Self-reparable device to generate a high voltage, and method for repairing a device to generate a high voltage

1. A generator for producing a high voltage from a power supply voltage comprising:

an oscillator for producing a driving signal;

a charge pump for producing the high voltage from the power supply voltage as a function of the driving signal, said charge pump comprising

n series-connected voltage step-up stages including a first step-up stage receiving the power supply voltage and a last step-up stage producing the high voltage, with n being greater than 1,

at least one replacement step-up stage; and

a switching circuit for replacing a damaged one of said n series-connected voltage step-up stages with said at least one replacement stage when a warning signal is received;

a voltage regulator for producing an activation signal for activating said oscillator if the high voltage is below a desired value; and

a detector for producing the warning signal if said charge pump is defective.

2. A generator according to claim 1 , wherein said detector produces the warning signal when the activation signal is kept active by said regulator during a period of time greater than a predefined time.

3. A generator according to claim 2 , wherein said detector comprises:

a first charge accumulator for receiving a charging current;

a comparator for producing the warning signal when a potential at said first charge accumulator reaches a predefined value; and

a selectable circuit path for short-circuiting said first charge accumulator when the activation signal is inactive.

4. A generator according to claim 3 , wherein the charging current is independent of the power supply voltage.

5. A generator according to claim 2 , wherein said detector further comprises a delay circuit for extending duration of the predefined time during a pump-starting phase of said charge pump.

6. A generator according to claim 1 , wherein said detector produces the warning signal when the high voltage falls below a critical value.

7. A generator according to claim 6 , wherein said detector comprises:

a voltage level detector for producing the warning signal when the high voltage is below the critical value;

an inhibit circuit for inhibiting said voltage level detector during a first activation of the activation signal.

8. A generator according to claim 1 , wherein said detector produces the warning signal when the activation signal is kept active during a period of time greater than a predefined time, or when the high voltage falls below a critical value.

9. A high-voltage generator comprising:

an oscillator for producing a driving signal;

a charge pump for producing a high voltage from a power supply voltage based upon receiving the driving signal, said charge pump comprising

a plurality of voltage step-up stages connected in series, said plurality of voltage step-up stages including a first step-up stage receiving the power supply voltage and a last step-up stage producing the high voltage,

at least one replacement step-up stage; and

at least one switch for replacing a damaged one of said plurality of voltage step-up stages with said at least one replacement stage when a warning signal is received;

a voltage regulator for producing an activation signal for activating said oscillator if the high voltage is below a desired value; and

a detector for producing the warning signal if one of said plurality of step-up stages is defective.

10. A high-voltage generator according to claim 9 , wherein said detector produces the warning signal when the activation signal is kept active by said regulator during a period of time greater than a predefined time.

11. A high-voltage generator according to claim 10 , wherein said detector comprises:

a first charge accumulator for receiving a charging current;

a comparator for producing the warning signal when a potential at said first charge accumulator reaches a predefined value; and

a selectable circuit path for short-circuiting said first charge accumulator when the activation signal is inactive.

12. A high-voltage generator according to claim 11 , wherein the charging current is independent of the power supply voltage.

13. A high-voltage generator according to claim 10 , wherein said detector further comprises a delay circuit for extending duration of the predefined time during a pump-starting phase of said charge pump.

14. A high-voltage generator according to claim 9 , wherein said detector produces the warning signal when the high voltage falls below a critical value.

15. A high-voltage generator according to claim 14 , wherein said detector comprises:

a voltage level detector for producing the warning signal when the high voltage is below the critical value;

an inhibit circuit for inhibiting said voltage level detector during a first activation of the activation signal.

16. A high-voltage generator according to claim 9 , wherein said detector produces the warning signal when the activation signal is kept active during a period of time greater than a predefined time, or when the high voltage falls below a critical value.

17. A method for repairing a high-voltage generator comprising an oscillator for producing a driving signal; a charge pump for producing a high voltage from a power supply voltage based upon receiving the driving signal, the charge pump comprising a plurality of series-connected voltage step-up stages including a first step-up stage receiving the power supply voltage and a last step-up stage producing the high voltage, at least one replacement step-up stage, and a switching circuit for replacing a damaged one of the plurality of series-connected voltage step-up stages with the at least one replacement stage when a warning signal is received; a voltage regulator for producing an activation signal for activating the oscillator if the high voltage is below a desired value; and a detector for producing the warning signal when a defective state of the charge pump has been detected, the method comprising:

monitoring the charge pump;

determining if the charge pump is defective based upon the detector generating the warning signal; and

activating the switching circuit based upon receiving the warning signal for replacing a damaged one of the plurality of series-connected voltage step-up stages with the at least one replacement step-up stage.

18. A method according to claim 17 , wherein replacing the damaged one of the plurality of series-connected voltage step-up stages comprises:

disconnecting the damaged step-up stage in the charge pump;

connecting the at least one replacement step-up stage in place of the damaged step-up stage; and

storing information that the charge pump has been repaired.

19. A method according to claim 17 , wherein the last step-up stage of the charge pump is replaced by the at least one replacement step-up stage.

20. A method according to claim 17 , wherein the at least one replacement step-up stage comprises a plurality of step-up stages, wherein more than one step-up stages are defective, and the defective step-up stages are replaced by an equivalent number of replacement step-up stages.

21. A method according to claim 17 , wherein after a defective step-up stage has been replaced, further comprising:

monitoring the charge pump again;

determining if the charge pump is defective based upon the detector generating the warning signal; and

activating the switching circuit based upon receiving the warning signal for replacing a step-up stage ranked immediately below a previously replaced step-up stage.