current detection signal, uncoupling the first and second AC power lines from the load.
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Specification