Display apparatus, projector, and control method

1. A power supply device comprising:

a power source device adapted to supply electric power to an external microphone via an audio signal line connected to a microphone jack, the power source device having a switching element;

a switch device adapted to switch power supply of the power source device between ON and OFF;

a voltage level detection device adapted to detect a voltage level of the audio signal line in a condition in which the power supply from the power source device is ON; and

a control device adapted to control the switch device in accordance with a type of the external microphone determined based on a detection result of the voltage level detection device,

wherein the control device controls the switching element so as to gradually raise a power supply voltage of the power source device prior to the voltage level detection device detecting the voltage level of the audio signal line.

2. The power supply device according to claim 1 , further comprising:

a connection detection device adapted to detect a state of connection between the microphone jack and the external microphone,

wherein the control device is further adapted to control the switch device to switch ON power supply from the power source device upon the connection detection device detecting that the external microphone is connected to the microphone jack.

3. The power supply device according to claim 1 , further comprising:

an integrator adapted to gradually raise the power supply voltage of the power source device.

4. An acoustic device provided with a microphone jack to which an external microphone is connected, comprising:

the power supply device according to claim 1 .

5. A projector comprising:

a light source device;

a light modulation device adapted to modulate a light beam, which is emitted from the light source device, in accordance with image information to form image light;

a projection optical device adapted to enlargedly project the image light; and

the acoustic device according to claim 4 .

6. A power supply method using a power supply device, comprising:

providing, to the power supply device, a power source device adapted to supply electric power to an external microphone via an audio signal line connected to a microphone jack, the power source device having a switching element, and a switch device adapted to switch power supply from the power source device between ON and OFF;

detecting a voltage level of the audio signal line in a condition in which the power supply from the power source device is ON; and

controlling the switch device in accordance with a type of the external microphone determined based on a detection result of the voltage level,

wherein the switching element is controlled so as to gradually raise a power supply voltage of the power source device prior to detecting the voltage level of the audio signal line.

7. The power supply device according to claim 1 , wherein the control device controls the switch device to switch OFF power supply from the power source device upon determining that the type of external microphone does not require power from the power source device to operate.

8. A display apparatus comprising:

an image display device adapted to form an optical image;

a microphone jack adapted to connect with an external microphone;

an OSD controller adapted to prepare OSD screen image data about the external microphone to supply to the image display device;

a power source device adapted to supply electric power to the external microphone via an audio signal line coupled to the microphone jack;

a switch device adapted to switch power supply of the power source device between an ON and an OFF state;

a voltage level detection device adapted to detect a voltage level of the audio signal line in a condition in which the power supply from the power source device is in the ON state so as to determine whether the microphone requires electric power from the power source device to operate or whether the microphone is operational without electric power from the power source device; and

a control device adapted to:

hold the power supply from the power source in the ON state when the voltage level detection device determines that the microphone requires electric power to operate;

switch the power supply from the power source to the OFF state when the voltage level detection device determines that the microphone is operational without electric power from the power source device.