JP2005189073A - Voltage detection device for dc power source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an unnecessary closed circuit from being formed. <P>SOLUTION: At the time of starting a maintenance work for a vehicle, the internal continuity of the DC power source 11 is disconnected by making the maintenance SW (SW0) 22 turn off, and making the off set power source SW (SW5) 23 turn off. Therefore, the formation of the closed circuit, i.e. the current flow between the positive pole 11p and the negative pole 11n of the DC power source 11 is inhibited even at the time when the positive terminal 11p of the DC power source 11 and the negative terminal 11n are short-circuited. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a voltage detection apparatus for a DC power supply.

Conventionally, in an assembled battery (battery) formed by connecting a plurality of unit cells, such as secondary batteries, in series, as a cell voltage detection circuit connected in parallel to each unit cell, for example, from an optical element such as a photo MOSFET There is known a battery voltage measuring device that includes a flying capacitor circuit that detects a voltage between terminals of each unit cell (see, for example, Patent Document 1).
Japanese Patent No. 3430083

However, in the battery voltage measuring device according to the above prior art, it is difficult to downsize and highly integrate optical elements such as photo MOSFETs. For example, even when the battery voltage measuring device is mounted on a vehicle. There is a problem that it is difficult to downsize the battery voltage measuring device. In addition, it is difficult to increase the temperature resistance of an optical element such as a photo MOSFET. For example, when a battery voltage measuring device is mounted on a vehicle having a relatively high environmental temperature, the battery voltage measuring device is appropriately operated. May be difficult.
For such a problem, for example, instead of an optical element such as a photo MOSFET, a switching capacitor composed of an FET such as a p-channel MOSFET and an n-channel MOSFET is provided to constitute a flying capacitor circuit, thereby requiring a device configuration. It is possible to easily reduce the size of the apparatus and increase the temperature resistance while suppressing the increase in cost.
By the way, in the assembled battery as described above, for example, in order to prevent a closed circuit from being formed even when the positive electrode side terminal and the negative electrode side terminal of the assembled battery are short-circuited during maintenance work or the like, It is desirable to provide a maintenance switch for cutting off the connection between adjacent unit cells in series. However, when a flying capacitor circuit is configured with FET switching elements, an offset power supply that applies a predetermined bias voltage to the unit cell on the lowest potential side of the battery in order to drive each switching element in a desired state Is provided at a position on the lowest potential side of the battery, even if the maintenance switch is set to the OFF (open) state, a closed circuit including the positive and negative terminals and the offset power source of the short-circuited assembled battery It is desirable to prevent such a closed circuit from being formed.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a voltage detection device for a DC power supply capable of preventing an unnecessary closed circuit from being formed.

  In order to solve the above-described problems and achieve the object, a voltage detection apparatus for a DC power supply according to the first aspect of the present invention includes a plurality of unit cells (for example, the unit cells 11a in the embodiment) connected in series. A connected DC power supply (for example, the DC power supply 11 in the embodiment) and a flying capacitor circuit (for example, the voltage detection device 21 in the embodiment) that detects a voltage between terminals of each unit cell of the DC power supply. An offset power supply that is connected to a position on the lowest potential side of the DC power supply and applies a predetermined bias voltage to the terminal of the unit cell on the lowest potential side of the DC power supply. (For example, the offset power source 24 in the embodiment) and the inter-unit cell switch (for example, in the embodiment) that is connected in series in the DC power source and cuts off the connection between adjacent unit cells. Maintenance SW (SW0) 22), an offset power cut-off switch that cuts off the connection between the position of the lowest potential side of the DC power supply and the offset power supply (for example, offset power supply SW (SW5) 23 in the embodiment), Opening means (for example, step S02, step S03 in the embodiment) for setting the inter-unit cell switch and the offset power cut-off switch to an open state when performing maintenance work related to the DC power supply is provided. And

  According to the voltage detection device for a DC power supply having the above configuration, when performing maintenance work, in addition to the inter-unit cell switch, the offset power cut-off switch is turned off, so that the positive-side terminal and the negative-side terminal of the DC power supply Even when the short circuit is short-circuited, a closed circuit including the short-circuited positive and negative terminals and the offset power supply is formed, that is, current is generated between the positive and negative terminals of the DC power supply. It can be prevented from flowing.

  Furthermore, in the voltage detection device for a DC power supply according to the second aspect of the present invention, the voltage detection device for the DC power supply is mounted on a vehicle, and a start switch (for example, in the embodiment) that instructs the vehicle to start. Connection means (for example, step S05, step S06, step S14, step S15 in the embodiment) for setting the inter-unit cell switch and the offset power cut-off switch to the connected state when the start SW 15) is in the on state. It is characterized by providing.

  According to the voltage detection device for a DC power supply having the above-described configuration, when the process of detecting the voltage between the terminals of the unit cell is executed by setting the start switch to the on state, the flying capacitor circuit is appropriately operated. Can do.

As described above, according to the voltage detection device for a power storage device of the present invention described in claim 1, even when the positive electrode side terminal and the negative electrode side terminal of the DC power supply are short-circuited during the maintenance work, Thus, it is possible to prevent a closed circuit including the short-circuited positive and negative terminals and the offset power source from being formed.
In addition, according to the voltage detection device for a power storage device of the present invention described in claim 2, the flying capacitor circuit can be appropriately operated.

Hereinafter, a voltage detection apparatus for a DC power supply according to an embodiment of the present invention will be described with reference to the accompanying drawings.
A DC power supply voltage detection device 10 according to the present embodiment is mounted on a vehicle such as a fuel cell vehicle or a hybrid vehicle, for example, and a plurality of unit cells 11a,..., 11a are connected in series as shown in FIG. The output voltage of the input / output terminal of each unit cell 11a of the DC power supply 11 thus formed is detected.
Here, the DC power source 11 includes, for example, a capacitor in which a plurality of capacitor cells made of, for example, an electric double layer capacitor or an electrolytic capacitor are connected in series, or a plurality of cells (for example, a secondary battery such as a lithium ion battery) in series. The battery is connected to the battery.
The DC power supply 11 is connected in parallel to a motor drive circuit 13 that controls the drive and regenerative operation of a motor 12 as a vehicle drive source, for example, as shown in FIG.

The motor drive circuit 13 includes, for example, a PWM inverter based on pulse width modulation (PWM) configured by a bridge circuit using a plurality of switching elements such as transistors. For example, the motor drive circuit 13 is connected to a stator winding of the motor 12 having a plurality of phases. The energization is sequentially commutated.
The operation of the motor drive circuit 13 is controlled by the control device 14. For example, when the motor 12 is driven, based on a torque command output from the control device 14, the DC power supplied from the DC power supply 11 is converted into AC power and the motor is operated. 12 is supplied. On the other hand, when a driving force is transmitted from the driving wheel W side to the motor 12 side via the transmission (T / M) during regenerative operation such as when the vehicle is decelerated, the motor driving circuit 13 causes the motor 12 to generate power. To generate a so-called regenerative braking force and recover the kinetic energy of the vehicle body as electric energy.
Thus, for example, the control device 14 outputs a start SW 15 that outputs a signal instructing start or stop of the vehicle according to an input operation of the operator, and a detection signal of the accelerator opening AP related to the accelerator operation amount of the driver. Is connected to an accelerator opening sensor 16 that outputs a rotational speed sensor 17 that outputs a detection signal of the rotational speed Nm of the motor 12.
A switch 18 whose opening / closing state is controlled by the control device 14 according to the on / off state of the start SW 15 is provided between the positive terminal 11p of the DC power source 11 and the motor drive circuit 13.

As shown in FIG. 1, for example, the voltage detection device 10 of the DC power supply according to the present embodiment has each voltage detection device connected in parallel to the input / output terminals of the unit cells 11a,..., 11a via voltage detection lines. 21, 21, maintenance SW (SW 0) 22 provided at a connection portion between adjacent unit cells 11 a and 11 a at appropriate positions inside the DC power supply 11, a negative terminal 11 n of the DC power supply 11, and a motor drive circuit 13 includes an offset power supply SW (SW5) 23 provided at an appropriate position between the power supply 13, an offset power supply 24, an offset power supply grounding unit 25, and a control device 14.
The open / close state of the maintenance SW (SW0) 22 is controlled by the control device 14, and as described later, for example, when maintenance work starts while the vehicle is stopped, or when the start SW 15 is OFF (that is, when the vehicle is stopped), etc. ) State, and is set to an ON (connected) state at the time of cell voltage detection for detecting a cell voltage between input / output terminals of each unit cell 11a,..., 11a.

The offset power supply SW (SW5) 23 is a switching element made of an FET such as an n-channel MOSFET. The drain of the switching element is connected to the negative terminal 11n of the DC power supply 11, and the source is the positive side of the offset power supply 24. The gate is connected to the control device 14. For example, when the maintenance work is started while the vehicle is stopped, or when the start SW 15 is turned off, for example, the gate of the switching element is grounded by the control device 14, whereby the offset power supply SW23 is set to the off state. On the other hand, when the cell voltage is detected, the control device 14 releases the ground of the gate of the switching element, and an ON signal having an appropriate voltage level is input to the gate, whereby the offset power supply SW23 is set to the ON state.
The offset power supply 24 applies a predetermined bias voltage to the input / output terminal of the unit cell 11a on the lowest potential side of each unit cell 11a,..., 11a of the DC power supply 11, and is parallel to the unit cell 11a on the lowest potential side. The connected voltage detection device 21, and further, the first switching element (SW1) 31 provided in each voltage detection device 21,..., 21 connected in parallel to each unit cell 11a,. The second switching element (SW2) 32 is driven in a desired state, and the negative terminal of the offset power source 24 is grounded by being connected to the offset power source grounding section 25.
That is, the bias voltage output from the offset power supply 24 is set to be at least a value equal to or higher than the gate drive voltage of the first and second switching elements 31 and 32.

The voltage detection device 21 includes, for example, first to fourth switching elements (SW1 to SW4) 31, 32, 34, and 35 that constitute a flying capacitor circuit, a capacitor 33, a voltage measurement unit 36, and a drive unit 38. It is configured.
The first switching element (SW1) 31 and the second switching element (SW2) 32 are switching elements made of FETs such as p-channel MOSFETs, for example. The source of the first switching element 31 is connected to the positive terminal of the unit cell 11a. The source of the second switching element 32 is connected to the negative terminal of the unit cell 11a, and each gate is connected to the drive unit 38. A capacitor 33 is connected between the drain of the first switching element 31 and the drain of the second switching element 32.
The third switching element (SW3) 34 and the fourth switching element (SW4) 35 are switching elements made of FETs such as n-channel MOSFETs, for example, and the drain of the third switching element 31 is the same as that of the first switching element 31. The drain of the fourth switching element 35 is connected to the drain of the second switching element 32, and each gate is connected to the drive unit 38. A voltage measuring unit 36 is connected between the source of the third switching element 34 and the source of the fourth switching element 35.
The voltage measuring unit 36 detects the voltage across the capacitor 33 and outputs a digital signal obtained by A / D converting the detection result to the control device 14.
A diode is disposed between the source and drain of each switching element 31, 32, 34, 35, and the anode of each diode is connected to each drain of the first and second switching elements 31, 32. Is connected to the cathode of each diode. The cathodes of the diodes are connected to the drains of the third and fourth switching elements 34 and 35, and the anodes of the diodes are connected to the sources.
The source of the fourth switching element 35 connected to the voltage measuring unit 36 is grounded by being connected to the grounding unit 37.

In this voltage detection device 21, when the cell voltage is detected, first and second switching elements 31, 32 are first set to an on state, and third and fourth switching elements 34, 35 are set to an off state. The capacitor 33 is charged such that the voltage across the capacitor 33 is equal to the terminal voltage of the unit cell 11a.
Next, the first and second switching elements 31 and 32 are set to the off state, the third and fourth switching elements 34 and 35 are set to the on state, and the voltage across the capacitor 33 is changed by the voltage measuring unit 36. Detected.
Each switching element 31, 32, 34, 35 is set to an off state when the gate is grounded by the driving unit 38, while the grounding of the gate is released by the driving unit 38 and an appropriate voltage level is set. When the ON signal is input to the gate, the ON state is set.
The drive unit 38 whose operation state is controlled by the control device 14 is grounded, for example, by being connected to the grounding unit 39, and is a unit in which the voltage source to be measured (that is, the voltage detection device 21 is connected in parallel). A cell voltage between the input and output terminals of the cell 11a) is used as a gate drive voltage for the first and second switching elements 31 and 32. Here, the bias voltage output from the offset power supply 24 connected to the negative terminal 11n of the DC power supply 11 via the offset power supply SW (SW5) 23 is at least the gate drive of the first and second switching elements 31 and 32. Since the voltage is set to be equal to or higher than the voltage, the gate driving voltage set according to the cell voltage of the unit cell 11a by the driving unit 38 is the first and second switching elements 31, 32. The first and second switching elements 31 and 32 can be driven by the bias voltage output from the offset power supply 24 even when the gate drive voltage is lower than the first gate drive voltage.

  The voltage detection apparatus 10 for a DC power supply according to the present embodiment has the above-described configuration. Next, the operation of the voltage detection apparatus 10 for the DC power supply will be described with reference to the accompanying drawings.

When the vehicle is operated, the cell voltage between the input / output terminals of the unit cells 11a,..., 11a is detected at an appropriate timing. When this cell voltage is detected, the maintenance SW (SW0) 22 and the offset power supply SW (SW5) 23 are detected. Is set to on (connected).
On the other hand, the maintenance SW (SW0) 22 and the offset power supply SW (SW5) 23 are turned off (opened) when, for example, maintenance work is started while the vehicle is stopped, or when the start SW 15 is turned off (that is, when the vehicle is stopped). Is set.
Here, by turning off the maintenance SW (SW0) 22, the continuity inside the DC power supply 11 is cut off. That is, even if the positive electrode side terminal 11p and the negative electrode side terminal 11n of the DC power supply 11 are short-circuited in this state, it is prohibited to flow a current into the DC power supply 11.
However, even when the maintenance SW (SW0) 22 is turned off, when the offset power supply SW (SW5) 23 is turned on, the positive terminal 11p and the negative terminal 11n of the DC power supply 11 are short-circuited. In this case, for example, as shown in FIG. 2, the offset power source SW (SW 5) 23, the offset power source 24, the offset power source grounding unit 25, the grounding unit 37 of the voltage detection device 21, and the third and first switching are sequentially performed. A closed circuit in which current flows back to the offset power supply SW (SW5) 23 through the elements 34, 31 or the fourth and second switching elements 35, 32 and the short-circuited portion of the positive terminal 11p and the negative terminal 11n. L is formed.
Therefore, in addition to the maintenance SW (SW0) 22, the offset power supply SW (SW5) 23 is turned off so that the positive terminal 11p and the negative terminal 11n of the DC power supply 11 are short-circuited. The closed circuit L is formed, that is, the current is prohibited from flowing between the positive terminal 11p and the negative terminal 11n of the DC power supply 11.

Hereinafter, processing for controlling the on / off states of the maintenance SW (SW0) 22 and the offset power supply SW (SW5) 23 will be described.
First, for example, in step S01 shown in FIG. 3, it is determined whether or not the vehicle maintenance operation is started. Here, on the basis of a signal output from a sensor or an appropriate switch for detecting an appropriate state related to the start of maintenance work of the vehicle, for example, a switch for detecting whether or not the casing accommodating the DC power supply 11 is opened, the vehicle It is determined whether or not the maintenance work starts.
If this determination is “NO”, the flow proceeds to step S 04 described later.
On the other hand, if this determination is “YES”, the flow proceeds to step S 02.
In step S 02, maintenance SW (SW 0) 22 is turned off to prohibit current from flowing into DC power supply 11.
Next, in step S03, the offset power supply SW (SW5) 23 is turned off, the formation of the closed circuit L including the offset power supply SW (SW5) 23 is prohibited, and the series of processing ends.
In step S04, it is determined whether or not the start SW 15 of the vehicle is on.
If the determination result in step S04 is “NO”, the series of processing ends.
On the other hand, if the determination result of step S04 is “YES”, the process proceeds to step S05.
In step S05, maintenance SW (SW0) 22 is turned on.
Next, in step S06, the offset power supply SW (SW5) 23 is turned on.
Next, in step S07, the execution of the cell voltage detection process is started, and the series of processes is ended.

As described above, according to the voltage detection device 10 of the DC power supply according to the present embodiment, the offset power supply SW (SW5) 23 is turned off in addition to the maintenance SW (SW0) 22 at the start of vehicle maintenance work. Thus, even when the positive terminal 11p and the negative terminal 11n of the DC power supply 11 are short-circuited, the closed circuit L is formed, that is, the positive terminal 11p and the negative terminal 11n of the DC power supply 11 are formed. It is possible to prevent a current from flowing between.
Moreover, when the start of the vehicle SW 15 is set to the on state and the execution of the cell voltage detection process is started, the maintenance SW (SW 0) 22 and the offset power source SW (SW 5) 23 are turned on. Thus, the voltage detection device 21 can be appropriately operated.

In the above-described embodiment, the on / off state of the maintenance SW (SW0) 22 and the offset power supply SW (SW5) 23 is switched according to the determination result of whether or not the vehicle maintenance work starts. However, the present invention is not limited to this. For example, as shown in FIG. 4, the on / off states of the SWs 22 and 23 may be simply switched according to the on / off state of the start SW 15 of the vehicle.
In this case, first, in step S11 shown in FIG. 4, it is determined whether or not the start SW 15 of the vehicle is on.
If this determination is “YES”, the flow proceeds to step S 14 described later.
On the other hand, if this determination is “NO”, the flow proceeds to step S 12.
In step S <b> 12, the maintenance SW (SW <b> 0) 22 is turned off to prohibit current from flowing into the DC power supply 11.
Next, in step S13, the offset power supply SW (SW5) 23 is turned off, prohibiting the formation of the closed circuit L including the offset power supply SW (SW5) 23, and the series of processing ends.
In step S14, the maintenance SW (SW0) 22 is turned on.
Next, in step S15, the offset power supply SW (SW5) 23 is turned on.
Next, in step S16, the execution of the cell voltage detection process is started and the series of processes is terminated.
In the above-described embodiment, instead of the start SW 15, for example, a parking switch for instructing the stop state of the vehicle, a sensor for detecting the open / close state of the vehicle door, or the like may be used.

  In the embodiment described above, the open / close state of the maintenance SW 22 is controlled by the control device 14. However, the present invention is not limited to this, and the maintenance SW 22 may be, for example, an opening of a casing in which the DC power supply 11 is accommodated. A switch that automatically shuts off the circuit in conjunction with an appropriate state related to the start of maintenance work may be used.

It is a lineblock diagram of vehicles carrying a voltage detection device of direct-current power supply concerning one embodiment of the present invention. It is a figure which shows an example of the closed circuit L formed in the voltage detection apparatus of the DC power supply shown in FIG. It is a flowchart which shows operation | movement of the voltage detection apparatus of the DC power supply shown in FIG. It is a flowchart which shows operation | movement of the voltage detection apparatus of the DC power supply which concerns on the modification of this embodiment.

Explanation of symbols

10 DC power supply voltage detection device 11 DC power supply 15 Start SW (start switch)
22 Maintenance SW (switch between unit cells)
23 Offset power switch (offset power cutoff switch)
24 Offset power source Step S02, Step S03 Opening means Step S05, Step S06, Step S14, Step S15 Connection means

Claims (2)

A DC power supply voltage detection device comprising: a DC power supply in which a plurality of unit cells are connected in series; and a flying capacitor circuit that detects a voltage between terminals of each unit cell of the DC power supply,
An offset power source connected to a position on the lowest potential side of the DC power source and applying a predetermined bias voltage to a terminal of the unit cell on the lowest potential side of the DC power source;
An inter-unit cell switch that is connected in series in the DC power supply and that cuts off a connection between adjacent unit cells;
An offset power cutoff switch that cuts off the connection between the position of the lowest potential side of the DC power source and the offset power source,
An apparatus for detecting a voltage of a DC power supply, comprising: open means for setting the inter-unit cell switch and the offset power cut-off switch to an open state when performing maintenance work related to the DC power supply. The voltage detection device of the DC power supply is mounted on a vehicle,
2. The direct current according to claim 1, further comprising connection means for setting the inter-unit cell switch and the offset power cutoff switch to a connected state when a start switch for instructing start of the vehicle is in an on state. Power supply voltage detection device.

Images