JP2011055588A - Charger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charger which can efficiently charge a secondary battery in a simple configuration by using a solar cell as a power source. <P>SOLUTION: In the charger 100, an input voltage feedback circuit 7 changes the set value of the input voltage of a solar cell 1 by a signal from a microcomputer 11. That is, the microcomputer 11 sets different input voltage set values V1-V5 in order in the resistors 7e-7h of the input feedback circuit 7, depending upon whether they output low signals or not. Furthermore, it measures a charge current to each voltage value, and sets the input voltage of a solar cell 1 at charge to an input voltage value, by which the maximum charge current allowable can be obtained, according to the voltage of a battery. It can input the maximum input voltage among the set values into the solar cell 1 by repeating this setting in every set time, thus it is possible to charge the secondary battery efficiently in a simple and low-cost configuration by the resistors 7e-7h. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a charging device for charging a secondary battery such as a lithium ion battery, a nickel hydride battery, or a nickel cadmium battery for an electric tool using a solar battery as a power source.

  Conventionally, a charging device for charging a nickel-cadmium battery or a lithium-ion battery is charged by being supplied from a commercial power source. However, for example, when a cordless electric tool or the like is used in a place where commercial power is not supplied, the user has to prepare a number of spare batteries according to the amount of work. Therefore, there is a demand for a charging device that can be charged from another power source other than the commercial power source. To meet this demand, a plurality of converters are provided as voltage conversion means, and the converter is turned on / off according to the power source as the power source. There has been proposed a charging device that can be driven to charge a battery pack with a power source other than a commercial power source (see, for example, Patent Document 1).

Japanese Patent Laying-Open No. 2005-245145 (page 3-6, FIG. 1)

  Various power sources can be considered as power sources other than commercial power sources. For example, consider a solar cell that is attracting attention because it is environmentally friendly and clean. With solar cells, the amount of power that can be extracted increases if the amount of irradiation is large, and the amount of power that can be extracted decreases if the amount of irradiation is small. Moreover, even if it is the same irradiation amount, generated electric power changes with what voltage value uses a solar cell. In addition, the generated power varies depending on the operating temperature even with the same irradiation amount. In order to take out the maximum electric power strictly from the solar cell under such various conditions, a method by a complicated calculation using a microcomputer or the like can be considered. However, the use of a microcomputer capable of such a complicated calculation has a problem in terms of cost.

  Therefore, the present invention is to provide an inexpensive and simple configuration charging device for efficiently charging a secondary battery using a solar battery as a power source.

  In order to achieve the above object, the invention described in claim 1 is directed to a charging voltage feedback circuit that feeds back a signal for controlling the charging voltage to a predetermined voltage value, and to control the charging current to a predetermined current value. A charging current feedback circuit that feeds back a signal of the above, a switching control means for controlling the output to a predetermined voltage value and a predetermined current value by a feedback signal from the charging voltage feedback circuit and the charging current feedback circuit, and an input voltage from the solar cell An input voltage feedback circuit that feeds back a signal for controlling the input voltage to a predetermined input voltage value, an input voltage detection means for detecting an input voltage from the solar cell, a charging current detection means for detecting a charging current, A charging device for charging a secondary battery using a solar cell having an input as a power source Thus, the input voltage setting means for setting one of a plurality of setting values as the predetermined input voltage value, and all the input voltage values that can be selected by the input voltage setting means at every predetermined time are sequentially selected and selectable. Charging current storage means for storing the charging current for each input voltage value, battery voltage detection means for detecting the battery voltage of the secondary battery, and a maximum for obtaining a maximum allowable current value corresponding to the battery voltage detected by the battery voltage detection means An allowable current calculating means; and an input voltage selecting means for selecting, from the selectable input voltage values, an input voltage value that maximizes the charging current stored in the charging current storage means within a range not exceeding the maximum allowable current. The input voltage setting means updates the setting of the input voltage to the input voltage selected by the input voltage selection means every predetermined time, and performs charging with the updated input voltage.

  According to such a configuration, the solar cell is always set to output the maximum power within the set value within the allowable range corresponding to the battery voltage, regardless of the state of light irradiation or the like.

  The invention described in claim 2 is characterized in that, in the invention described in claim 1, the input voltage setting means comprises a plurality of resistors having different resistance values.

  According to such a configuration, the input voltage from the solar cell to the charging device varies depending on which of the plurality of resistors of the input voltage setting unit is selected.

  The invention according to claim 3 further includes battery state detecting means for detecting the state of the secondary battery, and charging current limiting means for determining a maximum charging current according to the state detected by the battery state detecting means, The input voltage selection means sets the input voltage value so as not to exceed the maximum charging current.

  According to such a configuration, the maximum output power is obtained from the solar cell in the set value within a range not exceeding the maximum charging current according to the type and connection state of the secondary battery and the temperature of the secondary battery. Is set.

  The invention according to claim 4 is a switching control means for converting the power of the solar cell to provide a charging current to the secondary battery, an input voltage detecting device for detecting input power from the solar cell, and a charging current. A charge current detecting means for detecting the input voltage, and an input control means for changing the input voltage so that the charging current becomes a current corresponding to the secondary battery by operating the switching control means. Yes.

  According to such a configuration, the solar cell is always set to output the maximum power within the set value within the allowable range corresponding to the battery voltage, regardless of the state of light irradiation or the like.

  According to the charging device of claims 1 and 4 of the present invention, the charging current to the secondary battery is maximized within an allowable range according to the battery voltage without detecting the state of the irradiation amount of the solar battery. By setting the input voltage from the solar battery to the charging device as described above, it is possible to always output the maximum power among the set values within the allowable range according to the battery voltage, and it is possible to obtain an efficient charging device. .

  According to the charging device according to claim 2, in addition to the effect of the charging device according to claim 1, with the simple configuration of selecting one from a plurality of resistors, the maximum value from the solar cell among the set values Electric power can be obtained.

  According to the charging device of the third aspect, in addition to the effect of the charging device of the first or second aspect, since the setting does not exceed the maximum charging current according to the state of the secondary battery, It is possible to charge safely without considering the state of the battery.

  Thus, according to the charging device of the present invention, it is possible to provide an excellent effect that it is possible to provide a charging device that can be efficiently charged with an inexpensive and simple configuration using a solar cell as a power source.

The figure which shows the change by the irradiation amount in the relationship between the output current with respect to the output voltage of the solar cell by one embodiment of this invention, and output power. The figure which shows the change by the temperature in the relationship of the output current with respect to the output voltage of the solar cell by one embodiment of this invention. The figure which shows the case where the irradiation amount in the relationship of the output current with respect to the output voltage of the solar cell by one embodiment of this invention is significantly small. The circuit diagram which shows the charging device and secondary battery by one embodiment of this invention. The flowchart which shows the charging method by one embodiment of this invention. The flowchart which shows the charge method by the modification of this invention. The table | surface which shows the relationship between the battery temperature and the limit current in the charging method by the modification of this invention.

  A charging apparatus according to an embodiment of the present invention will be described with reference to FIGS.

  First, output characteristics of solar cell 1 serving as a power source of charging apparatus 100 according to the present embodiment will be described. The solar cell 1 is a power generation device that generates power using the photoelectric effect of a semiconductor such as silicon (SI).

  In FIG. 1, an example of the dose dependency in the output characteristic of the solar cell 1 is shown. In FIG. 1, the horizontal axis represents the output voltage of the solar cell, and the vertical axis represents the output current and output power. Further, the irradiation amount P1> the irradiation amount P2, and the irradiation amount P1 is larger, indicating that the sunlight is irradiated. As shown in FIG. 1, the output characteristics of the solar cell 1 change depending on the irradiation amount. That is, if the irradiation amount is large, the electric power that can be taken out increases like the irradiation amount P1, and if it is small, the electric power that can be taken out like the irradiation amount P2 decreases. The broken line in FIG. 1 shows the change in output power with respect to the output voltage in the case of the dose P1, for example. Thus, even if the irradiation amount is the same, the generated power differs depending on the voltage value at which the solar cell is used. This will be described with reference to FIG.

  When a solar cell is used at point A in the dose P1 in the figure, the power is voltage x current. For example, if the voltage value at this point is Va and the current value is Ia, the power that can be extracted is VaxIa. Become. On the other hand, consider the case where a solar cell is used at the point A '. For example, if A ′ is a point having a value half the voltage at point A, the voltage value is ½ Va. Further, as can be seen from the figure, the current hardly changes at the points A and A '. Therefore, the current Ia ′ at the point A ′ is substantially Ia as with the point A. Therefore, the electric power that can be taken out at the point A 'is 1/2 VaxIa. That is, the electric power that can be taken out at the point A ′ is ½ of the electric power that can be taken out at the point A.

  The same can be said for the case where there is an irradiation amount of a certain amount or more and the irradiation amount P2 (irradiation amount P1> irradiation amount P2) at the same temperature. The point at which the power that can be extracted at a certain dose is maximized is that the vertical line is drawn from the voltage line on the horizontal axis in the figure and the output characteristic is hit, and the horizontal line is drawn from that point to the current line on the vertical axis. This is a place where the area of the rectangle formed by being surrounded by the horizontal axis, the vertical axis, the horizontal line, and the vertical line when it is drawn becomes maximum (for example, Wmax in FIG. 1). The area of this rectangle is horizontal axis (voltage) x vertical axis (current) = power. Hereinafter, this point is referred to as a maximum operating point.

  Here, a case where the secondary battery is directly connected to the solar battery and charged is considered. In this case, the voltage of the solar battery is reduced to the voltage of the secondary battery. For example, when a solar cell having the characteristics shown in FIG. 1 is directly connected to a secondary battery having a voltage of 1/2 Va, the voltage of the solar cell is also reduced to 1/2 Va. If the dose is P1, the charging current that flows is Ia. Therefore, although the maximum value of the power that can be extracted is VaxIa as described above, only ½ VaxIa of power can be extracted when directly connected.

  On the other hand, consider a case where a switching circuit is provided between the solar battery and the secondary battery so as to control the voltage of the solar battery so as to become a predetermined value. If control is performed to keep the voltage of the solar cell at Va, the power of VaxIa can be taken out in the case of the irradiation amount P1 as described above. Therefore, for example, when charging a secondary battery having a voltage of 1 / 2Va, the charging current is as follows. That is, since output power = efficiency × input power, it can be expressed as output voltage × output current = efficiency × input voltage × input current. Here, the output voltage is 1 / 2Va, the input voltage is Va, and the input current is Ia. When the efficiency is 85%, for example, from 1 / 2Vax output current = 0.85xVaxIa, output current = 2x0.85Ia = 1. 7Ia, and charging can be performed with a charging current approximately 1.7 times that of the direct connection.

  As described above, the voltage value at the maximum operating point of the solar cell is approximately equal to the same voltage value as in the dose P1 and dose P2 in FIG. It becomes. However, depending on the conditions in which the solar cell is placed, for example, as shown in FIG. 2, when the temperature is high, this voltage value decreases and the maximum operating point deviates considerably. That is, when the temperature is T1, the output characteristic is as shown by a solid line, and the maximum operating point is the point B of the output voltage Vb and the output current Ib. When the temperature T2 is lower than the temperature T1, the output characteristic is as shown by a broken line, and the maximum operating point is the point C of the output voltage Vc and the output current Ic.

  As shown in FIG. 3, even when the irradiation amount to the solar cell is reduced, there is a considerable deviation. In other words, when the dose is P3, the output characteristic is as shown by a solid line, and the maximum operating point is the point D of the output voltage Vd and the output current Id. When the dose P4 is lower than the dose P3, the output characteristics are as shown by the broken line, and the maximum operating point is the point E of the output voltage Ve and the output current Ie.

  In order to take out strictly the maximum electric power from the solar cell under various conditions as described above, complicated calculation using, for example, a microcomputer or the like is required. However, a high-performance microcomputer capable of executing such complicated operations has a problem of high cost. The charging device according to the present embodiment has a configuration that does not require a high-performance microcomputer.

  FIG. 4 is a circuit block diagram showing a charging apparatus according to an embodiment of the present invention. As shown in FIG. 4, the charging device 100 is a charging device that charges the battery pack 3 using a solar cell 1 connected to the outside as a power source.

  The battery pack 3 is a battery pack to be charged, and includes a battery set 3a to which one or more cells are connected, and a battery type discriminating resistor comprising a discrimination resistor for discriminating the type or number of cells of the battery set 3a. 3b and a temperature sensitive resistor 3c such as a thermistor for monitoring the battery temperature set in the vicinity of the battery set 3a.

  The solar cell 1 is a power source that generates power when light enters. The solar cell 1 may be configured to be removable from the charging device 100. The charging device 100 includes a smoothing capacitor 6 and a switching power supply circuit 8 and outputs charging power for charging the battery pack 3 having a secondary battery. The charging device 100 includes an input voltage detection circuit 15, an input voltage feedback circuit 7, a charging voltage feedback circuit 9, a charging current feedback circuit 10, a microcomputer 11, an auxiliary power supply 2, a battery type determination circuit 4, a battery temperature detection circuit 5, A battery voltage detection circuit 12 and a charge on / off circuit 13 are provided to control charging power.

  The smoothing capacitor 6 smoothes the output of the solar cell 1. The switching power supply circuit 8 is a circuit for controlling a charging voltage and a charging current, and includes a DC / DC converter 8a, a P-channel FET 8b, a rectifier diode 8c, a coil 8d, and a smoothing capacitor 8e. In this embodiment, the voltage of the solar cell is stepped down to generate a charging voltage. The DC / DC converter 8a is a step-down circuit connected to the positive and negative outputs of the smoothing capacitor 6 and the gate of the FET 8b. The DC / DC converter 8a receives a feedback signal output from a charging voltage feedback circuit 9 and a charging current feedback circuit 10 to be described later, and controls the switching timing of the FET 8b in accordance with the signal to charge the DC / DC converter 8a. Control current and charge voltage. Note that the source of the FET 8 b is connected to the positive side of the solar cell 1. The rectifier diode 8 c is connected between the drain of the FET 8 a and the negative side of the solar cell 1. The input side of the coil 8d is connected to the drain of the FET 8b, and the smoothing capacitor 8e is connected between the output side of the coil 8d and the negative side of the solar cell 1, and smoothes the output of the DC / DC converter 8a.

  The input voltage detection circuit 15 is an input voltage detection circuit for detecting an input voltage, and includes a resistor 15 a and a resistor 15 b connected to the positive side of the solar cell 1. The input voltage is divided by the resistor 15a and the resistor 15b, and the divided value is input to an A / D port 11f of the microcomputer 11 described later, whereby the microcomputer 11 reads the input voltage.

  The input voltage feedback circuit 7 includes resistors 7a, 7b, 7c, 7d, 7e, 7f, 7g, 7h and an operational amplifier 7i. The resistors 7a and 7b are connected in series to each other and divide the output voltage of the solar cell 1 as an input, and the divided value is input to the non-inverting input terminal of the operational amplifier 7i. The resistors 7c and 7d are connected in series to each other, divide the value of the voltage Vcc, and input the input voltage to the inverting input section of the operational amplifier 7i as an input voltage setting value for keeping the input voltage at a certain predetermined value. This voltage value is referred to as a first input voltage setting value V1.

  One end of each of the resistors 7e, 7f, 7g, and 7h is connected to the connection point between the resistors 7c and 7d, and the other end is connected to the output port 11d of the microcomputer 11. For example, by outputting a low signal from a port connected to the resistor 7e of the microcomputer 11 to be described later, the set value of the input voltage input to the inverting input unit of the operational amplifier 7i is changed in parallel with the resistor 7c of the voltage Vcc and the resistors 7d and 7e. It can be set to a partial pressure value with the resistor. This value is a second input voltage setting value V2 different from the first input voltage setting value V1 obtained by dividing the voltage Vcc by the resistors 7c and 7d.

  Similarly, by outputting a low signal from a port connected to the resistor 7f of the microcomputer 11, the set value of the input voltage input to the inverting input portion of the operational amplifier 7i is changed to the parallel resistance of the resistor 7c of the voltage Vcc and the resistors 7d and 7f. Can be set to a third input voltage setting value V3. Similarly, by outputting a low signal from a port connected to the resistor 7g of the microcomputer 11, the set value of the input voltage inputted to the inverting input portion of the operational amplifier 7i is changed to the parallel resistance of the resistor 7c of the voltage Vcc and the resistors 7d and 7g. And this value becomes the fourth input voltage setting value V4. Similarly, by outputting a low signal from a port connected to the resistor 7h of the microcomputer 11, the set value of the input voltage input to the inverting input portion of the operational amplifier 7i is changed to the parallel resistance of the resistor 7c of the voltage Vcc and the resistors 7d and 7h. And this value becomes the fifth input voltage setting value V5.

  The output voltage value of the solar cell 1 is controlled based on the output signal of the operational amplifier 7i so as to be the input voltage set value set according to the output signal of the microcomputer 11. The value set as the input voltage setting value is set to a value that can take out electric power that is substantially close to the maximum electric power from the solar cell 1.

  The charging voltage feedback circuit 9 includes resistors 9a, 9b, 9c and 9d, an operational amplifier 9e, and a diode 9f. The resistors 9a and 9b divide the output voltage of the switching power supply circuit 8, that is, the charging voltage, and the divided value is input to the non-inverting input terminal of the operational amplifier 9e. The resistors 9c and 9d divide the value of the voltage Vcc, and the divided voltage is input to the inverting input terminal of the operational amplifier 9e as a charging voltage setting value for keeping the charging voltage at a certain predetermined value. A signal corresponding to the difference between the charging voltage divided by the resistors 9a and 9b and the charging voltage set value obtained by dividing the voltage Vcc by the resistors 9c and 9d is output from the operational amplifier 9e, and the DC / DC converter is based on the signal. The charging voltage is controlled by 8a switching the switching FET 8b. Here, since the diode 9f is connected in series to the output side of the operational amplifier 9e, the charging voltage set value is actually a limit voltage value for preventing the battery voltage from rising above this set value. Thus, the DC / DC converter 8a performs switching of the FET 8b so as to increase the voltage when the voltage falls below the charging voltage set value, and conversely, the FET 8b reduces the voltage when the voltage rises above the set value. A predetermined voltage is maintained by switching.

  The charging current feedback circuit 10 includes a shunt resistor 10a, resistors 10b, 10c, 10d, 10e, and 10f, operational amplifiers 10g and 10h, and a diode 10i. When a current flows through the shunt resistor 10a, a negative potential of current x shunt resistor x (-1) is input to the non-inverting input terminal of the operational amplifier 10g. The operational amplifier 10g and the resistors 10b, 10c, and 10d constitute an inverting amplifier circuit, and a value that is 10d / 10c times the negative potential proportional to the charging current input to the non-inverting input terminal of the operational amplifier 10g is obtained from the output. Is output. The output value is input to the non-inverting input terminal of the operational amplifier 10h. On the other hand, the output of the operational amplifier 7i, which is a feedback signal from the input voltage feedback circuit 7, is input to the inverting input terminal of the operational amplifier 10h. The operational amplifier 10h outputs a current control signal corresponding to the charging current flowing through the shunt resistor 10a and the output of the input voltage feedback circuit 7, and controls the switching of the FET 8b by the DC / DC converter 8a to control the charging current. At this time, since the diode 10i is connected in series to the output side of the operational amplifier 10h, the current control signal is a signal for actually preventing the charging current from rising above a predetermined value.

  Here, consider a case where the input voltage (voltage of the solar cell 1) is higher than the input voltage setting set in the input voltage feedback circuit 7. In the present embodiment, the charging voltage and the charging current are controlled in the switching power supply circuit 8 based on the feedback output from the operational amplifiers 9e and 10h. That is, switching control is performed in the switching power supply circuit 8 so that the potentials of the non-inverting input portion and the inverting input portion of the operational amplifiers 9e and 10h become the same potential (imaginary short). As the input voltage rises, the input voltage feedback circuit 7 cannot balance the input section of the operational amplifier 7i. Further, since the output of the operational amplifier 7i is input to the input portion of the operational amplifier 10h of the charging current feedback circuit 10, the input portion of the operational amplifier 10h cannot be balanced. Then, the switching power supply circuit 8 performs switching so that the input parts of the operational amplifiers 7i and 10h are balanced based on the feedback signal from the operational amplifier 10h. By performing this switching, the charging current is increased to such a value that the input voltage decreases to the input voltage setting. Conversely, when the input voltage (solar cell voltage) is lower than the input voltage setting set in the input voltage feedback circuit 7, the switching power supply circuit 8 increases the charging current to the input voltage setting. Reduce to value. That is, when the irradiation amount increases and the solar cell voltage increases, the charging current is increased. Conversely, when the irradiation amount decreases and the solar cell voltage decreases, switching is performed to decrease the charging current. The power supply circuit 8 controls the battery voltage of the solar cell to a predetermined value.

  The microcomputer 11 includes a CPU 11a, output ports 11b, 11c, 11e, 11d, and A / D ports 11e, 11f, and controls the operation of the charging device 100.

  The battery voltage detection circuit 12 includes resistors 12a and 12b. The battery voltage is divided by the resistors 12a and 12b and input to the A / D port 11f of the microcomputer 11.

  The charge on / off circuit 13 is controlled by a signal from an output port 11b connected to the resistor 13A of the microcomputer 11. When charging is performed, for example, a high signal is output from the output port 11b connected to the charging on / off circuit 13 of the microcomputer 11, whereby the charging device 100 and the battery set 3a are connected to perform charging. Conversely, when charging is terminated, for example, a low signal is output from the output port 11b of the microcomputer 11 so that the charging device 100 is disconnected from the battery set 3a, whereby the charging is terminated.

  The battery type discriminating circuit 4 is a battery type discriminating means for discriminating the type of the battery pack 4a, and includes a resistor 4a. The battery type is determined by inputting a value obtained by dividing the voltage Vcc by the resistor 4a and the battery type determining resistor 3b set in the battery pack 3 to an A / D port 11e of the microcomputer 11 described later. The battery type here refers to, for example, a difference in the type of the battery itself such as a lithium ion battery, a nickel hydride battery, or a nickel cadmium battery, or a difference in the number of cells in the lithium ion battery (for example, a difference such as 4 cells or 5 cells) or connection. It is the difference between the states (series and parallel). The reason for determining the battery type is that the charge control method differs depending on the battery type, and accordingly, it is necessary to perform appropriate charging for each battery type.

  The battery temperature detection circuit 5 is a battery temperature detection means composed of resistors 5a and 5b. The battery temperature is a value obtained by dividing the voltage Vcc by the resistor 5a, the resistor 5b, and the parallel resistance of the temperature-sensitive resistor 3c, which is a temperature-sensitive element whose resistance value varies depending on the battery temperature in the battery pack 3. 11 is read by inputting to the A / D port 11e.

  The charging state display circuit 14 is a display circuit for informing the user of the presence or absence of charging, and includes resistors 14a, 14b, 14c, an LED 14d, and an FET 14e. During charging, by outputting a high signal from the output port 11c connected to the resistor 14b of the microcomputer 11, the FET 14e is turned on and the LED 14d is turned on. Conversely, when the battery is not charged, the FET 14e is turned off and the LED 14d is turned off by outputting a low signal from the output port 11c.

  The auxiliary power source 2 is a power source for the microcomputer 11 and operational amplifiers, and includes a DC / DC converter 2a, a Pch FET 2b, a rectifier diode 2c, a coil 2d, a smoothing capacitor 2e, and resistors 2f and 2g. The In this embodiment, the voltage of the solar cell is stepped down to generate a voltage Vcc that serves as a power source for the microcomputer 11 and the like. The DC / DC converter 2a steps down the output of the smoothing capacitor 6. The DC / DC converter 2a switches the FET 2b, which is a switching element, so that a value obtained by dividing the output voltage by the resistors 2f and 2g becomes a predetermined value set in the DC / DC converter 2a. The values of the resistors 2f and 2g may be set so that a value obtained when the desired voltage Vcc is divided by the resistors 2f and 2g becomes a predetermined voltage set in the DC / DC converter 2a.

  Next, the operation of the charging apparatus according to the present embodiment will be described with reference to the circuit block diagram of FIG. 4 and the flowchart of FIG.

  First, when the solar battery 1 that is an input power supply is connected to the charging device, power is supplied to the auxiliary power supply 2 by the solar battery, whereby electric power is supplied to the microcomputer 11 and the microcomputer 11 enters an operating state. Before the battery is mounted, the LED 14d is turned off in order to notify the user that the battery is not charged (step 501). In order to turn off the LED 14d, the FET 14e is turned off by outputting a low signal from the output port 11c connected to the resistor 14b of the microcomputer 11.

  Next, it is determined whether or not the battery pack 3 is mounted on the charging device 100. The connection of the battery pack 3 may be determined by, for example, a change in the detection signal of the battery temperature detection circuit 5 input to the A / D port 11e of the microcomputer 11 (step 502). Subsequently, the battery type is determined based on the detection signal from the battery type detection circuit 4 (step 503). The battery type is set in accordance with the resistance value of the battery type discriminating resistor 3b in the battery pack 3. For example, the battery type differs depending on the type such as a lithium ion battery, a nickel hydride battery, a nickel cadmium battery, an output voltage of 14.4V, It is set based on a voltage band such as an 18V battery or the number of battery cells in the battery pack 3.

  Here, before the start of charging, the input voltage is set to be the first input voltage setting value V1. As described above, the first input voltage setting value V1 is defined as a value set by the resistors 7c and 7d by not outputting a signal from the output port 11d of the microcomputer 11 connected to the resistors 7e to 7h. (Step 504).

  Next, charging is started (step 505). The start of charging is controlled by outputting a signal from the output port 11b connected to the charging on / off control circuit 13a of the microcomputer 11. When charging is started, the LED 14d in the charging state display circuit 14 is turned on in order to notify the user of the start of charging (step 506). To turn on the LED 14d, a high signal is output from the output port 11c connected to the resistor 14b of the microcomputer 11, and the FET 14e is turned on.

  The charging apparatus 100 according to the present embodiment has a circuit capable of setting a plurality of input voltages, changes the input voltage every predetermined time, and the charging current at that time becomes a charging current that can be allowed by the battery pack 3. It is configured to set the corresponding input voltage. The method will be described below.

  When charging is started in step 505, the charging current is detected by detecting the value output from the output section of the operational amplifier 10g at that time in the A / D port 11f of the microcomputer 11, and the value is stored (step 507). Next, the input voltage is set to the second input voltage setting value V2. The second input voltage setting value V2 is set by a resistor 7c and a parallel resistor of the resistors 7d and 7e, and is set by outputting a low signal from the output port 11d of the microcomputer 11 connected to the resistor 7e ( Step 508). The value output from the output terminal of the operational amplifier 10g at that time is detected at the A / D port 11f of the microcomputer 11 to detect the charging current, and the value is stored (step 509).

  Next, the input voltage is set to the third input voltage set value V3. The third input voltage set value V is set by a resistor 7c and a parallel resistor of the resistors 7d and 7f, and is set by outputting a low signal from the output port 11d of the microcomputer 11 connected to the resistor 7f ( Step 510). The value output from the output terminal of the operational amplifier 10g at that time is detected at the A / D port 11f of the microcomputer 11 to detect the charging current, and the value is stored (step 511).

  Next, the input voltage is set to a fourth input voltage set value V4. The fourth input voltage setting value V4 is set by a resistor 7c and a parallel resistor of resistors 7d and 7g, and is set by outputting a low signal from the output port 11d of the microcomputer 11 connected to the resistor 7g ( Step 512). The charging current is detected by detecting the value output from the output section of the operational amplifier 10g at that time in the A / D port 11f of the microcomputer 11, and the value is stored (step 513).

  Next, the input voltage is set to a fifth input voltage set value V5. The fifth input voltage setting value V5 is set by a resistor 7c and a parallel resistor of resistors 7d and 7h, and is a value set by outputting a low signal from the output port 11d of the microcomputer 11 connected to the resistor 7h ( Step 514). The charging current is detected by detecting the value output from the output section of the operational amplifier 10g at that time in the A / D port 11f of the microcomputer 11, and the value is stored (step 515).

  Next, the maximum allowable current that can be supplied based on the battery voltage of the battery pack 3 is obtained, and the maximum allowable current is determined from the charging current values detected and stored in steps 507, 509, 511, 513, and 515. Set the voltage value to the input voltage at the maximum charging current within the range. That is, a corresponding low signal is output from the output port 11d of the microcomputer 11 so that the input voltage setting value to be set is obtained. As described above, by performing the processes in steps 507 to 516, it is possible to easily detect the operating voltage of the solar battery having the largest charging current according to the battery voltage.

  Next, it is determined whether or not a predetermined time has elapsed since the start of charging (step 517). If it is determined in step 517 that the predetermined time has elapsed, the input voltage is changed from V1 to V5 as previously performed in steps 507 to 516, and the respective charging currents at that time are detected and stored. In addition, the maximum allowable current that can be supplied based on the battery voltage of the battery pack 3 is obtained, and the input voltage at the maximum charging current within the range not exceeding the maximum allowable current from the stored charging current values. A voltage value is set (steps 518 to 528). By repeating this process at regular intervals, it is possible to efficiently perform charging with the optimum operating voltage at all times.

  Next, it is determined whether or not the battery is fully charged (step 529). There are various methods for determining the full charge. For example, when charging a lithium ion battery, a method for determining full charge when the battery voltage detected by the battery voltage detection circuit 12 reaches a predetermined value. Etc. The predetermined value of the battery voltage to be determined as full charge at this time is based on the battery type detected in step 503, for example, 4 cells × 4.2V = 16.8V, 5 cells in the case of a 4-cell series-connected lithium ion battery. In the case of a series-connected lithium ion battery, the voltage may be set to 4.2 V per cell, such as 5 cells × 4.2 V = 21 V. Note that the value of the predetermined value to be set is not limited to this.

  In the case of a nickel cadmium battery, for example, there is a method of determining that the battery is fully charged when the battery temperature detected by the battery temperature detection circuit 5 reaches a predetermined temperature or higher during charging. In addition, these full charge detection methods are examples, and are not limited thereto, and need to be appropriately determined.

  If it is determined in step 529 that the battery is fully charged, charging is terminated (step 530). If it is determined in step 529 that the battery is not fully charged, the process returns to step 517 again. The end of charging is controlled by outputting a signal from the output port 11b connected to the charging on / off control circuit 13a of the microcomputer 11. When the charging is terminated in step 530, the LED 14b of the charging state display circuit 14 is turned off to notify the user that the charging is terminated (step 531). To turn off the LED 14b, a low signal is output from the output port connected to the resistor 14b of the microcomputer 11, and the FET 14e is turned off.

  Next, it is determined whether or not the battery pack 3 has been removed from the charging apparatus 100 (step 532). If it has been removed, the process returns to step 501. In this way, the input voltage is changed every predetermined time, the charging current is detected and stored at that time, and the input voltage is set to a value in which the charging current is maximized. The operating voltage of the battery can be easily detected, and efficient charging becomes possible.

  As described above, in the charging device 100 according to the embodiment of the present invention, the microcomputer 11 has different input voltage setting values depending on whether or not to output a low signal to the resistors 7e to 7h of the input voltage feedback circuit 7. V1 to V5 are sequentially set. Furthermore, the charging current for each voltage value is measured and stored, and the input voltage setting value for obtaining the maximum charging current within the range not exceeding the maximum allowable current according to the battery voltage of the battery pack 3 The input voltage of the battery 1 is set. By repeating this setting every predetermined time, the maximum input power according to the battery voltage can be always input to the solar cell 1. Moreover, since the setting of the input voltage of the solar cell 1 is made by selecting any one of the resistors 7e to 7h, it can be efficiently charged with a simple and low-cost configuration.

  Next, a modification of the operation of the charging apparatus according to the present embodiment will be described with reference to the circuit block diagram of FIG. 4, the flowchart of FIG. 6, and the table of FIG. In the flowchart of FIG. 6, Step 601 to Step 615, Step 618 to Step 628, and Step 631 to Step 634 are the same as Step 501 to Step 515, Step 517 to Step 527, and Step 529 to Step 532 of FIG. Therefore, detailed description is omitted.

  First, when the solar battery 1 that is an input power supply is connected to the charging device, power is supplied to the auxiliary power supply 2 by the solar battery, whereby electric power is supplied to the microcomputer 11 and the microcomputer 11 enters an operating state. Before the battery is mounted, the LED 14d is turned off in order to notify the user that the battery is not charged (step 601). Next, it is determined whether or not the battery pack 3 is mounted on the charging device 100. (Step 602). Subsequently, the battery type is determined based on the detection signal from the battery type detection circuit 4 (step 603).

  Before the start of charging, the input voltage is set to be the first input voltage set value V1 (step 604). Next, charging is started (step 605). When charging is started, the LED 14d in the charging state display circuit 14 is turned on in order to notify the user of the start of charging (step 606).

  When charging is started in step 605, the charging current at that time is detected and the value is stored (step 607). Next, the setting of the input voltage is set to the second input voltage setting value V2 (step 608), the charging current at that time is detected, and the value is stored (step 609). The input voltage is set to the third input voltage set value V3 (step 610), the charging current at that time is detected, and the value is stored (step 611). Similarly, the input voltage is set to the fourth input voltage setting value V4 (step 612), the charging current at that time is detected, and the value is stored (step 613). Further, the input voltage is set to the fifth input voltage setting value V5 (step 614), the charging current at that time is detected, and the value is stored (step 615).

  Next, the maximum permissible current that can be supplied based on the battery voltage of the battery pack 3 is obtained, and the maximum permissible current is determined from the charging current values detected and stored in steps 607, 609, 611, 613, and 615. Set the voltage value to the input voltage at the maximum charging current within the range. At this time, the state of the battery is detected (step 616). Here, the state of the battery includes the type of battery, the temperature of the battery, and the like. If too much current is passed when the battery temperature is low, it is not preferable in terms of battery properties. Therefore, as shown in FIG. 7, for example, when the battery temperature is higher than the temperature T3 (for example, 0 ° C.) and lower than the temperature T4 (for example, 40 ° C.), the maximum current that can be supplied is, for example, the current I7 and the temperature is lower than T3 The limit current is defined as a current I8. That is, if the charging current detected at steps 607, 609, 611, 613, 615 and the voltage value set as the input voltage value exceeds the limit current set according to the temperature, Next, the input voltage setting value when the next largest charging current is obtained is set (step 617). Thus, by providing the limit current according to the temperature, it is possible to easily detect the operating voltage of the solar battery with the largest charging current within a range where the battery performance is not deteriorated or dangerous.

  Next, it is determined whether or not a predetermined time has elapsed since the start of charging (step 618). If it is determined in step 618 that a predetermined time has elapsed, the input voltage is changed from V1 to V5 as previously performed in steps 607 to 616, and the respective charging currents at that time are detected and stored. The input voltage is set to the maximum charging current that can be taken according to the battery state such as temperature (steps 619 to 630). By repeating this process at regular intervals, it is possible to efficiently perform charging with the optimum operating voltage at all times.

  Next, it is determined whether or not the battery is fully charged (step 631). If it is determined in step 631 that the battery is fully charged, charging is terminated (step 632). If it is determined in step 631 that the battery is not fully charged, the process returns to step 618 again. When the charging is terminated in step 632, the LED 14b of the charging state display circuit 14 is turned off to notify the user that the charging is terminated (step 633). Next, it is determined whether or not the battery pack 3 has been removed from the charging device 100 (step 634). If the battery pack 3 has been removed, the process returns to step 601.

  In this way, the input voltage is changed every predetermined time, the charging current is detected and stored at that time, and the input voltage is set to a value that maximizes the charging current according to the state of the battery. It is possible to easily detect the operating voltage of the solar cell, which is the maximum charging current possible, and it is possible to charge efficiently and safely.

  Furthermore, it can be set so as not to exceed the maximum allowable value of the charging current according to the battery state, and charging can be performed more safely.

  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 circuit configuration of the charging device 100 is not limited to the above, and any other configuration may be used as long as the same operation and operation are performed.

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

DESCRIPTION OF SYMBOLS 1: Solar cell 3: Battery pack 3a: Battery set 3b: Battery type discrimination resistance 3c: Temperature sensitive resistance 7: Input voltage feedback circuit 8: Switching power supply circuit 9: Charging voltage feedback circuit 10: Charging current feedback circuit 11: Microcomputer 13 : Charging on / off circuit 15: Input voltage detection circuit

Claims (4)

A charging voltage feedback circuit for feeding back a signal for controlling the charging voltage to a predetermined voltage value; a charging current feedback circuit for feeding back a signal for controlling the charging current to a predetermined current value; and the charging voltage feedback circuit; Switching control means for controlling the output to the predetermined voltage value and the predetermined current value by a feedback signal from the charging current feedback circuit, and a signal for controlling the input voltage from the solar cell to the predetermined input voltage value are fed back. An input voltage feedback circuit, an input voltage detection means for detecting an input voltage from the solar battery, and a charging current detection means for detecting a charging current. A charging device for charging,
Input voltage setting means for setting any one of a plurality of set values as the predetermined input voltage value;
Charging current storage means for sequentially selecting all input voltage values selectable in the input voltage setting means every predetermined time, and storing charging current for each selectable input voltage value;
Battery voltage detection means for detecting the battery voltage of the secondary battery;
Maximum allowable current calculating means for obtaining a maximum allowable current value according to the battery voltage detected by the battery voltage detecting means;
Input voltage selecting means for selecting an input voltage value that maximizes the charging current stored in the charging current storage means within a range not exceeding the maximum allowable current from the selectable input voltage values;
The input voltage setting means updates the setting of the input voltage to the input voltage selected by the input voltage selection means at every predetermined time, and performs charging with the updated input voltage. Charging device.   The charging device according to claim 1, wherein the input voltage setting unit includes a plurality of resistors having different resistance values. Battery state detection means for detecting the state of the secondary battery;
Charging current limiting means for determining a maximum charging current according to the state detected by the battery state detecting means;
Further comprising
The charging device according to claim 1, wherein the input voltage selection unit sets an input voltage value so as not to exceed the maximum charging current. A charging device for charging a secondary battery with electric power of a solar battery,
Switching control means for converting the power of the solar cell to provide a charging current to the secondary battery;
An input voltage detection device for detecting input power from the solar cell;
Charging current detection means for detecting the charging current;
Input control means for changing the input voltage so that the charging current becomes a current corresponding to the secondary battery by operating the switching control means;
A charging device comprising:

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