Electronic apparatus

An electronic apparatus includes solar cells, an accumulation portion that accumulates power generated by the solar cells, an electronic apparatus main body portion that is operated by using power accumulated in the accumulation portion, and an operation control circuit that performs control so that, in a case where a voltage of the accumulation portion increases, an operation of the electronic apparatus main body portion is started if the voltage of the accumulation portion exceeds a first threshold voltage, and, in a case where a voltage of the accumulation portion decreases, an operation of the electronic apparatus main body portion is stopped if the voltage of the accumulation portion is less than a second threshold voltage which is smaller than the first threshold voltage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2016-207510 filed Oct. 24, 2016.

BACKGROUND

Technical Field

The present invention relates to an electronic apparatus.

SUMMARY

According to an aspect of the invention, there is provided an electronic apparatus including solar cells; an accumulation portion that accumulates power generated by the solar cells; an electronic apparatus main body portion that is operated by using power accumulated in the accumulation portion; and an operation control circuit that performs control so that, in a case where a voltage of the accumulation portion increases, an operation of the electronic apparatus main body portion is started if the voltage of the accumulation portion exceeds a first threshold voltage, and, in a case where a voltage of the accumulation portion decreases, an operation of the electronic apparatus main body portion is stopped if the voltage of the accumulation portion is less than a second threshold voltage which is smaller than the first threshold voltage.

DETAILED DESCRIPTION

Next, a description will be made of an exemplary embodiment of the invention with reference to the drawings.

FIG. 1is a diagram illustrating a configuration of a location identification system including a beacon transmission apparatus10according to an exemplary embodiment of the invention.FIG. 1illustrates plural beacon transmission apparatuses10as beacon transmission apparatuses10ato10c.

The location identification system in the present exemplary embodiment is a system for specifying the current position of a mobile terminal apparatus20, and is, as illustrated inFIG. 1, formed of the beacon transmission apparatuses10ato10c, the portable mobile terminal apparatus20such as a smart phone, a tablet terminal apparatus, or a personal computer (hereinafter, abbreviated to a PC), and a server apparatus30.

FIG. 1illustrates only a single mobile terminal apparatus20, but, actually, plural mobile terminal apparatus20are included in the location identification system.

The invention is applicable to any apparatus as long as the mobile terminal apparatus20is connectable to the position information server apparatus30via a communication network.

Each of the beacon transmission apparatuses10ato10chas a function of transmitting a beacon signal including identifier (ID) information for specifying the beacon transmission apparatus via a wireless communication line such as WiFi. Each of the beacon transmission apparatuses10ato10cis provided at a location where a position of the mobile terminal apparatus20is desired to be specified. For example, the beacon transmission apparatuses10ato10care provided at different locations such as the inside of a conference room and a corridor, and normally transmit beacon signals including the identifiers.

In a case where the mobile terminal apparatus20comes close to the vicinities of the locations where the beacon transmission apparatuses10ato10care provided, the mobile terminal apparatus20receives beacon signals transmitted from the beacon transmission apparatuses10ato10c, and transmits information regarding the identifiers included in the received beacon signals and information regarding received radio wave intensities when the beacon signals are received, to the server apparatus30as signal information.

If the signal information is received from the mobile terminal apparatus20, the server apparatus30estimates a position of the mobile terminal apparatus20on the basis of the information regarding the identifiers or the information regarding the received radio wave intensities included in the signal information. Specifically, the server apparatus30stores respective installation positions of the beacon transmission apparatuses10ato10c, determines a beacon transmission apparatus around which the mobile terminal apparatus20is present on the basis of the information regarding the identifiers in the received signal information, and calculates a distance from the beacon transmission apparatus on the basis of the received radio wave intensity, so as to estimate the current position of the mobile terminal apparatus20.

The server apparatus30receives signal information based on the plural beacon transmission apparatuses from the mobile terminal apparatus20, and may thus estimate a more accurate position.

Next,FIG. 2illustrates an exterior of the beacon transmission apparatus10. The beacon transmission apparatus10is provided with solar cells31on a surface thereof, and is thus configured to be able to be operated without being connected to an external power source.

If connection to an AC power source is necessary in a case where the beacon transmission apparatuses10are provided at various locations such as an office, a conference room, and a corridor, there is a restriction in an installation location without a degree of freedom. If a power source is drawn to a location where the beacon transmission apparatus10is provided through an extension cable or the like, this is not realistic in a case where many beacon transmission apparatuses10are used since the time and effort for installation are considerable.

If the beacon transmission apparatus10is driven by using a battery or the like, there is a problem in that the battery is required to be replaced in a case where the battery runs out. Even if a rechargeable secondary battery is used, there is a problem in that the battery is required to be charged in a case where the battery runs out.

Thus, the beacon transmission apparatus10in the present exemplary embodiment is configured to be able to be provided at various locations without requiring connection to an external power source since the solar cells31such as solar panels are provided.

The beacon transmission apparatus10of the present exemplary embodiment may be operated only in a case where an office or the like is operating, and lighting is in an ON state.

With reference toFIG. 3, a description will be made of a schematic operation of the beacon transmission apparatus10of the present exemplary embodiment, for example, in a case where the beacon transmission apparatus10is used in an office.

In this office, for example, regular working time is 9:00 to 18:00. Thus, if an employee comes to the office at 9:00 in the morning, and thus lighting is turned on, the solar cells31start to generate power, and thus the beacon transmission apparatus10is activated. In the daytime in which a person is present in the office, the beacon transmission apparatus10continues to generate electric power by using light of the lighting which is in an ON state. If the employee leaves the office at 18:00 in the evening, and thus the lighting in the office is turned off, the beacon transmission apparatus10does not generate power, and, as a result, the beacon transmission apparatus10stops an operation.

A description will be made of a circuit configuration of the beacon transmission apparatus10of the present exemplary embodiment with reference toFIG. 4.

As illustrated inFIG. 4, the beacon transmission apparatus10of the present exemplary embodiment includes the solar cells (photoelectric cells)31which receive sunlight or lighting light, and convert light energy into electric energy so as to generate electric power, a capacitor (accumulation portion)32which accumulates power generated by the solar cells31, a voltage monitoring circuit33, a regulator34, and a main body portion35.

The main body portion35is an electronic apparatus main body portion which is operated by using electric power accumulated in the capacitor32. Specifically, the main body portion35is operated as a transmission portion which transmits a beacon signal including an identifier (identification information) of the beacon transmission apparatus10to the periphery thereof through wireless communication such as WiFi.

The regulator34is a constant voltage circuit which converts a voltage accumulated in the capacitor32into a voltage of 3 V which is an operation voltage of the main body portion35, and outputs the voltage. The regulator34is provided with an enable terminal (EN), performs a voltage conversion operation so as to perform an operation of supplying an output voltage to the main body portion35if the enable terminal transitions to a high level, and stops the voltage conversion operation so as not to supply a voltage to the main body portion35if the enable terminal transitions to a low level.

The capacitor (accumulation portion)32is a capacitor called a super capacitor (SCAP), and is, for example, an electric double layered capacitor having the capacitance of 0.02 farad (F).

In the capacitor32, power generated by the solar cells31is accumulated therein, and thus a voltage gradually increases. Since a rated value of a generated voltage of the solar cells31is 5 V, if the solar cells31start to generate power, a voltage of the capacitor32also gradually increases, and finally reaches 5 V after a sufficient time elapses.

The voltage monitoring circuit33is an operation control circuit which performs control so that an operation of the main body portion35is started if a voltage of the capacitor32exceeds 4 V (first threshold voltage) in a case where the voltage of the capacitor32increases, and an operation of the main body portion35is stopped if the voltage of the capacitor32is less 2 V (second threshold voltage) lower than 4 V in a case where the voltage of the capacitor32decreases.

Specifically, the voltage monitoring circuit33controls an operation of the main body portion35by outputting a control signal to the enable terminal (EN) of the regulator34so that the regulator34switches between operation and stoppage. In other words, if a control signal from the voltage monitoring circuit33transitions to a high level, the regulator34is operated to output a voltage to the main body portion35, and, if the control signal from the voltage monitoring circuit33transitions to a low level, the regulator34stops to be operated so as not to output a voltage to the main body portion35.

Next, a specific circuit configuration of the voltage monitoring circuit33will be described with reference toFIG. 5.

As illustrated inFIG. 5, the voltage monitoring circuit33is formed of voltage detection circuits41and42, and a D flip-flop (DFF) circuit43.

The voltage detection circuit41outputs a signal which transitions to a high level in a case where a voltage of the capacitor32exceeds 4 V, and transitions to a low level in a case where the voltage thereof is equal to or lower than 4 V. The voltage detection circuit42outputs a signal which transitions to a high level in a case where a voltage of the capacitor32exceeds 2 V, and transitions to a low level in a case where the voltage thereof is equal to or lower than 2 V.

The DFF circuit43is a logic circuit which detects rising edge of an output signal from the voltage detection circuit41so as to cause a control signal for controlling an operation of the main body portion35to transition to a high level, that is, an active state, and detects falling edge of an output signal from the voltage detection circuit42so as to cause the control signal for controlling an operation of the main body portion35to transition to a low level, that is, an inactive state.

Specifically, a voltage of the capacitor32is applied to an input terminal D of the DFF circuit43, an output signal from the voltage detection circuit41is input to a rising edge detection terminal CK, and an output signal from the voltage detection circuit42is input to a falling edge detection terminal CL. A high level signal is applied to a preset terminal PR of the DFF circuit43, and a logic output from an output terminal Q is output to the enable terminal EN of the regulator34as a control signal.

Next, a description will be made of an operation of the voltage monitoring circuit33with such a configuration with reference to a timing chart ofFIG. 6.

First, in an initial state, the output terminal Q of the DFF circuit43is at a low level. If a voltage of the capacitor32increases, and then a voltage value exceeds 2 V, an output voltage from the voltage detection circuit42first changes from a low level to a high level. If a voltage of the capacitor32further increases, and then a voltage value exceeds 4 V, an output voltage from the voltage detection circuit41changes from a low level to a high level.

Then, the DFF circuit43detects rising edge of the output signal from the voltage detection circuit41, and outputs a logic of the input terminal D to the output terminal Q. In other words, the logic of the output terminal Q of the DFF circuit43changes to a high level.

Since a logic state of the output terminal Q of the DFF circuit43is applied to the enable terminal of the regulator34as a control signal, the regulator34outputs an output voltage of 3 V to the main body portion35, and thus the main body portion35is activated. Thus, the beacon transmission apparatus10is also brought into an operation state.

Next, if a voltage of the capacitor32gradually decreases from 5 V, and then a voltage value becomes 4 V or less, an output voltage from the voltage detection circuit41first changes from a high level to a low level. However, a logic state of the output terminal Q of the DFF circuit43does not change.

If a voltage of the capacitor32further decreases, and then a voltage value becomes 2 V or less, an output voltage from the voltage detection circuit42changes from a high level to a low level. Then, the DFF circuit43detects falling edge of an output signal from the voltage detection circuit42, and outputs a logic of the input terminal D to the output terminal Q. Since the voltage value of the capacitor32is equal to or lower than 2 V at this time, the logic of the input terminal D is at a low level, and thus a logic of the output terminal Q of the DFF circuit43also changes to a low level.

Thus, the control signal which is output to the enable terminal of the regulator34changes to a low level so that an output voltage from the regulator34becomes 0 V, and thus the main body portion35is brought into an operation stoppage state. In other words, the beacon transmission apparatus10is also brought into an operation stoppage state.

In other words, the voltage monitoring circuit33is configured to perform a hysteresis (history effect) operation in which, in a case where a voltage of the capacitor32increases, the regulator34OS brought into an operation state so as to activate the main body portion35if a voltage value exceeds 4 V, and, in a case where a voltage of the capacitor32decreases, the regulator34is brought into a stoppage state so as to stop an operation of the main body portion35if a voltage value is 2 V or less.

Next, with reference toFIG. 7, a description will be made of a relationship between an input voltage and an output voltage of the regulator34.

The regulator34in the present exemplary embodiment is a low dropout voltage type regulator. Thus, as illustrated inFIG. 7, the regulator34is a circuit in which, if a voltage which is equal to or higher than an output voltage of 3 V by the dropout voltage is applied to the input terminal, the output voltage of 3 V is generated.

The regulator34is a circuit in which, in a case where an input voltage is equal to or lower than 3 V, a voltage which is equal to or lower than the input voltage by the dropout voltage is output.

Since the regulator34has such a circuit configuration, even if a voltage value of the capacitor32ranges from 2 V to 3 V, a voltage which is equal to or lower than 2 V to 3 V by the dropout voltage is applied to the main body portion35.

A rated voltage of the main body portion35is 3 V, but the main body portion35is configured to be operable if a voltage which is equal to or higher than 2 V is applied. Thus, in a case where light is not applied to the solar cells31, power generation is stopped, and thus power accumulated in the capacitor32is consumed so that a voltage decreases, the main body portion35is continuously in an operation state until a voltage of the capacitor32is equal to or lower than 2 V.

With this circuit configuration, the time at which the beacon transmission apparatus10is brought into a stoppage state is delayed, and thus an operation period of time increases compared with a case where an operation of the main body portion35is stopped at the time at which a voltage of the capacitor32is equal to or lower than 4 V.

Next, with reference toFIG. 8, a description will be made of a voltage change of the capacitor32after lighting of a location where the beacon transmission apparatus10of the present exemplary embodiment is provided is brought into an ON state.

InFIG. 8, a case is assumed in which lighting is brought into an ON state at 9:00 in the morning, and thus the solar cells31start to generate power. A case is assumed in which an amount of electric charge accumulated in the capacitor32at the time of 9:00 is substantially 0, and a voltage of the capacitor32is also substantially 0 V.

If the solar cells31continue to generate power in this state, an amount of electric charge accumulated in the capacitor32, and thus a voltage value gradually increases. At a time point T1, if a voltage value of the capacitor32exceeds 4 V, a logic state of the output terminal Q of the DFF circuit43changes from a low level to a high level. Then, the regulator34is also brought into an operation state, so as to supply an output of 3 V to the main body portion35, and thus the beacon transmission apparatus10starts to be activated.

FIG. 9illustrates a state of an operation of the beacon transmission apparatus10till the time point T1. As illustrated inFIG. 9, since a logic of a control signal from the voltage monitoring circuit33is at a low level (L) till the time point T1, the regulator34is in an OFF state, and thus an operation of the main body portion35is also stopped. Thus, till the time point T1at which a voltage of the capacitor32is 4 V from starting of power generation in the solar cells31, power generated by the solar cells31is continuously accumulated in the capacitor32, and thus a voltage of the capacitor32continuously increases.

Here, in a case where the main body portion35of the beacon transmission apparatus10is activated, larger power than during a steady operation is consumed. Thus, if the beacon transmission apparatus10starts to be activated at the time point T1, power consumed in the beacon transmission apparatus10is larger than power generated by the solar cells31, and thus a voltage of the capacitor32is temporarily reduced.

However, if the main body portion35of the beacon transmission apparatus10completes the activation operation and enters a steady state, consumed power is reduced so as to be smaller than generated power in the solar cells31. Thus, an amount of electric charge accumulated in the capacitor32increases, and thus a voltage value changes to an increase (time point T2).

FIG. 10illustrates a state of an operation of the beacon transmission apparatus10from the time point T1to the time point T2. As illustrated inFIG. 10, at the time point T1, a logic of a control signal from the voltage monitoring circuit33transitions to a high level (H) so that the regulator34is brought into an ON state, and thus the main body portion35performs an activation operation.

Thus, an amount of electric charge reduced from an amount of electric charge accumulated in the capacitor32is larger than an amount of electric charge accumulated in the capacitor32from the solar cells31. As a result, a voltage of the capacitor32is continuously reduced from the time point T1to the time point T2at which the activation operation of the main body portion35is completed.

Here, a difference voltage of 2 V between a detection voltage of 4 V of the voltage detection circuit41and a detection voltage of 2 V of the voltage detection circuit42is set to be higher than a drop voltage of the capacitor32caused by the voltage monitoring circuit33starting an operation of the main body portion35.

Thus, even if a voltage of the capacitor32temporarily drops due to an activation operation of the beacon transmission apparatus10, the voltage thereof is not equal to or lower than the detection voltage of 2 V of the voltage detection circuit42. If a voltage of the capacitor32temporarily drops due to an activation operation of the beacon transmission apparatus10, and the voltage thereof is equal to or lower than the detection voltage of 2 V of the voltage detection circuit42, an output voltage may not be obtained from the regulator34, and thus the main body portion35is continuously in an operation stoppage state.

In other words, in this case, the beacon transmission apparatus10repeats an activation operation, and a stoppage state due to a voltage drop, and thus may not transition to a steady state.

FIG. 11illustrates a state after a time point T2at which the beacon transmission apparatus10transitions to a steady state, and power consumption is less than in the activation state.

After the time point T2at which the activation operation is completed, since power consumption in the main body portion35is reduced, an amount of electric charge accumulated in the capacitor32from the solar cells31is larger than an amount of electric charge released from the capacitor32, and thus a voltage of the capacitor32increases. If a voltage of the capacitor32reaches 5 V at a time point T3, the voltage of the capacitor32is constant as 5 V.

Here, a description will be made of a method of setting a capacitance of the capacitor32. If a capacitance of the capacitor32is set to a great value, the above-described drop voltage when the main body portion35is activated may be reduced. However, in a case where a capacitance of the capacitor32is set to a great value, the time required for a voltage of the capacitor32to be 4 V from starting of a power generation operation of the solar cells31is also increased. In other words, the time required for the beacon transmission apparatus10to start an operation after lighting of a location where the beacon transmission apparatus10is provided is turned on is also increased.

Thus, a capacitance of the capacitor32is required to be set to an optimal value on the basis of power consumption during activation of the main body portion35or an amount of power generated by the solar cells31.

MODIFICATION EXAMPLES

In the above-described exemplary embodiment, a description has been made of a case where the invention is applied to the beacon transmission apparatus which is operated by using power generated by the solar cells, but the invention is not limited thereto, and the invention is applicable to other electronic apparatuses which are operated by using power generated by solar cells. For example, the invention is also applicable to electronic apparatuses such as a thermometer or a hygrometer which is operated by using power generated by solar cells.