Device for generating a high voltage supply

Claim 2

A voltage generator including: a capacitor; positive and negative power supply rails; first and second normally non-conducting M.I.S. transistors each of which is connected between a respective plate of the capacitor and a respective power supply rail; means to apply electrical pulses to a gate electrode of one of the first and second transistors to render the first and second transistors conducting for a limited period to charge the capacitor and then isolate the capacitor on the first and second switching devices reverting to their non-conducting state; a normally non-conducting third M.I.S. transistor connected between one of the plates of the capacitor and the opposite power supply rail to that to which the one capacitor plate is connectable by the respective one of the first and second transistors; and, output means connected to the other capacitor plate; the third transistor having its gate electrode connected to the said other capacitor plate for biasing the third transistor to a conducting state in response to the said other cApacitor plate attaining a predetermined voltage, whereby the third transistor is operative, on isolation of the capacitor subsequent to charging thereof, to connect the one capacitor plate to the said opposite power supply rail to produce an enhanced voltage on the said other capacitor plate.

Claim 3

A voltage generator according to claim 1, wherein the output means comprises a fourth M.I.S. transistor and a second capacitor, the fourth transistor having its gate electrode and one current carrying terminal connected to the said other capacitor plate, the second capacitor being connected between the other current carrying terminal of the fourth transistor and the power supply rail to which the said one capacitor plate is connected by the third transistor.

Claim 4

A voltage generator including: a capacitor having first and second plates; positive and negative power supply rails; normally open first and second electrically controllable switching devices each of which is connected between a respective one of said first and second plates of the capacitor and a respective power supply rail; means to trigger the first and second switching devices into the closed state thereof for a limited period to charge the capacitor and to then isolate the capacitor on the first and second switching devices reverting to their normally open state; a normally open third electrically controllable switching device connected between one of the first and second plates of the capacitor and the power supply rail to opposite that which the said one capacitor plates is connectable by the respective one of the first and second switching devices; and, output means connected to the other capacitor plate; the third switching device being operatively connected to the said other capacitor plate for triggering to a closed state in response to the said other capacitor plate attaining a predetermined voltage, whereby the third switching device is operative, on isolation of the capacitor subsequent to charging thereof, to connect the said one of the first and second capacitor plates to the said opposite power supply rail to produce an enhanced voltage on the said other of the first and second capacitor plates.

Claim 5

A voltage generator including: a capacitor having first and second plates; positive and negative power supply rails; normally open first and second electrically controllable switching devices each of which is connected between a respective one of said first and second plates of the capacitor and a respective power supply rail; means to trigger the first and second switching devices into the closed state thereof for a limited period to charge the capacitor and to then isolate the capacitor on the first and second switching devices reverting to their normally open state; a normally open third electrically controllable switching device connected between one of the first and second plates of the capacitor and the power supply rail to opposite that which the said one capacitor plates is connectable by the respective one of the first and second switching devices; and, output means connected to the other capacitor plate; the third switching device being operatively connected to the said other capacitor plate for triggering to a closed state in response to the said other capacitor plate attaining a predetermined voltage, whereby the third switching device is operative, on isolation of the capacitor subsequent to charging thereof, to connect the said one of the first and second capacitor plates to the said opposite power supply rail to produce an enhanced voltage on the said other of the first and second capacitor plates.

Claim 6

A voltage generator according to claim 3, wherein the third switching device comprises an M.I.S. transistor having its gate electrode connected to the said other of the first and second capacitor plate.

Claim 7

A voltage generator according to claim 4, wherein the gate electrode of the third switching device is connected to one plate of a protective capacitor having its other plate connected to ground.

Claim 8

A voltage generator according to claim 3, wherein the means to trigger the first and second switching devices comprises means to apply electrical pulses to a control electrode of one of the first and second switching devices.

Claim 9

A voltage generator according to claim 3, wherein the output means comprises a fourth electrically controllable switching device connected to the said other capacitor plate, and a second capacitor, the fourth switching device being arranged to feed the enhanced voltage to the second capacitor across which a voltage output can be taken.