JP5440400B2 - Power supply - Google Patents

Description

  The present invention relates to a power supply device including two power storage devices connected in parallel.

  Automobile manufacturers are putting effort into the development of low-emission vehicles against the backdrop of consideration for environmental issues and the strengthening of exhaust emission regulations set by the government. In particular, hybrid vehicles that combine a DC power source, an inverter, and a motor in addition to a conventional engine have been rapidly popularized in recent years as low-cost development has accelerated due to advances in secondary battery technology.

  A secondary battery mounted on a DC power supply device of a hybrid vehicle is used for driving a motor or the like and for energy regeneration during vehicle deceleration. And in order to improve energy efficiency, driving | running | working a vehicle appropriately, supplying appropriate electric power according to load, recovering energy with high efficiency at the time of regeneration, etc. are calculated | required. In order to meet these demands, a technology is known in which a hybrid power supply device in which capacitors are connected in parallel to a secondary battery is mounted on a hybrid vehicle or the like as a power supply source of a motor (for example, Patent Document 1). reference).

  A secondary battery and a capacitor are connected using a switch using a mechanical relay so that connection and disconnection are possible, and a switch of a semiconductor element such as a MOSFET (metal oxide semiconductor field effect transistor). Yes (see, for example, Patent Document 2).

  By combining a capacitor with low resistance and excellent output performance with a secondary battery, it is possible to flexibly supply power to a rapidly changing motor load, and to realize energy regeneration during deceleration with high efficiency. Furthermore, by using a capacitor, it is possible to assist starting from an idling stop that requires an instantaneous large current output, and to reduce the burden on the secondary battery and prevent deterioration.

  Since the secondary battery and the capacitor are electrically connected in parallel while the system is driven, they are equipotential. However, if the two are disconnected when the system is stopped, a potential difference is generated due to the difference in each self-discharge amount. Generally, a capacitor is considered to have a larger self-discharge than a secondary battery, and therefore the potential of the capacitor tends to be lower than the potential of the secondary battery.

  When a potential difference is generated between the secondary battery and the capacitor as described above, there is a problem that an inrush current flows from the secondary battery to the capacitor when the capacitor and the secondary battery are connected at the time of starting the system. This inrush current heats and damages the inside of the capacitor, and may cause welding of a relay element that connects the capacitor and the power supply line.

  Therefore, as a method for preventing such an inrush current, a configuration is known in which a path in which a current limiting resistor and a switch are arranged is provided in parallel with respect to a main switch to be connected and disconnected (see, for example, Patent Document 3). . When connecting the capacitor and the secondary battery, first, a path having a current limiting resistor is connected to precharge the capacitor while limiting the amount of current. After that, when the potential difference is almost eliminated, the main switch is connected.

  A configuration is also known in which a semiconductor switching element is provided in parallel with the main switch instead of the current limiting resistor described above, and a precharge function is realized using the semiconductor switching element (for example, Patent Document 4).

JP 2004-31926 A JP 2006-152820 A Japanese Patent Laying-Open No. 2005-312156 JP 2007-143221 A

  In recent years, in addition to electric double layer capacitors, next-generation capacitors with larger capacities have been developed, and in particular, capacitors of the negative electrode doped with lithium ions have very little self-discharge, and the voltage increases depending on the storage environment. There is also. When such a next-generation capacitor is applied, the magnitude relationship between the amount of self-discharge of the secondary battery and the capacitor is reversed, and when the capacitor and the secondary battery are connected, an inrush current flows from the capacitor side to the secondary battery side. There is a possibility of flowing.

  However, the configuration described in Patent Document 4 can cope with an inrush current flowing in the direction from the secondary battery to the capacitor, but the current from the capacitor to the secondary battery is caused to flow through the body diode of the semiconductor switching element. Since it flows, inrush current cannot be prevented.

A power supply device according to a first aspect of the present invention is provided on a current path connecting a first power storage device and a second power storage device connected in parallel to a load, and the first power storage device and the second power storage device. A main switching circuit that switches between a path disconnection state and a path connection state; a first and second switching circuit connected in series; and a potential difference adjustment circuit connected in parallel with the main switching circuit, The first switching circuit has at least one first semiconductor switching element having a built-in body diode oriented to cut off a current flowing from the first power storage device to the second power storage device. , Having at least one second semiconductor switching element including a body diode oriented to cut off current flowing from the second power storage device to the first power storage device, A controller that controls the first and second semiconductor switching elements so as to reduce a potential difference between the power storage device and the second power storage device, and switches the main switching circuit from the path disconnection state to the path connection state after the potential difference is reduced; It is further provided with a feature.
The first switching circuit has a switching element group in which a plurality of first semiconductor switching elements are connected in parallel, and the second switching circuit has a switching element group in which a plurality of second semiconductor switching elements are connected in parallel. You may comprise as follows.
In addition, a potential difference determination unit that determines whether or not the potential difference between the first power storage device and the second power storage device is equal to or greater than a predetermined threshold is set. After performing, it is possible to switch to the path connection state, and when the potential difference determination unit determines that the potential difference is smaller than the threshold value, it is possible to switch to the path connection state without reducing the potential difference.
Furthermore, the control unit is further provided with a current amount adjustment circuit for adjusting the output current amounts of the first and second semiconductor switching elements, and according to the potential difference between the first power storage device and the second power storage device. The potential difference may be reduced by adjusting the amount of output current.
Further, the first and second semiconductor switching elements may be constituted by MOSFETs, and the gate voltages of the MOSFETs may be adjusted to adjust the output current amounts of the first and second semiconductor switching elements.

  According to the present invention, when connecting two power storage devices connected in parallel from a disconnected state, a bidirectional inrush current can be prevented regardless of the magnitude relationship between the voltages of the two power storage devices.

1 is a schematic block diagram of a power supply device according to a first embodiment of the present invention. 3 is a block diagram illustrating a schematic configuration of a control unit 11. FIG. It is a flowchart which shows the control procedure at the time of IGN starting. It is a figure which shows the electric current amount limitation electric current path | route at the time of electric current amount limitation. It is a figure explaining the current limiting method at the time of an electric current amount limiting process, (a) is a time chart of ON / OFF operation | movement of MOSFET76, (b) is the duty ratio D and the gate-source voltage of MOSFET73,74, and The relationship is shown. It is a figure which shows the time chart at the time of an electric current amount limiting process, (a) shows the electric potential difference of the capacitor 6 and the secondary battery 5, (b) shows the ON / OFF state of the electric current amount limiting circuit starting switch 75, (C) shows the state of the MOSFETs 71 and 72. It is a figure explaining a difference with a prior art, (a) shows the conventional structure, (b) shows the structure of 1st Embodiment. It is a figure explaining the power supply device by the 2nd Embodiment of this invention. It is a flowchart which shows the control procedure in 2nd Embodiment. It is a figure which shows a modification.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
-First embodiment-
FIG. 1 is a schematic block diagram when the power supply device according to the first embodiment of the present invention is used for driving a rotating electrical machine. In FIG. 1, a power supply device 1 is connected to an inverter device 3 via relays 2a and 2b. The rotating electrical machine 4 is rotationally driven by the inverter device 3. The rotating electrical machine 4 constitutes a starter motor and a motor generator for starting an engine in an idling stop system of a vehicle.

  The power supply device 1 includes a secondary battery 5 such as a lead storage battery, a capacitor 6 connected in parallel with the secondary battery 5, a discharge cutoff MOSFET 71, a charge cutoff MOSFET 72, a capacitor side current amount limiting MOSFET 73, Secondary battery side current amount limiting MOSFET 74, current amount limiting MOSFET gate voltage fixing resistor 13, MOSFET protection resistor 14, current amount limiting circuit starting MOSFET 76, control unit 11, capacitor voltage detecting unit 12.

  In the present embodiment, as an example, secondary battery 5 and capacitor 6 are mounted as a power storage device, but the present invention can be applied to any combination of power storage devices. The capacitor 6 is configured by connecting a plurality of capacitor cells in a multi-series multi-parallel configuration, and the secondary battery 5 is also configured by a plurality of secondary battery cells connected in a multi-series multi-parallel configuration.

  The power path on the plus (+) side from the capacitor 6 to the secondary battery 5 includes a first current line in which a discharge cutoff MOSFET 71 and a charge cutoff MOSFET 72 are connected in series, and a capacitor-side current amount limiting MOSFET 73. Two current lines are connected in parallel to a second current line in which a secondary battery side current amount limiting MOSFET 74 is connected in series.

  In this embodiment, the parallel connection of the first current line and the second current line is provided on the plus side. However, if necessary, these configurations may be provided on the ground (−) side current line. It may be provided on both the plus side and the ground side.

  Discharge cut-off MOSFET 71 and charge cut-off MOSFET 72 are connected such that body diodes 711 and 721 contained therein are opposite to each other. In the example shown in FIG. 1, the source sides of the MOSFETs 71 and 72 are connected so that the anodes of the body diodes 711 and 721 are connected. In this way, by connecting the two MOSFETs 71 and 72 in series in the opposite directions, when both the MOSFETs 71 and 72 are turned off, a bidirectional current is cut off. Further, when both MOSFETs 71 and 72 are turned on, a non-cut-off state is established with respect to a bidirectional current of a current flowing from the capacitor 6 side to the secondary battery 5 side and a current flowing in the opposite direction.

  In the present embodiment, an enhancement-type N-channel MOSFET having a low on-resistance is used as the discharge cutoff MOSFET 71 and the discharge cutoff MOSFET 72 so that the current path connecting the capacitor 6 and the secondary battery 5 has a low resistance configuration. Is used. However, enhancement-type P-channel MOSFETs may be used for all or any one of the MOSFETs, and the same switching function is realized such as normally-off type GaN-FETs and combinations of IGBTs and diodes. The same applies if possible.

  Further, when N-channel MOSFETs are used as the discharge cutoff MOSFET 71 and the charge cutoff MOSFET 72, a boost gate driver (not shown) for driving the gates of the MOSFETs 71 and 72 is used. Any gate driver can be used as long as it can drive the gate of the N-channel MOSFET, such as a charge pump type.

  In the example shown in FIG. 1, the discharge cut-off MOSFET 71 is arranged on the capacitor 6 side and the charge cut-off MOSFET 72 is arranged on the secondary battery 5 side. However, if the peripheral circuit is configured so that each MOSFET can be controlled, it is arranged in reverse. It doesn't matter.

  On the other hand, regarding the connection between the current amount limiting MOSFET 73 and the current amount limiting MOSFET 74 of the second current line, the body diodes 731 and 741 are connected in opposite directions. Therefore, when both of the MOSFETs 73 and 74 are turned on, the bidirectional current between the current flowing from the capacitor 6 side to the secondary battery 5 side and the current flowing in the opposite direction is not cut off. When both are turned off, a bidirectional current is cut off. In the case of the current amount limiting MOSFETs 73 and 74, the current amount limiting MOSFETs 73 and 74 may be disposed at positions opposite to those in FIG.

  Enhancement type P-channel MOSFETs are used for the current amount limiting MOSFETs 73 and 74, and the output current amount of the current amount limiting MOSFETs 73 and 74 is adjusted by controlling the current amount limiting circuit starting MOSFET 76 by PWM (Pulse Width Modulation). The An enhancement type N-channel MOSFET is used as the current amount limiting circuit starting MOSFET 76.

  The resistor 14 is a protective resistor for preventing a large current from flowing through the MOSFET 76, which is a semiconductor element, from being damaged when the current amount limiting MOSFETs 73 and 74 are turned on / off. When the current amount limiting MOSFETs 73 and 74 are turned on, it is necessary to drop these gate voltages to the ground level. Therefore, the resistance constant of the resistor 14 is sufficiently smaller than the resistance constant of the resistor 13 (for example, three digits smaller). ) Is desirable.

  In the example shown in FIG. 1, enhancement-type P-channel MOSFETs are used for the current amount limiting MOSFETs 73 and 74. However, if the peripheral circuit is configured so as to realize the same function, all of the current amount limiting MOSFETs can be used. Alternatively, an enhancement type N-channel MOSFET may be used for any one of them.

  The controller 11 performs on / off control of the discharge cutoff MOSFET 71 and the charge cutoff MOSFET 72 and PWM control of the current amount limiting circuit starting MOSFET 76. In addition, the control unit 11 monitors the total voltage of the secondary battery 5, each cell voltage of the capacitor 6 detected by the voltage detection unit 12, the total voltage, and the like.

  FIG. 2 is a block diagram showing a schematic configuration of the control unit 11. The control unit 11 controls the entire power supply device, and a dedicated IC or general-purpose microcomputer is used. However, the control unit 11 is not limited to this as long as the same function can be realized. The control unit 11 includes a switch drive unit 111, a potential difference determination unit 112, and a communication unit 113 that performs communication with a host.

  The switch driving unit 111 drives the gate of the switch driving signal and the MOSFET 76 for starting the current amount limiting circuit. The potential difference determination unit 112 monitors the voltages of the secondary battery 5 and the capacitor 6 and performs potential difference determination described later. The capacitor voltage and the secondary battery voltage are A / D converted and captured by an A / D converter (not shown) provided in the potential difference determination unit 112.

Any communication function to the upper level of the communication means 113 may be used as long as it satisfies the necessary functions such as CAN (Controller Area Network), I ² C (Inter-Integrated Circuit), SPI (System Packet Interface). It doesn't matter. In the present embodiment, a start signal (IGN signal) for starting the rotating electrical machine 4 is input from the host system (not shown) to the communication means 113 via the communication function.

  When the IGN signal is input to the communication unit 113, a command for voltage measurement and potential difference determination is output from the communication unit 113 to the potential difference determination unit 112, and the potential difference determination unit 112 measures the voltage of the capacitor 6 and the secondary battery 5. At the same time, potential difference determination described later is performed based on the measurement result. The potential difference determination unit 112 outputs a switch drive signal to the switch drive unit 111 based on the measurement result and the determination result. The switch driving means 111 drives the MOSFETs 71 and 72 and the current amount limiting circuit starting MOSFET 76 based on the switch driving signal.

  When both the MOSFETs 71 and 72 of the first current line are turned on and connected to the secondary battery 5 and the capacitor 6 in a state where the potential difference between the secondary battery 5 and the capacitor 6 is large, from the capacitor side according to the potential difference. An inrush current flows to the secondary battery side or from the secondary battery side to the capacitor side. Therefore, a second current line for precharging is connected in advance and precharging is performed until the potential difference reaches a predetermined potential difference threshold, and then both MOSFETs 71 and 72 are turned on.

  Next, a control method at the time of IGN activation will be described. FIG. 3 is a flowchart showing a control procedure at the time of IGN activation. This control program is executed in the control unit 11. In the flowchart shown in FIG. 3, there is almost no potential difference between the secondary battery 5 and the capacitor 6 after the IGN signal is input to the communication means 113, and before the relays 2a and 2b are turned on. The control is shown.

When an IGN signal is input from the host system to the communication means 113 of the control unit 11, the control shown in FIG. 3 starts and the process proceeds to step S100. In step S100, the potential difference determination unit 112 of the control unit 11 compares the total voltage of the secondary battery 5 with the total voltage of the capacitor 6, and determines whether or not the potential difference | ΔV | is equal to or greater than a preset potential difference threshold V _0. Determine whether. That is, when the secondary battery 5 and the capacitor 6 are connected, it is determined whether or not a current amount limiting process is necessary. As an example of the potential difference threshold V ₀ , the forward voltage (for example, 0.5 V) of the body diodes 711 and 721 of the MOSFETs 71 and 72 is conceivable, but is not necessarily limited thereto.

In step S100, if the potential difference determination unit 112 determines that the potential difference | ΔV | between the total voltage of the secondary battery 5 and the total voltage of the capacitor 6 is smaller than the potential difference threshold V ₀ , the process proceeds to step S120. When the potential difference | ΔV | is smaller than the potential difference threshold value V ₀ , there is no fear of an inrush current. Therefore, in step S120, the switch driving means 111 is set such that the current amount limiting circuit starting MOSFET 76 is off and the MOSFET 71 and MOSFET 72 are It is turned on. As a result, the first current line is in a bidirectional conductive state. That is, the power supply device 1 is in a normal state in which the capacitor 6 can be freely charged and discharged, and the control process shown in FIG. 3 ends.

  When the control process of FIG. 3 is completed, the relays 2a and 2b provided between the power supply device 1 and the inverter device 3 are turned on, and the IGN activation operation is executed. Since a large current flows through the rotating electrical machine 4 when the IGN is activated, MOSFETs corresponding to the large current are used as the discharge cutoff MOSFET 71 and the charge cutoff MOSFET 72.

On the other hand, if it is determined in step S100 that the potential difference | ΔV | is equal to or greater than the potential difference threshold V ₀ , the process proceeds to step S115, and the setting of the switch driving unit 111 is set to perform the current amount limiting process. The current amount limiting process is a process for eliminating the potential difference | ΔV | between the secondary battery 5 and the capacitor 6. The MOSFETs 71 and 72 are set to be turned off, and the current amount limiting circuit starting MOSFET 76 is set. Is set to be PWM controlled. PWM control of the current amount limiting circuit starting MOSFET 76 will be described later.

When the process of step S115 is completed, the process returns to step S100, and the process of determining whether or not the potential difference | ΔV | is greater than or equal to the potential difference threshold V ₀ is performed again. When the charging of the capacitor 6 by setting processing by the secondary battery 5 in step S115 is started, a potential difference | [Delta] V | gradually decreases, the potential difference | [Delta] V | is the processing of step S110 and step S115 to below a potential difference threshold _{V 0} Is repeated. When the potential difference | ΔV | becomes smaller than the potential difference threshold V ₀ , YES is determined in the step S100, and the process proceeds to a step S120.

  FIG. 4 is a diagram showing a current amount limiting current path at the time of current amount limiting processing, showing the capacitor 6, the secondary battery 5, the MOSFETs 71 to 74, and the current amount limiting circuit starting MOSFET 76 necessary for explaining the control method. It is. At the time of limiting the amount of current set in the switch state in step S115, only the second current line is in a bidirectionally conductive state as shown in FIG. 4, and a current amount limiting current path as shown by a broken line is formed. .

  FIG. 5 is a diagram for explaining a current limiting method during the current amount limiting process. 5A is a time chart when the current amount limiting circuit starting MOSFET 76 is periodically turned on and off. FIG. 5B is a time chart showing the duty ratio D and the current amount limiting MOSFET 73 during PWM control. , 74 shows the relationship between the gate-source voltages.

  As shown in FIG. 5A, the current amount limiting circuit starting MOSFET 76 is turned on and off peripherally during PWM control. The current amount limiting circuit starting MOSFET 76 is turned on / off in a cycle T2, and T1 is a time during which the current amount limiting circuit starting MOSFET 76 is on. At this time, the duty ratio D is expressed by D = T1 / T2. The duty ratio D can be adjusted in the range of 0 ≦ D ≦ 1 by the switch driving means 111 of the control unit 11 shown in FIG. When D = 0, the current amount limiting circuit starting MOSFET 76 is always off, and when D = 1, the current amount limiting circuit starting MOSFET 76 is always on.

  When the value of the duty ratio D changes, the drain-source of the current limiting circuit starting MOSFET 76 behaves like a variable resistor. Therefore, as shown in FIG. 5B, the gate-source voltages of the current amount limiting MOSFETs 73 and 74 vary according to the value of the duty ratio D. Since the current amount limiting MOSFETs 73 and 74 are P-channel MOSFETs, the gate voltage is lowered from the source to the on-resistance region as the source voltage decreases.

  VGS0 is a gate-source voltage when the current amount limiting MOSFETs 73 and 74 change from the saturation region to the on-resistance region. However, when the duty ratio D is D = D0, the gate-source voltage is VGS0. Therefore, by adjusting the duty ratio D in the range of 0 to D0, it is possible to limit the amount of drain current flowing through the current amount limiting MOSFETs 73 and 74 (that is, the amount of current flowing through the second current line).

  6A and 6B are time charts during the current amount limiting process. FIG. 6A shows the potential difference | ΔV | between the capacitor 6 and the secondary battery 5, and FIG. 6B shows the current amount limiting circuit starting MOSFET 76. The control state is shown, and (c) shows the on / off states of the MOSFETs 71 and 72. Time t1 is the time when the setting process of step S115 is performed and the current amount limiting process is started.

At t <t1, the current amount limiting circuit starting MOSFET 76 and the MOSFETs 71 and 72 are off. Further, the potential difference at time t1 | [Delta] V | is larger than the potential difference threshold V _0. Furthermore, since the body diodes 711 and 721 of the MOSFETs 71 and 72 and the body diodes 731 and 741 of the current amount limiting MOSFETs 73 and 74 are opposed to each other, the magnitude relationship between the voltages of the secondary battery 5 and the capacitor 6 is determined. Regardless, no current flows through either the first current line or the second current line.

  At time t1, the current amount limiting circuit starting MOSFET 76 is PWM controlled to control the drain currents of the current amount limiting MOSFETs 73 and 74, and a current amount limiting current as shown in FIG. The direction in which the current limiting current flows depends on the magnitude relationship between the potential of the capacitor 6 and the potential of the secondary battery 5 before connection.

  In the current amount limiting process of t> t1, the current amount limiting current flows, whereby the potential difference | ΔV | between the capacitor 6 and the secondary battery 5 gradually decreases. The slope of the straight line indicating the change in the potential difference | ΔV | (that is, the degree of current amount limitation) can be adjusted by changing the duty ratio D of the PWM control.

When the potential difference | ΔV | between the capacitor 6 and the secondary battery 5 decreases due to the current amount limiting process and the potential difference | ΔV | falls below the potential difference threshold V ₀ at time t2, the process proceeds from step S100 to step S120 in FIG. The amount limiting circuit starting MOSFET 76 is turned off, and the MOSFET 71 and the MOSFET 72 are turned on. As a result, the first current line becomes bidirectionally conductive, and the potential difference | ΔV | quickly decreases to 0V. In step S120, the current amount limiting circuit starting MOSFET 76 is turned off and the current amount limiting MOSFETs 73 and 74 are turned off (cut-off state). However, the current amount limiting MOSFETs 73 and 74 are turned on (non-cut-off state). The current amount limiting circuit starting MOSFET 76 may be controlled as described above.

  In the first embodiment described above, the current amount limiting MOSFETs 73 and 74 are arranged in series so that the body diodes 731 and 741 face the second current line as a precharge circuit as shown in FIG. Inrush current during precharging for eliminating the potential difference can be prevented in both directions. Such bidirectional bidirectional inrush current prevention during precharging will be described with reference to FIG.

  FIG. 7A shows an example of a conventional configuration (corresponding to the configuration described in Patent Document 4), and only one semiconductor switching element 40 is provided in the precharge circuit. Relays SMR1 and SMR2 are used for the main switch. When the secondary battery 5 and the capacitor 6 are disconnected, the relays SMR1 and SMR2 are opened. In this conventional configuration, the case where the voltage VCAP of the capacitor 6 becomes larger than the voltage VBAT of the secondary battery 5 is not considered, and the relay SMR1 is closed for precharging in such a situation (VCAP> VBAT). As a result, an inrush current flows through the body diode 401 of the semiconductor switching element 40.

  FIG. 7B shows the case of the present embodiment, and relays SMR1 and SMR2 are arranged as main switches in the same manner as in FIG. 7A for easy comparison. In this configuration, since the body diodes 731 and 741 of the current amount limiting MOSFETs 73 and 74 are opposed to each other, when the relay SMR2 is closed and precharging is performed, the body diodes 731 and 741 are used to enter. No current flows. If the relay SMR2 is closed, the current amount limiting circuit starting MOSFET 76 is PWM-controlled, and the potential difference is eliminated by flowing the limited current.

  Further, in the configuration shown in FIGS. 1 and 4, since a set of MOSFETs 71 and 72 are used instead of the relays SMR1 and SMR2 including the mechanically movable portion in FIG. 7B, the durability of the main switch is improved. be able to. Since the MOSFETs 71 and 72 are also arranged so that the body diodes 711 and 721 are opposed to each other, by turning off both the MOSFET 71 and the MOSFET 72, the secondary battery 5 and the capacitor 6 can be completely cut off. it can.

  In the above-described embodiment, the amount of current is limited by adjusting the gate voltage of the current amount limiting MOSFETs 73 and 74 by PWM control of the current amount limiting circuit starting MOSFET 76. However, instead of using the current amount limiting circuit starting MOSFET 76, the gates of the current amount limiting MOSFETs 73 and 74 may be directly PWM controlled. Further, the present embodiment can be applied as long as the gate voltage of the current amount limiting MOSFETs 73 and 74 can be adjusted regardless of the PWM control.

-Second Embodiment-
FIG. 8 is a diagram for explaining a power supply device according to the second embodiment of the present invention, and corresponds to FIG. 4 in the first embodiment. In the second embodiment shown in FIG. 8, instead of the current amount limiting circuit starting MOSFET 76, a current amount limiting circuit starting switch 75 for turning on and off the current amount limiting MOSFETs 73 and 74 is provided, A limiting resistor 8 is provided in series with the amount limiting MOSFETs 73 and 74 to limit the amount of current flowing through the second current line. In FIG. 8, a normal relay is used as the current amount limiting circuit starting switch 75, but any other device having an equivalent function such as a semiconductor switch (eg, MOSFET) may be used.

  FIG. 9 is a flowchart showing a control procedure in the case of the configuration of FIG. Each process of step S115 and step S120 of FIG. 3 is replaced by step S215 and step S220 of FIG. Prior to receiving the IGN signal, the current amount limiting circuit starting switch 75 and the MOSFETs 71 and 72 are all turned off. When the current amount limiting circuit starting switch 75 is off, the gate voltages of the current amount limiting MOSFETs 73 and 74 are equal to the source voltage by the gate voltage fixing resistor 13. Therefore, the current amount limiting MOSFETs 73 and 74 are turned off. As a result, the first and second current lines are cut off.

  In step S215, the current amount limiting circuit starting switch 75 is turned on, and the MOSFETs 71 and 72 are turned off. When the current amount limiting circuit starting switch 75 is turned on, the gate voltages of the current amount limiting MOSFETs 73 and 74 drop to the ground level, and the current amount limiting MOSFETs 73 and 74 are turned on. As a result, the current whose current amount is limited by the limiting resistor 8 flows to the second current line, and the potential difference | ΔV | between the secondary battery 5 and the capacitor 6 decreases. The direction in which the current limiting current flows depends on the magnitude relationship between the potential of the capacitor 6 and the potential of the secondary battery 5 before connection.

  In step S220, all of the current amount limiting circuit starting switch 75 and MOSFETs 71 and 72 are turned on. As a result, the first and second current lines are in a bidirectionally conductive state, and the power supply device 1 is in a normal state in which the capacitor 6 can be freely charged and discharged.

In the present embodiment, when the potential difference | ΔV | between the secondary battery 5 and the capacitor 6 falls below the potential difference threshold V ₀ , the first and second current lines are set in the bidirectionally conductive state in step S120. However, even when the first and second current lines are in a bidirectionally conductive state, the current mainly flows through the first current line because the current limiting resistor 8 is provided in the second current line. For this reason, the current amount limiting circuit starting switch 75 may be turned off to turn off the current amount limiting MOSFETs 73 and 74 provided on the second current line, and only the first current line may be in a bidirectionally conductive state. .

  Enhancement-type P-channel MOSFETs are used for the current amount limiting MOSFETs 73 and 74. However, if a peripheral circuit is configured so that the same function can be realized, all or any one of the current amount limiting MOSFETs can be used. An enhancement type N-channel MOSFET may be used. When enhancement type P-channel MOSFETs are used for the current amount limiting MOSFETs 73 and 74, the current amount limiting is performed only by turning on the current amount limiting circuit starting switch 75 and setting the gate voltage of the current amount limiting MOSFETs 73 and 74 to the ground level. The MOSFETs 73 and 74 can be easily turned on.

-Third embodiment-
The third embodiment is control in consideration of the lower limit voltage of the capacitor 6. Examples of the capacitor having the lower limit voltage include a lithium ion capacitor having an overdischarge threshold.

  If an overdischarged state is maintained in a lithium ion capacitor, gas generation or the like may occur inside, and the performance of the capacitor is significantly deteriorated. Therefore, in the present embodiment, the control unit 11 determines whether the cell voltage of the capacitor 6 is below the overdischarge threshold. When it is determined that the cell voltage is lower than the overdischarge threshold, the discharge cutoff MOSFET 71 of the first current line is turned off, and the current amount limiting MOSFET 73 provided on the second power supply line, 74 is turned off. Thereby, only charging by the first current line is permitted for the capacitor 6. With such a configuration, the capacitor 6 is prevented from being discharged and cell deterioration due to overdischarge can be prevented, which is effective in improving the safety and extending the life of the lithium ion capacitor.

  Such control may be performed when the capacitor 6 and the secondary battery 5 are connected. However, when the connection state is changed to the disconnected state, the relay 2a and 2b are turned on and the power supply device 1 is turned on. This is suitable in a state where a load (inverter device 3) is connected. For example, if the capacitor 6 is switched from the connected state to the disconnected state when the capacitor 6 is below the overdischarge threshold value, the capacitor 6 is always left in the overdischarged state during the disconnection, and the performance of the capacitor 6 is deteriorated. . Therefore, in such a case, the application of the control is effective.

  In the embodiment described above, for example, one element is used for each of the discharge cutoff MOSFET 71 and the charge cutoff MOSFET 72 as shown in FIG. However, in order to cope with a larger current, as shown in FIG. 10, the discharge cutoff MOSFET 71 and the charge cutoff MOSFET 72 may be configured by a plurality of MOSFETs connected in parallel in the same direction. With this configuration, the current that flows during normal use is distributed among the MOSFETs connected in parallel, so that a larger current can be accommodated. Note that the current amount limiting MOSFETs 73 and 74 may also be constituted by a plurality of MOSFETs connected in parallel.

  In the embodiment described above, the power supply device 1 is provided on the current path connecting the secondary battery 5 and the capacitor 6 to the secondary battery 5 and the capacitor 6 that are connected in parallel to the inverter device 3. The control unit 11 includes MOSFETs 71 and 72 that switch between a disconnected state and a path connection state, a potential difference adjusting circuit that is connected in parallel with the MOSFETs 71 and 72 and includes the current amount limiting MOSFETs 73 and 74 connected in series. Since the body diodes 731 and 741 of the current amount limiting MOSFETs 73 and 74 are provided so as to face each other, at the time of precharging via the second current line provided with the current amount limiting MOSFETs 73 and 74, It is possible to prevent an inrush current from occurring in the direction of. Thus, the potential difference between the secondary battery 5 and the capacitor 6 can be eliminated without generating an inrush current during precharging.

  Further, when the MOSFETs 71 and 72 are switched from the path cut state to the path connected state, it is determined whether or not the potential difference between the secondary battery 5 and the capacitor 6 is equal to or greater than a predetermined threshold value. When it is determined that the potential difference is smaller than the threshold value, switching to the path connection state is performed without reducing the potential difference. Therefore, inrush current does not occur when the MOSFETs 71 and 72 are turned on and switched to the path connection state.

  In the above-described embodiment, the power source having a configuration in which the secondary battery and the capacitor are connected in parallel has been described as an example. However, the present invention is not limited thereto, and different types of power storage elements having different self-discharge rates are combined in parallel. It can be applied to other power supply devices. That is, the present invention can also be applied to combinations such as capacitors and capacitors and secondary batteries and secondary batteries. Further, as the capacitor 6, a hybrid capacitor using different electrode materials for the positive electrode material and the negative electrode material, for example, a lithium ion capacitor in which the negative electrode is doped with lithium ions can be applied.

  As described above, this embodiment can be applied to any type of power storage device combination as long as it is a power supply device in which different types of power storage devices having different self-discharge rates are combined in parallel. When making a connection, the connection process can be performed safely by preventing a bidirectional inrush current regardless of the magnitude relationship between the two voltages. As a result, when a secondary battery is used as a power storage device, the burden caused by the flow of a large current is reduced. Therefore, the secondary battery can be reduced in size, reduced in price, extended in life, and highly reliable in the entire power supply device. Is also effective.

  In the above-described embodiment, the case where the present invention is applied to a vehicle idling stop system has been described as an example. However, the present invention is not limited to this, and the present invention can be applied to a power supply apparatus that supplies power to various loads. The above description is merely an example, and the present invention is not limited to the above embodiment as long as the characteristics of the present invention are not impaired. Moreover, it is also possible to combine one or a plurality of embodiments and modification examples, and the effects of each embodiment can be achieved independently or synergistically.

  1: power supply device, 2: relay, 3: inverter device, 4: rotating electric machine, 5: secondary battery, 6: capacitor, 8: current limiting resistor, 11: control unit, 12: capacitor voltage detection unit, 13: gate Voltage fixing resistor, 71: MOSFET for discharging interruption, 72: MOSFET for charging interruption, 73: MOSFET for limiting current amount on the capacitor side, 74: MOSFET for limiting current amount on the secondary battery side, 75: Switch for starting current amount limiting circuit 76: Current amount limiting circuit starting MOSFET, 111: Switch driving means, 112: Potential difference judging means, 113: Communication means, 14: MOSFET protection resistor, 711, 721, 731, 741: Body diode

Claims (13)

A first power storage device and a second power storage device connected in parallel to the load;
A main switching circuit that is provided on a current path connecting the first power storage device and the second power storage device, and switches between a path disconnection state and a path connection state;
A first and second switching circuit connected in series, and a potential difference adjusting circuit connected in parallel with the main switching circuit;
The first switching circuit has at least one first semiconductor switching element including a body diode oriented to cut off a current flowing from the first power storage device to the second power storage device,
The second switching circuit has at least one second semiconductor switching element containing a body diode oriented to cut off a current flowing from the second power storage device to the first power storage device,
The first and second semiconductor switching elements are controlled to reduce a potential difference between the first power storage device and the second power storage device, and the main switching circuit is moved from the path disconnected state after the potential difference is reduced. A power supply apparatus further comprising a control unit for switching to the path connection state. The power supply device according to claim 1,
The first switching circuit includes a switching element group in which a plurality of the first semiconductor switching elements are connected in parallel.
The second switching circuit has a switching element group in which a plurality of the second semiconductor switching elements are connected in parallel. The power supply device according to claim 1 or 2,
A potential difference determination unit that determines whether a potential difference between the first power storage device and the second power storage device is equal to or greater than a predetermined threshold;
The control unit switches to the path connection state after reducing the potential difference when the potential difference determination unit determines that the potential difference is greater than or equal to the threshold value, and when the potential difference determination unit determines that the potential difference is smaller than the threshold value, A power supply apparatus that switches to the path connection state without performing reduction. The power supply device according to any one of claims 1 to 3,
The control unit further includes a current amount adjustment circuit that adjusts an output current amount of the first and second semiconductor switching elements, and controls a potential difference between the first power storage device and the second power storage device. In response, the output current amount is adjusted to reduce the potential difference. The power supply device according to claim 4,
The first and second semiconductor switching elements are composed of MOSFETs,
The power supply device, wherein the current amount adjusting circuit adjusts an output current amount of the first and second semiconductor switching elements by adjusting a gate voltage of the MOSFET. The power supply device according to any one of claims 1 to 3,
The potential difference adjusting circuit has a resistance element connected in series to the first and second switching circuits,
The control unit reduces the potential difference by turning on the first and second semiconductor switching elements, respectively. The power supply device according to any one of claims 1 to 3,
The control unit performs PWM (Pulse Width Modulation) control on the first and second semiconductor switching elements in accordance with a potential difference between the first power storage device and the second power storage device, thereby controlling an output current amount. A power supply device that adjusts and reduces the potential difference. The power supply device according to any one of claims 1 to 7,
The main switching circuit is
A third switching circuit having at least one third semiconductor switching element containing a body diode oriented to cut off a current flowing from the first power storage device to the second power storage device;
Formed by connecting in series a fourth switching circuit having at least one fourth semiconductor switching element containing a body diode oriented to cut off the current flowing from the second power storage device to the first power storage device A power supply device characterized by that. The power supply device according to claim 8, wherein
The third switching circuit has a switching element group in which a plurality of the third semiconductor switching elements are connected in parallel,
The fourth switching circuit includes a switching element group in which a plurality of the fourth semiconductor switching elements are connected in parallel. The power supply device according to claim 8 or 9,
The first and second semiconductor switching elements are composed of enhancement type P-channel MOSFETs,
The power supply apparatus, wherein the third and fourth semiconductor switching elements are composed of enhancement type N-channel MOSFETs. The power supply device according to any one of claims 8 to 10,
The first power storage device is configured with a capacitor cell, and the second power storage device is configured with a secondary battery cell,
An overdischarge determination unit for determining whether the voltage of the capacitor cell is below an overdischarge threshold;
When the overdischarge determination unit determines that the control unit is below an overdischarge threshold, the control unit turns off the first, second, and third switching elements, and sets the fourth switching element. A power supply device which is turned on. The power supply device according to any one of claims 1 to 10,
At least one of said 1st and 2nd electrical storage apparatus is comprised with the hybrid capacitor using a different electrode material for a positive electrode material and a negative electrode material, The power supply device characterized by the above-mentioned. The power supply device according to claim 12,
The hybrid capacitor is a lithium ion capacitor having a negative electrode doped with lithium ions.

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