JP5479194B2 - Backup system, portable device - Google Patents

Description

  The present invention relates to a backup system that is provided in an electric device to which a battery can be attached and detached, and that includes a backup power source that supplies power instead of the battery when power supply from the battery is interrupted.

  In an electrical device in which a battery is detachable, a backup system including a backup power source that supplies power to a power supply target instead of the battery when power supply from the battery to a power supply target (such as an integrated circuit) is interrupted Some are provided. Hereinafter, a conventional backup system will be described. FIG. 1 is a diagram showing a conventional backup system. A backup system 300 shown in FIG. 1 is provided in an electric device, and is connected in parallel to the power supply unit 310, which is an integrated circuit or a volatile memory for controlling the electric device, and the power supply unit 310. A battery 320 and a backup power source 330 are connected.

  As shown in FIG. 1, the backup system 300 is provided with a mechanical switch SW <b> 1 for electrically disconnecting the backup power source 330 from the backup system 300 in the inspection process at the time of manufacturing the electrical equipment. This is because, in the inspection step, a stabilized power source is connected to the power receiver 310, and a test current is passed from the stabilized power source 310 to the power receiver 310 to measure the current value. As shown in FIG. 3, when the current flows up to the backup power source, accurate measurement becomes difficult. Therefore, the backup power source 330 is electrically disconnected from the backup system 300 by the mechanical switch SW1. That is, in the inspection process, as shown in FIG. 2, the mechanical switch SW1 is turned off to electrically disconnect the backup power source 330 from the backup system 300 so that no current flows through the backup power source 330. The switch SW1 is turned on to electrically connect the backup power supply 330 to the backup system 300 as shown in FIG.

  However, the backup system 300 including the mechanical switch SW1 has the following drawbacks. First, the mechanical switch SW1 has a drawback that it is more fragile than a semiconductor switch. Further, since the mechanical switch SW1 is manually operated, it is necessary to form an opening in the casing (cabinet) of the electrical device for projecting the mechanical switch SW1 to the outside of the casing. As a result, the strength of the casing is lowered, and it is difficult to take measures for waterproofing and dustproofing. In addition, the opening has a drawback that it becomes a design restriction or a restriction on the design. Further, since the mechanical switch SW1 is manually operated, an operation error that the backup power source 330 is connected during the inspection process or an operation error that the backup power source 330 is disconnected from the backup system 300 when used on the user side. There is a drawback that is likely to occur.

  On the other hand, as shown in FIG. 4, a semiconductor switch SW2 that operates according to a control signal generated based on a command from a CPU (Central Processing Unit) is provided, and the backup power source 430 is electrically connected from the system by the semiconductor switch SW2. The backup system 400 that is separated from each other does not have the above-described drawbacks.

JP-A-10-274792

  However, the backup system 400 in which the backup power source 430 is disconnected from the system by the semiconductor switch SW2 has the following problems. First, according to the backup system 400 as shown in FIG. 4, since the semiconductor switch SW2 is switched on and off based on a command from the CPU, a bug in the software or runaway causes a time other than during the inspection process (for example, a user) A malfunction occurs in which the backup power supply 430 is disconnected from the system suddenly. When such a malfunction occurs, the backup function does not work.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a backup system capable of electrically disconnecting a backup power source only during an inspection process without causing the malfunction. is there.

  In order to solve the above-described problem, the present invention provides a battery case in which a battery is mounted in a backup system provided in a portable device capable of communicating with a host device via a cable, and the battery case. A battery lid to be fitted; a power supply unit that receives power from the battery; a backup power source that supplies backup power to the power supply unit; and the battery and the backup power source in parallel to the power supply unit And a second mode in which the backup power supply is electrically disconnected from the power receiver and the battery while the battery is electrically connected to the power receiver. A state where the semiconductor switch and the battery cover are fitted in the battery case and from the host device via the cable. The first mode is entered when at least one of the states in which no power is supplied to the device, the battery cover is removed from the battery case, and the host device is connected to the portable device via the cable. And a control circuit for controlling the semiconductor switch so as to be in the second mode when power is supplied.

  According to the configuration of the present invention, the backup power supply is disconnected from the system when an operation that is not normally performed is performed on the user side in which the cable is connected after the battery cover is removed. Thus, the disadvantage that the backup power source is disconnected from the system on the user side can be suppressed. Therefore, by deliberately performing the above-mentioned operation that is not normally performed only during the inspection process, the backup power supply is turned on only during the inspection process without causing a malfunction that the backup power supply is disconnected from the system at times other than during the inspection process. There is an effect that it can be separated from the system.

  In the backup system of the present invention, the control circuit has a first input terminal and a second input terminal, and at least one of the first input terminal and the second input terminal inputs a first type signal. When the control signal indicating that the first mode is entered is output to the semiconductor switch, and when both the first input terminal and the second input terminal are inputting a second type signal, An AND circuit that outputs to the semiconductor switch a control signal indicating that a second mode is set, and when the battery cover is fitted in the battery case, a first type signal is input to the first input terminal, When the battery cover is removed from the battery case, a first signal supply unit that inputs a second type signal to the first input terminal, and power is not supplied from the host device to the portable device. A second signal supply unit that sometimes inputs a first type signal to the first input terminal and inputs a second type signal to the second input terminal when power is supplied from the host device to the portable device; The structure which has may be sufficient. According to this configuration, since the semiconductor switch can be controlled only by hardware without being controlled by software, the conventional problems (the occurrence of bugs and the runaway of software) that have been controlled by software do not occur. Has merit.

  In the backup system of the present invention, the cable may be a USB (Universal Serial Bus) cable. Furthermore, the portable device provided with the backup system of the present invention may be capable of communicating with the host device via the USB cable by being mounted on a cradle.

  The present invention has an effect of providing a backup system capable of electrically disconnecting a backup power supply only at the time of the inspection process without causing a malfunction that the backup power supply is disconnected from the system at a time other than the time of the inspection process.

It is a figure which shows the backup system which is the conventional backup system, and isolate | separates backup power supply with a mechanical switch. It is a figure for demonstrating the test process performed with respect to the backup system shown in FIG. It is a figure for demonstrating the test | inspection process performed with respect to the backup system which is not provided with a mechanical switch but cannot perform separation of a backup power supply. It is a figure which shows the backup system which is the conventional backup system and isolate | separates backup power supply with a semiconductor switch. It is a figure which shows the backup system of one Embodiment of this invention. (A) is a figure which shows the battery case of the portable information terminal provided with the backup system of one Embodiment of this invention. (B) is a figure which shows the state which removed the battery cover and opened the battery case. (C) is a figure which shows the state which mounted | wore with the battery cover and covered the battery case with the battery cover. (A) is a figure which shows the housing | casing of the portable information terminal provided with the backup system of one Embodiment of this invention, and the said cradle for portable information terminals. (B) is a figure which shows the state in which the said portable information terminal is inserted in the said cradle. (A) is a figure which shows the time of normal use of the backup system which concerns on one Embodiment of this invention. (B) is a figure which shows the time of battery replacement of the backup system which concerns on one Embodiment of this invention. (C) is a figure which shows the time of USB communication of the backup system which concerns on one Embodiment of this invention. (D) is a figure showing a time when a backup power source is disconnected in the backup system according to the embodiment of the present invention. It is a figure for demonstrating the test | inspection process performed with respect to the portable information terminal provided with the backup system which concerns on one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail. FIG. 5 is a diagram showing a backup system according to an embodiment of the present invention.

  The backup system 10 shown in FIG. 5 is provided in a portable information terminal (PDA: Personal Digital Assistant). The backup system 10 supplies power from the backup power supply 13 to the power receiver 11 instead of the battery 12 when the power supply from the battery 12 to the power receiver 11 is interrupted in the portable information terminal. .

  Note that, as shown in FIG. 7A, the portable information terminal includes a cradle 51 for performing USB (Universal Serial Bus) communication and charging as an external device. As shown in FIG. 7B, when the casing (cabinet) 50 of the portable information terminal is inserted into the cradle 51, the portable information terminal is connected to a commercial power supply via the AC adapter 53 and is attached to the portable information terminal. It is possible to charge the existing battery 12. Further, by inserting the casing 50 of the portable information terminal into the cradle 51 and connecting the cradle 51 and a PC (personal computer) 54 with a USB cable, USB communication can be performed between the portable information terminal and the PC 54. become.

  Next, the configuration of the backup system 10 will be described. As shown in FIG. 5, the backup system 10 includes a power supply unit 11, a battery 12, a backup power supply 13, a semiconductor switch SW <b> 3, a battery lid switch SW <b> 4, a pull-up resistor R, and an AND circuit 14. Have. As shown in FIG. 5, the AND circuit 14 has terminals IN1 and IN2 for inputting signals and a terminal OUT for outputting signals.

  The power supply section 11 is a computer that receives power supply from the battery 12 and performs information processing and control processing in the portable information terminal, and includes an integrated circuit and various memories. As shown in FIG. 5, a battery 12 and a backup power source 13 are connected in parallel to the power supply unit 11.

  The battery 12 is a battery that can be attached to and detached from the portable information terminal, and supplies power to the power supply unit 11. When the battery 12 is electrically connected to the backup system 10 and the portable information terminal is mounted on the cradle 51, the battery 12 can be charged by the AC adapter 53.

  The backup power source 13 supplies power to the power receiving unit 11 instead of the battery 12 when power supply from the battery 12 to the power receiving unit 11 is interrupted in the portable information terminal. Here, as the case where the power supply from the battery 12 to the power supply unit 11 is interrupted, the battery 12 is removed from the battery case of the portable information terminal (when the battery is replaced), or due to a drop impact or the like. There are times when it is temporarily away from the terminal.

  By providing the backup power supply 13 as described above, it is possible to prevent the data stored in the power supply unit 11 from being lost. For example, even if a situation occurs in which the battery 12 is temporarily separated from the battery case terminal due to a drop impact or the like while the user is operating the portable information terminal, the input information is lost until the situation occurs. Can be prevented.

  The semiconductor switch SW3 is connected in series with the backup power supply 13 between the power supply line connecting the negative terminal of the battery 12 and the power receiver 11 and the power line connecting the positive terminal of the battery 12 and the power receiver 11. Yes. That is, when the semiconductor switch SW3 is turned on, the backup power supply 13 is electrically connected to the power supply unit 11 and the battery 12, and when it is turned off, the backup power supply 13 is connected from the power supply unit 11 and the battery 12. It is designed to be electrically disconnected.

  Specifically, the negative terminal of the backup power source 13 is connected to the power line connecting the negative terminal of the battery 12 and the power receiver 11, and the power line connecting the positive terminal of the battery 12 and the power receiver 11 is connected. The plus terminal of the backup power supply 13 is connected via the semiconductor switch SW3. The semiconductor switch SW3 electrically connects the positive terminal of the backup power supply 13 to the power supply line connecting the positive terminal of the battery 12 and the power receiver 11 when turned on, and the positive of the battery 12 when turned off. The positive terminal of the backup power supply 13 is electrically disconnected from the power supply line connecting the terminal and the power receiver 11.

  The battery lid switch SW4 is a switch attached to the battery case 16 into which the battery 12 is inserted. Hereinafter, the battery case 16 and the battery lid switch SW4 will be described with reference to FIG.

  A portable information terminal including the backup system 10 of the present embodiment is provided with a battery case 16 and a battery lid 15 shown in FIG. When the battery 12 is fitted in the battery case 16, the battery 12 and the power supply unit 11 are electrically connected as shown in FIG. 5, and when the battery 12 is removed from the battery case 16, the battery 12 is electrically disconnected from the power receiver 11.

  As shown in FIGS. 5 and 6, a battery lid switch SW4 is attached to the battery case 16 of the present embodiment. The battery lid switch SW4 is turned off when the battery lid 15 is removed from the battery case 16 as shown in FIG. 6B, and the battery lid 15 is turned off as shown in FIG. 6C. When fitted in the case 16, it is pressed by a part of the battery cover 15 and turned on.

  As shown in FIGS. 5 and 6, the battery lid switch SW4 connects the terminal IN1 (input terminal) of the AND circuit 14 and GND in the on state, and disconnects the terminals IN1 and GND in the off state. It is supposed to be. Further, as shown in FIG. 5, a pull-up resistor R connected to the battery 12 is attached to a line connecting the battery lid switch SW4 and the terminal IN1. Thereby, when the battery lid switch SW4 is turned on, the input of the terminal IN1 becomes low. On the other hand, when the battery cover switch SW4 is turned off, the input of the terminal IN1 becomes high.

  The AND circuit 14 is a logic gate in which the terminal IN1 is connected to the battery lid switch SW4, the terminal IN2 is connected to VBUS, and the terminal OUT is connected to the control terminal of the semiconductor switch SW3. In response to this. VBUS is a part of the USB cable, and is a power source for supplying a voltage (5 V) from the host computer (PC 54 in the example of FIG. 7B) to the power-supplied supply unit 11 of the portable information terminal during USB communication. (Hereinafter, the voltage supplied by VBUS is referred to as VBUS voltage). That is, when the portable information terminal is inserted into the cradle 51 and the USB cable is connected between the PC 54 and the portable information terminal, the VBUS voltage is applied to the terminal IN2, and as a result, the input of the terminal IN2 is Become high. On the other hand, when the connection by the USB cable is not performed between the PC 54 and the portable information terminal, the voltage applied to the terminal IN2 is zero, and as a result, the input of the terminal IN2 becomes low.

  The AND circuit 14 outputs a control signal indicating high from the terminal OUT only when the input of the terminal IN1 is high and the input of the terminal IN2 is high, and from the terminal OUT otherwise. A control signal indicating low is output. The semiconductor switch SW3 is turned on when a low control signal is input from the AND circuit 14, and is turned off when a high control signal is input from the AND circuit 14.

  Next, the operation of the backup system 10 described above will be described with reference to FIG.

  First, the normal use when the portable information terminal is removed from the cradle 51 and the user activates and uses the portable information terminal will be described. In normal use, since the battery cover 15 is basically fitted in the battery case 16, the battery cover switch SW4 is on and the input of the terminal IN1 is low (L). Further, during normal use, since the portable information terminal is removed from the cradle 51, the VBUS voltage is not applied to VBUS, so the input at the terminal IN2 is low. Therefore, during normal use, as shown in FIG. 8A, the AND circuit 14 outputs a control signal indicating low, the semiconductor switch SW3 is turned on, and the backup power source 13 together with the battery 12 is a power supply unit. 11 is electrically connected.

  Here, the reason why the battery cover 15 is basically fitted into the battery case 16 during normal use will be described in detail below. The act of the user starting or using the portable information terminal with the battery 12 inserted into the battery case 16 and the battery cover 15 removed is usually prohibited in the operation manual. This is the first reason that there is a risk that the battery 12 may fall out during use of the portable information terminal, and the second reason that the removal of the battery 12 during activation of the portable information terminal involves an electrical risk. According to. Therefore, unless the user ignores the operation manual and removes the battery cover 15 to activate the portable information terminal, the battery cover switch SW4 is turned on during normal use.

  Next, the battery replacement will be described. At the time of battery replacement, the battery cover 15 is removed from the battery case 16 as shown in FIG. 6, and the battery cover switch SW4 is turned off. Therefore, when the battery is replaced, the input of the terminal IN1 is high (H). In addition, the fact that the battery has been replaced means that the portable information terminal is not inserted into the cradle 51 and the portable information terminal is not activated, so USB communication is not performed. Therefore, when the battery is replaced, since the VBUS voltage is not applied to VBUS, the input of the terminal IN2 is low. Therefore, at the time of battery replacement, as shown in FIG. 8B, the AND circuit 14 outputs a control signal indicating low, the semiconductor switch SW3 is turned on, and the backup power supply 13 together with the battery 12 is the power supply section 11. Is electrically connected.

  Next, the USB communication will be described. At the time of USB communication, the portable information terminal is inserted in the cradle 51, and the VBUS voltage is applied to VBUS, so the input of the terminal IN2 is high. During USB communication, the battery cover 15 is basically fitted in the battery case 16, so the battery cover switch SW4 is on and the input of the terminal IN1 is low. Therefore, during USB communication, as shown in FIG. 8C, the AND circuit 14 outputs a control signal indicating low, the semiconductor switch SW3 is turned on, and the backup power source 13 together with the battery 12 is the power-supplied supply unit 11. Is electrically connected.

  The reason why the battery cover 15 is basically fitted in the battery case 16 during USB communication will be described below. As in the second reason described above, removing the battery 12 while the portable information terminal is being started involves an electrical danger. Therefore, the act of starting or using the portable information terminal (including USB communication) by the user with the battery cover 15 removed is normally prohibited in the operation manual. Therefore, unless the user ignores the operation manual and removes the battery cover 15 to perform USB communication, the battery cover 15 is fitted into the battery case 16 during USB communication, and the battery cover switch SW4 is on.

  Next, a case will be described in which the battery cover 15 is removed and a state where the VBUS voltage is applied to VBUS, which is not normally performed (hereinafter referred to as “unusual state”), occurs exceptionally. In the non-normal state, since the battery cover 15 is removed from the battery case 16, the battery cover switch SW4 is off and the input of the terminal IN1 is high. In addition, the fact that the VBUS voltage is applied to VBUS means that the input of the terminal IN2 is high. Therefore, in the non-normal state, as shown in FIG. 8D, the AND circuit 14 outputs a control signal indicating high, the semiconductor switch SW3 is turned off, and the backup power source 13 is connected to the power supply unit 11. In addition, the battery 12 is electrically disconnected.

  Here, in the backup system 10 of this embodiment, the reason why the backup power supply 13 is electrically disconnected from the power-supplied supply unit 11 and the battery 12 when the non-normal state occurs will be described.

  The non-normal state occurs when USB communication is performed with the battery cover 15 removed, but this state is an exceptional case where the user ignores the operation manual as described above. Except for, there is almost no occurrence. Therefore, even if the backup power supply 13 is disconnected from the system when the abnormal state occurs, there is almost no inconvenience for the user. Therefore, in the present embodiment, by adopting the backup system 10 as shown in FIG. 8, the backup power supply 13 is electrically disconnected from the power supply unit 11 and the battery 12 when the non-normal state occurs. I have to.

  And in the inspection process at the time of manufacture of the portable information terminal equipped with the backup system 10, the test current is supplied to the power supply unit 11 to measure the current value. A normal state is generated and the backup power supply 13 is electrically disconnected from the backup system 10. Specifically, in the inspection process, as shown in FIG. 9, the VBUS voltage is applied to VBUS, the battery cover 15 is removed, and the battery cover switch SW4 is turned off, and then the power supply unit 11 is stabilized. A power source P is connected to supply a test current. Thereby, an accurate current value measurement can be performed in the inspection process.

  In other words, in this embodiment, the backup power supply 13 is disconnected from the system only when an operation that is not normally performed on the user side, “the VBUS voltage is applied to the VBUS after the battery cover 15 is removed” is detected. In addition, while suppressing the inconvenience that the backup power source 13 is disconnected from the system on the user side, the backup power source 13 is disconnected from the system by deliberately generating the abnormal state in the inspection process, and accurate current measurement is performed. It has been realized.

  As described above, the present embodiment is the backup system 10 provided in the portable information terminal that can communicate with the PC 54 (host device) 54 via the USB cable. The backup system 10 includes a battery case 16 in which the battery 12 is mounted, a battery lid 15 fitted in the battery case 16, a power supply unit 11 that receives power supply from the battery 12, and backup power to the power target supply unit 11. Is provided with a backup power supply 13, a semiconductor switch SW3, and an AND circuit (control circuit) 14. Here, the semiconductor switch SW3 includes a first mode in which the battery 12 and the backup power source 13 are connected in parallel to the power receiver 11 (see FIGS. 8A to 8C), and the battery 12 The second mode (see FIG. 8D) in which the backup power supply 13 is electrically disconnected from the power receiver 11 and the battery 12 while being electrically connected to the power receiver 11 is switched. The AND circuit 14 is in the first state when the battery cover 15 is fitted into the battery case 16 and when the power is not supplied from the PC 54 to the portable information terminal via the USB cable. The semiconductor switch SW3 is controlled to enter the second mode when the battery lid 15 is removed from the battery case 16 and power is supplied from the PC 54 to the portable information terminal via the USB cable. It is like that. As a result, the backup power supply 13 is disconnected from the system when an operation that is not normally performed on the user side of removing the battery cover 15 and connecting the USB cable is performed. In this case, the disadvantage that the backup power supply 13 is disconnected from the system can be suppressed. Therefore, by performing the above-mentioned operation that is not normally performed only during the inspection process, the backup power source 13 is disconnected only during the inspection process without causing a malfunction that the backup power supply 13 is disconnected from the system at times other than during the inspection process. Can be separated from the system.

  The AND circuit 14 includes a terminal IN1 (first input terminal) and a terminal IN2 (second input terminal), and at least one of the terminal IN1 and the terminal IN2 receives a low signal (first type signal). When the signal is input, a low signal (control signal) for connecting the battery 12 and the backup power source 13 in parallel to the power supply unit 11 is output to the semiconductor switch SW3, and both the terminal IN1 and the terminal IN2 are high. When a signal (second type signal) is input, a high signal (control signal) for electrically disconnecting the backup power supply 13 from the system is output to the semiconductor switch SW3. The backup system 10 of the present embodiment inputs a low signal to the terminal IN1 when the battery cover 15 is fitted in the battery case 16, and a high signal to the terminal IN2 when the battery cover 15 is detached from the battery case 16. The first signal supply unit (battery cover switch SW4, pull-up resistor R, GND, electrical ground 12) is input, and a low signal is output when power is not supplied from the host device to the portable information terminal via VBUS. A second signal supply unit (VBUS) for inputting a high signal to the terminal IN2 when power is supplied from the host device to the portable information terminal is input to the terminal IN2. According to such a configuration, since the semiconductor switch SW3 can be controlled only by hardware without being controlled by software, the conventional problems (the occurrence of bugs and the runaway of software) that have controlled the semiconductor switch SW3 by software occur. Has the advantage of not.

  Further, according to the configuration of the present embodiment, since the backup power supply 13 is disconnected from the system by the semiconductor switch SW3, an operation error like the conventional configuration (FIG. 1) in which the disconnection is performed by the mechanical switch can be suppressed. Operation reliability can be increased. In the conventional configuration of FIG. 1, when the mechanical switch is not turned on at the time of use, the user needs to turn on, but in the present embodiment, there is no such necessity. Further, in the present embodiment, it is not necessary for the engineer to operate the mechanical switch in the inspection process, and the number of processes can be reduced. Further, in the configuration of the present embodiment, the mechanical switch that is necessary in the conventional configuration of FIG.

  In the conventional configuration shown in FIG. 4, since the semiconductor switch SW2 is controlled by the CPU, it is necessary to energize the CPU in order to control the semiconductor switch SW2 during the inspection process. Therefore, the conventional configuration shown in FIG. 4 has a problem that it is difficult to accurately measure the standby current when the CPU is in a standby state (when the power is turned off). There is no problem.

  In the present embodiment, it is considered that the phenomenon that “the VBUS voltage is applied to VBUS after removing the battery cover 15” is not normally performed, and the backup power supply 13 is disconnected when the phenomenon occurs. However, if a configuration that prohibits the causal action of the above phenomenon is adopted, it is possible to further suppress the occurrence of the disadvantage that the backup power supply is disconnected when the user is used. For example, a sensor that detects that the battery cover 15 is removed is provided, and when the battery cover 15 is removed, a message that “the battery cover 15 is removed and will not start” is displayed on the display device. The configuration may be such that the OS is started after 15 is fitted and control (including USB communication) is enabled.

  The backup system 10 according to the present embodiment is applied not only to a portable information terminal but also to a portable device capable of USB communication with a host computer such as a cellular phone, a portable game device, an electronic dictionary, a portable music player, and an IC recorder. Is possible.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The backup system of the present invention can be applied to a portable device capable of USB communication with a host computer. Such portable devices include portable information terminals, portable game devices, electronic dictionaries, portable music players, IC recorders. Etc.

DESCRIPTION OF SYMBOLS 10 Backup system 11 Power supply part 12 Battery 13 Backup power supply 14 AND circuit (control circuit)
15 Battery cover 16 Battery case 50 Case 51 Cradle 54 PC (host device)
IN1 terminal (first input terminal)
IN2 terminal (second input terminal)
OUT terminal (output terminal)
SW3 Semiconductor switch SW4 Battery cover switch

Claims (4)

In a backup system provided in a portable device that can communicate with a host device via a cable,
A battery case to which the battery is mounted;
A battery lid fitted into the battery case;
A power receiving unit that receives power from the battery;
A backup power supply for supplying backup power to the power supply unit;
A first mode in which the battery and the backup power supply are connected in parallel to the power supply unit; and the battery is electrically connected to the power supply unit while the backup power supply is the power supply. And a semiconductor switch for switching between a second mode electrically disconnected from the battery and the battery;
The first mode is set when at least one of the state in which the battery cover is fitted in the battery case and the state in which power is not supplied from the host device to the portable device via the cable. A control circuit for controlling the semiconductor switch so as to be in the second mode when the battery cover is removed from the battery case and power is supplied from the host device to the portable device via the cable. And a backup system. The control circuit has a first input terminal and a second input terminal, and when at least one of the first input terminal and the second input terminal inputs a first type signal, the first mode is used. A control signal indicating that the second mode is entered when both the first input terminal and the second input terminal are inputting a second type signal. An AND circuit that outputs a signal to the semiconductor switch;
A first type signal is input to the first input terminal when the battery cover is fitted in the battery case, and a second type signal is input to the first input terminal when the battery cover is removed from the battery case. A first signal supply unit for inputting a signal;
When power is not supplied from the host device to the portable device, a first type signal is input to the first input terminal, and when power is supplied from the host device to the mobile device, a second type signal is input. The backup system according to claim 1, further comprising a second signal supply unit that inputs to the second input terminal.   The backup system according to claim 1, wherein the cable is a USB (Universal Serial Bus) cable. A portable device comprising the backup system according to claim 3, wherein the portable device is capable of communicating with the host device via the USB cable by being attached to a cradle. .

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