Miscellaneous active electrical nonlinear devices – circuits – and – Gating – Superconductive device
Reexamination Certificate
1999-05-10
2001-09-25
Callahan, Timothy P. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Gating
Superconductive device
C327S554000, C327S374000, C327S205000, C326S003000
Reexamination Certificate
active
06294946
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates a switching circuit. In particular, the present invention relates to a switching circuit comprising a switch which on activation discharges a capacitance.
Typically, a switching circuit utilises a switch to complete an electrical circuit. When the switch is closed the circuit is closed and when the switch is open the circuit is open. One disadvantage of such a switch is that power is dissipated while the switch remains closed.
It would be desirable to provide a switching circuit which consumes less power.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a switching circuit, comprising: a first node for receiving a first voltage; a second node for providing an output; a third node for receiving a second voltage; a capacitance coupled between the second node and the third node; means for intermittently charging the capacitance to provide a first output voltage from the second node; and a switch connected between the first node and the second node for isolating the second node from the first node when open and for discharging the capacitance to provide a second output voltage when closed.
In one embodiment the switching circuit further comprises a buffer connected to the second node.
In another embodiment the switching circuit further comprises a latch connected to the second node.
Preferably, the latch is a Schmitt trigger latch.
Preferably, the means for charging the capacitance comprises a second switch responsive to a control signal for connecting the second node to a voltage source.
In a preferred embodiment the control signal is a pulsed signal.
Preferably, the duration of a pulse is substantially less than the period between pulses.
More preferably, the pulse has a duration which is {fraction (1/500)} of its period.
Preferably, the pulse has a duration of about 1 ms.
Preferably, the voltage source is a positive voltage and the first and second voltages are ground.
In one embodiment the capacitance comprises a stray capacitance.
Preferably, the switching circuit comprises a capacitor for providing at least a portion of the capacitance.
It will be appreciated that in the present invention, when the first switch is open, power is dissipated only while the capacitance charges. Once the capacitance has been charged and when the first switch is open negligible current will be drawn by the capacitor and negligible power will be consumed. When the first switch is closed, the voltage at the second node quickly discharges. When the second switch is then closed, the voltage at the second node increases in a stepwise fashion as the capacitance is intermittently charged. The voltage at the second node will depend upon the total charge supplied by the means for intermittently charging the capacitance and the value of the capacitance.
A preferred embodiment of the present invention will now be described hereinbelow by way of example only with reference to the accompanying drawings:
REFERENCES:
patent: 4047052 (1977-09-01), Koubek et al.
patent: 4752741 (1988-06-01), Kim et al.
patent: 5258662 (1993-11-01), Skovmand
patent: 5331230 (1994-07-01), Ichihara
patent: 5410195 (1995-04-01), Ichihara
patent: 5477185 (1995-12-01), Jouen
patent: 5973518 (1999-10-01), Vallancourt
Astra Aktiebolag
Callahan Timothy P.
Fish & Richardson P.C.
Luu An T.
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