Charging device and charging method

Abstract

This invention provides a secondary battery charging device that can efficiently charge batteries by controlling the current value in conjunction with the voltage value. [Solution] The charging device 100 includes a transformer 2 connected to a power source 1 that converts a DC voltage to a predetermined DC voltage, a current control unit 3 connected to the transformer 2 that controls the output current, and a signal control unit 4 that outputs a voltage control signal to the transformer 2 and a current control signal to the current control unit 3. The current supplied to the secondary battery 5 includes a first period set to a first current value and a second period set to a second current value. In the first period, the first current value is set to a first voltage value which is greater than or equal to the voltage value required to flow into the secondary battery 5, and in the second period, the second current value is set to a second voltage value which is greater than or equal to the voltage value required to flow into the secondary battery 5.

Description

Technical Field

[0001] The present disclosure relates to a charging device that controls the power supplied to a secondary battery and a charging method for the charging device.

Background Art

[0002] In a charging device for a secondary battery using a solar cell as a power source, a device equipped with a DC-DC converter that performs boosting or bucking is used so that charging can be performed at a stable voltage. By the way, DC-DC converters are used not only in charging devices but also in drive circuits such as LED devices used for lighting and the like. In such an LED drive circuit, the voltage fluctuates due to temperature changes, and the power consumption may increase. Therefore, a method for suppressing the power consumption generated in a constant current drive circuit has been proposed (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003] [[ID=...]]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A conventional LED drive circuit includes a DC power supply that outputs a DC LED drive voltage, a constant current drive circuit connected in series with the LED to the DC power supply, and a headroom voltage monitoring circuit that dynamically variably controls the voltage level of the LED drive voltage by acting on the DC power supply so that the headroom voltage obtained at the current terminal of the constant current drive circuit is maintained near the reference voltage.

[0005] Incidentally, in charging devices, charging efficiency can be improved by controlling the current to a binary value according to the characteristics of the secondary battery. When charging a secondary battery with a desired current value, the potential difference between the terminals of the secondary battery changes in proportion to the current value. When voltage control is performed with a DC-DC converter, the output voltage is kept constant, so normally, a binary voltage is not output. Therefore, when controlling a binary current, the voltage value is set to a high value to control the current, and even at low current values, the voltage value is high, which leads to the problem of wasted power consumption.

[0006] This disclosure is made to solve the above-mentioned problems and aims to provide a charging device for a secondary battery that can be charged efficiently by controlling the current value in conjunction with the voltage value, and a charging method for the charging device. [Means for solving the problem]

[0007] The charging device according to this disclosure is a charging device for controlling power supplied to a secondary battery, comprising: a transformer connected to a power source and converting a DC voltage to a predetermined DC voltage; a current control unit connected to the transformer and controlling the output current; and a signal control unit that outputs a voltage control signal to the transformer and a current control signal to the current control unit, wherein the current supplied to the secondary battery includes a first period set to a first current value and a second period set to a second current value, wherein in the first period, the transformer is configured to convert the first current value to a first voltage value which is equal to or greater than the voltage value required to flow through the secondary battery, and in the second period, the transformer is configured to convert the second current value to a second voltage value which is equal to or greater than the voltage value required to flow through the secondary battery.

[0008] The charging device according to this disclosure is a charging device that controls the power supplied to a secondary battery, wherein the current supplied to the secondary battery includes a first period set to a first current value and a second period set to a second current value, wherein in the first period, the first current value is set to a first voltage value which is equal to or greater than the voltage value required to flow through the secondary battery, and in the second period, the second current value is set to a second voltage value which is equal to or greater than the voltage value required to flow through the secondary battery, wherein the first current value is equal to or greater than the minimum value at which the secondary battery can be charged, the second current value is higher than the first current value, the second voltage value is set to a value within a range corresponding to the second current value, and the first voltage value is set to a value within a range corresponding to the first current value and is lower than the second voltage value.

[0009] The charging method according to this disclosure is a charging method for a charging device that controls power supplied to a secondary battery, wherein the charging device comprises: a transformer connected to a power source and converting a DC voltage to a predetermined DC voltage; a current control unit connected to the transformer and controlling the output current; and a signal control unit that outputs a voltage control signal to the transformer and a current control signal to the current control unit, wherein the current supplied to the secondary battery includes a first period set to a first current value and a second period set to a second current value, wherein in the first period, the transformer is configured to convert the first current value to a first voltage value which is equal to or greater than the voltage value required to flow through the secondary battery, and in the second period, the transformer is configured to convert the second current value to a second voltage value which is equal to or greater than the voltage value required to flow through the secondary battery. [Effects of the Invention]

[0010] According to this disclosure, when charging a secondary battery, efficient charging can be achieved by changing the current value to two different values. In this process, power consumption can be reduced by also changing the voltage value according to the current value. [Brief explanation of the drawing]

[0011] [Figure 1]This is a schematic diagram showing a charging device according to the first embodiment of this disclosure. [Figure 2] This is a circuit diagram showing the schematic of the transformer section. [Figure 3] This is a characteristic diagram showing the power supplied from the charging device to the secondary battery. [Figure 4] This is a schematic diagram showing a charging device according to a second embodiment of the present disclosure. [Figure 5] This is a characteristic diagram showing the power supplied from the charging device to the secondary battery in the second embodiment. [Figure 6] This is a schematic diagram showing a charging device according to a third embodiment of this disclosure. [Modes for carrying out the invention]

[0012] (First Embodiment) Hereinafter, a charging device according to the first embodiment of this disclosure will be described with reference to the drawings.

[0013] Figure 1 is a schematic diagram showing a charging device according to the first embodiment of this disclosure, and Figure 2 is a schematic circuit diagram showing a transformer section.

[0014] The charging device 100 controls the power supplied from the power source 1 and supplies it to the secondary battery 5. The charging device 100 includes a voltage transformer 2, a current control unit 3, and a signal control unit 4. In this embodiment, the power source 1 is a solar cell that generates solar power, and the secondary battery 5 is a flow-type metal-air battery.

[0015] The transformer unit 2 is connected to the power supply 1 and converts the DC voltage to a predetermined DC voltage. The transformer unit 2 includes a converter 2a, which is a voltage converter (DC-DC converter), and an adjustment circuit 2b that receives the output of the converter 2a and performs feedback control.

[0016] The current control unit 3 is connected to the transformer unit 2 and controls the current output to the secondary battery 5. That is, in the charging device 100, the transformer unit 2 and the current control unit 3 are sequentially connected between the power source 1 and the secondary battery 5. The signal control unit 4 outputs a voltage control signal to the transformer unit 2 and a current control signal to the current control unit 3. The current control unit 3 receives the current control signal and controls the output current value so that it is not less than the minimum value at which the secondary battery 5 can be charged.

[0017] Basically, the power to the secondary battery 5 is controlled by the current required for charging, and the voltage at that time is determined by the performance (characteristics) of the secondary battery 5. Therefore, the transformer unit 2 receives the voltage control signal and converts the voltage so that it is not less than the voltage value required for flowing through the secondary battery 5. Note that the power supplied from the charging device 100 to the secondary battery 5 will be described with reference to FIG. 3 described later.

[0018] Regarding the adjustment circuit 2b, for example, as shown in FIG. 2, it is configured by combining a plurality of resistors and switching elements. In the adjustment circuit 2b, by switching the on / off of the switching element according to the signal from the signal control unit 4, some resistors can be connected or disconnected, and the voltage at the FB (feedback) terminal of the converter 2a can be changed. Note that the adjustment circuit 2b is not limited to this, and it may be configured by combining various elements so as to change the voltage output from the transformer unit 2.

[0019] FIG. 3 is a characteristic diagram showing the power supplied from the charging device to the secondary battery.

[0020] In FIG. 3, a graph showing the output voltage Vout of the charging device 100 is shown at the top, and a graph showing the output current Is of the charging device 100 is shown at the bottom. The charging device 100 controls so that two current values alternate, and controls so that an appropriate voltage value is obtained according to the current value. Specifically, regarding the output current Is, in the first period Ta, it is set to the first current value Ia which is a low value, and in the subsequent second period Tb, it is set to the second current value Ib which is higher than the first current value Ia. The output voltage Vout is synchronized with the output current Is. In the first period Ta, it is set to the first voltage value Va which is a low value, and in the subsequent second period Tb, it is set to the second voltage value Vb which is a high value. It is preferable that the second current value Ib is set to 2 to 4 times the first current value Ia, and it is preferable that the second voltage value Vb is set to 2 to 3 times the first voltage value Va.

[0021] In the present embodiment, the second period Tb is set shorter than the first period Ta. That is, the charging device 100 controls to maintain a low current value in the long first period Ta, and controls to temporarily increase the current value in the short second period Tb. Note that the lengths of the first period Ta and the second period Tb may be adjusted as appropriate, and the second period Tb may be set longer than the first period Ta.

[0022] As described above, when charging the secondary battery 5, by changing to two different current values, efficient charging can be achieved. At this time, by also changing the voltage value according to the current value, power consumption can be suppressed. And by applying two or more current values within a certain period, efficient charging can be achieved for the flow-type metal-air battery. Also, when the current value is low, by suppressing the voltage value low, wasteful power consumption can be avoided. Furthermore, by increasing the voltage value according to the current value, appropriate power can be output. By providing a clear difference between the two voltage values and current values and controlling them to appropriate values, the charging efficiency of the secondary battery 5 can be further improved.

[0023] (Second Embodiment) Next, a charging device according to the second embodiment of this disclosure will be described with reference to the drawings. In the second embodiment, the configuration which is substantially the same as that of the first embodiment shown in Figures 1 to 3 will not be described, and only the differences will be described.

[0024] Figure 4 is a schematic diagram showing a charging device according to a second embodiment of this disclosure.

[0025] The second embodiment differs from the first embodiment in that a power storage unit 7 is added. The power storage unit 7 is connected to the power supply 1 in parallel with the transformer unit 2 and stores the power supplied from the power supply 1. Specifically, in this embodiment, the path from the power supply 1 to the current control unit 3 is connected in parallel to the path passing through the transformer unit 2 and the path passing through the power storage unit 7. The power storage unit 7 is, for example, a large-capacity capacitor or an electric double-layer capacitor.

[0026] In the path passing through the transformer unit 2, the first diode D1, the transformer unit 2, and the first switch SW1 are connected in that order. The first diode D1 prevents current from flowing back from the transformer unit 2 to the power supply 1. The first switch SW1 is switched on and off in response to instructions from the signal control unit 4.

[0027] In the path passing through the energy storage unit 7, the second diode D2, the auxiliary current control unit 6, the energy storage unit 7, and the second switch SW2 are connected in that order. The second diode D2 prevents current from flowing back from the auxiliary current control unit 6 to the power supply 1. The auxiliary current control unit 6 receives a signal from the signal control unit 4 and controls the current value input to the energy storage unit 7. The second switch SW2 is switched on and off in response to instructions from the signal control unit 4.

[0028] The charging device 100 is equipped with an input power measuring unit that measures the voltage and current values ​​from the power supply 1, and a transformer current measuring unit that measures the current value to the transformer unit 2. Specifically, the input power measuring unit should measure the voltage and current values ​​before the power supply branches into a path through the transformer unit 2 and a path through the energy storage unit 7. The transformer current measuring unit should measure, for example, the current value at the first diode D1.

[0029] The input power measurement unit inputs the measured first voltage measurement value Vpv and first current measurement value Ihpv to the signal control unit 4. The transformer current measurement unit also inputs the measured second current measurement value Idc to the signal control unit 4. The signal control unit 4 then controls the stored current value Ied based on the first current measurement value Ihpv and the first voltage measurement value Vpv so that the power of the power supply 1 (for example, a solar cell) is maximized.

[0030] The control method that maximizes the power of power source 1 described above is shown below. As a premise, according to the law of conservation of current, the stored current value Ied can be expressed as "Ied = Ihpv - Idc". If the maximum current of power source 1 is Ihpvm, and the value of Ied at that time is Iedm, then it can be expressed as "Iedm = Ihpvm - Idc".

[0031] In this control system, first, the auxiliary current control unit 6 gradually reduces the current Ied from Iedm. As Ied decreases, Ihpv and Vpv change, and consequently, the power Wpv (=Ihpv × Vpv) also changes. Next, each time Ied is reduced, Ihpv and Vpv are measured, and the increase or decrease in the value of Wpv is estimated from these measurements. Finally, when the value of Wpv changes from increasing to decreasing, the operation to reduce Ied is stopped, and the value of Ied at that time is set to Iedc. As described above, the auxiliary current control unit 6 is controlled by the signal control unit 4 based on the measured values ​​input to the input power measurement unit, and the aforementioned value of Iedc is input to the battery 7 as the stored current value Ied.

[0032] The transformer unit 2 uses a switching element to increase and decrease the current, and an inductor transforms the voltage based on this increase or decrease in current. Therefore, the current flowing to the transformer unit 2 has periods when the current increases and periods when the current decreases. When a solar cell is used as the power source 1, the current value generated by the solar cell is determined by the amount of sunlight at that time, and a fixed amount of current flows in proportion to the amount of sunlight at that time. Therefore, if the amount of current flowing to the transformer unit 2 increases or decreases, the current corresponding to the change in the voltage due to the transformation is wasted. In contrast, in this embodiment, the current value flowing to the energy storage unit 7 is controlled so that the output power of the power source 1 is maximized, and any surplus power that is not needed for charging at that time is stored in the energy storage unit 7, so that the energy obtained from sunlight can be used efficiently without waste.

[0033] Figure 5 is a characteristic diagram showing the power supplied from the charging device to the secondary battery in the second embodiment.

[0034] In Figure 5, similar to Figure 3, the graph showing the output voltage Vout of the charging device 100 is shown at the top, and the graph showing the output current Is of the charging device 100 is shown at the bottom. In Figure 5, the change in the output voltage Vout during the second period Tb is different from that in Figure 3, and this point will be explained below.

[0035] In this embodiment, the first switch SW1 and the second switch SW2 are switched on and off as appropriate by signals from the signal control unit 4, so that during the first period Ta, power is supplied from the transformer unit 2 to the secondary battery 5, and during the second period Tb, power is supplied from the energy storage unit 7 to the secondary battery 5.

[0036] The energy storage unit 7 tends to experience a voltage drop when current flows through it. Therefore, in the second period Tb, the output voltage Vout is set to a value higher than the second voltage value Vb at the start, and even at the end when the voltage has dropped, the output voltage Vout is set to remain higher than the second voltage value Vb. In this way, different voltage and current values ​​can be easily set by switching the power supply.

[0037] (Third embodiment) Next, a charging device according to the third embodiment of this disclosure will be described with reference to the drawings. In the third embodiment, the configuration which is substantially the same as that of the first and second embodiments shown in Figures 1 to 5 will not be described, and only the differences will be explained.

[0038] Figure 6 is a schematic diagram showing a charging device according to the third embodiment of this disclosure.

[0039] In the third embodiment, the configuration of the path passing through the energy storage unit 7 differs from that of the second embodiment. Specifically, in this embodiment, an auxiliary converter 8 (an example of an energy storage voltage transformer) and a third switch SW3 are added between the second switch SW2 and the current control unit 3 in the path passing through the energy storage unit 7. The auxiliary converter 8 is a boost-type voltage converter that converts the output voltage from the energy storage unit 7 to a predetermined voltage value, and the output voltage is input to the current control unit 3. The third switch SW3 is switched on and off in response to instructions from the signal control unit 4. In this embodiment, since the output voltage from the energy storage unit 7 is kept at a constant voltage by the auxiliary converter 8, the charging efficiency of the secondary battery 5 can be improved.

[0040] For the second switch SW2 and the third switch SW3, the timing at which they are turned on may be staggered, taking into account the rise time of the auxiliary converter 8.

[0041] The embodiments disclosed herein are illustrative in all respects and do not constitute a basis for restrictive interpretation. Therefore, the technical scope of this disclosure is not construed solely by the embodiments described above, but is defined based on the claims. Furthermore, all modifications within the meaning and scope of "equivalent to" the claims are included. In particular, elements, batteries, power supplies, components, etc., exemplified in this disclosure may be replaced with those having similar functions. [Explanation of symbols]

[0042] 1 power supply 2. Transformer section 2a converter 2b Adjustment circuit 3 Current control unit 4. Signal Control Unit 5 Secondary battery 6. Auxiliary current control unit 7. Energy Storage Unit 8. Auxiliary converter (an example of a storage and transforming unit) 100 Charging device

Claims

1. A charging device that controls the power supplied to a secondary battery, A transformer unit connected to a power supply that converts a DC voltage to a predetermined DC voltage, A current control unit connected to the voltage transformer controls the output current, The system comprises a signal control unit that outputs a voltage control signal to the transformer and a current control signal to the current control unit, The current supplied to the secondary battery includes a first period set to a first current value and a second period set to a second current value. During the first period, the transformer is set to convert the first current value to a first voltage value that is equal to or greater than the voltage value required to flow through the secondary battery. During the second period, the transformer is configured to convert the second current value to a second voltage value that is equal to or greater than the voltage value required to flow through the secondary battery. A charging device characterized by the following.

2. A charging device according to claim 1, The first current value is set to be equal to or greater than the minimum value at which the secondary battery can be charged. The second current value is higher than the first current value. The second voltage value is set to a value within the range corresponding to the second current value. The first voltage value is set to a value within the range corresponding to the first current value, and is lower than the second voltage value. A charging device characterized by the following.

3. A charging device according to claim 2, The second current value is 2 to 4 times the first current value. The second voltage value is two to three times the first voltage value. A charging device characterized by the following.

4. A charging device according to claim 1, The system includes a power storage unit connected in parallel with the transformer unit to the power supply unit, which stores power. A charging device characterized by the following.

5. A charging device according to claim 4, An input power measuring unit that measures the voltage and current values ​​from the power supply, The system includes an auxiliary current control unit provided in the wiring that supplies surplus power to the aforementioned power storage unit, The aforementioned power source is a solar cell. The input power measurement unit inputs the measured first voltage measurement value and first current measurement value to the signal control unit. The signal control unit changes the detected current value input to the energy storage unit and controls the auxiliary current control unit so that the power of the solar cell calculated from the first current value and the first voltage measurement value becomes the maximum current value within the range of change of the detected current value. A charging device characterized by the following.

6. A charging device according to claim 5, The system includes a voltage transformer that converts the output voltage from the energy storage unit to a predetermined voltage value, The aforementioned energy storage transformer is a boost-type voltage converter, and the output voltage is input to the current control unit. A charging device characterized by the following.

7. A charging device according to claim 4, The transformer unit supplies power to the secondary battery during the first period. The energy storage unit supplies power to the secondary battery during the second period. A charging device characterized by the following.

8. A charging device according to claim 1, The secondary battery is a flow-type metal-air battery. A charging device characterized by the following.

9. A charging device that controls the power supplied to a secondary battery, The current supplied to the secondary battery includes a first period set to a first current value and a second period set to a second current value. During the first period, the first current value is set to a first voltage value that is equal to or greater than the voltage value required to flow through the secondary battery. During the second period, the second current value is set to a second voltage value that is equal to or greater than the voltage value required to flow through the secondary battery. The first current value is set to be equal to or greater than the minimum value at which the secondary battery can be charged. The second current value is higher than the first current value. The second voltage value is set to a value within the range corresponding to the second current value. The first voltage value is set to a value within the range corresponding to the first current value, and is lower than the second voltage value. A charging device characterized by the following.

10. A charging device according to claim 9, The second current value is at least twice the first current value. A charging device characterized by the following.

11. A charging device according to claim 10, The second current value is 2 to 4 times the first current value. The second voltage value is two to three times the first voltage value. A charging device characterized by the following.

12. A charging method for a charging device that controls the power supplied to a secondary battery, The charging device is A transformer unit connected to a power supply that converts a DC voltage to a predetermined DC voltage, A current control unit connected to the voltage transformer controls the output current, The system comprises a signal control unit that outputs a voltage control signal to the transformer and a current control signal to the current control unit, The current supplied to the secondary battery includes a first period set to a first current value and a second period set to a second current value. During the first period, the transformer is set to convert the first current value to a first voltage value that is equal to or greater than the voltage value required to flow through the secondary battery. During the second period, the transformer is configured to convert the second current value to a second voltage value that is equal to or greater than the voltage value required to flow through the secondary battery. A charging method characterized by the following.

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