JP2010081711A - Charging circuit, charging circuit control method and charging circuit control program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging circuit, a charging circuit control method and a charging circuit control program, capable of highly efficiently charging a storage battery by preventing the deterioration of the storage battery due to a fine charging current. <P>SOLUTION: The charging circuit for charging a battery pack 2 with the power generated by a solar cell 1 includes: a switching element 5 for switching between a loop 2 through which a charging current flows from an inductance 4 to the battery pack 2 and a loop 1 through which the current returns from the inductance 4 to the solar cell 1 without intervention of the battery pack 2. A calculating section 8a calculates a switching time of the switching element 5 in advance from an opening voltage of the solar cell 1, a short circuit current and the performance of the inductance 4. A switching control section 8b transmits a PWM signal decided from the switching time calculated in advance by the calculating section 8a, thereby switching-controlling the switching element 5. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a charging circuit, a charging circuit control method, and a charging circuit control program.

  Conventionally, when weather observation or monitoring is performed in a place where it is difficult to secure a power supply infrastructure, a solar cell system combining a solar cell and a storage battery can be used as a power source for data collection and information transmission. In the solar cell system, for example, power generated by the solar cell is supplied to the load during the daytime, the storage battery is charged with surplus power, and necessary power is supplied by discharging from the storage battery at night.

  As an example of such a solar cell system, for example, Patent Documents 1 and 2 describe an independent solar power generation system in which a storage battery and a solar cell are combined. Specifically, Patent Document 1 discloses a Ni-MH (nickel-hydrogen) storage battery that is charged by a first converter connected to the output of the solar battery and a charger connected to the output of the first converter. And a second converter connected to the output of the first converter and the output of the electric double layer capacitor and connected to the Ni-MH battery via a backflow prevention diode, and connected to the output of the second converter. A stand-alone photovoltaic system with a load is described.

  Patent Document 2 discloses a solar cell that generates electric power by sunlight, a converter connected to the output of the solar cell, an electric double layer capacitor connected to the output of the converter, an output of the converter, and an electric double layer. Independent solar light comprising a plurality of chargers connected to capacitors, a plurality of Ni-MH batteries connected corresponding to the chargers, and a load connected to the outputs of the plurality of Ni-MH batteries A power generation system is described.

  Thus, when charging a storage battery with a solar battery, it is common to charge via a converter. The converter outputs a constant voltage to the storage battery with the solar battery as an input, and matches the output voltage with the charging voltage of the storage battery. Here, the generated electric power of the solar cell greatly fluctuates due to sunlight, but the fluctuation appears as an increase or decrease in the output current (charging current) of the converter. That is, even if the power generation amount decreases, the output voltage (charging voltage) of the converter does not change, and the output current (charging current) decreases.

JP 2000-250646 A JP 2001-069688 A

  However, normally, the optimum value is set for the charging current of the storage battery, and when the charging current becomes very small, the charging efficiency is remarkably lowered and the storage battery is not charged. In that case, most of the electric power input to the storage battery is converted into heat, but there is a problem that the deterioration of the storage battery proceeds due to this exothermic reaction.

  The present invention has been made to solve the above-described problems caused by the prior art, and prevents a deterioration of a storage battery due to a minute charging current and can be charged efficiently, a charging circuit control method, and a charging circuit. An object is to provide a control program.

  In order to solve the above-described problems and achieve the object, the charging circuit for charging the power generated by the solar battery to the storage battery includes an inductance connected to the solar battery, and an electric circuit through which a charging current flows from the inductance to the storage battery. And a switching element that switches an electric path for returning current from the inductance to the solar cell without going through the storage battery, and a switching control means that controls the switching element according to a switching time calculated in advance. Features.

  Further, a charging circuit control method for controlling a charging circuit that charges a storage battery with electric power generated by a solar battery includes an electric circuit through which a charging current flows from an inductance connected to the solar battery to the storage battery, and without passing through the storage battery. A calculation step of calculating a switching time of a switching element for switching an electric path for returning a current from the inductance to the solar cell from information on the solar cell and the inductance, and the switching element according to the switching time calculated in advance by the calculation step And a switching control step for controlling the switching.

  In addition, a charging circuit control program for causing a computer to execute a method for controlling a charging circuit that charges a storage battery with electric power generated by a solar battery causes a charging current to flow from the inductance connected to the solar battery to the storage battery. A calculation procedure for calculating a switching time of a switching element for switching between an electric circuit and an electric circuit for returning current from the inductance to the solar cell without going through the storage battery from information on the solar cell and the inductance is executed. To do.

  According to the present invention, there is an effect that it is possible to prevent the storage battery from being deteriorated due to a minute charging current and to charge efficiently.

  Moreover, according to this invention, there exists an effect that it becomes possible to generate | occur | produce a pulse-shaped charging current efficiently.

  Embodiments of a charging circuit, a charging circuit control method, and a charging circuit control program according to the present invention will be described below with reference to the accompanying drawings. In Example 1, a case where the present invention is applied to a solar cell system in which a solar cell and a storage battery are combined will be described.

[Configuration of Solar Cell System According to Example 1]
First, the configuration of the solar cell system according to Example 1 will be described. FIG. 1 is a block diagram illustrating the configuration of the solar cell system according to the first embodiment. As shown in the figure, this solar cell system includes a solar cell 1, an assembled battery 2, a series resistor 3, an inductance 4, a switching element 5, a diode 6, a current measuring unit 7, and a control unit 8. With.

  Of the two electric circuits connecting the solar cell 1 and the assembled battery 2, a series resistor 3, an inductance 4, and a diode 6 are inserted into one of the electric circuits in order from the solar cell 1 side. The electric circuit between the inductance 4 and the diode 6 is connected to the other electric circuit connecting the solar cell 1 and the assembled battery 2 via the switching element 5.

  Here, the series resistor 3, the inductance 4, the switching element 5, the diode 6, the current measuring unit 7, and the control unit 8 constitute a charging circuit that charges the assembled battery 2 with the electric power generated by the solar cell 1.

  The solar cell 1 generates electric power by converting solar energy into electric energy. For example, the solar cell 1 in Example 1 has a maximum power generation capacity of 90 W, the maximum value of the open circuit voltage is 20 V, and the maximum value of the short circuit current is 5 A.

  The assembled battery 2 stores the electric power generated by the solar battery 1. For example, the assembled battery 2 in Example 1 is configured by connecting a plurality of Ni-MH storage battery cells in series in 10 cells. Here, each Ni-MH storage battery cell has a rated voltage of 1.2 V and a rated capacity of 100 Ah, for example. The assembled battery 2 has, for example, a rated voltage of 12 V, a rated capacity of 100 Ah, and a power storage capacity of 1200 Wh. The Ni-MH storage battery cell has a minimum chargeable current (for example, 1 A). If charging is continued below this level, the charging efficiency is remarkably lowered and the deterioration is promoted. It is desirable.

  The series resistor 3 is used for current measurement, and its resistance value is negligibly small.

  The inductance 4 is, for example, a coil and has a property of holding a current output from the solar cell 1.

  The switching element 5 controls the supply of the charging current to the assembled battery 2 under the control of the control unit 8. In the first embodiment, the switching element 5 is realized by an FET (Field Effect Transistor). When the switching element 5 is controlled to be on (short circuit), both terminals of the solar cell 1 are directly connected to both terminals of the inductance 4. At this time, the current output from the solar cell 1 returns to the solar cell 1 via the series resistor 3, the inductance 4, and the switching element 5 (loop 1), and no charging current flows to the assembled battery 2. At this time, the assembled battery 2 is not short-circuited because of the diode 6. On the other hand, when the switching element 5 is controlled to be off (opened), the current output from the solar cell 1 returns to the solar cell 1 via the series resistor 3, the inductance 4, the diode 6, and the assembled battery 2. (Loop 2). That is, when the switching element 5 is controlled to be turned off, a charging current flows from the inductance 4 to the assembled battery 2 via the diode 6.

  The diode 6 has an anode terminal connected to the inductance 4 and a cathode terminal connected to the assembled battery 2. The direction of the current flowing to the assembled battery 2 is controlled by the diode 6 only in the direction in which the assembled battery 2 is charged.

  The current measuring unit 7 measures the current flowing from the solar cell 1 to the inductance 4. Specifically, the current measuring unit 7 measures a current flowing from the solar cell 1 to the inductance 4 by measuring a voltage generated at both ends of the series resistor 3.

  In addition, although Example 1 demonstrates the case where an electric current is measured using the series resistance 3, the method of measuring the electric current which flows into the inductance 4 from the solar cell 1 is not necessarily restricted to this. For example, a component capable of measuring the magnitude of the magnetic field generated around the current and outputting a voltage corresponding to the measured magnitude of the magnetic field may be used. In that case, the said component is connected between the solar cell 1 and the inductance 4, and the output current from the solar cell 1 is made to conduct | electrically_connect to a component. And the current measurement part 7 measures the electric current which flows from the solar cell 1 to the inductance 4 by measuring the voltage output from components.

  As shown in FIG. 1, the control unit 8 includes a calculation unit 8 a and a switching control unit 8 b, and switches the switching element 5 on / off according to a previously calculated switching time, thereby charging the assembled battery 2. To control the supply. Below, the switching control part 8b is demonstrated first.

  The switching control unit 8b switches on / off of the switching element 5 according to the switching time calculated in advance by the calculation unit 8a. Specifically, the switching control unit 8 b transmits a PWM (Pulse Width Modulation) signal determined by the period (frequency) and the duty ratio notified from the calculation unit 8 a to the switching element 5. The switching of the switching element 5 is controlled.

  The PWM signal is an on / off repetition signal determined by a cycle and a duty ratio. The duty ratio is a ratio of the on time determined by on time / (on + off time). The larger the duty ratio, the longer the on time (connected time). For example, a PWM signal having a period of 50 μsec and a duty ratio of 50% repeats a signal that is on for 25 μsec and off for 25 μsec. If the duty ratio is increased to 80% while the period is 50 μsec, a signal of ON for 40 μsec and OFF for 10 μsec is repeated.

  Here, the relationship between the current flowing from the solar cell 1 to the inductance 4 and the charging current supplied to the assembled battery 2 as a result of the control by the switching control unit 8b will be described. FIG. 2 is a diagram for explaining the relationship between the current flowing from the solar cell to the inductance and the charging current supplied to the assembled battery.

  In FIG. 2, when the switching control unit 8 b controls the switching element 5 to be on (ON), a certain time is required until the current in the loop 1 is saturated because of the inductance 4. Thereafter, the switching control unit 8b controls the switching element 5 to be turned off, so that the saturated current becomes the charging current for the assembled battery 2. That is, the switching control unit 8b can repeatedly supply the pulsed current to the assembled battery 2 by repeatedly turning on / off the switching element 5.

In the figure, (a) shows the change over time of the current _Ip output from the solar cell 1, the vertical axis shows the magnitude of the current _Ip , and the horizontal axis shows the time t. . On the other hand, (b) shows the change over time of the charging current I _C supplied to the assembled battery 2, the vertical axis shows the magnitude of the charging current I _C , and the horizontal axis shows the time t. .

First, as shown in the figure, it is assumed that at the time of t = 0, I _p and I _C are 0 and the switching element 5 is turned on. As time t elapses, I _p gradually increases as shown in FIG. When the ON time calculated by the calculation unit 8a elapses, the switching control unit 8b controls the switching element 5 to be turned off, and the charging current I _C flows through the assembled battery 2 as shown in FIG. It becomes like this.

Thereafter, as time t further elapses, I _p gradually decreases as shown in FIG. Then, when the off time calculated by the calculation unit 8a has elapsed, the switching control unit 8b controls the switching element 5 to be turned on, and the charging current I _C flowing through the assembled battery 2 is changed as shown in FIG. It becomes zero.

As described above, the switching control unit 8b repeats the control of the charging current I _C according to the on time and the off time calculated by the calculation unit 8a, whereby the pulsed charging current I _C is sequentially supplied to the assembled battery 2. The

  In the first embodiment, the switching control unit 8b performs the switching control as described above only when the amount of solar radiation decreases. Specifically, the switching control unit 8b compares the magnitude of the current measured by the current measurement unit 7 with a threshold (for example, 1A), and determines that the magnitude of the current is below the threshold (1A). Start control.

For example, when the amount of solar radiation is large and the power generation is sufficiently performed by the solar cell 1, the magnitude of the current measured by the current measuring unit 7 exceeds 1A, so that the switching control unit 8b includes the switching element 5 Continue to control off. Therefore, in this state, the assembled battery 2 continues to be charged with a charging current I _C that is greater than or equal to the minimum charging current. On the other hand, when the amount of solar radiation decreases during charging, the magnitude of the current measured by the current measuring unit 7 is less than 1A, and thus the switching control unit 8b starts switching control.

  In other words, when there is a sufficient amount of solar radiation and the short-circuit current of the solar cell 1 is 5 A (changes in the amount of solar radiation appear as changes in the short-circuit current), charging can be performed by connecting the assembled battery 2 as it is. A charging current exceeding 1 A (minimum current that can be charged) can be obtained, but when the amount of solar radiation decreases, the charging current may be below the minimum current that can be charged. In such a case, the switching control unit 8b according to the first embodiment switches a current path by switching control and performs charging using a pulsed current.

Now, the time (ON time) from when the switching element 5 is controlled to ON until the current in the loop 1 is saturated (more accurately, the current increases to near the short-circuit current of the solar cell 1), and the switching element There is a problem with the time (off time) until the current of loop 2 is used up after 5 is controlled to be off. If the on-control state is continued, the current saturates, and if the off-control state is continued thereafter, the current disappears. However, since the number of on / off operations is directly related to the charging current amount, It is desirable to repeat off. However, if you shorten the much switching time, it is not possible to save the current until the off and will short-circuit current I _s close before the current is saturated. It is necessary to set a switching time so that a sufficient amount of current can be accumulated during the on-time and the switching frequency is increased. In Example 1, the calculation part 8a calculates the switching time beforehand from the open circuit voltage of the solar cell 1, the short circuit current, the performance of the inductance 4, the voltage of the assembled battery 2, and the like. Next, the calculation unit 8a will be described.

  The calculation unit 8 a calculates the switching time of the switching element 5 from the information about the solar cell 1 and the inductance 4 and the voltage of the assembled battery 2. Specifically, the calculation unit 8a in the first embodiment stores a calculation formula for calculating the switching time of the switching element 5, and substitutes the open-circuit voltage of the solar cell 1, the short-circuit current, the performance of the inductance 4, and the like into the calculation formula. Thus, the switching time is calculated. Further, the calculation unit 8a determines the cycle and duty ratio of the PWM signal from the calculated switching time, and notifies the switching control unit 8b of the determined cycle and duty ratio. Here, the calculation unit 8a in the first embodiment calculates the switching time in consideration of the influence of the temperature and the amount of solar radiation. For example, the calculation unit 8a calculates the switching time at regular intervals (every minute, etc.) Notify the controller 8b.

That is, open-circuit voltage V _o of the solar cell 1 varies under the influence of temperature, the short-circuit current I _s varies by receiving the variation in the amount of solar radiation. Therefore, calculation unit 8a opens the voltage V _o and the short-circuit current I _s is measured or estimated, by substituting the open-circuit voltage V _o and the short-circuit current I _s measured or estimated in the formula, the temperature and amount of solar radiation The switching time is calculated considering the influence. For example, the open-circuit voltage V _o can be directly measured by opening a separate switch connected to the output of the solar cell 1 or can be estimated by measuring the temperature of the solar cell 1. it can. Also, the short-circuit current I _s, when measured (short-circuit current I _s, which can be measured (while controlling to turn on the switching element 5) in short-circuit of the solar cell 1 is set longer the short time You may). The calculation unit 8a substitutes the open-circuit voltage V _o and the short-circuit current I _s measured or estimated in this way into the calculation formula.

In the first embodiment, calculation unit 8a is stored a formula, the open-circuit voltage V _o and the short-circuit current I _s measured or estimated switching time is calculated by substituting in the formula, the calculated switching time Although the method for determining the period and duty ratio of the PWM signal has been described, the present invention is not limited to this. For example, calculation unit 8a is open voltage V _o, the assembled battery 2 voltage V _b, the short-circuit current I _s, and the value L of the inductance of the inductance 4, calculation results may be a technique for storing a table that associates.

First, a process for deriving a calculation formula for calculating the switching time will be described. FIG. 3 is a diagram for explaining calculation of on-time and off-time, FIG. 4 is a diagram for explaining a case where a switching element (FET) is controlled to be on, and FIG. It is a figure for demonstrating the case where an element (FET) is controlled to OFF. In deriving the calculation formula, the inductance value of the inductance 4 is L, and as shown in FIG. 3, the solar cell 1 is connected to a voltage source (V _o ) and a resistance R _p = V _o / I _s (for example, 20V ÷ 5A = 4Ω). Further, Kirchhoff's second law is applied to each of the case where the switching element 5 is controlled to be on and the case where the switching element 5 is controlled to be off.

As shown in FIG. 4A, when the switching element 5 is controlled to be on, the following equation (1) is established according to Kirchhoff's second law.

When equation (1) is solved as i = 0 when t = 0, i becomes the following equation (2).

Then, the time the current flowing through the loop 1 reaches 90% of the short-circuit current I _s (see FIG. 4 (B)) is obtained as the following equation (3).

On the other hand, as shown in FIG. 5A, when the switching element 5 is controlled to be off, the following equation (4) is established according to Kirchhoff's second law.

When the equation (4) is solved as i = I _s when t = 0, that is, when the current transition is calculated by assuming that I _s (short-circuit current) flows in the loop 2 at t = 0, i becomes The following equation (5) is obtained.

In the case of V _o ≧ V _b (the voltage of the assembled battery 2), the current flowing through the loop 2 converges as shown in FIG. 5B and the following equation (6).

However, since it cannot wait until it converges, when the convergence time of 90% is obtained, the 90% convergence value of the current flowing through the loop 2 is expressed by the following equation (7).

を解くと、以下の（９）式となり、スイッチング素子５がオンに制御されている場合の９０％立ち上がり時間（（３）式）と同じ結果となる。

In order to obtain the time t at which this current is applied, the following equation (8)

Is solved, the following equation (9) is obtained, which is the same as the 90% rise time (equation (3)) when the switching element 5 is controlled to be on.

When V _o <V _b (the voltage of the assembled battery 2), the calculation converges to the equation (6), but this convergence value is negative, so that the diode 6 does not actually flow backward. Therefore, it does not become negative and the current only reaches zero. For this reason, what is necessary is just to obtain | require the time t until the electric current which flows through the loop 2 becomes zero. Substituting i = 0 into equation (5) yields the following equation (10).

Summarizing the rise and fall times of the current at the on and off times obtained by the above calculation, the current saturates when the switching element 5 is controlled to be on (precisely, the current reaches 90% of Is). The time required for (accumulating) is expressed by the following equation (11).

Further, when the switching element 5 is controlled to be off, the time required for the current to disappear (to be precise, 90% convergence or zero current) is expressed by the following equation (12).

Therefore, the calculation unit 8a stores the expressions (11) and (12), and calculates the switching time by substituting the open circuit voltage, the short circuit current, the performance of the inductance 4 and the like of the solar cell 1 into the calculation expression. At this time, the voltage _{Vb of the} assembled battery 2 increases as it is charged. If the fluctuation range of the voltage V _{b in} the first embodiment is 16 to 10 [V], for example, in the first embodiment, when the calculation unit 8a calculates the switching time, V _o (20V) ≧ V _b Suppose that it became (12V). V _o = 20 [V], I _s = 2 [A], L = 64 [μH], and V _b = 12 [V]. The short-circuit current Is is set to 2 [A] on the assumption that the amount of solar radiation is reduced.

When the calculation unit 8a calculates the values by substituting these values into the equations (11) and (12), t _ON — _90% = t _OFF — _90% = 14.7 [μs]. For this reason, from the calculation result that the calculation unit 8a only needs to switch on / off every 14.7 [μs], the PWM signal for the switching element 5 is converted into a cycle of 29.5 [μs] and a duty ratio of 50% ( As long as V _o ≧ V _b , the duty ratio is calculated as 50%).

[Procedure for Charging Method in Solar Cell System According to Embodiment 1]
Next, the procedure of the charging method in the solar cell system according to Example 1 will be described. FIG. 6 is a flowchart illustrating the procedure of the charging method in the solar cell system according to the first embodiment. In the initial state of the first embodiment, the switching element 5 is controlled to be in an off state, and a charging current flows from the inductance 4 to the assembled battery 2.

As shown in FIG. 6, in the solar cell system, the switching control unit 8b compares the magnitude of the current measured by the current measuring unit 7 with a threshold value I ₁ (for example, 1A) (step S1), and the magnitude of the current. Is determined to exceed the threshold value I ₁ (1A) (Yes at step S1), the switching control unit 8b repeats the process of determining the magnitude of the current and the threshold value I ₁ (1A).

On the other hand, when it is determined that the magnitude of the current is lower than the threshold value I ₁ (1A) (No in step S1), the switching control unit 8b starts the transmission of the PWM signal to the switching element 5 to thereby perform the switching control. Start (step S2). Here, the switching control unit 8b transmits a PWM signal determined by the period and the duty ratio notified from the calculation unit 8a to the switching element 5. In addition, since the calculation unit 8a in the first embodiment calculates, for example, a switching time every fixed period (every minute or the like) and notifies the switching control unit 8b, the PWM signal transmitted from the switching control unit 8b to the switching element. This also takes into account the effects of temperature and solar radiation.

  Then, the switching control unit 8b stops transmission of the PWM signal (step S4) when a certain time has elapsed (for example, 1 minute) after starting transmission of the PWM signal to the switching element 5 (step S3). Then, the switching element 5 is controlled to be turned off, and a charging current flows from the inductance 4 to the assembled battery 2.

Thereafter, the switching control unit 8b returns to the process of determining the current magnitude and the threshold value I ₁ (1A) again (step S1).

[Effect of Example 1]
As described above, the solar cell system according to the first embodiment includes, as a charging circuit, the inductance 4 connected to the solar cell 1, the electric path through which the charging current flows from the inductance 4 to the assembled battery 2, and the assembled battery 2. The switching element 5 that switches the current path from the inductance 4 to the solar cell 1 without switching, and the control unit 8 that controls the switching of the switching element 5 according to the switching time calculated in advance. In Example 1, when the switching element 5 is on (short circuit), the solar cell 1 is directly connected to the inductance 4, and when the switching element 5 is off (open), the solar cell 1 includes the inductance 4 and the diode. 6. Connected to a loop including the assembled battery 2. Further, the solar cell system according to the first embodiment obtains the cycle and duty ratio of the PWM signal to the switching element 5 from the open circuit voltage, short-circuit current, and the performance of the inductance 4 of the solar cell 1.

  For this reason, according to the first embodiment, since the charging current lower than the minimum charging current does not flow to the assembled battery 2, it is possible to prevent the storage battery from being deteriorated due to a minute charging current. Moreover, since the fall of the charging efficiency by supplying a very small charging current to the assembled battery 2 can be prevented, it becomes possible to charge efficiently. Further, according to the first embodiment, since the pulsed charging current is generated based on the pre-calculated switching time, the switching frequency can be obtained while obtaining a sufficient current, and the pulsed charging current can be efficiently obtained. Can be generated.

  In addition, according to the first embodiment, the switching control unit 8b performs switching control of the switching element 5 by transmitting a PWM signal determined from a switching time calculated in advance. For this reason, according to the first embodiment, since the pulsed charging current can be controlled simply by transmitting a predetermined PWM signal, the pulsed charging current can be generated easily and efficiently. Become.

  In addition, according to the first embodiment, the charging circuit further includes the current measurement unit 7 that measures the current flowing from the solar cell 1 to the inductance 4, and the switching control unit 8 b has the magnitude of the current measured by the current measurement unit 7. And a threshold value (for example, 1A), and switching control is started when it is determined that the magnitude of the current is less than 1A. For this reason, according to the first embodiment, when the amount of solar radiation is large, the switching control is not performed and the assembled battery 2 continues to be charged. Appropriate charging can be performed.

  According to the first embodiment, when the switching control unit 8b executes the switching control for a predetermined time (for example, 1 minute) after starting the switching control, the switching control unit 8b stops the switching control and is measured by the current measuring unit 7. The current magnitude and the threshold value (1A) are compared again. For this reason, according to the first embodiment, it is possible to follow the variation in the amount of solar radiation.

  Although the first embodiment of the present invention has been described so far, the present invention may be implemented in various different forms other than the first embodiment described above.

[Storage batteries other than Ni-MH storage batteries]
In Example 1, although the case where the assembled battery 2 comprised from several Ni-MH storage battery was used was demonstrated, this invention is not restricted to this, Even when another kind of storage battery is used, it is the same Can be applied to. In other words, the same effect as in the first embodiment can be obtained if a storage battery that is deteriorated by a minute charging current or has a reduced charging efficiency is used in the same manner as the Ni-MH storage battery.

[When the open voltage of the solar battery is smaller than the voltage of the assembled battery]
In Example 1, has been described a case open voltage V _O of the solar cell 1 is larger than the voltage V _b of the battery pack 2 as an example, the present invention is not limited to this, the solar cell 1 The present invention can be similarly applied when the open-circuit voltage V _O is smaller than the voltage V _{b of the} assembled battery 2. For example, _assuming that V _O = 8 [V], I _s = 2 [A], L = 64 [μH], and V _b = 12 [V], the calculation unit 8a has t _ON — _90% = 36.8 [μs]. , T _{OFF — i = 0} = 17.6 [μs]. Therefore, the calculation unit 8a uses the calculation result of the on time 36.8 [μs] and the off time 17.6 [μs] to realize this with the PWM signal, the period 54.4 [μs], and the duty ratio. 68% is determined. However, since V _o <V _b , if the PWM signal is not transmitted and the switching element 5 is controlled to be off, the assembled battery 2 cannot be charged from the solar cell 1 at all. For this reason, the switching control unit 8b always transmits a PWM signal to the switching element 5 from the beginning to perform charging with a pulsed current.

[Stopping switching control]
In the first embodiment, the method of stopping the switching control when the switching control is executed for a predetermined time (for example, 1 minute) has been described. However, the present invention is not limited to this. After starting the switching control, the switching control unit 8b compares the current magnitude of the loop 1 during the on-time of the PWM signal with a threshold value (for example, 2A), and determines that the current magnitude exceeds 2A. Switching control may be stopped. When current measurement is difficult with an on-time of about several tens of μs, the on-time may be increased only when current measurement is performed (for example, 1 ms).

[System configuration, etc.]
In the first embodiment, the configuration in which the calculation unit 8a that calculates the switching time of the switching element 5 in advance is provided in the control unit 8 of the charging circuit is described. However, the present invention is not limited to this. The calculation unit 8a may be provided in another computer different from the charging circuit, and only the calculation result may be transmitted to the switching control unit 8b of the charging circuit. Or you may notify the switching control part 8b because the operator of a solar cell system inputs the calculation result calculated by the calculation part 8a with which the computer different from a charging circuit was equipped. For example, short-circuit current due to the received change and the open-circuit voltage V _o due to receiving the handle open voltage V _o and the short-circuit current I _s of the solar cell 1 as a fixed value of (temperature effects, the effects of solar radiation treat as not account for variations in I _s) if it is effective for.

  In the first embodiment, the series resistor 3, the inductance 4, and the diode 6 are connected to one electric circuit (positive side). However, the present invention is not limited to this, and these circuit elements are connected to the other electric circuit. It is also possible to connect to (minus side). In this case, a series resistor 3, an inductance 4, and a diode 6 (the anode terminal is connected to the assembled battery 2 and the cathode terminal is connected to the inductance 4 in this order from the solar cell 1 side to the other electric circuit (minus side). The diode 6 is in the direction in which the assembled battery 2 is charged. The electric circuit between the inductance 4 and the diode 6 is connected to the positive electric circuit via the switching element 5.

  In addition, the processing procedure shown in the specification and drawings (such as FIG. 6), specific names (such as FIGS. 1 to 5), and information including various data and parameters are arbitrarily changed unless otherwise specified. be able to. In addition, each component of the illustrated charging circuit is functionally conceptual and does not necessarily need to be physically configured as illustrated. The calculation unit 8a and the switching control unit 8b may be performed by software processing on the microprocessor.

  As described above, the charging circuit, the charging circuit control method, and the charging circuit control program according to the present invention are useful when charging the storage battery with the electric power generated by the solar battery, and in particular, the storage battery with a small charging current. It is suitable for cases where it is required to prevent deterioration and decrease in charging efficiency.

1 is a block diagram illustrating a configuration of a solar cell system according to Example 1. FIG. It is a figure for demonstrating the relationship between the electric current which flows into an inductance from a solar cell, and the charging current supplied to an assembled battery. It is a figure for demonstrating calculation of on time and off time. It is a figure for demonstrating the case where a switching element (FET) is controlled by ON. It is a figure for demonstrating the case where a switching element (FET) is controlled by OFF. 3 is a flowchart illustrating a procedure of a charging method in the solar cell system according to Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solar cell 2 Assembly battery 3 Series resistance 4 Inductance 5 Switching element 6 Diode 7 Current measurement part 8 Control part 8a Calculation part 8b Switching control part

Claims (16)

A charging circuit for charging a storage battery with electric power generated by a solar battery,
An inductance connected to the solar cell;
A switching element for switching between an electric circuit (loop 2) through which a charging current flows from the inductance to the storage battery and an electric circuit (loop 1) from which the current returns from the inductance to the solar battery without going through the storage battery;
Switching control means for controlling the switching of the switching element according to a pre-calculated switching time;
A charging circuit comprising:   2. The charging circuit according to claim 1, wherein the switching control unit performs switching control of the switching element by transmitting a PWM signal determined from a switching time calculated in advance. The switching time calculated in advance includes the open voltage of the solar cell as “V _o ”, the short-circuit current of the solar cell as “I _s ”, the voltage of the storage battery as “V _b ”, and the inductance value of the inductance as “ 3, wherein when “V _o ≧ V _b ”, the switching time between the loop 1 and the loop 2 is equal when expressed by the following equation (1): Charging circuit.

The switching time calculated in advance includes the open voltage of the solar cell as “V _o ”, the short-circuit current of the solar cell as “I _s ”, the voltage of the storage battery as “V _b ”, and the inductance value of the inductance as “ L ”and when“ V _o <V _b ”, it is represented by the above formula (1) and the following formula (2):
The switching control means controls the switching element so that the time represented by the equation (1) is the loop 1 and the time represented by the equation (2) is the loop 2. The charging circuit according to claim 1, wherein:

Further comprising current measuring means for measuring a charging current to the storage battery,
When the open circuit voltage of the solar cell is larger than the voltage of the storage battery, the switching control unit compares the magnitude of the current measured by the current measuring unit with a first threshold value, and compares the magnitude of the current. The charging circuit according to any one of claims 1 to 3, wherein the switching control is started when it is determined that the current falls below the first threshold value.   When the switching control means executes the switching control for a predetermined time after starting the switching control, the switching control means stops the switching control, and compares the magnitude of the current measured by the current measuring means with the first threshold again. The charging circuit according to claim 5.   The switching control means, after starting the switching control, a current measured by the current measuring means, a current returning from the inductance to the solar cell without passing through the storage battery, and a second threshold value In comparison, if it is determined that the magnitude of the current exceeds the second threshold, the switching control is stopped, and the magnitude of the current measured by the current measuring means is compared with the first threshold again. 6. The charging circuit according to claim 5, wherein   5. The switching control unit according to claim 1, wherein the switching control unit always executes the switching control when an open voltage of the solar battery is smaller than a voltage of the storage battery. The charging circuit as described.   The charging circuit according to claim 1, further comprising calculation means for calculating the switching time from information on the solar battery, the storage battery, and the inductance. A charging circuit control method for controlling a charging circuit for charging a storage battery with electric power generated by a solar battery,
A switching element for switching between an electric circuit (loop 2) through which a charging current flows from the inductance connected to the solar battery to the storage battery and an electric circuit (loop 1) from which the current returns from the inductance to the solar battery without going through the storage battery A calculation step of calculating the switching time from information on the solar cell, the storage battery, and the inductance;
A switching control step of controlling the switching of the switching element according to the switching time calculated in advance by the calculation step;
The charging circuit control method characterized by including. In the calculation step, the open voltage of the solar cell is “V _o ”, the short-circuit current of the solar cell is “I _s ”, the voltage of the storage battery is “V _b ”, and the inductance value of the inductance is “L”. 11. The switching time represented by the equation (1) when “V _o ≧ V _b ” is satisfied, and the switching time between the loop 1 and the loop 2 becomes equal. 11. Charge circuit control method. In the calculation step, the open voltage of the solar cell is “V _o ”, the short-circuit current of the solar cell is “I _s ”, the voltage of the storage battery is “V _b ”, and the inductance value of the inductance is “L”. When “V _o <V _b ”, the switching time represented by the above formula (1) and the above formula (2) is calculated,
In the switching control step, the switching element is subjected to switching control so that the time represented by the equation (1) is the loop 1 and the time represented by the equation (2) is the loop 2. The charging circuit control method according to claim 10, wherein: A charging circuit control program for causing a computer to execute a method for controlling a charging circuit that charges a storage battery with electric power generated by a solar battery,
Computer
A switching element for switching between an electric circuit (loop 2) through which a charging current flows from the inductance connected to the solar battery to the storage battery and an electric circuit (loop 1) from which the current returns from the inductance to the solar battery without going through the storage battery The charging circuit control program which performs the calculation procedure which calculates switching time from the information regarding the said solar cell, the said storage battery, and the said inductance. A solar battery system that charges a storage battery with electric power generated by a solar battery,
The solar cell;
An inductance connected to the solar cell;
A switching element for switching between an electric circuit (loop 2) through which a charging current flows from the inductance to the storage battery and an electric circuit (loop 1) from which the current returns from the inductance to the solar battery without going through the storage battery;
Switching control means for controlling the switching of the switching element according to a pre-calculated switching time;
The storage battery;
A solar cell system comprising: The switching time calculated in advance includes the open voltage of the solar cell as “V _o ”, the short-circuit current of the solar cell as “I _s ”, the voltage of the storage battery as “V _b ”, and the inductance value of the inductance as “ The solar cell according to claim 14, wherein when “V _o ≧ V _b ”, the switching time between the loop 1 and the loop 2 is equal when “V _o ≧ V _b ”. system. The switching time calculated in advance includes the open voltage of the solar cell as “V _o ”, the short-circuit current of the solar cell as “I _s ”, the voltage of the storage battery as “V _b ”, and the inductance value of the inductance as “ L ”, and when“ V _o <V _b ”, it is expressed by the above formula (1) and the above formula (2),
The switching control means controls the switching element so that the time represented by the equation (1) is the loop 1 and the time represented by the equation (2) is the loop 2. The solar cell system according to claim 14.

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