JP2019129555A - Dc/dc converter, power supply system, and charging/discharging method of secondary battery - Google Patents

Abstract

To provide a DC/DC converter, a power supply system, and a charging/discharging method of a secondary battery capable of increasing the temperature by charging/discharging an in-vehicle secondary battery.SOLUTION: A DC/DC converter is connected between a secondary battery mounted on a vehicle and a capacitor that temporarily stores electric power. The DC/DC converter charges and discharges the secondary battery and the capacitor with a predetermined cycle and a predetermined current waveform.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a DC / DC converter connected between a vehicle-mounted secondary battery and a storage battery that temporarily stores electric power, a power supply system including the DC / DC converter, and a method of charging / discharging a secondary battery.

  Conventionally, an auxiliary battery that supplies auxiliary devices is mounted on the vehicle, and HV (Hybrid Vehicle: hybrid vehicle), PHV (Plug-in Hybrid Vehicle: plug-in hybrid vehicle), EV (Electric Vehicle: electric vehicle) In a vehicle having a motor such as), a driving battery is mounted. In addition, vehicles that generate regenerative power in a generator by converting kinetic energy of the vehicle into electric power during deceleration and store the generated regenerative power in a battery, capacitor, or other power storage device are also widespread.

  A battery utilizing a chemical reaction is susceptible to temperature changes, and tends to deteriorate the characteristics of charge and discharge (hereinafter also referred to as charge and discharge) particularly in a low temperature environment. On the other hand, many inventions have been devised to prevent such deterioration of characteristics at low temperatures.

  For example, in Patent Document 1, when the temperature of the driving secondary battery (battery) is lower than the set temperature, the secondary battery (auxiliary battery) for electrical equipment alternates with the driving secondary battery. Particularly, there is described a technique of heating the secondary battery for driving by self-heating by charging and discharging. Further, Patent Document 2 discloses a driving secondary battery by using a half bridge circuit and an inductor to charge or discharge a driving secondary battery with a stepped down voltage. A technique for generating a ripple current of a predetermined frequency to raise the temperature is described.

JP 2003-92805 A International Publication No. 2011/004464

  However, the technique disclosed in Patent Document 1 charges and discharges between a high-pressure secondary battery for driving and a low-pressure secondary battery for electrical equipment, and the technique disclosed in Patent Document 2 The charge / discharge ripple current is generated with respect to the driving secondary battery, and none of them is used to charge / discharge the low voltage side secondary battery alone.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a DC / DC converter, a power supply system, and a secondary that can charge and discharge an in-vehicle secondary battery to raise the temperature. To provide a method for charging and discharging a battery.

  A DC / DC converter according to an aspect of the present invention is a DC / DC converter connected between a secondary battery mounted on a vehicle and a storage battery for temporarily storing power, the secondary battery and the storage battery Are charged and discharged with a predetermined period and with a predetermined current waveform.

  A power supply system according to an aspect of the present invention includes the above-described DC / DC converter and the storage battery.

  In the charge and discharge method of a secondary battery according to an aspect of the present invention, the secondary battery is charged with a DC / DC converter connected between the secondary battery mounted on a vehicle and a storage battery that temporarily stores electric power. A method of discharging includes charging and discharging the secondary battery and the capacitor with each other at a predetermined cycle and with a predetermined current waveform.

  The present application can not only be realized as a DC / DC converter having such a characteristic processing unit, a power supply system, and a method of charging and discharging a secondary battery, and also causes a computer to execute such characteristic processing steps. It can be realized as a program for Further, part or all of the DC / DC converter can be realized as an integrated circuit, or can be realized as another system including a DC / DC converter and / or a power supply system.

  According to the above, it is possible to charge and discharge the secondary battery for supplying power to the load on the vehicle to raise the temperature.

FIG. 1 is a block diagram showing a configuration example of a power supply system according to a first embodiment. It is explanatory drawing which shows an example of the equivalent circuit model of a low voltage battery. It is an explanatory view showing an example of an impedance spectrum of a low voltage battery. It is a block diagram which shows the structural example of a DC / DC converter. It is a timing chart which shows a relation between charge and discharge of a low voltage battery, and pressure increase and decrease by DC / DC converter. It is a graph which shows the time change of the battery temperature at the time of heating up a low voltage battery. 10 is a block diagram illustrating a configuration example of a power supply system according to Modification Example 1. FIG. It is a block diagram which shows the structural example of the power supply system which concerns on the modification 2. FIG. FIG. 16 is a block diagram showing an example of configuration of a power supply system according to a modification 3;

Description of the embodiment of the present invention
First, the embodiments of the present invention will be listed and described. In addition, at least part of the embodiments described below may be arbitrarily combined.

(1) A DC / DC converter according to one aspect of the present invention is a DC / DC converter connected between a secondary battery mounted on a vehicle and a storage battery for temporarily storing power, the secondary The battery and the capacitor are mutually charged and discharged in a predetermined cycle and with a predetermined current waveform.

(15) A method of charging and discharging a secondary battery according to an aspect of the present invention is a method of connecting a secondary battery according to an aspect of the present invention, the method comprising: A method of charging / discharging a battery, comprising charging and discharging the secondary battery and the battery with a predetermined period and a predetermined current waveform.

  In this aspect, the DC / DC converter is connected between the in-vehicle secondary battery and the battery that temporarily stores electric power, and the secondary battery is discharged and charged. Discharge and charge of the secondary battery are alternately performed. Charging / discharging in this case is performed with a predetermined cycle and a predetermined current waveform. As a result, charging and discharging are performed with a cycle in which the temperature increase effect of the secondary battery is relatively large and the current waveform with a relatively small amount of increase in the terminal voltage of the secondary battery in comparison at the same magnitude of charge and discharge current. Therefore, the secondary battery can be safely heated in a relatively short time.

(2) The secondary battery is preferably a non-aqueous electrolyte secondary battery including a lithium ion battery.

  In the case where the secondary battery is a non-aqueous electrolyte secondary battery including a lithium ion battery, the mobility of the ions in the electrolytic solution is increased by charging and discharging the capacitor with each other with the capacitor at low temperature. Deterioration of the discharge characteristics of the secondary battery is preferably prevented.

(3) The capacitor preferably includes an electric double layer capacitor, a lithium ion capacitor or a lithium ion battery.

  When the battery is an electric double layer capacitor, a lithium ion capacitor, or a lithium ion battery, it is excellent in rapid charge / discharge characteristics, and therefore, voltage fluctuation of the load due to rapid fluctuation of load current is suitably prevented. Further, when the temperature of the secondary battery is raised, the temperature of the capacitor or the lithium ion battery is also raised simultaneously to prevent the deterioration of the charge / discharge characteristics.

(4) It is preferable that the period is a reciprocal of a frequency at which the absolute value of the internal impedance of the secondary battery is equal to or less than a value larger by a predetermined value than the minimum value of the absolute value.

  Voltage fluctuation of the secondary battery with respect to the magnitude of the charge and discharge current by charging and discharging the secondary battery in a cycle represented by the reciprocal of the frequency at which the absolute value of the internal impedance is smaller than the minimum value by a predetermined value or less The width is relatively small, and the deterioration of the secondary battery is prevented.

(5) The period is preferably a reciprocal of a frequency at which the absolute value of the imaginary component of the internal impedance is equal to or less than a second value.

  By charging and discharging the secondary battery in a cycle represented by the reciprocal of the frequency at which the absolute value of the imaginary component of the internal impedance is less than or equal to the second value, the real component of the internal impedance among the charge and discharge currents of the secondary battery The current flowing through the secondary battery becomes relatively large to generate Joule heat, and the secondary battery is efficiently heated.

(6) The current waveform is preferably sinusoidal or rectangular.

  When the current waveform of charge and discharge is sinusoidal, since the harmonic components included in the charge and discharge current are relatively small, the charge and discharge current should be adjusted appropriately by selecting the charge and discharge cycle. The voltage fluctuation range is relatively small. Moreover, when the current waveform of charging / discharging is a rectangular wave shape, the temperature increase effect of a secondary battery becomes comparatively large compared with the peak value of the same charging / discharging current.

(7) It is preferable that the said battery is connected to the load of the said vehicle.

  When the load is directly connected to the capacitor, the rapid fluctuation of the load current is absorbed by the capacitor without time delay.

(8) The secondary battery is preferably connected to a load of the vehicle.

  When the load is directly connected to the secondary battery, no loss occurs in the power supplied from the secondary battery to the load.

(9) A power supply system according to an aspect of the present invention includes the above-described DC / DC converter and the storage battery.

  In this aspect, the storage battery included in the power supply system is heated at the same time as the secondary battery.

(10) It is preferable to further provide the said secondary battery.

  The power supply system further includes a secondary battery in addition to the storage battery, and these are managed integrally with the DC / DC converter.

(11) It is preferable that the secondary battery is charged by a second DC / DC converter that steps down the voltage of the second secondary battery for driving the vehicle.

The voltage of the second secondary battery for driving the vehicle is reduced by the second DC / DC converter, and power is supplied to the secondary battery. Thereby, for example, when the SOC (State Of Charge) of the secondary battery decreases, the secondary battery is charged by the second secondary battery, and power is also supplied to the load.
(12) It is preferable to further provide the second DC / DC converter.

  The power supply system further includes a second DC / DC converter in addition to the capacitor, and these are managed integrally with the DC / DC converter.

(13) Preferably, the secondary battery is charged by an on-vehicle generator that generates electric power in conjunction with an engine mounted on the vehicle.

  Power is supplied from the on-board generator to the secondary battery. For example, when the SOC of the secondary battery is lowered, the on-board generator charges the secondary battery, and power is also supplied to the load.

(14) It is preferable to further include a power control unit that causes the DC / DC converter to charge and discharge the secondary battery and the capacitor based on the detection result obtained from the detection unit that detects the temperature of the secondary battery.

  Since the power supply control unit causes the DC / DC converter to charge and discharge based on the temperature of the secondary battery, for example, when the temperature of the secondary battery is lower than a predetermined temperature, it is necessary to raise the temperature of the secondary battery. The secondary battery and the battery are mutually charged / discharged by the / DC converter.

Details of the Embodiment of the Present Invention
Specific examples of a DC / DC converter, a power supply system, and a method of charging and discharging a secondary battery according to an embodiment of the present invention will be described below with reference to the drawings. The present invention is not limited to these exemplifications, but is shown by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. Moreover, the technical features described in each embodiment can be combined with each other.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration example of a power supply system S according to the first embodiment. The power supply system S is connected to a DC / DC converter 1 for converting the voltage of a low voltage battery 100 (corresponding to a secondary battery) mounted on a vehicle C and supplying power to a load group 200 mounted on a vehicle. And at least a storage battery 2 for temporarily storing power. The DC / DC converter 1 is connected between the low voltage battery 100 and the storage battery 2 and converts voltage bidirectionally. The low voltage battery 100 may be included in the power supply system S.

  The low voltage battery 100 is, for example, a non-aqueous electrolyte secondary battery such as a lithium ion battery, and has a much higher volumetric energy density and mass energy density than conventional lead storage batteries. Low-voltage battery 100 is a DC / DC converter 3 (second DC) that reduces the voltage of high-voltage battery 300 (corresponding to a second secondary battery) for driving vehicle C when the battery voltage or SOC decreases. Is equivalent to the DC / DC converter). The low voltage battery 100 may be charged without the DC / DC converter 1 by a DC / DC converter that steps down the voltage of the high voltage battery 300. The DC / DC converter 3 may be included in the power supply system S.

  The battery 2 is, for example, an electric double layer capacitor (EDLC = Electronic Double-Layer Capacitor) or a lithium ion capacitor, and has an internal resistance lower than that of the low voltage battery 100 and can be charged / discharged in a short time. A lithium ion battery may be used as the battery 2.

  The power supply system S further controls the charging / discharging of the DC / DC converter 1 based on the detection result acquired from the temperature sensor 41 which detects the temperature of the DC / DC converter 1 when starting the vehicle C, etc. A power supply control unit 4 which is a unit) may be provided. The power supply control unit 4 detects a decrease in the voltage of the low voltage battery 100 or a decrease in the SOC to cause the DC / DC converter 3 to discharge the high voltage battery 300 and causes the DC / DC converter 1 to charge the low voltage battery 100. In this case, the power supply voltage supplied to the storage battery 2 and the load group 200 is adjusted to be constant by the DC / DC converter 3, and the adjusted voltage is converted by the DC / DC converter 1 to charge the low voltage battery 100.

  In the configuration described above, when the low voltage battery 100 is appropriately charged, the DC / DC converter 1 converts the voltage of the low voltage battery 100 to supply the power supply voltage to the load group 200 and the storage battery 2. Is supplied with operating power, and the battery 2 is charged to the power supply voltage. The DC / DC converter 3 may convert the voltage of the high voltage battery 300 to constantly supply the power supply voltage to the load group 200 and the storage battery 2, and the low voltage battery 100 may back up this.

  When the load group 200 includes an inductive load, when the power supply voltage suddenly fluctuates within a short time, the capacitor 2 suppresses fluctuations in the power supply voltage. For example, a high voltage system such as the high voltage battery 300 is floating from the vehicle body for safety, and an inrush current flows through a relay that releases the floating when the vehicle C is started. The decrease in power supply voltage can be suppressed by the discharge current from. When the low voltage battery 100 or the DC / DC converter 1 fails, the storage battery 2 supplies operating power to the load group 200 for a certain period of time.

  When the low voltage battery 100 is a non-aqueous electrolyte secondary battery such as a lithium ion battery, the movement of ions in the electrolyte is slowed at low temperature, the discharge characteristics are degraded, and the voltage drop in large current discharge becomes large. It has also been pointed out that lithium ions in the electrolyte may precipitate as lithium metal at extremely low temperatures. Therefore, in the first embodiment, when the temperature of the low-voltage battery 100 acquired from the temperature sensor 41 when the vehicle C is started is lower than a predetermined temperature, the power control unit 4 causes the DC / DC converter 1 to discharge the low-voltage battery 100 and the battery 2. , And discharge of the storage battery 2 and charge of the low voltage battery 100 are alternately performed. During this time, Joule heat is generated by the charge / discharge current flowing to the internal resistance of the low voltage battery 100 to raise the temperature of the low voltage battery 100, so that the deterioration of the discharge characteristics is alleviated. However, care should be taken so that the voltage of the low voltage battery 100 does not become an overvoltage due to the voltage drop occurring in the internal resistance.

  Here, characteristics when the low-voltage battery 100 is a lithium ion battery will be described. FIG. 2 is an explanatory view showing an example of an equivalent circuit model of the low voltage battery 100. As shown in FIG. The equivalent circuit model represents the internal impedance of the low-voltage battery 100. For example, four parallel circuits of a voltage source having an open circuit voltage OCV, a resistor R1, resistors R2 to R5, and capacitors C2 to C5 are provided. It is composed of a combination of circuits connected in series. The open circuit voltage OCV is determined by static balance of the positive electrode, the negative electrode, and the electrolyte, and the internal impedance is determined by a dynamic mechanism. When charging current or discharging current flows, a battery voltage obtained by subtracting a voltage drop due to the internal impedance from OCV is externally observed as a terminal voltage.

  More specifically, resistance R1 represents, for example, resistance of the electrolyte bulk, resistances R2 to R5 represent, for example, interface charge transfer resistance and diffusion impedance, and capacitors C2 to C5 represent, for example, electric double layer capacitance Represents. The resistance of the electrolytic solution bulk includes the conduction resistance of lithium (Li) ions in the electrolytic solution, the electronic resistance at the positive electrode and the negative electrode, and the like. The interface charge transfer resistance includes charge transfer resistance and film resistance on the surface of the active material. The diffusion impedance is an impedance resulting from the diffusion process of lithium ions into the active material particles.

  FIG. 3 is an explanatory diagram showing an example of the impedance spectrum of the low-voltage battery 100. In FIG. 3, the horizontal axis indicates the real component Zr of the impedance Z, and the vertical axis indicates the imaginary component Zi of the impedance Z. The solid line represents the characteristics when the relatively low voltage battery 100 is placed in a normal temperature environment, and the broken line represents the characteristics of the low voltage battery 100 when degraded or placed in a low temperature environment. As shown in FIG. 3, when the low-voltage battery 100 is deteriorated or placed in a low-temperature environment, the arc of the impedance spectrum increases and the internal impedance increases, but the so-called resonance frequency at which the imaginary component Zi is zero is substantially equal. It is constant, and the magnitude of the real number component at the resonance frequency is also substantially constant.

  The internal resistance R of the low voltage battery 100 mainly includes the resistance Rs of the electrolyte bulk and the interface charge transfer resistance Rc. On the other hand, when the measurement frequency by the AC impedance method is lowered from, for example, a frequency of about 1 kHz to a frequency of about 0.1 Hz, the internal impedance of the low-voltage battery 100 is zero at the resonance frequency and the imaginary component Zi becomes zero. The extremum is taken in a region called a frequency range (near regions indicated by reference symbols fb and fb ′ in FIG. 3), and then it is turned to increase again. This increase is known to contribute to diffusion impedance. At frequencies higher than the boundary frequency region, the internal impedance of the low-voltage battery 100 is approximated by the total value of the resistance Rs of the electrolyte bulk and the interface charge transfer resistance Rc. The

As described above, when Joule heat is generated in the internal resistance R by the charge / discharge current I flowing to the low voltage battery 100, the voltage drop of the internal resistance R is represented by I × R while the Joule heat is I ² × It is proportional to R. Therefore, in order to increase the Joule heat while keeping the voltage drop constant, the low-voltage battery 100 may be charged and discharged at a cycle that is the reciprocal of the frequency at which the internal resistance R decreases. Specifically, it is ideal to charge and discharge at a cycle that is the reciprocal of the resonance frequency, but the cycle represented by the reciprocal of the frequency at which the absolute value of the internal impedance is not more than a predetermined value greater than the minimum value It is preferable to charge and discharge the More preferably, charging / discharging is performed in a cycle represented by the reciprocal of the frequency at which the absolute value of the imaginary component of the internal impedance is equal to or less than the second value.

  Next, the configuration and operation of the DC / DC converter 1 will be described. FIG. 4 is a block diagram illustrating a configuration example of the DC / DC converter 1. The DC / DC converter 1 is a full-bridge circuit having two arms A and B including a switching element such as a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor: hereinafter referred to as a transistor), and drives each transistor on / off. And a drive control unit 10 having a drive circuit 11.

  The transistor Q1 of the arm A has a drain connected to one end of the smoothing capacitor C11 and is connected to one end of the low voltage battery 100 via the resistor R11, and a source connected to the drain of the transistor Q2 and one end of the inductor L1. The gate is connected to the drive circuit 11. The source of the transistor Q 2 is connected to the common potential, and the gate is connected to the drive circuit 11. The other end of the capacitor C11 and the other end of the low voltage battery 100 are connected to a common potential. Both ends of the resistor R11 are connected to the input terminal of the amplifier Z1. The amplifier Z1 is a current sense amplifier, and is adapted to provide the drive control unit 10 with a voltage proportional to the current flowing through the resistor R11.

  The transistor Q3 of the arm B has a drain connected to one end of the smoothing capacitor C12 and one end of the capacitor 2, a source connected to the drain of the transistor Q4 and the other end of the inductor L1, and a gate connected to the drive circuit 11. Yes. The source of the transistor Q4 is connected to the common potential, and the gate is connected to the drive circuit 11. The other end of the capacitor C12 and the other end of the capacitor 2 are connected to a common potential.

  In addition to the drive circuit 11, the drive control unit 10 generates a reference current waveform circuit 12 that generates a voltage representing the waveform of a reference current that is a reference of charge and discharge current, and generates and drives a triangular wave for generating a PWM signal. A triangular wave generation circuit 13 to be supplied to the circuit 11, an amplifier 14, and a comparator 15 are included. Drive circuit 11 is supplied with voltage V1 of low-voltage battery 100 and voltage V2 of capacitor 2. The reference current waveform circuit 12 generates a sinusoidal voltage in the first embodiment, but may generate another waveform such as a rectangular waveform or a triangular waveform.

  For example, the non-inverting input terminal of the amplifier 14 is connected to the output terminal of the amplifier Z1, and the inverting input terminal is connected to the output terminal of the reference current waveform circuit 12. The amplifier 14 is an error amplifier, amplifies the error of the current flowing through the resistor R11 with respect to the reference current that changes in a sine wave shape, and gives an error voltage to the drive circuit 11.

  For example, the non-inverted input terminal of the comparator 15 is connected to the output terminal of the reference current waveform circuit 12, and the inverted input terminal is connected to the common potential. The comparator 15 gives a signal indicating discharge or charge to the drive circuit 11 according to whether the polarity of the sinusoidal voltage representing the waveform of the reference current is positive.

  The drive circuit 11 determines the voltage conversion direction by the full bridge circuit having the arms A and B in accordance with a signal indicating discharge or charge provided from the comparator 15. The drive circuit 11 determines the step-down, step-up or through operation by the arms A and B in accordance with the determined voltage conversion direction and the magnitudes of the voltages V1 and V2.

  When the operation of the arm A or B is determined to be step-down, the PWM signal is provided from the drive circuit 11 to the transistor Q1 or Q3. When the operation of arm A or B is determined to be boosted, PWM signal is applied from drive circuit 11 to transistor Q2 or Q4. The PWM signal is generated, for example, by comparing the error voltage from the amplifier 14 with the triangular wave from the triangular wave generation circuit 13. If the operation of the arms A or B is determined to be through, the transistor Q1 or Q3 is fixed on and the transistor Q2 or Q4 is fixed off. Apart from the so-called dead time, the transistors Q1 and Q2 and the transistors Q3 and Q4 are turned on complementarily.

  FIG. 5 is a timing chart showing the relationship between charging and discharging of the low voltage battery 100 and step-up and step-down by the DC / DC converter 1. In the timing chart divided into five stages in FIG. 5, the same time axis (t) is set as the horizontal axis, and the vertical axis indicates the voltage or the state. The uppermost timing chart represents the time change of the reference current of the charge / discharge current. The reference current here is a sinusoidal current whose magnitude changes at a frequency close to the resonant frequency of the low voltage battery 100. This frequency is a frequency at which the absolute value of the internal impedance of the low voltage battery 100 is less than or equal to the minimum value by a predetermined value or less, and a frequency at which the absolute value of the imaginary component of the internal impedance is less than a second value near to zero. But there is.

  The timing chart of the second stage from the top represents a period during which the state of discharge and charge determined in accordance with the time change of the reference current continues. The timing chart of the third stage from the top represents an example of the timing at which the level relationship between the voltages V1 and V2 applied to the drive circuit 11 changes. The timing charts of the fourth and fifth stages from the top show the duration during which the buck and boost operations by arms A and B continue, which is determined based on the discharge and charge states and the high / low relationship of voltages V1 and V2. Represent.

  Here, it is assumed that the low voltage battery 100 is discharged in the period from time t0 to t2, and the low voltage battery 100 is charged in the period from time t2 to t4. Also, during the period from time t0 to t1 (t0 <t1 <t2) and during the period from time t3 to t4 (t2 <t3 <t4), voltage V1 is higher than voltage V2 and from time t1 to t3. It is assumed that the voltage V1 is lower than the voltage V2 during the period. Even in the case where the reference current has a rectangular wave shape, it is possible to assume the same discharge and charge periods as described above and the same voltage relationships as described above in the respective periods.

  For example, during the period from time t0 to t1 when the voltage V1 is higher than the voltage V2 in the period in which the discharge of the low voltage battery 100 is determined, the arm B is controlled smoothly and the voltage V1 is stepped down by the arm A. The current flowing through the resistor R11 during this step-down period is PWM controlled so as to change in accordance with the temporal change of the reference current. During the period from the time t1 to the time t2 when the voltage V1 is lower than the voltage V2, the arm A is controlled smoothly and the voltage V1 is boosted by the arm B, and the current flowing through the resistor R11 during this boosting period is the reference current. PWM control is performed so as to change following the time change. Various techniques have already been proposed for switching from step-down by the arm A to step-up by the arm B at time t1, and thus the description thereof is omitted here.

  Similarly, during the period from the time t2 to t3 when the voltage V1 is lower than the voltage V2 in the period in which charging of the low voltage battery 100 is determined, the arm A is controlled smoothly and the voltage V2 is stepped down by the arm B. During the step-down period, the current flowing through the resistor R11 is PWM controlled so as to change in accordance with the time change of the reference current. During the period from time t3 to t4 when the voltage V1 is higher than the voltage V2, the arm B is controlled through and the voltage V2 is boosted by the arm A, and the current flowing through the resistor R11 during this boosting period is the reference current. PWM control is performed so as to change following the time change.

  The above description of the operation of the drive control unit 10 exemplifies the case where the voltage signal and the like are processed by hardware, but the signal processing is performed by the software executed by the microcomputer and the like, and the transistors Q1 and Q2 are processed according to the result. , Q3 and Q4 may be driven. Further, the above description of the operation is based on the premise that the level relationship between the voltage V1 and the voltage V2 is not uniquely determined. For example, when the voltage V1 is always higher than the voltage V2, the arm B is not necessary, and the transistor Q4 And transistor Q3 is replaced with a conductor. Similarly, if the voltage V1 is always lower than the voltage V2, then the arm A is not needed, the transistor Q2 is reduced and the transistor Q1 is replaced by a conductor.

  Next, an actual measurement value of the battery temperature when the temperature of the low voltage battery 100 is raised by the charge and discharge current will be described. FIG. 6 is a graph showing the time change of the battery temperature when the low voltage battery 100 is heated. The graphs shown in the upper and lower two stages in FIG. 6 each have the same time axis (t) as the horizontal axis, and the vertical axis represents the temperature (° C.) of the low voltage battery 100. The upper graph shows the temperature change when the temperature rises with a sinusoidal charge / discharge current, and the lower graph shows the temperature change when the temperature rises with a rectangular wave charge / discharge current for comparison. Is.

  The low-voltage battery 100 used for the measurement is obtained by stacking three flat plate cells (unit batteries) having a capacity of 3 Ah with the plate surfaces thereof as a module. Among these, the change in temperature of the central cell is indicated by a solid line, and the change in temperature of the other two cells is indicated by a broken line and an alternate long and short dash line. The measurement point of temperature selected one specific point out of the four corners of the plate surface in each cell. The magnitude of the charge and discharge current is 90 Ap-p. The temperature of the low-voltage battery 100 at the start of temperature increase is −30 ° C.

  As shown in the upper part of FIG. 6, when the temperature is increased with a sinusoidal charge / discharge current, the battery temperature rises by about 10 ° C. in approximately 15 minutes. When the temperature is raised by the rectangular wave charge / discharge current, the battery temperature rises by about 10 ° C. in about 7 minutes. In any case, the terminal voltage of the low voltage battery 100 does not become an overvoltage while continuing the charge and discharge for about 30 minutes, and no particular abnormality is recognized.

  As described above, according to the first embodiment, the DC / DC converter 1 is connected between the low-voltage battery 100 mounted on the vehicle and the storage battery 2 that temporarily stores electric power. Charging of the storage battery 2, discharging of the storage battery 2 and charging of the low voltage battery 100 are performed alternately. Charging / discharging in this case is performed with a predetermined cycle and a predetermined current waveform. Therefore, charging / discharging is performed with a current waveform having a relatively large temperature rise effect of low-voltage battery 100 and relatively small increase amount of terminal voltage of low-voltage battery 100 in comparison at the same magnitude of charge / discharge current. It becomes possible to raise the temperature of the low-voltage battery 100 safely in a relatively short time.

  Further, according to the first embodiment, since the low voltage battery 100 is a non-aqueous electrolyte secondary battery including a lithium ion battery, the electrolytic solution can be obtained by charging and discharging the capacitor 2 with each other at low temperature. It is possible to preferably prevent the deterioration of the discharge characteristics of the low voltage battery 100 due to the increase of the mobility of ions therein.

  Furthermore, according to the first embodiment, the battery 2 is an electric double layer capacitor, a lithium ion capacitor, or a lithium ion battery, and is excellent in rapid charge / discharge characteristics. Therefore, the voltage of the load group 200 due to a rapid change in load current. Fluctuation can be suitably prevented. Further, since the temperature of the capacitor or the lithium ion battery is also raised simultaneously when the low voltage battery 100 is heated, it is possible to prevent the deterioration of the charge and discharge characteristics.

  Furthermore, according to the first embodiment, charging / discharging of the low-voltage battery 100 is performed by charging / discharging the low-voltage battery 100 in a cycle represented by the reciprocal of the frequency at which the absolute value of the internal impedance is smaller than the minimum value by a predetermined value. Since the voltage fluctuation range of the low voltage battery 100 with respect to the size is relatively small, the deterioration of the low voltage battery 100 can be prevented.

  Furthermore, according to the first embodiment, the low voltage battery 100 is charged and discharged by charging and discharging the low voltage battery 100 in a cycle represented by the reciprocal of the frequency at which the absolute value of the imaginary component of the internal impedance is less than the second value close to zero. Among the charge and discharge currents, the current flowing to the real part of the internal impedance becomes relatively large to generate Joule heat, so the temperature of the low voltage battery 100 can be efficiently raised.

  Furthermore, according to the first embodiment, when the current waveform of charge and discharge is sinusoidal, since the harmonic components included in the charge and discharge current are relatively small, charge and discharge can be performed by appropriately selecting the charge and discharge cycle. The voltage fluctuation range of the low voltage battery 100 with respect to the magnitude of the current can be kept relatively small. In addition, when the current waveform of charge and discharge is a rectangular wave, the temperature increase effect of the low voltage battery 100 can be relatively increased by comparing at the same peak value of the charge and discharge current.

(Modification 1)
The first embodiment is a form in which the load group 200 is directly connected to the battery 2, whereas the first modification is a form in which the load group 200 is directly connected to the low-voltage battery 100. FIG. 7 is a block diagram illustrating a configuration example of the power supply system S1 according to the first modification. The power supply system S <b> 1 includes at least a battery 2 that temporarily stores power and a DC / DC converter 1 that converts the voltage of the battery 2 and supplies power to the low-voltage battery 100 and the load group 200. The DC / DC converter 1 is connected between the storage battery 2 and the low voltage battery 100, and converts voltage in both directions. The low voltage battery 100 may be included in the power supply system S1.

  The low voltage battery 100 is charged by the DC / DC converter 3 that reduces the voltage of the high voltage battery 300 when the battery voltage or the SOC decreases. The DC / DC converter 3 may be included in the power supply system S. The other connection configurations are the same as those shown in FIG. 1 of the first embodiment, and therefore, the portions corresponding to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the configuration according to the first modification, when the low voltage battery 100 is appropriately charged, the low voltage battery 100 steadily supplies the power supply voltage to the load group 200, whereby the operating power is supplied to the load group 200. . The DC / DC converter 3 may convert the voltage of the high voltage battery 300 to constantly supply the power supply voltage to the load group 200 and the low voltage battery 100, and the low voltage battery 100 may back up this. The DC / DC converter 1 converts the voltage of the low voltage battery 100 at appropriate times to charge the storage battery 2.

  When the load group 200 includes an inductive load, the DC / DC converter 1 converts the power supply voltage and charges the storage battery 2 when the power supply voltage rises sharply, thereby causing fluctuations in the power supply voltage. suppress. In addition, when the power supply voltage sharply drops, the DC / DC converter 1 converts the voltage of the storage battery 2 and supplies it to the load group 200, thereby suppressing the fluctuation of the power supply voltage. When the low voltage battery 100 breaks down, the storage battery 2 supplies operating power to the load group 200 for a certain period of time via the DC / DC converter 1.

  As described above, according to the first modification, since the load group 200 is directly connected to the low voltage battery 100, generation of loss in the power supplied from the low voltage battery 100 to the load group 200 is prevented. Can do.

  Further, according to the first embodiment and the first modification, the voltage of the high voltage battery 300 for driving the vehicle C is reduced by the DC / DC converter 3, and power is supplied to the low voltage battery 100. Therefore, when the SOC of the secondary battery decreases, the low voltage battery 100 can be charged by the high voltage battery 300, and power can be supplied to the load group 200.

  Further, according to the first embodiment and the first modification, the power supply systems S and S 1 further include the DC / DC converter 3 in addition to the storage battery 2, and manage them integrally with the DC / DC converter 1. can do.

(Modification 2)
In the first embodiment, the low-voltage battery 100 is charged with power from the high-voltage battery 300 via the DC / DC converters 3 and 1, whereas in the second modification, the low-voltage battery 100 is replaced with the DC / DC converter 1. , And is charged with the power from the on-vehicle alternator 400 (corresponding to the on-vehicle generator). FIG. 8 is a block diagram showing a configuration example of a power supply system S2 according to the second modification. The power supply system S2 includes at least a DC / DC converter 1 that converts the voltage of the low-voltage battery 100 and supplies electric power to the in-vehicle load group 200, and a capacitor 2 that is connected to the load group 200 and temporarily stores electric power. Prepare. The DC / DC converter 1 is connected between the low voltage battery 100 and the storage battery 2 and converts voltage bidirectionally. The low voltage battery 100 may be included in the power supply system S.

  Low voltage battery 100 is charged at any time by DC / DC converter 1 that converts a voltage generated by alternator 400 that generates electric power in conjunction with the engine of vehicle C. The vehicle C is not equipped with the DC / DC converter 3 and the high voltage battery 300. The other connection configurations are the same as those shown in FIG. 1 of the first embodiment, and therefore, the portions corresponding to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the configuration according to the second modification, when the alternator 400 is not generating power, the DC / DC converter 1 converts the voltage of the low-voltage battery 100 and supplies the power voltage to the load group 200 and the capacitor 2, whereby the load group The operating power is supplied to 200, and the battery 2 is charged to the power supply voltage. When the load group 200 includes an inductive load, the capacitor 2 suppresses the fluctuation of the power supply voltage when the power supply voltage rapidly changes within a short time. When the low voltage battery 100 or the DC / DC converter 1 fails, the storage battery 2 supplies operating power to the load group 200 for a certain period of time.

(Modification 3)
In the second modification, the low-voltage battery 100 is charged with power from the in-vehicle alternator 400 via the DC / DC converter 1, whereas in the third modification, the low-voltage battery 100 is charged with power from the alternator 400. It is a form charged directly. FIG. 9 is a block diagram illustrating a configuration example of the power supply system S3 according to the third modification. The power supply system S3 includes at least a DC / DC converter 1 that converts the voltage of the low-voltage battery 100 and supplies electric power to the in-vehicle load group 200, and a capacitor 2 that is connected to the load group 200 and temporarily stores electric power. Prepare. The DC / DC converter 1 is connected between the low voltage battery 100 and the storage battery 2 and converts voltage bidirectionally. The low voltage battery 100 may be included in the power supply system S.

  Low voltage battery 100 is charged at any time by the power generated by alternator 400 that generates power in conjunction with the engine of vehicle C. The vehicle C is not equipped with the DC / DC converter 3 and the high voltage battery 300. The other connection configurations are the same as those shown in FIG. 1 of the first embodiment, and therefore, the portions corresponding to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the configuration according to the third modification, when the alternator 400 is not generating power, the DC / DC converter 1 converts the voltage of the low-voltage battery 100 and supplies the power voltage to the load group 200 and the capacitor 2, whereby the load group The operating power is supplied to 200, and the battery 2 is charged to the power supply voltage. When the load group 200 includes an inductive load, when the power supply voltage suddenly fluctuates within a short time, the capacitor 2 suppresses fluctuations in the power supply voltage. When the low voltage battery 100 or the DC / DC converter 1 fails, the storage battery 2 supplies operating power to the load group 200 for a certain period of time.

  As described above, according to the third modification and the first embodiment and the second modification, since the load group 200 is directly connected to the capacitor 2, the capacitor 2 absorbs the rapid fluctuation of the load current without time delay. can do.

  Further, according to the first embodiment and the first to third modifications, the temperature of the storage battery 2 included in the power supply systems S and S1 to S3 can be raised simultaneously with the low voltage battery 100.

  Furthermore, according to the first embodiment and the first to third modifications, the power supply systems S and S1 to S3 further include the low voltage battery 100 in addition to the capacitor 2, and these are integrated with the DC / DC converter 1. Can be managed.

  Furthermore, according to Modifications 2 and 3, power is supplied from the alternator 400 to the low voltage battery 100. Therefore, when the SOC of the low voltage battery 100 is lowered, the low voltage battery 100 can be charged by the alternator 400, and power can be supplied to the load group 200.

  Furthermore, according to the first embodiment and the first to third modifications, since the power supply control unit 4 causes the DC / DC converter 1 to charge and discharge based on the temperature of the low voltage battery 100, the temperature of the low voltage battery 100 is lower than a predetermined temperature. When the temperature of the low-voltage battery 100 needs to be increased, the DC / DC converter 1 can charge and discharge the low-voltage battery 100 and the battery 2 with each other.

1, 3 DC / DC converter 2 capacitor 4 power supply control unit 41 temperature sensor 10 drive control unit 12 drive circuit 12 reference current waveform circuit 13 triangular wave generation circuit 14 amplifier 15 comparator 100 low voltage battery 200 load group 300 high voltage battery 400 alternators A, B Arm C Vehicle Q1, Q2, Q3, Q4 Transistor C11, C12 Capacitor L1 Inductor R11 Resistor Z1 Amplifier

Claims (15)

A DC / DC converter connected between a secondary battery mounted on a vehicle and a storage battery for temporarily storing power,
A DC / DC converter wherein the secondary battery and the capacitor are mutually charged and discharged in a predetermined cycle and with a predetermined current waveform.   The DC / DC converter according to claim 1, wherein the secondary battery is a non-aqueous electrolyte secondary battery including a lithium ion battery.   The DC / DC converter according to claim 1, wherein the capacitor includes an electric double layer capacitor, a lithium ion capacitor or a lithium ion battery.   The DC // DC converter according to any one of claims 1 to 3, wherein the cycle is a reciprocal of a frequency at which the absolute value of the internal impedance of the secondary battery is equal to or less than a value larger than the minimum value by a predetermined value. DC converter.   5. The DC / DC converter according to claim 4, wherein the period is a reciprocal of a frequency at which an absolute value of an imaginary component of the internal impedance is equal to or less than a second value.   The DC / DC converter according to any one of claims 1 to 5, wherein the current waveform is sinusoidal or rectangular.   The DC / DC converter according to any one of claims 1 to 6, wherein the capacitor is connected to a load of the vehicle.   The DC / DC converter according to any one of claims 1 to 6, wherein the secondary battery is connected to a load of the vehicle.   A power supply system comprising the DC / DC converter according to any one of claims 1 to 8 and the storage battery.   The power supply system according to claim 9, further comprising the secondary battery.   The power supply system according to claim 9, wherein the secondary battery is charged by a second DC / DC converter that steps down a voltage of a second secondary battery mounted in the vehicle.   The power supply system according to claim 11, further comprising the second DC / DC converter.   The power supply system according to claim 9 or 10, wherein the secondary battery is charged by an onboard generator that generates electric power in conjunction with an engine mounted on the vehicle.   The power supply control unit according to any one of claims 9 to 13, further comprising: a power supply control unit that causes the DC / DC converter to charge and discharge the secondary battery and the capacitor based on a detection result obtained from a detection unit that detects the temperature of the secondary battery. The power supply system described in the section. A method of charging and discharging the secondary battery with a DC / DC converter connected between a secondary battery mounted on a vehicle and a battery that temporarily stores electric power,
A method of charging and discharging a secondary battery, comprising the steps of: charging and discharging the secondary battery and the capacitor with each other at a predetermined cycle and with a predetermined current waveform.

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