Recharging method and recharging device

Abstract

This charging method and charging device calculate the efficiency of the charging device on the basis of the input electric power and the output electric power of the charging device when a battery and a capacitor are connected in parallel and electric power is supplied to the battery from the charging device via the capacitor, and cause the charging device to transition to an intermittent operation mode in which the charging device is intermittently operated at an intermittent frequency when it is determined that the efficiency falls below a predetermined threshold. The intermittent frequency is higher than the frequency of resonance generated between the battery and the capacitor, and in the intermittent operation mode, the gain of the ripple electric current flowing in the battery with respect to the ripple electric current output from the charging device is 0 dB or less.

Description

Charging method and charging device

[0001] The present disclosure relates to a charging method and a charging device.

[0002] A technology has been disclosed for an on-board charger that provides stable operation by suppressing the adverse effects of the resonant frequency of the AC power supply filter and maximizing the phase margin and gain margin (see Patent Document 1). This technology provides multiple band-elimination filters that suppress amplification at the resonant frequency determined by the on-board charger and the AC power supply, and switches to the optimal band-elimination filter depending on the current of the AC power supply, thereby suppressing unstable charging operation due to amplification of disturbance noise and switching noise of the charger itself.

[0003] Patent No. 5888710

[0004] According to the technology described in Patent Document 1, it is necessary to prepare a plurality of band-elimination filters that suppress amplification at the resonant frequency, which poses a problem of increasing the size of the on-board charger.

[0005] The present disclosure has been made in view of the above-mentioned problems, and aims to provide a charging method and a charging device that can suppress the influence of resonance that occurs when the charging device is connected to a battery while suppressing an increase in the size of the charging device.

[0006] In order to solve the above-mentioned problems, a charging method and a charging device according to the present disclosure calculate the efficiency of the charging device based on the input power and output power of the charging device when the charging device is connected in parallel with a battery and a capacitor and supplies power to the battery via the capacitor, and if it is determined that the efficiency is below a predetermined threshold, transition the charging device to an intermittent operation mode in which the charging device operates intermittently at an intermittent frequency. The intermittent frequency is higher than the frequency of resonance occurring between the battery and the capacitor, and in the intermittent operation mode, the gain of the ripple current flowing through the battery relative to the ripple current output from the charging device is 0 dB or less.

[0007] According to the present disclosure, it is possible to suppress the influence of resonance caused by connecting a charging device to a battery while suppressing an increase in size of the charging device.

[0008] 1 is a block diagram illustrating a configuration of a charging system including a charging device according to an embodiment of the present disclosure; FIG. 2 is a flowchart illustrating a control process of the charging device according to an embodiment of the present disclosure; FIG. 3 is a diagram illustrating a relationship between an intermittent frequency and a gain; and FIG. 4 is a diagram illustrating a relationship between an intermittent frequency and a phase difference.

[0009] Next, embodiments of the present disclosure will be described in detail with reference to the drawings. In the description, the same components are designated by the same reference numerals and redundant description will be omitted.

[0010] [Configuration of Charging System] Fig. 1 is a block diagram showing the configuration of a charging system including a charging device according to an embodiment of the present disclosure. As shown in Fig. 1, the charging system includes a charging device 10, a capacitor 20, a battery 30, and a controller 40. The charging system may be mounted on a vehicle (not shown).

[0011] The charging device 10 is connected in parallel with the battery 30 and the capacitor 20. The charging device 10 supplies power to the battery 30 via the capacitor 20. The charging device 10, the capacitor 20, and the battery 30 are electrically connected by electrical wiring such as a harness. The charging device 10 is also controlled by a controller 40.

[0012] For example, the charging device 10 is connected to an AC power source, converts the power input from the AC power source, and outputs the converted power to the capacitor 20. The charging device 10 is provided with a sensor that measures the power input from the AC power source (input power) and a sensor that measures the power output to the capacitor 20 (output power). The measured values ​​of the input power and output power are transmitted to the controller 40.

[0013] Alternatively, the charging device 10 and the AC power source may be connected by, for example, a charging plug. The charging device 10 may be provided with a sensor that detects the insertion state of the charging plug. The charging device 10 may also be provided with a sensor that detects the connection state with the AC power source. These sensors may detect whether or not the charging device 10 and the AC power source are electrically connected. Information on the insertion state or connection state (hereinafter referred to as the connection state, etc.) may be transmitted to the controller 40.

[0014] The charging device 10 may include an LLC converter 12. The charging device 10 may convert input power into output power using the LLC converter 12. Here, the LLC converter 12 converts DC current using resonance generated by the magnetizing inductance of a transformer and a coil and capacitor connected in series with the transformer. The current output from the LLC converter 12 can be controlled by controlling the switching frequency of the LLC converter 12. There are various types of circuits that can realize the LLC converter 12, and the circuit may be any of a full-bridge type, a half-bridge type, or a primary-secondary full-bridge type. The charging device 10 is not limited to the examples given here.

[0015] The LLC converter 12 can reduce the output current by increasing the switching frequency. To reduce the output current of the LLC converter 12 to a value less than a predetermined current amount, the LLC converter 12 is operated intermittently instead of increasing the switching frequency.

[0016] The state in which the LLC converter 12 operates intermittently is called an intermittent operation mode, whereas the state in which the LLC converter 12 operates continuously is called a continuous operation mode.

[0017] The intermittent operation mode will now be described. An intermittent period is one cycle consisting of an on period during which current is output from the LLC converter 12 and an off period during which no current is output from the LLC converter 12. For example, the interval between the ends of the on periods may be the intermittent period. By making the off period longer than the on period, the current output by the charging device 10 is effectively reduced. The reciprocal of the intermittent period is called the intermittent frequency. By operating the LLC converter 12 intermittently, switching loss in the LLC converter 12 can be suppressed and the required turn-on / off times of the switching elements can be ensured.

[0018] In the continuous operation mode, there is no off period during which no current is output from the LLC converter 12, and the increase or decrease in the current output from the LLC converter 12 is controlled by increasing or decreasing the switching frequency.

[0019] The intermittent frequency is set to a low value within a range that does not increase the ripple current in the capacitor 20. By lengthening the off period (reducing the intermittent frequency), the current output by the charging device 10 can be effectively reduced, but the ripple current increases. Also, by shortening the off period (increasing the intermittent frequency), the ripple current can be reduced, but the current output by the charging device 10 cannot be effectively reduced.

[0020] Additionally, the charging device 10 may be provided with a phase sensor that acquires the phase of the output current of the charging device 10. Specifically, the phase sensor may acquire the phase of the current flowing between the charging device 10 and the capacitor 20. Information indicating the phase of the current acquired by the phase sensor may be transmitted to the controller 40.

[0021] The capacitor 20 smoothes the power output from the charging device 10 and supplies it to the battery 30. In Fig. 1, the capacitor 20 is shown as a single capacitor, but is not limited to this example. For example, an inverter may be installed between the charging device 10 and the battery 30, and the capacitor 20 may be a capacitor component included in the inverter.

[0022] The battery 30 is charged by power supplied from the charging device 10 via the capacitor 20. The battery 30 may be composed of various types of batteries. For example, the battery 30 may include a lithium ion battery. Alternatively, the battery 30 may be various types of batteries such as a zinc battery, a sodium ion battery, or a magnesium ion battery. The battery 30 is not limited to the examples given here.

[0023] The battery 30 may also be provided with a temperature sensor that measures the temperature of the battery 30. For example, the temperature sensor may measure the temperature inside the battery 30 so that the state of the battery 30 can be accurately determined based on the temperature. Information indicating the temperature of the battery 30 may be transmitted to the controller 40.

[0024] Furthermore, a coolant may be supplied to the battery 30 from an external source in order to cool the battery 30. More specifically, a flow path through which the coolant flows may be provided inside the battery 30, and heat may be exchanged between the supplied coolant and the battery 30. A temperature sensor may be provided to measure the temperature of the coolant before it cools the battery 30. Information indicating the temperature of the coolant may be transmitted to the controller 40.

[0025] The battery 30 may also be provided with a phase sensor that acquires the phase of the current flowing through the battery 30. Specifically, the phase sensor may acquire the phase of the current flowing between the capacitor 20 and the battery 30. Information indicating the phase of the current acquired by the phase sensor may be transmitted to the controller 40.

[0026] Another note about the relationship between the battery 30 and ripple current: The electrical wiring connecting the charging device 10, the capacitor 20, and the battery 30 has an inductance component. Therefore, if the resonant frequency determined by the inductance component of the electrical wiring and the capacitance component of the capacitor 20 matches the intermittent frequency of the charging device 10, the ripple current may increase. If the increased ripple current causes rapid electrodeposition within the battery 30, a short circuit may occur between the positive and negative electrodes of the battery 30. In this way, an increase in ripple current is likely to lead to deterioration of the battery 30.

[0027] Therefore, in order to suppress the effects of resonance that occur when the charging device 10 is connected to the battery 30 and to suppress deterioration of the battery 30, it is necessary to set the intermittent frequency so that the resonance frequency and the intermittent frequency do not coincide.

[0028] The controller 40 controls the charging device 10. For example, the controller 40 is a general-purpose computer including a CPU (Central Processing Unit), a memory, and an input / output unit. A computer program (control program) for controlling the charging device 10 is installed in the computer. By executing the computer program, various functions described below are realized.

[0029] The control program may be stored in a storage medium such as a non-transitory computer-readable medium, or may be distributed via a telecommunications line.

[0030] The following describes an example in which various functions are realized by software, but it is also possible to realize the various functions by preparing dedicated hardware for executing the information processing described below.Furthermore, the various functions may be realized by individual hardware.

[0031] The controller 40 acquires the input power and output power of the charging device 10, and calculates the efficiency of the charging device 10 based on the input power and the output power. For example, the controller 40 may acquire the input power and the output power from a sensor provided in the charging device 10. The controller 40 may also include a divider and calculate the efficiency by dividing the output power by the input power.

[0032] Furthermore, the controller 40 determines whether the calculated efficiency is below a predetermined threshold. If it is determined that the calculated efficiency is below the predetermined threshold, the controller 40 transitions the charging device 10 to an intermittent operation mode in which the charging device 10 operates intermittently at an intermittent frequency. The controller 40 controls the charging device 10 to output a current during an on period in the intermittent operation mode. The controller 40 controls the charging device 10 to not output a current during an off period in the intermittent operation mode.

[0033] The controller 40 may set the intermittent frequency based on the calculated efficiency, and may then control the charging device 10 to operate at the set intermittent frequency.

[0034] Here, the intermittent frequency is higher than the frequency of the resonance occurring between the battery 30 and the capacitor 20, and is set in a range such that in the intermittent operation mode, the gain of the ripple current flowing through the battery 30 relative to the ripple current output from the charging device 10 is 0 dB or less.

[0035] 3 is a diagram showing the relationship between the intermittent frequency and the gain, in which a curve CV1 shows how the gain of the ripple current flowing through the battery 30 relative to the ripple current output from the charging device 10 changes depending on the set intermittent frequency.

[0036] If the resonance frequency determined by the inductance component of the electrical wiring and the capacitance component of capacitor 20 is frequency FB, curve CV1 has a peak at frequency FB. To reduce the ripple current generated in battery 30, a frequency FG at which the gain is 0 dB or less is determined in advance and registered in controller 40. Then, controller 40 sets the intermittent frequency in a range RG where the intermittent frequency is equal to or greater than frequency FG.

[0037] Furthermore, the controller 40 may maintain the intermittent operation mode until the connection between the power source AC (external power source) that supplies power to the charging device 10 and the charging device 10 is released. For example, the controller 40 may acquire information such as the connection state from a sensor provided in the charging device 10 and determine whether the connection between the power source AC and the charging device 10 has been released.

[0038] Alternatively, the controller 40 may obtain a temperature difference obtained by subtracting a reference temperature from the temperature of the battery 30. Then, when it is determined that the temperature difference exceeds a predetermined temperature difference, the controller 40 may transition the charging device 10 to the intermittent operation mode. For example, the controller 40 may include a subtractor and calculate the temperature difference by subtracting the reference temperature from the temperature obtained by a temperature sensor provided in the battery 30.

[0039] Here, the reference temperature may be the temperature of the refrigerant before it is supplied to the battery 30 and cools the battery 30. Alternatively, the reference temperature may be the temperature outside the battery 30, particularly the temperature around the charging device 10.

[0040] Thus, by calculating the temperature difference using the controller 40, it is possible to grasp the degree to which the temperature inside the battery 30 has risen compared to the surroundings. It is also possible to grasp the degree to which a load is being placed on the battery 30 as the battery 30 is being charged. In a situation in which the load on the battery 30 is increasing as the battery 30 is being charged, the load on the battery 30 can be reduced by transitioning the charging device 10 to the intermittent operation mode.

[0041] Furthermore, the controller 40 may acquire a phase difference between the output current of the charging device 10 and the current flowing through the battery 30. Then, when it is determined that the phase difference is less than a predetermined phase difference, the controller 40 may transition the charging device 10 to an intermittent operation mode. For example, the controller 40 may include a subtractor and calculate the phase difference by subtracting the phase of the output current of the charging device 10 from the phase of the current flowing through the battery 30, which is acquired by a phase sensor provided in the battery 30.

[0042] A note on the relationship between the intermittent frequency and the phase difference is provided below. Figure 4 is a diagram showing the relationship between the intermittent frequency and the phase difference. In Figure 4, curve CV2 shows how the phase difference between the output current of the charging device 10 and the current flowing through the battery 30 changes depending on the set intermittent frequency.

[0043] Experiments have revealed that there is a correlation between the gain and phase of the current flowing through the battery 30 with respect to the output current of the charging device 10. Therefore, instead of the gain, the charging device 10 may be transitioned to the intermittent operation mode when the phase difference falls below a predetermined phase difference θ1.

[0044] By determining whether to transition to intermittent operation mode based on the gain of the ripple current flowing into the battery 30 relative to the ripple current output from the charging device 10, as well as the phase difference of the current flowing into the battery 30 relative to the output current of the charging device 10, more accurate control of the charging device 10 can be achieved.

[0045] In addition, in the intermittent operation mode, the controller 40 may control the intermittent frequency based on the phase difference so that the calculated phase difference becomes a target phase difference θ2 that is smaller than the predetermined phase difference θ1. For example, the control of the intermittent frequency based on the phase difference may be feedback control. The manner of control of the intermittent frequency is not limited to the example given here.

[0046] [Processing Procedure for Controlling the Charging Device] Fig. 2 is a flowchart showing a processing for controlling the charging device according to an embodiment of the present disclosure. The processing shown in Fig. 2 may be repeatedly executed at a predetermined cycle.

[0047] In step S101 , the controller 40 acquires the connection state and the like from a sensor provided in the charging device 10 .

[0048] In step S103, the controller 40 determines whether the charging device 10 is connected to an external power source that supplies power to the charging device 10. If it is determined that the external power source is not connected to the charging device 10 (NO in step S103), the processing in FIG. 2 ends.

[0049] On the other hand, if it is determined that the external power supply and the charging device 10 are connected (YES in step S103), the controller 40 acquires the input power and the output power of the charging device 10 in step S105.

[0050] In step S107, the controller 40 calculates the efficiency of the charging device 10 based on the input power and the output power.

[0051] In step S109, the controller 40 determines whether the calculated efficiency is below a predetermined threshold value.

[0052] If it is determined that the efficiency is lower than the predetermined threshold (YES in step S109), the process proceeds to step S121. The controller 40 transitions the charging device 10 to the intermittent operation mode and controls the charging device 10 in the intermittent operation mode.

[0053] If it is determined that the efficiency is not below the predetermined threshold (NO in step S109), in step S111, the controller 40 obtains a temperature difference obtained by subtracting the reference temperature from the temperature of the battery 30.

[0054] In step S113, the controller 40 determines whether the temperature difference exceeds a predetermined temperature difference.

[0055] If it is determined that the temperature difference exceeds the predetermined temperature difference (YES in step S113), the process proceeds to step S121.

[0056] If it is determined that the temperature difference does not exceed the predetermined temperature difference (NO in step S113), in step S115, the controller 40 obtains the phase difference of the current flowing through the battery 30 relative to the output current of the charging device 10.

[0057] In step S117, the controller 40 determines whether the phase difference is less than a predetermined phase difference.

[0058] If it is determined that the phase difference is less than the predetermined phase difference (YES in step S117), the process proceeds to step S121.

[0059] If it is determined that the phase difference is not less than the predetermined phase difference (NO in step S117), in step S119, the controller 40 controls the charging device 10 in the continuous operation mode.

[0060] After the processes of steps S119 and S121, the process returns to step S101.

[0061] [Effects of the Embodiments] As described in detail above, the charging method and charging device according to the present disclosure, when connected in parallel with a battery and a capacitor and supplying power from the charging device to the battery via the capacitor, calculates the efficiency of the charging device based on the input power and output power of the charging device, and if it is determined that the efficiency is below a predetermined threshold, transitions the charging device to an intermittent operation mode in which the charging device operates intermittently at an intermittent frequency. The intermittent frequency is higher than the frequency of resonance occurring between the battery and the capacitor, and in the intermittent operation mode, the gain of the ripple current flowing through the battery relative to the ripple current output from the charging device is 0 dB or less.

[0062] This makes it possible to suppress the influence of resonance caused by connecting the charging device to the battery while preventing the charging device from becoming larger. Furthermore, it is possible to suppress ripple current and prevent battery deterioration. Furthermore, it is possible to achieve both a reduction in ripple current and an effective reduction in the current output by the charging device.

[0063] The controller may maintain the intermittent operation mode until the connection between the charging device and the external power source that supplies power to the charging device is disconnected. This allows the intermittent operation mode to be maintained until the battery is fully charged, thereby suppressing battery deterioration. As a result, the reliability of battery charging can be improved.

[0064] The controller may acquire a temperature difference obtained by subtracting a reference temperature from the battery temperature, and when it determines that the temperature difference exceeds a predetermined temperature difference, transition the charging device to an intermittent operation mode. This reduces the load on the battery during charging and improves the reliability of battery charging.

[0065] The reference temperature may be the temperature of the refrigerant before it is supplied to the battery and begins to cool the battery. This allows the magnitude of the battery temperature rise associated with charging to be estimated with high accuracy. The magnitude of the load applied to the battery during charging can be accurately determined.

[0066] The controller may acquire a phase difference between the output current of the charging device and the current flowing through the battery, and when it is determined that the phase difference is less than a predetermined phase difference, transition the charging device to the intermittent operation mode. This makes it possible to determine whether to transition to the intermittent operation mode based on the phase difference of the current in addition to the gain, thereby achieving more accurate control of the charging device.

[0067] The controller may control the intermittent frequency based on the phase difference in the intermittent operation mode so that the phase difference becomes a target phase difference that is smaller than a predetermined phase difference. This allows for more accurate control of the charging device and more reliable suppression of ripple current flowing through the battery.

[0068] The charging device may include an LLC converter, which enables the implementation of an intermittent operation mode, thereby reducing the ripple current and effectively reducing the current output by the charging device.

[0069] The battery may include a lithium ion battery. This makes it possible to suppress the ripple current and inhibit deterioration of the lithium ion battery, which is susceptible to deterioration due to increased ripple current.

[0070] Each of the functions described in the above embodiments may be implemented by one or more processing circuits, including programmed processors, electrical circuits, and even devices such as application specific integrated circuits (ASICs), or circuit components arranged to perform the described functions.

[0071] Although the contents of the present disclosure have been described above based on the embodiments, the present disclosure is not limited to these descriptions, and various modifications and improvements are possible, which will be apparent to those skilled in the art. The descriptions and drawings that form part of this disclosure should not be understood as limiting the present disclosure. Various alternative embodiments, examples, and operating techniques will be apparent to those skilled in the art from this disclosure.

[0072] Of course, the present disclosure includes various embodiments not described herein. Therefore, the technical scope of the present disclosure is defined only by the invention-specifying matters according to the scope of the claims that are appropriate from the above description.

[0073] AC power supply (external power supply) 10: charging device 12: LLC converter 20: capacitor 30: battery 40: controller θ1: predetermined phase difference θ2: target phase difference

Claims

1. A charging method involving a controller that controls a charging device that is connected in parallel to a battery and a capacitor and supplies power to the battery via the capacitor, wherein the controller: acquires input power and output power of the charging device; calculates the efficiency of the charging device based on the input power and the output power; and, if it is determined that the efficiency is below a predetermined threshold, transitions the charging device to an intermittent operation mode in which the charging device operates intermittently at an intermittent frequency; the intermittent frequency is higher than a frequency of resonance occurring between the battery and the capacitor; and in the intermittent operation mode, the gain of the ripple current flowing through the battery relative to the ripple current output from the charging device is 0 dB or less.

2. The charging method according to claim 1, wherein the controller maintains the intermittent operation mode until the connection between the charging device and an external power source that supplies power to the charging device is released.

3. The charging method according to claim 1 or 2, wherein the controller obtains a temperature difference obtained by subtracting a reference temperature from the temperature of the battery, and when it is determined that the temperature difference exceeds a predetermined temperature difference, transitions the charging device to the intermittent operation mode.

4. The charging method according to claim 3, wherein the reference temperature is the temperature of the refrigerant before it is supplied to the battery and cools the battery.

5. A charging method according to any one of claims 1 to 4, wherein the controller obtains a phase difference between the output current of the charging device and the current flowing through the battery, and when it is determined that the phase difference is below a predetermined phase difference, transitions the charging device to the intermittent operation mode.

6. The charging method according to claim 5, wherein the controller controls the intermittent frequency based on the phase difference in the intermittent operation mode so that the phase difference becomes a target phase difference that is smaller than the predetermined phase difference.

7. A charging method according to any one of claims 1 to 6, wherein the charging device comprises an LLC converter.

8. The charging method according to any one of claims 1 to 7, wherein the battery comprises a lithium ion battery.

9. A charging device controlled by a controller, wherein the charging device is connected in parallel to a battery and a capacitor and supplies power to the battery via the capacitor, the controller obtains input power and output power of the charging device, calculates the efficiency of the charging device based on the input power and the output power, and when it is determined that the efficiency is below a predetermined threshold, transitions the charging device to an intermittent operation mode in which the charging device operates intermittently at an intermittent frequency, the intermittent frequency being higher than a frequency of resonance occurring between the battery and the capacitor, and in the intermittent operation mode, the gain of the ripple current flowing through the battery relative to the ripple current output from the charging device is 0 dB or less.

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