Loss variable control device

Abstract

To inhibit battery degradation by rapidly eliminating a low-temperature state and a high-temperature state while inhibiting overcharge, regarding a battery mounted on a hybrid vehicle and an electric vehicle.SOLUTION: A circuit loss variable control device, which is a PWM circuit having an arithmetic unit 31, a driver 32 and a power element 33, is used for a power distribution unit 22 and a DC / DC converter 23. The circuit loss variable control device comprises a first circuit 36 that makes a circuit loss of the driver 32 relatively small in the above case, and a second circuit 37 that makes the circuit loss of the driver 32 larger than the first circuit 36. The circuit loss variable control device performs control so as to vary resistance by switching between the first circuit 36 and the second circuit 37 and expand the circuit loss.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the control of a PWM circuit mounted on an electric vehicle. [Background technology]

[0002] Hybrid vehicles, which combine a power generating device such as an engine-driven generator or a fuel cell with a battery, are commonly used as electric vehicles that can achieve both environmental friendliness and fuel efficiency. These hybrid vehicles are divided into two types: one in which the motor is driven primarily by power from the power generating device, and another in which the battery is first charged and then driven by power from the battery. In either type, the battery is generally charged with regenerative current, and the battery also serves as a receiver for the surplus power generated.

[0003] However, there is a limit to the amount of power a battery can absorb, and supplying current beyond a fully charged state will significantly deteriorate the battery. For this reason, a limit is set to prevent regenerative current from occurring when the battery's State of Charge (SOC) is high, and regeneration is controlled within that range.

[0004] Furthermore, batteries have the tendency to reduce output when their temperature becomes too high or too low. In order to warm the battery when the temperature is low, priority is given to series driving, which supplies power from the power generation device to the battery to warm it up while also driving using output from the battery. However, rapid cooling is difficult when the temperature is high, so methods are being considered to reduce battery input and output in order to prioritize heat dissipation and suppress heat generation (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-014820 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the method described in Patent Document 1 is intended to prevent heating during external power supply, and is not capable of adjusting the regenerative current generated during driving or the power from the power generation device.

[0007] Therefore, an object of the present invention is to prevent overcharging of batteries mounted on hybrid vehicles and electric vehicles, while quickly eliminating low-temperature and high-temperature conditions, thereby preventing battery deterioration. [Means for solving the problem]

[0008] This invention is A PWM circuit having a computing unit, a driver, and a power element, a first circuit in which the circuit loss of the driver is relatively small; a second circuit in which the circuit loss of the driver is greater than that of the first circuit, The above problem was solved by a first solution, which is a loss variable control device that executes a loss expansion control means that varies the resistance by switching between the first circuit and the second circuit, thereby controlling the circuit loss to expand.

[0009] Furthermore, the variable loss control device according to the present invention has the following features in addition to the first solution: A second solution can be adopted in which the resistance is made variable by changing the gate voltage through switching between the first circuit and the second circuit.

[0010] Furthermore, the variable loss control device according to the present invention has the following features in addition to the first or second solving means: A third solution can be adopted in which the resistance is variable by changing the amount of current flowing to the gate side by switching between the first circuit and the second circuit.

[0011] Further, the present invention provides an electric vehicle equipped with a variable loss control device according to any one of the first to third solving means, The PWM circuit is disposed in a power distribution unit between the motor and the drive battery, A fourth solution can be adopted in which, when the SOC of the drive battery is above a predetermined value, or when the temperature of the drive battery is in a high temperature state above a predetermined temperature, the first circuit and the second circuit are switched so that the resistance of the PWM circuit becomes high, thereby increasing circuit loss and controlling the regenerative current supplied to the drive battery to be suppressed.

[0012] Further, the present invention provides an electric vehicle equipped with a variable loss control device according to any one of the first to third solving means, The PWM circuit is disposed in a DC / DC converter between the drive battery and the 12V battery, A fifth solution can be adopted in which, when the temperature of the driving battery is in a low-temperature state below a predetermined temperature, the first circuit and the second circuit are switched so that the resistance of the PWM circuit becomes high, thereby increasing circuit loss and the amount of heat generated. [Effects of the Invention]

[0013] In typical electric vehicles, control is performed to minimize circuit loss and reduce energy loss. However, contrary to the conventional idea, this invention controls the circuit loss to increase it, thereby causing regenerative current to be lost in situations where the drive battery may be overcharged or overheated, or increasing circuit loss to warm the drive battery when it is too cooled. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a functional block diagram showing an embodiment of an electric vehicle according to the present invention. [Figure 2] A power distribution diagram showing an embodiment of an electric vehicle according to the present invention. [Figure 3] A map table for each individual situation for switching circuits according to the present invention [Figure 4]Graph showing the relationship between gate-source voltage and drain current [Figure 5] Graph showing the change in drain current when switching to increase circuit loss DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described with reference to a configuration diagram of an electric vehicle 10 shown in FIG. 1 and a power distribution diagram shown in FIG. The electric vehicle 10 according to the present invention is an electrically powered vehicle that can travel by driving a motor 21 to rotate the wheels. It may be a purely electric vehicle, or an electric vehicle with multiple power sources, such as a hybrid vehicle or a fuel cell vehicle. In the case of a hybrid vehicle, it may not only be charged by power generated by an engine, but may also be a plug-in hybrid vehicle (PHEV) that is equipped with an external charging system that allows power to be charged from an external source and an external power supply that allows power to be supplied to the outside. While FIG. 1 shows an example in which the motor 21 is driven primarily by power stored in a drive battery 24, the motor 21 may also be driven primarily by power generated by an engine or the like, and is not limited to this.

[0016] The electric vehicle 10 according to the present invention has a separate drive battery 24 and a 12V battery 27. The 12V battery 27 is a lead-acid battery that mainly supplies power used to start the engine and drive 12V components 28 and the control unit 25, which is an ECU. For convenience, it is called a 12V battery, but any battery of the same series, such as a 24V battery, can be used. On the other hand, the drive battery 24 is a separate system from the 12V battery 27 and is large enough to supply power to drive the motor 21; lithium-ion batteries, sodium-ion batteries, etc. can be used.

[0017] The electric vehicle 10 according to the present invention has a control unit 25 that executes each of the means described below for controlling the power supplied to the motor 21. The control unit 25 has a semiconductor arithmetic unit and a memory device, receives signals from sensors attached to each unit and transmitted data, receives operations from the driver, and sends instructions to each unit. Each of the means described below is realized as a function realized by executing a recorded program or as a function using a dedicated circuit. The control unit 25 is preferably implemented as an additional function by installing and executing a program that realizes the present invention in an ECU (Electronic Control Unit) installed in the electric vehicle 10 for driving control, rather than providing a separate arithmetic unit specifically for the means specified in this invention.

[0018] The electric vehicle 10 according to the present invention has high-voltage components that control the power supplied to the motor 21 and the 12V system components 28. In the example shown in the figure, the high-voltage components include a power distribution unit 22 that distributes the power supplied to the motor 21, and a DC / DC converter 23 that reduces the voltage to the 12V system.

[0019] The variable loss control device according to the present invention is used in these high-voltage components. The variable loss control device is a PWM (Pulse Width Modulation) circuit including a calculation device 31, a driver 32, and a power element 33. That is, the variable loss control device is capable of switching between a current-carrying state and a non-current-carrying state, and controls the average current output by adjusting the time ratio (duty ratio) of each state. The variable loss control device according to the present invention includes, for the driver 32, a first circuit 36 ​​having a relatively small circuit loss and a second circuit 37 having a relatively large circuit loss compared to the first circuit 36. An example of this circuit configuration is shown in FIG. 2. The calculation device 31 varies the resistance by switching between the first circuit 36 ​​and the second circuit 37, and executes a loss expansion control means that controls the circuit loss of the variable loss control device (power distribution unit 22, DC / DC converter 23) to expand under the following conditions:

[0020] The following are examples of situations in which control to increase circuit loss is effective: (State 1) The input current introduced is reduced when the battery (drive battery 24 / 12V battery 27) is close to full charge. (State 2) When the battery is cold, the output current from the battery is increased to warm it up. (State 3) When the battery is hot, the input current to the battery is reduced to promote cooling. Conversely, in situations that do not fall under these categories, that is, when the battery is within the appropriate capacity and temperature ranges, control is performed to reduce circuit loss by increasing the input current to the battery or reducing the output current, as is commonly done.

[0021] The problems associated with each of the above states and the effects of applying the present invention will be described below. <First state: Reduction of input current when the battery is nearly fully charged> When regenerative current is generated from the motor 21, it is supplied to the drive battery 24, as shown in FIG. 1, to charge the drive battery 24. This mainly occurs when the drive battery 24 (including the 12V battery 27) is nearly fully charged. If the drive battery 24 were to accept further regenerative current when nearly fully charged, it would be overcharged, accelerating battery capacity degradation. The same applies when distributing regenerative current to the 12V battery 27. For this reason, the introduction of regenerative current must be limited as much as possible when the battery is nearly fully charged. However, since regenerative current is also used as a brake without using the foot brake, disconnecting the motor 21 from the circuit would cause discomfort and inconvenience when operating the vehicle. Therefore, in this invention, by increasing the circuit loss of the power distribution unit 22 between the motor 21 and the drive battery 24 when the battery is nearly fully charged, the power consumed by the power distribution unit 22 can be increased, thereby reducing the power supplied to the drive battery 24. As such, the SOC threshold for avoiding charging when the SOC exceeds 95% and continues to rise continuously can be used to limit the power supplied. However, this threshold may be adjusted as appropriate depending on the type and capacity of the drive battery 24 .

[0022] <Second state: Increases the output current from the battery to warm the battery when powered at low battery temperature> The lithium-ion and sodium-ion batteries currently used in the drive battery 24 tend to increase their internal resistance at low temperatures. This tendency is evident in temperatures below 0°C and becomes even stronger at temperatures below -15°C. While the acceptable range of low temperatures depends on the battery type, the present invention is easily applicable if temperatures below -10°C are considered low, or temperatures below -15°C are considered even lower. As the battery's internal resistance increases, the power (current) that can be extracted from the battery decreases, resulting in a decrease in the output of the motor 21. Therefore, this invention increases the circuit loss in either or both of the power distribution unit 22 between the motor 21 and the drive battery 24 and the DC / DC converter 23 between the motor 21 and the 12V battery 27 during powering when the battery temperature is low. This increases the power consumed by the entire system, forcibly controlling the battery to extract the maximum amount of power that can be extracted. When the output power is forcibly increased, the battery heats up due to the increased output power in accordance with the internal resistance. As the battery warms up, it becomes easier to escape from the low-temperature state.

[0023] <Third state: Reduces the input current to the battery during regeneration when the battery is hot> Contrary to the second state, when the battery is hot, chemical reactions such as electrolyte decomposition within the battery are more likely to occur rapidly. Supplying regenerative input current to the battery in such a state accelerates the deterioration of the electrolyte and electrodes. For this reason, even if the battery is not nearly fully charged, the introduction of regenerative current must be limited as much as possible when the battery is hot. However, as mentioned above, preventing the generation of regenerative current itself would result in an uncomfortable operation. Therefore, in this invention, when the battery is hot, increasing the circuit loss of the power distribution unit 22 between the motor 21 and the drive battery 24 increases the power consumed by the power distribution unit 22 and reduces the power supplied to the drive battery 24. This prevents the battery from overheating and allows air or water cooling to prevail. The acceptable range of high temperatures at which cooling must be prioritized is 55°C or higher, depending on the type of battery used in the drive battery, and 60°C or higher is considered a high temperature limit.

[0024] <Other conditions> If neither of the above conditions is met, the power distribution unit 22 and DC / DC converter 23 are controlled to use the first circuit 36, which has relatively small circuit loss, to prevent circuit waste. Note that if the SOC is insufficient (for example, below 10%), it is generally recommended to prioritize charging. However, even if the SOC is insufficient, if the battery temperature is too high or too low, it is recommended to prioritize addressing the temperature.

[0025] Furthermore, in this invention, a third circuit and a fourth circuit, which have even greater circuit loss, may be provided in addition to the first circuit 36 ​​and the second circuit 37. When there is a need to further increase the circuit loss, it is preferable to be able to switch to these circuits and vary the resistance.

[0026] An example of a variable loss control device having three circuits with increasing circuit loss, namely a first circuit (circuit loss: low), a second circuit (circuit loss: medium), and a third circuit (circuit loss: high), will be described. The switching state according to the situation in an embodiment in which the variable loss control device is employed in each of the power distribution unit 22 and the DC / DC converter 23, will be described using FIG. 3. For the sake of brevity, the power distribution unit 22 will be referred to as "PDU" and the DC / DC converter 23 as "DCDC" in the figure. The states A to K and the targeted policies are as follows: (A·L) Battery temperature is at its lowest or highest, so you want to prevent the battery from being used. (B) I want to prevent the battery temperature from rising as much as possible and also want to prevent it from exceeding its capacity. (C) I want to prevent the battery temperature from rising as much as possible. (D) I want to prevent the battery temperature from rising as much as possible and increase the capacity. (E) I want to prevent overcapacity as much as possible. (F) I want to prevent exceeding capacity (G) Normal operation (H) I want to raise the battery temperature as much as possible and prevent capacity loss as much as possible. (I) I want to actively raise the battery temperature (J) I want to actively raise the battery temperature, but I want to avoid exceeding the capacity as much as possible. (K) I want to set the battery temperature to increase aggressively, but I can't set it to high loss because there is no energy.

[0027] (State A) When the battery temperature is at its highest (above a predetermined value within the allowable range), circuit loss is reduced during power running regardless of the battery capacity. This is because it is necessary to minimize power consumption and prevent the battery from overheating as much as possible. On the other hand, during regeneration, circuit loss in the power distribution unit 22 (PDU) is increased to increase power consumption as much as possible and consume the regenerative current supplied to the battery. (State B) When the battery temperature is high and near its maximum (close to the limit of the allowable range), the tendency is basically similar to state A. However, when the battery capacity is at or near its upper limit, the circuit loss in DC / DC converter 23 is slightly increased (circuit loss: medium) to prevent the battery from exceeding capacity, both during power running and regeneration, and the power supplied to the battery is suppressed as much as possible. (State C) When the battery temperature is high and near its maximum, and the battery capacity is within the appropriate range, the main control is basically to suppress the battery temperature. During power running, small circuit loss is acceptable, but during regeneration, the circuit loss of the power distribution unit 22 is increased. (State D) When the battery temperature is near its maximum and the battery capacity is near its minimum or has reached the minimum allowable limit, the circuit loss during regeneration is increased to a slightly higher "medium" setting rather than the highest "high" setting, to prevent the battery temperature from rising while still placing some importance on battery charging. (State E) If the battery temperature is within the allowed operating temperature range and the battery capacity is close to the upper limit, the circuit loss is set to "medium" rather than "high," and power consumption in the circuit is increased to prevent the tendency toward exceeding capacity. (State F) If the battery temperature is within the allowable operating temperature range and the battery capacity has reached its upper limit, both the power distribution unit 22 and the DC / DC converter 23 set the circuit loss to "high" to maximize the power consumption in the circuit and prevent overcapacity. This also prevents overcapacity when the battery temperature is near the lowest limit (close to the allowable range limit). (State G) When the battery temperature is within the allowed operating temperature range and the battery capacity is adequate or low, the circuit loss is set to "low." This is the original default state. (State H) When the battery temperature is low and near the lowest point (close to the limit of the allowable range) and the battery capacity is near the lower limit, the circuit loss is set to "low" during regeneration to prevent a decrease in the capacity of the drive battery 24. During power running, the circuit loss is switched to "medium" to warm the battery. Meanwhile, the DC / DC converter 23 prioritizes warming by setting the circuit loss to "medium." (State I) When the battery temperature is low and near the minimum (close to the limit of the allowable range) and the battery capacity is within the appropriate range, the DC / DC converter 23 sets the circuit loss to "high" to prioritize heating. During power running, the power distribution unit 22 also sets the circuit loss to "high" to prioritize heating. (State J) When the battery temperature is low and near the minimum (close to the limit of the tolerance range) and the battery capacity is near the upper limit, the circuit loss is set to "medium" or "high" to raise the temperature and prevent the tendency toward exceeding the capacity. (State K) When the battery temperature is low and near the minimum (close to the limit of the allowable range) and the battery capacity has reached the lower limit of the allowable range, it is desirable to increase power consumption to raise the battery temperature, but since the capacity is insufficient, the circuit loss is set to "low" in both cases. (State L) When the battery temperature is at its lowest (below a predetermined value within the allowable range), the internal resistance of the drive battery 24 becomes too high. For this reason, the circuit loss is lowered to reduce the load during power running, and the circuit loss is set to "high" during power running to prevent unexpected chemical changes from occurring during charging.

[0028] The above map is an example, and it is advisable to add more stages and execute a loss increase control means for controlling the circuit loss to increase appropriately as needed.

[0029] To grasp each of these conditions, the control unit 25 constantly monitors the charge state and battery temperature of the drive battery 24. Although not shown in Fig. 1, if the control unit 25 also monitors the charge state and battery temperature of the 12V battery 27, it will be able to provide control that is more suited to the situation. Based on the monitored battery conditions, the control unit 25 controls the circuit loss to increase when necessary.

[0030] The configuration and operation of the variable loss control device shown in FIG. 2, which switches between a first circuit 36 ​​and a second circuit 37 that increase the circuit loss, will be described below. This corresponds to the internal configuration of the power distribution unit 22 or the DC / DC converter 23. This variable loss control device has a calculation device 31, a driver 32, and a power element 33. The calculation device 31 can employ a CPU (Central Processing Unit) or a DSP (Digital Signal Processor) that switches between circuits. The driver 32 is provided with a first circuit 36 ​​and a second circuit 37, which have different circuit losses, and the calculation device 31 can switch which one to use. Both the first circuit 36 ​​and the second circuit 37 have semiconductors, and are circuits that can apply voltages from power sources 1 and 2, which have different voltages, to the gate G of the power element 33. In this example, the R that constitutes the first circuit 36 ​​and the second circuit 37 11 and R 21 , R 12 and R 22 are the same resistances, and the transistors that make up n1 and TR n2 , T.R. p1 and TR p2 However, the second circuit 37 includes the resistor R 23 is added, and the voltage of power supply 2 is lower than that of power supply 1. This resistor R 23 Therefore, the circuit resistance of the second circuit 37 is higher than that of the first circuit 36. Furthermore, the voltage applied to the gate G of the power element 33 is also higher in the second circuit 37. The difference in voltage between the power source 1 and the power source 2 can be achieved by, but is not limited to, boosting the voltage from the 12V battery 27 via a boost circuit to achieve the specified voltage.

[0031] Here, an N-channel MOSFET is used as the power element 33. The drain current that flows from the drain (D) to the source (S) increases depending on the gate (G) voltage. When using a conventional MOSFET, the relationship between the gate-source voltage and the drain current tends to be as shown in Figure 4. For this reason, it is common to control the circuit loss by increasing the gate-source voltage to increase the drain current. However, in this invention, the gate-source voltage is reduced, and control is performed to increase the circuit loss (resistance), thereby achieving the control shown in the map in Figure 3.

[0032] As a control to increase the circuit loss, in addition to the first control (1) that switches between the first circuit 36 ​​and the second circuit 37 to lower the voltage between the gate (G) and the source (S) as described above, a second control (2) that slows the rate of change between ON and OFF between the gate (G) and the source (S) can also be employed, or these can be combined. Figure 5 shows a graph of the amount of current when switching ON and OFF over time. By performing the first control (1), the maximum value of the amount of current becomes smaller (α → β), and by performing the second control (2), the slope of the rise from OFF to ON becomes smaller.

[0033] Specifically, the lower the gate voltage, the higher the resistance becomes due to the first control (1), reducing the current flowing between the drain (D) and source (S), and increasing circuit loss. This first control (1) can be realized by preparing multiple power supplies with different voltages, such as power supply 1 and power supply 2, and switching between them. As for the second control (2), since there is a parasitic capacitor called input capacitance at the gate (G) terminal, the speed at which the resistance changes from a high state to a low state can be changed by controlling the amount of current charged to this. In other words, if the charge is slower, the high resistance state will last longer, which can increase circuit loss. In this way, the second control (2) controls R 23 This can be achieved by preparing multiple circuits with different resistances and switching between them.

[0034] Combining these factors makes the area of ​​the trapezoid, which corresponds to the total amount of power, which is the magnitude of the amount of current flowing over time, sufficiently small. This area corresponds to the amount of power stored in one ON / OFF. A smaller amount of current means that the circuit loss as a whole has increased. As a PWM circuit, if the circuit loss increases and the drain current decreases, it becomes more difficult to store power, so the switching speed is controlled to increase accordingly.

[0035] The ON / OFF of the entire circuit is controlled by switching between the first circuit 36 ​​and the second circuit 37. When a drain current flows, power accumulates in the coil L1, and when the drain current stops, power flows from the coil L1 and accumulates in the capacitor C1. In terms of implementation, this variable circuit loss control device can be used in parallel instead of one, with three of them connected, and a PWM circuit that controls ON / OFF can be used as a circuit corresponding to each one. [Explanation of symbols]

[0036] 1, 2 Power supply 10. Electric Vehicles 21 Motor 22 Power Distribution Unit 23 DC / DC converter 24 Drive battery 25 Control Unit 27 12V battery 28 12V Components 31 Arithmetic unit 32 Drivers 33 Power Elements 36 First circuit 37 Second circuit R 11 ,R 12 ,R 21 ,R 22 ,R 23 resistance L1 coil C1 capacitor TR n1 , T.R. n2 , T.R. p1 , T.R. p2 transistor

Claims

1. A PWM circuit having a computing device, a driver, and a power element, a first circuit in which the circuit loss of the driver is relatively small; a second circuit in which the circuit loss of the driver is greater than that of the first circuit, A loss variable control device that executes loss enlargement control means for varying resistance by switching between the first circuit and the second circuit, thereby controlling so as to enlarge circuit loss.

2. The variable loss control device according to claim 1 , wherein the resistance is varied by changing a gate voltage through switching between the first circuit and the second circuit.

3. The variable loss control device according to claim 1 , wherein the resistance is varied by changing the amount of current flowing to the gate side by switching between the first circuit and the second circuit.

4. An electric vehicle equipped with the variable loss control device according to any one of claims 1 to 3, The PWM circuit is disposed in a power distribution unit between the motor and the drive battery, When the SOC of the drive battery is equal to or higher than a predetermined value, or when the temperature of the drive battery is equal to or higher than a predetermined temperature and in a high temperature state, the first circuit and the second circuit are switched so that the resistance of the PWM circuit is high, thereby increasing circuit loss and controlling the regenerative current supplied to the drive battery to be suppressed.

5. An electric vehicle equipped with the variable loss control device according to any one of claims 1 to 3, The PWM circuit is disposed in a DC / DC converter between the drive battery and the 12V battery, When the temperature of the drive battery is in a low-temperature state where it is equal to or lower than a predetermined temperature, the first circuit and the second circuit are switched so that the resistance of the PWM circuit is high, thereby increasing circuit loss and the amount of heat generated.

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