Vehicle Power System

Abstract

To provide a power supply system for a vehicle, which supports an idling stop function and has a function as a backup power supply.SOLUTION: A power supply system for a vehicle 1 comprises: a DC power supply 2 which is mounted on a vehicle and supplies power to one or a plurality of loads; a first switching element Q1 which is connected in series between the DC power supply 2 and the load 21: a power storage part 3 which is electrically connected to the DC power supply 2; and a DC-DC converter 4 which is connected between the power storage part 3 and the first switching element Q1. The DC-DC converter comprises: a second switching element Q2; a third switching element Q3; a fourth switching element Q4; a fifth switching element Q5; and a coil 6.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power supply system to be mounted on a vehicle, and more particularly to a power supply system for a vehicle equipped with an idling stop function, which is adapted to a drop in battery voltage when the engine is restarted and can also function as a backup power supply in the event of a power loss. [Background technology]

[0002] In recent years, vehicles equipped with an idling stop function have become widespread in order to reduce fuel consumption. The idling stop function can save fuel by stopping the engine when the vehicle is stopped. However, when the vehicle is restarted, a large current is consumed to drive the starter, which causes an instantaneous drop in battery voltage and may temporarily stop the operation of the load connected to the battery. Therefore, a circuit configuration is required that compensates for the voltage drop when the engine is restarted and ensures power supply to the load.

[0003] An example of a power supply system for a vehicle with an idling stop function is shown in Patent Document 1. The power supply system for the idling stop vehicle described in Patent Document 1 includes a battery that is charged by the vehicle's alternator, and various electric loads that are supplied with power from the battery. A voltage compensation means is interposed between the battery and the electric loads. The battery is also connected to the starter of the vehicle, and supplies power to the starter when the vehicle is started. In Patent Document 1, a capacitor or a DC-DC converter is applied as the voltage compensation means. When the vehicle is restarted after an idling stop state, if the battery voltage temporarily drops, the voltage compensation means boosts the input voltage and supplies it to the electric loads.

[0004] In recent years, vehicles equipped with a backup power supply for use in the event of a power loss have become widespread. A backup power supply is a power supply that supplies power to a specific load when the main power supply installed in the vehicle becomes unable to supply power due to an accident or the like. Patent Document 2 discloses a backup power supply device having a capacitor, a charging circuit that is provided in the charging path of the capacitor and performs a step-down operation, a boost circuit that is provided in the output path of the capacitor, and a door lock release output terminal that is connected to the boost circuit.

[0005] Vehicle power supply systems that support an idling stop function and also function as a backup power supply have been under consideration for some time. Figure 6 shows a power supply system 101, which is an example of the configuration of a conventional power supply system. The power supply system 101 is separately equipped with a power supply subsystem 102 for stably supplying power to a load when the engine is restarted from an idling stop, and a backup power supply subsystem 103.

[0006] A conventional power supply system 101 includes a power storage device 111 that supplies power to a load 104 at a predetermined voltage. The power storage device 111 is connected to an alternator of the vehicle and is charged while the vehicle is running. The power supply subsystem 102 also includes a DC-DC converter 113, which is made up of a switching element and a coil, between the power storage device 111 and the load 104. When the engine is restarted from an idling stop, the DC-DC converter 113 functions as a boost circuit to compensate for a temporary voltage drop in the power storage device 111 and supply power to the load 104 at a specified voltage.

[0007] The backup power supply subsystem 103 includes a power storage device 112 separate from the power storage device 111, and a DC-DC converter 114 separate from the DC-DC converter 113. The power storage device 112 is charged by the alternator while the vehicle is running. When the power supply from the power storage device 111 is stopped, the backup system 103 boosts the power from the power storage device 112 by the DC-DC converter 114 and supplies the boosted power to a specific load 105 . [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2002-38984 A [Patent Document 2] International Publication No. 2013 / 125170 Summary of the Invention [Problem to be solved by the invention]

[0009] Previous vehicle power supply systems had to incorporate two storage batteries and two DC-DC converters in separate subsystems to accommodate the idling stop function and to function as a backup power source, which made the system complicated and made it difficult to miniaturize the entire circuit.

[0010] The present invention has been made in consideration of the above-mentioned current situation, and has as its object to provide a vehicle power supply system that is compatible with an idling stop function and has a function as a backup power supply, while using a reduced number of elements in a step-up / step-down circuit compared to conventional systems. [Means for solving the problem]

[0011] The invention of claim 1 relates to a vehicle power supply system. The power supply system of claim 1 includes a DC power supply mounted on a vehicle and supplying power to one or more loads, a first switching element connected in series between the DC power supply and the load, a power storage unit electrically connected to the DC power supply, and a DC-DC converter connected between the power storage unit and the first switching element. The vehicle power supply system of the present invention is characterized in that the DC-DC converter includes a second switching element, a third switching element, a fourth switching element, a fifth switching element, and a coil.

[0012] In the DC-DC converter of the vehicle power supply system of the present invention, the second switching element and the third switching element are connected in series to form a first leg, and the fourth switching element and the fifth switching element are connected in series to form a second leg, and it is preferable that one end of the coil is connected between the second switching element and the third switching element, and the other end of the coil is connected between the fourth switching element and the fifth switching element.

[0013] The DC-DC converter of the vehicle power supply system of the present invention functions as a boost converter that boosts a current from a DC power source by turning on the second switching element, turning off the third switching element, and switching the fourth and fifth switching elements when the first switching element is in the off state. Also, when the first switching element is in the on state, the DC-DC converter functions as a buck converter that lowers a current from a DC power source by turning off the second switching element, turning on the third switching element, and switching the fourth and fifth switching elements. Furthermore, when the first switching element is in the off state, the DC-DC converter functions as a boost converter that boosts a current from a power storage unit by turning off the second switching element, turning on the third switching element, and switching the fourth and fifth switching elements. That is, the DC-DC converter of the present invention functions as a buck-boost converter.

[0014] The power storage unit of the vehicle power supply system of the present invention is preferably a secondary battery or an electric double layer capacitor having a rated voltage lower than the supply voltage of the DC power supply.

[0015] In the vehicle power supply system of the present invention, it is preferable that one or more switching elements selected from the group consisting of the first switching element, the second switching element, the third switching element, the fourth switching element, and the fifth switching element are MOSFETs. Effect of the Invention

[0016] In the vehicle power supply system of the present invention, a first switching element is connected in series between a DC power supply and a load, the first DC power supply and a power storage unit are electrically connected via a DC-DC converter, and the DC-DC converter is a step-up / step-down converter, so that it is not necessary to mount separate DC-DC converters for each of the sub-power supply systems for the idling stop function and the backup power supply function as in the conventional system, and therefore a low-cost, large-capacity vehicle power supply system can be provided. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a vehicle power supply system according to a preferred embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing a state in which the vehicle power supply system of the present invention supplies power from a DC power supply to a load. [Diagram 3] FIG. 3 is a diagram showing a state in which the vehicle power supply system of the present invention supplies power from a DC power supply to a load when the engine is restarted from idling. [Figure 4] FIG. 4 is a diagram showing a state in which the vehicle power supply system of the present invention supplies power from a DC power supply to a power storage unit. [Diagram 5] FIG. 5 is a diagram showing a state in which the vehicle power supply system of the present invention supplies power from the power storage unit to a load. [Figure 6] FIG. 6 is a diagram showing a schematic configuration of a conventional vehicle power supply system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a most preferred embodiment of a vehicle power supply system according to the present invention will be described with reference to the drawings.

[0019] 1 shows an embodiment of a vehicle power supply system 1 of the present invention. The vehicle power supply system 1 in this embodiment includes a DC power supply 2, a power storage unit 3, a DC-DC converter 4, and a first switching element Q1.

[0020] The DC power source 2 supplies power to one or more loads 21. Preferably, the DC power source 2 is configured as a power storage device that is charged by a power generation device of the vehicle. As a preferred example, the DC power source 2 can be a lead battery, which is the most common battery for vehicles. Alternatively, the DC power source 2 can be a battery in which a plurality of unit cells, such as lithium ion cells or nickel hydrogen cells, are connected in series. As an alternative configuration, the DC power source 2 can be configured with an alternator and a rectifier circuit.

[0021] The DC power supply 2 supplies power to one or more loads 21 mounted on a vehicle, such as an audio system, an air conditioner, and an engine control ECU. The rated voltage and storage capacity of the DC power supply 2 can be appropriately changed according to the specifications of the voltage and current supplied to the connected load 21.

[0022] A first switching element Q1 is connected in series between the positive electrode side of the DC power supply 2 and the load 21. In a preferred embodiment, a wiring 12 is connected between the positive electrode of the DC power supply 2 and the drain side of the first switching element Q1, and a wiring 13 is connected between the load 21 and the source side of the first switching element Q1.

[0023] The first switching element Q1 may be a semiconductor switching element such as a metal-oxide-semiconductor field-effect transistor (MOSFET) or an insulated-gate bipolar transistor (IGBT), and is preferably an N-channel depletion type MOSFET.

[0024] The power storage unit 3 is a power storage device with a smaller capacity and a lower rated voltage than the DC power source 2, and functions as a backup power source when the DC power source 2 is disconnected from the circuit. As a suitable example, a secondary battery such as a lithium ion cell or a nickel hydrogen cell can be applied to the power storage unit 3. Alternatively, an electric double layer capacitor (EDLC) can be applied as the power storage unit 3. The power storage unit 3 supplies power to a specific load 21 such as an airbag activation circuit or a door lock release device.

[0025] In one embodiment in which the device is mounted on a vehicle, a 12V lead battery can be used as the DC power source 2, and a lithium-ion cell can be used as the power storage unit 3.

[0026] The power storage unit 3 is connected to a DC power source 2 and a load 21 via a DC-DC converter 4. The negative electrode side of the DC power source 2 and the negative electrode side of the power storage unit 3 are connected by a wiring 11. The wiring 11 is grounded.

[0027] The DC-DC converter 4 includes a second switching element Q2, a third switching element Q3, a fourth switching element Q4, a fifth switching element Q5, and a coil 6. Preferably, semiconductor switching elements such as MOSFETs or IGBTs can be used for the second switching element Q2 to the fifth switching element Q5, similar to the first switching element Q1.

[0028] In the DC-DC converter 4, a first leg is formed by connecting a second switching element Q2 and a third switching element Q3 in series, and a second leg is formed by connecting a fourth switching element Q4 and a fifth switching element Q5 in series. In the first leg, the drain side of the second switching element Q2 is connected to a wiring 12, and the source side of the third switching element Q3 is connected to the power storage unit 3. In the second leg, the drain side of the fourth switching element Q4 is connected to a wiring 13, and the source side of the fifth switching element Q5 is connected to a wiring 11.

[0029] One end of the coil 6 of the DC-DC converter 4 is connected between the second switching element Q2 and the third switching element Q3, and the other end is connected between the fourth switching element Q4 and the fifth switching element Q5. The coil 6 stores magnetic energy and releases electric energy according to the on / off control of the second switching element Q2 to the fifth switching element Q5.

[0030] The first switching element Q1 and the DC-DC converter 4 are controlled to be switched on and off by commands from a control means (not shown).

[0031] The operation of the vehicle power supply system 1 of this embodiment will be described below with reference to FIGS.

[0032] [Power supply route during normal driving] 2, the path through which the vehicle power supply system 1 supplies power to the load 21 during normal driving is shown by a bold line. The power supply path is shown. During normal driving, the first switching element Q1 is always on, and the second switching element Q2 is always off. Power is supplied from the DC power supply 2 to the load 21 via the wiring 12, the first switching element Q1, and the wiring 13.

[0033] [Power supply path when restarting the engine from an idling stop state] FIG. 3 shows, with a bold line, a power supply path for supplying power to the load 21 when the engine is restarted from an idling stop state. When the engine is restarted, the voltage supplied from the DC power source 2 to the wiring 12 temporarily drops. At this time, the first switching element Q1 and the third switching element Q3 are controlled to be turned off, and the second switching element Q2 is turned on. Then, the fourth switching element Q4 and the fifth switching element Q5 are controlled to be turned on and off at a predetermined switching period, respectively. Power is supplied from the DC power source 2 to the coil 6 via the wiring 12 and the second switching element Q2, boosted by the coil 6 according to the switching of the switching elements Q4 and Q5, supplied to the wiring 13, smoothed by a smoothing circuit (not shown), and then supplied to the load 21. In this way, when the engine is restarted from an idling stop state, the coil 6, the fourth switching element Q4, and the fifth switching element Q5 function as a boost converter to supply power of an appropriate voltage to the load 21.

[0034] [Power supply path from DC power supply to backup power supply] In FIG. 4, the power supply path when charging the power storage unit 3, which is a backup power source, from the DC power source 2 is shown by a thick line. Power may be supplied to the power storage unit 3 separately from the power supply to the load 21, or may be supplied simultaneously to the load 21. Charging from the DC power source 2 to the power storage unit 3 is performed by turning on the first switching element Q1 and the third switching element Q3, and controlling the fourth switching element Q4 and the fifth switching element Q5 to be turned on and off at a predetermined switching period. Power is supplied from the DC power source 2 to the coil 6 via the wiring 12, the first switching element Q1, and the fourth switching element Q4, and is stepped down by the coil 6 by switching the switching elements Q4 and Q5, and is supplied to the power storage unit 3 at a rated voltage. In this way, the coil 6, the fourth switching element Q4, and the fifth switching element Q5 function as a step-down converter, and the power storage unit 3 is appropriately charged.

[0035] [Power supply path from backup power supply to load] In FIG. 5, the power supply path for supplying power from the power storage unit 3 of the backup power supply to the load 21 is shown by a thick line. Since the power storage unit 3 is a power storage device with a small capacity and a low rated voltage, it is necessary to boost the power in order to supply power to the load 21. Therefore, the first switching element Q1 and the second switching element Q2 are controlled to be turned off, and the third switching element Q3 is turned on. Then, the fourth switching element Q4 and the fifth switching element Q5 are controlled to be turned on and off at a predetermined switching period. Power is supplied from the power storage unit 3 to the coil 6 via the third switching element Q3, boosted by the coil 6 according to the switching of the switching elements Q4 and Q5, supplied to the wiring 13, smoothed by a smoothing circuit (not shown), and then supplied to the load 21. In this way, when the power supply from the DC power source 2 is stopped, the coil 6, the fourth switching element Q4, and the fifth switching element Q5 function as a boost converter, and can supply power of an appropriate voltage from the power storage unit 3 to the load 21.

[0036] [Path that supplies power from the backup power source to the load when restarting the engine from an idling stop state] 5 can be used as a power supply path for supplying power to the load 21 when the engine is restarted from the idling stop state. That is, power from the power storage unit 3 of the backup power supply can be supplied to the coil 6 via the third switching element Q3, and the power can be boosted by the coil 6 in accordance with the switching of the switching elements Q4 and Q5, and supplied to the wiring 13, from which it can be supplied to the load 21.

[0037] The configuration of the vehicle power supply system described in this embodiment can be modified as appropriate. For example, when supplying power to a plurality of loads from a DC power supply, the power supply may be divided into a plurality of loads according to the required voltage and current of the loads. It is possible to supply power from a battery by wiring multiple circuits. Also, when the power supplied to the load is small, a switching element such as a diode can be used instead of a MOSFET. Also, the type of DC power supply and the power storage unit can be changed as appropriate. [Explanation of symbols]

[0038] 1,101 Power Systems 2 DC power supply 3. Power storage unit 4,113,114 DC-DC Converters 6 Coils 11,12,13 Wiring 21,104,105 Load 102 Power Subsystem 103 Backup Power Subsystem 111,112 Electricity storage device Q1 First switching element Q2 Second switching element Q3 Third switching element Q4 Fourth switching element Q5 Fifth switching element

Claims

1. A DC power source mounted on a vehicle and configured to supply power to one or more loads; A first switching element connected in series between the DC power supply and the load; a power storage unit electrically connected to the DC power supply; a DC-DC converter connected between the power storage unit and the first switching element; It is equipped with the DC-DC converter includes a second switching element, a third switching element, a fourth switching element, a fifth switching element, and a coil; the second switching element and the third switching element are connected in series to form a first leg, the fourth switching element and the fifth switching element are connected in series to configure a second leg, one end of the coil is connected between the second switching element and the third switching element, the other end of the coil is connected between the fourth switching element and the fifth switching element, The DC-DC converter comprises: when the first switching element is in an off state, the second switching element is in an on state, the third switching element is in an off state, and a fourth switching element and the fifth switching element are switched to function as a boost converter that boosts a current from the DC power supply; when the first switching element is in an ON state, the second switching element is in an OFF state, the third switching element is in an ON state, and a fourth switching element and the fifth switching element are switched to function as a step-down converter that steps down a current from the DC power supply; and a buck-boost converter configured to function as a boost converter that boosts a current from the power storage unit by turning off the second switching element, turning on the third switching element, and switching the fourth switching element and the fifth switching element when the first switching element is in an off state.

2. 2. The vehicle power supply system according to claim 1, wherein the power storage unit is a secondary battery or an electric double layer capacitor having a rated voltage lower than a supply voltage of the DC power source.

3. 3. The vehicle power supply system according to claim 1, wherein one or more switching elements selected from the group consisting of the first switching element, the second switching element, the third switching element, the fourth switching element, and the fifth switching element are MOSFETs.

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