Ac overcurrent protection circuit

Claim 2

An AC protection circuit comprising: switching means which can be coupled between a source of AC signals and a load; threshold means, including a first RC circuit having a time constant of less than the duration of one cycle of said AC signal, said threshold means being responsively to the current flowing through said switching means for open-circuiting said switching means within one cycle of said AC signal when inrush current inhibiting means for inhibiting said threshold means from open circuiting said switching means for a certain time when said current which exceeds said given value is an inrush current.

Claim 3

The invention according to claim 1, wherein said inrush current inhibiting meaNs includes a second RC time constant circuit having a time constant greater than the duration of a plurality of cycles of said AC signal, said inrush inhibiting means preventing said threshold means from open-circuiting said switching means for said plurality of cycles for inrush currents exceeding said given value.

Claim 4

A two-terminal AC overcurrent protection circuit capable of being serially coupled between a source of AC power and a load for preventing an overcurrent other than an inrush overcurrent from being applied from said source to said load, said circuit comprising, AC switching means and a sampling resistance serially connected between two terminals, a capacitance means including a capacitor and a diode, the cathode of said diode being coupled to one side of said capacitor; means for coupling the other side of said capacitor and the anode of said diode across said sampling resistance; said capacitor being responsive to the peak value of the voltage across said resistance, said capacitor being charged to at least a certain voltage during a certain number of cycles of said voltage across said resistance; means for charging said capacitor to a voltage greater than said certain voltage, said diode being reversed biased when said capacitor is charged above said certain voltage; and threshold means coupled in parallel with said capacitance means for open-circuiting said switching means on the occurrence of an overcurrent after said capacitor has charged to said certain voltage.

Claim 5

A two-terminal AC overcurrent protection circuit capable of being serially coupled between a source of AC power and a load for preventing an overcurrent other than an inrush overcurrent from being applied from said source to said load, said circuit comprising, AC switching means and a sampling resistance serially connected between two terminals, a capacitance means including a capacitor and a diode, the cathode of said diode being coupled to one side of said capacitor; means for coupling the other side of said capacitor and the anode of said diode across said sampling resistance; said capacitor being responsive to the peak value of the voltage across said resistance, said capacitor being charged to at least a certain voltage during a certain number of cycles of said voltage across said resistance; means for charging said capacitor to a voltage greater than said certain voltage, said diode being reversed biased when said capacitor is charged above said certain voltage; and threshold means coupled in parallel with said capacitance means for open-circuiting said switching means on the occurrence of an overcurrent after said capacitor has charged to said certain voltage.

Claim 6

The invention according to claim 3, wherein said threshold means includes a threshold device having a threshold voltage, and means for coupling said threshold device between said anode of said diode and said AC switching means, said threshold voltage of said device being said certain voltage, whereby whenever the voltage at the anode of said diode exceeds said threshold voltage and said capacitor is charged above said certain voltage, said threshold device open circuits said switching means.

Claim 7

The invention according to claim 4 wherein the voltage across said capacitor is less than said certain voltage before said power is applied to said load.