JP2005124317A - Bus powered device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a bus powered device which can avoid a stop of an operation caused by an insufficient power of a drive power supplied from an external unit through a communication cable. <P>SOLUTION: The bus powered device includes a battery 16 which can supply a larger power than an upper limit value of a power capable of being supplied from the external unit via the communication cable 50, and a switch element 14 which is switched so that when a power consumption of a CPU 12, a memory 18 and a power load 20 is larger than a predetermined value set as a value of the upper limit value or less, the power supplied by the battery 16 is applied as a drive power by the CPU 12, and the power supplied from the external unit via the communication cable 50 is applied as the drive power when the power consumption is less than the predetermined value set as the value of the upper limit value or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a bus-powered device, and more particularly to a bus-powered device configured to be able to supply driving power from an external device to a power load by a communication cable.

  In recent years, based on interface standards that can supply power via communication cables such as USB (Universal Serial Bus) standards, IEEE (Institute of Electrical and Electronics Engineers) 1394 standards, etc., driving power from an external device to a power load by a communication cable A number of bus-powered devices configured to be able to be supplied have been commercialized. The bus powered device is sometimes called a bus powered device.

  By the way, when power is supplied to such a bus-powered device via a communication cable, the power consumption due to the power load of the bus-powered device is smaller than the above-mentioned maximum power. In this case, power consumption is increased, which is not preferable.

In order to solve this problem, Patent Document 1 discloses that a bus-powered transmitter connected to a communication line (corresponding to the communication cable) and supplied with power from the communication line outputs the bus-powered transmitter. A technique is disclosed in which the value of the DC output current is variable in at least two stages.
JP 2002-354714 A

  By the way, in the interface standard capable of supplying power via the communication cable as described above, an upper limit value of power that can be supplied by the communication cable (for example, 2.5 W in the USB standard) is determined.

  Therefore, when the power consumption due to the power load of the bus-powered device temporarily exceeds the upper limit value, there is a problem that the operation of the bus-powered device may stop due to power shortage. there were.

  For example, a digital camera is connected to a personal computer (hereinafter referred to as a PC) according to the USB standard via a communication cable, and an image captured by the digital camera is collected and used in real time by the PC. In an embodiment using a camera, the digital camera may perform an operation of extending the lens to a predetermined position after opening the lens shutter in response to a shooting start request from the PC. Is significantly larger than other operations, and power shortage may occur during the lens extension operation, and the operation may be stopped.

  Note that the technique disclosed in Patent Document 1 makes the DC output current variable within the range up to the upper limit value.

  The present invention has been made to solve the above-described problems, and provides a bus-powered device capable of avoiding an operation stop caused by power shortage of drive power supplied from an external device via a communication cable. For the purpose.

  In order to achieve the above object, the bus powered device according to claim 1 is a bus powered device configured to be able to supply driving power from an external device to a power load by a communication cable, and can be supplied by the communication cable. A battery capable of supplying a power larger than an upper limit value of power, and a switch means for switching to apply one of the power supplied by the communication cable and the power supplied by the battery as drive power to the power load; , When the power consumption of the power load is greater than a predetermined value that is less than or equal to the upper limit value, the switch means is controlled to apply the power supplied by the battery as drive power, and the power load consumption When the power is less than or equal to the predetermined value, the power supplied by the communication cable is applied as drive power. It comprises a control means for controlling the switch means.

  The bus-powered device according to claim 1 is configured such that driving power from an external device to an electric power load can be supplied by a communication cable, and a battery that can supply electric power larger than an upper limit value of electric power that can be supplied by the communication cable. Is provided. The external device includes any device capable of supplying power to the outside via a communication cable such as a PC, a PDA (Personal Digital Assistant), and a mobile phone. Further, the battery includes a rechargeable secondary battery in addition to a primary battery that cannot be charged.

  Here, the bus-powered device of the present invention includes switch means for switching so that either one of the power supplied by the communication cable and the power supplied by the battery is applied as driving power to the power load. The switch means is configured so that the power supplied by the battery is applied as drive power when the power consumption of the power load is greater than a predetermined value that is not more than the upper limit value by the control means. The switch means is controlled so that the power supplied by the communication cable is applied as the driving power when the power consumption of the power load is equal to or less than the predetermined value. The switch means includes semiconductor switches such as bipolar transistors and field effect transistors, electronic components such as relay switches, mechanical switches whose contacts can be electrically opened and closed, and the like.

  As described above, according to the bus powered device of the first aspect, the battery includes a battery that can supply power larger than the upper limit value of the power that can be supplied by the communication cable, and the power consumption of the power load is a value that is equal to or lower than the upper limit value. The power supplied by the battery is applied as the driving power when the power is larger than the predetermined value, and the power supplied by the communication cable is applied as the driving power when the power consumption of the power load is equal to or less than the predetermined value. Since the switching is performed, it is possible to avoid the operation stop caused by the power shortage of the driving power supplied from the external device via the communication cable.

  According to the present invention, as in the invention described in claim 2, the information processing apparatus further includes a storage unit that stores in advance information indicating a high power operation mode in which the power consumption of the power load exceeds the predetermined value. Controlling the switch means to apply the power supplied by the battery as drive power when the power load operation mode is the high power operation mode, and the power load operation mode is another operation mode. In this case, the switch means can be controlled so that the power supplied by the communication cable is applied as the driving power.

  Accordingly, the switch means can be switched without detecting the power consumption due to the power load, and the apparatus can be configured at low cost and in a small size without providing a circuit for detecting the power consumption. The storage means includes ROM (Read Only Memory), EEPROM (Electrically Erasable and Programmable ROM), flash EEPROM (Flash EEPROM) and other storage elements, smart media (SmartMedia®), xD picture card (xD -Picture Card), CompactFlash (CompactFlash), ATA (AT Attachment) card, micro drive, floppy disk, CD-R (Compact Disc-Recordable), CD-RW (Compact Disc-ReWritable), magneto-optical disk, etc. A portable recording medium is included.

  According to a third aspect of the present invention, as in the third aspect of the present invention, the control unit further includes a storage unit that stores in advance information indicating a normal power operation mode in which the power consumption of the power load is equal to or less than the predetermined value. Controls the switch means so that the power supplied by the communication cable is applied as drive power when the power load operation mode is the normal power operation mode, and the power load operation mode is other than The switch means may be controlled so that the power supplied by the battery is applied as the driving power when in the operation mode.

  Accordingly, the switch means can be switched without detecting the power consumption due to the power load, and the apparatus can be configured at low cost and in a small size without providing a circuit for detecting the power consumption. The storage means includes storage elements such as ROM, EEPROM, flash EEPROM, smart media, xD picture card, compact flash, ATA card, microdrive, floppy disk, CD-R, CD-RW, magneto-optical A portable recording medium such as a disk is included.

  According to a fourth aspect of the present invention, as in the fourth aspect of the invention, the control unit includes a detection unit that detects power consumption of the power load, and the power consumption detected by the detection unit is the predetermined value. The switch means is controlled so that the power supplied by the battery is applied as drive power when the power is larger, and is supplied by the communication cable when the power consumption detected by the detection means is less than or equal to the predetermined value. The switch means may be controlled so that power is applied as drive power.

  Thereby, switching of the switch means can be performed according to the actual power consumption by the power load, and the switching can be performed with high accuracy.

  Further, according to the present invention, as in the invention described in claim 5, the battery is a rechargeable secondary battery, and charging means for charging the secondary battery with surplus power supplied by the communication cable. Can be further provided.

  As a result, the battery according to the present invention can be appropriately charged, and the remaining capacity of the battery can be appropriately recovered.

  The bus powered device according to the present invention includes a battery that can supply power larger than the upper limit value of power that can be supplied by the communication cable, and the power consumption of the power load is larger than a predetermined value that is not more than the upper limit value. Since the power supplied by the battery is sometimes applied as the driving power, and the power supplied by the communication cable is applied as the driving power when the power consumption of the power load is not more than the predetermined value, the communication is switched. An effect is obtained that it is possible to avoid an operation stop caused by power shortage of drive power supplied from an external device via a cable.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings. Here, a case where a digital camera is applied as the bus powered device of the present invention will be described.

[First Embodiment]
First, the configuration of the bus-powered device 10A according to the present embodiment will be described with reference to FIG.

  As shown in the figure, the bus-powered device 10A according to the present embodiment includes a CPU (central processing unit) 12 that controls the operation of the entire bus-powered device 10A, two input terminals, and one output terminal. A switch element 14 that can be switched according to a control signal from the outside so as to connect one of the input terminals to the output terminal, a battery 16 configured as a secondary battery, a nonvolatile memory 18, And a power load 20 excluding the CPU 12 and the memory 18 in the bus-powered device 10A.

  In the present embodiment, a lithium ion battery is used as the battery 16 and a flash memory is used as the memory 18. In addition, since the bus-powered device 10A according to the present embodiment is a digital camera, the power load 20 includes a motor that drives a lens for forming a captured image, an image sensor, and the like.

  On the other hand, the bus-powered device 10A is equipped with a communication function based on a predetermined interface standard (USB standard in the present embodiment), and a connector (not shown) corresponding to the standard is provided outside the housing. . The bus-powered device 10A can be connected to an external device such as a PC, PDA, mobile phone, or the like corresponding to the standard via the connector and the communication cable 50 corresponding to the standard.

  Input pins to which control signals (D + signal and D− signal in this case) are input via the communication cable 50 of the connector (not shown) are connected to the CPU 12, and control signals from external devices are input to the CPU 12. The

  On the other hand, an input pin to which a power signal (here, a vbus signal) is input via the communication cable 50 of the connector (not shown) is connected to one input terminal of the switch element 14 and supplied from an external device. Power is applied to the input terminal. The other input terminal of the switch element 14 is connected to the battery 16, and the power supplied from the battery 16 is applied to the input terminal.

  The output terminal of the switch element 14 is connected to the power input terminals of the CPU 12, the memory 18, and the power load 20. The CPU 12 is connected to a control terminal for performing connection control in the switch element 14. Therefore, any one of the power supplied from the external device via the communication cable 50 and the power supplied from the battery 16 to the CPU 12, the memory 18, and the power load 20 is controlled by the CPU 12 by the switch element 14. In accordance with this, it is selectively supplied.

  On the other hand, the CPU 12 is interconnected to the memory 18 and the power load 20. The CPU 12 can access the memory 18 (read and write information), and the power load 20 is controlled by the CPU 12.

  In addition to various control programs, the memory 18 according to the present embodiment shows an operation mode in which the power consumption by the CPU 12, the memory 18 and the power load 20 exceeds a predetermined value (corresponding to the “high power operation mode” of the present invention). Information (hereinafter referred to as “high power operation mode information”) is stored in advance. In the present embodiment, as the predetermined value, an upper limit value (2.5 W here) of the supply power defined in the interface standard (here, USB standard) applied in the bus powered device 10A is used. Applicable.

  FIG. 2 shows an example of the high power operation mode information stored in the memory 18. As shown in the figure, in the present embodiment, information on the name of the high power operation mode and the maximum power consumption in the high power operation mode is stored as the high power operation mode information. Note that the maximum power consumption information is not necessarily required, and only information that can specify the high power operation mode may be stored.

  The battery 16 according to the present embodiment is applied with a battery that is larger than the upper limit value and that can supply the maximum power consumption in the bus powered device 10A.

  Next, with reference to FIG. 3, the operation of the bus-powered device 10A according to the present embodiment will be described. FIG. 3 is a flowchart showing a flow of processing of the power switching processing program executed when the operation mode shifts to another mode in the CPU 12 of the bus-powered device 10A. The program is stored in the memory 18 in advance. ing.

  In step 100 of the figure, the high power operation mode information is read from the memory 18, and in the next step 102, whether the operation mode after the transition is included in the high power operation mode indicated by the read high power operation mode information. By determining whether or not, it is determined whether or not the operation mode after the transition is a high power operation mode.

  If the determination in step 102 is negative, the process proceeds to step 104, where the switch element 14 is switched so that the power supplied from the external device via the communication cable 50 is output, and then this power switching process is performed. Exit the program.

  On the other hand, if the determination in step 102 is affirmative, the process proceeds to step 106, the switch element 14 is switched to output the power supplied from the battery 16, and the power switching processing program is terminated.

  With this power switching processing program, driving power is supplied from the battery 16 to the CPU 12, the memory 18 and the power load 20 when shifting to the high power operation mode, and the communication cable 50 from the external device when shifting to another operation mode. The driving power is supplied via the.

  The bus powered device 10A according to the present embodiment is operated by the driving power supplied according to the power consumption for each operation mode as described above, so that it is possible to avoid operation stop due to power shortage.

  As described above in detail, according to the bus powered device 10A according to the present embodiment, the battery 16 that can supply power larger than the upper limit value of power that can be supplied by the communication cable 50 is provided, and the CPU 12, the memory 18, and the power. When the power consumption of the load 20 is larger than a predetermined value that is not more than the above upper limit value, the power supplied by the battery 16 is applied as driving power, and when the power consumption is not more than the predetermined value, the communication cable 50 Since switching is performed so that the supplied power is applied as the driving power, it is possible to avoid an operation stop caused by a shortage of the driving power supplied from the external device via the communication cable 50.

  In addition, the bus powered device 10A according to the present embodiment includes the memory 18 that stores in advance information indicating a high power operation mode in which the power consumption of the CPU 12, the memory 18, and the power load 20 exceeds the predetermined value. When the operation mode of the load is the high power operation mode, the switch element 14 is controlled to apply the power supplied by the battery 16 as the driving power, and communication is performed when the operation mode of the power load is another operation mode. Since the switch element 14 is controlled so that the power supplied by the cable 50 is applied as the drive power, the switch element 14 can be switched without detecting the power consumption due to the power load. The apparatus can be configured at low cost and in a small size without providing a circuit for detection.

  In the present embodiment, high power operation mode information indicating an operation mode in which the power consumption of the power load exceeds a predetermined value is stored, and when the operation mode after the transition is the high power operation mode, the battery 16 However, the present invention is not limited to this. For example, normal power operation mode information indicating an operation mode in which the power consumption of the power load is a predetermined value or less is stored in the memory 18. In addition, when the operation mode after the transition is a mode other than the normal power operation mode, the mode can be switched to the power supply from the battery 16. Also in this case, the same effects as in the present embodiment can be obtained.

[Second Embodiment]
First, the configuration of the bus powered device 10B according to the second exemplary embodiment will be described with reference to FIG. Note that the same components in FIG. 1 as those in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and description thereof is omitted.

  As shown in the figure, in the bus powered device 10B according to the second embodiment, the switch switching control unit 22A is newly added, and the connection source of the control terminal of the switch element 14 is not the CPU 12. Only the switch switching control unit 22A is different from the bus powered device 10A according to the first embodiment.

  As shown in the figure, the switch switching control unit 22A includes a comparator 24 and a resistor 26. The output terminal of the switch element 14 is connected to the non-inverting input terminal of the comparator 24, and the battery 16 is connected to the inverting input terminal via the resistor 26. The output terminal of the comparator 24 is connected to the control terminal of the switch element 14.

  Here, the voltage value of the battery 16 is converted so that the resistance value of the resistor 26 becomes the voltage value at the output terminal of the switch element 14 when the power consumption by the CPU 12, the memory 18 and the power load 20 becomes a predetermined value. It is a value that can be done. In the present embodiment, as the predetermined value, the upper limit value (2.5 W here) of the supply power defined in the interface standard (here, USB standard) applied in the bus powered device 10B is used. Applicable.

  Next, the operation of the bus powered device 10B according to the present embodiment will be described.

  When the power consumption by the CPU 12, the memory 18 and the power load 20 is smaller than the predetermined value, the output voltage of the switch element 14 becomes lower than the voltage applied to the inverting input terminal of the comparator 24. Becomes low level. Thereby, the switch element 14 is switched so that electric power supplied from the external device via the communication cable 50 is output, and the electric power is supplied as driving power to each load.

  On the other hand, when the power consumption by the CPU 12, the memory 18, and the power load 20 is larger than the predetermined value, the output voltage of the switch element 14 becomes higher than the voltage applied to the inverting input terminal of the comparator 24. The output terminal becomes high level. Thereby, the switch element 14 is switched so that the power supplied from the battery 16 is output, and the power is supplied as driving power to each load.

  In the bus-powered device 10B according to the present embodiment, switching is performed according to the power consumption of the actual power load by switching the switch element 14 by the switch switching control unit 22A configured as hardware by an electronic circuit as described above. Therefore, the operation stop caused by the power shortage can be avoided.

  As described above in detail, the bus powered device 10B according to the present embodiment includes the battery 16 that can supply power larger than the upper limit value of power that can be supplied by the communication cable 50, and the CPU 12, the memory 18, and the power. When the power consumption of the load 20 is larger than a predetermined value that is not more than the above upper limit value, the power supplied by the battery 16 is applied as driving power, and when the power consumption is not more than the predetermined value, the communication cable 50 Since switching is performed so that the supplied power is applied as the driving power, it is possible to avoid an operation stop caused by a shortage of the driving power supplied from the external device via the communication cable 50.

  Further, the bus powered device 10B according to the present embodiment includes the comparator 24 that detects the power consumption of the CPU 12, the memory 18, and the power load 20, and the power consumption detected by the comparator 24 is the predetermined power. When the power consumption detected by the comparator 24 is less than or equal to a predetermined value, the switch element 14 is controlled so that the power supplied by the battery 16 is applied as the driving power when the power is larger than the value. Since the switch element 14 is controlled so that electric power is applied as drive power, the switch element 14 can be switched according to the actual power consumption by the power load, and the switching can be performed with high accuracy. .

[Third Embodiment]
First, the configuration of the bus-powered apparatus 10C according to the third embodiment will be described with reference to FIG. Note that the same components in FIG. 4 as those in FIG. 4 are denoted by the same reference numerals as those in FIG.

  As shown in the figure, in the bus powered device 10C according to the third embodiment, a switch switching control unit 22B is applied instead of the switch switching control unit 22A, and the control terminal of the switch element 14 Only the point that the connection source is the CPU 12 is different from the bus-powered apparatus 10B according to the second embodiment.

  As shown in the figure, the switch switching control unit 22B includes an analog / digital converter (hereinafter referred to as “A / D converter”) 28 in addition to the comparator 24 and the resistor 26. The output terminal of the comparator 24 is connected to the input terminal of the A / D converter 28, and the output terminal of the A / D converter 28 is connected to the CPU 12.

  Next, with reference to FIG. 6, the operation of the bus powered device 10C according to the present embodiment will be described. FIG. 6 is a flowchart showing the flow of processing of the power switching processing program executed every predetermined period (0.1 seconds in the present embodiment) in the CPU 12 of the bus powered device 10C. 18 is stored in advance.

  In step 200 of the figure, the digital value indicating the output level from the comparator 24 inputted from the A / D converter 28 is larger than a predetermined value which is a value corresponding to between the high level and the low level. Determine whether.

  And when it becomes negative determination in the said step 200, it transfers to step 202, and after switching the switch element 14 so that the electric power supplied via the communication cable 50 may be output, this electric power switching process Exit the program.

  On the other hand, if an affirmative determination is made in step 200, the process proceeds to step 204, the switch element 14 is switched to output the power supplied from the battery 16, and the power switching process program is terminated.

  According to this power switching processing program, the power consumed by the CPU 12, the memory 18, and the power load 20 is supplied by the interface standard (here, the USB standard) applied to the bus powered device 10C. If it is larger than the upper limit value, drive power is supplied from the battery 16, and in other cases, drive power is supplied from the external device via the communication cable 50.

  Since the bus-powered device 10C according to the present embodiment is operated by the driving power supplied according to the actual power consumption as described above, it is possible to avoid an operation stop due to power shortage.

  As described above in detail, according to the bus powered device 10C according to the present embodiment, the battery 16 that can supply power larger than the upper limit of power that can be supplied by the communication cable 50 is provided, and the CPU 12, the memory 18, and the power. When the power consumption of the load 20 is larger than a predetermined value that is not more than the above upper limit value, the power supplied by the battery 16 is applied as driving power, and when the power consumption is not more than the predetermined value, the communication cable 50 Since switching is performed so that the supplied power is applied as the driving power, it is possible to avoid an operation stop caused by a shortage of the driving power supplied from the external device via the communication cable 50.

  In addition, according to the bus-powered device 10C according to the present embodiment, the power consumption detected by the CPU 24, the comparator 24 that detects the power consumption of the memory 12, and the power load 20 is detected by the CPU 24. When the power consumption detected by the comparator 24 is less than or equal to the predetermined value, the switch element 14 is controlled so that the power supplied by the battery 16 is applied as the driving power when the power consumption is less than the predetermined value. Since the switch element 14 is controlled to apply the supplied power as the driving power, the switch element 14 can be switched according to the actual power consumption by the power load, and the switching is performed with high accuracy. be able to.

  In the present embodiment, the case where the switching element 14 is switched according to the comparison result by the comparator 24 has been described. However, the present invention is not limited to this, and for example, the comparator 24 is used. Instead, by connecting the input terminal of the A / D converter 28 to the output terminal of the switch element 14, the CPU 12 directly detects the voltage value of the output terminal of the switch element 14, and the switch element 14 has a voltage value corresponding to the voltage value. It can also be set as the form which switches. In this case, since the comparator 24 is not necessary, the cost of the bus-powered device can be reduced as compared with the present embodiment.

  In each of the above embodiments, the case where a rechargeable secondary battery is applied as the battery of the present invention has been described. However, the present invention is not limited to this, and for example, a primary battery that cannot be charged is applied. It can also be set as the form to do. Also in this case, the same effects as those of the above embodiments can be obtained.

[Fourth Embodiment]
First, the configuration of the bus-powered device 10D according to the fourth embodiment will be described with reference to FIG. Note that the same components in FIG. 1 as those in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and description thereof is omitted.

  As shown in the figure, the bus-powered device 10D according to the fourth embodiment includes one input terminal and two output terminals, and externally connects the input terminal to one of the output terminals. The bus-powered device according to the first embodiment is the only addition of the switch element 30 that can be switched according to the control signal and the charge control unit 32 that controls the charging operation for the battery 16. It is different from 10A.

  As shown in the figure, in the bus-powered device 10D, the output terminal of the switch element 14 is connected to the input terminal of the switch element 30, and one output terminal of the switch element 30 is connected to the power input terminal of the power load 20. The other output terminal of the switch element 30 is connected to the input terminal of the charge control unit 32. The output terminal of the charging control unit 32 is connected to the battery 16.

  The CPU 12 is connected to the control terminal of the switch element 30, and the connection state of the switch element 30 can be set by the CPU 12.

  Next, with reference to FIG. 8, the operation of the bus-powered device 10D according to the present embodiment will be described. FIG. 8 is a flowchart showing the flow of processing of the power switching processing program executed when the operation mode shifts to another mode in the CPU 12 of the bus-powered device 10D. The program is stored in the memory 18 in advance. ing.

  In step 300 of the figure, high-power operation mode information is read from the memory 18, and in the next step 302, the high-power operation mode indicated by the read high-power operation mode information includes the operation mode after the transition. By determining whether or not, it is determined whether or not the operation mode after the transition is a high power operation mode.

  If the determination in step 302 is negative, the process proceeds to step 304, and the switch element 14 is switched so that the power supplied from the external device via the communication cable 50 is output, and then the process proceeds to step 308. To do.

  In step 308, it is determined whether or not the bus powered device 10 </ b> D is recognized by the external device. If the determination is affirmative, the process proceeds to step 310 where the input terminal of the switch element 30 is connected to the power load 20. After switching so as to be connected to the output terminal, the power switching processing program is terminated.

  On the other hand, if a negative determination is made in step 308, the process proceeds to step 312 to switch the input terminal of the switch element 30 to be connected to the output terminal to which the charge control unit 32 is connected, and then switch the power. Terminate the processing program.

  In addition, when the electric power from an external device is supplied by the said step 312 in the charge control part 32, charge control to the battery 16 using the said electric power will be performed.

  On the other hand, if the determination in step 302 is affirmative, the process proceeds to step 306 where the switch element 14 is switched to output the power supplied from the battery 16 and the input terminal of the switch element 30 is connected to the power load 20. After switching so as to be connected to the output terminal, the power switching processing program is terminated.

  With this power switching processing program, driving power is supplied from the battery 16 to the CPU 12, the memory 18 and the power load 20 when shifting to the high power operation mode, and the communication cable 50 from the external device when shifting to another operation mode. The driving power is supplied via the.

  Since the bus-powered device 10D according to the present embodiment is operated by the driving power supplied according to the power consumption for each operation mode as described above, it is possible to avoid operation stop due to power shortage.

  Further, in the bus powered device 10D, when the power supplied from the external device is not recognized by the external device and there is surplus power, the battery 16 is charged with the surplus power. The remaining capacity can be recovered as appropriate.

  As described above in detail, the bus powered device 10D according to the present embodiment includes the battery 16 that can supply power larger than the upper limit value of power that can be supplied by the communication cable 50, the CPU 12, the memory 18, and the power. When the power consumption of the load 20 is larger than a predetermined value that is not more than the above upper limit value, the power supplied by the battery 16 is applied as driving power, and when the power consumption is not more than the predetermined value, the communication cable 50 Since switching is performed so that the supplied power is applied as the driving power, it is possible to avoid an operation stop caused by a shortage of the driving power supplied from the external device via the communication cable 50.

  Further, the bus powered device 10D according to the present embodiment includes the memory 18 that stores in advance information indicating a high power operation mode in which the power consumption of the CPU 12, the memory 18, and the power load 20 exceeds the predetermined value. When the operation mode of the load is the high power operation mode, the switch element 14 is controlled to apply the power supplied by the battery 16 as the driving power, and communication is performed when the operation mode of the power load is another operation mode. Since the switch element 14 is controlled so that the power supplied by the cable 50 is applied as the drive power, the switch element 14 can be switched without detecting the power consumption due to the power load. The apparatus can be configured at low cost and in a small size without providing a circuit for detection.

  Furthermore, according to the bus-powered device 10D according to the present embodiment, since the battery 16 is charged with surplus power supplied by the communication cable 50, the battery 16 can be appropriately charged. The remaining capacity of the battery 16 can be recovered as appropriate.

  In each of the above embodiments, the case where the threshold value (predetermined value) for switching the switch element 14 is the upper limit value of the supplied power in the applied interface standard has been described, but the present invention is not limited to this. Instead, it may be configured to have a value smaller than the upper limit value. In this case, the smaller the threshold value, the more reliably the operation stop due to power shortage can be avoided. However, the consumption of the battery 16 becomes severe and the continuous drive time of the bus powered device is shortened. It is preferable to set an appropriate value according to conditions and the like.

  Further, the flow of processing of the power switching processing program (see FIGS. 3, 6, and 8) described in each of the above embodiments is an example, and can be changed as appropriate without departing from the gist of the present invention. Needless to say.

  Furthermore, the configurations (see FIGS. 1, 4, 5, and 7) of the bus powered devices 10A to 10D described in the above embodiments are also examples, and are appropriately changed within the scope not departing from the gist of the present invention. It goes without saying that it is possible.

It is a block diagram which shows the structure of 10 A of bus-powered apparatuses which concern on 1st Embodiment. It is a schematic diagram which shows an example of high power operation mode information. It is a flowchart which shows the flow of a process of the electric power switching process program which concerns on 1st Embodiment. It is a block diagram which shows the structure of the bus-powered apparatus 10B which concerns on 2nd Embodiment. It is a block diagram which shows the structure of 10 C of bus powered apparatuses which concern on 3rd Embodiment. It is a flowchart which shows the flow of a process of the electric power switching process program which concerns on 3rd Embodiment. It is a block diagram which shows the structure of bus powered apparatus 10D which concerns on 4th Embodiment. It is a flowchart which shows the flow of a process of the electric power switching process program which concerns on 4th Embodiment.

Explanation of symbols

10A-10D Bus powered device 12 CPU (control means)
14 Switch element (switch means)
16 battery (secondary battery)
18 Memory (memory means)
20 Power load 22A, 22B Switch switching control unit (control means)
24 comparator (detection means)
32 Charging control unit (charging means)

Claims (5)

A bus-powered device configured to be able to supply driving power from an external device to a power load via a communication cable,
A battery capable of supplying power larger than the upper limit of power that can be supplied by the communication cable;
Switch means for switching to apply one of the power supplied by the communication cable and the power supplied by the battery as drive power to the power load;
When the power consumption of the power load is greater than a predetermined value that is less than or equal to the upper limit value, the switch means is controlled to apply the power supplied by the battery as drive power, and the power consumption of the power load Control means for controlling the switch means so as to apply the power supplied by the communication cable as the driving power when is less than or equal to the predetermined value;
A bus powered device. Further comprising storage means for previously storing information indicating a high power operation mode in which power consumption of the power load exceeds the predetermined value;
The control means controls the switch means to apply power supplied by the battery as drive power when the power load operation mode is the high power operation mode, and the power load operation mode is The bus-powered device according to claim 1, wherein the switch means is controlled so that the power supplied by the communication cable is applied as drive power when in another operation mode. A storage means for storing in advance information indicating a normal power operation mode in which power consumption of the power load is equal to or less than the predetermined value;
The control means controls the switch means to apply power supplied by the communication cable as drive power when the power load operation mode is the normal power operation mode, and the power load operation mode. The bus-powered device according to claim 1, wherein the switch means is controlled so that the power supplied by the battery is applied as drive power when is in another operation mode. The control means includes detection means for detecting power consumption of the power load, and applies power supplied by the battery as drive power when the power consumption detected by the detection means is greater than the predetermined value. The switch means is controlled as described above, and the switch means is controlled so that the power supplied by the communication cable is applied as drive power when the power consumption detected by the detection means is less than or equal to the predetermined value. The bus-powered device according to 1. The battery is a rechargeable secondary battery;
The bus-powered device according to claim 1, further comprising a charging unit that charges the secondary battery with surplus power supplied from the communication cable.

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