Current fault protection system
First Claim
1. A protection system for a power supply for preventing the drawing of an excessive amount of current by an electrical load fault comprising:
- (a) means for sensing the magnitude of current flowing to the electrical load and producing a first control signal having a first level when current flow is less than a maximum amount of the power supply and having a second level when current flow exceeds the maximum amount; and
a second control signal having a first level which occurs in response to detection of current flow greater than the maximum amount of current flow and a second level when a load fault is not present;
(b) a switching means disposed in series with the load, conduction of the switching means being controlled by the first control signal and passing current when the first control signal is at the first level; and
(c) a shunt circuit, coupled in parallel with the switching means, the shunt circuit containing a switching circuit coupled to an impedance which limits the amount of current drawn by the load when the impedance is in series with the load, conduction of the switching circuit being controlled by the second control signal and passing current to permit current flow through the impedance of the shunt circuit when the second control signal has the first level and blocking current flow when the second control signal has the second level.
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Accused Products
Abstract
An overcurrent protection system (10) for a power supply is disclosed. The system monitors the instantaneous flow of current between a power supply (12) and an electrical load (16) to detect when the flow of current exceeds a maximum rated amount. A counter (30) is used for counting the number of times that samples of the flow of current exceed the maximum rated amount synchronous with zero current crossing to generate a trip signal when a predetermined count is reached which disconnects the power supply (12) from the load. The counter (30) is decremented each time a predetermined time interval elapses in which the flow of current above the maximum rate is not detected as measured from a point of zero current flow between the power supply (12) and the electrical load (14). The invention may be used for both AC and DC power supplies.
58 Citations
18 Claims
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1. A protection system for a power supply for preventing the drawing of an excessive amount of current by an electrical load fault comprising:
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(a) means for sensing the magnitude of current flowing to the electrical load and producing a first control signal having a first level when current flow is less than a maximum amount of the power supply and having a second level when current flow exceeds the maximum amount; and
a second control signal having a first level which occurs in response to detection of current flow greater than the maximum amount of current flow and a second level when a load fault is not present;(b) a switching means disposed in series with the load, conduction of the switching means being controlled by the first control signal and passing current when the first control signal is at the first level; and (c) a shunt circuit, coupled in parallel with the switching means, the shunt circuit containing a switching circuit coupled to an impedance which limits the amount of current drawn by the load when the impedance is in series with the load, conduction of the switching circuit being controlled by the second control signal and passing current to permit current flow through the impedance of the shunt circuit when the second control signal has the first level and blocking current flow when the second control signal has the second level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A protection system for a power supply for preventing the drawing of an excessive amount of current by an electrical load fault comprising:
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(a) means for sensing the magnitude of current flowing to the electrical load and producing a first control signal having a first level when current flow is less than a maximum rated amount of the power supply and having a second level when current flow exceeds the maximum rated amount; (b) a switching means disposed in series with the load, conduction of the switching means being controlled by the first control signal and passing current when the first control signal is at the first level; and (c) a shunt circuit, coupled in parallel with the switching means, the shunt circuit containing a switching circuit coupled to an impedance which limits the amount of current drawn by the load when the impedance is in a path of current flow between the power supply and the load, conduction of the shunt circuit being controlled by the first control signal and passing current to permit current flow through the impedance of the shunt circuit when the first control signal has the second level and blocking current flow when the first control signal has the first level.
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Specification