Voltage supply circuit and microphone unit comprising the same

• US 20060062406A1
• Filed: 08/16/2005
• Published: 03/23/2006
• Est. Priority Date: 08/17/2004
• Status: Active Grant

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: NEC Electronics Corporation (Renesas Electronics Corporation)
• Inventors: Kinoshita, Hiroshige
• Granted Patent: US 8,041,056 B2
• Time in Patent Office: Days
• US Class Current: 381/113
• CPC Class Codes: H04R 3/00 Circuits for transducers , loudspeakers or microphones

Abstract

A voltage supply circuit comprises a voltage control circuit for outputting a bias voltage control signal according to a set value based on a bias voltage of a sensor and a voltage generation circuit for generating the bias voltage to be applied to the sensor based on the bias voltage control signal.

Claims

1. A voltage supply circuit comprising:

a voltage control circuit for outputting a bias voltage control signal according to a set value based on a bias voltage of a sensor; and

a voltage generation circuit for generating the bias voltage to be applied to the sensor based on the bias voltage control signal.

2. The voltage supply circuit as claimed in claim 1, wherein the voltage control circuit comprises a storage circuit for holding the set value.

3. The voltage supply circuit as claimed in claim 2, wherein the storage circuit stores the set value responding to a set value holding signal to be input to a terminal for sensitivity adjustment of the voltage control circuit.

4. The voltage supply circuit as claimed in claim 1, wherein the voltage generation circuit comprises a PWM circuit for outputting a clock pulse based on the bias voltage control signal, and a charge pump circuit for generating the bias voltage based on the clock pulse to be output by the PWM circuit.

5. The voltage supply circuit as claimed in claim 2, wherein the voltage generation circuit comprises a PWM circuit for outputting a clock pulse based on the bias voltage control signal, and a charge pump circuit for generating the bias voltage based on the clock pulse to be output by the PWM circuit.

6. The voltage supply circuit as claimed in claim 1, wherein the voltage control circuit generates the bias voltage control signal based on a sensitivity adjustment signal to be input via the terminal for sensitivity adjustment of the voltage control circuit.

7. The voltage supply circuit as claimed in claim 2, wherein the voltage control circuit generates the bias voltage control signal based on a sensitivity adjustment signal to be input via the terminal for sensitivity adjustment.

8. The voltage supply circuit as claimed in claim 5, wherein the voltage control circuit comprises a PWM duty control circuit for generating the bias voltage control signal based on a sensitivity adjustment signal to be input via the terminal for sensitivity adjustment of the voltage control circuit.

9. The voltage supply circuit as claimed in claim 2, wherein the storage circuit stores a plurality of set values, and the voltage control circuit selects an arbitrary set value out of the plurality of set values based on a sensitivity switching signal, and outputs a bias voltage control signal corresponding to the selected set value.

10. The voltage supply circuit as claimed in claim 3, wherein the storage circuit stores a plurality of set values, and the voltage control circuit selects an arbitrary set value out of the plurality of set values based on a sensitivity switching signal, and outputs a bias voltage control signal corresponding to the selected set value.

11. The voltage supply circuit as claimed in claim 6, wherein the storage circuit stores a plurality of set values, and the voltage control circuit selects an arbitrary set value out of the plurality of set values based on a sensitivity switching signal, and outputs a bias voltage control signal corresponding to the selected set value.

12. The voltage supply circuit as claimed in claim 7, wherein the storage circuit stores a plurality of set values, and the voltage control circuit selects an arbitrary set value out of the plurality of set values based on a sensitivity switching signal, and outputs a bias voltage control signal corresponding to the selected set value.

13. The voltage supply circuit as claimed in claim 5, wherein the voltage generation circuit further comprises a change pump stage count switching circuit for switching the number of boosting stages of the charge pump circuit.

14. A microphone unit, comprising:

a microphone to which bias voltage is supplied;

a voltage generation circuit for boosting the power supply voltage and generating the bias voltage based on a bias voltage control signal; and

a voltage control circuit for outputting the bias voltage control signal based on a set value of the bias voltage.

15. The microphone unit as claimed in claim 14, wherein the voltage control circuit further comprises a storage circuit for storing the set value of the bias voltage.

16. The microphone unit as claimed in claim 15, wherein the storage circuit stores a plurality of set values of the bias voltage.

17. The microphone unit as claimed in claim 14, wherein the voltage control circuit stores a set value of the bias voltage based on a signal to be input to a terminal for sensitivity adjustment.

18. The microphone unit as claimed in claim 15, wherein the voltage control circuit stores a set value of the bias voltage based on a signal to be input to a terminal for sensitivity adjustment.

19. A sensitivity adjustment method for a microphone unit which comprises a condenser microphone, an amplification circuit and a voltage supply circuit which supplies a bias voltage based on a set value to the condenser microphone, comprising:

detecting a difference between a reference voltage and an output voltage of the condenser microphone;

outputting a sensitivity adjustment instruction;

adjusting the output voltage based on the sensitivity adjustment instruction; and

,

storing a control signal corresponding to the adjusted output voltage as the set value.

20. The sensitivity adjustment method as claimed in claim 19, wherein

when the difference between the reference voltage and the output voltage of the condenser microphone is within a tolerance range, the output voltage is determined as the adjusted output voltage.

21. The sensitivity adjustment method as claimed in claim 19, further comprising;

switching the reference voltage; and

inputting a sound signal corresponding to the switched reference voltage.

22. A sensitivity adjustment device for a microphone unit which comprises a condenser microphone and a voltage supply circuit which supplies a bias voltage based on a set value to the condenser microphone, comprising:

a comparator which compares an output voltage of the condenser microphone with a reference voltage; and

,

a control instruction generation circuit which outputs a sensitivity adjustment instruction for adjusting the output voltage of the condenser microphone based on the reference voltage, and outputs a storing instruction for storing the set value based on the adjusted output voltage.