CN103580105B - Charging device - Google Patents

Abstract

The present invention provides a method of performing rapid charging at an appropriate charging current (Ic) corresponding to the battery capacity even for secondary batteries with different battery capacities without performing capacity measurement processing for detecting the battery capacity of the secondary battery before fast charging. charging device. While the power supply unit is charging the secondary battery with direct current power, the charging voltage of the above direct current power can be made to be the terminal voltage of the secondary battery, and the voltage rise change rate calculated by the calculation unit is a predetermined set rise change rate The way to control the charging current of the above-mentioned DC power.

Description

charging device

technical field

The present invention relates to a charging device for charging a secondary battery, and particularly relates to charging with an optimum charging current matching the battery capacity of the secondary battery being charged even if the battery capacity of the secondary battery to be charged is different in a fast charging mode.

Background technique

Conventionally, secondary batteries such as lithium-ion batteries are usually charged using the CCCV (Constant Current Constant Voltage) charging method shown in FIG. 3 . In the CCCV charging method, as shown in (b) of the figure, after precharging by applying a small charging current Ic and confirming the rise of the voltage between the terminals of the secondary battery (referred to as terminal voltage) Vb, a constant voltage is used. The rapid charging for charging with the charging current Ic of the current Ik1 is performed to maintain the terminal voltage Vb(t) near the maximum charging voltage Ve before the terminal voltage Vb(t) reaches or is about to reach the maximum charging voltage Ve specified in the secondary battery. ) way to gradually reduce the charging current Ic (t) constant voltage charging. Here, the maximum charging voltage Ve is the maximum charging voltage allowed when charging the secondary battery. Charging at a voltage exceeding the maximum charging voltage causes overcharging and the secondary battery may deteriorate or be damaged. The maximum charging voltage Ve of the secondary battery is substantially constant depending on the type of the battery regardless of the battery capacity, and is 4.2 V in the case of a lithium ion battery.

On the other hand, in quick charging, the rising rate (slope) of the terminal voltage Vb(t) rising at a constant charging current Ik1 differs depending on the battery capacity of the secondary battery to be charged. Compared with the battery capacity, if charging If the current Ik1 is small, the charging time for quick charging is prolonged. Conversely, if the current Ik1 is large, charging is performed beyond the natural chemical change rate of the secondary battery, and thus the service life of the secondary battery is shortened. Therefore, using a secondary battery that is fully charged with a nominal capacity value as a constant current discharge, the discharge current value at the end of discharge (SOC (State of Charge) is 0%) is 1C (C is the rated discharge) capacity value), a charging device that sets a constant current Ik1 shown in Figure 3(a) for each 1C specified by the battery capacity of the secondary battery to be charged, and makes the charging current Ic of about 1C a constant current output , so-called 1C charging in fast charging. If rapid charging is performed by 1C charging, it can be charged to full charge in the shortest time without exceeding the natural chemical change rate of the secondary battery.

However, it is necessary to prepare a dedicated charging device for setting Ik1 for each battery capacity of the secondary battery to be charged. In order to solve this problem, it is known that the charging current Ic for constant current control during fast charging is transferred from the secondary battery The side is set to a constant current Ik2 consistent with the battery capacity of the secondary battery, and the charging current Ik2 of the optimum value set for each battery capacity is used for secondary batteries with different battery capacities even in ordinary charging devices. charging method. In this charging method, as shown in FIG. 4, a charging device that outputs a DC voltage Vk that is sufficiently higher than the maximum charging voltage Ve of the secondary battery as a charging voltage Vc and outputs a constant voltage is used, and the equipment side that stores and stores the secondary battery is used. The constant current control circuit performs constant current control so that the charging current Ik2 during quick charging is 1C, which is consistent with the battery capacity of the secondary battery. Therefore, in quick charging, 1C charging is performed on the secondary battery, and when the terminal voltage Vb(t) reaches the maximum charging voltage Ve after about one hour, the charging current Ic(t) is decreased and the terminal voltage Vb is charged at a constant voltage maintained at the maximum charging voltage Ve.

In addition, it is also known to execute a capacity measurement process of detecting the battery capacity of a precharged secondary battery before quick charging, and to perform charging of a constant current charging process during quick charging with a charging current Ic set based on the detected battery capacity. device (Patent Document 1). The battery capacity of the secondary battery is a certain period of time from when the charging circuit that flows the known charging current Io for capacity detection from the charging device to the secondary battery in the capacity measurement process is switched on and off, and the charging current Io flows out The two SOC1 and SOC2 (unit %) detected at the interval of Δt are obtained.

That is, the battery capacity of the secondary battery is given by

Battery capacity = charging current Io · certain time △ t · 100 / (SOC2-SOC1)

calculate. Among them, the SOC (State of Charge), which is the remaining amount of the battery, makes the secondary battery 100% when fully charged, and increases and decreases in proportion to the change in the open voltage between the terminals of the secondary battery. Therefore, SOC1 and SOC2 change from Calculate the open voltage of the secondary battery that controls the opening of the charging circuit before and after the charging time Δt.

prior art literature

Patent Document 1: Japanese Patent Laid-Open No. 2008-61373

In the above-mentioned conventional CCCV charging method shown in FIG. 3 , it is necessary to prepare a dedicated charging device for each battery capacity of the secondary battery. During rapid charging, when compared with the battery capacity, an excessive charging current flows. When Ic, it becomes a cause of deterioration of a secondary battery, and the service life becomes short. Conversely, when constant current charging is performed with a charging current Ic that is too small compared with the battery capacity, the charging time until full charging is prolonged, and rapid charging cannot be performed.

On the other hand, in accordance with the battery capacity of the secondary battery shown in FIG. 4 , the charging current Ic(t) during quick charging is controlled to be constant from the side of the secondary battery that is charged or from the side of the device that houses the secondary battery. In the current Ik2 charging method, even during rapid charging, the terminal voltage Vb(t) of the secondary battery rises, and since the charging voltage Vc output from the charging device cannot be controlled from the secondary battery or the equipment side, the charging voltage from the charging device is constant. The voltage output is a DC voltage Vk sufficiently higher than the maximum charging voltage Ve of the secondary battery. As a result, especially in the initial stage of rapid charging, the potential difference between the DC voltage Vk as the charging voltage Vc and the terminal voltage Vb(t) of the secondary battery is large, and the constant current Ik2 flows, resulting in a large power loss, and the loss Energy is converted to heat, etc., producing an involuntary temperature rise.

In addition, in the charging device described in Patent Document 1, it is necessary to perform capacity measurement processing for detecting the battery capacity of the secondary battery before rapid charging. The open voltage of the battery is troublesome, and its control is also complicated.

In addition, since the charging circuit is controlled to be opened every time the remaining battery capacity (SOC) is detected, the terminal voltage of the secondary battery drops greatly, so charging is not substantially performed in the capacity measurement process, and there is a problem of poor charging efficiency. class questions.

Contents of the invention

The purpose of the present invention is to provide a capacity measurement process for detecting the battery capacity of a secondary battery before quick charging, and to provide an appropriate charging current Ic(t) corresponding to the battery capacity even for secondary batteries with different battery capacities. A charging device for fast charging.

Another object of the present invention is to provide a charging device that performs fast charging without power loss by matching the charging voltage Vc output from the charging device during fast charging to the terminal voltage Vb(t) of the secondary battery.

In order to achieve the above object, the charging device of Scheme 1 is provided with a power supply unit for charging the secondary battery with DC power, and a power supply control unit for controlling the charging operation of the above-mentioned power supply unit until the terminal voltage of the above-mentioned secondary battery reaches a predetermined end voltage. The unit has a voltage detection unit that detects the terminal voltage of the secondary battery, a timer unit that counts the elapsed time, and a calculation unit that sequentially calculates the voltage rise and change rate represented by the terminal voltage increase amount ΔV in a minute unit of elapsed time. During the period when the power supply unit charges the secondary battery with the direct current power, the charging voltage of the direct current power can be made to be the terminal voltage of the secondary battery, and the voltage rise and change rate calculated by the calculation unit is equal to or equal to the predetermined set rise and change rate. way to control the charging current of the above DC power.

The power supply control unit obtains the terminal voltage increase amount △ from the potential difference of the terminal voltage of the secondary battery detected by the voltage detection unit before and after the micro-unit elapsed time measured by the timer unit while the power supply unit is charging the secondary battery with DC power. V, calculates the rate of change of voltage rise in the above minute unit elapsed time. The calculated voltage rise and change rate indicates the charging speed of the secondary battery and is proportional to the charging current. Therefore, by setting the rise and change rate according to the voltage rise and change rate, the charging current is variably controlled regardless of the battery of the secondary battery. Regardless of the capacity, it can be charged at an optimum charging speed suitable for the secondary battery.

The charging device of Solution 2 is characterized in that the end voltage is the maximum charging voltage allowed by the secondary battery, and the power supply control unit controls the charging operation of the power supply unit in the fast charging mode until the terminal voltage of the secondary battery reaches a value higher than the maximum charging voltage. For a slightly lower target voltage, set the above-mentioned rising change rate in the fast charging mode to be close to the voltage rising change rate of the following occasion: discharge the secondary battery with the nominal capacity value at a constant current, and make it become The current value at the end of the discharge is 1C, and the charging is performed with a charging current of 1C.

Until the terminal voltage of the secondary battery reaches the target voltage which is slightly lower than the maximum charging voltage, the terminal voltage of the secondary battery increases at a rate of change in voltage increase when charging with a charging current of approximately 1C. In the fast charging mode, the secondary battery is charged at a charging rate approximately equal to a natural discharge rate regardless of its battery capacity.

The charging device according to the third solution is characterized in that the target voltage is the inflection point voltage at which the rate of voltage increase and change proportional to the charging current starts to decrease.

When the terminal voltage of the secondary battery exceeds the inflection point voltage, even if the same charging current is applied, the rate of increase of the terminal voltage drops sharply, and the rate of conversion of electric energy supplied to the secondary battery to heat increases, deteriorating charging efficiency. Therefore, the rapid charging mode in which the terminal voltage is increased at a rate of change in voltage increase when charging with a charging current of approximately 1C is terminated at the timing of reaching the inflection point voltage just before the charging efficiency deteriorates.

The charging device of Solution 4 is characterized in that, after the terminal voltage of the secondary battery reaches the above-mentioned target voltage, the power supply control part controls the charging operation of the above-mentioned power supply part to the maximum charging voltage in the fine-tuning charging mode, and the above-mentioned setting in the fine-tuning charging mode The rate of change of rise is set to a value sufficiently lower than the rate of change of rise set in the quick charge mode.

After the terminal voltage of the secondary battery reaches the above-mentioned target voltage, until the maximum charging voltage, the voltage rise and change rate of the terminal voltage of the secondary battery decreases rapidly compared with the fast charging mode, so the terminal voltage gradually approaches the maximum charging voltage, and will not be the terminal voltage Overcharging exceeding the maximum charging voltage.

If the target voltage is an inflection point voltage, the charging current decreases after reaching the inflection point voltage, so that the terminal voltage reaches the maximum charging voltage while heat generation is suppressed.

The charging device of claim 5 is the charging device described in any one of claims 1 to 4, characterized in that the power supply unit is connected in series by switching of a switching element between at least a DC input voltage of a DC voltage higher than the end voltage, In the open-circuit step-down converter that outputs the DC power between the charging terminals of the secondary battery, the power supply control unit increases or decreases the switching voltage of the switch so that the rate of voltage rise and change calculated by the calculation unit coincides with the set rate of rise and change. The on-off energy rate of the pulse width modulation signal for on-off control of the element is adjusted to adjust the above-mentioned voltage rise and change rate.

The magnitude of the DC power output from the off-type step-down converter depends on the on-duty rate of the pulse width modulation signal that controls the switching element to be turned off. Therefore, the DC power to charge the secondary battery increases or decreases according to the increase or decrease in the on-duty rate. reduce. The output voltage of the open circuit step-down converter is the terminal voltage of the secondary battery, so the increase and decrease of the DC power appear as the increase and decrease of the charging current, and the rate of change of the voltage rise proportional to the charging current also increases and decreases. Therefore, by adjusting the on-duty rate of the pulse width modulation signal, the voltage rise and change rate calculated by the calculation unit can be made to coincide with the set rise and change rate.

The effects of the present invention are as follows.

According to the invention of claim 1, by not performing the capacity measurement process of detecting the battery capacity of the secondary battery before quick charging, even if it is a secondary battery with a different battery capacity, the rate of increase and change can be set arbitrarily, which can be compared with The secondary battery is charged at an optimum charging speed corresponding to the battery capacity. Therefore, it is not necessary to prepare a dedicated charging device for each secondary battery to be charged, and it can be used as a common charging device for charging multiple types of secondary batteries.

In addition, since the secondary battery is charged with the charging voltage equal to the terminal voltage of the secondary battery, the power loss due to the voltage difference between the two is small, and charging can be performed without unnecessary heat generation.

According to the invention of Claim 2, irrespective of the battery capacity of the secondary battery to be charged, it is possible to charge at the fastest charging speed that does not degrade the secondary battery.

According to the invention of claim 3, since the fast charging mode with a high voltage rise and change rate is terminated at the timing when the inflection point is reached, it is possible to prevent a decrease in charging efficiency.

According to the invention of Claim 4, the secondary battery does not deteriorate due to overcharging.

Also, if the target voltage is the knee point voltage, in the trim charging mode exceeding the knee point voltage, since the charging voltage is sufficiently lowered, heat generation can be suppressed, and the charging efficiency can be charged to the maximum charging voltage without greatly reducing the charging efficiency.

According to the invention of Solution 5, it is possible to make the voltage rise and change rate coincide with the set rise and change rate only by adjusting the turn-on energy rate of the pulse width modulation signal that controls the switching element on and off while the charging voltage is in the state of the terminal voltage. .

Description of drawings

FIG. 1 is a circuit diagram of a charging device 1 according to an embodiment of the present invention that charges a secondary battery 10 .

2( a ) is a graph showing the relationship between the charging voltage Vc output from the charging device 1 and the charging current Ic during charging the secondary battery 10 by the charging device 1 , and (b) is a graph showing the relationship between the charging device 1 and the charging current Ic. A graph of the terminal voltage waveform Vb(t) and the charging current waveform Ic(t) while the secondary battery 10 is being charged.

Figure 3 (a) is a graph showing the relationship between the charging voltage Vc output from the charging device and the charging current Ic during the charging of the secondary battery using the existing CCCV charging method, and (b) shows the relationship between the charging current Ic and the charging current Ic using the existing CCCV charging method. Graphs of the terminal voltage waveform Vb(t) and the charging current waveform Ic(t) during the charging of the secondary battery by the CCCV charging method.

Figure 4(a) is a graph showing the relationship between the charging voltage Vc output from the charging device and the charging current Ic during the charging of the secondary battery by other existing charging methods, and (b) is a graph showing the relationship between the charging current Ic and Graphs of the terminal voltage waveform Vb(t) and the charging current waveform Ic(t) during the charging of the secondary battery by other charging methods.

In the figure: 1-charging device, 2-power supply unit, 3-power supply control unit, 4-switching element (switching element), 9-microprocessor (computing unit), 10-secondary battery, 12-terminal voltage detection circuit , 15 - timing circuit (timing unit).

detailed description

Next, a charging device 1 according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2 . As shown in FIG. 1 , the charging device 1 includes a power supply unit 2 for charging a secondary battery 10 with direct current power, and a power supply control unit 3 for controlling the output of the power supply unit 2 .

The power supply unit 2 steps down the input voltage Vin of the DC power supply 20 smoothed by the smoothing capacitor 11 connected between the pair of inputs 2a and 2b, and outputs it to an open-circuit step-down converter between the pair of outputs 2c and 2d. The structure includes a switching element 4 connected between the low-voltage side input 2b and the low-voltage side output 2d, an inductor 6 connected between the high-voltage side input 2a and the high-voltage side output 2c, a capacitor 7 connected between the pair of outputs 2c and 2d, A switching element for preventing backflow connected between the high-voltage side input 2a and the low-voltage side output 2d.

The switch element 4 is a three-terminal electric field effect transistor that makes the drain and the signal source output 2d and input 2b at the low voltage side respectively, and connects the port to the drive circuit 17 described later in the power supply control section 3. The forward switch control signal output by 17 controls the switch between the drain and the signal source.

The switching element for backflow prevention is also a three-terminal electric field effect transistor with the drain input 2a on the high voltage side, the signal source output 2d on the low voltage side, and the port connected to the drive circuit 17 of the power control part 3. During the turn-off control of the switching element 4 by the flyback control signal output by 17, the disconnection control is performed between the drain and the signal source by preventing the current flowing from the high-voltage side input 2a to the low-voltage side input 2b. While the element 4 is being turned on, conduction between the drain and the signal source is controlled so that a discharge current from the low-side output 2d side to the high-side output 2c flows due to the flyback operation of the inductor 6 . Therefore, instead of the switching element for backflow prevention, a diode may be used in the forward direction from the low-voltage side input 2b to the high-voltage side input 2a.

The high-voltage side output 2c and the low-voltage side output 2d are directly connected to a pair of terminals 10a, 10b of the secondary battery 10 through a high-voltage side charging line 8a and a low-voltage side charging line 8b, respectively. Thus, the output voltage between the pair of outputs 2c and 2d of the power supply unit (open-circuit step-down converter) 2 matches the terminal voltage Vb between the pair of terminals 10a and 10b of the secondary battery 10 charged by the power supply unit 2 . .

The secondary battery 10 charged by the DC power of the power supply unit 2 is a lithium-ion battery with a maximum charging voltage of 4.2V and a nominal voltage of 3.7V. Lithium-ion batteries cannot withstand overvoltages exceeding the maximum charging voltage. The end voltage of the charging stop is set as the maximum charging voltage 4.2V, and the voltage control unit 3 performs charging control to stop charging when the output voltage between the pair of outputs 2c and 2d, that is, the terminal voltage Vb reaches 4.2V. As described above, since the open-circuit step-down converter for stepping down the input voltage Vin is used in the voltage unit 2 , the input voltage Vin of the DC power supply 20 is at least higher than the maximum value of 4.2V of the terminal voltage Vb.

As shown in FIG. 1 , the power supply control unit 3 includes a microprocessor 9, a terminal voltage detection circuit 12 that detects the terminal voltage Vb between the output 2c and 2d at a cycle of several msec, and outputs it to the microprocessor 9. In addition to the microprocessor 9 Outside the execution program of the secondary battery 10 to be charged, the ROM 13 that stores the end voltage or the target voltage described later, setting the rate of change, etc. specified in each secondary battery 10 to be charged is based on the distribution between the low-voltage side charging lines 8b. The voltage drop of the resistor 18 always monitors the charging current Ic flowing in the low-voltage side charging line 8b and outputs the charging current detection circuit 14 to the microprocessor 9, the timing circuit 15 that outputs the timing information to the microprocessor 9, and detects the DC voltage. The input voltage Vin of the power supply 20 is output to the microprocessor 9 by the input voltage detection circuit 16 and the drive circuit 17 which controls the operation of the switching element 4 and the switching element for backflow prevention. The microprocessor 9 is also connected to a temperature sensor 19 disposed near the secondary battery 10 , and temperature information of the secondary battery 10 is input from the temperature sensor 19 .

In the high-speed charging mode described later, the forward switching control signal for switching the switching element 4 (the port of the FET) by the drive circuit 17 is a rectangular wave signal that repeats the H level and the L level in a period of 1 μsec. , when the rectangular wave signal is at the H level, the low-voltage side output 2d is connected to the low-voltage side input 2b. In addition, the flyback control signal for opening and closing the backflow prevention switching element 5 (FET port) by the drive circuit 17 inverts the polarity of the above-mentioned forward switching control signal and outputs it to the forward switching control signal synchronously. The signal of the signal outputs an L-level rectangular wave signal to the backflow prevention switching element 5 while the switching element 4 is being turned off, and blocks the high-voltage side input 2a and the low-voltage side output 2d. Therefore, during the ON period when the switching element 4 is turned off, the voltage difference between the input voltage Vin of the DC power supply 20 and the terminal voltage Vb is applied to the inductor 6 to charge the inductor 6 and convert electric energy into magnetic energy.

On the other hand, during the off-period during which an L-level rectangular wave signal is output to the switching element 4 to open the switching element 4, an H-level rectangular wave signal is output to the backflow prevention switching element 5, so that the high-voltage side input 2a conducts with the low-voltage side output 2d, so the magnetic energy accumulated in the inductor 6 during the ON period becomes electric energy, that is, the charging current Ic, which charges the secondary battery 10 and the capacitor 7 connected in parallel to both ends of the inductor 6 .

Here, in one cycle (1 μsec) which is the sum of the ON period and the OFF period, the electric energy generated at the outputs 2c and 2d of the power supply unit 2 is proportional to the ratio of the ON period in one cycle, that is, the ON energy rate. Proportion. The electric energy generated on the outputs 2c, 2d charges the secondary battery 10 as DC power, but the outputs 2c, 2d are connected to the pair of terminals 10a, 10b of the secondary battery 10, so the output voltage between the outputs 2c, 2d is the same as The terminal voltage Vb between the terminals 10 a and 10 b is equal, and the DC power that increases or decreases in proportion to the conduction rate is expressed as an increase or decrease in the charging current Ic for charging the secondary battery 10 .

Therefore, in this embodiment, the forward switching control signal which is a rectangular wave signal is a PWM (Pulse Width Modulation) signal modulated with predetermined control data output from the microprocessor 9. In other words, by using the control data output from the microprocessor 9 to the drive circuit 17, the turn-on rate of the forward switch control signal is changed, thereby controlling the increase and decrease of the charging current Ic.

Next, the charging of the secondary battery 10 as a lithium ion battery to the end voltage Ve will be described centering on the operation of the microprocessor 9 in each mode of pre-charging, quick charging, and fine-tuning charging shown in FIG. 2( b ). The charging process of device 1.

(precharge mode A)

In the pre-charge mode, before charging the secondary battery 10, it is determined whether there is an abnormality in the secondary battery 10 or the charging circuit, and if an abnormality is confirmed, the charging is stopped without shifting to the rapid charging mode.

When the microprocessor 9 starts the _t0 of the precharge mode, the terminal voltage Vb, the charging current Ic, and the input voltage Vin detected by the terminal voltage detection circuit 12, the charging current detection circuit 14, the input voltage detection circuit 16, and the temperature sensor 19 are stored respectively. , the temperature Tb of the secondary battery 10, and at the same time, output control data to the drive circuit 17 to make the power supply unit 2 operate, wherein the output data output a forward switch control signal and a flyback control signal. Wherein, the control data output to the drive circuit 17 utilizes pulse width modulation to make the ON period of the forward switch control signal short, so, as shown in FIG. ) to charge the secondary battery 10 .

After that, the microprocessor 9 detects the terminal voltage Vb, the charging current I, the input voltage Vin, and the temperature Tb of the secondary battery 10 at _t1 after the predetermined time counted by the timer circuit 15 from the terminal voltage detection circuit 12 and the charging current detection circuit 12, respectively. The circuit 14, the input voltage detection circuit 16, and the temperature sensor 19 input, and when compared with the value at t ₀ , any one of the detected values has an abnormal value, for example, if the terminal voltage Vb(t) does not rise, the charging current Ic(t) If the value is not within the range predicted by the control data, if the input voltage Vin is below the end voltage, if the temperature Tb of the secondary battery rises abnormally, etc., the charging is stopped. When the charge is suspended, the forward switching control signal output from the microprocessor 9 is always at L level, and the switching element 4 is controlled to be turned on.

(Quick charging mode B→B′→C)

If there is no abnormality in the detection value at _t1 , the mode shifts to the quick charging mode. In the fast charging mode, the secondary battery 10 is charged at a charging rate substantially equal to the rated discharge rate of the secondary battery 10 until the terminal voltage Vb(t) reaches the target voltage Ve' which is slightly lower than the maximum charging voltage Ve. t ₂ hours. Here, the so-called charging rate approximately equal to the rated discharge rate of the secondary battery 10 is a rate at which the terminal voltage Vb(t) and the nominal capacity value of the fully charged secondary battery 10 are discharged at a constant current, so that the secondary battery 10 is discharged at a constant current. The current value at the end of hourly discharge is 1C, and the voltage rise rate (the voltage difference between the terminal voltage Vb(t) per unit time) when the secondary battery 10 is charged with a charging current of 1C (referred to as 1C charging) ) are approximately equal. In addition, in the present embodiment, the target voltage Ve' at which the fast charging mode is terminated is set as the inflection point voltage at which the rate of change of voltage increase proportional to the charging current Ic(t) starts to decrease, and is slightly lower than the maximum charging voltage Ve of 4.2V. 4.0V.

In the ROM 13, as the charging information of the secondary battery 10, which is a lithium ion battery, the secondary battery to be charged is stored according to the voltage rise and change rate (different for each battery type of the secondary battery 10) when 1C charging is performed. The first set rate of change of the secondary battery 10 (here, the rate of change in the case of a lithium-ion battery), and the second set rate of change set to a value sufficiently lower than the first set rate of change , a target voltage Ve′ (4.0V), and a maximum charging voltage Ve (4.2V) as an end voltage.

After the microprocessor 9 starts the fast charging mode _t1 , the control data that makes the turn-on energy of the forward switch control signal a predetermined value is output to the drive circuit 17, and the forward switch control signal and the polarity are output from the drive circuit 17. The flyback control signal with reversed nature makes the power supply unit 2 operate. After that, the terminal voltage increase ΔV is obtained from the voltage difference between the terminal voltage Vb(t) detected by the terminal voltage detection circuit 12 at about (B, B') of the minute time Δt of several msec, and is calculated as each minute time The terminal voltage increment of Δt is the voltage rise change rate of ΔV.

Next, the calculated voltage rise and change rate is compared with the first set rise and change rate read from the ROM 13, and the forward switching is performed so that the calculated voltage rise and change rate coincide with the first set rise and change rate. Control data for changing the on-duty rate of the control signal is output to the drive circuit 17 . That is, when the calculated voltage rise change rate is equal to or less than the first set rise change rate, the control data for increasing the turn-on rate of the forward switch control signal is output to the drive circuit 17, so that the charging current Ic(t) On the contrary, when the calculated voltage rise change rate is above the first set rise change rate, the control data for reducing the turn-on energy rate of the forward switch control signal is output to the drive circuit 17 to reduce the charging current Ic( t). The voltage rise rate of the terminal voltage Vb(t) increases and decreases according to the charging current Ic(t). Therefore, by repeating the above-mentioned processing in a cycle of, for example, several msec in the fast charging mode, regardless of the size of the battery capacity, the The secondary battery 10 can be charged at a charge rate approximately equal to the rated discharge rate. In addition, the length of the minute time Δt, that is, the period in which the above-mentioned processing is repeated, is set to several msec in this embodiment, but it is not necessarily such a length, and it can be implemented even with a length of several seconds to several tens of seconds. this invention.

The charging current Ic(t) in this fast charging mode preferably fluctuates around the charging current value 1C determined by the type of the secondary battery 10 to be charged and its capacitance capacity, but it does not use a predetermined charging method like a conventional charging device. The current value 1C performs constant current control on the known secondary battery 10, so even if the charging conditions such as the change in the internal resistance of the secondary battery 10 over the years or the change in the resistance value of the charging line change, the charging current Ic also automatically changes. setting, it can maintain the optimum charging speed according to its own charging conditions.

In addition, the microprocessor 9 compares the terminal voltage Vb(t) detected by the terminal voltage detection circuit 12 with the target voltage Ve′ (4.0) read from the ROM 13 while repeating the above processing in a cycle of several msec. , when the target voltage Ve′ (4.0V) is reached, transfer from the fast charging mode to the fine-tuning charging mode.

(fine-tuning charging mode D)

In the fine-tuning charging mode, since the terminal voltage Vb(t) exceeds the inflection point voltage at which the charging efficiency of the secondary battery 10 drops sharply, the charging current Ic(t) of the secondary battery 10 is decreased to reduce the charging speed and prevent excess charging. The charging current Ic(t) is converted into thermal energy to degrade the charging efficiency, and prevents the terminal voltage Vb from being overcharged to exceed the maximum charging voltage, resulting in deterioration or damage to the secondary battery 10 .

The microprocessor 9 follows the fast charging mode, detects the terminal voltage Vb(t) before and after the tiny time Δt of a few msec, calculates the terminal voltage increment ΔV per tiny time Δt, that is, the voltage rise rate, and sends it to the driving circuit 17 outputs control data for changing the turn-on rate of the forward switch control signal so that the calculated voltage rise change rate matches the second set rise change rate read from the ROM 13 .

The second set rate of increase and change is sufficiently lower than the first set rate of change of increase and is a value close to 0. Therefore, as shown in FIG. The charging current Ic of the fast charging mode drops sharply from the charging current Ic(t) of the fast charging mode, and the terminal voltage Vb(t) rises with an extremely slow slope.

While the microprocessor 9 repeats the above processing in a cycle of several msec, the terminal voltage Vb(t) detected by the terminal voltage detection circuit 12 and the maximum charging voltage Ve (4.2 V) which is the end voltage read from the ROM 13 are compared. In contrast, when _t3 of the end voltage (4,2V) is reached, the forward switching control signal output from the slave processor 9 is always at L level, and the switching element 4 is turned on to stop charging.

In the charging process of the secondary charging 10 described above, after the terminal voltage Vb(t) reaches _t3 when the end voltage (4.2v), the microprocessor 9 outputs the control data to make the voltage rise and change rate 0 to the control The circuit 17 flows a small charging current Ic(t) to maintain the terminal voltage Vb at the end voltage (4.2V).

In addition, even in the quick charging mode or the trimming charging mode, when the temperature of the secondary battery 10 detected by the temperature sensor 19 rises abnormally, or when the input voltage Vin is lower than the end voltage (4.2V), the switching element 4 is controlled to be turned on. Stop charging.

The present invention is not limited to the above embodiments, and can be modified in various ways. For example, the first setting rate of change for making the rate of rise and change of voltage consistent in the fast charging mode is not necessarily set to charge with a charging current of 1C. The rate of change in voltage rise can be set in accordance with any charging speed such as 2C charging or 1/2C charging.

In addition, the set rise change rate for matching the voltage rise change rate is not necessarily the same in the fast charging mode, and any one of a plurality of set rise change rates set to different change rates may be made to match the change of the charging state. The rate of change of voltage rise is consistent. For example, as the temperature of the secondary battery 10 detected by the temperature sensor 19 rises, the set rise change rate is changed to a set rise change rate that makes the voltage rise change rate equal to a lower value.

In addition, the terminal voltage detected around the elapsed time of the minute unit can be specified by performing calculation processing such as removing abnormal values or averaging based on the correlation of a plurality of continuously detected terminal voltages.

In addition, the power supply unit 2 is not limited to an open-circuit step-down converter, and any type of converter can be used as long as the output current (charging current) for charging the secondary battery can be variably controlled in a state in which the output voltage is linked to the terminal voltage. DC power supply.

In addition, the secondary battery is not limited to a lithium-ion battery as long as it has a characteristic that the charging speed changes according to the charging current, and may be other secondary batteries such as nickel-cadmium batteries.

Industrial applicability is as follows.

The present invention is suitable for a charging device using a reverse plate spring as a movable contact plate.

Claims (6)

1. A charging device comprising: a power supply unit for charging a secondary battery with DC power; and a power supply control unit that controls the charging operation of the power supply unit until the terminal voltage of the secondary battery reaches a predetermined end voltage, The charging device is characterized in that, The power control section has: a voltage detection unit that detects a terminal voltage of the secondary battery; A timing unit for counting elapsed time; A calculation unit that sequentially calculates the voltage rise and change rate expressed by the terminal voltage increase △V within a small unit elapsed time, While the power supply unit is charging the secondary battery with DC power, the charging voltage of the above-mentioned DC power is controlled to the terminal voltage of the secondary battery, and the charging current of the above-mentioned DC power is variably controlled so that the calculation unit calculates The voltage rise and change rates are a plurality of predetermined set rise and change rates different from each other. 2. The charging device according to claim 1, characterized in that, The end voltage is the maximum charging voltage allowed by the secondary battery, The power supply control unit controls the charging operation of the power supply unit in the fast charging mode until the terminal voltage of the secondary battery reaches a target voltage slightly lower than the maximum charging voltage, Set the above-mentioned rising change rate in the fast charging mode to be close to the voltage rising change rate when charging with a charging current of 1C, wherein the 1C is fully charged with a nominal capacity value at a constant current The secondary battery is discharged, and the current value that makes the discharge end in 1 hour. 3. The charging device according to claim 2, characterized in that, The target voltage is the inflection point voltage at which the rate of change of voltage increase proportional to the charging current starts to decrease. 4. The charging device according to claim 2, characterized in that, After the terminal voltage of the secondary battery reaches the target voltage, the power control unit controls the charging operation of the power supply unit in a fine-tuning charging mode until the terminal voltage of the secondary battery reaches the maximum charging voltage, The set increase change rate in the fine charge mode is set to a value sufficiently lower than the set increase change rate in the quick charge mode. 5. The charging device according to claim 3, characterized in that, After the terminal voltage of the secondary battery reaches the target voltage, the power control unit controls the charging operation of the power supply unit in a fine-tuning charging mode until the terminal voltage of the secondary battery reaches the maximum charging voltage, The set increase change rate in the fine charge mode is set to a value sufficiently lower than the set increase change rate in the quick charge mode. 6. The charging device according to any one of claims 1 to 5, characterized in that: The power supply unit is an open-circuit step-down converter that outputs the above-mentioned DC power between the charging terminals of the secondary battery by opening and closing a switching element connected in series between a DC input of at least a DC voltage higher than the end voltage, and the power supply The control unit adjusts the above-mentioned voltage rise and change rate by increasing or decreasing the turn-on rate of the pulse width modulation signal in such a manner that the voltage rise and change rate calculated by the calculation unit coincides with the above-mentioned set rise and change rate, wherein the pulse width modulation signal Opening and closing control is performed on the above-mentioned switching element.