Hearing instrument comprising switched capacitor DC-DC converter

1. A hearing instrument comprising:

a rechargeable battery source providing a battery supply voltage:

a switched capacitor DC-DC converter comprising a DC input configured to receive the battery supply voltage, wherein the converter is configured for converting the battery supply voltage into a higher or lower DC output voltage; and

at least one active circuit configured to receive the DC output voltage for energizing active components of the at least one active circuit;

wherein the at least one active circuit comprises a class D output amplifier, the class D output amplifier being coupled upstream with respect to a speaker of the hearing instrument.

2. The hearing instrument according to claim 1 , further comprising a control and processing circuit comprising:

a first audio input channel for receipt of a first audio signal, and

a signal processor for processing of the first audio signal for generating a compensated microphone signal according to a hearing loss of a user;

wherein the compensated microphone signal is for application to an audio input of the class D output amplifier for generation of a modulated output signal at a predetermined modulation frequency for application to the speaker.

3. A hearing instrument comprising:

a rechargeable battery source providing a battery supply voltage;

a switched capacitor DC-DC converter comprising a DC input configured to receive the battery supply voltage, wherein the converter is configured for converting the battery supply voltage into a higher or lower DC output voltage; and

at least one active circuit configured to receive the DC output voltage for energizing active components of the at least one active circuit;

wherein the switched capacitor DC-DC converter comprises a charge pump circuit comprising a switch array driven by first and second non-overlapping clock phases derived from a clock signal.

4. The hearing instrument according to claim 3 , wherein the switch array is configured to, in the first clock phase, charge a capacitor and, in the second clock phase, discharge the capacitor.

5. The hearing instrument according to claim 3 , wherein the switched capacitor DC-DC converter further comprises an output voltage regulator.

6. The hearing instrument according to claim 5 , wherein the output voltage regulator comprises a reference voltage input for receipt of a DC reference voltage, and a feedback voltage input for receipt of a feedback voltage representative of the DC output voltage.

7. The hearing instrument according to claim 5 , wherein the output voltage regulator further comprises an error signal generator configured to combine a DC reference voltage and a feedback voltage to determine a control signal.

8. The hearing instrument according to claim 7 , wherein the output voltage regulator further comprises a loop filter configured for lowpass filtering the control signal to generate a lowpass filtered control signal.

9. The hearing instrument according to claim 8 , wherein the output voltage regulator further comprises a multi-level quantizer configured to convert the lowpass filtered control signal into a corresponding digital control signal at a predetermined sampling frequency.

10. The hearing instrument according to claim 5 , wherein the output voltage regulator further comprises a switch array controller configured to generate the first and second non-overlapping clock phases for the charge pump circuit based on the clock signal and a digital control signal.

11. The hearing instrument according to claim 5 , further comprising a clock generator, wherein the clock generator is configured to generate a predefined set of fixed clock frequencies.

12. The hearing instrument according to claim 11 , wherein the output voltage regulator is configured to select a clock frequency from the predefined set of fixed clock frequencies in accordance with a predetermined modulation frequency of a class D output amplifier.

13. The hearing instrument according to claim 12 , wherein each clock frequency of the predefined set of fixed clock frequencies is an integer multiple of the predetermined modulation frequency of the class D output amplifier.

14. The hearing instrument according to claim 12 , wherein the clock signal of the switched capacitor DC-DC converter is synchronous to another clock signal that sets the predetermined modulation frequency of the class D output amplifier.

15. The hearing instrument according to claim 1 , wherein the rechargeable battery source comprises at least one Li-Ion battery cell.

16. The hearing instrument according to claim 3 , wherein the switched capacitor DC-DC converter further comprises a multi-level quantizer, and wherein a predetermined sampling frequency of the multi-level quantizer is equal to two times a clock frequency of the clock signal.

17. The hearing instrument according to claim 3 , wherein the switch array of the charge pump circuit comprises a first controllable semiconductor switch and a second controllable semiconductor switch configured to be driven by the first clock phase, and wherein the switch array also comprises a third controllable semiconductor switch and a fourth controllable semiconductor switch configured to be driven by the second clock phase.

18. The hearing instrument according to claim 17 , wherein the first and second controllable semiconductor switches respectively comprise a first plurality of individually controllable switch segments and a second plurality of individually controllable switch segments driven respectively by first and second sets of switch segment control signals derived from the first clock phase; and

wherein the third and fourth controllable semiconductor switches respectively comprise another a third plurality of individually controllable switch segments and a fourth plurality of individually controllable switch segments driven respectively by third and fourth sets of switch segment control signals derived from the second clock phase.

19. The hearing instrument according to claim 18 , wherein the output voltage regulator is configured to, for one or more of the first, second, third and fourth controllable semiconductor switches, select respective one(s) of the first, second, third, and fourth plurality of individually controllable switch segments in accordance with an amplitude of a digital control signal.

20. The hearing instrument according to claim 18 , wherein the output voltage regulator is configured to:

switch between an on-state and an off-state of the first controllable semiconductor switch by sequentially turning-on and turning-off the first plurality of individually controllable switch segments via the first set of switch segment control signals; and/or

switch between an on-state and an off-state of the second controllable semiconductor switch by sequentially turning-on and turning-off the second plurality of individually controllable switch segments via the second set of switch segment control signals; and/or

switch between an on-state and an off-state of the third controllable semiconductor switch by sequentially turning-on and turning-off the third plurality of individually controllable switch segments via the third set of switch segment control signals; and/or

switch between an on-state and an off-state of the fourth controllable semiconductor switch by sequentially turning-on and turning-off the fourth plurality of individually controllable switch segments via the fourth set of switch segment control signals.

21. The hearing instrument according to claim 5 , wherein the output voltage regulator is configured to switch between individual clock frequencies of a predefined set of fixed clock frequencies in accordance with an amplitude of a digital control signal.