JP4771548B2 - Wireless communication terminal and transmission control program for extending life of secondary battery - Google Patents

Description

  The present invention relates to a wireless communication terminal and a transmission control program for extending the life of a secondary battery.

  In recent years, wireless communication terminals for machine-to-machine in a ubiquitous environment are becoming widespread. These terminals are carried by humans, are provided in a mobile body (car, pet, etc.), or are arranged at various locations, and can acquire various peripheral information and further transmit the peripheral information. By collecting such peripheral information in a specific server, it is possible to analyze the relationship between a wide range of position information and various peripheral information.

  Such a terminal is a terminal equipped with a peripheral information monitoring function and a communication module. For example, peripheral information (for example, peripheral environment information such as temperature and humidity, or peripheral image information captured by a camera) is automatically used. And the peripheral information is transmitted to the server via the base station. Further, such a terminal is usually portable and includes a secondary battery as a power source, and can be configured to use an external power source (AC power source) as necessary.

  In addition, many terminals have a self-power generation function. For example, a solar cell can be provided in the outer part of the casing of the terminal. During normal startup, the secondary battery is charged with the power output from the solar battery, and the power is supplied to the wireless communication function and other circuits.

  Such a terminal normally stores the electricity generated by the solar cell once in the secondary battery. Then, power is supplied from the secondary battery to the wireless communication function and other circuits. By adopting such a configuration, the wireless communication function can be driven only by the secondary battery even in a place where an external power source cannot be used or in the night when sunlight cannot be obtained.

Japanese Patent No. 3173580 JP 2007-020051 A JP 2005-190295 A JP 2003-249672 A JP-A-8-2223067 "Batteries in a Portable World (secondedition)," Isidor Buchmann, Cadex Electronics Inc. Masahiro Ichimura, et al., “Life characteristics of small lithium-ion batteries”, IEICE Technical Report, Electronic Communication Energy Technology, Vol.105, No.197, pp.19-23. Matsushita Electric Industrial, "Economy Mode (ECO) with a battery life about 1.5 times longer than before", [online], [Search July 4, 2007], Internet <URL: http: // panasonic. jp / pc / support / products / r4g / mobile.html>

  However, secondary batteries usually have a lifetime due to self-discharge and repeated use. Therefore, even when the solar battery is operating normally, if the secondary battery deteriorates quickly, the secondary battery must be replaced after all.

  Therefore, the present invention relates to a wireless communication terminal and transmission control capable of extending the life of a secondary battery (period until the secondary battery is replaced) as much as possible for a terminal having a self-power generation function and a secondary battery. The purpose is to provide a program.

According to the present invention, wireless communication has self-power generation means, a secondary battery that charges electricity output from the self-power generation means, and wireless communication means that communicates with a base station using the power of the secondary battery. On the terminal,
Peripheral information monitoring means for automatically monitoring peripheral information;
A transmission buffer for temporarily buffering the peripheral information;
A remaining capacity detecting means for detecting a remaining capacity of the secondary battery;
Based on the characteristics of the secondary battery, an optimum remaining capacity where the number of repeated charging / discharging is the largest, and an upper limit first threshold remaining capacity and a lower limit second threshold remaining capacity based on the allowable number of times of charging / discharging are specified in advance. And full charge capacity> first threshold remaining capacity > optimum remaining capacity > second threshold remaining capacity> remaining capacity 0, and the secondary battery is charged only up to the first threshold remaining capacity. Charging / discharging control means to control,
Only when the remaining capacity of the secondary battery is between the first threshold remaining capacity and the second threshold remaining capacity, the peripheral information stored in the transmission buffer is transmitted to the base station, the peripheral information in the case where the second threshold residual capacity or less have a transmission control means for controlling so as not to transmit,
The transmission control means divides the peripheral information into predetermined burst length units, and secures a predetermined waiting time as a transmission interval for each packet of the predetermined burst length .

  According to another embodiment of the wireless communication terminal of the present invention, the self-power generation means is preferably a solar cell that generates light by receiving light.

  According to another embodiment of the wireless communication terminal of the present invention, the remaining capacity detecting means preferably detects the remaining capacity of the secondary battery from a depth of discharge (DoD) or an output voltage.

According to the present invention,
Self-power generation means;
A secondary battery for charging electricity output from the self-power generation means;
Wireless communication means for communicating with the base station using the power of the secondary battery;
A transmission control program to function a computer mounted in a wireless communication terminal having,
Peripheral information monitoring means for automatically monitoring peripheral information;
A transmission buffer for temporarily buffering the peripheral information;
A remaining capacity detecting means for detecting a remaining capacity of the secondary battery;
Based on the characteristics of the secondary battery, an optimum remaining capacity where the number of repeated charging / discharging is the largest, and an upper limit first threshold remaining capacity and a lower limit second threshold remaining capacity based on the allowable number of times of charging / discharging are specified in advance. And full charge capacity> first threshold remaining capacity> optimum remaining capacity> second threshold remaining capacity> remaining capacity 0, and the secondary battery is charged only up to the first threshold remaining capacity. Charging / discharging control means to control,
Only when the remaining capacity of the secondary battery is between the first threshold remaining capacity and the second threshold remaining capacity, the peripheral information stored in the transmission buffer is transmitted to the base station, Transmission control means for controlling not to transmit the peripheral information when the threshold remaining capacity is 2 or less
Have
The transmission control means divides the peripheral information into predetermined burst length units, and ensures a predetermined waiting time as a transmission interval for each packet of the predetermined burst length.
The computer is made to function as described above .

  According to the wireless communication terminal and the transmission control program of the present invention, the remaining capacity of the secondary battery is always in a certain range (for example, 60% to full charge capacity with respect to the terminal having the self-power generation function and the secondary battery 20%), the life of the secondary battery can be extended as much as possible. As a result, the period until the secondary battery is replaced can be extended as much as possible, resulting in a reduction in maintenance work.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a system configuration diagram having a wireless communication terminal.

  According to FIG. 1, the wireless communication terminal 1 according to the present invention includes an antenna 12 and can communicate with the wireless base station 2 via a wireless link. The radio base station 2 is connected to the data collection server 3 via a network. Thereby, the radio communication terminal 1 can communicate with the data collection server 3 via the radio base station 2.

  In addition, the wireless communication terminal 1 includes a solar battery 10 as a self-power generation function and a secondary battery 11 that stores electricity output from the solar battery 10. The wireless communication terminal 1 can drive the wireless communication function using the power of the secondary battery. Therefore, it can be arranged even in a place where there is no external power source. Of course, an external power supply 14 may be provided.

  Furthermore, the wireless communication terminal 1 includes a peripheral information monitor unit 13 that can monitor peripheral information. The peripheral information includes, for example, peripheral environment information such as temperature, humidity, rainfall, and seismic intensity, or peripheral image information such as an image. For example, the wireless communication terminal 1 can transmit the peripheral information automatically monitored by the peripheral information monitoring unit 13 to the data collection server 3 via the wireless base station 2. As described above, the wireless communication terminal that has the self-power generation function and automatically transmits the data monitored by the peripheral information monitoring unit can be arranged in various places.

  Here, the characteristics of the secondary battery will be described.

  A terminal such as a mobile phone or a portable information terminal often uses a lithium ion battery as a secondary battery. A lithium ion battery has a large capacity per unit volume and has no memory effect at the time of charging, and thus is optimal as a secondary battery.

  It is known that a lithium ion battery significantly deteriorates its chargeable / dischargeable life when left in a fully charged state or an overdischarged state (empty charged state, remaining capacity 0) for a long time (for example, Non-Patent Document 1). 2 and 3). In particular, according to Non-Patent Document 3, when charging / discharging is repeated in the 100% charged state, the capacity of the secondary battery is reduced faster than in the case where charging / discharging is repeated in the 80% charged state (the service life is shortened). (Short).

  FIG. 2 is a schematic characteristic graph of the number of charge / discharge cycles versus remaining capacity in a lithium ion battery.

  The graph of FIG. 2 is a general characteristic graph for a lithium ion battery, and is not a result of measurement under specific conditions. Based on the characteristics of the secondary battery, the optimum remaining capacity that maximizes the number of repeated charging and discharging is specified. Generally, when a lithium ion battery is repeatedly charged and discharged in a charged state of about 40%, the number of times of charging and discharging is the largest. That is, it can be said that the lifetime is long. On the other hand, even if the charging rate is increased or decreased from the approximately 40% charged state, the number of times of charging / discharging decreases.

  In a terminal that is charged with a secondary battery by a solar battery as described in the prior art document, the secondary battery is always charged by the solar battery. Then, it is considered that the secondary battery is in a fully charged state in most time periods except for the time during which the wireless communication function is operating. That is, the lifetime (number of times of charging / discharging) of the secondary battery is deteriorated by repeatedly charging the secondary battery from the solar battery.

  Also, a wireless communication terminal arranged to monitor peripheral information usually has a solar cell in order to reduce maintenance work. Nevertheless, if the replacement work of the secondary battery that accumulates the electricity of the solar battery frequently occurs, the purpose of reducing the maintenance work cannot be achieved. According to the present invention, by performing transmission control, the life of the secondary battery is extended, and as a result, maintenance work is reduced.

  FIG. 3 is a functional configuration diagram of the wireless communication terminal according to the present invention.

  According to FIG. 3, the wireless communication terminal 1 externally includes a solar cell 10 as a self-power generation function, an antenna 12 as a wireless communication function, a peripheral information monitor unit 13, and an external power supply (AC power supply) 14. Have. According to the present invention, an external power source is not required, but the charging rate of the secondary battery is controlled even when an external power source is used.

  The wireless communication terminal 1 includes a secondary battery 11, a power supply control unit 15, a transmission buffer 16, a transmission control unit 17, a flash memory (F-ROM) 18, and a wireless communication function unit 19. Have In particular, the transmission control unit 17 is realized by executing a program that causes a computer installed in the wireless communication terminal 1 to function.

  The power supply control unit 15 further includes a remaining capacity detection unit 151. The power supply control unit 15 has a charge / discharge control function for the secondary battery while automatically switching between the solar battery 10 and the external power supply 14.

Here, the threshold value is defined for the secondary battery as follows.
[1] first threshold remaining capacity> optimum remaining capacity> second threshold remaining capacity (for example) 60% charge> 40% charge> 20% charge [2] full charge capacity> first threshold remaining capacity> second Threshold remaining capacity> remaining capacity 0
(For example) 100% charge> 60% charge> 20% charge> 0% charge At this time, the charge / discharge control function of the power supply control unit 15 is the first threshold remaining capacity (60% charge) at the maximum. It controls to charge only.

  Further, the remaining capacity detection unit 151 detects the remaining capacity of the secondary battery 11. The detected remaining capacity is output to the transmission control unit 17.

Here, the remaining capacity is the depth of discharge (DoD:
A value calculated from Depth of Discharge (battery capacity × (1−depth of discharge)), which is measured by a microcomputer provided in the remaining capacity detection unit 151. Regarding the relationship between the remaining capacity and the discharge depth, specifically, the remaining capacity is 100% when the discharge depth is 0%, and the remaining capacity is 0% when the discharge depth is 100%.

  If the discharge depth cannot be obtained directly, the output voltage of the secondary battery may be used. In that case, the remaining capacity is estimated from the output voltage by the microcomputer. Regarding the relationship between the remaining capacity and the discharge depth with respect to the output voltage, specifically, when the voltage is 4.2 V (= charge voltage), the discharge depth is 0% and the remaining capacity is 100%, and the voltage is 2.75 V (= end voltage). In this case, the discharge depth is 100% and the remaining capacity is 0%.

  The peripheral information monitored by the peripheral information monitor unit 13 is accumulated in the transmission buffer 16 and placed in a transmission waiting state. The output timing of the data stored in the transmission buffer 16 is controlled according to the control of the transmission control unit 17.

  The transmission control unit 17 transmits data only when the remaining capacity of the secondary battery is between the first threshold remaining capacity (for example, 60%) and the second threshold remaining capacity (for example, 20%), Control is performed so that data is not transmitted when the second threshold remaining capacity (for example, 20%) or less. Thereby, it is possible to maintain the remaining capacity so as to extend the life of the secondary battery as much as possible. Then, the data extracted from the transmission buffer 16 is output to the flash memory 18. At this time, it is divided into data of a predetermined burst unit length and transmitted.

  The flash memory 18 is used as a block device for the wireless communication function and operates as a file system. The wireless communication function unit 19 outputs radio waves from the antenna 12 by existing baseband processing, IF processing, and RF processing.

  FIG. 4 is a flowchart of processing of the transmission control unit in the present invention.

  The transmission control unit 17 starts the processing of this flowchart when data to be transmitted is generated, for example, when communication start is instructed from an application.

(S401) First, it is determined whether data is stored in the transmission buffer 16 or not. If the data to be transmitted is not accumulated, the process is terminated.

(S <b> 402) When data is accumulated in the transmission buffer 16, the remaining capacity is acquired from the remaining capacity detection unit 151 in the power supply control unit 15.

  Here, the power supply control unit 15 controls the remaining capacity of the secondary battery 11 to be equal to or less than the first threshold remaining capacity. Specifically, the power control unit 15 charges the secondary battery 11 so that when the remaining capacity reaches the first threshold remaining capacity, the power output from the solar battery 10 is discharged as it is. To do. Accordingly, the secondary battery 11 is not charged higher than the first threshold remaining capacity at the maximum. That is, the remaining capacity detected by the remaining capacity detector 151 does not become higher than the first threshold remaining capacity.

(S403) Next, the transmission control unit 17 determines whether or not the remaining capacity is equal to or greater than the second threshold remaining capacity. Here, if the remaining capacity is lower than the second threshold remaining capacity, the process is terminated without transmitting data.

  Accordingly, the secondary battery can be maintained in a state where a certain remaining capacity (first threshold remaining capacity to second threshold remaining capacity) exists. If data communication is executed until the remaining capacity of the secondary battery becomes 0, then the secondary battery is left in a state where the remaining capacity is 0, which leads to shortening of its life.

  For example, for a secondary battery that is a lithium ion battery, if it is recognized that maintaining a charged state of approximately 40% with respect to a fully charged state extends the life of the battery, the first threshold remaining capacity is set to 60%. It is also preferable to set the second threshold remaining capacity to 20%. In this case, the secondary battery 11 is always held between the 60% remaining capacity state at the time of full charge and the 20% remaining capacity state. Thereby, the lifetime of the secondary battery 11 can be extended.

(S404) On the other hand, if the remaining capacity is equal to or greater than the second threshold remaining capacity, data is transmitted. At this time, the data to be transmitted is divided into predetermined burst length units and transmitted.

(S405) After transmitting a packet having a predetermined burst length, a predetermined waiting time is secured as a transmission interval. By increasing the data transmission interval, the load on the secondary battery can be reduced, and the recovery effect of the secondary battery can be obtained. And it returns to S401 again.

  FIG. 5 is a circuit configuration diagram of the power supply controller in the present invention.

  According to the circuit configuration of FIG. 5, the battery connection control unit 153 can properly use the solar battery and the external power source. The external power supply will be used preferentially. The charge / discharge control unit 152 controls the remaining capacity of the secondary battery 11 to be equal to or less than a first threshold remaining capacity (for example, 60%).

  As described above in detail, according to the wireless communication terminal and the transmission control program of the present invention, the remaining capacity of the secondary battery is always within a certain range (full) for the terminal having the self-power generation function and the secondary battery. For example, the life of the secondary battery can be extended as much as possible. As a result, the period until the secondary battery is replaced can be extended as much as possible, resulting in a reduction in maintenance work.

  According to the various embodiments of the present invention described above, those skilled in the art can easily make various changes, modifications and omissions within the scope of the technical idea and the viewpoint of the present invention. The above description is merely an example, and is not intended to be restrictive. The invention is limited only as defined in the following claims and the equivalents thereto.

It is a system configuration diagram having a wireless communication terminal. It is a rough characteristic graph of the number of times of charge and discharge in a lithium ion battery versus remaining capacity. It is a function block diagram of the radio | wireless communication terminal in this invention. It is a flowchart of the process of the transmission control part in this invention. It is a circuit block diagram of the power supply control part in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wireless communication terminal 10 Solar cell, self-power generation function 11 Secondary battery, lithium ion battery 12 Antenna 13 Peripheral information monitor part 14 External power supply, AC power supply 15 Power supply control part 151 Remaining capacity detection part 152 Charge / discharge control part 153 Battery connection control Unit 16 Transmission buffer 17 Transmission control unit 18 Flash memory, F-ROM
19 Wireless Communication Function Unit 2 Wireless Base Station 3 Data Collection Server

Claims (4)

In a wireless communication terminal having a self-power generation means, a secondary battery that charges electricity output from the self-power generation means, and a wireless communication means that communicates with a base station using the power of the secondary battery,
Peripheral information monitoring means for automatically monitoring peripheral information;
A transmission buffer for temporarily buffering the peripheral information;
A remaining capacity detecting means for detecting a remaining capacity of the secondary battery;
Based on the characteristics of the secondary battery, an optimum remaining capacity where the number of repeated charging / discharging is the largest, and an upper limit first threshold remaining capacity and a lower limit second threshold remaining capacity based on the allowable number of times of charging / discharging are specified in advance. And full charge capacity> first threshold remaining capacity > optimum remaining capacity > second threshold remaining capacity> remaining capacity 0, and the secondary battery is charged only up to the first threshold remaining capacity. Charging / discharging control means to control,
Only when the remaining capacity of the secondary battery is between the first threshold remaining capacity and the second threshold remaining capacity, the peripheral information stored in the transmission buffer is transmitted to the base station, the peripheral information in the case where the second threshold residual capacity or less have a transmission control means for controlling so as not to transmit,
The radio communication terminal characterized in that the transmission control means divides the peripheral information into predetermined burst length units, and ensures a predetermined waiting time as a transmission interval for each packet of the predetermined burst length .   The wireless communication terminal according to claim 1, wherein the self-power generation means is a solar cell that generates light by receiving light.   3. The wireless communication terminal according to claim 1, wherein the remaining capacity detection unit detects a remaining capacity of the secondary battery from a depth of discharge (DoD) or an output voltage. 4. Self-power generation means;
A secondary battery for charging electricity output from the self-power generation means;
Wireless communication means for communicating with a base station using the power of the secondary battery;
A transmission control program to function a computer mounted in a wireless communication terminal having,
Peripheral information monitoring means for automatically monitoring peripheral information;
A transmission buffer for temporarily buffering the peripheral information;
A remaining capacity detecting means for detecting a remaining capacity of the secondary battery;
Based on the characteristics of the secondary battery, an optimum remaining capacity where the number of repeated charging / discharging is the largest, and an upper limit first threshold remaining capacity and a lower limit second threshold remaining capacity based on the allowable number of times of charging / discharging are specified in advance. And full charge capacity> first threshold remaining capacity> optimum remaining capacity> second threshold remaining capacity> remaining capacity 0, and the secondary battery is charged only up to the first threshold remaining capacity. Charging / discharging control means to control,
Only when the remaining capacity of the secondary battery is between the first threshold remaining capacity and the second threshold remaining capacity, the peripheral information stored in the transmission buffer is transmitted to the base station, Transmission control means for controlling not to transmit the peripheral information when the threshold remaining capacity is 2 or less;
Have
The transmission control means divides the peripheral information into predetermined burst length units, and ensures a predetermined waiting time as a transmission interval for each packet of the predetermined burst length.
A transmission control program for causing a computer to function as described above .

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