Abstract An electric timing circuit for the time delayed delivery of a voltage pulse to an electric fuze element or other current or voltage sensitive element uses a capacitor voltage source which can be charged from an external source of electric potential. The capacitor discharges through the leakage resistance of its dielectric and through leakage resistance of semiconductor devices in the biased "off" state, until the capacitor voltage decreases to a preset value, at which time a threshold value switch connects the electric element to the capacitor voltage source. The threshold value switch is constituted by two series connected Field Effect Transistors, one N channel type and one P channel type. Both transistors are biased in the "off" condition by the circuit connections until the capacitor voltage decreases to the threshold level and turns both transistors "on". The two non-conducting transistor channels in series permit a very long discharge time for a given capacitor. One embodiment of the invention utilizes the negligible current threshold switch in series with the gate circuit of a thyristor to trigger the thyristor and permit a large current flow through the thyristor and the series connected electric element. A second embodiment of the invention uses the two-transistor threshold switch in series with a sensitive electric element.
An electric timing circuit comprising in combination: a threshold value switch including an N-channel F.E.T. and a P-channel F.E.T. having their drain-source path connected in series, the gate electrodes of each connected to the drain of the other and their source electrodes connected together; a voltage sensitive element; a self contained voltage source; and means connecting said source, said element and the drain-source path of said F.E.T.s in a series circuit.
Claim 2
Dependent Claim
71 words
An electric timing circuit comprising in combination: a threshold value switch including an N-channel F.E.T. and a P-channel F.E.T. having their drain-source path connected in series, the gate electrodes of each connected to the drain of the other and their source electrodes connected together; a voltage sensitive element; a self contained voltage source; and means connecting said source, said element and the drain-source path of said F.E.T.s in a series circuit.
Claim 3
Dependent Claim
15 words
An electric timing circuit, as claimed in claim 1, said voltage source being a capacitor.
Claim 4
Dependent Claim
25 words
An electric timing circuit, as claimed in claim 1, including means connected in said timing circuit providing a constant current discharge of said voltage source.
Claim 5
Dependent Claim
36 words
An electric timing circuit, as claimed in claim 2, including an electric valve connected in series with said voltage sensitive element and having a control electrode; said threshold value switch being connected to said control electrode.
Claim 6
Dependent Claim
15 words
An electric timing circuit, as claimed in claim 4, said electric valve being a thyristor.
Claim 7
Dependent Claim
49 words
An electric timing circuit, as claimed in claim 4, including a pair of terminals for connection to an external source of electric potential; said capacitor being connected across said terminals; and a second capacitor connected between said control electrode of said electric valve and one end of said element.
Claim 8
Dependent Claim
44 words
An electric timing circuit, as claimed in claim 4 including a mechanical switch to permit charging said capacitor from an external charging voltage source and subsequently disconnecting said capacitor from said external charging voltage source and connecting said capacitor to said threshold value switch.