JP5362428B2 - Disconnection detector - Google Patents

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 12 V for starting the engine and a high voltage battery for driving the 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 or 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 both-ends 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 that replenishes energy with an electric motor to a gasoline engine when climbing or regenerates energy to a high-voltage battery when descending is insufficient. 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 wire when a difference between the voltage across the 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 a noise filter connected between both ends of the unit cell and the voltage detection IC and a discharge resistor for equalizing the unit cell, which increases the number of parts. 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

  Therefore, the present invention focuses on the above-described problems, and an object thereof is to provide a disconnection detection device that can detect disconnection of an electric circuit at a low cost.

  In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that an electric circuit for connecting each end of a plurality of unit cells connected in series to each other and a voltage detecting means for detecting a voltage at both ends of the unit cell. In the disconnection detecting device for detecting disconnection, 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, a plurality of capacitors connected in parallel to each of the unit cell and the switch element via the resistor, and a voltage across the capacitor before the switch element is turned on First capacitor voltage measuring means for performing on-control of the switch element to discharge the capacitor and reducing the voltage across the capacitor to zero. Switch control means for controlling off, second capacitor voltage measurement means for measuring a voltage across the capacitor after the switch element is turned off by the switch control means, and first and second capacitor voltage measurement means And a disconnection detecting means for detecting disconnection of the electric circuit based on the voltage across the capacitor measured by the above.

  The invention according to claim 2 is set such that the second capacitor voltage measuring means measures the voltage across the capacitor when a predetermined time has elapsed since the switch element is turned off by the switch control means. The disconnection detecting means compares the voltage across the capacitor measured by the second capacitor voltage measuring means with a threshold value determined according to the voltage across the capacitor measured by the first capacitor voltage measuring means. Is set so as to detect disconnection of the electric circuit, and when the capacitor is charged by controlling the switch element to be off when the electric circuit is normal, the voltage across the capacitor is constant from 0 And when the capacitor is charged by controlling the switch element to be off when the electric circuit is disconnected. And time until the voltage across the serial capacitor becomes constant from 0, consists in breaking detection apparatus according to claim 1 that is characterized in that set between.

  According to a third aspect of the present invention, the predetermined time is a time taken for the voltage across the capacitor to become constant from 0 when the switch element is turned off and the capacitor is charged when the electric circuit is normal. The disconnection detection device according to claim 2, wherein the disconnection detection device is set between a charging time constant of the capacitor at the time of disconnection of the electric circuit.

  The invention according to claim 4 is characterized in that the threshold value is set to 0.63 times or less of the voltage across the capacitor measured by the first capacitor voltage measuring means. It exists in the disconnection detection device.

  According to a fifth aspect of the present invention, the capacitor is charged by controlling the switching element to be off when the electric circuit is normal, with three times the charging time constant of the capacitor when the electric circuit is normal determined by the resistor and the capacitor. 5. The disconnection detection device according to claim 2, wherein the predetermined time is set as a time required for the voltage across the capacitor to become constant from 0 in some cases.

  As described above, according to the first and second aspects of the invention, 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 detection means, so that the voltage across the capacitor rises slowly over time and becomes constant. Therefore, the disconnection of the electric circuit can be accurately measured by measuring the voltage across the capacitor after the switch element is turned off. 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, the disconnection detection apparatus which can prevent the increase in a number of parts and can detect disconnection of an electric circuit can be provided at low cost.

  According to the third aspect of the present invention, the voltage across the capacitor when the predetermined time has elapsed can be made greatly different between when disconnected and when it is normal, so that the disconnection of the electric circuit can be accurately detected.

  According to invention of Claim 4, the disconnection of an electric circuit is correctly detectable.

  According to the fifth aspect of the present invention, when the capacitor is charged by simply turning off the switching element when the electric circuit is normal from the charging time constant of the capacitor, the time taken for the voltage across the capacitor to become constant from 0 is calculated. Can be sought.

It is a schematic circuit diagram which shows one Embodiment of the voltage detection apparatus incorporating the disconnection detection apparatus of this 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 a photocoupler is used as the first insulation I / F shown in FIG. 1. FIG. 5 is a detailed electrical connection diagram when a photocoupler is used 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 disconnection. It is a flowchart which shows the disconnection detection process procedure of the control circuit shown in FIG.

Hereinafter, embodiments 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. In FIG. 1, reference sign _BL 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 apparatus includes a main microcomputer 10 as 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. 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 PNP 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 the sake of 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.

When the switch element SWn is controlled to be off and the capacitor C10n is charged in a normal state where no disconnection occurs, the time taken for the voltage across the capacitor C10n to become constant from 0 is defined as T3, the internal impedance of the voltage detection IC 11 and the capacitor A time constant at the time of disconnection determined by C10n is τ1. As is apparent from FIG. 7, the voltage across the capacitor C10n after elapsed time T3 in the normal is over 0.63 times the voltage across E of reliably unit cell BT _n. On the other hand, when disconnection occurs, the voltage across the capacitor C10n prior time constant τ1 of course, equal to or less than 0.63 times the voltage across E of the unit cell BT _n.

Therefore, the voltage V1 across the capacitor C10n when the predetermined time Tc1 set in the period T4 between the time T3 and the time constant τ1 elapses after the switch element SWn is turned off is _{equal to} the voltage E across the unit cell BTn. if 0.63 (threshold value) or less to detect disconnection, it is possible to detect the normal is greater than 0.63 times the voltage across the voltage V1 across the unit cell BT _n. The above-described time T3 may be obtained experimentally, or the predetermined time Tc1 may be determined with the time T3 being three times the time constant τ2 determined by the resistor R10n and the capacitor C10n in a normal state (∵3 × τ2≈T3). The time constant τ1 can be obtained in advance by measuring the internal impedance of the voltage detection IC 11. Next, let's apply specific numerical values. Now, assuming that the resistance R10n = 100Ω, the capacitor C10n = 0.1 μF, and the internal impedance of the voltage detection IC 11 = 500 kΩ, the time constant τ1 at the time of disconnection and the time constant τ2 at the time of normality are expressed by the following equations (1) and (2). It becomes the value shown.
τ1 = 500 kΩ × 0.1 μF = 0.05 seconds (1)
τ2 = 100Ω × 0.1 μF = 0.00001 seconds (2)
Therefore, the predetermined time Tc1 may be set in the period T4 of 3 × τ2 = 0.00003 seconds or more and τ1 = 0.05 seconds or less.

  Based on the above-described disconnection detection principle, disconnection detection processing of the voltage detection apparatus having the above-described configuration will be described with reference to FIG. First, when switching to disconnection detection processing, the main microcomputer 10 starts processing and transmits a disconnection detection command to the control circuit 18 of the block B1 connected via the first transmission line LT1. This disconnection detection command is sequentially transmitted from the control circuit 18 of the block B1 to the control circuits 18 of the upper blocks B2 to B5 through the first transmission line LT.

When receiving the disconnection detection command, the control circuit 18 of the block B1 performs a disconnection detection process described later. In the disconnection detection process, first, the control circuit 18 sets n to 1 (step S1). Next, the control circuit 18 serves as a first capacitor voltage measuring means measures the voltage across the capacitor C10n, stored in the RAM as a voltage across E of the unit cell BT _n (step S2). Next, the control circuit 18 turns on the switch element SWn (step S3). The control circuit 18 waits for the time T1 to elapse after the ON control (Y in Step S4), and controls the switch element SWn to OFF (Step S5). The time T1 is set to such a time that the capacitor C10n is discharged after the switch element SWn is turned on and the voltage at both ends becomes zero. Therefore, the voltage across the capacitor C10n is 0 immediately after the switch element SWn is turned off in step S5. 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 S3 to S5.

Next, the control circuit 18 waits for a predetermined time Tc1 set in a period T4 between the time T3 and the time τ1 to elapse as shown in FIG. Y in Step S6) acts as a second 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 S7). That is, the control circuit 18, both ends of the unit cell BT _n by controlling the selection switch group 16, i.e., connecting both ends of 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. Thereafter, the control circuit 18 serves as breakage detector, not more than 0.63 times the voltage across E of the voltage V1 across the unit cell BT _n (in step S8 N), the unit cell BT _n and the voltage detection IC11 Is connected to the RAM as a disconnection detection result (step S9).

In contrast, the control circuit 18, electrical path across voltage V1 is greater than 0.63 times the voltage across E of the unit cell BT _n (Y in step S8), and connecting the unit cells BT _n and the voltage detection IC11 Is stored in the RAM as a disconnection detection result (step S10). Next, the control circuit 18 determines whether n has reached 11 (step S11). If n has not reached 11 (N in step S11), the control circuit 18 increments n (step S12), 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 S9 and S10 is transmitted to the main microcomputer 10 (step S13), 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 unit cell BT ₁ to BT discharged is used to equalize the resistance to 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 1 which can prevent the increase in a number of parts and can detect the disconnection of an electric circuit can be provided at low cost.

Further, according to the first embodiment, the control circuit 18 measures the voltage across the capacitor C10n when the predetermined time Tc1 has elapsed since the switch element SWn was turned off, and measured the voltage across the capacitor C10n and the unit. and it detects the disconnection of the electric path on the basis of a comparison between 0.63 times the voltage across E cell BT _n. Thereby, when the predetermined time Tc1 has elapsed after the switch element SWn is turned off, the disconnection can be detected easily and in a short time only by measuring the voltage across the capacitor C10n.

Further, according to the first embodiment, the predetermined time Tc1 is set between the time T3 and the time constant τ1. By setting the predetermined time Tc1 in this way, the voltage across the capacitor C10n when the predetermined time Tc1 elapses can be made greatly different between the disconnected time and the normal time, so that the disconnection of the electric circuit can be accurately detected. Can do. Further, according to the first embodiment described above, the threshold value is set to 0.63 times the voltage across E of the unit cell BT _n. Therefore, the disconnection of the electric circuit can be detected accurately.

According to the first embodiment described above, 0.63 times the voltage E between both ends of the unit cell BT _n is set as the threshold value, but the present invention is not limited to this. The threshold value may be a value that can detect disconnection by paying attention to the fact that the charging time constant of capacitor C10n differs between disconnection and normal.

  Further, according to the above-described embodiment, the predetermined time Tc1 is set to the period T4 between the time T3 and the time constant τ1, but the present invention is not limited to this. As is apparent from FIG. 7, it can be seen that there is a difference in the voltage across the capacitor C10n between the disconnection time and the normal time unless the time T5 is exceeded even if the time constant is longer than τ1. Therefore, the predetermined time Tc1 may be set to a period between the time T3 and the time T5, and may be longer than the time constant τ1.

  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 measurement means, disconnection detection means)
BT _{1 to} BT ₅₅ unit cell C101 to C111 capacitor R100 to R111 resistor SW1 to SW11 switch element

Claims (5)

In the disconnection detecting device for detecting the disconnection of the electric circuit connecting the both ends of the plurality of unit cells connected in series with each other and the voltage detection 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;
First capacitor voltage measuring means for measuring a voltage across the capacitor before turning on the switch element;
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;
Second capacitor voltage measuring means for measuring a voltage across the capacitor after the switch element is turned off by the switch control means;
Disconnection detecting means for detecting disconnection of the electric circuit based on the voltage across the capacitor measured by the first and second capacitor voltage measuring means;
A disconnection detecting device comprising: The second capacitor voltage measuring means is set to measure a voltage across the capacitor when a predetermined time has elapsed since the switch element was turned off by the switch control means;
The disconnection detecting means compares the voltage across the capacitor measured by the second capacitor voltage measuring means with a threshold value determined according to the voltage across the capacitor measured by the first capacitor voltage measuring means. Is set to detect disconnection of the electrical circuit based on
When the predetermined time is normal when the electric circuit is normal and the switch element is turned off to charge the capacitor, the time required for the voltage across the capacitor to become constant from 0 and the switch element when the electric circuit is disconnected 2. The disconnection detecting device according to claim 1, wherein the disconnection detecting device is set between a time until the voltage across the capacitor becomes constant from 0 when the capacitor is charged by controlling off the capacitor. . The predetermined time is the time taken for the voltage across the capacitor to become constant from 0 when the switch element is turned off and the capacitor is charged when the electric circuit is normal, and the capacitor when the electric circuit is disconnected The disconnection detection device according to claim 2, wherein the disconnection detection device is set between The disconnection detecting device according to claim 3, wherein the threshold value is set to 0.63 times or less of a voltage across the capacitor measured by the first capacitor voltage measuring unit. When the capacitor is charged by turning off the switching element when the electric circuit is normal, the voltage across the capacitor is three times the charging time constant of the capacitor when the electric circuit is normal determined by the resistor and the capacitor. The disconnection detecting device according to any one of claims 2 to 4, wherein the predetermined time is set as a time required to become constant from 0.

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