JP2010114958A - Charger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charger capable of unfailingly and easily preventing a secondary battery from being an overcharged state even when the mounted secondary battery cannot be recognized. <P>SOLUTION: When the battery voltage sampled per predetermined time by a battery voltage detection circuit 5 is dropped by not less than a predetermined value from the maximum value, the maximum voltage value so far is reset and a newly detected voltage value is used as the new maximum voltage value, and if a further voltage drop by not less than a predetermined value from the new maximum voltage value is detected, a switching power supply is stopped. If a second voltage drop is not detected or if voltage increase of not less than the predetermined value is detected, the power supply is not stopped but returns to processing of determining whether the battery is mounted or not. Thus, even if erroneous charging is executed when a failure occurs in a function for turning ON-OFF the connection of a battery temperature detecting circuit 3 or a power supply circuit 6, the charging can be safely and unfailingly stopped. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a charging device for charging a secondary battery used in an electric tool.

Conventionally, in a charging device, for example, a current detection unit for detecting a charging current on the charging device side is provided, and when the charging current is detected when the mounting of the battery is not recognized, The configuration is such that unexpected charging is avoided by adopting a configuration in which power is supplied to the secondary battery and the charging circuit is stopped. (For example, refer to Patent Document 1).
JP 2008-193797 A

  However, the provision of the current detection means requires a dedicated circuit for current detection and a control circuit associated with current detection, and there is a problem in that the entire apparatus is increased in size and cost.

  Therefore, the present invention provides that the secondary battery is erroneously charged and falls into an overcharged state due to a failure of the function of recognizing the mounting of the battery in the charging device or the function of supplying charging power to the secondary battery. An object of the present invention is to provide a charging device that can be surely easily, safely and inexpensively prevented.

  In order to achieve the above object, the invention described in claim 1 is a charging device for charging a battery, wherein the battery voltage detecting means for detecting the battery voltage, and the voltage value detected by the battery voltage detecting means are obtained. Storage means for storing; battery mounting determining means for determining whether or not the battery is mounted on the charging device; and operating by receiving power supply from an external power source, and the battery is mounted by the battery mounting determining means A power supply means for supplying power to the battery when it is determined that there is a power supply stop means for stopping power supply from the external power supply to the power supply means, a control means for controlling the operation of the charging device, The control means includes a voltage detection control means for causing the battery voltage detection means to detect a voltage value, a voltage value storage control means for storing the voltage value detected by the battery voltage detection means, and a battery in the battery mounting determination means. Implemented A voltage change determining means for determining that the voltage value detected by the battery voltage detecting means has changed, and when the voltage change determining means detects a change in the voltage value, And a power stop control means for operating the stop means.

  According to such a configuration, the power supply means supplies power from the external power source to the battery when it is determined that the battery is mounted. When the battery mounting determination means determines that the battery is not mounted and the battery voltage changes, the power supply from the external power supply to the power supply means is stopped by operating the power supply stop means.

  According to a second aspect of the present invention, in the charging device according to the first aspect, the voltage storage control means stores the voltage value detected by the battery voltage detection means in the storage means, and the highest voltage value among the detected voltage values. The value is stored as a maximum voltage value, the voltage change determination means determines that the voltage value detected by the battery voltage detection means has dropped by a predetermined value or more than the maximum voltage value, and the power stop control means determines the voltage change When the means detects a voltage drop of a predetermined value or more, the power supply stop means is activated.

  According to such a configuration, when a voltage drop of a predetermined value or more with respect to the maximum voltage value among the battery voltage values stored by the storage unit is detected, the secondary battery is erroneously charged and the battery is overcharged. The charging is stopped by determining that the power supply from the external power supply to the power supply means is stopped.

  According to a third aspect of the present invention, in the second aspect of the present invention, the control means is configured such that the voltage change determining means determines that the voltage value detected by the battery voltage detecting means has dropped by a predetermined voltage from the maximum voltage value. If determined, the maximum voltage value resetting means for deleting the storage of the maximum voltage value from the storage means, and the voltage value detected by the voltage detection means immediately after the maximum voltage value resetting means deletes the storage of the maximum voltage value, And a maximum voltage value updating means for storing the new maximum voltage value in the storage means, wherein the power stop control means is configured such that the voltage value detected by the voltage detection means after the new maximum voltage value is stored is the new maximum voltage value. The power supply stopping means is actuated when it is determined that the value has dropped from the value by a predetermined value or more.

  According to such a configuration, once it is determined that there is a voltage drop of a predetermined value or more, the maximum voltage value is reset, and when a predetermined voltage drop is detected with reference to the voltage immediately after the reset, charging is stopped.

  According to the charging device of the first aspect of the present invention, the power supply path to the secondary battery is connected when the battery mounting is not recognized due to a failure such as poor contact between the power supply means and the terminals. If the battery voltage value changes due to the presence of the battery, it can be determined that there is a case where unintended charging may be performed, and the power supply stopping means can be operated to stop the charging. Therefore, the situation where a secondary battery is charged accidentally is avoided. In addition, since a current detection circuit for detecting a current on the charging path and a control circuit for stopping charging based on the detected current are not required, the entire apparatus can be reduced in size and cost can be reduced. Can do.

  According to the charging device of claim 2 of the present invention, in addition to the above effect, the maximum voltage value even when the power supply path to the secondary battery is always connected due to failure regardless of whether or not the battery is mounted. If it is determined that there is a case where unintended charging may be performed when a voltage drop of a predetermined value or more is detected from charging, the charging can be stopped by stopping the power supply from the external power supply to the power supply means. Therefore, a situation in which the secondary battery is overcharged and fails is avoided.

  According to the third aspect of the present invention, in addition to the above effect, even if it is determined that there is a voltage drop of a predetermined value or more, the power supply is not stopped immediately, but the maximum voltage that has already been stored. Reset the value. Furthermore, power supply is stopped when a predetermined voltage drop is detected with respect to the voltage immediately after the reset. As a result, when the user notices that the secondary battery is not installed and detects a voltage drop exceeding a predetermined value that occurs when the battery is removed, the power supply is unnecessarily supplied. It can be prevented from stopping. Therefore, it is possible to reliably stop charging in the event of a failure without falling into a situation where charging cannot be performed unless the connection with the external power source is once disconnected even though there is no failure in the charging device.

  Hereinafter, a charging device according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram showing a charging device 100 according to an embodiment of the present invention. As shown in FIG. 1, the charging device 100 is a charging device that is supplied with power from the AC power source 1 and charges the battery pack 2 connected to the output side.

  The AC power source 1 is an external power source such as a commercial power source. The battery pack 2 includes a plurality of unit cells connected in series, and includes a thermistor 2a and a battery type discrimination resistor 2b. The thermistor 2a is a temperature sensitive element for detecting the battery temperature of the unit cell. The battery type discrimination resistor 2b is a discrimination resistor for discriminating the type of the battery based on a voltage change when the battery pack 2 is attached to the charging device 100. The battery type here is, for example, a nickel-cadmium battery if the battery type discrimination resistor 2b is a resistance X, or a nickel metal hydride battery if the resistance is Y. The battery type is not limited to the above-mentioned nickel-cadmium battery or nickel-metal hydride battery.

  The charging device 100 includes a primary side rectifying / smoothing circuit 10, a switching power supply 20, a high frequency transformer 21, a secondary side rectifying / smoothing circuit 30, a charging current control circuit 60, a charging voltage control circuit 70, a photocoupler 8, and a SW control IC stop signal transmission. A circuit 9, a power supply circuit 6, and a power supply control circuit 7 are included, and the operation is controlled by the microcomputer 50.

  The primary-side rectifying / smoothing circuit 10 includes a full-wave rectifying circuit 11 and a smoothing capacitor 12, and rectifies and smoothes the AC input from the AC power supply 1 and outputs the AC. The switching circuit 20 includes an N-channel MOSFET 22, a SW control IC 23, a starting resistor 24, a SW control IC constant voltage circuit 25, and a SW control IC stop circuit 26. The switching circuit 20 is a circuit for controlling the output to the primary side coil of the high frequency transformer 21 by adjusting the timing for switching the output of the primary side rectifying and smoothing circuit 10 or the like.

  The high-frequency transformer 21 includes a primary winding 21a, a secondary winding 21b, a tertiary winding 21c, and a quaternary winding 21d, and the secondary winding is applied to the primary winding 21a to which a switched input voltage is applied. The winding 21b is an output winding for driving the SW control IC 23, the tertiary winding 21c is an output winding for charging the battery pack 2, and the fourth winding 21d is an output winding for a control system power source such as the microcomputer 50. It is. In addition, with respect to the primary winding 21a, the secondary winding 21b, the fourth winding 21d have the same polarity, and the tertiary winding 21c has the opposite polarity. The primary side rectifying / smoothing circuit 10, the switching circuit 20, and the high-frequency transformer 21 function as a switching power supply.

  In the switching circuit 20, the starting resistor 24 and the SW control IC 23 are connected in series to each other on the output side of the primary side rectifying and smoothing circuit 10. The start resistor 24 is a resistor for starting the SW control IC 23 by inputting the output of the primary side rectifying and smoothing circuit 10 to the SW control IC 23. The SW control IC 23 is a SW power supply IC that adjusts the output voltage by changing the drive pulse width of the MOSFET 22. A feedback signal corresponding to a charging current and a charging voltage for controlling the switching timing is input from the photocoupler 8 to the SW control IC 23. The SW control IC 23 receives a constant voltage for driving from the constant voltage circuit 25. The output terminal of the SW control IC 23 is connected to the gate of the MOSFET 22 and controls the MOSFET 22 by a pulse signal at a predetermined timing. The drain of the MOSFET 22 is connected to the output side of the primary winding 21 a of the high-frequency transformer 21, and the source is connected to the negative side output of the primary side rectifying and smoothing circuit 10.

  The SW control IC constant voltage circuit 25 includes a diode 25a, a capacitor 25b, a resistor 25c, an NPN transistor 25d, and a Zener diode 25e. The diode 25a and the capacitor 25b are connected to both ends of the secondary winding 21b while being connected in series with each other. The collector of the NPN transistor 25d is connected to the cathode side of the diode 25a, the gate is connected to the Zener diode 25e and the drain of the FET 26f of the SW control IC stop circuit 26, and the emitter is connected to the SW control IC 23. Further, a resistor 25c is connected between the collector and gate of the NPN transistor 25d.

  After the power is supplied from the AC power source 1, the SW control IC constant voltage circuit 25 is operated during normal driving (hereinafter referred to as normal time) in which the switching operation of the SW control IC 23 described later is driven without stopping. A voltage corresponding to the sum of the voltage between the Zener diode 25e and the base-emitter of the NPN transistor 25d of about 0.6 volts is applied to the SW control IC 23, and the SW control IC 23 performs a switching operation using this voltage as a power source. For the Zener diode 25e, the power supply voltage of the SW control IC 23 is selected so as to sufficiently satisfy the value.

  The SW control IC stop circuit 26 includes a resistor 26a, a photocoupler receiver 26b (transmitter 9a), a Zener diode 26c, a P-channel FET 26d, an N-channel FET 26e, and an FET 26f. The input side of the resistor 26 a is connected to the output side of the primary side rectifying and smoothing circuit 10. The output side of the resistor 26a is connected to the photocoupler receiver 26b, the source of the FET 26d, and the Zener diode 26c. The gate of the FET 26d is connected to the drain of the FET 26e, and the drain of the FET 26d is connected to the gate of the FET 26e and the gate of the FET 26f. The source of the FET 26e, the source of the FET 26f, and the anode of the Zener diode 26c are connected to the negative side output of the primary side rectifying and smoothing circuit.

  In the normal time, the SW control IC stop circuit 26 is not operating, but operates when the receiving unit 26b is turned on by a signal from the SW control IC stop signal transmission circuit 9 described later. That is, when the receiving unit 26b is turned on, the output voltage rectified by the primary side rectifying and smoothing circuit 10 is applied to the gate of the FET 26e and the gate of the FET 26f via the resistor 26a and the receiving unit 26b, and the FET 26e and FET 26f are turned on. It becomes a state. Similarly, when the output voltage of the primary side rectifying / smoothing circuit 10 is applied to the Zener diode 26c via the resistor 26a, a value corresponding to the Zener voltage of the Zener diode 26c is applied to the source of the FET 26d. Further, the FET 26d is turned on by applying a potential between the drain and gate of the FET 26e in the on state between the gate and drain of the FET 26d.

  The SW control IC 23 is in an operating state when a voltage corresponding to the sum of about 0.6 V between the base-emitter voltage of the Zener diode 25e and the transistor 25d is applied. As described above, the FET 26f is turned on. In other words, the Zener diode 25e is short-circuited by being turned on. For this reason, the voltage applied to SW control IC23 falls and falls to about 0.6V. When the voltage applied to the SW control IC 23 falls below the voltage necessary for the operation of the SW control IC 23, which is about 0.6V, the SW control IC 23 naturally stops the switching operation.

  When the SW control IC 23 stops in this way, the signal from the transmission side 9b of the photocoupler is not transmitted, so that the receiving unit 26b is turned off. However, in the present embodiment, after the receiving unit 26b is once turned on, the output of the primary side rectifying / smoothing circuit 10 is turned on with the resistor 26a regardless of whether the receiving unit 26b is on or off. It is maintained by the path of the FET 26d and the FET 26e that are in the state. Therefore, a voltage corresponding to the sum of about 0.6 V between the base diode and the emitter of the Zener diode 25e and the transistor 25d is not applied to the SW control IC 23 again, and the operation state is not brought about. However, the OFF state of the SW control IC 23 is released by turning off the connection between the AC power source 1 and the charging device 100 by an operation such as pulling out the outlet, and the AC power source 1 and the charging device 100 are connected again. For example, the normal operation is resumed.

  A secondary side rectifying and smoothing circuit 30 is connected to the output side of the tertiary winding 21 c of the high frequency transformer 21. The secondary side rectifying / smoothing circuit 30 includes a diode 31, a smoothing capacitor 32, and a resistor 33, and rectifies and smoothes the output of the tertiary winding 21c. The diode 31 and the smoothing capacitor 32 are connected in series to each other and are connected to both ends of the tertiary winding 21c. The resistor 33 is connected in parallel to the smoothing capacitor 32.

  The charging voltage control circuit 70 includes a resistor 70a and a Zener diode 70b, and is a circuit for feeding back a signal for controlling the charging voltage to the SW control IC 23 via the photocoupler 8. The resistor 70a and the Zener diode 70b are connected in series with each other, the input side of the resistor 70a is connected to the output side of the secondary side rectifying / smoothing circuit 30, and the output side of the Zener diode 70b is connected to the photocoupler 8. It is connected. The value of the Zener diode 70b determines the charging voltage. When a voltage equal to or higher than the Zener voltage is applied from the secondary-side rectifying and smoothing circuit 30 to the Zener diode 70b, the charging voltage control circuit 70 outputs a voltage control signal for suppressing the voltage to the photocoupler 8 serving as a signal transmission unit. Thus, the charging voltage is controlled.

  The charging current control circuit 60 includes resistors 60a, 60b, 60c, 60d, 60e, and 60f, an operational amplifier 60g, a diode 60h, and a shunt resistor 60i, and performs SW control of a signal for controlling the charging current via the photocoupler 8. This is a circuit for returning to the IC 23. The resistors 60a and 60b are connected in series between the voltage Vcc and the reference potential point. The input side of the resistor 60c is connected in series to the output side of the resistor 60a, and the output side of the resistor 60c is connected to the inverting terminal of the operational amplifier 60g and to the resistor 60d. A resistor 60e is connected to the non-inverting input terminal of the operational amplifier 60g, and the shunt 60i is connected between the resistor 60d and the resistor 60e. The output side of the operational amplifier 60g is connected to the photocoupler 8 via a resistor 60f and a diode 60h connected in series with each other.

  With the above configuration, a predetermined voltage is generated at the connection point between the resistor 60c and the resistor 60d and applied to the inverting input terminal of the operational amplifier 60g. The resistor 60e is connected between the non-inverting input terminal of the operational amplifier 60g and the output from the battery pack 2, and a current corresponding to the charging current flowing through the battery pack 2 flows into the resistor 60e according to the charging current of the battery pack 2. The voltage is applied to the non-inverting input terminal of the operational amplifier 60g. When the operational amplifier 60g outputs a voltage corresponding to the difference between the voltages applied to the two input terminals, the output voltage is output to the SW control IC 23 via the resistor 60f, the diode 60h, and the photocoupler 8 according to the output of the operational amplifier 60g. When the signal to be suppressed is input, the output voltage of the primary winding 21a is controlled, and the charging of the battery pack 2 is controlled with constant current.

  The photocoupler 8 is a signal transmission unit that feeds back the voltage control signal from the charging voltage control circuit 70 and the current control signal from the charging current control circuit 60 to the SW control IC 23.

  The charging device 100 includes a constant voltage circuit 40 for operating the microcomputer 50. The battery pack 2 further includes a battery temperature detection circuit 3 connected to the thermistor 2a, a battery type determination circuit 4 connected to the battery type determination resistor 2b, and a battery voltage detection circuit 5 for detecting the battery voltage.

  The constant voltage circuit 40 includes a diode 41, capacitors 42 and 44, a three-terminal regulator 43, and a reset IC 45. The first terminal of the three-terminal regulator 43 is connected to the quaternary winding 21 d via the diode 41 and connected to the reference potential point via the capacitor 42. The second terminal of the three-terminal regulator 43 is connected to the reference potential point, the third terminal is connected to the reference potential point via the capacitor 44, is connected to the potential point of the voltage Vcc, and is further connected to the microcomputer 50. ing. The reset input port 54 is connected between the voltage Vcc and the reference potential point. The constant voltage circuit 40 converts the output of the quaternary winding 21d into a predetermined voltage Vcc and outputs it as a power source for the microcomputer 50 or the like. The reset IC 45 outputs a reset signal to the reset input port 54 of the microcomputer 50 in order to put the microcomputer 50 into an initial state.

  The microcomputer 50 includes a CPU 51, an A / D port 52, output ports 53 a and 53 b, and a reset port 54, and controls the operation of the charging device 100. The A / D port 52 receives signals from the battery temperature detection circuit 3, the battery type determination circuit 4, and the battery voltage detection circuit 5. The output port 53 a outputs a signal for controlling whether or not the charging current is supplied to the battery pack 2 to the power supply control circuit 7. The output port 53b outputs a signal for lighting the LED 80 to indicate that the battery is being charged.

  The battery temperature detection circuit 3 includes a resistor 3a and a resistor 3b connected in series between the voltage Vcc and the reference potential. When the battery pack 2 is not mounted on the charging device 100, the microcomputer 50 outputs a value obtained by dividing the voltage Vcc by the resistors 3a and 3b. When the battery pack 2 is connected to the charging device 100, the thermistor 2a is arranged in parallel with the resistor 3b, and the voltage Vcc is divided by the resistor 3a and the parallel resistance of the resistor 3b and the thermistor 2a. Is output. Therefore, a voltage corresponding to the battery temperature is output to the A / D port 52. Further, as described above, a constant voltage value is output before mounting the battery, and an output corresponding to the battery temperature is output after mounting. Therefore, the microcomputer 50 determines mounting of the battery pack 2 based on the change in the output.

  The battery type discriminating circuit 4 has a resistor 4a connected to the voltage Vcc. When the battery pack 2 is mounted on the charging device 100, the battery pack 2 is connected to the battery type discrimination resistor 2b, and a voltage obtained by dividing the voltage Vcc by the resistor 4a and the battery type discrimination resistor 2b is output to the A / D port 52. As a result, a voltage corresponding to the type of battery is output to the A / D port 52.

  The battery voltage detection circuit 5 includes resistors 5a and 5b. When the battery pack 2 is mounted, a battery voltage is input to the input side of the resistor 5a. The output side of the resistor 5a is connected to the microcomputer 50 and is connected to a reference potential via the resistor 5b. The battery voltage of the battery pack 2 is detected by dividing the voltage by the resistor 5 a and the resistor 5 b in the battery voltage detection circuit 5 and inputting the value to the A / D port 52 of the microcomputer 50.

  The power supply circuit 6 is power supply means for supplying power from the charging device 100 to the battery pack 2. The power supply circuit 6 includes a relay as an example, but is not limited thereto. The power supply circuit 6 switches presence / absence of power supply from the charging device 100 to the battery pack 2 according to a signal from the power supply control circuit 7.

  The power supply control circuit 7 is power supply control means for controlling the power supply circuit 6. The power supply control circuit 7 controls the power supply circuit 6 by a signal from the output port 53 a of the microcomputer 50.

  The SW control IC stop signal transmission circuit 9 is a signal transmission means including a photocoupler transmission unit 9a (reception unit 26b), an FET 9b, and the like for transmitting a signal for stopping the SW control IC 23 itself. The anode side of the transmission unit 9a is connected to the output of the rectifying / smoothing circuit 30, and the cathode side is connected to the drain of the FET 9b. A signal from the output port 53b of the microcomputer 50 is input to the gate of the FET 9b, and the FET 9b is controlled by the signal. As will be described later, when it is determined that some failure has occurred in the charging apparatus 100, the microcomputer 50 outputs a predetermined signal from the output port 53b to turn on the FET 9b. When the FET 9b is turned on, the signal is transmitted to the SW control IC stop circuit 26 via the receiving unit 26b by the light emitting of the transmitting unit 9a of the photocoupler as described above.

  The LED 80 is an LED for displaying a charging state. The LED 80 is turned on and off by a signal from the output port 53b of the microcomputer 50. In the present embodiment, it is assumed that the LED 8 is being charged when it is lit and is not being charged when it is not lit.

  Next, an example of charging operation control of the charging device 100 according to the present embodiment will be described with reference to the flowchart of FIG. First, when the power is turned on, the microcomputer 50 initially sets the output port 53a and the output port 53b. Next, it is determined whether or not the battery pack 2 is connected to the charging device 100 (step 201). For example, as described above, the battery is connected when the value of the A / D port 52 of the microcomputer 50 input via the battery temperature detection circuit 3 is changed. If it is determined in step 201 that a battery has been installed, the LED 80 is turned on to display that charging is in progress (step 202). The LED 80 is turned on by a signal from the output port 53b of the microcomputer 50. Next, charging is started (step 203). Charging is started by controlling the power supply circuit 6 from the output port 53 a of the microcomputer 50 via the power supply control circuit 7 and supplying charging power to the secondary battery pack 2.

  Thereafter, it is detected whether or not the battery is fully charged (step 204). There are various detection methods for determining full charge. For example, in the −ΔV detection method, it is determined that the battery is fully charged by detecting that a predetermined amount has dropped from the peak voltage at the end of charging based on the output of the battery voltage detection circuit 5. The second-order differential detection method aims to reduce overcharge by stopping charging before the battery voltage reaches a peak, and to improve the cycle life of the battery. It is determined that the battery is fully charged by detecting a negative point. Further, in the ΔT detection method, based on the output of the battery temperature detection circuit 3, it is determined that the battery temperature rise value from the start of charging is equal to or higher than a predetermined temperature rise value, and is determined to be fully charged. Further, the dT / dt detection method is disclosed in Japanese Patent Application Laid-Open No. 62-193518, Japanese Patent Application Laid-Open No. 2-246739, Japanese Utility Model Laid-Open No. 3-34638, and the like. It is determined that the rate of increase (temperature gradient) is greater than or equal to a predetermined value and is fully charged. The full charge detection may be performed using one or more of the methods described above, but is not limited thereto.

  After detecting the full charge, the charging is terminated (step 205). Charging is terminated by controlling the power supply circuit 6 from the output port 53a of the microcomputer 50 via the power supply control circuit 7 and stopping the supply of charging power to the battery pack 2.

  Thereafter, the LED 80 is turned off by a signal from the output port 53b of the microcomputer 50 (step 206). In the present embodiment, the end of charging is indicated by turning off the LED 80. Thereafter, when it is detected that the battery pack 2 is removed from the charging apparatus 100 (step 207), the process returns to step 201.

  In the above control, the charging device 100 recognizes that the battery pack 2 is mounted and performs charging control until the end of charging when charging is performed without stopping the switching power supply (hereinafter referred to as normal charging). This is a flow of

  Next, the case where it is not recognized in step 201 that the battery mounting is mounted will be described. If it is determined in step 201 that the battery is not mounted, it is first determined in step 208 whether or not the voltage drop flag is 1. Although the voltage drop flag will be described later, this flag is not 1 unless a voltage drop has already been detected, so the routine proceeds to step 209 here. In step 209, the battery voltage is taken into the A / D port 52 of the microcomputer 50 at every predetermined sampling time via the battery voltage detection circuit 5. At that time, the microcomputer 50 specifies the maximum value among the battery voltages taken in every predetermined sampling time from the A / D port 52, stores it as the maximum voltage value, and updates it (step 210). .

  Next, in step 211, whether or not the current (that is, the latest) battery voltage value taken in every predetermined sampling time has dropped by a predetermined value or more from the maximum voltage value updated at any time in step 210. Is discriminated (step 211). When the battery pack 2 is not actually mounted, since the battery voltage is not detected, the voltage value does not drop naturally, and the voltage value does not drop below the maximum voltage value in step 211 (step 211: NO). Therefore, the process returns to step 201 again to determine whether or not a battery is mounted. When the battery is not mounted as described above, the above-described operation is repeated until the battery mounting is detected in step 201.

  Next, let us consider a case where the battery mounting is not recognized in step 201 for some reason even though the battery is mounted. As an example of a case where the battery temperature cannot be recognized, a failure of the battery temperature detection circuit 3 can be considered. Further, as in the present embodiment, the thermistor 2a provided on the battery pack 2 side and the battery temperature detection circuit 3 on the charging device 100 side are connected through terminals by mounting the battery pack 2, and at that time If the mounting of the battery is recognized by the change in the value of the battery temperature detection circuit 3, for example, a contact failure of the connection terminal between the thermistor 2a and the battery temperature detection circuit 3 at that time may be considered.

  Since battery mounting is not recognized in step 201, the process proceeds to step 208 to determine whether or not the voltage drop flag is 1. The voltage drop flag will be described later. Since this flag is not 1 unless a voltage drop has already been detected, the process proceeds to step 209. In step 209, the battery voltage is taken into the A / D port 52 of the microcomputer 50 at every predetermined sampling time via the battery voltage detection circuit 5. At that time, the microcomputer 50 specifies the highest value among the battery voltages taken in every predetermined sampling time from the A / D port 52, stores it as the maximum voltage value, and updates it (step 210).

  Next, in step 211, it is determined whether or not the current battery voltage value taken in every predetermined sampling time has dropped by a predetermined value or more from the maximum voltage value of the voltage value updated at any time in step 210. (Step 211). As described above, when the battery pack 2 is mounted but the battery mounting cannot be recognized, only the battery voltage is detected, and the voltage value does not drop naturally. The voltage value does not drop below the maximum voltage value. Therefore, the process returns to step 201 again to determine whether or not the battery pack 2 is mounted.

  However, when the battery is not recognized on the charging device 100 side even though the battery pack 2 is attached, the LED 80 indicating that charging is in an off state, and the user notices an abnormality, and somewhere There is a high possibility that the battery pack 2 is removed from the charging device 100 at the time of. In that case, the voltage detected by the battery voltage detection circuit 3 drops to zero at once from the battery voltage immediately before the battery is removed.

  Here, the properties of the secondary battery used in the present embodiment will be described with reference to the charging graph of FIG. FIG. 3 shows the battery voltage change during charging when the horizontal axis is time t and the vertical axis is battery voltage V. In general, the battery voltage of a nickel cadmium battery or a nickel metal hydride battery increases as the battery is charged as shown in FIG. After that, the voltage does not increase when it is near full charge (near time t = t1), and the voltage becomes flat and gradually decreases. Generally, as described above, when the battery voltage becomes flat without increasing, or when the voltage starts to decrease, it is determined that the battery is fully charged, and charging is stopped. If charging continues without stopping charging at this point, the voltage continues to drop, eventually becoming overcharged and causing a battery failure.

  As described above, if charging is performed even though battery mounting is not recognized, it is considered that there is a failure in the battery mounting recognition function and the power supply function. On the other hand, if the battery is charged, the battery voltage should drop after full charge. By detecting this and stopping the charge, it is possible to safely stop the charge even when the charging device is faulty. be able to.

  Here, consider a case where the mounting of the battery is not recognized due to, for example, a contact failure between the connection terminals on the battery pack 2 side and the charging device 100 side. In this case, as described above, since the LED 80 indicating that charging is in the off state, the user notices an abnormality and is likely to remove the battery pack 2 at some point. If the battery pack 2 is removed, the value of the battery voltage detection circuit 5 drops from the battery voltage value to zero at once. Considering the case where switching is stopped by detecting this voltage drop, as described in the explanation of FIG. 1, in this embodiment, once switching is stopped, the voltage of the AC power source 1 is stopped. Unless it is removed (unless the AC power supply is removed), the operation control state in which normal charging is possible cannot be restored. That is, when the contact of the terminal between the battery pack 2 and the charging device 100 is poor and the LED 80 does not light (cannot be charged), the battery pack 2 is pulled out once and the terminal is contacted accurately. Even if it makes it, it will fall into the state which cannot be charged, if connection with the alternating current power supply 1 is once canceled.

  Therefore, in this embodiment, after a predetermined voltage drop is detected in step 211, the voltage drop flag is set to 1 in step 212 (the voltage drop flag becomes 1 when the voltage drops once to a predetermined value). Thereafter, the maximum voltage value stored / updated in step 210 is reset once (step 213), the voltage immediately after the reset is detected by the battery voltage detection circuit 5, and stored as a new maximum voltage value in the microcomputer 50 (step 213). 214). Further, the battery voltage detection circuit 5 starts detecting the battery voltage every predetermined sampling time (step 215). In step 216, it is determined whether or not the current battery voltage detected in step 215 has dropped by a predetermined value or more from the new maximum voltage value immediately after resetting the voltage maximum value stored in step 214. If it is determined in step 216 that the voltage value has dropped by a predetermined value or more with respect to the new maximum voltage value, switching of the power supply is stopped by stopping the SW control IC 23 (step 217). The method for stopping the switching is as described in detail when the SW control IC stop circuit 26 in FIG. 1 is described.

  Thus, after the first voltage drop is detected in step 211, the stored maximum voltage value is reset without stopping the power supply only by detecting the first voltage drop. After that, if switching is stopped only when a second voltage drop is detected, it is detected when the battery pack 2 is once removed from the charging device 100 in the case of poor contact of the terminals as described above. Switching is not stopped only by the voltage drop. This is because even if the battery pack 2 is removed and the voltage drops, the power supply stop process is not unconditionally performed after the first voltage drop is detected. If the second voltage drop is detected, the switching stops. However, if the battery pack 2 is removed, the battery voltage is not detected and no voltage drop is detected, so the switching does not stop.

  On the other hand, if the battery pack 2 is not recognized and the battery pack 2 continues to be supplied with power because of the failure of the power supply circuit 6 or the like, the battery voltage is kept charged and the battery is fully charged. It will descend after passing. In step 211, when the voltage drops more than a predetermined value, the detection of the voltage drop is reset once, but the battery voltage further drops as the battery continues to be charged. Then, when the second voltage drop is detected in step 216, switching is stopped. By performing such control, there is a risk of battery failure such that the battery pack 2 cannot be recognized without stopping switching in the event of a poor terminal contact at the time of battery mounting. Stop switching only in certain cases.

  If it is determined in step 216 that the current voltage has not dropped by a predetermined value or more from the new maximum voltage value immediately after reset, whether or not the current voltage value has increased by a predetermined value or more from the new maximum voltage value immediately after reset Is discriminated (step 218). In step 218, if the current battery voltage rises by a predetermined value or more from the new maximum voltage value immediately after reset, the voltage drop flag is set to zero (step 219). In step 217, if it is not determined that the current battery voltage has increased by a predetermined value or more from the voltage value immediately after reset, the process returns to step 201.

  The steps after step 218 are as follows. When the battery mounting cannot be recognized due to poor contact of the terminals when the battery is mounted as described above, the battery pack 2 is once removed and then the battery pack 2 is mounted again. In the case where the battery mounting is not recognized again due to a contact failure of the terminal or the like again, the processing from step 208 is performed again. When the battery pack 2 is once removed due to poor terminal contact or the like, the state of proceeding to step 216 for detecting the second voltage drop is maintained in the flow. In this state, if the battery pack 2 with poor contact is mounted again and then removed again, a second voltage drop is detected and switching stops. At this time, when the battery pack 2 is mounted, the voltage detected by the battery voltage detection circuit 5 rises to a value corresponding to the battery voltage. When the voltage rises once while detecting the second voltage drop in this way (step 218: YES), step 208 detects the first voltage drop again by setting the voltage drop flag to zero. The switching power supply is prevented from being stopped unnecessarily.

  In the above embodiment, the battery voltage detection circuit 5 corresponds to battery voltage detection means, the battery temperature detection circuit 3 corresponds to battery mounting determination means, the power supply circuit 6 corresponds to power supply means, and the SW control IC The stop circuit 26 corresponds to power supply stop means. The microcomputer 50 corresponds to storage means and control means of the present invention.

  As described in detail above, according to charging apparatus 100 according to the present embodiment, battery pack 2 is not recognized by battery temperature detection circuit 3 that recognizes the mounting of battery pack 2, and is actually mounted. However, a process for avoiding erroneous charging when it is not recognized is performed. In other words, using the property of the secondary battery that the battery voltage drops after full charge, if the battery voltage sampled every predetermined time drops more than a predetermined value than the maximum value, a failure will occur. It is determined whether charging has been performed or whether the user has noticed a failure and has re-mounted the battery pack 2. In other words, if the previous maximum voltage value is reset and the newly detected voltage value becomes the new maximum voltage value, and a voltage drop of a predetermined value or more is detected further than the new maximum voltage value, some sort of failure has occurred. Judge that there is, stop the switching power supply. That is, power supply from the AC power supply 1 to the power supply circuit 6 is stopped. When the second voltage drop is not detected or when a voltage rise of a predetermined value or more is detected, the process returns to the battery mounting determination process without stopping the power supply.

  By performing the processing as described above, erroneous charging is performed when there is a malfunction in the function of recognizing battery mounting or a malfunction in the function of turning on and off the connection of the supply path for supplying power to the battery pack 2. However, it is possible to stop charging safely and reliably. Therefore, it is possible to avoid a decrease in battery life or failure due to overcharging. In this case as well, since power is supplied until the battery voltage starts to drop, the attached battery can be charged to a fully charged state.

  Further, when the user notices a problem and re-installs the battery pack 2 or removes the battery pack 2, the power supply is not unnecessarily stopped. Therefore, charging can be performed efficiently.

  Note that the above processing can be performed without providing a charging current detection circuit for detecting the charging current, and there is an effect of reducing the size of the circuit and reducing the cost.

  The charging device according to the present invention is not limited to the above-described embodiment, and various modifications and improvements can be made within the scope described in the claims. For example, the specific circuit configuration of the charging apparatus 100 is not limited to the above example, and other configurations may be used as long as they perform substantially the same operation.

  In addition, when the voltage value detected when the battery pack 2 is not recognized to be mounted changes due to an increase or decrease of a predetermined value or more, the microcomputer 50 recognizes the mounting of the battery pack 2 due to a contact failure of the terminals. However, it may be determined that the charging current may be supplied to the battery pack 2 by mistake, and the switching power supply may be stopped.

  The charging device of the present invention can be used as a device for charging a secondary battery used in an electric tool.

The circuit diagram which shows the structure of the charging device by this Embodiment. The flowchart which shows operation | movement of the charging device by this Embodiment. The figure which shows the change of the charging voltage of a secondary battery.

Explanation of symbols

  1: AC power supply 2: Battery pack 2b: Thermistor 3: Battery temperature detection circuit 6: Power supply circuit 7: Power supply control circuit 9: SW control IC stop signal transmission circuit 9b: Transmitter 23: SW control IC 25: Constant voltage Circuit 26: SW control IC stop circuit 26b: Receiver 50: Microcomputer 60: Constant current control circuit 70: Constant current setting circuit

Claims (3)

A charging device for charging a battery,
Battery voltage detecting means for detecting the battery voltage;
Storage means for storing a voltage value detected by the battery voltage detection means;
Battery mounting determining means for determining whether or not the battery is mounted on the charging device;
A power supply unit that operates by receiving a power supply from an external power source, and that supplies power to the battery when the battery mounting determination unit determines that the battery is mounted;
Power supply stopping means for stopping power supply from the external power supply to the power supply means;
Control means for controlling the operation of the charging device;
Have
The control means includes
Voltage detection control means for causing the battery voltage detection means to detect a voltage value;
Voltage value storage control means for storing the voltage value detected by the battery voltage detection means;
Voltage change determining means for determining that the voltage value detected by the battery voltage detecting means has changed when it is determined that the battery is not mounted in the battery mounting determining means;
A power stop control means for operating the power stop means when the voltage change determining means detects a change in the voltage value;
A charging device comprising: The voltage storage control means stores the voltage value detected by the battery voltage detection means in the storage means, and stores the highest value among the detected voltage values as a maximum voltage value,
The voltage change determining means determines that the voltage value detected by the battery voltage detecting means has dropped by a predetermined value or more than the maximum voltage value,
The power supply stop control means operates the power supply stop means when the voltage change determination means detects a voltage drop equal to or greater than the predetermined value. The control means includes
Maximum voltage value reset that deletes storage of the maximum voltage value from the storage means when the voltage change determination means determines that the voltage value detected by the battery voltage detection means has fallen a predetermined voltage below the maximum voltage value Means,
Maximum voltage value updating means for storing the voltage value detected by the voltage detection means immediately after the maximum voltage value resetting means deletes the storage of the maximum voltage value in the storage means as a new maximum voltage value;
Further comprising
The power stop control means, when it is determined that the voltage value detected by the voltage detection means after the new maximum voltage value is stored falls below a predetermined value from the new maximum voltage value, the power stop means The charging device according to claim 2, wherein the charging device is operated.

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