Electric device and method of controlling the same

CROSS-REFERENCE TO RELATED APPLICATIONS

0001This application claims the benefit of Japanese Patent Application No. 2014-176156 filed Aug. 29, 2014 in the Japan Patent Office, and the disclosure of which is incorporated herein by reference.

BACKGROUND

0002The present disclosure relates to an electric device comprising a power supply circuit that supplies electric power to an external device via a connector.

0003For instance, an example of a rechargeable electric device disclosed in Japanese Unexamined Patent Application Publication No. 2013-070504 is configured to have a battery pack, which incorporates a rechargeable battery, detachably attached thereto, and receive electric power supply from the attached battery pack to light a light.

0004Aside from the rechargeable electric device mentioned above, electric devices of different kinds, such as a rechargeable electric power tool, a rechargeable vacuum cleaner, a rechargeable gardening tool (mowing machine, etc.), and a rechargeable radio, are also known as rechargeable electric devices that operate by receiving electric power from a battery.

SUMMARY

0005A rechargeable electric device of this kind may be configured so as to supply electric power to an external device (for example, mobile device such as a mobile phone or a smart phone) from a battery of the rechargeable electric device thereby to charge a rechargeable battery in the external device.

0006In this case, a rechargeable electric device may be provided with a connector, such as a socket to receive a USB (Universal Serial Bus) plug, for supplying electric power to the external device via a specified cable and may be configured to supply electric power to the external device via this connector.

0007However, it requires a constant operation of a power supply circuit that generates power supply voltage to supply electric power to the external device in the rechargeable electric device. Such operation of the power supply circuit may cause unnecessary increase in power consumption of the rechargeable electric device.

0008It is desirable that one aspect of the present disclosure can provide a technique that can reduce a standby power consumption of a power supply circuit to supply electric power to an external device via a connector in an electric device.

0009An electric device in one aspect of the present disclosure comprises a connector, a power supply unit, a connection-detection unit, and control unit. The connector is configured to couple to an external device. The power supply unit is configured to supply electric power to the external device via the connector. The connection-detection unit is configured to detect whether the external device is coupled to the connector.

0010The control unit is configured to control electric power supplied to the power supply unit from a battery so as to increase electric power supplied to the power supply unit when the connection-detection unit detects that the external device is coupled to the connector.

0011With such electric device, it is possible to reduce electric power supplied to the power supply unit thereby to reduce power consumption of the battery when no external device is coupled to the connector and thus no electric power supply is needed for the external device. In short, it is possible to achieve a power-saving on the electric device.

0012The connector may comprise a power supply terminal. The connection-detection unit may be configured to detect that the external device is coupled to the connector by a voltage change in the power supply terminal. The control unit may be configured to increase electric power supplied to the power supply unit when the connection-detection unit detects that the external device is coupled to the connector.

0013The power supply unit may be configured to supply electric power to the external device so as to keep the voltage of the power supply terminal constant when a value of a current that flows to the connector is within a specified range. The power supply unit may be configured to reduce the voltage of the power supply terminal and limit the value of the current that flows to the connector to a specified upper limit or below when the value of the current that flows to the connector reaches the upper limit.

0014In this case, it is possible to reduce electric power supplied from the power supply unit to the external device to a specified electric power or below and restrain or prevent the power supply unit from being overheated.

0015In addition, the control unit may be configured to either reduce or block electric power supplied to the power supply unit when the value of the current that flows to the connector is equal to or below a specified lower limit.

0016In this case, it is possible to reduce a standby current that flows to the power supply unit and achieve a further power-saving on the electric device by either stopping operation of the power supply unit or restricting the operation of the power supply unit when electric power supply is not necessary for the external device that is coupled to the connector.

0017The electric device may comprise a voltage detection unit that is configured to detect a value of a battery voltage of the battery. The control unit may be configured to perform a specified protective operation when the value of the battery voltage detected by the voltage detection unit is equal to or below an overdischarge threshold value and to set the overdischarge threshold value in accordance with a result of detection by the connection-detection unit.

0018The overdischarge threshold value may be set to vary between a case where the external device is coupled to the connector and a case where the external device is not coupled to the connector.

0019The control unit may be configured to notify information related to the battery voltage via a notification unit when the value of the battery voltage detected by the voltage detection unit is equal to or below the overdischarge threshold value. When this is the case, it is possible to encourage a user of the electric device to charge the battery when the battery voltage is decreased.

0020The control unit may be configured to set the overdischarge threshold value in accordance with a result of detection by the connection-detection unit such that the overdischarge threshold value while the external device is coupled to the connector is set smaller than the overdischarge threshold value while the external device is not coupled to the connector.

0021In the above case, it is possible to encourage the user to charge the battery in an early stage when the external device is not coupled to the connector, or use the electric device to supply electric power to the external device until the battery is empty (i.e., until the battery voltage reaches a lowest voltage) when the external device is coupled to the connector.

0022The control unit may be configured to continue the notification via the notification unit until at least one of a first condition and a second condition is satisfied after the value of the battery voltage detected by the voltage detection unit has become equal to or below the overdischarge threshold value: the first condition is a condition that the value of the battery voltage reaches a set value smaller than the overdischarge threshold value; and, the second condition is a condition that a specified time elapses.

0023The control unit may be configured to light a light emitting unit in accordance with a preset timing when the connection-detection unit detects that the external device is not coupled to the connector. In this case, it is possible for the user to easily identify a location of the electric device.

0024The electric device may comprise an oscillation/impact detection unit that is configured to detect at least either an oscillation or an impact applied to the electric device. The control unit may be configured to light the light emitting unit in accordance with a preset timing for a given length of time when either one of an oscillation or an impact is detected by the oscillation/impact detection unit.

0025If the electric device in the above case is a rechargeable light or radio that is possibly used in the event of a power outage or a natural disaster, the electric device can be easily found by lighting the light emitting unit automatically by an oscillation or an impact.

0026The electric device may further comprise a luminance detection unit that is configured to detect a value of luminance surrounding the electric device. The control unit may be configured to light the light emitting unit in accordance with a preset timing when the value of the surrounding luminance detected by the luminance detection unit is equal to or below a specified value.

0027If the surroundings of the electric device are dark (i.e. when it is not easy to find where the electric device is) in the above case, electric power consumption due to the light emission of the light emitting unit can be reduced by lighting the light emitting unit in accordance with the preset timing.

0028The electric device may comprise a grip portion that is configured to provide a grip for the user, and the battery. The connector may be disposed between the grip portion and the battery.

0029The electric device may further comprise a power-consumption unit that is configured to consume electric power of the battery and disposed on a side of the grip portion opposite to a side where the battery is provided.

0030Another aspect of the present disclosure is a method of controlling an electric device. The electric device comprises a connector that is configured to couple to an external device, and a power supply unit that is configured to supply electric power to the external device via the connector. The method comprises detecting whether the external device is coupled to the connector, and controlling electric power supplied to the power supply unit from a battery so as to increase electric power supplied to the power supply unit when it is detected that the external device is coupled to the connector.

0031As for an electric device comprising a power supply circuit to supply electric power to an external device via a connector, a standby power consumption of a power supply circuit can be reduced by using the above method.

BRIEF DESCRIPTION OF THE DRAWINGS

0032An exemplary embodiment will be described hereinafter by way of example with reference to the accompanying drawings, in which:

0033<figref idref="DRAWINGS">FIG. 1</figref> is a perspective view of an external appearance of a rechargeable lighting device according to an exemplary embodiment;

0034<figref idref="DRAWINGS">FIG. 2</figref> is a perspective view of a lighting device viewed from a direction opposite to that of <figref idref="DRAWINGS">FIG. 1</figref>;

0035<figref idref="DRAWINGS">FIG. 3</figref> is an explanatory drawing showing an inner structure of a lighting device;

0036<figref idref="DRAWINGS">FIG. 4</figref> is a block diagram showing a circuit configuration of a lighting device;

0037<figref idref="DRAWINGS">FIG. 5</figref> is a flowchart showing a control process performed by MCU in a lighting device;

0038<figref idref="DRAWINGS">FIG. 6</figref> is a flow chart showing a variation of a control process; and,

0039<figref idref="DRAWINGS">FIG. 7</figref> is a perspective view of an external appearance of a battery pack, to which an adapter of another exemplary embodiment is attached.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

0040As shown in <figref idref="DRAWINGS">FIG. 1</figref> to <figref idref="DRAWINGS">FIG. 3</figref>, a rechargeable lighting device (hereinafter, simply referred to as “lighting device”) <b>2</b> of the present exemplary embodiment is a lighting device that is configured to be operational for on-site work. The lighting device comprises a grip portion <b>4</b> that is formed into a rod-like shape to provide a grip for a user; a light unit <b>6</b> that is disposed on a first end-side of the grip portion <b>4</b> in the longitudinal direction (the upper side in <figref idref="DRAWINGS">FIG. 1</figref> to <figref idref="DRAWINGS">FIG. 3</figref>); and, a battery pack <b>8</b> that is detachably attached to a second end-side of the grip portion <b>4</b> in the longitudinal direction (the lower side in <figref idref="DRAWINGS">FIG. 1</figref> to <figref idref="DRAWINGS">FIG. 3</figref>), the second end-side being opposite the first end-side on the grip portion <b>4</b>.

0041The light unit <b>6</b> is disposed such that it can swing to the directions indicated with arrows in <figref idref="DRAWINGS">FIG. 1</figref> and <figref idref="DRAWINGS">FIG. 3</figref> in relation to the grip portion <b>4</b> and be folded towards the grip portion <b>4</b> via a connecting part <b>5</b> that is disposed on the first end-side of the grip portion <b>4</b>.

0042A first surface of the light unit <b>6</b> faces the grip portion <b>4</b> when the light unit <b>6</b> is folded towards the grip portion <b>4</b>. The first surface comprises a plurality of light-emitting elements (LED) <b>10</b> dispersed thereon, as shown in <figref idref="DRAWINGS">FIG. 4</figref>, such that light from each light-emitting element <b>10</b> is radiated to the surroundings.

0043A second surface of the light unit <b>6</b>, which is opposite the first surface, comprises a hook <b>7</b> stored therein to hook the lighting device <b>2</b> on a surrounding tree or structure.

0044Next, the battery pack <b>8</b> comprises at least a rechargeable battery <b>12</b> (see, <figref idref="DRAWINGS">FIG. 4</figref>), such as a lithium-ion battery, integrated therein. In addition, the battery pack <b>8</b> is detachably attached to an attachment portion <b>9</b> that is disposed on the second end-side of the grip portion <b>4</b>.

0045When the battery pack <b>8</b> is attached to the attachment portion <b>9</b>, the battery <b>12</b> is electrically coupled to a circuit board <b>30</b> (see, <figref idref="DRAWINGS">FIG. 3</figref>) inside the grip portion <b>4</b> via connection terminals <b>14</b> and <b>15</b> (see, <figref idref="DRAWINGS">FIG. 4</figref>) disposed in the attachment portion <b>9</b>.

0046As shown in <figref idref="DRAWINGS">FIG. 3</figref>, the grip portion <b>4</b> comprises a hollow synthetic resin case <b>16</b> that is formed into a shape to provide an easy grip for the user; the circuit board <b>30</b> and other components are placed inside the case <b>16</b>. The case <b>16</b> comprises a first wall that faces the light unit <b>6</b> when the light unit <b>6</b> is folded, and a second wall opposite the first wall. The circuit board <b>30</b> is arranged along the second wall.

0047Hereinafter, the first-wall side of the grip portion <b>4</b> is referred to as the front of the lighting device <b>2</b>; the second-wall side of the grip portion <b>4</b> is referred to as the back of the lighting device <b>2</b>.

0048An operation switch <b>18</b> is disposed on the second wall; the operation switch <b>18</b> is for switching the state of the lighting device <b>2</b> between ON and OFF by being pressed by the user. The operation switch <b>18</b> is electrically coupled to the circuit board <b>30</b>.

0049A USB (Universal Serial Bus) connector <b>20</b> is disposed at the back of the attachment portion <b>9</b>; the USB connector <b>20</b> is for supplying electric power to an external device (for example, a mobile phone or a smart phone) that can be supplied with electric power via a USB cable. In short, the USB connector <b>20</b> is disposed between the grip portion <b>4</b> and the battery pack <b>8</b>.

0050This USB connector <b>20</b> is a socket to receive a USB plug and has a terminal structure that is compliant with the USB standard. In other words, as shown in <figref idref="DRAWINGS">FIG. 4</figref>, the USB connector <b>20</b> comprises a positive power supply terminal (5V), a negative power supply terminal (GND), and a pair of communication terminals (D−, D+).

0051In the present exemplary embodiment, this USB connector <b>20</b> is used for supplying electric power to the external device; thus, the pair of communication terminals (D−, D+) is coupled to each other, and the positive power supply terminal (5V) and the negative power supply terminal (GND) disposed between the pair of communication terminals are used as the terminals for supplying electric power.

0052As shown in <figref idref="DRAWINGS">FIG. 2</figref> and <figref idref="DRAWINGS">FIG. 3</figref>, the attachment portion <b>9</b> comprises a cap <b>22</b> that protects the USB connector <b>20</b> when no external device is coupled to the USB connector <b>20</b>. The cap <b>22</b> comprises a cap body <b>23</b> that is inserted into the USB connector <b>20</b>, a belt part <b>24</b> for attaching the cap body <b>23</b> to the attachment portion <b>9</b>, and a protuberance <b>25</b> for allowing the user to handle the cap <b>22</b> with the user's fingertips when removing the cap body <b>23</b> from the USB connector <b>20</b>.

0053A notification LED <b>28</b> is disposed on the front side of the attachment portion <b>9</b>; the notification LED <b>28</b> is for notifying a condition of the lighting device <b>2</b>, for example, a decrease in remaining amount of electric power in the battery <b>12</b>.

0054The USB connector <b>20</b> and the notification LED <b>28</b> are electrically coupled to the circuit board <b>30</b> via wiring inside the case <b>16</b> (not shown).

0055As shown in <figref idref="DRAWINGS">FIG. 4</figref>, the circuit board <b>30</b> comprises a positive power-supply line <b>31</b> that is coupled to a positive electrode side of the battery <b>12</b> via the connection terminal <b>14</b>, and a negative power-supply line (i.e., a ground line) <b>32</b> that is coupled to a negative electrode side of the battery <b>12</b> via the connection terminal <b>15</b>.

0056The circuit board <b>30</b> comprises a constant-current circuit <b>36</b>, a voltage-conversion circuit <b>40</b>, a current-detection circuit <b>44</b>, an external-device-detection circuit <b>46</b>, a battery-voltage-measurement circuit <b>48</b>, a control circuit <b>50</b>, and a power-supply-voltage generation circuit <b>52</b>.

0057When a switching element <b>34</b> is in the ON state, the constant-current circuit <b>36</b> is electrically coupled to the positive power-supply line <b>31</b> and the negative power-supply line <b>32</b>, supplies a constant current to the light-emitting elements <b>10</b> in the light unit <b>6</b>, and turns on the light unit <b>6</b>.

0058When a switching element <b>38</b> is in the ON state, the voltage-conversion circuit <b>40</b> is electrically coupled to the positive power-supply line <b>31</b> and the negative power-supply line <b>32</b>, and supplies a specified power supply voltage (5V) to the positive power supply terminal of the USB connector <b>20</b>. More specifically, the voltage-conversion circuit <b>40</b> is configured to control an output voltage thereof to be constant if a value of a current that flows from the USB connector <b>20</b> to the external device is within an acceptable range. Further, the voltage-conversion circuit <b>40</b> is configured to reduce the output voltage to limit the value of the current that flows to the external device to the upper limit or below if the value of the current exceeds the upper limit. The voltage-conversion circuit <b>40</b> of the present exemplary embodiment may be configured as a DC-DC converter. A DC-DC converter can control an output voltage thereof to be constant if the value of the current that flows from the USB connector <b>20</b> to the external device is within an acceptable range. On the other hand, the DC-DC converter cannot control the output voltage to be constant if the value of the current that flows to the external device exceeds the upper limit, and thus, the output voltage is reduced to limit the value of the current to the upper limit or below.

0059A switching element <b>42</b> is disposed on an output path of the power supply voltage (5V) from the voltage-conversion circuit <b>40</b> to the USB connector <b>20</b>. This is to prevent or to reduce inflow of a current to the voltage-conversion circuit <b>40</b> from the external device that is coupled to the USB connector <b>20</b> or from the external-device-detection circuit <b>46</b> when the switching element <b>38</b> is in the OFF state and the voltage-conversion circuit <b>40</b> stops its operation.

0060Thus, the state of the switching element <b>42</b> is switched between ON and OFF in conjunction with the switching element <b>38</b> by the control circuit <b>50</b>, which will be mentioned later. Additionally, each of the switching elements <b>34</b>, <b>38</b>, and <b>42</b> is configured to switch its state between ON and OFF in accordance with a command from the control circuit <b>50</b>. In the present exemplary embodiment, each of the switching elements <b>34</b>, <b>38</b>, and <b>42</b> may be a semiconductor element such as FET (Field Effect Transistor).

0061Next, the ground line <b>32</b> is electrically coupled to the negative power supply terminal (GND) of the USB connector <b>20</b>. The current-detection circuit <b>44</b> is disposed on the ground line <b>32</b> and detects a value of a current that flows through the ground line <b>32</b>, in other words, a value of a current that is supplied from the battery <b>12</b> to the external device coupled to the USB connector <b>20</b>.

0062When the switching element <b>42</b> is in an OFF state, the external-device-detection circuit <b>46</b> detects that the external device is coupled to the USB connector <b>20</b> from a voltage change in the positive power supply terminal of the USB connector <b>20</b>.

0063The battery-voltage-measurement circuit <b>48</b> is electrically coupled to the positive power-supply line <b>31</b> and the negative power-supply line <b>32</b> and measures a value of an output voltage (battery voltage) of the battery <b>12</b> that is electrically coupled to the connection terminals <b>14</b> and <b>15</b>.

0064Detection signals from the current-detection circuit <b>44</b>, the external-device-detection circuit <b>46</b>, and the battery-voltage-measurement circuit <b>48</b>, as well as an input signal from the operation switch <b>18</b> are inputted into the control circuit <b>50</b>.

0065The control circuit <b>50</b> lights the light unit <b>6</b> and supplies electric power to the external device based on the inputted signals from the individual parts mentioned above. The control circuit <b>50</b> of the present exemplary embodiment is configured as an MCU (Micro Control Unit). The MCU may be a microcomputer; a combination of various separate electronic components; an ASIC (Application Specified Integrated Circuit); a programmable logic device, such as a FPGA (Field Programmable Gate Array); or a combination of these.

0066The power-supply-voltage generation circuit <b>52</b> supplies a power supply voltage (direct current constant voltage) Vcc for operation to the control circuit <b>50</b> and the external-device-detection circuit <b>46</b>. More specifically, the power-supply-voltage generation circuit <b>52</b> generates the power supply voltage Vcc from electric power supplied from the battery <b>12</b> via the positive power-supply line <b>31</b> and the negative power-supply line <b>32</b>.

0067Next, a control process executed by the control circuit <b>50</b> will be explained referring to the flowchart of <figref idref="DRAWINGS">FIG. 5</figref>.

0068The control process shown in <figref idref="DRAWINGS">FIG. 5</figref> is a process that is executed as one of main routines when the control circuit <b>50</b> is in operation as the power supply voltage Vcc is supplied from the power-supply-voltage generation circuit <b>52</b>.

0069In this control process, it is first determined in S<b>110</b> (S stands for a step) whether the external device is coupled to the USB connector <b>20</b> based on a detection signal from the external-device-detection circuit <b>46</b>. If the external device is coupled to the USB connector <b>20</b>, the process then proceeds to S<b>120</b>; if no external device is coupled to the USB connector <b>20</b>, the process then proceeds to S<b>190</b>.

0070In S<b>120</b>, it is determined whether the value of the battery voltage detected by the battery-voltage-measurement circuit <b>48</b> is less than a preset threshold value K<b>1</b>. The threshold value K<b>1</b> is a threshold value for determining an overdischarge while the external device is coupled to the USB connector <b>20</b>, and is used for determining whether to encourage the user to charge the battery <b>12</b> by lighting the notification LED <b>28</b>.

0071If it is determined in S<b>120</b> that the value of the battery voltage is less than the threshold value K<b>1</b>, the process then proceeds to S<b>140</b> to turn ON the notification LED <b>28</b> (light is on); if it is determined in S<b>120</b> that the value of the battery voltage is equal to or above the threshold value K<b>1</b>, the notification LED <b>28</b> is then turned OFF (light is off) in S<b>140</b>.

0072Next, it is determined in S<b>150</b> whether the value of the battery voltage is less than a preset threshold value K<b>2</b>. The threshold value K<b>2</b> is a threshold value for determining, based on the value of the battery voltage, whether a remaining amount of electric power charged in the battery <b>12</b> is equal to or more than the electric power practicable to supply electric power to the external device. The threshold value K<b>2</b> is set greater than the threshold value K<b>1</b> in the present exemplary embodiment.

0073If it is determined in S<b>150</b> that the value of the battery voltage is equal to or above the threshold value K<b>2</b>, the process proceeds to S<b>160</b> to turn ON the switching elements <b>38</b> and <b>42</b>. As a consequence, a current conduction to the voltage-conversion circuit <b>40</b> begins, and a power supply voltage that is generated by the current conduction to the voltage-conversion circuit <b>40</b> is outputted from the USB connector <b>20</b> to the external device. In other words, in S<b>160</b>, a power source of the external device that is coupled to the USB connector <b>20</b> is turned ON and electric power is supplied to the external device.

0074Next, it is determined in S<b>170</b>, based on a detection signal from the current-detection circuit <b>44</b>, whether a current is flowing to the external device via the power supply terminal of the USB connector, in other words, whether the external device is in operation. In S<b>170</b>, it may be determined whether the value of the current that flows to the external device is equal to or below a specified lower limit.

0075If it is determined in S<b>170</b> that the current is flowing to the external device (or, that the value of the current flowing to the external device is greater than the lower limit), the process then proceeds to S<b>120</b>; if it is determined that no current is flowing to the external device (or, that the value of the current flowing to the external device is equal to or below the lower limit), the process then proceeds to S<b>180</b>. The process also proceeds to S<b>180</b> if it is determined in S<b>150</b> that the value of the battery voltage is less than the threshold value K<b>2</b>.

0076In S<b>180</b>, by turning OFF the switching elements <b>38</b> and <b>42</b>, the current conduction to the voltage-conversion circuit <b>40</b> is stopped and electric power supply to the external device is blocked. In other words, electric power supply to the external device is blocked by turning OFF the power source of the external device coupled to the USB connector <b>20</b>. After turning OFF the power source of the external device in S<b>180</b>, the process proceeds to S<b>110</b>. In S<b>180</b>, a switching frequency of the voltage-conversion circuit <b>40</b> that is configured as a DC-DC converter may be reduced.

0077Next, it is determined in S<b>190</b> whether the value of the battery voltage is less than a preset threshold value K<b>3</b>; S<b>190</b> is executed when it is determined in S<b>110</b> that no external device is coupled to the USB connector <b>20</b>.

0078The threshold value K<b>3</b> is a threshold value for determining an overdischarge while no external device is coupled to the USB connector <b>20</b> and is set greater than the threshold value while the external device is coupled to the USB connector <b>20</b> (i.e., the threshold value K<b>1</b>). The reason for this is because it is not necessary to operate the voltage-conversion circuit <b>40</b> to supply electric power to the external device.

0079If it is determined in S<b>190</b> that the value of the battery voltage is equal to or above the threshold value K<b>3</b>, the notification LED <b>28</b> is turned OFF (light is off) in S<b>220</b>, and the process proceeds to S<b>110</b>.

0080On the other hand, if it is determined in S<b>190</b> that the value of the battery voltage is less than the threshold value K<b>3</b>, the process proceeds to S<b>200</b> to determine whether the value of the battery voltage is less than a threshold value K<b>4</b>, which is smaller than the threshold values K<b>1</b> to K<b>3</b>.

0081If it is determined in S<b>200</b> that the value of the battery voltage is equal to or above the threshold value K<b>4</b>, the notification LED <b>28</b> is turned ON (light is on) in S<b>230</b>, and then the process proceeds to S<b>110</b>.

0082If it is determined in S<b>200</b> that the value of the battery voltage is less than the threshold value K<b>4</b>, the notification LED <b>28</b> is turned OFF (light is off) in S<b>210</b>, and then the control process is ended.

0083The reason for this is because the threshold value K<b>4</b> is the lowest overdischarge threshold value of all the threshold values K<b>1</b> to K<b>4</b>, and the battery <b>12</b> will be overdischarged and deteriorated if the battery <b>12</b> is kept discharged for lighting the notification LED <b>28</b> and for other purposes.

0084As mentioned hereinbefore, the control circuit <b>50</b> makes the voltage-conversion circuit <b>40</b> operate when the external device is coupled to the USB connector <b>20</b> in the lighting device <b>2</b> of the present exemplary embodiment.

0085When a current does not flow from the USB connector <b>20</b> to the external device and the external device stops its operation, the control circuit <b>50</b> stops the operation of the voltage-conversion circuit <b>40</b> and maintains stopping of the operation of the voltage-conversion circuit <b>40</b> until the external device is coupled to the USB connector <b>20</b>.

0086Thus, according to the present exemplary embodiment, when no external device is coupled to the USB connector <b>20</b> and it is not necessary to supply electric power to the external device, a standby current generated from the operation of the voltage-conversion circuit <b>40</b> can be made substantially zero, and the lighting device <b>2</b> can be made power-saving.

0087As for the voltage-conversion circuit <b>40</b> that is configured as a DC-DC converter, in particular, its consumed power at the time of operation increases by switching of a semiconductor element for voltage conversion included in the voltage-conversion circuit <b>40</b>; nevertheless, by stopping its operation as in the present exemplary embodiment, power consumption of the battery <b>12</b> can be efficiently reduced.

0088In the present exemplary embodiment, when no external device is coupled to the USB connector <b>20</b>, the operation of the voltage-conversion circuit <b>40</b> is completely stopped by turning OFF the switching element <b>38</b>. Alternatively, it may be configured to reduce a switching frequency of the voltage-conversion circuit <b>40</b> that is configured as a DC-DC converter. The power consumed at the voltage-conversion circuit <b>40</b> can be reduced also in this way.

0089As for the voltage-conversion circuit <b>40</b> that is configured as a DC-DC converter in the present exemplary embodiment, its output voltage decreases when the value of the current that flows to the external device exceeds the upper limit; thus, an overheating of the voltage-conversion circuit <b>40</b> can be prevented or reduced by reducing electric power supplied to the external device from the voltage-conversion circuit <b>40</b> to the specified electric power or below.

0090In the present exemplary embodiment, different threshold values K<b>1</b> and K<b>3</b> are provided as the threshold values for determining whether to light the notification LED <b>28</b>. When the external device is coupled to the USB connector <b>20</b>, the threshold value K<b>1</b> is used that is smaller than the threshold value K<b>3</b>, which is used when no external device is coupled to the USB connector <b>20</b>.

0091Thus, the value of the battery voltage, at which the notification LED <b>28</b> is lit to encourage the user to charge the battery <b>12</b>, can be set lower when the external device is coupled to the USB connector <b>20</b> than when no external device is coupled to the USB connector <b>20</b>, so that electric power can be supplied to the external device until the battery <b>12</b> is empty. When no external device is coupled to the USB connector <b>20</b>, charge of the battery <b>12</b> can be started earlier.

0092In the present exemplary embodiment, when the value of the battery voltage becomes lower than the lowest overdischarge threshold value (the threshold value K<b>4</b>), the battery <b>12</b> is protected from being overdischarged by ceasing to light the notification LED <b>28</b> and ending the control process.

0093Alternatively, as shown in <figref idref="DRAWINGS">FIG. 6</figref>, it may be designed to cease lighting the notification LED <b>28</b> and to end the control process when a specified time has elapsed (S<b>145</b> or S<b>235</b>) since the lighting of the notification LED <b>28</b> in S<b>140</b> or in S<b>230</b>.

0094In the present exemplary embodiment, the voltage-conversion circuit <b>40</b> corresponds to an example of the power supply unit of the present disclosure; the external-device-detection circuit <b>46</b> corresponds to an example of the connection-detection unit of the present disclosure; the control circuit <b>50</b> corresponds to an example of the control unit of the present disclosure; the battery-voltage-measurement circuit <b>48</b> corresponds to an example of the voltage detection unit of the present disclosure; and, the light unit <b>6</b> corresponds to an example of the power-consumption unit of the present disclosure.

0095Embodiments of the present disclosure are as explained above; nevertheless, the present disclosure is not limited to the aforementioned exemplary embodiments and can be carried out in various modes without departing from the spirit of the present disclosure.

0096For example, it is assumed that the lighting device <b>2</b> of the aforementioned exemplary embodiment is used at a time of a disaster, such as an electric power outage or an earthquake, but stored in a designated storage place in normal times. If thus used, the lighting device <b>2</b> may not be found immediately when needed depending on how it is stored.

0097Thus, when no external device is coupled to the USB connector <b>20</b>, the control circuit <b>50</b> may light the notification LED <b>28</b> or the light-emitting elements <b>10</b> of the light unit <b>6</b> in accordance with a preset timing (for example, on a regular basis).

0098In this case, an oscillation sensor <b>62</b> may be incorporated into the lighting device <b>2</b>, as illustrated in dotted lines in <figref idref="DRAWINGS">FIG. 4</figref>, and the control circuit <b>50</b> may light the notification LED <b>28</b> or the light-emitting elements <b>10</b> of the light unit <b>6</b> in accordance with a preset timing (for example, on a regular basis) for a given length of time after the oscillation sensor <b>62</b> detects an oscillation. In a word, power consumption of the battery <b>12</b> can thus be reduced.

0099A luminance sensor <b>64</b> may be provided in the lighting device <b>2</b>, as illustrated in dotted lines in <figref idref="DRAWINGS">FIG. 4</figref>, and the control circuit <b>50</b> may permit the notification LED <b>28</b> or the light-emitting elements <b>10</b> of the light unit <b>6</b> to be lit in accordance with a preset timing (for example, on a regular basis) on condition that a value of luminance of the surroundings detected by the luminance sensor <b>64</b> is equal to or below a specified value.

0100The aforementioned exemplary embodiments relate to a lighting device; nevertheless, the present disclosure can be applied in the same manner as in the aforementioned exemplary embodiments to any rechargeable electric devices that comprise a rechargeable battery, such as a rechargeable electric power tool, a rechargeable gardening tool, a rechargeable electric fan, and a rechargeable radio.

0101A rechargeable electric device may be an adapter <b>70</b> that is attached to the battery pack <b>8</b> as shown in <figref idref="DRAWINGS">FIG. 7</figref> to supply electric power to the external device, such as a portable device.

0102In other words, this adapter <b>70</b> comprises the USB connector <b>20</b> and the cap <b>22</b> in the same manner as in the aforementioned exemplary embodiments. If the circuit board <b>30</b>, which comprises the components of the aforementioned exemplary embodiments except for the switching element <b>34</b> and the light unit <b>6</b>, is incorporated into the adapter <b>70</b>, and the control circuit <b>50</b> executes the same control process as in the aforementioned exemplary embodiments, the adapter <b>70</b> can be made as power-saving as the aforementioned exemplary embodiments are.

0103The aforementioned exemplary embodiments explain the electric device to which the battery pack comprising the battery can be detachably attached; nevertheless, the battery may be incorporated into the electric device and charged by coupling the electric device to an external battery charger.

0104In addition, the aforementioned exemplary embodiments explain that the power supply unit for supplying electric power to the external device is configured as the voltage-conversion circuit <b>40</b>; nevertheless, the power supply unit may be any circuits that can supply electric power to the external device, for example, any circuits that are typically used as power supply circuits.