DC power supply device

Provided is a DC power supply device If an electrical tool (81) of a rated voltage of 36 V is connected to the DC power supply device (1) (if the voltage of a lower positive terminal indicates the presence of a short bar), a microcomputer (30) performs control so as to switch a switching element (Q1) on and output a DC voltage of 36 V between an upper positive terminal and the upper negative terminal. If an electrical tool (81) of a rated voltage of 18 V is connected to the DC power supply device (1) (if the voltage of the lower positive terminal indicates the absence of a short bar), the microcomputer (30) performs control so as to switch a switching element (Q2) on and output a DC voltage of 18 V between the upper positive terminal and the upper negative terminal.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a 371 application of the international PCT application serial no. PCT/JP2018/040519, filed on Oct. 31, 2018, which claims the priority benefit of Japan applications no. 2017-231268, filed on Nov. 30, 2017; no. 2017-231269, filed on Nov. 30, 2017; and no. 2017-231270, filed on Nov. 30, 2017. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND OF THE INVENTION

Technical Field

The present invention relates to a DC power supply device that converts an AC current supplied from an external AC power supply into a DC current and supplies the DC current to an electrical tool.

Related Art

Conventionally, there is known a DC power supply device that is connected to a battery attaching/detaching unit of a cordless electrical tool, converts an external AC power supply into a DC power supply, and supplies the DC power supply as a drive power supply to the electrical tool. In general, when the DC power supply device is connected to an external AC power supply, an internal circuit is driven. Thus, even in a state that the DC power supply device is not connected to an electrical tool, the DC power supply device comes into a state of being capable of outputting a DC power supply (state that a DC voltage is applied between a positive-side output terminal and a negative-side output terminal).

LITERATURE OF RELATED ART

Patent Literature

SUMMARY

Problems to be Solved

Conventionally, in order to connect a DC power supply device to various electrical tools having different rated voltages, a converter and an adapter are arranged as separated units, and a different adapter is used for each rated voltage of the electrical tool, and thus use of common parts is hindered. In addition, the DC power supply device has internal circuits such as a transformer. Hence, in a state that a DC voltage is applied between a positive-side output terminal and a negative-side output terminal, the DC power supply device consumes electric power due to an operation of the internal circuits even when the DC power supply device is not connected to the electrical tool, and there is room for improvement in terms of a reduction in power consumption. In addition, if the DC power supply device stops output to the electrical tool due to abnormality, and the abnormality is solved while a trigger of the electrical tool is in an ON-state, there is an unexpected re-start of the electrical tool to a user in some cases when the output from the DC power supply device to the electrical tool is automatically re-started, and thus there is room for improvement in terms of a feeling of use.

The present invention is made in recognition of the above circumstances, and a first object thereof is to provide a DC power supply device that is suitable for being connected in common to a plurality of electrical tools having different rated voltages or for reducing power consumption.

A second object of the present invention is to provide a DC power supply device that is capable of inhibiting a connected electrical tool from being unexpectedly started.

Means to Solve Problems

According to a first aspect of the present invention, a DC power supply device is provided. The DC power supply device is connected to an external AC power supply and an electrical tool, converts an AC current supplied from the AC power supply into a DC current and supplies the DC current to the electrical tool. The DC power supply device includes: a detection part that detects information of the electrical tool that has been connected; and a switching circuit that switches between voltage values of the DC current which is supplied to the electrical tool, depending on a detection result obtained by the detection part.

The information may contain information of a rated voltage of the electrical tool that has been connected.

The DC power supply device may include: a connector unit that is connected to the external AC power supply; a cable unit having the connector unit at one end; and an adapter unit that is arranged at the other end of the cable unit and has the detection part, a connection unit, the switching circuit, and a conversion part that converts the AC current supplied from the AC power supply into the DC current. The conversion part may have a rectifying circuit and a voltage transforming circuit. The adapter unit may have an output terminal that is arranged at the connection unit and outputs the DC current to the electrical tool.

The adapter unit may have a housing and a fan, wherein the housing has an air inlet and an air outlet and accommodates the detection part, the rectifying circuit, and the voltage transforming circuit, and the fan is arranged in the housing and generates an air flow from the air inlet to the air outlet.

The adapter unit may have a first substrate which extends in a first direction in the housing. The output terminal may be arranged on a first surface side of the first substrate. The rectifying circuit and the voltage transforming circuit may be arranged on a second surface side of the first substrate. The first substrate may be positioned between the air inlet and the air outlet in the first direction.

The connection unit may be capable of being selectively connected to an electrical tool having a first rated voltage and an electrical tool having a second rated voltage lower than the first rated voltage. The switching circuit may output, to the output terminal, voltages from both ends on a secondary side of the voltage transforming circuit when the detection result obtained by the detection part indicates the first rated voltage, and the switching circuit may output, to the output terminal, a voltage between a center tap and one end on the secondary side of the voltage transforming circuit when the detection result obtained by the detection part indicates the second rated voltage.

The connection unit may be capable of being selectively connected to an electrical tool having a first rated voltage and an electrical tool having a second rated voltage lower than the first rated voltage. The switching circuit may set the voltage value to a first voltage when the detection result obtained by the detection part indicates the first rated voltage, and the switching circuit may not supply the DC voltage to the electrical tool when the detection result obtained by the detection part indicates the second rated voltage.

The information may contain information on a state of the electrical tool. The switching circuit may be a stopping part which stops output of a DC voltage to an output unit, depending on the detection result obtained by the detection part.

The DC power supply device may include: an input unit to which an AC voltage from the external AC power supply is input; and a voltage transforming circuit arranged between the input unit and the output unit. The stopping part may stop the output of the DC voltage to the output unit by cutting off an input current to the voltage transforming circuit.

The detection part may have a connection-state detection terminal which receives a signal indicating connection of the electrical tool, and the stopping part may stop the output of the DC voltage to the output unit when the detection part does not receive the signal indicating the connection of the electrical tool.

The DC power supply device may have a control unit which switches between whether or not the stopping part stops the output of the DC voltage to the output unit, a control-system power-supply unit which generates an operation voltage of the control unit, and a cut-off part that cuts off supply of the operation voltage from the control-system power-supply unit to the control unit when the stopping part stops the output of the DC voltage to the output unit.

According to a second aspect of the present invention, a DC power supply device is provided. The DC power supply device is connected to an external AC power supply and an electrical tool, converts an AC current supplied from the AC power supply into a DC current and supplies the DC current to the electrical tool. The DC power supply device includes: an abnormality detection part; a state detection part that detects a state of the electrical tool; an output unit that supplies the DC current to the electrical tool; and a cut-off part that cuts off output of the DC current to the output unit when the abnormality detection part detects abnormality. If the output is cut off due to the abnormality, the cut-off part cancels cut-off of the output according to a requirement condition that a predetermined state is detected by the state detection part.

The cut-off part may cancel the cut-off of the output when the abnormality is eliminated and when the predetermined state is detected by the state detection part.

The predetermined state may be a state that a stop operation of an operation unit is performed, wherein the operation unit instructs driving and stopping of the electrical tool.

The DC power supply device may include: a connector unit that is connected to the external AC power supply; a cable unit having the connector unit at one end; an adapter unit that is arranged at the other end of the cable unit and has a connection unit which is connected to the electrical tool; a first light emitting unit that turns on when abnormality is detected by the abnormality detection part; and a second light emitting unit that turns on when the electrical tool is connected to the DC power supply device. The first and second light emitting units may be arranged on a side of an extension origin of the cable unit, on a housing of the adapter unit.

Moreover, an optional combination of configurational elements described above or an example in which there is a change in description of the present invention in a method, a system, and the like is also valid as an aspect of the present invention.

Effect

According to the first aspect of the present invention, it is possible to provide a DC power supply device that is suitable for being connected in common to a plurality of electrical tools having different rated voltages or for reducing power consumption.

According to the second aspect of the present invention, it is possible to provide a DC power supply device that is capable of inhibiting a connected electrical tool from being unexpectedly started.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, preferred embodiments of the present invention are described in detail with reference to the drawings. Moreover, the same reference signs are assigned to the same or equivalent configurational elements, members, and the like illustrated in the drawings, and the repeated description thereof is appropriately omitted. In addition, the invention is not limited to the embodiments, and the embodiments are provided as examples of the invention. Characteristics or combinations thereof which are described in the embodiments are not all necessarily essential to the invention.

With reference toFIGS. 1 to 7, a mechanical configuration of a DC power supply device1according to Embodiment 1 of the present invention is described. Front-rear, up-down, and right-left directions which are orthogonal to each other in the DC power supply device1are defined as illustrated inFIG. 1. The DC power supply device1includes a plug unit7(FIG. 5) serving as a connector unit which is connected to an external AC power supply, a cable unit5which has the plug unit7at one end, and an adapter unit10arranged at the other end of the cable unit5. As illustrated inFIG. 1, the cable unit5extends from a lower front portion of the adapter unit10, and an extending direction of the cable unit5from the adapter unit10is variable from a front direction to a down direction.

The adapter unit10has a housing11having substantially the same shape as that of a housing of a battery pack which is used as a power supply of a cordless electrical tool (hereinafter, simply described as a “battery pack”). The adapter unit10also has the same terminal structure as that of the battery pack and is detachably connected (installed) to a battery attaching/detaching unit of the electrical tool instead of the battery pack. In addition, the adapter unit10can be connected in common to a plurality of electrical tools having different rated voltages. For example, as illustrated inFIG. 8, the adapter unit10is detachably connected to a battery attaching/detaching unit82aat a lower end portion of a handle unit82of an impact driver80A which is a cordless electrical tool having a rated voltage of 18 V (example of a second rated voltage). Otherwise, as illustrated inFIG. 9, the adapter unit10is detachably connected to a battery attaching/detaching unit84aat a lower portion of a rear end of a handle unit84of a portable circular saw80B which is a cordless electrical tool having a rated voltage of 36 V (example of a first rated voltage). A trigger (operation unit)82bis arranged at an upper end portion of the handle unit82of the impact driver80A illustrated inFIG. 8. A trigger (operation unit)84bis arranged at a front end portion of the handle unit84of the portable circular saw80B illustrated inFIG. 9.

The housing11of the adapter unit10has air inlets12at both right and left side surfaces and has air outlets13at an upper portion of a front surface. In addition, similarly to the battery pack, the housing11has rails16at right and left sides, respectively, the rails becoming a guide when the housing slides to be connected to the electrical tool. Similarly to the battery pack, a latch mechanism is arranged on the housing11for engagement to the electrical tool, the latch mechanism including a pair of right and left latch operation unit17and a latch projection portion19(FIGS. 3 and 5) which is switched between projection and non-projection toward the rails16by the latch operation unit17. A plurality of slits18for terminal connection is arranged at an upper surface of the housing11. A terminal35illustrated inFIG. 6faces the outside from the slits18. A first LED14and a second LED15as first and second light emitting units are arranged at the upper surface on a front side (side of an extension origin of the cable unit5) of the housing11. The first LED14is, for example, a red LED that is turned on when abnormality is detected. The second LED15is, for example, a green LED that is turned on when the adapter unit10is connected to the electrical tool.

As illustrated inFIG. 6, a first substrate20, on which terminals35(positive and negative terminals and other terminals illustrated inFIG. 10) for connection to the electrical tool are mounted, is arranged (for example, screwed to be fixed) on an upper portion of an internal space of the housing11. The first substrate20is substantially perpendicular to the up-down direction and extends in the front-rear direction serving as a first direction. The terminals35are mounted on an upper surface (arranged at a side of the upper surface) serving as a first surface of the first substrate20. The first substrate20is positioned between the air inlets12and the air outlets13in the front-rear direction. A cooling fan33that generates an air flow (cooling air) from the air inlets12to the air outlets13is arranged at an upper front portion in the housing11. Dashed-line arrows inFIG. 6represent flowing of the air flow generated by the cooling fan33.

A second substrate40is arranged at a lower portion of the internal space of the housing11. Circuit parts such as a transformer22(circuit parts that configure the DC power supply device1illustrated inFIG. 10) are mounted on the second substrate40. The circuit parts such as the transformer22on the second substrate40are arranged on a side of a lower surface serving as a second surface of the first substrate20and are positioned between the air inlets12and the air outlets13in the front-rear direction. The air flow generated by the cooling fan33is drawn into the housing11from the air inlets12, cools the circuit parts such as the transformer22, the terminals35on the first substrate20, the first LED14, and the second LED15, and is exhausted out of the housing11from the air outlets13. The first substrate20also functions as a rectifying plate (air guiding plate) of the air flow generated by the cooling fan33.

FIG. 10is a circuit diagram illustrating a state that the DC power supply device1is connected to an external AC power supply50and an electrical tool81. The configuration of the electrical tool81is not particularly limited; however, in an example inFIG. 10, the electrical tool81includes a brushless motor85and an inverter circuit83that drives the brushless motor85. In addition, a capacitor C2is arranged between an upper positive terminal and an upper negative terminal of the electrical tool81, and a short bar89is arranged between a lower positive terminal and a lower negative terminal of the electrical tool81. The short bar89is a member that causes short circuit between the lower positive terminal and the lower negative terminal. The short bar89is present if the electrical tool81has a rated voltage of 36 V and is not present (short circuit does not occur between the lower positive terminal and the lower negative terminal) if the electrical tool81has a rated voltage of 18 V. Although not illustrated, the electrical tool81includes a control unit such as a microcomputer that controls driving of the inverter circuit83. A switch SW1arranged on a route of an input current to the inverter circuit83is switched on and off through an operation of a trigger (operation unit) by a user.

In the DC power supply device1, a diode bridge21serving as the rectifying circuit is arranged between output terminals of the AC power supply50. A smoothing capacitor C1, a primary winding of the transformer22, an auxiliary power supply28serving as a control-system power-supply unit are arranged in parallel between output terminals of the diode bridge21. A switching element23such as a FET or an IGBT is arranged on a route of a current supplied from the diode bridge21to the primary winding of the transformer22. The transformer22is an isolation transformer, and the auxiliary power supply28also includes an isolation transformer. Hence, a connection terminal (input unit) of the DC power supply device1to the AC power supply and a connection terminal of the DC power supply device1to the electrical tool are insulated from each other.

Both ends of a secondary winding of the transformer22are connected to respective output units (upper positive terminal and upper negative terminal) which output a DC voltage to the electrical tool81. A switching element Q1such as an FET or an IGBT is arranged between one end of the secondary winding of the transformer22and the upper positive terminal. A center tap of the secondary winding of the transformer22is connected to the upper positive terminal via a switching element Q2such as an FET or an IGBT. The center tap is arranged at a position at which winding of the secondary winding is divided by a predetermined division ratio (for example, 1 to 1). The switching elements Q1and Q2configure a switching circuit that switches between voltage values of a DC current supplied to the electrical tool81. A voltage detection circuit26is arranged between both ends of the secondary winding of the transformer22and between the center tap and the other end of the secondary winding. A current detection resistor R1is arranged between the other end of the secondary winding of the transformer22and the upper negative terminal. Voltages of both ends of the resistor R1are transmitted to a microcomputer30(wiring not illustrated). The upper negative terminal and the lower negative terminal are connected to each other. An output terminal of the auxiliary power supply28is connected via a regulator29to a power input terminal of the microcomputer30serving as the control unit.

An AC voltage (AC current) supplied from the AC power supply50is rectified and smoothened by the diode bridge21and the capacitor C1and is input to the primary winding of the transformer22and the auxiliary power supply28. Switching (on/off) of the switching element23is controlled by control of a switching control circuit24, and thereby a voltage in proportion to a winding ratio to the primary winding is induced at both ends of the secondary winding of the transformer22and the center tap. A constant-voltage control circuit25receives a detection result obtained by the voltage detection circuit26and controls an operation of the switching control circuit24with control performed by the microcomputer30. Consequently, switching of the switching element23is controlled such that the voltages of both ends of the secondary winding of the transformer22are constant at 36 V, or the voltage of the center tap is constant at 18 V.

The microcomputer30detects a rated voltage of the electrical tool81(for example, detects whether the voltage is 36 V or 18 V) according to the voltage of the lower negative terminal. The short bar89that causes short circuit between the lower positive terminal and the lower negative terminal is present if the electrical tool81has a rated voltage of 36 V, and the short bar is not present if the electrical tool81has a rated voltage of 18 V. Hence, in a state that the electrical tool81having a rated voltage of 36 V is connected to the DC power supply device1, due to the short bar89, a voltage of the lower positive terminal becomes a voltage (value approximate to 0 V which is the ground potential) obtained by dividing a power-supply voltage of 5 V by resistors R2and R1. On the other hand, in a state that the electrical tool81having a rated voltage of 18 V is connected to the DC power supply device1, the short bar89is not present. Hence, a voltage value of the lower positive terminal is pulled up by the resistor R2and becomes 5 V. Hence, the microcomputer30can detect the rated voltage of the electrical tool81connected to the DC power supply device1according to the voltage of the lower positive terminal.

When the electrical tool81having a rated voltage of 36 V is connected to the DC power supply device1(when the voltage of the lower positive terminal indicates the presence of the short bar), the microcomputer30performs control so as to switch the switching element Q1on and switch the switching element Q2off, outputting a DC voltage (DC current) of 36 V between the upper positive terminal and the upper negative terminal. On the other hand, when the electrical tool81having a rated voltage of 18 V is connected to the DC power supply device1(when the voltage of the lower positive terminal indicates the absence of the short bar), the microcomputer30performs control so as to switch the switching element Q2on and switch the switching element Q1off, outputting a DC voltage (DC current) of 18 V between the upper positive terminal and the upper negative terminal.

A fan-motor driving circuit31operates according to the control performed by the microcomputer30and drives a fan motor32. The fan motor32is a motor that drives the cooling fan33illustrated inFIG. 6. The microcomputer30controls turning-on and turning-off of the first LED14and the second LED15.

According to the embodiment, the following effects can be achieved.

(1) A conversion part (the diode bridge21or the transformer22) that converts an AC voltage (AC current) into a DC voltage (DC current) is arranged in the adapter unit10, and the adapter unit10can be connected to both the electrical tool having a rated voltage of 36 V and the electrical tool having a rated voltage of 18 V. Hence, an adapter unit10having a different shape is not required to be arranged for each rated voltage of the electrical tool, and the embodiment is advantageous in terms of use of common parts.

(2) For example, when a DC voltage of 36 V is supplied to the electrical tool having a rated voltage of 18 V, there is a possibility that elements of the electrical tool will malfunction or break down due to an overvoltage. However, in the DC power supply device1, a DC voltage matching the rated voltage of the connected electrical tool is supplied, and thus it is possible to reduce the possibility.

(3) The voltages of both ends of the secondary winding of the transformer22are used when the DC voltage of 36 V is output, and the voltage of the center tap of the secondary winding is used when the DC voltage of 18 V is output. Hence, the embodiment is highly efficient compared with a case of switching the output voltage by control of the switching element23only.

(4) Unlike the battery pack, the DC power supply device1can be used for a long time without running out of capacity, and thus the terminal35connected to the electrical tool has a temperature higher than that of a terminal of the battery. However, the air flow generated by the cooling fan33cools the terminal35, and thus it is possible to suitably suppress overheating of the terminal35.

FIG. 11is a circuit diagram illustrating a state that a DC power supply device2according to Embodiment 2 of the present invention is connected to the external AC power supply50and the electrical tool81. Unlike the DC power supply device1illustrated inFIG. 10, in the DC power supply device2, the secondary winding of the transformer22does not have the center tap, and the switching elements Q1and Q2are not present either. When the electrical tool81having a rated voltage of 36 V is connected to the DC power supply device2, the microcomputer30performs control so as to activate the constant-voltage control circuit25and enable the switching control circuit24to perform switching control on the switching element23, outputting a DC voltage (DC current) of 36 V between the upper positive terminal and the upper negative terminal. On the other hand, when the electrical tool81having a rated voltage of 18 V is connected to the DC power supply device2, the microcomputer30deactivates (stops) the constant-voltage control circuit25so as to disable the switching control circuit24from performing switching control on the switching element23(that is, so as to switch off the switching element23serving as a stopping part and cut off an input current to the transformer22), and stops output of the DC voltage (DC current) between the upper positive terminal and the upper negative terminal. Except for the above aspect, the embodiment is the same as Embodiment 1. According to the embodiment, the DC voltage is not supplied to the electrical tool having a rated voltage of 18 V, and thereby it is possible to reduce the possibility that elements of the electrical tool malfunction or break down due to an overvoltage.

FIG. 12is a circuit diagram illustrating a state that a DC power supply device3according to Embodiment 3 of the present invention is connected to the external AC power supply50and an electrical tool81a. Hereinafter, the description will focus on differences from Embodiment 2 illustrated inFIG. 11. The electrical tool81adoes not have the lower positive terminal and the lower negative terminal of the electrical tool81inFIG. 11. A positive terminal and a negative terminal of the electrical tool81acorrespond to the upper positive terminal and the upper negative terminal of the electrical tool81inFIG. 11. The electrical tool81ahas a T terminal. A resistor R3is arranged between the T terminal and the negative terminal.

The DC power supply device3does not have the lower positive terminal and the lower negative terminal of the DC power supply device2inFIG. 11. A positive terminal and a negative terminal of the DC power supply device3correspond to the upper positive terminal and the upper negative terminal of the DC power supply device2inFIG. 11. The DC power supply device3has a T terminal serving as a connection-state detection terminal. The microcomputer30detects presence or absence of connection of the electrical tool81aaccording to a voltage of the T terminal. The resistor R3is arranged between the T terminal and the negative terminal of the electrical tool81a. Hence, in a state that the electrical tool81ais connected to the DC power supply device3, the voltage of the T terminal becomes a voltage obtained by dividing a power-supply voltage of 5 V by resistors R2and R3. On the other hand, in a state that the electrical tool81ais not connected to the DC power supply device3, the voltage of the T terminal becomes 5 V. Hence, the microcomputer30can detect whether or not the electrical tool81ais connected to the DC power supply device3, according to the voltage of the T terminal (signal from the electrical tool81awhich is received from the T terminal).

When the electrical tool81ais connected to the DC power supply device3(when the voltage of the T terminal indicates the connection of the electrical tool81a), the microcomputer30performs control so as to activate the constant-voltage control circuit25and enable the switching control circuit24to perform switching control on the switching element23, outputting a DC voltage (DC current) between the upper positive terminal and the upper negative terminal (supply a DC power supply to the electrical tool81a). When the electrical tool81ais not connected to the DC power supply device3(when the voltage of the T terminal is 5 V and indicates an opening state, that is, disconnection of the electrical tool81a), the microcomputer30deactivates (stops) the constant-voltage control circuit25so as to disable the switching control circuit24from performing switching control on the switching element23(that is, so as to switch off the switching element23serving as the stopping part and cut off an input current to the transformer22), and stops output of the DC voltage (DC current) between the positive terminal and the negative terminal.

According to the embodiment, the following effects can be achieved.

(1) In a state that the electrical tool is not connected to the DC power supply device3, the microcomputer30performs control so as to switch the switching element23off and cut off the input current to the transformer22. Hence, compared with a case that switching control of the switching element23is performed even in the state that the electrical tool is not connected to the DC power supply device3, it is possible to reduce power consumption of the transformer22or the voltage detection circuit26, and it is possible to reduce power consumption of the DC power supply device3as a whole.

(2) In the state that the electrical tool is not connected to the DC power supply device3, the DC voltage (DC current) is not output between the positive terminal and the negative terminal of the DC power supply device3, and thus the embodiment is preferable in design.

FIG. 13is a circuit diagram illustrating a state that a DC power supply device4according to Embodiment 4 of the present invention is connected to the external AC power supply50and an electrical tool81b. Hereinafter, the description will focus on differencesFIG. 12. The electrical tool81bhas a switch SW2which is connected to a microcomputer87arranged in the electrical tool81b. One end of the switch SW2is connected to the microcomputer87, and the other end thereof is connected to a V terminal. The switch SW2is switched on and off together with the switch SW1through an operation of a trigger by a user. When the switch SW2is switched on, a signal of a ground level is output to the microcomputer87and the V terminal.

The DC power supply device4includes a cut-off part (cut-off circuit) that cuts off supply of an operation voltage from the auxiliary power supply28to the microcomputer30when the switch SW2is switched on in the electrical tool81band does not cut off the supply of the operation voltage from the auxiliary power supply28to the microcomputer30when the switch SW2is switched off in the electrical tool81b. The cut-off part includes transistors Q3to Q5serving as switching elements, resistors R5to R7, and a Zener diode ZD. The transistors Q3and Q5are PNP transistors, and the transistor Q4is a NPN transistor. When the switch SW2is switched on in the electrical tool81b, a potential of the V terminal serving as a driving-state detection terminal (base potential of the transistor Q3) becomes the ground potential, a current flows in a route from the resistor R5through the Zener diode ZD, the resistor R6, and the V terminal to the ground, a voltage between a base and an emitter of the transistor Q3becomes negative due to a voltage drop caused by the resistor R6, and the transistor Q3turns on. When the transistor Q3turns on, a current flows in a route from the resistor R5through the Zener diode ZD and the transistor Q3to the resistor R7, a voltage between a base and an emitter of the transistor Q4becomes positive due to a voltage drop caused by the resistor R7, and the transistor Q4turns on. When the transistor Q4turns on, a current flows in a route from the resistor R5through the Zener diode ZD and the resistor R6to the transistor Q4. A voltage between a base and an emitter of the transistor Q5becomes negative due to a voltage drop caused by the resistor R5, and the transistor Q5turns on. Consequently, a constant operation voltage (for example, 5 V) is supplied from a collector of the transistor Q5to the microcomputer30.

When the switch SW2is switched off in the electrical tool81b, the base potential of the transistor Q3becomes unstable, no current flows to the resistor R6, the voltage between the base and the emitter of the transistor Q3becomes zero, and the transistor Q3turns off. Consequently, no current flows to the resistor R7, the voltage between the base and the emitter of the transistor Q4becomes zero, and the transistor Q4turns off. In addition, no current flows to the resistor R5, the voltage between the base and the emitter of the transistor Q5becomes zero, and the transistor Q5turns off. Consequently, supply of the operation voltage from the auxiliary power supply28to the microcomputer30is cut off. Except for the above aspect, the DC power supply device4is the same as the DC power supply device3.

According to the embodiment, the same effects as those of Embodiment 3 can also be achieved. In addition, according to the embodiment, when the trigger of the electrical tool81bis turned off (when the switches SW1and SW2are switched off, and the brushless motor85is not driven), the supply of the operation voltage to the microcomputer30is cut off and the microcomputer30is stopped, and thus it is also possible to reduce power consumption during the connection to the electrical tool81b.

FIG. 14is a circuit diagram illustrating a state that a DC power supply device3A according to Embodiment 5 of the present invention is connected to the external AC power supply50and an electrical tool81c. The electrical tool81cis the same as the electrical tool81ainFIG. 12except that an electronic switch SW3is arranged. The electronic switch SW3is switched on and off together with the switch SW1through an operation of a trigger (operation unit) by the user. The DC power supply device3A is the same as the DC power supply device3inFIG. 12except that the microcomputer30is connected to the electronic switch SW3of the electrical tool81cvia the V terminal.

The microcomputer30detects on and off of the trigger as a state of the electrical tool81caccording to a voltage of the V terminal serving as the driving-state detection terminal that configures a state detection part. When the trigger is operated to be on in the electrical tool81c, the electronic switch SW3is switched on, a signal (signal indicating a driving operation of the trigger) from the electronic switch SW3is transmitted to the microcomputer30via the V terminal, and the microcomputer30can detect that the trigger of the electrical tool81cis driven. When the trigger is operated to be off in the electrical tool81c, the electronic switch SW3is switched off, the signal from the electronic switch SW3is not transmitted, and the microcomputer30can detect that the trigger of the electrical tool81cis operated to be stopped.

FIG. 15is a control flowchart of the DC power supply device3A. When the microcomputer30detects that the electrical tool is connected to the DC power supply device3A (YES in S1), the microcomputer turns on a green LED (example of the second LED15) (S2) and performs switching control of a FET (example of the switching element23) (S3). Consequently, an output of a DC voltage (DC current) between the positive terminal and the negative terminal is started. When the microcomputer30detects abnormality (YES in S4), the microcomputer turns on a red LED (example of the first LED14) (S5) and turns off the FET (S6). Consequently, the output of the DC voltage (DC current) between the positive terminal and the negative terminal is stopped. The abnormality includes at least one of temperature abnormality, input voltage abnormality, and overcurrent abnormality of each unit (transformer22, switching element23, and the like). A temperature sensor such as a thermistor (not illustrated), an input-voltage detection part (not illustrated), or the current detection resistor R1functions as abnormality detection part.

After the detection of abnormality (YES in S4), if the trigger is not operated to be off (operated to be stopped) (NO in S7), the microcomputer30maintains turning-on of the red LED (S5) and turning-off of the FET (S6) regardless of whether or not an abnormality state is eliminated. In a state that the trigger is operated to be off (YES in S7), when the abnormality state is eliminated (NO in S8), the microcomputer30turns off the red LED (S9), and the process returns to step S1.

According to the embodiment, the following effects can be achieved.

(1) If the output of the DC voltage (DC current) between the positive terminal and the negative terminal is stopped (cut off) due to the abnormality, the microcomputer30maintains stopping of the output until an off operation of the trigger in the electrical tool is detected. Hence, even when the abnormality is eliminated while the trigger is in an on state, the output of the DC voltage (DC current) from the DC power supply device3A to the electrical tool is not re-started, and thus it is possible to inhibit unexpected re-starting of the electrical tool for the user, and the feeling of use can be improved.

(2) Because the microcomputer30turns on the first LED14to notify the user of the abnormality when abnormality is detected, the user can quickly know the occurrence of the abnormality in the DC power supply device3A, and the DC power supply device3A is convenient to use.

(3) When the electrical tool is correctly connected (able to supply electric power) to the DC power supply device3A, the microcomputer30turns on the second LED15to notify the user of the connection, and thus the user can quickly know the success of the connection, and the DC power supply device3A is convenient to use.

As described above, the present invention is described with the embodiments as examples; however, those skilled in the art understand that it is possible to perform various modifications on every configurational element or every processing process of the embodiments within a range of the claims. Hereinafter, modification examples will be described.

In Embodiments 1 and 2, an example in which the rated voltage of the electrical tool81is detected based on presence and absence of the short bar89is described; however, the rated voltage may be detected based on an identification resistor arranged in the electrical tool. In the DC power supply device1of Embodiment 1, two levels (36 V and 18 V) of DC voltages can be output to the electrical tool; however, three or more levels of DC voltages may be output.

In Embodiments 3 and 4, whether or not the electrical tool is connected to the DC power supply device is determined based on the voltage of the T terminal; however, a switch such as a button which is pushed when the electrical tool is connected may be arranged in the vicinity of a terminal of the DC power supply device, and the output of the DC voltage (DC current) is stopped if the switch is switched off (if the button is not pushed when the switch is the button).

In Embodiment 5, the condition of output cut-off cancellation when the abnormality is eliminated in the DC power supply device is that the trigger of the electrical tool is operated to be off. However, a switch such as a button for the output cut-off cancellation which can be operated by the user may be separately arranged on the electrical tool or the DC power supply device, and the output cut-off cancellation may be performed if the switch is switched on (if the button is pushed when the switch is a button).