Method and circuit for adjusting an RC element

Abstract

A method for adjusting an RC element with a capacitive element with adjustable capacitance, in particular a capacitor, and/or a resistive element with adjustable resistance, in particular an ohmic resistance, is provided. Multiple adjustment cycles are performed, wherein each adjustment cycle sets a standard value for the capacitance of the capacitive element and/or for the resistance of the resistive element, charges the capacitive element for a predefinable charging time, compares a charging voltage to which the capacitive element has been charged during the charging time with a reference voltage. A comparison result is obtained that indicates whether the charging voltage is larger than the reference voltage or vice versa. In addition, the standard value for the capacitance and/or the resistance and/or the charging time for a subsequent adjustment cycle is selected as a function of the comparison result of at least one preceding adjustment cycle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

FIG. 1 is a schematic representation a circuit according to an embodiment of the present invention;

FIG. 2 illustrates a detail view of the capacitive element depicted in FIG. 1;

FIG. 3 a is a flow diagram of an embodiment of the inventive adjustment method; and

FIG. 3 b is another flow diagram of an embodiment of the inventive adjustment method.

Claims

1. A method for adjusting an RC element with a capacitive element having an adjustable capacitance and/or a resistive element with an adjustable resistance, wherein multiple adjustment cycles are performed, each adjustment cycle comprising: setting a standard value for the capacitance of the capacitive element and/or for the resistance of the resistive element;charging the capacitive element for a predefinable charging time;comparing a charging voltage to which the capacitive element has been charged during the charging time with a reference voltage;obtaining a comparison result that indicates whether the charging voltage is larger than the reference voltage or vice versa; andselecting a standard value for the capacitance and/or the resistance and/or the charging time for a subsequent adjustment cycle as a function of the comparison result of at least one preceding adjustment cycle.

2. The method according to claim 1, wherein the standard value for the capacitance for the next adjustment cycle is increased/decreased and/or wherein the standard value for the resistance for the next adjustment cycle is increased/decreased if the charging voltage in the preceding adjustment cycle was larger/smaller than the reference voltage.

3. The method according to claim 1, wherein the charging time for the next adjustment cycle is increased/decreased if the charging voltage in the preceding adjustment cycle was larger/smaller than the reference voltage.

4. The method according to claim 1, wherein the capacitive element is charged by a charging circuit having a constant current.

5. The method according to claim 1, wherein the capacitive element is charged by a charging circuit through a dropping resistor and a reference voltage source, wherein the dropping resistor is formed at least partially from the resistive element.

6. The method according to claim 1, wherein a maximum or minimum adjustable capacitance of the capacitive element and/or a maximum or minimum adjustable resistance of the resistive element is chosen as a standard value for a first adjustment cycle.

7. The method according to claim 6, wherein the standard value is changed by a predefinable step size between each set of successive adjustment cycles.

8. The method according to claim 7, wherein the step size is constant.

9. The method according to claim 7, wherein the step size is variable.

10. The method according to claim 9, wherein the step size is chosen as a function of the number of adjustment cycles previously performed.

11. The method according to claim 9, further comprising the steps of: maintaining a present value of the step size for the next adjustment cycle if the comparison result of the current adjustment cycle is identical to the comparison result of the preceding adjustment cycle;reducing or halving the present step size for the next adjustment cycle if the comparison result of the current adjustment cycle is not identical to the comparison result of the preceding adjustment cycle; andending the adjustment when the step size chosen for the next adjustment cycle drops below a predefined threshold value.

12. The method according to claim 1, wherein the capacitive element is discharged after the comparison step.

13. The method according to claim 1, wherein a charging circuit used to charge the capacitive element is disconnected from the capacitive element before the comparison step.

14. A circuit for adjusting an RC element having a capacitive element with an adjustable capacitance and/or a resistive element with an adjustable resistance, the circuit comprising: a charging circuit for charging the capacitive element that is connectable at least to a first terminal of the capacitive element;a comparator circuit having a first input, a second input, and an output, the first input being supplied with a reference potential corresponding to a reference voltage, and the second input being connectable to the first terminal of the capacitive element; anda control device that is configured to control the circuit by an adjustment process, the adjustment process comprising: setting a standard value for the capacitance of the capacitive element and/or for the resistance of the resistive element;charging the capacitive element for a predefinable charging time;comparing a charging voltage to which the capacitive element has been charged during the charging time with a reference voltage;obtaining a comparison result that indicates whether the charging voltage is larger than the reference voltage or vice versa; andselecting a standard value for the capacitance and/or the resistance and/or the charging time for a subsequent adjustment cycle as a function of the comparison result of at least one preceding adjustment cycle.

15. The circuit according to claim 14, wherein the control device has a state machine and/or is designed as a state machine.

16. The circuit according to claim 14, further comprising a discharging circuit for discharging the capacitive element, the discharging circuit being connectable to at least one terminal of the capacitive element.

17. The circuit according to claim 14, further comprising a clock generator circuit for producing a clock signal.

18. The circuit according to claim 14, further comprising a switch for connecting the charging circuit to the capacitive element.

19. The method according to claim 1, wherein the capacitive element is a capacitor.

20. The method according to claim 1, wherein the resistive element is an ohmic resistance element.