JP5035978B2 - DCDC converter device for vehicle - Google Patents

Description

  The present invention relates to a vehicular DC / DC converter device, and more particularly to a vehicular DC / DC converter device for transferring power between a main battery and an auxiliary battery.

  In a hybrid vehicle, etc., a high voltage main battery to which a generator or a traveling motor is connected, a low voltage auxiliary battery to which a vehicle electrical system or a control system is connected, and the main battery to an auxiliary battery A two-voltage power supply system equipped with a DC-DC converter device for a vehicle that performs power transmission is provided (Patent Document 1). In order to reduce the size and weight or increase the capacity of the main battery, it has been studied and studied to employ a lithium ion battery as the main battery.

  Lithium ion batteries are vulnerable to overcharge and overdischarge, so in lithium ion assembled batteries in which battery cells made of lithium ion batteries are connected in series, an equalization circuit for reducing the voltage difference between the battery cells is provided. It is normal. As this type of equalization circuit, Patent Document 2 proposes a circuit using a switch and a resistance element, and Patent Document 3 proposes a circuit using a switch and a capacitor.

The following patent document 4 filed by the present applicant proposes a two-transform DC-DC converter that operates two transformers in a complementary manner.
Japanese Unexamined Patent Publication No. Sho 62-173901 Japanese Patent No. 3796918 Japanese Patent Laid-Open No. 10-164768 Japanese Patent Laid-Open No. 2006-166550

  However, in the two-voltage type power supply system equipped with the above-described DC / DC converter device for vehicles, if the DC / DC converter device for vehicles becomes defective, power transmission to the auxiliary battery cannot be performed, so that the voltage of the auxiliary battery decreases.

  Further, in the above-described switch / resistance circuit type equalization circuit, the power stored in the high-voltage cell is consumed by the resistance element, so the power is wasted and the temperature rise of the substrate on which the resistance element is mounted is also a problem. became. Furthermore, the switch / capacitor circuit type equalization circuit requires a complicated circuit to transfer the necessary power between the battery blocks, and also requires a large number of times of switching because the stored power of the capacitor is small. It took a long time to equalize.

  The present invention has been made in view of the above problems, and an object thereof is to provide a DCDC converter device for a vehicle that is excellent in reliability and easy to equalize.

The present invention for solving the above-described problems is directed to a DC / DC converter device for a vehicle that transmits electric power from a high-voltage main battery formed by connecting a plurality of battery blocks in series to a low-voltage auxiliary battery in an electrically insulating manner. A plurality of DC / DC converters that separately perform power transmission between each battery block and the auxiliary battery, and a power transmission amount of the plurality of DC / DC converters can be individually controlled. In addition to having a battery state detection unit that determines whether a part of each battery block is defective, and having a plurality of battery blocks connected in series, between the battery block determined to be defective and the auxiliary battery And a controller for stopping the operation of the DC / DC converter. If it does in this way, since charging / discharging of a defective battery block is not performed at the time of power transmission between a main battery and an auxiliary machine battery, overheating and further deterioration of a defective battery block can be prevented.

  In this way, even if one DC-DC converter breaks down, power can be transmitted to the auxiliary battery through the remaining DC-DC converter, so that the important electronic device connected to the auxiliary battery due to the voltage drop of the auxiliary battery For example, it is possible to solve problems such as poor operation of the control device or the like, or a decrease in illumination.

  In addition, each DC-DC converter can independently control power transmission between each battery block of the main battery and the auxiliary battery, so that power transmission from the battery block having a large power storage amount to the auxiliary battery can be reduced. Power transmission from small battery block to auxiliary battery, emergency transmission from battery block with excessive terminal voltage to auxiliary battery, or battery block with excessive terminal voltage from auxiliary battery to auxiliary battery The power transmission can be stopped or the voltage variation between the battery blocks can be reduced. That is, these DC-DC converters can be operated as a kind of equalization circuit. In addition, since the discharge of the main battery is effectively used on the auxiliary battery side, power is not wasted.

  In addition, the battery block can be configured by connecting a plurality of battery cells in series, or may be configured by one battery cell. The DC / DC converter device for a vehicle of the present invention can be applied to a dual voltage power supply system such as a hybrid vehicle, an electric vehicle, and a fuel cell vehicle, and can also be applied to a normal internal combustion locomotive equipped with a dual voltage power supply system. .

  Note that the above power transfer between the battery block having a relatively small full charge capacity and the auxiliary battery can be compensated by the reverse power transfer between the other normal battery block and the auxiliary battery. . By this compensation, the SOC difference between the other normal battery blocks and the relatively small battery blocks described above can be further suppressed.

  In addition, after a battery block with a relatively small full charge capacity reaches full charge at the time of charging, power is transmitted from the battery block with a relatively small full charge capacity to the auxiliary battery, thereby allowing other batteries to Charging the block can be continued. Similarly, after a battery block with a relatively small full charge capacity reaches a minimum SOC value early at the time of discharging, power is transmitted from the auxiliary battery to the battery block with a relatively small full charge capacity. The discharge of the battery block can be continued.

  After all, according to this method, the charge / discharge capacity of the main battery (the SOC range between the maximum SOC value and the minimum SOC value) can be set to exceed that of the battery block having a relatively small full charge capacity. it can.

Further, the present invention provides a DC / DC converter device for a vehicle that transmits power from a high-voltage main battery formed by connecting a plurality of battery blocks in series to a low-voltage auxiliary battery so that the coils N1, N2, N3 are electrically insulated. And a transformer T2 having coils N4, N5, and N6. The coils N1 and N4 are connected in series to form a first coil pair, and the coils N2 and N5 are connected in series to form a second coil pair. The other end of the coil N1 forms an independent terminal (Te1) of the first coil pair, the other end of the coil N2 forms an independent terminal (Te2) of the second coil pair, and the other ends of the coils N4 and N5 A transformer forming a common terminal (Tec) of the first and second coil pairs, and a transistor (Q1) having one end connected to the common terminal (Tec) and the other end connected to the independent terminal (Te2) And a transistor (Q2) having one end connected to the common terminal (Tec) and the other end connected to the independent terminal (Te1) and connected to both ends of the battery block. A first AC / DC conversion circuit that performs AC / DC power conversion by complementary switching of (Q1, Q2), a transistor (Q4) connected in series with the coil N3, and a transistor (Q3) connected in series with the coil N6; One end of both transistors (Q3, Q4) is commonly connected to form a first output terminal, and the other end of both transistors (Q3, Q4) is individually connected to coils N3, N6 to form a second output terminal, A second AC / DC conversion circuit that performs AC / DC power conversion by complementary switching of the transistors (Q3 and Q4), and each of the plurality of battery blocks and the auxiliary battery A plurality of DC / DC converter for performing separate power transmission between the - characterized in that it comprises a separate power transmission amount of motor control can control unit - data and the plurality of DC / DC converter. In this way, the above-described effects can be achieved, and further improvement of efficiency and reduction of current ripple and switching noise can be realized.

  In a preferred embodiment, the independent terminal (Te1) is connected to the other end of the transistor (Q2) through a capacitor (C1), and the independent terminal (Te2) is connected to the other of the transistor (Q1) through a capacitor (C2). Connected to the end. In this way, it is possible to reduce the ripple voltage associated with the switching transistor (Q1) and the switching transistor (Q2) intermittently, and from the battery block even if the switching transistor (Q1) and the switching transistor (Q2) are turned on. Since the direct current can be prevented from flowing to the transformer, the reliability is improved.

  A preferred embodiment of the present invention applied to a hybrid vehicle will be described with reference to the following examples.

(Circuit configuration)
The electric system of the hybrid vehicle of this embodiment will be described with reference to FIG. 1 is a high voltage main battery formed by connecting a number of battery blocks in series, 2 is an auxiliary battery power supply device (vehicle DC-DC converter device in the present invention), 3 is a smoothing capacitor, and 4 is an auxiliary device for the vehicle. A battery 5 is a control device including a microcomputer.

  Although eight battery blocks 11 to 18 are illustrated in FIG. 1 as battery blocks constituting the main battery 1 made of an assembled battery, the number of battery blocks connected in series is arbitrary. In this embodiment, one battery block is configured by connecting eight lithium secondary battery cells in series, but this is also optional. The main battery 1 is connected to a generator (not shown) and a high voltage electric load.

  The auxiliary battery power supply device 2 includes a total of eight bidirectional DC-DC converters 21 to 28, and the bidirectional DC-DC converters 21 to 28 include the battery blocks 11 to 18 and the auxiliary battery 4. Each is connected so that bidirectional power can be exchanged. The smoothing capacitor 3 is connected in parallel to the auxiliary battery 4 and absorbs output voltage ripples of the bidirectional DC-DC converters 21 to 28.

  The auxiliary battery power supply device 2 supplies power from the main battery 1 to the auxiliary battery 4 and a low-voltage electric load (not shown) connected thereto, but the power supply capability of the main battery 1 is insufficient for some reason. In this case, the low voltage power input from the auxiliary battery 4 is boosted to supply power to the main battery 1. This kind of auxiliary battery power supply device 2 provided in a two power supply system for a vehicle so that power can be supplied in both directions is known. Note that each of the bidirectional DC-DC converters 21 to 28 of the auxiliary battery power supply device 2 may be configured by a unidirectional DC-DC converter that only supplies power from the main battery 1 to the auxiliary battery 4.

  The control device 5 executes power transmission between the main battery 1 and the auxiliary battery 4 by controlling the auxiliary battery power supply device 2 based on the terminal voltage of the main battery 1 or the auxiliary battery 4, The terminal voltage of the main battery 1 or the auxiliary battery 4 is maintained within a certain range. Control of this kind of auxiliary battery power supply apparatus 2 is publicly known. In this embodiment, the control device 5 further reduces the voltage variation between the battery blocks 11 to 18 at an appropriate timing determined based on the voltages of the battery blocks 11 to 18 and input information from the outside. Perform equalization. For example, the equalization between blocks is performed by operating a part of the bidirectional DC-DC converters 21 to 28 in the forward step-down power transmission mode from the main battery 1 to the auxiliary battery 4, and the bidirectional DC-DC converters 21 to 28. The other part is executed by operating in the reverse step-up power transmission mode from the auxiliary battery 4 to the main battery 1. Needless to say, each of the bidirectional DC-DC converters 21 to 28 shares power transmission between the battery block to which the self-connected battery block 11 to 18 of the main battery 1 and the auxiliary battery 4 are connected.

(Bidirectional DC-DC converter 21)
The bidirectional DC-DC converters 21 to 28 employed in this embodiment will be described. Since the bidirectional DC-DC converters 21 to 28 have the same circuit configuration, the bidirectional DC-DC converter 21 responsible for power transfer between the battery block 11 and the auxiliary battery 4 will be described with reference to FIG. .

  The bidirectional DC-DC converter 21 includes a first AC / DC converter circuit 6A, transformers T1 and T2, and a second AC / DC converter circuit 6B. The first AC / DC converting circuit 6A includes transistors Q1 and Q2 that are connected in series with each other and operate in a complementary manner, and capacitors C1 and C2. The transformer T1 is formed by winding coils N1, N2, and N3 around the core, and the transformer T2 is formed by winding coils N4, N5, and N6 around the core. As shown in FIG. 2, the core of the transformer T1 and the core of the transformer T2 are magnetically separated. In other words, the coils N1, N2, and N3 and the coils N4, N5, and N6 are magnetically separated. The second AC / DC converter circuit 6B is composed of transistors Q3 and Q4 that operate in a complementary manner, and has the same circuit configuration as a so-called synchronous rectifier circuit. In this embodiment, the transistors Q1 to Q4 are constituted by MOS transistors.

(First AC / DC conversion circuit 6A)
The first AC / DC converting circuit 6A will be described below.

  The transistors Q1 and Q2 are connected in series with each other and connected to both ends of the battery block 11. The transistor Q1 is connected to the low potential end of the battery block 11, and the transistor Q2 is connected to the high potential end of the battery block 11. S is a connection point between the transistors Q1 and Q2. The high potential end of the battery block 11 reaches the connection point S through the capacitor C1 and the coils N1 and N4. The low potential end of the battery block 11 reaches the connection point S through the capacitor C2 and the coils N2 and N5.

(Second AC / DC conversion circuit 6A)
The second AC / DC converting circuit 6B will be described below.

  The connection point of the transistors Q3 and Q4 is connected to the low potential terminal (ground terminal) of the auxiliary battery 4. The drain terminal of the transistor Q4 is connected to the high potential end of the auxiliary battery 4 through the coil N3. The drain terminal of the transistor Q3 is connected to the high potential end of the auxiliary battery 4 through the coil N6.

(Operation)
Hereinafter, the operation of the DCDC converter 21 will be described.

(Power transmission operation from the first AC / DC converting circuit 6A to the second AC / DC converting circuit 6B)
In this embodiment, the transistors Q1 and Q4 operate synchronously, the transistors Q2 and Q3 operate synchronously, and the transistors Q1 and Q4 and the transistors Q2 and Q3 perform a complementary operation (reverse operation). Of course, a dead time may be provided as appropriate.

  In mode A in which the transistors Q1 and Q4 are on and the transistors Q2 and Q3 are off, a current flows through the capacitor C1 in the order of the coil N1 and the coil N4. Increase in the direction of. As a result, the output voltage of the coil N3 is applied to the auxiliary battery 4. The reverse voltage of the coil N6 is cut off by turning off the transistor Q3.

  Next, in the mode B in which the transistors Q1 and Q4 are off and the transistors Q2 and Q3 are on, current flows in the order of the transistor Q2, the coil N5, the coil N2, and the capacitor C2. Since the winding direction of the coils N1 and N4 and the winding direction of the coils N2 and N5 are reversed, the magnetic flux of the transformers T1 and T2 is the second opposite to the first direction as the current increases. (In the first direction, it decreases). As a result, the output voltage of the coil N6 is applied to the auxiliary battery 4. The reverse voltage of the coil N3 is cut off by turning off the transistor Q4.

  In this embodiment, since the capacitors C1 and C2 are provided, the current is sufficiently attenuated by the stored voltage of the capacitors C1 and C2 at the end of each mode.

  In mode A, when the transistor Q1 is turned on, the capacitor C2 and the coils N2 and N5 form a short circuit. For this reason, the electric charge stored in the capacitor C2 flows through the coils N2 and N5 in the opposite direction to the mode B. As a result, the discharge current of the capacitor C2 flowing through the coils N2 and N5 in mode A enhances the magnetic flux formed by the current flowing through the coils N1 and N4.

  In mode B, when the transistor Q2 is turned on, the capacitor C1 and the coils N1 and N4 form a short circuit. For this reason, the electric charge stored in the capacitor C1 flows through the coils N1 and N4 in the opposite direction to the mode A. As a result, the discharge current of the capacitor C1 flowing through the coils N1 and N4 in mode B enhances the magnetic flux formed by the current flowing through the coils N2 and N4.

  FIG. 3 shows the relationship between the duty D and the output voltage Vout when the duty of the transistor Q1 is D (the duty of the transistor Q2 is 1-D). From FIG. 3, it is understood that the output voltage Vout can be adjusted by adjusting the duty D. This two-transformer DC-DC converter can alternately output a voltage during the on period and the off period of the transistor Q1 by utilizing the reverse operation of the two transformers, and supplies a current to the secondary side of the two transformers. The transformer magnetic flux can be restored to its original state during a period of no output, and the output voltage can be freely changed by adjusting the duty D with high efficiency and low ripple.

(Power transmission from the second AC / DC converter circuit 6B to the first AC / DC converter circuit 6A)
When the voltage output from the first AC / DC conversion circuit 6A to the coils N3 and N6 is smaller than the terminal voltage of the auxiliary battery 4, the current flowing through the coils N3 and N6 is reversed, and in mode A, this is the coil N1, The battery block 11 is charged by increasing the voltage of N4 so that the current flowing through the capacitor C1 is reversed, and in mode B, the battery block 11 is charged with the current flowing through the coils N5 and N2 and the capacitor C2 being reversed.

  That is, if the output voltage of the bidirectional DC-DC converter 21 is decreased by adjusting the duty D, the reverse boost transmission from the auxiliary battery 4 to the battery block 11 is executed, and the amount can be easily adjusted by adjusting the duty D. Can be controlled.

(Modification)
The first AC / DC conversion circuit 6A of the bidirectional DC-DC converter 21 can be variously modified. For example, the capacitors C1 and C2 may be omitted. In this case, the magnetic energy stored in the coils N2 and N5 is extinguished by the short circuit by the transistor Q1 in the mode A period. However, at this time, since the direction of the magnetic flux formed in the cores of the transformers T1 and T2 by the current flowing through the coils N2 and N5 is opposite to the direction of the magnetic flux formed by the coils N1 and N4 in mode A, the efficiency is slightly reduced. . Similarly, the magnetic energy accumulated in the coils N1 and N4 is extinguished by the short circuit by the transistor Q2 in the mode B period. However, at this time, since the direction of the magnetic flux formed in the cores of the transformers T1 and T2 by the current flowing through the coils N1 and N4 is opposite to the direction of the magnetic flux formed by the coils N2 and N5 in mode B, the efficiency is slightly reduced. .

  In addition, a conventionally known H-bridge type inverter may be employed as the first AC / DC converting circuit 6A. In this case, since there is one transformer, a secondary coil with an intermediate tap should be adopted as the secondary coil of the transformer to which the second AC / DC conversion circuit 6B is connected. Since the H-bridge type inverter is well known, detailed description thereof will be omitted.

  FIG. 11 shows a voltage calculation formula for each part of the DCDC converter shown in FIG. 2, and FIG. 12 shows the waveform of each part.

(Example effect)
The auxiliary battery power supply device (vehicle DC-DC converter device) 2 of this embodiment described above has DCDC converters 21 to 28 provided individually for each of the battery blocks 11 to 18 of the main battery 1. Yes. Therefore, the control unit 5 individually controls the duty D of the transistor Q1 of the DCDC converters 21 to 28, so that in the step-down power transmission from the main battery 1 to the auxiliary battery 4, the battery blocks 11 to 18 are transferred to the auxiliary battery 4. It is possible to adjust the power transmission amount of the power as necessary.

  Each example of power transmission between the battery blocks 11 to 18 and the auxiliary battery 4 will be further described.

(Example 1 of power transmission between main battery 1 and auxiliary battery 4)
A control example of step-down power transmission from the main battery 1 to the auxiliary battery 4 will be described below with reference to the flowchart shown in FIG.

  First, the block voltages Vn1 to Vn8 of the battery blocks 11 to 18 and the output voltage V2 of the auxiliary battery power supply device 2 are read (S100), and the average duty D is calculated so that the difference between the output voltage V2 and the target voltage is zero. (S102). The average duty D mentioned here is the average value of the duty D of the transistor Q1 of each DCDC converter 21-28. Next, it is calculated whether or not the variation, which is the difference between the maximum value and the minimum value of the block voltages Vn1 to Vn8, exceeds a predetermined threshold value (S104), and if it does not exceed the predetermined threshold value Operates each DCDC converter 21-28 by the average duty D (S106). In the case of exceeding, the duty D of the battery block having a large voltage among the block voltages Vn1 to Vn8 is larger than the average duty D, and the duty D of the battery block having a small voltage is smaller than the average duty D. The DCDC converters 21 to 28 are individually controlled by the determined duty D, adjusted according to the magnitudes of the block voltages Vn1 to Vn8 (S108).

  As a result, the amount of power transmitted from the battery block having a relatively high SOC and a relatively high voltage to the auxiliary battery 4 is transmitted from the battery block having a relatively low SOC and a relatively low voltage to the auxiliary battery 4. Since it becomes larger than the amount, it is possible to realize equalization between the battery blocks 11 to 18 simultaneously with the power transmission from the main battery 1 to the auxiliary battery 4. This control is particularly suitable when the auxiliary battery 4 has a low voltage and is difficult to discharge.

(Example 2 of power transmission between main battery 1 and auxiliary battery 4)
A control example of power transfer between the main battery 1 and the auxiliary battery 4 will be described below with reference to a flowchart shown in FIG.

  The block voltages Vn1 to Vn8 of the battery blocks 11 to 18 and the output voltage V2 of the auxiliary battery power supply device 2 are read (S100), and it is checked whether or not the output voltage V2 exceeds a certain threshold voltage Vth1 (S112). If it exceeds, the following control is executed to avoid further increase in SOC of the auxiliary battery 4.

  First, it is calculated whether or not the variation, which is the difference between the maximum value and the minimum value of the block voltages Vn1 to Vn8, exceeds a predetermined threshold value (S114), and if it exceeds the predetermined threshold value, The DCDC converters 21 to 28 are controlled so that the amount of power transmitted from the main battery 1 to the auxiliary battery 4 and the amount of reverse power transmitted from the auxiliary battery 4 to the main battery 1 coincide with each other, or the latter is slightly increased. (S116).

  Thereby, the battery block having a small block voltage is charged by reverse power transmission from the auxiliary battery 4 through the DCDC converter, and the battery block having a large block voltage is discharged by transmitting power to the auxiliary battery 4 through the DCDC converter. Equalization between the blocks 11-18 can be realized. At this time, since the transmission power from the main battery 1 to the auxiliary battery 4 is set to be equal to or less than the reverse transmission power from the auxiliary battery 4 to the main battery 1, harmful charging of the auxiliary battery 4 does not occur. Alternatively, charging / discharging of the auxiliary battery 4 does not occur, and equalization can be realized with high efficiency.

(Example 3 of power transmission between main battery 1 and auxiliary battery 4)
A control example of power transfer between the main battery 1 and the auxiliary battery 4 will be described below with reference to a flowchart shown in FIG.

  The block voltages Vn1 to Vn8 of the battery blocks 11 to 18 and the output voltage V2 of the auxiliary battery power supply device 2 are read (S100). In S122, the output voltage V2 is higher than the threshold voltage Vth1 described above. It is checked whether or not the value voltage Vth2 is exceeded (or whether or not the SOC of the main battery 1 is small). If so, the following control is executed to avoid further charging of the auxiliary battery 4.

  First, it is calculated whether or not the variation, which is the difference between the maximum value and the minimum value of the block voltages Vn1 to Vn8, exceeds a predetermined threshold value (S124), and if it exceeds the predetermined threshold value, Then, reverse boost power transmission is performed from the auxiliary battery 4 to each of the battery blocks 11 to 18 of the main battery 1 (S126). However, in this aspect, reverse step-up power transmission through the DCDC converter from the auxiliary battery 4 to the battery block having a large block voltage is relatively small, and the DCDC converter from the auxiliary battery 4 to the battery block having a small block voltage is transmitted through the DCDC converter. Reverse boost transmission is relatively large.

  As a result, the battery block having a small block voltage is relatively strongly charged by reverse power transmission from the auxiliary battery 4 through the DCDC converter, and the battery block having a large block voltage is relatively charged by reverse power transmission from the auxiliary battery 4 through the DCDC converter. Therefore, the battery blocks 11 to 18 can be equalized and overcharge of the auxiliary battery 4 can be prevented.

(Example 4 of power transmission between main battery 1 and auxiliary battery 4)
A control example of power transfer between the main battery 1 and the auxiliary battery 4 will be described below with reference to a flowchart shown in FIG.

  First, the temperature T of the main battery 1 is detected, and if the temperature T is lower than the predetermined threshold temperature Tth, predetermined power is supplied from a part (preferably half) of the battery blocks 11 to 18 to the auxiliary battery 4 side. A battery heating cycle for transmitting power and transmitting substantially equal power from the auxiliary battery 4 to the other part (preferably the other half) of the battery blocks 11 to 18 is executed (S134). As a result, most of the loss is consumed by the battery internal resistance of each of the battery blocks 11 to 18 of the main battery 1 without wasting power, and the temperature of each of the battery blocks 11 to 18 can be increased rapidly and uniformly. .

  In addition, since the SOC dispersion | variation between each battery block 11-18 arises by the said power transmission, after that, the SOC dispersion | variation between each battery block 11-18 is suppressed by performing the battery heating cycle which transmits electric power in the reverse direction to the above. However, each battery block 11-18 can be heated rapidly.

(Example 5 of power transmission between main battery 1 and auxiliary battery 4)
A control example of power transfer between the main battery 1 and the auxiliary battery 4 will be described below with reference to a flowchart shown in FIG.

  First, a battery defect determination subroutine for determining whether each of the battery blocks 11 to 18 is good or bad is executed (S140). Any of various known methods may be employed for the battery defect determination operation. For example, a battery block having an excessive battery resistance may be determined to be defective or may be determined based on the block voltage of the battery block. Since the battery failure determination is not the gist of the present invention, the description thereof will be omitted.

  Next, it is determined whether there is a defective battery block based on the result of the battery defect determination operation (S142). If there is a defective battery block, the power transmission operation of the DCDC converter connected to the defective battery block is prohibited. Thereby, since charging / discharging of a defective battery block is not performed at the time of power transmission between the main battery 1 and the auxiliary battery 4, overheating and further deterioration of a defective battery block can be prevented.

(Example 6 of power transmission between main battery 1 and auxiliary battery 4)
A control example of power transfer between the main battery 1 and the auxiliary battery 4 will be described below with reference to a flowchart shown in FIG.

  First, the capacity of each battery block 11 to 18, that is, the full charge capacity is calculated (S150). The full charge capacity here refers to the capacity that the battery block can currently charge and discharge. Any of various known methods may be employed for calculating the full charge capacity. For example, the battery voltage and the charge / discharge current integrated value may be determined. Since the calculation of the full charge capacity itself is not the gist of the present invention, the description thereof will be omitted. In S150, a battery block whose full charge capacity is smaller than a full charge capacity of other battery blocks by a predetermined value or more (for example, 60% or less) is determined as a small capacity battery block.

  Next, in both charging and discharging of the main battery 1, control is performed to reduce the charge / discharge current of the small capacity battery block by the DCDC converter connected to the small capacity battery block.

  More specifically, when the main battery 1 is charged, the DCDC converter connected to the small capacity battery block performs a discharging operation from the small capacity battery block to the auxiliary battery 4. Thereby, it can suppress that a small capacity battery block reaches full charge, and can increase the electric energy which can be charged to another battery block by that much. Note that power transmission from the auxiliary battery 4 to another battery block may be executed in parallel with the discharging operation from the small capacity battery block to the auxiliary battery 4.

  Similarly, when the main battery 1 is discharged, the DCDC converter connected to the small capacity battery block performs a charging operation from the auxiliary battery 4 to the small capacity battery block. As a result, the SOC of the small-capacity battery block can be prevented from decreasing earlier than the other battery blocks, and the amount of power that can be discharged by the other battery blocks can be increased accordingly. Note that power transmission (discharge) from another battery block to the auxiliary battery 4 may be executed in parallel with the power transmission (charging) operation from the auxiliary battery 4 to the small capacity battery block.

  If it does in this way, charging / discharging of big battery energy is realizable using the main battery 1 which has the battery block which deteriorated considerably.

(Example 7 of power transmission between main battery 1 and auxiliary battery 4)
A control example of power transfer between the main battery 1 and the auxiliary battery 4 will be described below with reference to a flowchart shown in FIG.

  First, a battery failure determination subroutine for determining whether each of the battery blocks 11 to 18 is good or bad is executed (S160). Any of various known methods may be employed for the battery defect determination operation. For example, a battery block having an excessive battery resistance may be determined to be defective or may be determined based on the block voltage of the battery block. Since the battery failure determination is not the gist of the present invention, the description thereof will be omitted.

  Next, it is determined whether or not there is a defective battery block based on the result of the battery defect determination operation (S162). If there is a defective battery block, the magnitude of the charge / discharge current of the defective battery block becomes a predetermined value or less. Thus, the power transmission or reverse power transmission operation of the DCDC converter connected to the defective battery block is controlled (S164). Thereby, the charging operation and the discharging operation of the main battery 1 can be maintained while suppressing the overheating of the defective battery block.

It is a circuit diagram which shows the auxiliary machine battery electric power feeder of an Example. It is a circuit diagram of the DCDC converter shown in FIG. It is a characteristic view which shows the relationship between the duty of the DCDC converter of FIG. 2, and an output voltage. 2 is a flowchart illustrating an example of control of the auxiliary battery power supply apparatus of FIG. 1. 2 is a flowchart illustrating an example of control of the auxiliary battery power supply apparatus of FIG. 1. 2 is a flowchart illustrating an example of control of the auxiliary battery power supply apparatus of FIG. 1. 2 is a flowchart illustrating an example of control of the auxiliary battery power supply apparatus of FIG. 1. 2 is a flowchart illustrating an example of control of the auxiliary battery power supply apparatus of FIG. 1. 2 is a flowchart illustrating an example of control of the auxiliary battery power supply apparatus of FIG. 1. 2 is a flowchart illustrating an example of control of the auxiliary battery power supply apparatus of FIG. 1. It is explanatory drawing which shows each part voltage calculation formula of the DCDC converter shown in FIG. It is a timing chart which shows each part waveform of the DCDC converter shown in FIG.

Explanation of symbols

C1, C2 capacitors
D duty
N1-N6 coil
Q1-Q4 transistors (switching transistors)
T1, T2 transformer
Vn1 to Vn8 Block voltage 1 Main battery 2 Auxiliary battery power supply 3 Smoothing capacitor 4 Auxiliary battery 5 Control device (control unit)
6A AC-DC conversion circuit 6B AC-DC conversion circuit 11-18 Battery block 21-28 DCDC converter

Claims (3)

In a vehicular DCDC converter device for transmitting power from a high voltage main battery formed by connecting a plurality of battery blocks in series to a low voltage auxiliary battery in an electrically insulating manner,
A plurality of DC / DC converters that separately perform power transmission between each of the plurality of battery blocks and the auxiliary battery, and a power transmission amount of the plurality of DC / DC converters can be individually controlled. A battery state detection unit for determining whether a part of each of the battery blocks is defective, and a plurality of battery blocks connected in series, the battery block determined to be defective and the auxiliary battery, And a controller for stopping the operation of the DC / DC converter in between. In a vehicular DCDC converter device for transmitting power from a high voltage main battery formed by connecting a plurality of battery blocks in series to a low voltage auxiliary battery in an electrically insulating manner,
A transformer T1 having coils N1, N2, and N3 and a transformer T2 having coils N4, N5, and N6 are provided. The coils N1 and N4 are connected in series to form a first coil pair, and the coils N2 and N5 are connected in series. And the other end of the coil N1 forms an independent terminal (Te1) of the first coil pair, the other end of the coil N2 forms an independent terminal (Te2) of the second coil pair, and the coil N4, The other end of N5 is a transformer pair forming a common terminal (Tec) of the first and second coil pairs, and a transistor (Q1) having one end connected to the common terminal (Tec) and the other end connected to the independent terminal (Te2). When, at both ends of the battery blocks together and formed a transistor (Q2) having one end and the other end to said common terminal (Tec) is connected to the independent terminals (Te1) connected in series A first AC / DC converter circuit that performs AC / DC power conversion by complementary switching of the two transistors (Q1 and Q2), a transistor (Q4) connected in series with the coil N3, and a transistor ( Q3), one end of both transistors (Q3, Q4) is connected in common to form a first output end, and the other end of both transistors (Q3, Q4) passes through coils N3, N6 individually to the second. And a second AC / DC converter circuit that performs AC / DC power conversion by complementary switching of the transistors (Q3 and Q4), and power between each of the plurality of battery blocks and the auxiliary battery A plurality of DC / DC converters that perform transmission separately;
A vehicular DCDC converter apparatus comprising: a control unit capable of individually controlling power transmission amounts of the plurality of DC / DC converters. The DC / DC converter device for a vehicle according to claim 2 ,
The independent terminal (Te1) is connected to the other end of the transistor (Q2) through a capacitor (C1).
The vehicle DC-DC converter device, wherein the independent terminal (Te2) is connected to the other end of the transistor (Q1) through a capacitor (C2).