Electronic device

Abstract

A USB electronic device with a power source loaded therein, which is connected to another USB electronic device via a USB connector, comprises a voltage detection unit that detects a voltage at an identification pin of the USB connector, a power supply control unit that controls connection/disconnection between a power supply pin of the USB connector and the power source based upon a change in voltage at the identification pin detected by the voltage detection unit and an allow/disallow control unit that executes control to allow/disallow detection of the voltage change at the identification pin.

1 . A USB electronic device with a power source loaded therein, which is connected to another USB electronic device via a USB connector, comprising:
 a voltage detection unit that detects a voltage at an identification pin of the USB connector;   a power supply control unit that controls connection/disconnection between a power supply pin of the USB connector and the power source based upon a change in voltage at the identification pin detected by the voltage detection unit; and   an allow/disallow control unit that executes control to allow/disallow detection of the voltage change at the identification pin.   
   
   
       2 . An electronic device according to  claim 1 , wherein:
 the allow/disallow control unit includes:   a pull-up circuit and a switch that connects/disconnects the pull-up circuit to/from the identification pin; and   the power supply control unit connects the pull-up circuit to the identification pin when the detection of the voltage change is allowed and disconnects the pull-up circuit from the identification pin when detection of the voltage change is disallowed by controlling changeover at the switch.   
   
   
       3 . An electronic device according to  claim 2 , further comprising:
 a setting operation unit with which a user selects a setting to allow/disallow the detection of a voltage change at the identification pin.   
   
   
       4 . A USB electronic device with a power source loaded therein, which is connected to another USB electronic device via a USB connector, comprising:
 a voltage detection unit that detects a voltage at an identification pin of the USB connector; and   power supply control unit that controls connection/disconnection between a power supply pin of the USB connector and the power source based upon a voltage change at the identification pin detected by the voltage detection unit, wherein: the power supply control unit includes:   a first switch disposed between the power supply pin and the power source, with which the power supply pin and the power source are connected with each other or disconnected from each other in response to a switching control signal; and   a second switch with which allow/disallow control is executed with regard to changeover at the first switch.   
   
   
       5 . An electronic device according to  claim 4 , wherein:
 when the changeover at the first switch is allowed via the second switch, the switching control signal is applied to the first switch via the second switch, whereas when the changeover at the first switch is disallowed via the second switch, the switching control signal is interrupted from the first switch by the second switch.   
   
   
       6 . An electronic device according to  claim 5 , wherein:
 the second switch is disposed between a switching control terminal of the first switch and the identification pin of the USB connector so as to connect/disconnect the switching control terminal of the first switch to/from the identification pin of the USB connector.   
   
   
       7 . An electronic device according to  claim 6 , wherein:
 the first switch is a semiconductor switching element and the switching control signal is applied to a switching control terminal of the semiconductor switching element, which is turned ON/OFF in correspondence to a voltage level at the identification pin.   
   
   
       8 . An electronic device according to  claim 7 , wherein:
 when the voltage level at the identification pin is low, the semiconductor switching element enters an ON state connecting the power supply pin to the power source.   
   
   
       9 . An electronic device according to  claim 4 , further comprising:
 an allow/disallow control unit that executes control to allow/disallow detection of a voltage change at the identification pin.   
   
   
       10 . An electronic device according to  claim 9 , wherein:
 the allow/disallow control unit includes:   a pull-up circuit; and   a switch that connects/disconnects the pull-up circuit to/from an identification pin; and   the switch connects the pull-up circuit to the identification pin when the detection of the voltage change is allowed and disconnects the pull-up circuit from the identification pin when detection of the voltage change is disallowed.   
   
   
       11 . An electronic device according to  claim 10 , wherein:
 when the changeover at the first switch is allowed by the second switch, the switching control signal is applied to the first switch via the second switch, whereas when the changeover at the first switch is disallowed by the second switch, the switching control signal is interrupted from the first switch by the second switch.   
   
   
       12 . An electronic device according to  claim 11 , wherein:
 the second switch is switched so as to connect/disconnect a switching control terminal of the first switch to/from the identification pin.   
   
   
       13 . An electronic device according to  claim 12 , wherein:
 the first switch is a semiconductor switching element and the second switch is disposed between a control terminal of the semiconductor switching element and the identification pin.   
   
   
       14 . An electronic device according to  claim 13 , wherein:
 the switching control signal corresponds to a voltage level at the identification pin and the semiconductor switching element is turned ON/OFF in correspondence to the voltage level at the identification pin.   
   
   
       15 . An electronic device according to  claim 14 , wherein:
 when the voltage level at the identification pin is low, the semiconductor switching element enters an ON state connecting the power supply pin to the power source.   
   
   
       16 . An electronic device according td  claim 9 , further comprising:
 a setting operation unit with which a user selects a setting to allow/disallow the detection of a voltage change at the identification pin.   
   
   
       17 . A USB electronic device that includes a USB device controller and a power source loaded therein, comprising:
 a USB connector at which an electronic device equipped with a USB host controller is connected;   a voltage detection unit that detects a voltage at an identification pin of the USB connector;   a first switch that connects/disconnects a power supply pin of the USB connector to/from the power source;   a detection unit that detects a voltage change at the identification pin detected via the voltage detection unit;   a second switch disposed between a switching control terminal of the first switch and the identification pin;   an allow/disallow control unit that executes control to allow/disallow detection of a voltage change by the detection unit; and   a switching control unit that executes switching control for the second switch so as to connect the identification pin to the switching control terminal of the first switch when the detection of the voltage change by the detection unit is allowed by the allow/disallow control unit and the voltage change is detected by the detection unit.   
   
   
       18 . An electronic device according to  claim 17 , further comprising:
 a setting operation unit with which a user selects a setting to allow/disallow the detection of a voltage change at the identification pin.   
   
   
       19 . An electronic device according to  claim 18 , wherein:
 the allow/disallow control unit includes:   a pull-up circuit and a switch that connects/disconnects the pull-up circuit to/from an identification pin; and   the switch connects the pull-up circuit to the identification pin when a setting for allowing detection of a voltage change is selected via the setting operation unit and disconnects the pull-up circuit from the identification pin when detection of the voltage change is disallowed.