Microphone array
A microphone array is disclosed. In an embodiment a microphone array includes a power supply circuit arrangement, at least one microphone circuit and a voltage detector. The power supply arrangement includes a switched-mode power supply circuit configured to generate at least two different levels of output voltage. The at least one microphone circuit includes a microphone transducer, and audio amplifier, a switchable voltage regulator circuit supplying the amplifier. The voltage detector is configured to switch the output voltage of the voltage regulator circuit depending on the voltage supplied by the switched-mode power supply circuit.
1. A microphone array comprising:
a power supply circuit arrangement comprising:
a switched-mode power supply circuit comprising an input terminal for a supply voltage, an output terminal for an output voltage and a terminal for a clock signal, the switched-mode power supply circuit configured to generate at least two different levels of the output voltage depending on a level of the supply voltage;
at least one microphone circuit comprising:
a microphone transducer having an output terminal; and
an amplifier having a supply terminal for a supply voltage and an output terminal for an audio signal, the output terminal of the microphone transducer connected to the amplifier; and
a voltage regulator circuit having an input terminal and an output terminal, the input terminal connected to the output terminal of the switched-mode power supply circuit and the output terminal connected to the supply terminal of the amplifier, wherein the voltage regulator circuit is configured to supply a voltage at the output terminal of the voltage regulator circuit in dependence on the level of the output voltage of the switched-mode power supply circuit.
2. The microphone array according to claim 1 , wherein the switched-mode power supply circuit is configured to generate a higher voltage when the supply voltage is higher than a threshold and a lower voltage when the level of the supply voltage is lower than the threshold.
3. The microphone array according to claim 1 , wherein the power supply circuit arrangement further comprises a monitoring circuit configured to monitor the level of the supply voltage and a control circuit configured to control the clock signal in response to the level monitored by the monitoring circuit.
4. The microphone array according to claim 3 , wherein the control circuit is configured to change a duty cycle of the clock signal to be supplied to the switched-mode power supply circuit depending on a determination made by the monitoring circuit.
5. The microphone array according claim 1 , wherein the voltage regulator circuit is configured to provide a voltage at the output terminal switchably controlled depending on a control signal.
6. The microphone array according to claim 1 , wherein the voltage regulator circuit is configured to supply a higher voltage at the output terminal of the voltage regulator circuit, when the voltage at the input terminal of the voltage regulator circuit is higher than a threshold, and to supply a lower voltage at the output terminal of the voltage regulator circuit, when the voltage at the input terminal of the voltage regulator circuit is lower than the threshold.
7. The microphone array according to claim 6 , wherein the microphone circuit comprises:
a voltage detector coupled to the input terminal of the voltage regulator circuit; and
an output terminal coupled to the voltage regulator circuit to control the level of the output voltage of the voltage regulator circuit.
8. The microphone array according to claim 7 , wherein the switched-mode power supply circuit is a buck converter circuit.
9. The microphone array according to claim 8 , wherein the buck converter circuit comprises:
an input terminal;
an output terminal;
a switch transistor coupled to the input terminal and having a control terminal controlled by the clock signal;
an inductor coupled in series with the switch transistor and coupled to the output terminal; and
a diode coupled to a node between the switch transistor and the inductor.
10. The microphone array according to claim 9 , wherein the clock signal is controlled to exhibit a high duty cycle when the level of the supply voltage is higher than a threshold, and to exhibit a low duty cycle when the level of the supply voltage is lower than a threshold.
11. The microphone array according to claim 1 , wherein the voltage regulator circuit is a low-dropout regulator.
12. The microphone array according to claim 11 , wherein the low-dropout regulator comprises:
an input terminal for a supply voltage;
an output terminal for an output voltage;
a transistor of which a controlled path is connected between the input and output terminals;
an amplifier having a terminal for a reference voltage and a terminal for a control voltage; and
a first and a second voltage divider coupled between the output terminal of the low-dropout regulator and the terminal for a control voltage of the amplifier, wherein the first and second voltage dividers are configured to be enabled alternately.
13. The microphone array according to claim 12 , wherein the first and second voltage dividers of the low-dropout regulator comprise a respective switch and the output of a voltage detector is coupled to the switches.
14. The microphone array according to claim 1 , further comprising a plurality of microphone circuits, each microphone circuit comprising a microphone transducer, an amplifier having an input terminal coupled to the microphone transducer and an output terminal for an audio signal, and a voltage regulator circuit, wherein the voltage regulator circuits of the at least one microphone circuit and of the plurality of microphone circuits are coupled to the output terminal for an output voltage of the switched-mode power supply circuit, and wherein the output terminals for an audio signal of the amplifiers of the at least one microphone circuit and of the plurality of microphone circuits are coupled to a summing node for the audio signals.