JP2011167001A - Power supply apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase storage capacity that can be used in a power supply apparatus. <P>SOLUTION: An alternator 16 is connected in series to a main battery 25 connected to an electrical component 23. A sub-battery 26 connected to the electrical component 23 is arranged in parallel to the main battery 25 and the alternator 16. The alternator 16 and the main battery 25 are connected in series, so that the main battery 25 can be discharged deeply without being restricted by low limit voltage of the sub-battery 26 and the electrical component 23. The storage capacity which the main battery 25 has can sufficiently be used, thereby increasing the storage capacity that can be used in the power supply apparatus 10. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a power supply device that supplies electric power to an electric load.

  In conventional vehicles, it is common to supply electric power to electrical components using lead-acid batteries. Although this lead storage battery can secure a large storage capacity, it has been difficult to charge and discharge with a large current. Therefore, it is conceivable to employ a lithium ion battery or the like having a high output density as the power storage unit mounted on the vehicle. However, adopting a lithium ion battery has been a factor in increasing the cost of the power storage unit. That is, the power storage unit mounted on the vehicle is required to have a storage capacity that can sufficiently drive the starter motor after leaving the vehicle for a predetermined period (for example, three months). However, since the cost per capacity of the lithium ion battery is high, it has been difficult to avoid increasing the cost of the power storage unit in order to secure the necessary power storage capacity. In order to solve this problem, a power supply device has been proposed in which a lithium ion battery having a small charging resistance and a lead storage battery for securing a storage capacity are combined (for example, see Patent Document 1).

JP 2004-225649 A

  However, when different power storage bodies are combined, such as a lead storage battery and a lithium ion battery, there is a problem that the storage capacity that can actually be used decreases because the respective operating voltage ranges are different. In other words, the operating voltage range of a lithium ion battery is wider than the operating voltage range of a lead-acid battery, so it is necessary to match the operating voltage range of the lithium-ion battery to the lead-acid battery in order to avoid excessive deterioration of the lead-acid battery. was there. Thereby, since the operating voltage range of the lithium ion battery is narrowed, it has been impossible to fully utilize the storage capacity of the lithium ion battery. Moreover, in order to ensure the operating voltage range of a lithium ion battery, installing a DC / DC converter between a lithium ion battery and a lead acid battery is also considered. However, the use of a DC / DC converter has been a factor in increasing the cost and size of the power supply device.

  An object of the present invention is to increase the storage capacity that can be used in a power supply device.

  A power supply device according to the present invention is provided in parallel with a first power storage unit connected to an electric load, power supply means connected in series to the first power storage unit, and the first power storage unit and the power supply unit. A second power storage unit connected to the electrical load, a first power supply path that bypasses the first power storage unit and connects the power supply means and the electrical load, and passes through the first power storage unit. A second power feed path connecting the power supply means and the electrical load; a first switch provided in the first power feed path; switched between a connected state and an open state; and provided in the second power feed path; And a second switch that is switched between a connected state and an open state.

  In the power supply device of the present invention, the second switch is provided on the negative electrode side of the first power storage unit, and a ground path that grounds a connection point between the second switch and the first power storage unit is connected and opened. A third switch that can be switched to is provided.

  The power supply device according to the present invention is characterized in that a lower limit voltage of the first power storage unit is set lower than a lower limit voltage of the second power storage unit or the electric load.

  The power supply device according to the present invention is characterized in that a full charge voltage of the first power storage unit is set to be equal to or higher than an upper limit voltage of the second power storage unit.

  According to the present invention, since the first power storage unit and the power supply means are connected in series, the first power storage unit is deeply discharged without being restricted by the lower limit voltage of the second power storage unit or the electric load. It becomes possible. This makes it possible to increase the storage capacity that can be used in the power supply device.

It is the schematic which shows the vehicle provided with the power supply device which is one embodiment of this invention. It is explanatory drawing which shows the control state of a switch. (a) And (b) is explanatory drawing which shows the electric power supply state of a power supply device. It is explanatory drawing which shows the electric power supply state of a power supply device. It is a diagram which shows the charging / discharging characteristic of a main battery and a sub battery. It is explanatory drawing which shows the electric power supply state of the power supply device at the time of engine starting. It is the schematic which shows the household power supply system with which a power supply device is applied.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing a vehicle 11 including a power supply device 10 according to an embodiment of the present invention. As shown in FIG. 1, an engine 12 and a transmission 13 are mounted on the vehicle 11. Drive wheels are connected to the output shaft 14 of the transmission 13 via a differential mechanism (not shown). Further, a starter motor 15 is assembled to the engine 12. Further, an alternator 16 serving as power supply means is connected to the engine 12 via a drive belt 17. Furthermore, the vehicle 11 is equipped with electrical components 23 such as a headlight 20, an ignition coil 21, and an electronic control unit 22 as electrical loads.

  The illustrated vehicle 11 is a so-called micro-hybrid vehicle, and the vehicle 11 is mounted with a low-voltage regenerative system using an alternator 16. At the time of deceleration at which the accelerator pedal is released, the alternator 16 is driven to generate electricity, so that the kinetic energy of the vehicle 11 is positively converted into electric energy and recovered. During acceleration when the accelerator pedal is depressed or during steady running, power generation by the alternator 16 is stopped to reduce the engine load. Thus, the fuel efficiency of the vehicle 11 is improved by controlling the alternator 16 so as not to increase the engine load.

  By the way, in order to improve the fuel efficiency of the vehicle, it is important to increase the regeneration amount (power generation amount) of the alternator during deceleration. However, in a vehicle including only a lead storage battery as a power storage unit as in the past, the charging current is limited by the lead storage battery, and thus it is difficult to increase the amount of regeneration of the alternator. In order to solve this problem, it is conceivable to employ a lithium ion battery or the like having a small charging resistance as the power storage unit. That is, the power storage unit mounted on the vehicle is required to have a storage capacity that can sufficiently drive the starter motor after leaving the vehicle for a predetermined period (for example, three months). However, since the cost per capacity of the lithium ion battery is high, the cost of the power storage unit has been increased in order to ensure the necessary power storage capacity.

  Therefore, as shown in FIG. 1, the power supply device 10 includes a main battery (first power storage body) 25 made of a lithium ion battery or the like having a small charging resistance, and a lead storage battery or the like that can secure a storage capacity at low cost. A sub-battery (second power storage unit) 26 is provided. However, it is difficult to fully utilize the storage capacity of a lithium ion battery simply by connecting a lithium ion battery and a lead storage battery in parallel. That is, since the lead storage battery is greatly deteriorated by deep charge / discharge, it is necessary to control it to a predetermined lower limit voltage (for example, 12.8 V) or more. On the other hand, the lithium ion battery can be discharged deeper than the lead acid battery. However, in order to avoid overdischarge of the lead acid battery, the lithium ion battery also has a voltage equal to or higher than a predetermined lower limit voltage (for example, 12.8 V). Needed to hold. That is, since the use voltage range of the main battery 25 is limited, it is difficult to fully utilize the storage capacity of the main battery 25. Therefore, the power supply device 10 according to one embodiment of the present invention is configured as follows in order to fully utilize the storage capacity of the main battery 25.

  Hereinafter, the structure of the power supply device 10 which is one embodiment of this invention is demonstrated. As shown in FIG. 1, the alternator 16 and the electrical component 23 are connected via a feed line 27. The power supply line 27 functions as a first power supply path that bypasses the main battery 25 and connects the alternator 16 and the electrical component 23. The power supply line 27 is provided with a first switch SW1 such as an n-channel FET. The switch SW1 can be switched between a connected state (ON) and an open state (OFF).

  A positive line 28 connected to the positive terminal of the main battery 25 is connected to the electrical component 23. Further, the negative line 29 connected to the negative terminal of the main battery 25 is connected to the plus terminal of the alternator 16. Thus, the main battery 25 and the alternator 16 are connected in series. That is, the positive electrode line 28 and the negative electrode line 29 connected to the main battery 25 function as a second power supply path that connects the alternator 16 and the electrical component 23 via the main battery 25.

  The negative line 29 is provided with a second switch SW2 such as an n-channel FET. The switch SW2 can be switched between a connected state (ON) and an open state (OFF). Further, a ground line 30 is connected to the negative electrode line 29 between the switch SW2 and the main battery 25. Thus, the connection point 31 between the switch SW2 and the main battery 25 is grounded by the ground line 30 as a ground path. The ground line 30 is provided with a third switch SW3 such as an n-channel FET. The switch SW3 can be switched between a connected state (ON) and an open state (OFF).

  Further, a positive line 32 connected to the electrical component 23 is connected to the positive terminal of the sub battery 26. Further, a negative electrode line 33 is connected to the negative terminal of the sub-battery 26, and the negative electrode line 33 is grounded. As described above, the sub battery 26 is connected in parallel to the main battery 25 and the alternator 16.

  As the main battery 25, a power storage unit having a small charge / discharge resistance and excellent cycle characteristics is used. Examples of such a power storage unit include so-called rocking chair type power storage units such as a lithium ion battery, a lithium ion capacitor, an electric double layer capacitor, and a nickel metal hydride battery. Here, the rocking chair type power storage unit refers to a power storage unit that performs charging and discharging by reciprocating lithium ions, hydrogen ions, and the like between electrodes. The power storage mechanism of the rocking chair type power storage unit has the characteristics that the charge / discharge resistance is small and the cycle characteristics are excellent because the physical structure change (dissolution / precipitation) of the electrode is not involved.

  As the sub battery 26, a power storage unit having a predetermined power storage capacity is used. The storage capacity of the sub-battery 26 is set in consideration of the starting performance after leaving the vehicle for a predetermined period. Examples of such a power storage unit include a so-called reserve power storage unit such as a lead storage battery having a low storage cost and a large storage capacity. Here, the reserve type power storage unit refers to a power storage unit that performs charge / discharge by dissolving ions in the electrolytic solution from the metal or the like of the electrode and precipitating the ions in the electrolytic solution on the electrode as metal or the like. The power storage mechanism of the reserve power storage unit involves changes in the physical structure (dissolution / deposition) of the electrode, so the charge / discharge resistance is large and the cycle characteristics are poor compared to the rocking chair type power storage unit. Therefore, it has a characteristic that it is easy to obtain a large storage capacity at low cost. The sub-battery 26 is not limited to the reserve type power storage unit, and a rocking chair type power storage unit may be used as the sub-battery 26 as long as a predetermined power storage capacity can be secured at low cost.

  In order to execute the switching control of the switches SW1 to SW3 described above, the power supply device 10 is provided with a power supply control unit (switch control means) 34. The power supply control unit 34 includes a CPU that executes a program, a ROM that stores a program, a RAM that temporarily stores data, an input / output port connected to various sensors, actuators, and the like. The sensors connected to the power supply control unit 34 include an accelerator opening sensor 35 that detects the operation state of the accelerator pedal, a vehicle speed sensor 36 that detects the vehicle speed, a voltage sensor 37 that detects the voltage of the alternator 16, and a voltage of the main battery 25. Voltage sensor 38 for detecting the current, current sensor 39 for detecting the current of the main battery 25, temperature sensor 40 for detecting the temperature of the main battery 25, voltage sensor 41 for detecting the voltage of the sub battery 26, and detecting the current of the sub battery 26 Current sensor 42 or the like.

  Next, switching control of the switches SW1 to SW3 by the power supply control unit 34 will be described. FIG. 2 is an explanatory diagram showing a control state of the switches SW1 to SW3. FIGS. 3A and 3B are explanatory diagrams showing the power supply state of the power supply device 10. FIG. 3 shows a state during acceleration of the vehicle where the accelerator pedal is depressed or during steady running. Further, FIG. 4 is an explanatory diagram showing a power supply state of the power supply device 10. FIG. 4 shows a state during deceleration of the vehicle in which the accelerator pedal is released. In FIG. 3 and FIG. 4, the power supply state is represented using black arrows.

  First, as shown in FIG. 2, the voltage applied to the electrical component 23 and the sub-battery 26 is controlled between a predetermined upper limit voltage Vmax and a lower limit voltage Vmin. The upper limit voltage Vmax is set to 14.4 V, for example, based on the upper limit voltage of the electrical component 23 and the sub battery 26. The lower limit voltage Vmin is set to 12.8 V, for example, based on the lower limit voltage of the electrical component 23 and the sub battery 26. That is, by controlling the applied voltage within a voltage range R (for example, 12.8 V to 14.4 V) set by the upper and lower limit voltages Vmax and Vmin, the electrical component 23 operates normally and the sub-battery 26 is overdischarged. Can be prevented. Further, the lower limit voltage V1 shown in FIG. 2 is a lower limit voltage of the main battery 25, and the main battery 25 can be discharged to be used up to the lower limit voltage V1.

  As shown in FIG. 2 and FIG. 3 (a), when the accelerator pedal is depressed (accelerator ON) with the terminal voltage of the main battery 25 exceeding the lower limit voltage V1, the switch SW2 is connected. The switches SW1 and SW3 are switched to the open state. Further, the power supply control unit 34 controls the generated voltage of the alternator 16 based on the terminal voltage of the main battery 25 so that the applied voltage is maintained in the voltage range R. That is, since the main battery 25 and the alternator 16 are connected in series by switch control, a voltage obtained by adding the power generation voltage of the alternator 16 and the terminal voltage of the main battery 25 is the applied voltage. Then, the power generation voltage of the alternator 16 is gradually increased so as to compensate for the voltage drop of the main battery 25 due to discharge. Thereby, the main battery 25 can be discharged to a region below the lower limit voltage Vmin while keeping the applied voltage in the voltage range R.

  2, when the terminal voltage of the main battery 25 reaches the lower limit voltage V1 due to discharge, the switch SW1 is switched to the connected state as shown in FIG. The switch SW2 is switched to the open state. Note that the switch SW3 is held open. 2, the generated voltage of the alternator 16 is raised to a predetermined target value within the voltage range R. Accordingly, the main battery 25 can be disconnected from the power supply device 10 while keeping the applied voltage in the voltage range R, and overdischarge of the main battery 25 can be prevented.

  As shown in FIGS. 2 and 4, when the accelerator pedal is released (accelerator OFF), the switch SW3 is switched to the connected state. Note that the switch SW1 is held in the connected state, and the switch SW2 is held in the open state. Further, the power supply control unit 34 sets a target generated current (for example, 200 A) of the alternator 16 according to the vehicle speed, and the alternator 16 adjusts the generated voltage within the voltage range R so that the target generated current can be obtained. Thereby, the electric power generated by the alternator 16 is supplied to the main battery 25 and the sub battery 26. In the case shown in FIG. 2, since the open voltage of the main battery 25 increases according to the state of charge, the generated voltage is increased so as to obtain a desired target generated current.

  As described above, since the alternator 16 and the main battery 25 are connected in series, the main battery 25 is moved to the lower limit voltage V1 without being limited by the lower limit voltage Vmin of the sub battery 26 or the electrical component 23. It becomes possible to discharge deeply. Here, FIG. 5 is a diagram showing charge / discharge characteristics of the main battery 25 and the sub-battery 26. As shown in FIG. 5, when the discharge of the main battery 25 is stopped at the lower limit voltage Vmin, the main battery 25 is used within the range of the state of charge SOC indicated by the symbol α. On the other hand, when discharging of the main battery 25 is continued up to the lower limit voltage V1, the main battery 25 can be used in the range of the state of charge SOC indicated by the symbol β. As described above, since the power storage capacity of the main battery 25 can be fully utilized, the power storage capacity that can be used in the power supply device 10 can be increased.

  Further, as indicated by a symbol A in FIG. 5, the terminal voltage (full charge voltage) in the fully charged state of the main battery 25 is set to be equal to or higher than the upper limit voltage Vmax of the sub battery 26. Thereby, even if it is a case where it charges to Vmax which is the upper limit voltage of the electrical component 23 or the sub battery 26, it becomes possible to prevent the overcharge of the main battery 25. In this way, since overcharging of the main battery 25 is reliably prevented, it is possible to achieve simplification of charging control of the main battery 25.

  Further, since the alternator 16 and the main battery 25 are connected in series, the voltage applied to the electrical component 23 can be stabilized by controlling the power generation voltage of the alternator 16. Furthermore, since the main battery 25 is configured by a rocking chair type power storage unit having a small charging resistance, it is possible to take in electric power with a large current (for example, 200 A) during deceleration. As described above, the main battery 25 can be sufficiently charged during deceleration, so that the alternator 16 can be stopped during acceleration or steady running. As a result, the engine load can be reduced and the fuel efficiency of the vehicle 11 can be improved. Further, by stopping the alternator 16 during acceleration, it is possible to suppress the engine load and improve the acceleration performance of the vehicle 11.

  In addition, the main battery 25 and the sub battery 26 are connected to the electrical component 23, but the SOC width (Vmax to V1) of the main battery 25 compared to the SOC width (Vmax to Vmin) of the sub battery 26 in the voltage range R. Is largely set by series connection with the alternator 16. Thereby, the main battery 25 can be charged / discharged mainly, and charging / discharging of the sub battery 26 can be suppressed. Therefore, even when a reserve power storage unit that deteriorates due to frequent charging and discharging is adopted for the sub-battery 26, it is possible to suppress the deterioration of the sub-battery 26. Moreover, by controlling the power generation voltage of the alternator 16, the applied voltage is kept within the predetermined voltage range R, so that charging / discharging of the sub-battery 26 can be suppressed to an extremely low level. In addition, since the cycle characteristics of the main battery 25 made of the rocking chair type power storage unit are good, the main battery 25 does not deteriorate significantly even if it is charged and discharged frequently.

  Further, as described above, since almost all the storage capacity of the main battery 25 can be utilized, the storage capacity of the main battery 25 made of a lithium ion battery or the like can be designed to be small. As a result, the main battery 25 can be reduced in size and cost. Further, the sub-battery 26 provided for backup can reduce the storage capacity as compared with the conventional battery. As a result, the sub battery 26 can be reduced in size and cost. Further, since the main battery 25 and the sub-battery 26 can be reduced in size, even when the main battery 25 and the sub-battery 26 are combined, the size of the main battery 25 and the sub-battery 26 can be suppressed to be equal to that of the conventional battery. It becomes possible. That is, the power supply device 10 can be mounted in the engine room as in the case of a conventional vehicle that includes only a lead storage battery. As a result, the power supply device 10 of the present invention can be mounted without significantly changing the vehicle body structure.

  Next, the power supply state of the power supply device 10 when the engine is started will be described. FIG. 6 is an explanatory diagram showing a power supply state of the power supply device 10 when the engine is started. As shown in FIG. 6, when the engine is started, the switches SW1 and SW2 are switched to the open state, and the switch SW3 is switched to the connected state. Thereby, it is possible to supply power from both the main battery 25 and the sub battery 26 to the starter motor 15 and the electrical component 23. Thus, since a large current can be supplied to the starter motor 15, for example, the startability of the engine 12 can be kept good even in a low temperature environment. In addition, since the sub-battery 26 having a predetermined storage capacity is provided, it is possible to maintain good starting performance after leaving the vehicle for a predetermined period. As the sub-battery 26, it is possible to suppress an increase in the cost of the power supply device 10 by using a reserve power storage unit such as a lead storage battery having a large storage capacity at a low cost.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, although the power supply device 10 of the present invention is applied to the vehicle 11, the present invention is not limited to the vehicle, and the power supply device 10 of the present invention may be applied to other devices. Here, FIG. 7 is a schematic diagram showing a household power supply system 50 to which the power supply apparatus 10 is applied. In FIG. 7, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. As shown in FIG. 7, in the household power supply system 50, a power generation system (power supply means) 53 including a solar cell 51 and a DC / DC converter 52, and a power supply system including a commercial power supply 54 and an AC / DC converter 55 ( Power supply means) 56. Then, an indoor electric load (electric load) 57 is connected to the power generation system 53 and the power supply system 56 via the power supply device 10. The main battery 25 is installed for daily charge and discharge, and the sub-battery 26 is installed for backup during disasters. In this household power supply system 50, by adjusting the output voltage of the power generation system 53 and the power supply system 56 according to the terminal voltage of the main battery 25, a DC / DC converter is not installed on the indoor electric load 57 side. The applied voltage to the indoor electrical load 57 can be kept substantially constant. As a result, the main battery 25 can be deeply discharged during daily charging and discharging, and the storage capacity of the main battery 25 can be fully utilized. Note that the power generation system 53 is used to effectively use sunlight during the day, but the power supply apparatus 10 of the present invention can also be effectively used for a home power supply system including only the power supply system 56. Is possible.

10 Power supply 15 Starter motor (electrical equipment, electric load)
16 Alternator (Power supply means)
20 Headlight (electric load)
21 Ignition coil (electric load)
22 Electronic control unit (electric load)
23 Electrical components (electric load)
25 Main battery (first battery)
26 Sub-battery (second power storage unit)
27 Feeding line (first feeding path)
28 Positive line (second feed path)
29 Negative electrode line (second feed path)
30 Grounding line (grounding path)
31 connection point 53 power generation system (power supply means)
56 Power supply system (power supply means)
57 Indoor electric load (electric load)
SW1 First switch SW2 Second switch SW3 Third switch Vmax Upper limit voltage Vmin Lower limit voltage V1 Lower limit voltage

Claims (4)

A first power storage unit connected to an electrical load;
Power supply means connected in series to the first power storage unit;
A second power storage unit provided in parallel with the first power storage unit and the power supply means and connected to the electrical load;
A first feeding path that bypasses the first power storage unit and connects the power supply means and the electric load;
A second feeding path that passes through the first power storage unit and connects the power supply means and the electrical load;
A first switch provided in the first power supply path and switched between a connected state and an open state;
A power supply apparatus comprising: a second switch provided in the second power supply path and switched between a connected state and an open state. The power supply device according to claim 1, wherein
The second switch is provided on the negative electrode side of the first power storage unit,
A power supply apparatus, wherein a third switch that is switched between a connected state and an open state is provided on a ground path that grounds a connection point between the second switch and the first power storage unit. The power supply device according to claim 1 or 2,
The lower limit voltage of the first power storage unit is set lower than the lower limit voltage of the second power storage unit or the electric load. The power supply device according to any one of claims 1 to 3,
The full charge voltage of said 1st electrical storage body is set more than the upper limit voltage of said 2nd electrical storage body, The power supply device characterized by the above-mentioned.

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