WO2010074351A2

WO2010074351A2 - Charging device

Info

Publication number: WO2010074351A2
Application number: PCT/JP2009/071913
Authority: WO
Inventors: Yasushi Nakano; Nobuhiro Takano; Kazuhiko Funabashi
Original assignee: Hitachi Koki Co., Ltd.
Priority date: 2008-12-26
Filing date: 2009-12-25
Publication date: 2010-07-01
Also published as: JP2010154703A; WO2010074351A3

Abstract

Charging device (1) includes a transformer (10) that is equipped with two input windings (10a, 10b) provided to correspond to connection terminals (4, 5) of at least two input power sources (2, 3), together with a charging output winding (10c) to output charging power voltage by being electromagnetically coupled to the input windings (10a, 10b), as well as an auxiliary output winding (10d) to output an electric circuit power voltage; a first switching element (11) and a second switching element (12) electrically connected respectively to input windings (10a, 10b); and a switching control circuit (13) to mutually control the first and second switching elements (11, 12).

Description

DESCRIPTION

Title of the Invention CHARGING DEVICE

Technical Field

[0001] The present invention relates to a charging device for charging a battery pack including a unit cell such as a nickel-cadmium rechargeable battery (hereafter abbreviated as "NiCd rechargeable battery") or a lithium-ion rechargeable battery used as a power source of portable equipment such as cordless electric power tools, and particularly relates to a charging device that can use a plurality of power sources including commercial power as input power.

Background Art

[0002] Battery packs including NiCd rechargeable batteries or lithium ion rechargeable batteries are generally used in portable equipment such as cordless electric power tools. A charging device for charging a battery pack including a NiCd rechargeable battery or a lithium ion rechargeable battery conventionally uses commercial power as input power. However, using cordless electric power tools in a location where there is no commercial power facilities requires the preparation of multiple spare battery packs when there is a large work load. This results in compounded equipment cost for battery packs and increasing difficulty in transport labor of battery packs to the work site. [0003] Therefore, a charging device is proposed that is constituted to enable charging from at least two types of input power, including commercial power, as input power of the charging device to charge a battery pack. Charging devices are disclosed, for instance, in Patent Literature 1 (Unexamined Japanese Patent Application KOKAI Publication No. 2005-245145) and Patent Literature 2 (Unexamined Japanese Patent Application KOKAI Publication No. 2008-236878) below in which a DC power source can also be used besides an AC power source as the input power source.

Summary of the Invention

[0004] However, in the known charging device that can use a plurality of power types as input power, as disclosed in the patent literature, a power circuit has a plurality of transformers (switching transformers) or a plurality of switching control circuits that correspond to the number of the plurality of input power types. As a result, the number (count) of parts required in the charging device increases.

[0005] Accordingly, an object of the present invention is to provide a charging device that charges a battery pack by power supplied from a plurality of kinds of power sources [0006] The following is a description of the representative features disclosed according to the present invention to solve the problems described above. [0007] One feature of the present invention is a charging device that can charge a battery pack by power supplied from either one of two input power sources, comprising: a transformer including two input windings provided to correspond to respective ones of the two input power sources, as well as including a charging output winding to output a charging power voltage by being electromagnetically coupled to the two input windings; first and second switching elements for switching current that flows to each input winding, each switching element being connected with each input winding of the transformer; a charging circuit for outputting a charging current or a charging voltage to the battery pack by being coupled with the charging output winding of the transformer; and a switching control circuit for commonly controlling the first and second switching elements. [0008] According to another feature of the present invention, a control unit for setting the charging current or the charging voltage of the charging circuit corresponding to the type of the two input power sources and outputting a control signal corresponding to the set charging current or the set charging voltage is further provided, and the switching control circuit commonly controls the first and second switching elements based on the control signal output from the control unit

[0009] According to another feature of the present invention, the transformer is equipped with an auxiliary output winding for outputting power voltage to the electric circuit within the charging device. [0010] According to still another feature of the present invention further comprises two input voltage detection units for detecting the respective voltage inputted to each input winding of the transformer, and two switching units provided for alternatively switching electric power transmission lines, to the first and second switching elements, coupled to each input winding based on the output of the input voltage detecting unit, to be brought into a conducting or a non-conducting state. [0011 ] According to still another feature of the present invention, the two input power sources are electrically connected detachably, by power cables with mutually differing appearance profiles, with corresponding connection terminals.

[0012] Still another feature of the present invention further comprises two connection terminals for electrically being connected with respective ones of two input power sources; and a connection prohibiting unit for preventing other connection terminal than the connection terminal that is alternately electrically connected to the corresponding input power from being connected to the corresponding input power.

[0013] According to still another feature of the present invention, the connection prohibiting unit comprises a shielding plate which covers the other connection terminal. [0014] According to still another feature of the present invention, one input power among the two input power sources is a commercial AC power source. [0015] According to still another feature of the present invention, the control unit includes a latch circuit for stopping the switching control circuit when determining that the two input power sources are electrically connected with the charging device

[0016] According to the features of the present invention described above, because commonality is enabled in the switching transformer (high frequency transformer) and the switching control circuit for a plurality of types of input power sources, a charging device can be provided that suppresses an enlarged size and the manufacturing cost of a charging device and which has the ability to charge a battery pack by at least one power of either of two types of input power.

Brief Description of Drawings [0017] Fig. 1 is an outline view showing a charging device according to an embodiment of the present invention.

Fig. 2 is a block diagram of a circuit of the charging device shown in Fig. 1.

Fig. 3 A is a circuit diagram showing a specific example of a first switching unit.

Fig. 3 B is a circuit diagram showing a specific example of a second switching unit. Fig. 4 is a block diagram showing a specific example of a switching control circuit shown in Fig. 2.

Fig. 5 is a control flowchart to explain the operation of the charging device of FIG. 2.

Best Mode for Carrying Out the Invention [0018] The above and other objects of the present invention, together with the above and other features, are further clarified from the description of the Specification to follow as well as the attached drawings.

[0019] A description will be given hereafter regarding a charging device according to an embodiment of the present invention with reference to Fig. 1 through Fig. 5. In addition, members that indicate the same functions and elements are numbered with the same reference numerals in drawings to describe an embodiment, and thereby redundant description will be omitted. [0020] Fig. 1 is an outline view showing a charging device according to an embodiment of the present invention. Fig. 2 is a block diagram of a circuit of the charging device shown in Fig. 1. Fig. 3 A as well as B are circuit diagrams each showing a specific example of a first switching unit and a second switching unit. Fig. 4 is a block diagram showing a specific example of a switching control circuit shown in Fig. 2. Fig. 5 is a control flowchart to explain the operation of the charging device of the present invention.

[0021] The Overall Constitution of the Charging Device

First, a description regarding the overall constitution of the charging device 1 will be given with reference to the block diagram of the circuit of the charging device of Fig. 2. The embodiment shown in Fig. 2 is an example of charging a lithium-ion battery pack 40 used in codeless electric power tools, by the charging device 1. The device is designed to connect with input power sources including commercial power source 2 or DC power source 3 that is different from the commercial power source 2. [0022] In other words, the charging device 1 can be connected to either one of at least two input power sources (commercial power source 2 or DC power source 3). For example, at a job site where commercial power source 2 is provided as input power source for the charging device 1, power from the commercial power source 2 is supplied to AC connector 4 through AC cable 4a (see Fig. 1). On the other hand, at a job site where there is no commercial power source as the input power source for the charging device 1 , power is supplied to DC connector 5 through DC cable 5 a (see Fig. 1) from DC power source 2 such as, for example, a car battery.

[0023] In addition, as shown in Fig. 1 , a slide plate 50 is provided that has the ability to slide laterally in an X direction at a connection exposed surface of AC connector 4 and DC connector 5 where AC cable 4a as well as DC cable 5a are connected respectively. Thereby when either one of AC connector 4 or DC connector 5 is connected to the cable 4a or 5a, the other connector (5 or 4) is shielded by the slide plate 50 so that the other unnecessary power supply can be protected.

[0024] Battery pack 40 includes a protection IC 41, a battery group 42, a thermal protector 43 to prevent abnormal temperature rise at the time of charging, an identification resistor 44 to identify the type of battery such as a lithium ion rechargeable battery (unit cell) and number of rechargeable battery cells (unit cell count) that compose the battery group 42, an overcharge signal transfer unit 45 to cause a battery temperature terminal LS to output an abnormal signal by being supplied with a drive power Vcc, and a heat sensitive element 46 such as a thermistor; and the battery pack 40 is electrically connected to the battery device 1 by a plurality of terminals 56 (including +, -, T, LS, and LD). [0025] The type of battery pack 40 is detected by a resistance value of the identification resistor 44 that is set in advance corresponding to the type of battery pack 40. The output of the identification resistor 44 is input to the identification resistance detection circuit 29 of the charging device 1, and compared with types of battery packs 40 stored in advance in a microcomputer 17 of the charging device 1, so that the type of battery pack is identified. The condition for carrying out battercy charge by using the charging device 1 can be set to correspond to the type of battery pack 40 by the working of the identification resistor 44.

[0026] The battery pack 40 includes, for example, a unit cell group 42 consisting of a plurality of lithium-ion rechargeable battery cells. The unit cell group 42 is controlled so as to prevent an overcharged state or an over discharged state (or over current state). For such control, protection IC 41 includes an overcharge detection circuit and over discharge/over current detection circuit for monitoring terminal voltage and load current of each cell of the unit cell group 42. [0027] Thermal protector 43 integrated into the battery pack 40 is constituted by a thermostatic switch using bimetallic contacts that transforms in response to the temperature of the heat generated from the unit cell group 42, and when the temperature of the unit cell group 42 reaches a designated temperature or above (for example, at 80 °C or above), the function operates so as to break the charging path. After the breaking, when the temperature of the unit cell group 42 decreases to less than the designated temperature, the charging path is connected again. The thermal protector 43 is connected so as to achieve a dual protection function for battery temperature along with the function of a thermal sensitive element 46.

[0028] The thermal sensitive element 46 described above is a thermal sensitive element arranged contacting or adjoining the unit cell group 42 to detect battery temperature at the time of charging the unit cell group 42, and constituted by, for example, a thermistor. The detection information of the battery temperature in the thermal sensitive element 46 is input to the microcomputer 17 of the charging device 1 through the battery temperature detection circuit 30 in the battery device 1.

[0029] High frequency transformer (switching transformer) 10 is equipped with two input windings 10a, 10b provided to correspond to connectors 4, 5 for supplying the power from commercial power source 2 or DC power source 3, a charge output winding 10c for outputting power voltage for charging by electromagnetic coupling in relation to the input windings 10a, 10b, and an auxiliary output winding 1Od for outputting the electric circuit power voltage (drive voltage Vcc). The high frequency transformer 10 occupies a comparatively large area, so one transformer for a plurality of input power sources is used according to this embodiment. [0030] A first smoothing circuit 6 forms a part of an input circuit that is coupled with the input winding 10a of the transformer 10, and is equipped with a rectification circuit for rectifying a current from commercial power source 2 (AC power source), and a smoothing circuit consisting of a smoothing capacitor, resistance, and the like (not illustrated). The current from commercial power source 2 is fully rectified by the first smoothing circuit 6, and the rectified voltage is smoothed to DC voltage by the first smoothing circuit 6.

[0031] A second smoothing circuit 7 forms a part of an input circuit that is coupled with the input winding 10b of the transformer 10, and is a smoothing circuit, for smoothing the input voltage that is input from the DC power source 3, consisting of a smoothing capacitor, resistance, and the like (not illustrated). This circuit does not include any rectification circuit. A third smoothing circuit 8 is a smoothing circuit that includes a rectification circuit that is coupled with the charge output winding 10c of the high frequency transformer 10. DC voltage for charging the battery pack 40 is output by this circuit.

[0032] A fourth smoothing circuit 9 is a smoothing circuit that includes a rectification circuit that is coupled with the auxiliary output winding 1Od of the high frequency transformer 10. DC output of the fourth smoothing circuit 9 is converted to the designated DC voltage by the constant voltage circuit 14, and the converted designated DC voltage is output as the drive voltage Vcc to the control circuit that includes the microcomputer 17. A first switching element 11 is composed of, for example, a power MOSFET (power insulated-gate field-effect transistor). The source or drain output terminal of the first switching element 11 is serially connected to the input winding 10a, and the DC output voltage of the first smoothing circuit 6 is switched by the first switching element 11 and output to the input winding 10a. The first switching element 11 is serially connected to the input winding 10a.

[0033] A second switching element 12 is composed of a semiconductor switching element (for example, MOSFET) similar to the first switching element 11. The source or drain output terminal of the second switching element 12 is serially connected to the input winding 10b and the DC output voltage of the second smoothing circuit 7 is switched by the second switching element 12 and output to the input winding 10b. The second switching element 12 is serially connected to the input winding 10b. [0034] A switching control circuit 13 supplies the drive pulse for a switching operation to either the first switching element 11 or the second switching element 12, and also controls the pulse width of the drive pulse. Thereby the voltage generated at the output winding 10c of the transformer 10 is controlled and the output voltage of the third smoothing circuit 8 is controlled.

[0035] A switching control circuit 13, as illustrated in Fig. 4, is generally constituted by a PWMIC (pulse width modulation switching IC) 13a produced by semiconductor integrated circuit technology. For example, PWMIC 13a is equiped with an R-S flip-flop FF, and has a comparator COM connected with a reset terminal R thereof, and further is equiped with a startup input terminal VH, a power input terminal Vcc, a feedback input terminal FB for the charging DC output side to provide feedback, an output terminal OUT for PWM driving of the first switching element 11 and the second switching element 12, a current input terminal IS for detecting the source current of the first switching element 11 and the second switching element 12, and a flip-flop input terminal FFS for inputting a set input signal and an output signal of latch circuit 18 to set terminal S of the R-S flip-flop FF. The functions of each terminal of PWMIC 13 a, which are appropriately achieved by a circuit provided within the PWMIC13a, are as follows. [0036] The flip-flop input terminal FFS detects the source current (source voltage) of the first switching element 11 or the second switching element 12 constituted by the power MOSFET, and detects the timing to turn on the first switching element 11 or the second switching element 12. Adjustments for the timing to turn on are conducted by adjustments to the time constants of resistance Rt and capacitor Ct. Furthermore, the terminal FFS stops the output pulse from the output terminal OUT of these PWMIC 13a by being pulled up by the latch circuit 18, and holds the stop state.

[0037] When voltage of the flip-flop input terminal FFS is lowered more than the designated threshold voltage, a set signal is input to R-S flip-flop FF, and the first switching element 11 or the second switching element 12 is turned on again. The first switching element 11 or the second switching element 12 can be turned on when the voltage is at the lowest point by suitably setting the delay time of the CR circuit in the resistance Rt and capacitor Ct that are connected to the auxiliary winding. [0038] Latch circuit 18 is added to the input terminal FFS, and the latch circuit 18 operates when an external signal exceeding the designated voltage has been input from the microcomputer 17 to the latch circuit 18 through fourth transmission unit 24 for more than the designated time. When the terminal FFS is clamped by the latch circuit 18, the output pulse of the output terminal OUT of the PWMIC 13a is stopped and this state is held. Reset is conducted by lowering the drive voltage Vcc to less than the threshold voltage.

[0039] Feedback input terminal FB is a terminal for feeding back an error in constant current or constant voltage of the charging circuit (including the third smoothing circuit 8 and the third switching circuit 35) formed at the secondary winding 10c side of the high frequency transformer 10 (see Fig. 2) through a third transmission unit 23, and also functions as a terminal for detecting an overload state.

[0040] Current input terminal IS detects the source current of the switching element 11 or the second switching element 12. The source current of the first switching element 11 or the second switching element 12 input to the current input terminal IS is input to the current comparator COM, and when the voltage reaches to the threshold voltage set in the terminal FB, the MOSFET (11 or 12) is turned off. Reference potential terminal GND is a terminal for giving the reference potential in order to set a voltage for each component in PWMICl 3a.

[0041] Output terminal OUT is a terminal for supplying a PWM drive signal to the gate terminal in MOSFET that constitute the first switching element 11 or the second switching element 12. For example, when an N-channel power MOSFET is used as the first switching element 11 or the second switching element 12, a high state (nearly the drive voltage Vcc) is output during the period for turning on MOSFET, and a low state (nearly the OV voltage) is output during the period for turning off MOSFET. [0042] Power input terminal Vcc is an input terminal for supplying the drive power to each component in PWMIC 13a. When using commercial power source 2, power input terminal Vcc applies the output voltage from the auxiliary winding in the transformer 10, which has been rectified and smoothed, to the each component . Auxiliary output winding 1Od for applying the voltage to the terminal FFS can be used as the auxiliary winding in transformer 10. Further, when using DC power source 3, power input terminal Vcc apply the DC voltage from DC power source 3 to the each component via the electric power supply line L3. [0043] Startup input terminal VH is connected, for example, with the electric power supply line Ll that is a supply line of power from AC power source 2 through the resistance. When a high voltage is applied to the VH terminal, current flows from the internal startup circuit ST in the PWMIC 13a through the terminal Vcc to the capacitor Cv connected between Vcc terminal-GND through, and the capacitor Cv is charged. When the voltage of the terminal Vcc exceeds the designated voltage, the PWMIC 13a starts up and starts the operation. When there is (drive voltage)Vcc applied from the auxiliary output winding 1Od, the internal startup circuit ST becomes an interrupted state. On the other hand, when there is no power supply from the auxiliary output winding 1Od, the PWMIC 13a performs the normal operation by the current supplied from the internal startup circuit ST. In such a manner, the PWMIC 13a has an internal startup circuit ST and enabling the apply of the drive voltage (Vcc) by only the internal startup circuit St in the event that the Vcc is not applied to the terminal Vcc.

[0044] This PWMIC 13a may be integrated on the circuit substrate together with peripheral circuits constituted by another discrete semiconductor circuit element, and is a component takes up a comparatively large occupancy in relation to the microcomputer 17. According to the present embodiment, this circuit component is held commonly for a plurality of input power sources.

[0045] Referring again to Fig. 2, the AC input voltage detection circuit 15 is a detection circuit for identifying the connection of the commercial power source (AC power) 2 to the AC connector 4, and DC input voltage detection circuit 16 is a detection circuit for identifying the connection of the DC power source 3 to the DC connecter 5. As the input power source for the charging device 1, either one of commercial power source 2 or DC power source 3 is selected based on the detected voltages of both detection circuits. [0046] A first switching unit 19 as well as a second switching unit 20 is a switching circuit connected respectively to the input winding 10a of the transformer 10 as well as input winding 10b of the transformer 10, and has a function to switch conduction (ON) or non-conduction (OFF) of the electric power supply line Ll or L3 (some cases may include L4) of the input circuit connected to each input winding 10a as well as 10b based on the detected signals of the AC input voltage detection circuit 15 and the DC input voltage detection circuit 16. The first switching unit 19 and the second switching unit 20 are constituted of relay switches 19a and 20a as shown in Fig. 3 A and B respectively. If the detected voltage is applied from the AC input voltage detection circuit 15 to the relay switch 19a, the electric power supply line Ll turns ON and the AC power source 2 is used as the input power source of the charging device 1 ; and if the detection voltage is applied from the DC input voltage detection circuit 16 to the relay switch 20a, the electric power supply line L3 turns ON, and the DC power source 3 is used as the input power source of the charging device 1.

[0047] A microcomputer 17 functions as the main control device of the charging device 1, and controls the switching control circuit 13, a fan motor drive circuit 33, a display circuit 34 and the like based on the output from the AC input voltage detection circuit 15, DC input voltage detection circuit 16, battery voltage detection circuit 25, identification resistance detection circuit 29, battery temperature detection circuit 30, and charging stop circuit 31. The latch circuit 18 can operate to stop the operation of the switching control circuit 13 based on the output signal transmitted from the microcomputer 17, and hold the top state as described above. [0048] A first transmission unit 21 as well as a second transmission unit 22 constituted of a photocoupler, respectively transmits the output of the AC input voltage detection circuit 15 as well as the DC input voltage detection circuit 16 to the microcomputer 17. [0049] A third transmission unit 23, also constituted of a photocoupler in the same manner as the first transmission unit 21 and the second transmission unit 22, transmits the output signals of the microcomputer 17 and the constant current/constant voltage control circuit 28 to the switching control circuit 13. At that time, the output signal of the microcomputer 17 is output to the third transmission unit 23 after being computed based on 5 the control signals that are input in advance to the microcomputer 17 from the identification resistance detection circuit 29, battery temperature detection circuit 30, and the charging stop circuit 31. By so doing, a start or stop of the operation of the first switching element 11 or the second switching element 12 is controlled, and further, the output pulse width of the first switching element 11 or the second switching element 12 is suitably controlled in

10 responding to the control signal that is fed back to the switching control circuit 13 from the third transmission unit 23.

[0050] On the other hand, a fourth transmission unit 24 constituted of, for example, a photocoupler has a function for transmitting the output signal of the microcomputer 17 to the latch circuit 18.

15 [0051] A battery voltage detection circuit 25 detects the battery voltage of the battery pack 40 during charging. Further, a charging current detection circuit 26 including, for example, a shunt resistance inserted to the charging path, detects the voltage generated by the charging current that runs through the charging current detection circuit 26. [0052] A current/voltage setting circuit 27 sets the value of a charging current and

20 charging voltage in order to charge the battery pack 40 based on the output from the microcomputer 17. The battery temperature detection circuit 30 detects the temperature of a rechargeable battery cell (unit cell) that constitute a unit cell group 42 based on the change of resistance of the heat sensitive element (for example, a thermistor) 46 of the battery pack 40 as described above. Further, the identification resistance detection circuit

25 29 detects the resistance value of the identification resistor 44 of the battery pack 40, and the microcomputer 17 determines the type of battery and unit cell count based on the detected the resistance value of the identification resistor 44 by the identification resistance detection circuit 29, and selects the set value of the charging current and charging voltage for the battery pack 40 corresponding to the determined battery type and the determined unit cell count in addition to the information of the battery temperature detection circuit 30. [0053] A constant current/constant voltage control circuit 28 outputs the signal for controlling the switching control circuit 13 based on the outputs from the battery voltage detection circuit 25, charging current detection circuit 26, and current/voltage setting circuit 27. As described above, the identification resistance detection circuit 29 outputs the signal based on the resistance value of the identification resistor 44 of the battery pack 40. The microcomputer 17 determines the type of battery and the unit cell count based on the output signal. Furthermore, a battery temperature detection circuit 30 detects the temperature of the unit cells in the battery pack 40 based on the resistance value of the heat sensitive element 46 of the battery pack 40.

[0054] The charging stop circuit 31 outputs the charge stop signal to the microcomputer 17 and the third switching unit 35 when an overcharge is detected by the overcharge detection circuit of the protection IC 41 in the battery pack 40, and the overcharge signal is output through the overcharge signal transmission unit 45 and the battery temperature terminal LS. A fan motor drive circuit 33 drives the fan motor 32 and prevents the temperature rise during charging of the battery pack 40. The fan motor drive circuit 33 is controlled based on the output signal from the microcomputer 17 that is output corresponding to a temperature condition of the battery pack 40 and the state of use of the commercial power source 2 or DC power source 3. For example, when the DC power from the DC power source 3 is supplied from a car battery in an automobile, such charging may be conducted within the car, so the operation of the fan motor 32 may be stopped. [0055] A display circuit 34 includes a display portion such as an LED (light emitting diode) for displaying the charge operation state of the charging device 1, and is driven by the control signal that is output by the microcomputer 17. The display circuit 34 includes, for instance, a red emitting LED and green emitting LED, and is designed so as to display, based on the control signal of the microcomputer 17, each state indicating: Before Charging by lighting only the red LED; Charging by lighting an essentially orange light by simultaneously lighting the red LED and green LED; and Charge Complete by lighting only the green LED. [0056] Furthermore, the display circuit 34 displays an input state of commercial power source 2 and DC power source 3 besides displaying the charging state of the battery pack 40. Moreover, when using the DC power source 3 as the input power source, the display circuit 34 displays an abnormal state of the power source when the DC power source 3 is not within the designated output voltage range. [0057] A third switching unit 35 switches the conduction (ON), non-conduction (OFF) of the charging path between the charging device 1 and the battery pack 40. [0058] The Operation of the Charging Device

A description will be given hereafter regarding the operation of the charging device 1 that relates to the present embodiment with reference to the circuit block diagram shown in Fig. 2 and the control flowchart shown in Fig. 5. The switching control circuit 13 starts up when the power from commercial power source 2 is input into the AC connector 4, the AC input voltage detection circuit 15 operates, and the first switching unit 19 brings the electric power supply line Ll into conduction. On the other hand, the switching control circuit 13 starts up when the power from DC power source 3 is input into the DC connector 5, the DC input voltage detection unit 16 operates, and the second switching unit 20 brings the electric power supply lines L3 and L4 into conduction.

[0059] Next, the switching control circuit 13 drives the first switching element 11 or the second switching element 12 and generates voltage to the output windings 10c and 1Od respectively connected with the third smoothing circuit 8 and the fourth smoothing circuit 9.

[0060] At this time, the output voltage Vcc of the fourth smoothing circuit 9 is controlled to the designated value by the activity of the constant voltage circuit 14 and applied as the drive voltage Vcc to the microcomputer 17 and the control system circuit. At the same time, the output signals from the battery voltage detection circuit 25 and the constant current/constant voltage control circuit 28 are fed back to the switching control circuit 13 through the third transmission unit 23, and the output voltage of the third smoothing circuit 8 is controlled to the designated value.

[0061] When the power from commercial power source 2 is input, voltage is also induced at the input winding 10b that corresponds to the DC power source 3 of the transformer 10, and the second switching unit 20 is a non-conducting state at this time so the induced voltage cannot be applied to the second smoothing circuit 7. Further, this induced voltage cannot be applied even to the plug of DC cable 5a (see Fig. 1).

[0062] In the same manner, when the power from the DC power source 3 is input, voltage is also induced at the input winding 10a that corresponds to the commercial power source 2 of the transformer 10, and because the first switching unit 19 is a non-conducting state at this time, the induced voltage cannot be applied to the first smoothing circuit 6 and the plug of AC cable 4a (see Fig. 1).

[0063] Moreover, with this embodiment, as shown in Fig. 1, when one cable (for example, the AC cable 4a) is plugged into the charging device 1, the slide plate 50 is provided to prevent the other cable (for example, the DC cable 5 a) from plugging into or making contact with the connector. [0064] After the microcomputer 17 starts up, the microcomputer 17 establishes the initial settings for each port (Step SlOl) and the like, causes the display circuit 34 to display "Before Charging" (Step S 102), and turns Off the third switching unit 35 (Step S 103). [0065] The microcomputer 17 determines the existence of an supply of the power from commercial power source 2 based on the output signal from the AC input voltage detection circuit 15 and the first transmission unit 21 (Step S 104). In Step S 104, if it is determined that the power from the commercial power source 2 is being supplied, then it continues to determine the existence of an supply of the power from DC power source 3 based on the output signal from the DC input voltage detection circuit 16 and the second transmission unit 22 (Step S 105).

[0066] If it is determined in Step S 105 that the power from DC power source 3 is not being supplied, the microcomputer 17 proceeds to AC mode (Step S 106). [0067] If it is determined in Step 104 that the power from commercial power source 2 is not being supplied (in the case of NO), then the microcomputer 17 continues to determine the existence of an supply of the power from DC power source 3 (Step S 107), and if it determines here that the power from DC power source 3 is being supplied, the microcomputer 17 proceeds to DC mode (Step S 108). [0068] Next, the microcomputer 17 determines whether there is an abnormality with the voltage applied from DC power source 3 (Step S 109), and if in Step 109 it is determined that there is no abnormality with the voltage applied from DC power source 3 then the microcomputer 17 proceeds to Step Sl 13. If it determines in Step 109 that there is an abnormality with the voltage applied from DC power source 3 (in the case of YES), the microcomputer 17 turns the third switching unit 35 Off (Step Sl 10) and causes the display circuit 34 to display "Power Error" (Step Si l l). By this, if the voltage is abnormally low in the DC power source 3, over discharging of the DC power source 3 is suppressed by prohibiting a charge to the battery pack 40. For example, if DC power source 3 is a car battery, such over discharging can be suppressed. [0069] If it is determined in Step S 105 that the power is being supplied from DC power source 3 (in the case of YES), the microcomputer 17 regards that both the power supplied from the commercial power source 2 and the power supplied from the DC power source 3 are being input at the same time and causes the latch circuit 18 to operate (ON) and causes the switching control circuit 13 to stop (OFF) (Step Sl 12). In this case, as described above, the switching control circuit 13 is held in a stopped state by the latching operation of the latch circuit 18 and the operation of the charging device 1 is held in a stopped state (OFF state). [0070] Moreover, according to the charging device 1 of the this embodiment, because the transformer 10 and the constant current/constant voltage control circuit 28 are provided in common for two input power sources (commercial power source 2 and DC power source 3), and because the output voltage of the third smoothing circuit 8 becomes unstable when the power is supplied from the both power sources, operation of the charging device 1 is controlled to forcefully stop in order to avoid this state. Further, if it is determined in Step S 107 that the power from DC power source 3 is not being supplied, the microcomputer 17 makes the latch circuit 18 to operate thereby stopping the switching control circuit 13 (Step S 112). The microcomputer 17 performs the process of step S 103 after performing the process of step 112.

[0071] After setting the input mode to either AC mode or DC mode in either Step 106 or Step 108, the microcomputer 17 determines the existence of the battery pack 40 (Step S 113), if it determines that the battery pack 40 is not connected to the charging device 1 , the charging complete flag is reset (Step Sl 14), and the charging flag is reset (Step Sl 15), and the microcomputer 17 returns to Step S 102.

[0072] When it is determined in Step S 113 that the battery pack 40 is connected to the charging device 1, then the microcomputer 17 determines the existence of the charging flag (Step Sl 16), and if the charging flag exists, the microcomputer 17 skips to step Sl 19. [0073] When it is determined in Step 116 that the charging flag does not exist, the microcomputer 17 continues to determine the existence of the charge complete flag (Step Sl 17), and if the charging complete flag exists, the microcomputer 17 returns to step S 103. [0074] Further, if the charging complete flag does not exist in Step Sl 17, the microcomputer 17 performs the battery type and unit cell count identification based on the output of the identification resistance detection circuit 29 (Step Sl 18), and then determines the battery temperature of the battery pack 40 based on the output of the battery temperature detection circuit 30 (Step Sl 19). When battery pack 40 is a high temperature, the microcomputer 17 causes the display circuit 34 to display "Battery High Temperature" (if high temperature during charging, then "Charging Complete") (Step S 120), and returns to Step S 103.

[0075] When it determines in Step Sl 19 that the battery pack 40 is not a high temperature (in the case of NO), the microcomputer 17 determines whether it is AC mode (Step S 121). When it determines in Step S 121 that it is not AC mode (in the case of NO), the microcomputer 17 proceeds to DC mode (Step S 124), and sets the current/voltage setting values of the DC mode (Step S 125).

[0076] In Step S 125, the optimal values for the current/voltage setting values are selected based on the output of the identification resistance detection circuit 29. More specifically, when the power is supplied from DC power source 3, the charging current is lowered compared to when the power is supplied from commercial power source 4. This is an important control in terms of matching the capacity of DC power source 3. Further, if the greater the unit cell count, the lower the charging current, a highly efficient power circuit can be devised which improves the life of the battery pack 40. After processing Step S125, the microcomputer 17 proceeds to Step 126, and causes the display circuit 34 to display "Charging".

[0077] When it is determined in Step S121 to be AC mode, the microcomputer 17 proceeds with the settings of the AC mode of Step S 122, and continues to set the current/voltage setting values of the AC mode (Step S 123). In Step S 123, the optimal values for the current/voltage setting values are selected based on the output of the identification resistance detecting circuit 29. More specifically, the charging current is set larger when the power is supplied from commercial power source 2 compared to when the power is supplied from DC power source 3. After processing Step S 123, the microcomputer 17 proceeds to Step S 126, and causes the display circuit 34 to display "Charging".

[0078] After processing Step S 123 or Step S 125, the microcomputer 17, at Step S 126, causes the display circuit 34 to display "Charging" , and then sets the charging flag (Step S 127), and switches the third switching unit 35 to a conducting state (Step S 128). Continuing to Step S 128, the microcomputer 17 begins charging at the designated current/voltage setting values selected at the preceding Step S 123 or Step S 125 (Step S129). [0079] Next, the microcomputer 17 performs the full charge detection process (Step S 130). Known art can be employed for the full charge detection. For example, in the case that the battery pack 40 includes lithium-ion rechargeable batteries, the charging voltage of the unit cell can be controlled so as not to be equal to or greater than a designated voltage value (for instance 4.2V) with a general constant voltage/constant current control. As another method, in the case of when the battery pack 40 includes a NiCd rechargeable batteries, the -ΔV detection method (minus delta V control method) to detect that the voltage has dropped by a predetermined amount from the peak voltage of the final stage of charging, and the ΔT/Δt detection method (temperature rise gradient control method) to detect the point in time that the battery temperature rise ratio (temperature gradient) per a prescribed time suddenly increases during charging as disclosed in Unexamined Japanese Patent Application KOKAI Publication No. S62-193518, Japanese Patent Application KOKAI Publication No. H2 -246739, and Unexamined Japanese Utility Model Application KOKAI Publication No. H3-34638, can be adopted. [0080] When it is determined in Step 130 that the battery pack 40 is not fully charged, the microcomputer 17 returns to Step S 104. When it is determined in Step S 130 that the battery pack 40 is fully charged, the microcomputer 17 resets the charging flag (Step S131), and causes the display circuit 34 to display "Charging Complete" (Step S 132), performs the setting of the charge complete flag (Step S 133) and each process, and returns to Step S103. [0081] According to the present embodiment and as is evident from the description given in the above embodiment, because the high frequency transformer 10 and the switching control circuit 13 are commonly constituted for a plurality of input power sources 2 and 3, the circuit part count for the transformer and switching control circuit and so forth for the charging device 1 is small and the manufacturing cost of the charging device 1 is low.

[0082] The capacity of the high frequency transformer 10 used in common for a plurality of input power sources can be formed to be larger than those used in conventional technique The larger capacity of the high-frequency transformer improves the power conversion efficiency, and supplies heat generation from the charging device, and as a result, the power consumption of this charging device is low. Particularly, with a car battery as the input power source, power consumption of the DC power source 3 can be suppressed, and the discharge life of the car battery can be maintained when the power consumption from the DC power source is low.

[0083] Further, a charging device 1 can be provided in a smaller size, and therefore the device is advantageous in transportation to a work site. Particularly, the present invention is advantageous with respect to the point of being that can reduce the size of a carrying case by applying to a charging device for transporting in one piece with electric power tools and storing in the carrying case of cordless electric power tools.

[0084] Further, according to this embodiment, because the switching circuit 19 or 20 is connected to the switching power supply circuit electrically connected to the input winding 10a or 10b of a common transformer 10, the electric power from each input power source 2 or 3 can be selectively supplied to the input winding 10a or 10b. Therefore, mutual interference of the plurality of input power sources based on electromagnetic coupling by a common transformer 10 can be prevented. Further, according to this embodiment, because the latch circuit 18 is provided, error operation can be prevented by the operation of the latch circuit 18 when the plurality of power is input from the plurality of input power sources of commercial power and DC power at the same time.

[0085] A detailed description is provided above of an invention according to the present inventors based on an embodiment; however, the present invention is not limited to the above embodiment, and modification within the range that does not deviate from such essence is possible. For example, in the embodiment, a description is given regarding a charging device 1 in which the battery pack 40 includes a lithium-ion rechargeable battery; however, the present invention can also apply to a charging device of a battery pack includes a NiCd rechargeable battery or the like.

[0086] Having described and illustrated the principles of this application by reference to one preferred embodiment, it should be apparent that the preferred embodiment may be modified in arrangement and detail without departing from the principles disclosed herein and that it is intended that the application be construed as including all such modifications and variations insofar as they come within the spirit and scope of the subject matter disclosed herein.

[0087] This application claims the benefit of Japanese Patent Application No.2008-331966 filed on December 26, 2008, the entire disclosure of which is incorporated by reference herein.

Claims

Claim 1. A charging device that charges a battery pack by power supplied from either one of two input power sources, comprising: a transformer including two input windings provided to correspond to respective ones of the two input power sources, as well as including a charging output winding to output a charging power voltage by being electromagnetically coupled to the two input windings; first and second switching elements for switching current that flows to each input winding, each switching element being connected with each input winding of the transformer; a charging circuit for outputting a charging current or a charging voltage to the battery pack by being coupled with the charging output winding of the transformer; and a switching control circuit for commonly controlling the first and second switching elements .

Claim 2. The charging device according to claim 1, further comprising: a control unit for setting the charging current or the charging voltage of the charging circuit corresponding to the type of the two input power sources and outputting a control signal corresponding to the set charging current or the set charging voltage; wherein the switching control circuit commonly controls the first and second switching elements based on the control signal output from the control unit.

Claim 3. The charging device according to claim 1, wherein the transformer includes an auxiliary output winding for outputting power voltage to the electric circuit within the charging device.

Claim 4. The charging device according to claim 1, further comprising; two input voltage detection units for detecting the respective voltage inputted to each input winding of the transformer, and two switching units provided for alternatively switching electric power transmission lines, to the first and second switching elements, coupled to each input winding based on the output of the input voltage detecting unit, to be brought into a conducting or a non-conducting state.

Claim 5. The charging device according to claim 1 , wherein the two input power sources are electrically connected detachably, by power cables with mutually differing appearance profiles, with corresponding connection terminals.

Claim 6. The charging device according to claim 1, further comprising: two connection terminals for electrically being connected with respective ones of two input power sources; a connection prohibiting unit for preventing other connection terminal than the connection terminal that is alternately electrically connected to the corresponding input power from being connected to the corresponding input power.

Claim 7. The charging device according to claim 5, wherein the connection prohibiting unit comprises a shielding plate which covers the other connection terminal.

Claim 8. The charging device according to claim 1, wherein one input power source among the two input power sources is a commercial AC power source.

Claim 9. The charging device according to claim 2, wherein the control unit includes a latch circuit for stopping the switching control circuit when determining that the two input power sources are electrically connected with the charging device.