JP2011007554A - Wire break detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wire break detector at a low cost for detecting a break in an electric path.SOLUTION: A switch element SWn is on-controlled by a control circuit to discharge a capacitor C10n, nulling a voltage across it, and thereafter the switch element SWn is off-controlled. Further, after a first predetermined time Tc1 has elapsed, and after a second predetermined time Tc2 has elapsed, voltages V1 and V2 across the capacitor C10n are measured to find V1/V2. When the found V1/V2 is equal to or less than 0.5, a break is detected.

Description

  The present invention relates to a disconnection detecting device, and in particular, detects disconnection of an electric circuit connecting both ends of a plurality of unit cells connected in series with each other and voltage detecting means for detecting a voltage between both ends of the unit cell. The present invention relates to a disconnection detection device.

  In recent years, hybrid vehicles (hereinafter referred to as HEVs) that travel using both an engine and an electric motor have become widespread. The HEV includes two types of batteries, a low voltage battery of about 12V for starting the engine and a high voltage battery for driving an electric motor. The high voltage battery described above obtains a high voltage by connecting a plurality of unit cells in series with a secondary battery such as a nickel-hydrogen battery or a lithium battery as a unit cell.

  In the above-described high voltage battery, the voltage across the unit cell, that is, the state of charge (SOC) varies as charging and discharging are repeated. When charging / discharging the battery, from the viewpoint of ensuring the durability and safety of each unit cell, charging is prohibited when the unit cell with the highest SOC (or both-ends voltage) reaches the set upper limit SOC (or upper-end voltage value). However, it is necessary to inhibit discharge when the unit cell having the lowest SOC (or both-ends voltage) reaches the set lower limit SOC (or lower-end both-ends voltage value). Therefore, when SOC variation occurs in each unit cell, the usable capacity of the battery is substantially reduced. For this reason, in HEV, so-called assist / regeneration, which replenishes energy with an electric motor to a gasoline engine when climbing, or regenerates energy to a high-voltage battery when descending a slope, becomes insufficient, and actual vehicle power performance and fuel efficiency are reduced. Will be reduced. Therefore, in order to equalize the SOC of each unit cell, it is necessary to detect the voltage across each unit cell.

  Conventionally, both ends of each unit cell are connected to a voltage detection IC as voltage detection means, and the voltage across each unit cell is detected by the voltage detection IC. However, if the electric circuit that connects the unit cell and the voltage detection IC is disconnected, the potential on the electric circuit side that is disconnected due to the internal impedance of the voltage detection IC becomes unstable. For this reason, there has been a problem that the voltage across the unit cell cannot be detected accurately.

  Therefore, a bypass circuit composed of a bypass resistor and a switching element that turns on and off the energization of the bypass resistor is connected in parallel to the unit cell, and the voltage across the unit cell and the bypass resistor when the energization to the bypass resistor is off are connected. There has been proposed a disconnection detection device that detects disconnection of an electric circuit when a difference between both end voltages of a unit cell when energization is on is large (Patent Document 1).

  However, in the above-described conventional disconnection detection device, it is necessary to provide a bypass resistor in parallel with the unit cell. For this reason, a bypass resistor is required in addition to the noise filter connected between both ends of the unit cell and the voltage detection IC and the discharge resistor for equalizing the unit cell, and the number of parts increases. was there. Further, when the resistance value of either the noise filter resistor or the bypass resistor fluctuates, the detection voltage fluctuates greatly. Therefore, if the resistance value fluctuates, there is a problem in that it causes a false detection.

Japanese Patent No. 3839397

  Then, this invention makes it a subject to provide the disconnection detection apparatus which can detect the disconnection of an electric circuit cheaply.

  The invention according to claim 1, which has been made to solve the above-described problem, is an electric circuit that connects both ends of each of a plurality of unit cells connected in series to each other and a voltage detection unit that detects a voltage between both ends of the unit cell. In the disconnection detecting device for detecting disconnection of each of the plurality of unit cells, a plurality of resistors respectively provided in the electric circuit connecting between both ends of the plurality of unit cells and the voltage detecting means, and each of the unit cells via the resistors A plurality of switch elements connected in parallel to each other, a plurality of capacitors connected in parallel to each of the unit cell and the switch element via the resistor, and discharging the capacitor by turning on the switch element. Switch control means for turning off the switch element after the voltage across the both ends is set to 0, and whether the switch element is turned off by the switch control means. After a lapse of time such that the voltage across the capacitor becomes equal to the voltage across the unit cell when the circuit is normal, and when the circuit is disconnected, the voltage across the capacitor is equal to the voltage across the unit cell. First capacitor voltage measuring means for measuring the voltage across the capacitor before such time elapses; second capacitor voltage measuring means for measuring the voltage across the capacitor after the first capacitor voltage measuring means; A disconnection detecting means for detecting disconnection of the electric circuit based on the voltage across the capacitor measured by the first capacitor voltage measuring means and the second capacitor voltage measuring means, respectively. It exists in the detection device.

  According to the second aspect of the present invention, (the voltage across the capacitor measured by the first capacitor voltage measuring means) / (the voltage across the capacitor measured by the second capacitor voltage measuring means) is less than or equal to the first threshold value. Or when (the voltage across the capacitor measured by the second capacitor voltage measuring means) / (the voltage across the capacitor measured by the first capacitor voltage measuring means) is equal to or greater than the second threshold value. The disconnection detecting device according to claim 1, wherein the disconnection detecting means detects disconnection.

  According to a third aspect of the present invention, the first capacitor voltage measuring unit sets the voltage across the capacitor when a first predetermined time has elapsed after the switch element is turned off by the switch control unit. And the second capacitor voltage measuring means so as to measure the voltage across the capacitor when a second predetermined time longer than the first predetermined time elapses after the switch element is turned off by the switch control means. Is set, and the first predetermined time is longer than 3 × (the charging time constant of the capacitor when the circuit is normal), and 0.4 × (the charging time constant of the capacitor when the circuit is disconnected) Is set to be shorter, the second predetermined time is set to be longer than (the charging time constant of the capacitor when the circuit is disconnected), and the first threshold is 0.5 or less, The disconnection detecting device according to claim 2, wherein the second threshold is set to 2 or more.

  According to a fourth aspect of the present invention, there is provided a disconnection detecting device for detecting disconnection of an electric circuit connecting both ends of each of a plurality of unit cells connected in series with each other and voltage detecting means for detecting a voltage between both ends of the unit cell. A plurality of resistors respectively provided in the electric circuit connecting both ends of the plurality of unit cells and the voltage detection means, and a plurality of switch elements connected in parallel to each of the unit cells via the resistors And a plurality of capacitors connected in parallel to each of the unit cell and the switch element via the resistor, and the capacitor is discharged by controlling the switch element to be on, and the voltage across the capacitor is set to 0. A switch control means for controlling the switch element to turn off, and the switch element when the switch circuit is turned off by the switch control means when the circuit is normal. After a lapse of time such that the voltage across the capacitor becomes equal to the voltage across the unit cell, and when the voltage across the capacitor is disconnected, a time elapses such that the voltage across the capacitor becomes equal to the voltage across the unit cell. Third capacitor voltage measuring means for measuring the voltage across the previous capacitor, and disconnection detecting means for detecting disconnection when the voltage across the capacitor measured by the third capacitor voltage measuring means is smaller than a third threshold. And a disconnection detecting device characterized by comprising:

  According to a fifth aspect of the invention, there is provided the disconnection detecting device according to the fourth aspect, wherein the third threshold value is set to a value smaller than a minimum voltage across the unit cell when normal.

  According to a sixth aspect of the present invention, the third capacitor voltage measuring means sets the voltage across the capacitor to measure when a third predetermined time elapses after the switch element is turned off by the switch control means. The third predetermined time is set to be longer than 3 × (charging time constant of the capacitor when the circuit is normal) and shorter than (charging time constant of the capacitor when the circuit is disconnected). It exists in the disconnection detection apparatus of Claim 5 characterized by the above-mentioned.

  As described above, according to the first aspect of the present invention, when the switch element is turned off when the electric circuit is normal, the capacitor is charged by the unit cell, and the voltage across the capacitor rises in a short time and becomes constant. On the other hand, when the electric circuit is disconnected, when the switch element is turned off, the capacitor is charged by a minute leakage current from the current detection means, so that the voltage across the capacitor rises slowly over time and becomes constant. Therefore, under normal conditions, the voltage across the capacitor measured by the first capacitor voltage measuring means and the voltage across the capacitor measured by the second capacitor voltage measuring means after the first capacitor voltage measuring means are almost the same. Be the same. On the other hand, at the time of disconnection, the voltage across the capacitor measured by the second capacitor voltage measuring means becomes larger than the voltage across the capacitor measured by the first capacitor voltage measuring means. For this reason, the disconnection of the electric circuit can be accurately measured by comparing the voltages across the capacitors respectively measured by the first capacitor voltage measuring means and the second capacitor voltage measuring means. Further, it is possible to detect disconnection using a resistor, a switch element, and a noise filter capacitor that are used to discharge and equalize unit cells. For this reason, an increase in the number of parts can be prevented, and disconnection of the electric circuit can be detected.

  According to the second aspect of the present invention, the disconnection can be detected by simply comparing the voltage across the capacitor measured by the first capacitor voltage measuring means and the second capacitor voltage measuring means.

  According to the third aspect of the invention, the first predetermined time is set to be longer than 3 × (capacitor charging time constant when the electric circuit is normal), whereby the voltage across the capacitor after the first predetermined time has elapsed under normal conditions. Can be made substantially the same as the voltage across the unit cell. Further, the first predetermined time is set shorter than 0.4 × (the charging time constant of the capacitor when the electric circuit is disconnected), and the second predetermined time is set longer than (the charging time constant of the capacitor when the electric circuit is disconnected). By doing so, the voltage across the capacitor measured by the first capacitor voltage measuring means at the time of disconnection is made 0.33 times or less of the voltage across the unit cell, and the voltage across the capacitor measured by the second capacitor voltage measuring means is reduced. The voltage across the unit cell can be 0.632 times or more. Therefore, (the voltage across the capacitor measured by the first capacitor voltage measuring means) / (the voltage across the capacitor measured by the second capacitor voltage measuring means) or (the capacitor measured by the second capacitor voltage measuring means) ) / (The voltage across the capacitor measured by the first capacitor voltage measuring means) can be made to greatly differ between the normal time and the disconnection, so that the disconnection of the electric circuit can be accurately detected.

  According to the invention of claim 4, when the switch circuit is turned off when the electric circuit is normal, the capacitor is charged by the unit cell, and the voltage across the capacitor rises in a short time and becomes constant. On the other hand, when the electric circuit is disconnected, when the switch element is turned off, the capacitor is charged by a minute leakage current from the current detecting means, so that the voltage across the capacitor rises slowly over time and becomes constant. Therefore, under normal conditions, the voltage across the capacitor measured by the third capacitor voltage measuring means is substantially equal to the voltage across the unit cell. On the other hand, at the time of disconnection, the voltage across the capacitor measured by the third capacitor voltage measuring means is smaller than the voltage across the unit cell. For this reason, the disconnection of the electric circuit can be accurately measured by comparing the voltage across the capacitor measured by the third capacitor voltage measuring means with the third threshold value. Further, it is possible to detect disconnection using a resistor, a switch element, and a noise filter capacitor used for discharging and equalizing unit cells. For this reason, an increase in the number of parts can be prevented, and disconnection of the electric circuit can be detected.

  According to the invention described in claim 5, by setting the second threshold value to a value smaller than the normal minimum voltage across the unit cell, the disconnection can be accurately detected even if the voltage across the unit cell varies. Can do.

  According to the sixth aspect of the present invention, the voltage across the capacitor after the third predetermined time has passed can be surely set to a value smaller than the minimum voltage across the unit cell when it is disconnected. Can be detected.

It is a circuit diagram showing one embodiment of a voltage detection device incorporating a disconnection detection device of the present invention. FIG. 2 is a circuit diagram showing details of the voltage detection IC shown in FIG. 1. FIG. 2 is a detailed electrical connection diagram when using a photocoupler as the first insulating I / F shown in FIG. 1. FIG. 3 is a detailed electrical connection diagram when using a photocoupler as the second insulation I / F shown in FIG. 1. FIG. 2 is a detailed circuit diagram between unit cells BT _{1 to} BT ₁₁ and a voltage detection IC 11 shown in FIG. (A) is a circuit diagram which shows the charging current at the time of normal, (B) is a circuit diagram which shows the charging current at the time of a disconnection. It is a time chart which shows the both-ends voltage of a capacitor at the time of normal time and a time of disconnection for explaining operation of a 1st embodiment. It is a flowchart which shows the disconnection detection processing procedure of the control circuit shown in FIG. 2 in 1st Embodiment. It is a time chart which shows the both-ends voltage of a capacitor at the time of normal time and a time of disconnection for explaining operation of a 2nd embodiment. It is a flowchart which shows the disconnection detection processing procedure of the control circuit shown in FIG. 2 in 2nd Embodiment.

First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In the present embodiment, the voltage detection device is mounted on a vehicle. The reference sign _BL in FIG. 1 is a low voltage battery. As shown in FIG. 1, the low-voltage battery _BL is composed of a plurality of secondary batteries. The low-voltage battery _BL is used as a drive power source for a starter that starts the engine, and a high-voltage battery is connected to both ends of the low-voltage battery _BL as a charger via a DC / DC converter as necessary.

In FIG. 1, reference symbol B _H is a high voltage battery. The high-voltage battery B _H is used as a power source of the electric motor in an HEV that uses both the engine and the electric motor as a travel drive source. Both ends of the high-voltage battery B _H are connected as a load as needed and a generator (generator ) Etc. are connected as a charger if necessary.

The high voltage battery _BH is divided into, for example, five blocks B1 to B5. Each block B1~B5 are each composed for example 11 pieces of unit cells _{BT 1 ~BT 11, BT 12 ~BT} 22, BT 23 ~BT 33, BT 34 ~BT 44, BT 45 ~BT 55. Each of the unit cells BT _{1 to} BT ₅₅ is composed of one secondary battery.

The voltage detection device includes a main microcomputer 10 as switch control means and voltage detection ICs 11 to 15 as voltage detection means. The main microcomputer 10 is composed of a well-known CPU, ROM, RAM, and the like, operates by receiving power supply from the low-voltage power supply circuit 20, and controls the voltage detection ICs 11-15. The low-voltage power supply circuit 20 generates the operating voltage VC of the main microcomputer 10 from the supply voltage of the low-voltage battery _BL .

The voltage detection ICs 11 to 15 are provided corresponding to the blocks B1 to B5. As shown in FIG. 2, the voltage detection ICs _{11 to} 15 are unit cells BT _{1 to} BT ₁₁ , BT _{12 to} BT ₂₂ , and BT _{23 to} BT ₃₃ that constitute the corresponding blocks B _{1 to} B 5 among the plurality of blocks B _{1 to} B 5. , BT _{34 to} BT ₄₄ and BT _{45 to} BT ₅₅ are operated by receiving power supply only. That is, in the voltage detection ICs 11 to 15 described above, the negative sides of the corresponding blocks B1 to B5 are at the ground level, and are at different ground levels. Thereby, the breakdown voltage of the devices constituting the voltage detection ICs 11 to 15 can be lowered.

Each of the voltage detection ICs 11 to 15 includes a selection switch group 16, a differential amplifier OP, an A / D converter 17, a control circuit 18, a high-voltage power supply circuit 19, and a cutoff switch S. The selection switch group 16 includes normally open switches provided at both ends of the unit cells BT _{1 to} BT ₅₅ , and one end of each of the plurality of unit cells BT _{1 to} BT ₅₅ serves as a differential amplifier OP. Connecting. The differential amplifier OP outputs the voltage across the unit cells BT _{1 to} BT ₅₅ connected by the selection switch group 16 to the A / D converter 17. The A / D converter 17 digitally converts the voltage across the unit cells BT _{1 to} BT ₅₅ from the differential amplifier OP and outputs the converted voltage to the control circuit 18.

  The control circuit 18 includes a well-known CPU, ROM, RAM, and the like, and controls the entire voltage detection ICs 11 to 15. The high voltage power supply circuit 19 generates the operating voltage Vcc of the differential amplifier OP, the A / D converter 17 and the control circuit 18 from the supply voltages of the corresponding blocks B1 to B5. The cutoff switch S is provided between the positive side of each of the blocks B1 to B5 and the high-voltage power supply circuit 19. The cutoff switch S is a switch that turns on / off the supply of the voltage across the blocks B1 to B5 to the high-voltage power supply circuit 19 and turns on / off the power supply to the voltage detection ICs 11-15. The cutoff switch S is composed of, for example, a PNP type transistor.

  Further, as shown in FIG. 1 and the like, the voltage detection device described above includes a first transmission line LT1 and a first reception line LR1 as a first communication line, and a first insulation interface (I / F) 21. And. The first transmission line LT1 and the first reception line LR1 are provided so as to connect the voltage detection ICs 11 to 15 in series with each other. Since the voltage detection ICs 11 to 15 have different ground levels, it is necessary to provide level shift circuits (not shown) on the first transmission line LT1 and the first reception line LR1 provided between the voltage detection ICs 11 to 15. is there.

  Further, the first transmission line LT1 and the first reception line LR1 are provided so as to connect between the lowest voltage detection IC 11 and the main microcomputer 10 among the voltage detection ICs 11-15. That is, in the first transmission line LT1 and the first reception line LR1, the main microcomputer 10, the voltage detection IC 11, the voltage detection IC 12, the voltage detection IC 13, the voltage detection IC 14, and the voltage detection IC 15 are connected in series in this order. It is provided as follows.

The first insulation I / F 21 is provided on the first transmission line LT1 and the first reception line LR1 provided between the lowest voltage detection IC 11 and the main microcomputer 10, and is connected to the voltage detection IC 11 and the main microcomputer. 10 in an electrically insulated state. The lowest voltage detection IC 11 and the main microcomputer 10 can transmit and receive information while being insulated from each other by the first insulation I / F 21. Thereby, the insulation of the high voltage battery _BH and the low voltage battery _BL can be maintained. As the first insulating I / F 21, for example, a light medium such as a photocoupler including a light emitting element and a light receiving element, and a magnetic medium such as a magnetic coupler are known.

  FIG. 3 shows a detailed electrical connection diagram of the voltage detection device shown in FIG. 1 when a photocoupler is used as the first insulation I / F 21. In the figure, details of the voltage detection IC 11 are omitted. As shown in the figure, the first insulation I / F 21 includes a light emitting element LE1 and a light receiving element LD2 provided in the low voltage side system, and a light emitting element LE2 and a light receiving element LD1 provided in the high voltage side system. is doing. As shown in the drawing, the light emitting element LE1 has one end connected to the main microcomputer 10 and the other end connected to the ground. When an electric signal is output from the main microcomputer 10, a current flows and emits light.

On the other hand, the light receiving element LD1 is provided between the negative side of the high-voltage power supply circuit 19 and the unit cell BT ₁ block B1. The light receiving element LD1 is turned on when receiving light from the light emitting element LE1, and supplies an electric signal to the control circuit 18 through the first transmission line LT1. According to the above configuration, an electrical signal can be transmitted to the control circuit 18 of the block B1 while being electrically insulated from the main microcomputer 10.

Further, the light emitting element LE2 has one end connected to the control circuit 18, the other end is connected to the negative side of the unit cell BT _1, the electrical signal is an output current to emit light flows from the control circuit 18. On the other hand, the light receiving element LD2 is provided between the low-voltage power supply circuit 20 and the ground. The light receiving element LD2 is turned on when receiving light from the light emitting element LE2, and supplies an electric signal to the main microcomputer 10 through the first receiving line LR1. According to the above configuration, an electrical signal can be transmitted to the main microcomputer 10 while being electrically insulated from the control circuit 18 of the block B1.

  In addition, as shown in FIG. 1 and the like, the voltage detection device described above includes a second transmission line LT2 as a second communication line, a second insulation I / F 22, on / off I / Fs 31 to 35, Thus, the cut-off switch S can be turned on in accordance with the output of the power signal from the main microcomputer 10. That is, the second transmission line LT <b> 2 is provided between the base of the NPN transistor constituting each cutoff switch S and the main microcomputer 10. The second transmission line LT2 includes a main line Ls having one end connected to the main microcomputer 10 side and a plurality of branch lines Lb1 to Lb5 branched from the other end of the main line Ls. As shown in FIG. 4, the other ends of the branch lines Lb <b> 1 to Lb <b> 5 are connected to the base of a PNP transistor that constitutes the cutoff switch S.

As shown in FIG. 1, the second insulation I / F 22 is provided on the main line Ls, and couples the cutoff switch S and the main microcomputer 10 in an electrically insulated state. Thereby, the insulation of the high voltage battery _BH and the low voltage battery _BL can be maintained. As the second insulation I / F 22, for example, a light medium such as a photocoupler composed of a light emitting element and a light receiving element or a magnetic medium such as a magnetic coupler is known. The on / off I / Fs 31 to 35 are provided corresponding to the branch lines lb1 to lb5, and convert the power signal transmitted from the main microcomputer 10 into an appropriate signal level for turning on / off the cutoff switch S. To do.

  Next, with reference to FIG. 4, the detailed configuration of the second transmission line LT2, the second insulation I / F 22, and the on / off I / Fs 31 to 35 as the second communication line described above. explain. As shown in the figure, the second insulation I / F 22 includes a light emitting element LE3 provided in the low pressure side system and a light receiving element LD3 provided in the low pressure side system. As shown in the drawing, the light emitting element LE3 has one end connected to the main microcomputer 10 and the other end connected to the ground. When a power signal is output from the main microcomputer 10, a current flows and emits light.

  On the other hand, one end of the light receiving element LD3 is connected to the plus side of the uppermost block B5, and the other end is connected to the minus side of the lowermost block B1 via voltage dividing resistors R1 to R6. The contact point between the voltage dividing resistor R1 and the voltage dividing resistor R2 is connected to the base of an NPN transistor that constitutes the on / off I / F 31. A contact point between the voltage dividing resistor R2 and the voltage dividing resistor R3 is connected to the base of an NPN transistor that constitutes the on / off I / F 32. A contact point between the voltage dividing resistor R3 and the voltage dividing resistor R4 is connected to the base of an NPN transistor that constitutes the on / off I / F 33. A contact point between the voltage dividing resistor R4 and the voltage dividing resistor R5 is connected to the base of the NPN transistor that constitutes the on / off I / F. A contact point between the voltage dividing resistor R5 and the voltage dividing resistor R6 is connected to a base of an NPN transistor that constitutes an on / off I / F 35.

  The emitters of the NPN transistors constituting the on / off I / Fs 31 to 35 are connected to the negative side of the blocks B1 to B5. The collectors of the NPN transistors constituting the on / off I / Fs 31 to 35 are connected to the bases of the PNP transistors constituting the cutoff switch S. According to the above configuration, when the main microcomputer 10 supplies a power signal to the light emitting element LE3, the power flows to the light emitting element LE3 to emit light. When the light from the light emitting element LE3 is received, the light receiving element LD3 is turned on. When the light receiving element LD3 is turned on, the NPN transistors constituting the on / off I / Fs 31 to 35 are turned on. Then, in response to the on / off I / F 31 being turned on, the PNP transistors constituting the cutoff switch S are turned on, and power is supplied to the voltage detection ICs 11 to 15. That is, the power supply of each voltage detection IC 11 to 15 can be controlled by supplying a power signal from the main microcomputer 10.

Next, the configuration of the disconnection detection device 30 incorporated in the voltage detection device described above will be described with reference to FIG. The disconnection detection device 30 is a device that detects disconnection of an electric circuit that connects both ends of each of the unit cells BT _{1 to} BT ₅₅ described above and the voltage detection ICs 11 to 15. As shown in the figure, in the block B1, the disconnection detection device 30 includes resistors R100 to R111, a plurality of switch elements SW1 to SW11, and a plurality of capacitors C101 to C111.

A plurality of resistors R100~R111 are respectively provided between the ends and the voltage detection IC11 of a plurality of unit cells BT ₁ to BT _11. Connection portions of the unit cells BT _{1 to} BT ₁₁ adjacent to each other are connected to the voltage detection IC 11 via common resistors R100 to R111. Therefore, the resistance R100~R111 are provided several +1 unit cells BT ₁ to BT _11. The plurality of switch elements SW1 to SW11 are connected in parallel to each of the unit cells BT _{1 to} BT ₁₁ via the resistors R100 to R111.

A plurality of capacitors C101~C111 are connected in parallel to each of the unit cells BT ₁ to BT ₁₁ via the resistor R100～R111. It said plurality of switch elements SW1~SW11 and capacitor C101~C111 are provided as many as unit cells BT ₁ to BT _11. The voltage across the unit cells BT _{1 to} BT ₁₁ is composed of the resistors R100 to R111 provided at both ends of the unit cells BT _{1 to} BT ₁₁ and the capacitors C101 to C111 connected in parallel to the unit cells BT _{1 to} BT ₁₁ . The noise filter circuit which removes a noise component from is comprised. Further, the above resistance R100～R111, constitutes a bypass circuit for discharging switching element SW1～SW11, in the unit cell BT ₁ to BT _11. Evenly That is, by discharging the unit cell BT ₁ to BT ₁₁ turns on the switching element SW1~SW11 corresponding to high unit cell BT ₁ to BT ₁₁ is the voltage across the voltage across the unit cell BT ₁ to BT ₁₁ Can be Further, since the blocks B2 to B5 have the same configuration as the block B1, detailed description thereof is omitted here.

Next, the disconnection detection principle of the disconnection detection device 30 incorporated in the voltage detection device described above will be described with reference to FIGS. For simplicity, only the block B1 connected to the voltage detection IC 11 will be described, but the same applies to the blocks B2 to B5. When the switch element SWn (n is an arbitrary integer) is turned on, the capacitor C10n connected in parallel to the switch element SWn is discharged, and the voltage across the capacitor C10n becomes zero. Thereafter, when the off SWn switching element, as shown in FIG. 6 (A), in the normal disconnection has not occurred, the charging current i1 from the unit cell BT _n is supplied to the capacitor C10n through the resistor R10n Capacitor C10n is charged. Thus, as shown by the solid line in FIG. 7, the voltage across the capacitor C10n is constant retains its voltage when a short time rises reach across voltage E of the unit cell BT _n.

On the other hand, as shown in FIG. 6B, when the electric circuit connecting the one end of the positive side of the unit cell BT _n and the voltage detection IC 11 is disconnected, if the switch element SWn is turned off, the voltage detection IC 11 The capacitor C10n is charged by the minute leakage current i2. As a result, as shown by the one-dot chain line in FIG. 7, the voltage across the capacitor C10n becomes constant after slowly rising over time.

In more detail, since at the normal time in which the charging current i1 from the unit cell BT _n is charged to the capacitor C10n through a resistor R10n, capacitor C10n is charged with a time constant determined by the resistor R10n and capacitor C10n . On the other hand, since the capacitor C10n is charged by the leakage current i2 from the voltage detection IC11 at the time of disconnection, the capacitor C10n is charged with a time constant determined by the internal impedance of the voltage detection IC11 and the capacitor C10n.

  The resistors R100 to R111 described above are set smaller than the internal impedance of the voltage detection IC 11. For example, when the internal impedance of the voltage detection IC 11 is 100 kΩ or more, the resistors R100 to R111 are set to several hundred Ω or less. Therefore, since the charging time constant of the capacitor C10n at the normal time is smaller than the charging time constant of the capacitor C10n at the time of disconnection, as shown in FIG. The voltage rises and becomes constant in a short time compared to the voltage across the capacitor C10n.

Now, such a from a voltage across the capacitor C10n when disconnection charging the capacitor C10n has not been turned off controlling SWn switching element during normal operation which occurs zero to substantially equal to the voltage across the unit cell BT _n times T1, When the switch element SWn is controlled to be off at the time of disconnection and the capacitor C10n is charged, the time required for the voltage across the capacitor C10n to become substantially equal to the voltage across the unit cell BTn is defined as T2.

  As shown in FIG. 7, the charging time after the switch element SWn is turned off is longer than the time T1 and shorter than the time T2, and in the normal time when no disconnection occurs, the capacitor C10n The voltage at both ends hardly changes. On the other hand, when the disconnection occurs, the voltage across the capacitor C10n gradually increases as the charging time elapses. Therefore, the rate of change of the voltage across the capacitor C10n in the period T3 was obtained, and it was found that it can be detected as normal if there is little change, and disconnected if there is a large change.

  Specifically, the voltage V1 across the capacitor C10n when the first predetermined time Tc1 set within the period T3 has elapsed after the switch element SWn is turned off, and the first predetermined value after the switch element SWn is turned off. The voltage V2 across the capacitor C10n when a second predetermined time Tc2 longer than the time Tc1 has elapsed is measured to determine the rate of change V1 / V2 of the voltage across the capacitor C10n, and the obtained rate of change V1 / V2 is A disconnection can be detected when the threshold is 1 or less.

  If the first predetermined time Tc1 is set as close as possible to the time T1, and the second predetermined time Tc2 is set as close as possible to the time T2, the change rate V1 / V2 at the time of non-disconnection is reduced. The rate of change V1 / V2 can be greatly different between the normal time and the disconnection, and the disconnection can be detected more accurately.

Next, the setting of the first predetermined time Tc1 and the second predetermined time Tc2 will be described in detail. Now, the charging time constant of the capacitor C10n at the time of disconnection determined by the internal impedance of the voltage detection IC 11 and the capacitor C10n is τ1, and the charging time constant of the capacitor C10n at the normal time determined by the resistor R10n and the capacitor C10n is τ2. . As is apparent from FIG. 7, the the elapsed time constant τ1 or from OFF control SWn switching element, the voltage across the capacitor C10n the above 0.632 times the voltage across E of the unit cell BT _n during disconnection .

On the other hand, in the prior off control SWn switching element to 0.4 × time constant τ1 elapses from the time of disconnection, the voltage across the capacitor C10n is below 0.33 times the voltage across E of the unit cell BT _n. Further, it is known that the above-described time T1 is substantially equal to three times the time constant τ2 (∵3 × τ2≈T1). Therefore, if the first predetermined time Tc1 is set to be longer than 3 × time constant τ2 and shorter than 0.4 × time constant τ1, and the second predetermined time Tc2 is set to be shorter than time constant τ1, the above-mentioned at the time of disconnection The change rate V1 / V2 can be 0.5 (≈0.33 / 0.632) or less. Therefore, if the change rate V1 / V2 is 0.5 (first threshold value) or less, it is determined that the wire is disconnected, and if it is higher than 0.5, it can be determined that it is normal.

Based on the above-described disconnection detection principle, disconnection detection processing of the voltage detection device will be described with reference to FIG. In the disconnection detection process, first, the control circuit 18 sets n to 1 (step S1). Next, the control circuit 18 turns on the switch element SWn (step S2). The control circuit 18 waits for the time Td to elapse after the ON control (Y in Step S3), and controls the switch element SWn to OFF (Step S4). The time Td is set such that the capacitor C10n is discharged after the switch element SWn is turned on and the voltage across the terminals becomes zero. Therefore, the voltage across the capacitor C10n is 0 immediately after the switch element SWn is turned off in step S4. Then, the capacitor C10n by OFF control of SWn switching element, the voltage across it is charged by the leakage current i2 from the charging current i1 or voltage detection IC11 from the unit cell BT _n is increased from zero. As is apparent from the above, the control circuit 18 functions as a switch control unit in steps S2 to S4.

Next, the control circuit 18 controls the switch element SWn to be turned off, and then, as shown in FIG. 7, the first predetermined time set to be longer than 3 × time constant τ2 and shorter than 0.4 × time constant τ1. Waiting for Tc1 to elapse (Y in step S5), it functions as a first capacitor voltage measuring means, measures the voltage across the capacitor C10n, and stores it in the RAM as the voltage V1 across the capacitor (step S6). That is, the control circuit 18, both ends of the unit cell BT _n by controlling the selection switch group 16, i.e., connecting the voltage across the capacitor C10n to the differential amplifier OP. As a result, the voltage across the capacitor C10n is supplied from the differential amplifier OP to the control circuit 18 via the A / D converter 17.

The control circuit 18 takes in the supplied voltage across the capacitor C10n and stores it in a RAM (not shown) as a voltage V1 across the capacitor C10n. After that, the control circuit 18 turns off the switch element SWn and waits for a second predetermined time Tc2 set longer than the time constant τ1, as shown in FIG. 7, (Y in step S7), It functions as a second capacitor voltage measuring means, measures the voltage across the capacitor C10n, and stores it in the RAM as the voltage V2 across the capacitor (step S8). Thereafter, the control circuit 18 functions as a disconnection detection means, obtains the change rate (V1 / V2), and if the obtained change rate (V1 / V2) is 0.5 or less (Y in step 9), the unit cell. It is determined that the electric circuit connecting BT _n and the voltage detection IC 11 is disconnected, and the fact is stored in the RAM as a disconnection detection result (step S10).

In contrast, the control circuit 18, if the determined change rate (V1 / V2) is greater than 0.5 (in step S9 N), path for connecting the unit cells BT _n and the voltage detection IC11 is normal It is determined that there is, and the fact is stored in the RAM as a disconnection detection result (step S11). Next, the control circuit 18 determines whether n has reached 11 (step S12). If n has not reached 11 (N in Step S12), the control circuit 18 increments n (Step S13) and then returns to Step S2.

On the other hand, if n has reached 11 (Y in step S11), the control circuit 18 finishes detecting the disconnection of the electric circuit between all the unit cells BT _{1 to} BT ₁₁ and the voltage detection IC ₁₁ constituting the block B1. After determining that the disconnection detection result stored in the RAM in steps 10 and S11 is transmitted to the main microcomputer 10 (step S14), the process is terminated. Similarly, the control circuit 18 of the blocks B2 to B5 performs the disconnection detection process. When the main microcomputer 10 receives the disconnection detection result of each of the blocks B1 to B5 and determines that there is a disconnection, the main microcomputer 10 notifies the fact.

According to the first embodiment described above, the control circuit 18 controls the switch element SWn to be turned off after discharging the capacitor C10n by setting the switch element SWn to be turned on to reduce the voltage across the capacitor C10n. The control circuit 18 measures the voltage V1, V2 across the capacitor C10n after the first predetermined time Tc1 and the second predetermined time Tc2 (> Tc1) after the switch element SWn is turned off, and the rate of change (V1 / V1). V2) is obtained, and disconnection is detected when the obtained rate of change (V1 / V2) is 0.5 or less. Thus, the unit cells BT ₁ to BT discharged is used to equalize the resistance to ₅₅ R100～R111 and switching element SW1～SW11, be performed disconnection detected using capacitors C101~C111 for noise filter it can. For this reason, the disconnection detection apparatus which can prevent the increase in a number of parts and can detect the disconnection of an electric circuit can be proposed cheaply.

Further, according to the first embodiment described above, the first predetermined time Tc1 is set longer than 3 × time constant τ2. This makes it possible to substantially equal to the first voltage across the predetermined voltage across the unit cell of the capacitor C10n time Tc1 after BT _n in normal. Further, the first predetermined time Tc1 is set shorter than 0.4 × time constant τ1, and the second predetermined time Tc2 is set longer than time constant τ1. Thus, the voltage across the capacitor C10n after the first predetermined time Tc1 elapses below 0.33 times the voltage across E of the unit cell BT _n during disconnection, both ends of the unit cell BT _n after the second predetermined time Tc2 elapses The voltage E can be 0.632 times or more. Therefore, since the change rate V1 / V2 can be greatly different between the normal time and the disconnection, the disconnection of the electric circuit can be accurately detected.

  In the first embodiment described above, 0.5 is set as the first threshold, but the present invention is not limited to this. When 3 × time constant τ 2 <first predetermined time Tc 1 <0.4 × time constant τ 1 and time constant τ 1 <second predetermined time Tc 2, the first threshold may be set to 0.5 or less.

  In the first embodiment described above, the disconnection is detected when the rate of change (V1 / V2) is 0.5 (first threshold) or less, but the present invention is not limited to this. For example, the disconnection may be detected when the rate of change (V2 / V1) is equal to or greater than the second threshold. In this case, similarly to the first embodiment, if 3 × time constant τ2 <first predetermined time Tc1 <0.4 × time constant τ1, and time constant τ1 <second predetermined time Tc2, the rate of change (V2 at the time of disconnection) Since / V1) is 2 or more, 2 or more can be set as the second threshold.

Second Embodiment Next, a second embodiment of the present invention will be described. Since the configuration of the voltage detection apparatus in the second embodiment is the same as that of the first embodiment, a detailed description thereof is omitted. First, the disconnection detection principle of the disconnection detection device 30 incorporated in the voltage detection device described above will be described with reference to FIG. For simplicity, only the block B1 connected to the voltage detection IC 11 will be described, but the same applies to the blocks B2 to B5.

  In the first embodiment described above, the disconnection is detected based on the change rate (V1 / V2) of the voltage across the capacitor C10n. In the second embodiment, the disconnection is detected when the voltage V3 across the capacitor C10n when the third predetermined time Tc3 has elapsed after the switch element SWn is turned off is equal to or lower than the third threshold value. The third predetermined time Tc3 is set longer than 3 × time constant τ2 and shorter than time constant τ1.

Thus setting the third predetermined time Tc3, the voltage across the capacitor C10n after the third predetermined time Tc3 elapsed during disconnection, the following 0.632 times the voltage across E of the unit cell BT _n. The voltage E × 0.632 across the unit cell BT _n is larger than the minimum voltage across the unit cell BTn when it is normal. On the other hand, the voltage across the capacitor C10n after the third predetermined time Tc3 elapsed in normal, since approximately equal to the voltage across the unit cell BT _n, does not fall below the minimum voltage across the normal unit cell BTn. Therefore, as described above, the third predetermined time Tc3 is set longer than 3 × time constant τ2 and shorter than time constant τ1, and the third threshold value is smaller than the minimum voltage across the unit cell BTn at the normal time. Is set, the disconnection can be detected when the both-end voltage V3 is equal to or lower than the third threshold value.

  Next, the disconnection detection process of the voltage detection apparatus in 2nd Embodiment is demonstrated with reference to FIG. Note that steps that are equivalent to the disconnection detection processing already described in the first embodiment described above with reference to FIG. 8 are assigned the same reference numerals, and detailed descriptions thereof are omitted. First, the control circuit 18 proceeds to steps S1 to S4 as in the first embodiment. Next, the control circuit 18 controls to turn off the switch element SWn, and then, as shown in FIG. 10, a third predetermined time Tc3 set longer than 3 × time constant τ2 and shorter than time constant τ1 elapses. (Y in step S15), it functions as a third capacitor voltage measuring means, measures the voltage across the capacitor C10n, and stores it in the RAM as the voltage V3 across the capacitor (step S16).

Thereafter, the control circuit 18, when the voltage across V3 captured below the third threshold value (Y in step S17), determines that the path for connecting the unit cells BT _n and the voltage detection IC11 is broken, that effect Is stored in the RAM as a disconnection detection result (step S10). On the other hand, the control circuit 18 determines that the electric circuit connecting the unit cell BT _n and the voltage detection IC 11 is normal when the captured both-end voltage V3 is larger than the third threshold (N in step S17). (Step S11), the fact is stored in the RAM as a disconnection detection result (Step S12). Hereinafter, since it is the same as that of the first embodiment, a detailed description is omitted here.

In the second embodiment described above, disconnection of the electric circuit is detected based on whether or not the voltage across the capacitor C10n after the third predetermined time Tc3 elapses after the control circuit 18 turns off the switch element SWn is equal to or lower than the third threshold value. is doing. Thus, as in the first embodiment, the resistor is used to equalize to discharge the unit cell BT ₁ ~BT ₅₅ R100~R111 and switching element SW1～SW11, utilizing the capacitor C101~C111 for noise filter Disconnection detection. For this reason, the disconnection detection apparatus which can prevent the increase in a number of parts and can detect the disconnection of an electric circuit can be proposed cheaply.

Further, according to the second embodiment described above, by setting the third threshold value to a value smaller than the minimum voltage across the normal of the unit cell BT _n, also the voltage across the unit cell BT _n fluctuates exactly Disconnection can be detected.

Further, according to the second embodiment described above, the third predetermined time Tc3 is set to be longer than the 3 × time constant τ2 and shorter than the time constant τ1, so that the third predetermined time Tc3 can be reliably established at the time of disconnection. since the voltage across the capacitor C10n after lapse can be a value smaller than the minimum voltage across the normal of the unit cell BT _n, it is possible to detect the disconnection of accurately path.

  Further, the above-described embodiments are merely representative forms of the present invention, and the present invention is not limited to the embodiments. That is, various modifications can be made without departing from the scope of the present invention.

11-15 Voltage detection IC (voltage detection means)
18 Control circuit (switch control means, first capacitor voltage measurement means, second capacitor voltage measurement means, third capacitor voltage measurement means, disconnection detection means)
BT ₁ to BT ₅₅ unit cell C101~C111 capacitor SW1~SW11 switching element

Claims (6)

In the disconnection detecting device for detecting disconnection of the electric circuit connecting the both ends of each of the plurality of unit cells connected in series with each other and the voltage detecting means for detecting the voltage across the unit cells,
A plurality of resistors respectively provided in the electric circuit connecting between both ends of the plurality of unit cells and the voltage detection means;
A plurality of switch elements connected in parallel to each of the unit cells via the resistor;
A plurality of capacitors connected in parallel to each of the unit cell and the switch element via the resistor;
A switch control means for controlling the switch element to be turned off after the capacitor is discharged by setting the switch element to be turned on to reduce the voltage across the capacitor to 0;
After a lapse of time such that the voltage across the capacitor becomes equal to the voltage across the unit cell when the electrical circuit is normal after the switch element is turned off by the switch control means, and when the electrical circuit is disconnected First capacitor voltage measuring means for measuring the voltage across the capacitor before a time has elapsed such that the voltage across the capacitor is equal to the voltage across the unit cell;
Second capacitor voltage measuring means for measuring the voltage across the capacitor after the first capacitor voltage measuring means;
Disconnection detecting means for detecting disconnection of the electric circuit based on the voltage across the capacitor measured by the first capacitor voltage measuring means and the second capacitor voltage measuring means,
A disconnection detecting device comprising: When (the voltage across the capacitor measured by the first capacitor voltage measuring means) / (the voltage across the capacitor measured by the second capacitor voltage measuring means) is equal to or lower than the first threshold, or (the first voltage The voltage across the capacitor measured by the two-capacitor voltage measuring means / (the voltage across the capacitor measured by the first capacitor voltage measuring means) is equal to or higher than the second threshold value, and the disconnection detecting means detects the disconnection. It detects. The disconnection detection apparatus of Claim 1 characterized by the above-mentioned. The first capacitor voltage measuring means is set to measure the voltage across the capacitor when a first predetermined time has elapsed after the switch element is turned off by the switch control means;
The second capacitor voltage measuring means sets the voltage across the capacitor to measure when a second predetermined time longer than the first predetermined time elapses after the switch element is turned off by the switch control means. And
The first predetermined time is set longer than 3 × (charging time constant of the capacitor when the circuit is normal) and shorter than 0.4 × (charging time constant of the capacitor when the circuit is disconnected). ,
The second predetermined time is set to be longer than (the charging time constant of the capacitor when the circuit is disconnected),
The disconnection detection device according to claim 2, wherein the first threshold value is set to 0.5 or less, or the second threshold value is set to 2 or more. In the disconnection detecting device for detecting disconnection of the electric circuit connecting the both ends of each of the plurality of unit cells connected in series with each other and the voltage detecting means for detecting the voltage across the unit cells,
A plurality of resistors respectively provided in the electric circuit connecting between both ends of the plurality of unit cells and the voltage detection means;
A plurality of switch elements connected in parallel to each of the unit cells via the resistor;
A plurality of capacitors connected in parallel to each of the unit cell and the switch element via the resistor;
A switch control means for controlling the switch element to be turned off after the capacitor is discharged by setting the switch element to be turned on to reduce the voltage across the capacitor to 0;
After a lapse of time such that the voltage across the capacitor becomes equal to the voltage across the unit cell when the electrical circuit is normal after the switch element is turned off by the switch control means, and when the electrical circuit is disconnected A third capacitor voltage measuring means for measuring a voltage across the capacitor before a time such that a voltage across the capacitor becomes equal to a voltage across the unit cell;
A disconnection detecting means for detecting a disconnection when a voltage across the capacitor measured by the third capacitor voltage measuring means is smaller than a third threshold;
A disconnection detecting device comprising: The disconnection detecting device according to claim 4, wherein the third threshold is set to a value smaller than a minimum voltage across the unit cell when normal. The third capacitor voltage measuring means is set to measure the voltage across the capacitor when a third predetermined time has elapsed after the switch element is turned off by the switch control means;
The third predetermined time is set to be longer than 3 × (the charging time constant of the capacitor when the electric circuit is normal) and shorter than (the charging time constant of the capacitor when the electric circuit is disconnected). The disconnection detection apparatus according to claim 5, wherein

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