JP2010206912A - Charger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charger having a simple configuration and which is available for charging a secondary battery, to which a plurality of solar cells having different output characteristics can be connected as an input power supply. <P>SOLUTION: The charger 40 allows a plurality of solar cells A, B, C having different output characteristic to be connected as an input power supply; the charger includes a switching power supply circuit 8, an input voltage feedback circuit 7, a charging voltage feedback circuit 9 and a charging current feedback circuit 10; the switching power supply circuit 8 is controlled, based on a composite signal of error-detecting signals of the three feedback circuits 7, 9, 10, to thereby charge the secondary battery 3a with a charging voltage Vc and a charging current Ic, which corresponds to the optimal output operating point of the output characteristics of the connected solar cells 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  In a cordless type electric tool such as a driver drill, a battery pack composed of a secondary battery such as a nickel cadmium battery (NiCad battery) or a lithium ion battery is generally used as a driving power source of the electric tool.

  Conventionally, a charging device for charging a secondary battery such as a nickel-cadmium battery or a lithium ion battery uses a commercial power source as an input power source. However, when the cordless power tool is used in a place where there is no commercial power supply equipment, it is necessary to prepare a large number of spare secondary batteries when the work volume is large. It may be difficult to carry the secondary battery to the site.

  Therefore, a charging device that can be charged from another power source other than a commercial power source has been proposed as an input power source of a charging device that charges a secondary battery. For example, Patent Document 1 below proposes a charging device that uses another power source other than a commercial power source.

JP 2005-245145 A

Various power sources other than the commercial power source are conceivable as the input power source of the charging device, but the inventors of the present application do not need an existing power supply facility such as a commercial power source at the work site, and the environment in the process of power generation We focused on a charger that uses a solar cell that can prevent contamination as an input power source.
In the voltage-current characteristic (output characteristic) of the solar cell, as shown in FIG. 4, at the time of light irradiation, the output voltage Voc when the output terminal is opened and the open current Isc when short-circuited, It has a maximum output operating point Amax that gives the maximum output power Pmax. In order to efficiently obtain power from the solar cell, it is necessary to operate the solar cell near the maximum output operating point Amax (hereinafter, the operating point Amax or an operating point in the vicinity thereof may be referred to as an “optimum output operating point”). is there. For this reason, when a load is connected to the solar cell, it is required to always maintain the load viewed from the solar cell side near the optimum output operating point Amax.

  The reason why the load connected to the solar cell is held at the optimum output operating point (near Amax) will be further described with reference to FIG. For example, when a solar cell is used at the maximum output operating point Amax at “large irradiation amount”, the power is voltage × current. Therefore, when the voltage value at this point is Vmax and the current value is Imax, the power that can be extracted is Vmax. XImax. On the other hand, consider the case where a solar cell is used at the operating point Ah of the load. If the current value Ih at the operating point Ah is, for example, a current corresponding to half the voltage Vmax at the current value Imax at the maximum output point Amax, the voltage value at the operating point Ah is 1/2 Vmax. At this time, as apparent from the output characteristics, there is almost no change in the current value between the current value Imax and the current value Ih. That is, the current value Ih at the operating point Ah is substantially the same current value (Ih≈Imax) as the current value Imax at the maximum output point Amax. Therefore, the electric power Ph that can be extracted at the operating point Ah is ½ Vmax × Ih, which is about ½ of the electric power Pmax that can be extracted at the maximum output point Amax.

  Similarly, in the case of “medium irradiation amount” and “low irradiation amount” in the output characteristics of the solar cell, the output power is about half of the maximum output operating point. As described above, the operating point (for example, Amax) at which the electric power that can be extracted at a certain irradiation amount is maximum hits the output characteristic by drawing a vertical line from the line of voltage V (for example, Vmax) on the horizontal axis in the figure. The area of the rectangle surrounded by the horizontal axis, vertical axis, horizontal line, and vertical line when the horizontal line is drawn from the operating point (Amax) to the current I line (eg, Imax) as the vertical axis from that point is maximized. It is a place. That is, if the output power (P) of the voltage (V) × current (I) at a specific operating point (for example, Amax) on the output characteristics is the maximum from any other operating point (for example, Ah), The maximum output operating point Amax is reached, and the voltage Vmax and current Imax at that time become the maximum output operating point. The operating voltage V at the maximum output operating point Amax that gives the maximum output power Pmax of the solar cell is substantially constant regardless of the amount of irradiation such as “medium irradiation amount” or “low irradiation amount” shown in FIG. It becomes a voltage value (Vmax).

  Here, in order to charge the secondary battery with the output voltage of the solar battery, considering the case where the secondary battery is directly connected to the solar battery and charged, the output voltage of the solar battery is It will drop to the charging voltage of the battery. For example, when a secondary battery having a voltage of 1/2 Vmax is directly connected to the solar battery having the characteristics shown in FIG. 4, the voltage of the solar battery also decreases to 1/2 Vmax. Assuming that “the irradiation amount is large”, the charging current that flows is Imax. Therefore, although the maximum value Pmax of the power that can be extracted is Vmax × Imax as described above, when the secondary battery is directly connected, only a power of ½ Vmax × Imax can be extracted. In view of the efficiency reduction of the output power, if a charge control circuit is provided between the solar battery and the secondary battery so that the output voltage of the solar battery becomes a predetermined value near the maximum output operating point (Vmax), The output power of the solar battery can be brought close to the maximum output power Pmax, and the secondary battery can be efficiently charged by the solar battery.

  Furthermore, when a plurality of types of solar cells can be connected as an input power source of the charging device, it is required to set an optimum output operating point for each of the plurality of types of solar cells. In other words, when a solar cell that is an input power source and a charging device are configured with a detachable connection part and a plurality of solar cells having different output characteristics can be used as an input power source, a plurality of solar cells are connected to the charging device. The charging efficiency of the secondary battery to be charged cannot be improved only by controlling the input voltage to be input to a predetermined value.

  When charging from a plurality of solar cells having different output voltage characteristics with different number of solar cells (number of panels), for example, the optimum operating voltage Vmax per cell (per panel) is 2 When the solar cell A connected in series and the solar cell C connected in series are used as an input power source, the solar cell A has two cells and the number of cells is small. However, there is an advantage that the price is low. In addition, the solar battery C has a number of cells as high as 6 and is expensive, but has a merit that charging to the same secondary battery is short because a lot of electric power can be taken out. Furthermore, if the charging time intermediate between the solar cell A and the solar cell C and the advantages and disadvantages of the price are taken into consideration, the number of cells of the solar cell as the input power source can be selected as four. Therefore, the user can select a plurality of types of solar cells according to his / her needs.

However, considering the voltage at each optimum output operating point in the solar cells A to C, the solar cell A is Vmax × 2 pieces = 2 Vmax, the solar battery B is Vmax × 4 pieces = 4 Vmax, and the solar cell C is Vmax × 6 pieces. = 6Vmax, and the voltage at the optimum output operating point is different. Therefore, when a solar cell with different output characteristics is used as an input power source, simply controlling the input voltage of the charging device to a predetermined voltage value significantly reduces the charging efficiency of the solar cell depending on the type of solar cell to be connected. I will let you.
Therefore, a main object of the present invention is to provide a charging device that includes a charging control circuit that operates a solar cell as an input power source at an optimum output operating point, and thereby can efficiently charge a secondary battery from the solar cell. There is.

Another object of the present invention is to provide a charging device for charging a secondary battery, comprising a charging control circuit capable of connecting a plurality of solar cells having different characteristics as an input power source.
Still another object of the present invention is to provide a charging device including a charge control circuit that is simple and inexpensive to operate a solar cell as an input power source at an optimum output operating point.

  To achieve the above object, typical features of the invention disclosed in the present application will be described as follows.

  According to one aspect of the present invention, there is provided a charging device including a charging control circuit for charging a secondary battery as an input power source by output power of a solar battery, wherein the charging control circuit has a plurality of different characteristics. The solar battery is configured to have a power supply connection part to which the solar battery can be attached and detached, and to control the charging current and the charging voltage in accordance with the output voltage of the solar battery connected to the power supply connection part.

  According to another aspect of the present invention, the charging control circuit controls a charging voltage and a charging current for charging the secondary battery based on an output voltage of a solar battery connected to the power connection unit. Switching control circuit, a charging voltage feedback circuit for feeding back a control signal for controlling the charging voltage to a set voltage value based on a charging voltage of the secondary battery to the switching control circuit, and the secondary battery A charging current feedback circuit for feeding back to the switching control circuit a control signal for controlling the charging current to a set current value based on the charging current of the switching control circuit based on the output voltage of the solar cell. In order to feed back a control signal for controlling the input voltage to the set input voltage value to the switching control circuit. An input voltage feedback circuit, the input voltage feedback circuit having input voltage setting means capable of setting a plurality of set input voltage values, and based on a control signal from the charging current feedback circuit, the switching control circuit Configured to control the value of the charging current controlled by the switching control circuit so that the input voltage of the switching control circuit becomes a predetermined voltage value selected based on a signal from the input voltage setting means of the input voltage feedback circuit. To do.

  According to still another feature of the present invention, the input voltage setting means includes an input voltage setting circuit capable of selecting an input voltage value corresponding to characteristics of the plurality of solar cells. Charging device.

According to still another aspect of the present invention, the input voltage setting means is configured to select a predetermined input voltage setting value based on the output voltage of the solar battery before charging the secondary battery.
According to still another aspect of the present invention, the charge control circuit includes a solar cell type determining unit for determining the characteristics of the solar cell, and the input voltage setting unit is determined by the solar cell type determining unit. A predetermined input voltage set value is selected on the basis of the type of the solar cell thus formed.

  According to still another aspect of the present invention, the charging voltage feedback circuit, the charging current feedback circuit, and the input voltage feedback circuit each include an operational amplifier, and a control signal of each feedback circuit is synthesized via the operational amplifier. And fed back to the switching control circuit.

  According to the above feature of the present invention, the charge control circuit has a power supply connection portion to which a plurality of solar cells having different characteristics can be attached and detached, and charging is performed according to the output voltage of the solar cell connected to the power supply connection portion. Since it comprises so that an electric current and a charging voltage may be controlled, the optimal output operation point can be set to each characteristic of a several solar cell, and charging power can be obtained efficiently from a solar cell.

  For example, referring to the output characteristic diagram of FIG. 4, when the secondary battery is charged with a voltage of 1/2 Vmax in the “irradiation amount” state, the charging control circuit causes the charging current I to be (Secondary battery charging power P = efficiency × maximum power Pmax of solar cell) = (secondary battery charging voltage 1/2 Vmax × secondary battery charging current I = efficiency × solar cell output voltage Vmax × solar cell Output current Imax) = (1/2 Vmax × secondary battery charging current I = efficiency × solar cell output voltage Vmax × solar cell output current Imax) From the following, assuming that the efficiency of the charging control circuit is 85%, for example: The charging current I of the secondary battery is I = 2 × 0.85Imax = 1.7Imax, which is approximately 1.7 times the charging current Imax when the secondary battery is directly connected to the solar battery. Can be charged with Thus, charging efficiency can be improved.

  According to the above feature of the present invention, the charging control circuit includes a switching control circuit, a charging voltage feedback circuit, a charging current feedback circuit, and an input voltage feedback circuit, and the input voltage feedback circuit includes a plurality of input voltage feedback circuits. An input voltage setting means capable of setting a set input voltage value, wherein a value of a charging current controlled by the switching control circuit based on a control signal from the charging current feedback circuit is determined by the input voltage of the switching control circuit; Since the control is performed so that a predetermined voltage value selected based on the signal from the input voltage setting means of the input voltage feedback circuit is obtained, it is possible to set an optimum output operating point for each characteristic of the plurality of solar cells, Charging power can be efficiently obtained from the battery.

  Further, since the charging voltage feedback circuit, the charging current feedback circuit, and the input voltage feedback circuit can be configured by an operational amplifier, a simple and inexpensive charging control circuit can be achieved.

  The above and other objects, and the above and other features of the present invention will become more apparent from the following description of the present specification and the accompanying drawings.

  Hereinafter, a charging device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a charging device according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of the charging device according to an embodiment of the present invention. Note that in the drawings for describing the embodiments, members having the same functions or elements are denoted by the same reference numerals, and repeated description thereof is omitted.

<About the configuration of the charging device>
A solar cell module 1 serving as an input power source includes, for example, a solar cell (cell) 1a composed of a PN junction of crystalline silicon and a discriminating element (for example, resistance element) 1b representing the type or characteristics of the solar cell. . As shown in FIG. 1, the solar cell module 1 is detachably connected to the main body of the charging device 40 via a connection portion 41. The connection part 41 has a common attachment / detachment mechanism so that a plurality of types of solar cell modules 1 can be connected. In the example shown in FIG. 1, a solar cell A in which two solar cells having an optimum output operating point voltage Vmax (see FIG. 4) are connected in series, and a solar cell having an optimum output operating point voltage Vmax. Four solar cells B connected in series and a solar cell C connected in series with six solar cells whose voltage at the optimum output operating point is Vmax have a common attachment / detachment mechanism.

  The auxiliary power supply unit 2 is a power supply unit that steps down the voltage Vi of the solar cell 1a and supplies a power supply voltage Vcc such as a microcomputer 11 and operational amplifiers 7g, 9e, 10g, and 10h described later. The auxiliary power supply unit 2 includes a DC converter (switching power supply circuit) 2a, a P-channel insulated gate field effect transistor (hereinafter referred to as “P-channel FET”) 2b, a rectifier diode 2c, a coil 2d, The capacitor 2e and the resistors 2f and 2g constitute a step-down switch power supply circuit, and step down the voltage Vi of the solar battery to generate the power supply voltage Vcc for the microcomputer 11 and the like.

  That is, the DC converter 2a constitutes a step-down converter, and the P-channel FET 2b is set so that the value obtained by dividing the output voltage by the potentiometers of the resistors 2f and 2g becomes a predetermined value set in the DC converter 2a. By switching, a desired power supply voltage Vcc is output. The resistance values of the resistors 2f and 2g are set so that a value obtained by dividing the desired power supply voltage Vcc by the resistors 2f and 2g becomes a comparison value set in a comparison circuit (not shown) of the DC converter 2a.

  The battery pack 3 is a battery pack to be charged, and includes a battery set 3a to which a secondary battery of one cell or more is connected, and a battery type discrimination including a discrimination resistor for discriminating the type or number of cells of the battery set 3a. It comprises an element 3b and a temperature sensitive element 3c such as a thermistor set in the vicinity of the battery set 3a for monitoring the battery temperature. The battery set 3a is composed of, for example, a lithium ion secondary battery.

The battery type discriminating means 4 has a function of discriminating the type of secondary battery of the battery set 3a from the battery type discriminating element 3b of the battery pack 3, and is composed of a resistor 4a. The battery type of the secondary battery 3a is a value obtained by dividing the power supply voltage Vcc by the resistor 4a and the battery type discrimination resistor 3b set in the battery pack 3, and an A / D port (analog- It is determined by inputting to the digital conversion port) 11e. Here, the battery type is, for example, the difference in the type of the secondary battery itself such as a lithium ion secondary battery, a nickel-cadmium secondary battery, a nickel hydride secondary battery, or the number of cells in the same type of secondary battery such as a lithium ion battery. (For example, a difference between 4 cells, 5 cells, etc.). The reason for determining the battery type is that the charge control method differs depending on the battery type, and it is necessary to perform appropriate charging for each battery type.
The battery temperature detection means 5 is a battery temperature detection means composed of resistors 5a and 5b. As the battery temperature, a value obtained by dividing the power supply voltage Vcc by the resistor 5a and the parallel resistance of the resistance value of the resistor 5b and the temperature sensing element 3c in the battery pack 3 is input to an A / D port 11e of the microcomputer 11 described later. Detect by.

The smoothing capacitor 6 is a smoothing capacitor connected in parallel to the solar cell 1a.
The input voltage feedback circuit 7 includes an operational amplifier 7g, voltage dividing resistors 7a and 7b connected to the non-inverting input part (+) of the operational amplifier 7g, and a voltage dividing resistor 7c connected to the inverting input part (−) of the operational amplifier 7g. , 7d, 7e, 7f. The voltage dividing resistors 7a and 7b divide the output voltage Vi of the solar cell serving as an input power source, and the divided value is input to the non-inverting input part (+) of the operational amplifier 7g. The voltage dividing resistors 7c and 7d divide the power supply voltage Vcc, and set voltage (hereinafter referred to as voltage dividing) for holding the output voltage Vi of the solar cell, that is, the input voltage Vi to the charge control circuit at a predetermined voltage value. The voltage value set by the resistors 7c and 7d is referred to as “first input voltage setting value”) and is supplied to the inverting input section (−) of the operational amplifier 7g. Here, the microcomputer 11 side terminal of the resistor 7e or 7f is normally clamped to a high signal, but the microcomputer side terminal of the resistor 7e or resistor 7f is selected to be a low signal corresponding to the type of the solar cell 1a. Is done.

  That is, by outputting a low signal to the resistor 7e from an output port 11d of the microcomputer 11 to be described later, the set value of the input voltage input to the inverting input portion (−) of the operational amplifier 7g, the power supply voltage Vcc and the resistor 7c, The voltage can be set to a divided voltage value between the resistor 7d and the resistor 7e in parallel (hereinafter referred to as “second input voltage setting value”). The second input voltage set value is set to a value smaller than the first input voltage set value set by only the resistors 7c and 7d, for example.

  Similarly, by outputting a low signal from the output port 11d of the microcomputer 11 to the resistor 7f, the power supply voltage Vcc is divided between the resistor 7c and the parallel resistance of the resistor 7d and the resistor 7f (hereinafter referred to as “third input voltage”). It can be set to “set value”. The third input voltage set value is set to a value smaller than the second input voltage set value, for example. In this way, the first input voltage setting value, the second input voltage setting value, and the third input voltage setting value correspond to the types A, B, and C of the solar cell 1 connected as the input power source shown in FIG. Is set to obtain the optimum operating voltage. In the above setting example, when the solar cell A is connected, the third input voltage set value is set. When the solar cell B is connected, the solar cell C is connected to the second input voltage set value. The first input voltage set value is set.

  The output voltage Vi of the solar cell 1 is divided by the detection resistors 7a and 7b, input to the non-inverting input part (+) of the operational amplifier 7g, and input to the inverting input part (-). Compared with a desired one of the second input voltage set value or the third input voltage set value, the optimum output operating voltage (for example, Vmax) is controlled so that the maximum power Pmax corresponding to the type of the solar cell 1 can be output. The Thereby, the output voltage Vi of the solar cell 1 is controlled to a voltage value at which the maximum power Pmax of the solar cell 1 can be taken out.

  The switching power supply circuit 8 constitutes a power supply for controlling the charging voltage Vc and the charging current Ic. The switching power supply circuit 8 includes a DC converter 8a, a P-channel FET 8b, a rectifier diode 8c, a coil 8d, and a smoothing capacitor 8e. In the present embodiment, a step-down switching power supply circuit that steps down the output voltage Vi of the solar cell 1 to generate the charging voltage Vc is used. The DC converter 8a controls the charging voltage Vc and the charging current Ic based on a feedback control signal from a charging current feedback circuit 10 in which error control signals of a charging voltage feedback circuit 9 and an input voltage feedback circuit 7 described later are combined. .

  The charging voltage feedback circuit 9 includes resistors 9a, 9b, 9c and 9d, an operational amplifier 9e, and a diode 9f. The battery charging voltage Vc is divided by resistors 9a and 9b and input to the non-inverting input (+) of the operational amplifier 9e. The set value Vsc of the charging voltage is generated by dividing the power supply voltage Vcc by the resistors 9c and 9d, and is input to the inverting input section (−) of the operational amplifier 3e.

  The DC converter 8a switches the switching FET 8b based on the output control signal of the operational amplifier 9e so that the charging voltage divided by the resistors 9a and 9b becomes the charging voltage setting value Vsc set by the resistors 9c and 9d. Control. Based on the output control signal of the operational amplifier 9e, the charging voltage setting value Vsc set by the resistors 9c and 9d is set to a limit voltage value for preventing the secondary battery voltage Vc from rising to a voltage equal to or higher than this setting value. Switching control of the drive signal of the switching FET 8b is performed by the converter 8a. That is, when the secondary battery voltage Vc is lower than the set value Vsc, switching control is performed to increase the battery voltage Vc. Conversely, when the secondary battery voltage Vc is higher than the set value Vsc, the secondary battery voltage is Switching control is performed so as to decrease Vc. Thus, a predetermined secondary battery voltage Vc that is equal to or lower than the set value Vsc can be maintained. The secondary battery voltage Vc is controlled to a voltage equal to or lower than the voltage Vi output from the solar battery 1 to the switching power supply circuit 8.

  The charging current feedback circuit 10 includes a first stage operational amplifier 10g and a subsequent stage operational amplifier 10h. The first stage operational amplifier 10g constitutes an inverting amplifier circuit together with the shunt resistor 10a for detecting the charging current Ic, the input resistors 10b and 10c, and the feedback resistor 10d, and can detect a relatively small charging current. A highly sensitive current amplifier is constructed. The post-stage operational amplifier 10h constitutes a comparison amplifier circuit, and the output of the first-stage operational amplifier 10g is input to the non-inverting input section (+) of the post-stage operational amplifier 10h via the input resistor 10e, and the inverting input section (-). The feedback signal (output of the operational amplifier 7g) from the input voltage feedback circuit 7 is input via the input resistor 10f. The output of the post-stage operational amplifier 10h is fed back to the DC converter 8a of the switching power supply circuit 8 through the diode 10i.

  According to this embodiment, the output via the diode 10i of the post-stage operational amplifier 10h is commonly connected to the output via the diode 9f of the operational amplifier 9e constituting the charge voltage feedback circuit 9 described above. That is, the output of the operational amplifier 9e and the output of the operational amplifier 10h are commonly connected in a wired OR format. Thereby, the input voltage Vi by the solar cell 1 is controlled corresponding to the magnitude of the charging current Ic while suppressing the charging voltage Vc to a voltage equal to or lower than the predetermined voltage value Vsc. In general, operational amplifiers 10g and 10h used in each stage are incorporated in one package (DIP or SOP package) by a semiconductor integrated circuit technology. Since an operational amplifier incorporated in one package may include an operational amplifier circuit connected in multiple stages, if such an operational amplifier circuit connected in multiple stages is adopted as the previous operational amplifier 10g, the detection sensitivity of charging current is further increased. Can be improved.

  According to such a feedback circuit 10, when a charging current Ic flows through the shunt resistor 10a, a negative potential of charging current (Ic) × shunt resistor (10a) × (−1) is applied to the non-inverting input portion of the operational amplifier 10g ( -). Since the operational amplifier 10g constitutes an inverting amplifier circuit together with the resistors 10b, 10c, and 10d, the voltage is 10d / 10c times the negative voltage value proportional to the charging current Ic input to the non-inverting input part (−) of the operational amplifier 10g. The value is output from the operational amplifier 10g and can be detected with high sensitivity even with a relatively small charging current. The output of the operational amplifier 10g is input to the non-inverting input part (+) of the operational amplifier 10h. On the other hand, since the feedback signal from the input voltage feedback circuit 7 is input to the inverting input section (−) of the operational amplifier 10h, the operational amplifier 10h is connected to the detection signal output of the charging current Ic and the input voltage (output voltage of the solar cell). ) Operates as a comparison amplifier circuit that compares Vi.

  When the input voltage (output voltage of the solar cell 1) Vi of the charging device 40 rises or falls below the input voltage setting Vsi set in the input voltage feedback circuit 7, the switching power supply circuit is based on the feedback output from the operational amplifier 7g. 8, the charging voltage Vc and the charging current Ic are controlled. That is, a virtual short circuit (imaginary short) in which the input potential difference between the non-inverting input unit (+) and the inverting input unit (−) in the operational amplifier 10h is zero within a range where the charging voltage Vc does not exceed the predetermined setting voltage Vsc. Thus, switching control is performed by the switching power supply circuit 8.

  In such switching control, if the input voltage Vi rises above the input voltage setting Vsi, the input voltage Vi rises so that both input parts (+) and (−) of the operational amplifier 7g in the input voltage feedback circuit 7 are increased. Unbalanced. Further, since the output of the operational amplifier 7g is inputted to the non-inverting input part (+) and the inverting input part (-) of the operational amplifier 10h of the charging current feedback circuit 10, both input parts (+) (-) of the operational amplifier 10h. There is no balance between them. Then, the switching power supply circuit 8 performs switching so that the input portions of the operational amplifiers 7g and 10h are balanced based on the feedback signal from the operational amplifier 10h. By performing this switching, the charging current Ic is increased so that the input voltage Vi decreases to the input voltage set value Vsi.

  Conversely, when the input voltage (solar cell voltage) Vi drops below the input voltage setting value Vsi set in the input voltage feedback circuit 7, the switching power supply circuit 8 sets the charging current Ic and the input voltage Vi sets the input voltage. Decrease to a value that increases to Vsi. In this way, when the irradiation amount increases and the voltage of the solar cell 1 increases, the charging current Ic is increased. Conversely, when the irradiation amount decreases and the voltage of the solar cell 1 decreases, charging is performed. The switching power supply circuit 8 is controlled so as to reduce the current Ic. As a result, the output voltage Vi of the solar cell 1 is controlled to a predetermined set value Vsi (a voltage near the optimum output operating point Vmax) having a voltage value higher than the charging voltage Vc.

The microcomputer 11 includes a CPU 11a, output ports 11b, 11c, and 11d, A / D ports 11e and 11f, and a memory unit such as a ROM and a RAM (not shown), and various types based on various detection input signals. The control signal is output. Note that the memory unit (not shown) of the microcomputer 11 stores and holds battery type determination data, battery temperature data, charging voltage data, and the like of the battery pack 3 and also stores data related to the battery type of the solar cell module 1. .
The battery voltage detection circuit 12 includes resistors 12a and 12b connected in series across the charge output circuit, and inputs a voltage divided by both the resistors 12a and 12b to the A / D port 11f of the microcomputer 11. To determine the battery voltage.

  The charging on / off circuit 13 is a circuit for turning on / off the charging path, and includes two semiconductor switching elements including a PNP transistor 13e and an NPN transistor 13f, and includes a bias resistor 13a of the NPN transistor 13f, 13b, and bias resistors 13c and 13d of the PNP transistor 13e.

  When charging, the NPN transistor 13f is turned on by outputting a high signal (H signal) from the output port 11b connected to the resistor 13a of the microcomputer 11. When the NPN transistor 13f is turned on, the PNP transistor 13e is also turned on, whereby the charging circuit including the switching power supply circuit 8 is electrically connected to the battery pack (secondary battery) 3 and the battery pack 3 is charged. On the contrary, when charging is terminated, the NPN transistor 13f is turned off by outputting a low signal (L signal) from the output port 11b connected to the resistor 13a of the microcomputer 11. By turning off the NPN transistor 13f, the PNP transistor 13e is also turned off, the charging path between the charging circuit and the battery pack 3 is cut off, and charging is terminated.

  The charge state display circuit 14 is a charge state display circuit for notifying the user whether or not charging is in progress. It comprises resistors 14a, 14b, 14c, an LED 14d, and an N-channel FET 14e. During charging, by outputting a high signal from the output port 11c connected to the resistor 14b of the microcomputer 11, the N-channel FET 14e is turned on and the LED 14d is turned on. Conversely, when the battery is not charged, a low signal is output from the output port 11c connected to the resistor 14b of the microcomputer 11, thereby turning off the N-channel FET 14e and turning off the LED 14d.

  The input voltage detection circuit 15 is a detection circuit for detecting an input voltage Vi input from the solar cell 1 to the charging device 40, and includes a voltage dividing resistor of resistors 15a and 15b. The input voltage is divided by the resistors 15 a and 15 b, and the divided voltage is input to the A / D port 11 f of the microcomputer 11, whereby the input voltage is determined by the microcomputer 11.

  The solar cell type discriminating means 16 is a solar cell type discriminating means for discriminating the characteristics of the solar cell 1a connected to the connecting portion 41, and is composed of a resistor 16a. The solar cell type (1a) of the solar cell module 1 is a value obtained by dividing the constant power supply voltage Vcc by the resistor 16a and the resistor 1b constituting the solar cell type discriminating element set in the solar cell module 1. By inputting to the A / D port 11 f of the microcomputer 11, comparison is made with the data stored in the memory in the microcomputer to make a determination. As used herein, the solar cell type refers to a plurality of solar cells A, B, and C having different operating points, as described above with reference to FIG. In order to efficiently charge the solar cell 1, it is necessary to control the voltage of the solar cell near the optimum output operating point, and the reason for determining the solar cell type is to determine this operating point.

<About the operation of the charging device>
Next, the operation of the charging device 40 according to the embodiment of the present invention will be described with reference to the circuit block diagram of FIG. 2 and the control flowchart of FIG.
First, when the solar cell 1 as an input power source is connected to the charging device 40, the charging device 40 enters an operating state using the solar cell 1 as a power source.

  In order to notify the user that the battery is not charged before the secondary battery 3a of the battery pack 3 is mounted, the LED 14d of the charge state display circuit 14 is turned off (step 401). In this case, in order to turn off the LED 14d, a low signal is output from the output port 11c connected to the resistor 14b of the microcomputer 11 to turn off the FET 14e.

  Next, it is determined whether or not the battery pack 3 is mounted on the charging device 40. The connection of the battery pack 3 is determined by, for example, a change in the detection signal of the battery temperature detection means 4 input to the A / D port 11e of the microcomputer 11 (step 402).

  Next, the battery type of the battery pack 3 is determined based on the detection signal from the battery type detection means 4 (step 403). The battery type of the battery pack 3 is set corresponding to the resistance value of the battery type discriminating element 3b in the battery pack 3. For example, the difference in the type of structure such as a lithium ion battery, a nickel metal hydride battery, a nickel-cadmium battery, etc. Even in the battery pack 3 having the same structure, the battery type discriminating element 3b based on the difference in the voltage range such as 14.4V or 18V or the number of battery sets in the battery pack 3 as in the case of the lithium ion secondary battery. The resistance value is set.

  Next, based on the detection signal from the solar cell type discriminating means 16, the battery type of the solar cell 1 is discriminated (step 404). For example, if the example of discrimination | determination of multiple types of solar cells A, B, and C shown in FIG. 1 is demonstrated, as above-mentioned, the solar cell A in which the two cells were connected in series is the optimal output of one cell. Assuming that the operating point is Vmax, the optimum operating voltage is 2 Vmax. Similarly, the solar cells B and C are respectively connected in series of 4 and 6, and the optimum output operating point is 4 Vmax and 6Vmax. Therefore, it is necessary to discriminate the battery type of the solar cell 1 based on the detection signal from the solar cell type discriminating means 16, and in the solar cells A, B and C, the resistance of the resistor 1b which functions as a solar cell type discriminating element. By setting the values to different resistance values a, b, and c, the solar cell type is determined.

  Such a solar cell type detection method based on the solar cell type discrimination element 1b installed in the solar cell module 1 is illustrated as an example, and other discrimination methods may be used. For example, there is a method of detecting the voltage Vi of the solar cell 1a of the solar cell module 1 by the input voltage detecting means 15 and discriminating the solar cell type based on the detected voltage Vi of the solar cell. For example, when the solar cell voltage before charging is in the range of V1 to V2 (however, V1 <V2), it is determined as solar cell A, and when it is in the range of V2 to V3 (where V2 <V3), the solar If it is determined that the battery is B and is in the range of V3 to V4 (however, V3 <V4), it can be determined that the solar battery C.

  Next, the set value Vsi of the input voltage Vi of the charging device 40 to be controlled is set based on the solar cell type of the solar cell module 1 detected in step 404 (step 405). For example, when it is determined in step 404 that the solar cell connected by the solar cell type determination unit 16 is the solar cell A, the set value Vsi of the input voltage Vi is set to the above-described third input voltage set value Vsi = 2Vmax. Therefore, a low signal is output from the output port 11d connected to the resistor 7e of the microcomputer 11. Similarly, when it is determined that the battery type of the connected solar cell module 1 is the solar cell B, the microcomputer 11 sets the set value Vsi of the input voltage Vi to the above-described second input voltage set value Vsi = 4Vmax. A low signal is output from the output port 11d connected to the resistor 7f. Similarly, when the solar cell C is determined, the output connected to the resistors 7e and 7f of the microcomputer 11 is set in order to set the set value Vsi of the input voltage Vi to the above-described first input voltage set value Vsi = 6Vmax. A high signal (open state) is held so as not to output a signal from the port 11d.

  Next, charging is started (step 406). Charging is started by outputting a high signal from the output port 11b connected to the resistor 13a of the microcomputer 11, thereby turning on the NPN transistor 13f and the PNP transistor 13e, and conducting the charging path connecting the switching power supply circuit 8 and the battery pack 3. This is done by setting a state.

  When charging is started, the LED 14d of the charging state display circuit 14 is lit in red, for example, in order to notify the user of the start of charging (step 407). 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.

  After the start of charging, it is determined whether or not the battery is fully charged (step 408). A well-known method can be adopted as a method for determining full charge. In an example of the full charge determination method in the present embodiment, for example, when the battery pack 3 charges the lithium ion secondary battery 3a, when the battery voltage detected by the battery voltage detection circuit 12 reaches a predetermined value, the battery pack 3 is fully charged. Is determined.

  The predetermined value of the battery voltage determined as full charge at this time is based on the battery type detected in step 403, for example, 4 cells × 4.2V = 16.8V in the case of a 4 cell lithium ion secondary battery 3a. In the case of the 5-cell lithium ion secondary battery 3a, it may be set to 4.2 V per cell, such as 5 cells × 4.2 V = 21 V. The predetermined value to be set is not limited to such a voltage value. In the case of a nickel-cadmium battery, for example, a method can be adopted in which charging is determined to be full when the battery temperature detected by the battery temperature detecting means 5 reaches a predetermined temperature or higher during charging.

  If it is determined in step 408 that the battery is fully charged, charging is terminated (step 409). The end of charging is performed by turning off the NPN transistor 13f and the PNP transistor 13e by outputting a low signal from the output port 11b connected to the resistor 13a of the microcomputer 11 and cutting off the charging path between the switching power supply circuit 8 and the battery pack 3. Is done by. When the charging is finished in step 409, the LED 14d of the charging state display circuit 14 is turned off to notify the user that the charging is finished (step 410). To turn off the LED 14d, a low signal is output from the output port 11c connected to the resistor 14b of the microcomputer 11 to turn off the FET 14e.

  Next, it is determined whether or not the battery pack 3 has been removed from the charging device 40 (step 411).

  As will be apparent from the above description of the embodiment, according to the present invention, a charging device (40) using one selected from a plurality of solar cells (A, B, C) as an input power supply is provided. The operating point (output voltage Vi and output current Ii) in the output characteristics of the solar cell can be controlled to the optimum output operating point according to the output characteristics of the plurality of solar cells (1) serving as input power sources. . Thereby, the charging efficiency by a solar cell can be improved.

  The voltage setting (Vsi) and the current setting (Isi) for obtaining the optimum output operating point of the solar cell are an input voltage feedback circuit (7) constituted by an operational amplifier and a charging current feedback circuit (10) constituted by the operational amplifier. Therefore, charging efficiency can be improved with a relatively simple circuit configuration.

  Further, the charging current feedback circuit (10) includes an inverting amplifier using a first-stage operational amplifier (10g) for detecting and amplifying the charging current, a setting error signal of the charging current (Ii), and setting of the input voltage (Vi). Since a comparison amplifier using a post-stage operational amplifier (10h) that compares the error signal is connected in multiple stages, the combination circuit of the setting error signal of the charging current (Ii) and the setting error signal of the input voltage (Vi) is compared. It can be configured easily. In particular, even when the charging current is small, the charging current is detected by the front-stage operational amplifier, and is combined with the error signal of the input voltage setting by the rear-stage operational amplifier.

  In the description of the above embodiment, an example in which a lithium ion secondary battery is charged as a secondary battery of the battery pack has been described. However, in a battery pack charging device configured with another secondary battery such as a Nicad battery. The same effect can be obtained even if the above is applied.

  As mentioned above, the invention made by the present inventor has been specifically described on the basis of the embodiment. However, the present invention is not limited to the above embodiment, and can be changed without departing from the gist thereof. is there.

The block diagram of the charging device which concerns on one Embodiment of this invention. The circuit diagram of the charging device shown in FIG. Fig. 3 is a control flowchart of the charging apparatus shown in Fig. 2. The output characteristic figure of a solar cell.

1: Solar cell module 1b: Solar cell type discriminating element 2: Auxiliary power supply 2a: DC converter 2b: P channel FET 2c: Rectifier diode 2d: Coil 2e: Smoothing capacitor 2f, 2g: Resistance 3: Battery pack 3a: Battery set ( Secondary battery) 3b: Battery type discriminating element (resistance)
3c: Temperature sensing element (thermistor) 4: Battery type discrimination means 4a: Resistance 5: Battery temperature detection means 5a, 5b: Resistance 6: Smoothing capacitor 7: Input voltage feedback circuit 7a, 7b, 7c, 7d, 7e, 7f: Resistor 7g: operational amplifier 8: switching power supply circuit 8a: DC converter 8b: P-channel FET 8c: rectifier diode 8d: coil 8e: smoothing capacitor 9: charging voltage feedback circuits 9a, 9b, 9c, 9d: resistor 9e: operational amplifier 9f: diode 10: charging current feedback circuit 10a: shunt resistor 10b, 10c, 10d, 10f: resistor 10g, 10h: operational amplifier 10i: diode 11: microcomputer 11a: CPU
11b, 11c, 11d: Output port 11e, 11f: A / D port 12: Battery voltage detection circuit 12a, 12b: Resistor 13: Charging ON / OFF circuits 13a, 13b, 13c, 13d: Resistor 13e: PNP transistor 13f: NPN Transistor 14: Charge state display circuits 14a, 14b, 14c: Resistance 14d: LED 14e: N-channel FET
15: Input voltage detection circuit 15a, 15b: Resistance 16: Solar cell type discriminating means 16a: Resistance 40: Charging device 41, 42: Connection part

Claims (6)

  A charging device comprising a charging control circuit for charging a secondary battery as an input power source by the output power of the solar battery, wherein the charging control circuit has a power supply connection part that can attach and detach a plurality of solar batteries having different characteristics. And a charging device configured to control a charging current and a charging voltage corresponding to an output voltage of a solar cell connected to the power supply connection portion.   The charging control circuit includes a switching control circuit for controlling a charging voltage and a charging current for charging the secondary battery based on an output voltage of a solar battery connected to the power supply connection unit, and the secondary battery. A charging voltage feedback circuit for feeding back to the switching control circuit a control signal for controlling the charging voltage to a set voltage value based on the charging voltage, and the charging current based on the charging current of the secondary battery. A charging current feedback circuit for feeding back a control signal for controlling to a set current value to the switching control circuit, and an input voltage of the switching control circuit is controlled to a set input voltage value based on an output voltage of the solar cell. Input voltage feedback circuit for feeding back a control signal to the switching control circuit. The input voltage feedback circuit includes input voltage setting means capable of setting a plurality of set input voltage values, and is controlled by the switching control circuit based on a control signal from the charging current feedback circuit. The charging current value is configured to be controlled so that the input voltage of the switching control circuit becomes a predetermined voltage value selected based on a signal from the input voltage setting means of the input voltage feedback circuit. The charging device according to claim 1.   The charging apparatus according to claim 2, wherein the input voltage setting means includes an input voltage setting circuit capable of selecting an input voltage value corresponding to characteristics of the plurality of solar cells.   The said input voltage setting means was comprised so that a predetermined | prescribed input voltage setting value might be selected based on the output voltage of the said solar cell before charging the said secondary battery, It was described in Claim 3 characterized by the above-mentioned. Charging device.   The charge control circuit includes a solar cell type determining unit for determining the characteristics of the solar cell, and the input voltage setting unit is a predetermined unit based on the type of solar cell determined by the solar cell type determining unit. The charging device according to claim 3, wherein the charging device is configured to select an input voltage set value.   Each of the charging voltage feedback circuit, the charging current feedback circuit, and the input voltage feedback circuit includes an operational amplifier, and control signals of the feedback circuits are synthesized via the operational amplifiers and fed back to the switching control circuit. The charging device according to any one of claims 2 to 5, wherein the charging device is configured as described above.

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