Communication system

Abstract

In a communication system, a control unit (6) and driver units (11) are connected in daisy chain; each unit includes a respective isolation communication circuit (13 and 14). The control unit measures, during a measurement period, the communication delay time between the control unit and each driver unit starting from the response time of executing a transmission pulse signal to each driver unit. Then, based on each communication delay time, the control unit sends a migration time to each driver unit to equalize the timings of the signals output by the driver units. When each driver unit receives an instruction from the control unit indicating the output of a signal by each driver unit, each driver unit outputs a signal when the migration time has elapsed.

Description

Technical Field

[0001] The present disclosure relates to a system in which communication devices including a master device and a plurality of slave devices communicate with each other in a daisy chain form. Background Art

[0002] For example, Patent Document 1 proposes a so-called in-wheel motor, in which a motor serving as a vehicle drive source in an electric vehicle is arranged on the inner peripheral side of a wheel included in a traveling wheel. In addition, Patent Document 2 discloses a motor provided with an inverter as a drive circuit corresponding to each motor in order to independently control the motors arranged on each wheel. In addition, Patent Document 3 discloses an inverter having an in-wheel structure and a motor corresponding to the inverter.

[0003] Patent Document 1: JP 2006-166544 A

[0004] Patent Document 2: JP 2009-207235 A

[0005] Patent Document 3: US 9073424 B2 Summary of the Invention

[0006] Here, assuming an in-wheel structure as in Patent Document 3, in which a motor and an inverter are provided on the inner peripheral side of a wheel. In such an in-wheel structure, an ECU (electronic control unit) for controlling the inverter needs to send drive signals to each of a plurality of switching elements constituting the inverter arranged on each wheel. In this case, since the wiring distance from the ECU to each wheel becomes longer, the difference in the delay time generated between the respective drive signals also becomes larger.

[0007] Generally, in order to prevent a short circuit between the upper arm and the lower arm, a dead time for simultaneously turning off the switching elements of the upper arm and the lower arm is provided for the drive signals supplied to each switching element. In the in-wheel structure inverter, if the variation in the delay time generated between the drive signals increases, it is necessary to set a longer dead time accordingly.

[0008] However, if a long dead time is set, the loss generated by the motor will increase, torque fluctuations and cogging will occur in the low speed range, and the gain will decrease at the current zero crossing point in vector control, resulting in deterioration of the controllability of the motor.

[0009] An object of the present disclosure is to provide a communication system capable of minimizing the time difference of signals sent from a master device to a plurality of slave devices connected in a daisy chain form.

[0010] According to a first aspect of the present disclosure, there is provided a communication system provided with communication devices connected in a daisy chain form. The communication devices include a master device and a plurality of slave devices, and the plurality of slave devices are arranged in the daisy chain from the master device in the communication connection order from the first position to the last. The master device and the plurality of slave devices respectively include corresponding insulated communication circuits. The master device is configured to measure, during a measurement period, a first communication delay time between the master device and a first slave device, which is any one of the plurality of slave devices, starting from a first response time in response to a transmission to the first slave device. Then, the master device is configured to (i) calculate a first shift time of the first slave device based on the measured first communication delay time, the first shift time being calculated to allow a first moment when the first slave device outputs a first signal to be equal to a second moment when a second slave device, which is any one of the plurality of slave devices other than the first slave device, outputs a second signal, and (ii) send the first shift time to the first slave device. Then, after receiving the first shift time, in response to an instruction to output the first signal received from the master device, the first slave device is configured to execute the output of the first signal at a time when a time elapsed from the time when the instruction to output the first signal is received from the master device passes the first shift time.

[0011] The above configuration can provide the following effects. When the wiring distances between the master device and each slave device are very long, it is assumed that the moments when each slave device receives an instruction to output a signal sent by the master device are different from each other. In such an assumption, each slave device is configured to output the signal required by the instruction after the shift time sent from the master device has passed. Therefore, the slave devices can synchronize the output moments of the signals.

[0012] According to a second aspect, which is an optional aspect of the first aspect, in the communication system, when the master device is activated, the master device respectively sends a plurality of identity data for identifying the slave devices, thereby assigning corresponding identity data to the slave devices. With this configuration, even if the number of slave devices connected in a daisy chain varies depending on the system, each slave device can be easily identified.

[0013] According to a third aspect, which is an optional aspect of the first aspect, in the communication system, the plurality of slave devices are configured to respectively output corresponding drive signals to corresponding switching elements included in a power conversion circuit configured to convert direct current into alternating current. Therefore, for a power conversion circuit such as an inverter, a dead time set to prevent a short circuit between the upper arm and the lower arm can be set as short as possible. This makes it possible to prevent a reduction in drive efficiency and deterioration of controllability. Description of the Drawings

[0014] The objectives, features, and advantages of the present disclosure will become more apparent from the following detailed description with reference to the accompanying drawings. In the drawings:

[0015] Figure 1 is a diagram showing a configuration in which a control unit and each driver unit according to a first embodiment are connected in a daisy chain;

[0016] Figure 2 shows a more detailed connection configuration between two isolated communication circuits;

[0017] Figure 3 is a more detailed display of Figure 4 the functional block diagram of the system configuration shown;

[0018] Figure 4 is a functional block diagram schematically showing the system configuration of an electric vehicle;

[0019] Figure 5 is a flowchart showing the system operation when power is turned on;

[0020] Figure 6 is a flowchart showing normal system operation;

[0021] Figure 7 is a diagram showing the process of assigning IDs to each IC;

[0022] Figure 8 is a diagram showing the correction of the clock frequency performed by each IC;

[0023] Figure 9 is a diagram showing the measurement process of the communication delay time between ICs;

[0024] Figure 10 is a diagram showing an example of the communication delay time of each IC;

[0025] Figure 11 is a diagram showing the process of synchronizing the output timing of the gate drive signal by migrating instructions to each IC;

[0026] Figure 12 is a diagram showing a specific example of the drive instruction sent from the control unit to each driver unit according to a second embodiment;

[0027] Figure 13 is a diagram showing an example of the drive instruction data to be sent;

[0028] Figure 14It is a diagram showing a specific example of drive instructions sent from the control unit to each drive unit according to the third embodiment;

[0029] Figure 15 It is a diagram showing an example of the data of drive instructions to be sent;

[0030] Figure 16 It is a flowchart showing the correction process of the total delay time according to the fourth embodiment;

[0031] Figure 17 It is a flowchart showing the measurement process of the total delay time;

[0032] Figure 18 It is a diagram showing an example of the correction result of the total delay time;

[0033] Figure 19 It is a diagram showing the space voltage vector according to the fifth embodiment;

[0034] Figure 20 It is a diagram showing an example of three-phase signals in one carrier period of a sector;

[0035] Figure 21 It is a diagram showing the example of drive instructions corresponding to Figure 20 ;

[0036] Figure 22 It is a diagram showing the process of adding the information sensed by each drive unit to the free area of the data packet of drive instructions according to the sixth embodiment;

[0037] Figure 23 It is a diagram showing the state of communication interruption according to the seventh embodiment;

[0038] Figure 24 It is a flowchart showing the process executed by the control unit;

[0039] Figure 25 It is a diagram showing a variation of the arrangement of the insulation communication circuit in the control unit according to the eighth embodiment;

[0040] Figure 26 It is a diagram showing a variation of the arrangement of the insulation communication circuit in the drive unit according to the ninth embodiment;

[0041] Figure 27 It is a diagram showing the configuration in which the control unit and the drive units are in a daisy chain for each phase according to the tenth embodiment;

[0042] Figure 28 It is a diagram showing the process of synchronizing the output timing of the gate drive signal by migrating instructions to each IC;

[0043] Figure 29 is a diagram showing a three-level inverter according to the eleventh embodiment;

[0044] Figure 30 is a diagram showing that the control unit and driver unit of the three-level inverter are configured in a daisy chain for each phase; and

[0045] Figure 31 is a diagram showing a case of a battery monitoring device applicable to an assembled battery according to the twelfth embodiment. DETAILED DESCRIPTION

[0046] (First Embodiment)

[0047] As Figure 4 shown, the communication system according to the first embodiment is applied to an electric vehicle in which (i) a motor and (ii) an inverter for driving the motor have an in-wheel structure (i.e., the motor and the inverter are arranged in the wheels). In Figure 4 the figure, for ease of illustration, the motor and the inverter are shown outside the wheels 2L and 2R, but in reality, the motor and the inverter have an in-wheel structure as Figure 3 shown.

[0048] The motor 3L and the inverter 4L are arranged corresponding to the wheel 2L of the electric vehicle 1. The inverter 4L drives the motor 3L. The rotating shaft of the motor 3L is attached to the axle of the wheel 2L. Similarly, the motor 3R and the inverter 4R are arranged corresponding to the wheel 2R. Driving power is supplied from a secondary battery 5 such as a lithium-ion battery to the inverters 4L and 4R. A control unit 6 as an ECU (Electronic Control Unit) outputs drive control signals to the inverters 4L and 4R via cables 7L and 7R. If it is not necessary to distinguish between left and right in the description of the configurations described below, the reference numerals do not show "L" or "R".

[0049] The inverter 4 as an example of a power converter includes a main circuit 8 and a gate driver circuit 9. The main circuit 8 is configured by connecting, for example, N-channel MOSFETs 10 as switching elements to a three-phase bridge. The gate driver circuit 9 includes six driver units 11 corresponding to the six FETs 10 respectively, and each driver unit 11 outputs a gate drive signal to the corresponding FET 10. Each driver unit 11 includes an IC 12 having a communication function.

[0050] As Figure 1As shown, the control unit 6 includes an isolation communication circuit 13, and the IC 12 of each driver unit 11 also includes an isolation communication circuit 14. The isolation communication circuit 13 and the isolation communication circuits 14(1) to 14(6) are daisy-chained via a communication cable. Figure 2 Shows a more detailed connection configuration between the isolation communication circuit 13 and the isolation communication circuit 14(1) which are two isolation communication circuits.

[0051] Each of the isolation communication circuits 13 and 14 includes a power supply 21, a gate array 22, a transmit / receive circuit 23, a protection circuit 24, a filter 25, and an isolation element 26. Then, the isolation elements 26 and 26 included in the isolation communication circuits 13 and 14(1) are connected via a cable 7. The control unit 6 is an example of a master device, and each driver unit 11 is an example of a slave device. In addition, the control unit 6 and each driver unit 11 are also examples of communication devices.

[0052] The operation according to the present embodiment will be described below. As Figure 5 shown, when the ignition switch (IG) of the vehicle is turned on and the power supply is turned on, the control unit 6 assigns an identity ID to the isolation communication circuit 14 of each driver unit 11 (S1). For this purpose, for example, known techniques disclosed in JP2006-268254A, JP2011-181392A, WO2014 / 162765A1 are used. The disclosures of JP2006-268254A, JP2011-181392A, and WO2014 / 162765A1 are incorporated herein by reference.

[0053] For example, as Figure 7 shown, according to the communication connection order of the daisy chain, the ID of the isolation communication circuit 13 is set to IC0, and the IDs of the isolation communication circuits 14(1) to 14(6) are set to IC1 to IC6, respectively. The ID data corresponds to the identity data. Hereinafter, the control unit 6 and each driver unit 11 can be represented by IC0 to IC6, which are the IDs of the isolation communication circuits 13, 14(1) to 14(6), respectively.

[0054] Subsequently, the control unit 6 repeatedly transmits a pulse signal as a synchronization signal to each driver unit 11 at regular time intervals via IC0 (S2). As Figure 8 shown, each of IC1 to IC6 uses a counter to count the interval between the rising edges of the received synchronization signal using the clock signal output from an oscillator which is an oscillation circuit, as a clock count value (S3). The functions of the oscillator and the counter are provided by the gate array 22.

[0055] IC1 to IC6 each determine whether the clock count value is a predetermined target value (S4). If the clock count value does not match the target value (No), the clock period of each oscillator is changed, and then the process returns to step S3 (S5). If the clock count value matches the target value (Yes), the clock period of each oscillator is locked (S6).

[0056] Next, when the pointer N indicating the ID number of the IC is set to "1" (S7), the control unit 6 sends a single-pulse signal from IC0 to IC_N (S8). Once the single-pulse signal is received, IC_N returns the single-pulse signal to the control unit 6 (S9). That is, in this case, the single-pulse signal is not sent to the downstream side of the daisy chain but to the upstream side. In other words, any one of the multiple driver units 11 as multiple slave devices is configured to return a response to the control unit 6 as the master device in a direction reverse to the direction of receiving the transmission from the master device during steps S8 to S12 as a measurement period (described later).

[0057] When the control unit 6 receives the single-pulse signal returned by IC_N, the control unit 6 measures the round-trip time from the transmission time of the single-pulse signal to the reception time of the single-pulse signal, halves the measured round-trip time to obtain the signal delay time, and stores the obtained signal delay time (see S10, Figure 9 ). Then, it is determined whether the pointer N is "6" (S11). When it is not "6" (No), the pointer N is incremented (S12) and the process returns to step S8. The above steps S8 to S12 correspond to the measurement period.

[0058] When measuring the above delay time, a replica circuit of the circuit capable of outputting a gate drive signal is prepared for each of IC1 to IC6. Therefore, the delay time of the signal generated in the replica circuit can be added as an internal delay.

[0059] When the pointer N becomes "6" (Yes), the control unit 6 extracts the longest time from the stored delay times of IC1 to IC6 (S13). Then, when the time differences between the respective delay times of IC1 to IC6 and the longest delay time are obtained, the obtained time differences are sent to the corresponding driver units 11 (S14). Each driver unit 11 stores the time difference corresponding to itself (S15). In Figure 10 the example shown, the longest delay time is 25 μs for IC6, and the respective corresponding time differences of IC1 to IC6 with respect to the longest delay time are shown as [15 μs, 12 μs, 9 μs, 6 μs, 3 μs, 0 μs].[[]END]]

[0060] Then, asFigure 6 As shown, in the normal operation of driving and controlling the motor, when the control unit 6 sends a driving instruction to each driver unit 11 (S21), each driver unit 11 shifts the output timing of the gate drive signal by a corresponding time difference (i.e., the shift time) (S22). As a result, each driver unit 11 drives all phases at the same moment, resulting in the simultaneous driving of all phases (S23). Figure 11 An image of the simultaneous driving of all phases is shown.

[0061] In this way, the output timings of the gate drive signals supplied to the respective FETs 10 constituting the main circuit 8 of the inverter 4 become simultaneous. This eliminates the need to provide a dead time to prevent a short circuit between the upper arm and the lower arm.

[0062] As described above, according to the first embodiment, the control unit 6 and each driver unit 11 connected in daisy chain are respectively provided with insulation communication circuits 13 and 14. The control unit 6 measures the communication delay time between the control unit 6 and each driver unit 11 from the response time in response to the pulse signal transmission to each driver unit 11 during the measurement period. Then, based on the corresponding communication delay time of the driver unit 11, the control unit 6 sends the corresponding shift time to the driver unit 11 so that the timings of the signals output by the driver unit 11 are equal. Then, when each driver unit 11 receives an instruction to output a signal from the control unit 6, the driver unit 11 outputs a signal after the shift time has elapsed.

[0063] The above configuration can provide the following effects. When the wiring distance between the control unit 6 and each of the multiple driver units 11 is significantly long, it is assumed that the timings at which the multiple driver units 11 receive the signals sent by the control unit 6 are different. In such an assumption, each driver unit 11 is configured to output a signal after the shift time sent from the control unit 6 has elapsed. Thereby, each driver unit 11 can synchronize the output timing of the signal with the output timings of the other driver units 11.

[0064] In this case, when the control unit 6 is started, the control unit 6 sends a plurality of identity data for respectively identifying the driver units 11, thereby assigning corresponding identity data to the driver units 11. With this configuration, even if the number of slave devices connected in daisy chain varies depending on the system, each slave device can be easily identified.

[0065] Then, each driver unit 11 outputs a drive signal to each of the multiple FETs 10 constituting the main circuit 8 of the inverter 4. Therefore, there is no need to set a dead time to prevent a short circuit between the upper arm and the lower arm. This makes it possible to prevent a reduction in drive efficiency and deterioration of controllability.

[0066] In addition, each driver unit 11 is provided with an oscillation circuit whose clock frequency is adjustable and a counter that counts the clock signal output from the oscillation circuit serving as an oscillator. The control unit 6 sends a synchronization signal to each driver unit 11. Each driver unit 11 uses the counter to count the interval time of the output synchronization signal as a count value, and adjusts the clock frequency so that the count value becomes a predetermined value. As a result, each driver unit 11 can accurately measure each migration time when outputting the gate drive signal. Therefore, the output timing of the gate drive signal can be reliably synchronized.

[0067] (Second Embodiment)

[0068] Hereinafter, for the sake of simplicity of description, the same parts as those in the first embodiment are denoted by the same reference numerals. Only the differences from the first embodiment will be described below. The second embodiment shows a specific example of the drive instruction sent from the control unit 6 to each driver unit 11. As Figure 12 and Figure 13 shown, when the carrier frequency of PWM control is, for example, 5 kHz and the period is 200 μs, drive instruction data is sent every 200 μs. In this case, if no drive instruction is sent in the next control period, the driver unit 11 can determine that an abnormality of communication interruption has occurred and perform a protection operation such as shutdown.

[0069] (Third Embodiment)

[0070] Similar to the second embodiment, the third embodiment will be described using a specific example of the transmission mode of the drive instruction. In the third embodiment, as Figure 14 and Figure 15 shown, data is sent at the stage where the mode of the three-phase drive instruction changes. In this case, compared with the second embodiment, the communication rate can be reduced.

[0071] (Fourth Embodiment)

[0072] In the first embodiment, Figure 10 the communication delay time shown may vary according to environmental conditions such as temperature. Therefore, in the fourth embodiment, the measurement of the delay time is performed periodically. When the change ratio of the delay time based on the initial measurement exceeds a threshold value, the process of updating the time difference sent to each driver unit is performed.

[0073] As Figure 16 shown, in the loop of steps S31 to S33, the total delay time measurement process in step S31 is performed periodically. In Figure 17In the total delay time measurement process shown, the control unit 6 sends a pulse signal from IC0 to IC1 and starts time measurement, i.e., clock counting (S41, S42). The IC_N that has received the pulse signal passes the pulse signal to the downstream IC_N+1 (S43). It should be noted that the control unit 6 does not participate in steps S43 to S46, and the processing performed on the IC1 to IC6 sides is shown. When "Yes" is obtained in step S44, IC6 sends the pulse signal received from IC5 to the control unit 6 (IC0) (S46). When the control unit 6 receives the pulse signal sent by IC6, the control unit 6 ends the time measurement (S47).

[0074] In Figure 16 , when returning from the total delay time measurement process, it is determined whether the measurement process is executed for the first time (S32). When it is determined that the measurement process is executed for the first time (S32: Yes), the control unit 6 stores the measurement result as the initial value of the total delay time (i.e., the initial measurement time) (S33). When executed for the second or subsequent times (S32: No), the difference between the current measurement time and the initial measurement time is obtained, and it is determined whether the difference exceeds the threshold value (S34). Regarding the threshold value here, for example, if the initial measurement time is 50 μs, 3 μs can be set as a value less than 10% of the initial measurement time. If the difference between the two measurement times is equal to or less than the threshold value (No), the process returns to step S31.

[0075] When the difference between the two measurement times exceeds the threshold value (Yes), the control unit 6 obtains and stores the change ratio of the current measurement time relative to the initial measurement time (S35). Then, each delay time is updated by multiplying the delay time of each of IC1 to IC6 stored in step S10 by the above change ratio (S36).

[0076] Subsequently, similar to step S14, the control unit 6 obtains the difference between the longest delay time and the other delay times based on the updated values and sends the difference to each driver unit 11 (S37). Each driver unit 11 stores the time difference corresponding to itself (S38). Then, the process returns to step S31.

[0077] For example, as Figure 18 shown, when the total delay time increases by 10% relative to the value at the start (i.e., the initial time), the migration time corresponding to each driver unit 11 is updated according to the change ratio.

[0078] As described above, according to the fourth embodiment, the control unit 6 measures and monitors the total delay time from the time when the pulse signal is sent to the time when the pulse signal is received via the driver unit 11(6) located at the communication connection end of the daisy chain. When the total delay time measured this time changes with respect to the previously measured value, the migration time of each driver unit 11 is corrected according to the change ratio. In other words, the master device is configured to measure and monitor the total delay time from the time when a signal is sent to the first slave device arranged in the communication connection order in the daisy chain among the plurality of slave devices to the time when a response is received by the last slave device arranged in the communication connection order in the daisy chain among the plurality of slave devices. Then, in response to the total delay time having changed with respect to the previously measured value, the master device is configured to correct the migration time of each of the plurality of slave devices according to the change ratio. As a result, even if the signal delay time changes due to changes in environmental conditions or the like, the migration time of each driver unit 11 can be appropriately corrected.

[0079] (Fifth Embodiment)

[0080] In the fifth embodiment, the drive instruction sent from the control unit 6 to each driver unit 11 is generated according to the Figure 19 and Figure 20 shown space vector method. Figure 20 is a three-phase drive signal pattern having one carrier period T in sector 1. In a half cycle, the voltage vector changes as [V0→V2→V1→V0], and the output time of each voltage vector changes as [t3 / 4→t2 / 2→t1 / 2→t3 / 4].

[0081] Figure 21 is an example of the drive instruction data sent from the control unit 6 to each driver unit 11 corresponding to Figure 20 . The first 3 bits represent the voltage vector, and the last 7 bits represent the output time of each voltage vector. Since the second half of the period T is the reverse of the output pattern of the first half, it is only necessary to send the data of the first half. The control unit 6 centrally sends the data in such a format at the start of each carrier period T. Each driver unit 11 grasps the binary level of the gate drive signal output by each according to the voltage vector represented by the first 3 bits.

[0082] As described above, the fifth embodiment provides the following effects. The control unit 6 generates drive instructions to be sent to each driver unit 11 by the space vector method. At the start of the carrier period T which is the control period, the control unit 6 sends drive instructions, the drive instructions having data including the level value of the drive signal and the duration of the level value in the period T. Each driver unit 11 outputs a gate drive signal to each FET 10 based on the received data. As a result, the communication rate can be further reduced. In addition, when data cannot be received at the start of the period T, each driver unit 11 can detect a communication interruption.

[0083] (Sixth Embodiment)

[0084] In the sixth embodiment, the space vector method is applied as in the fifth embodiment. Each driver unit 11 adds information to the idle area of the data packet sent by the control unit 6 and forwards it to the control unit 6. The added information includes information sensed by sensors or the like provided in each driver unit 11, such as information about the temperature, voltage, current, and short circuit of the FET 10.

[0085] As Figure 22 shown, there is an idle area in the drive instruction data packet sent by IC0. IC1 adds information on the U-phase lower arm to the received data packet and sends it to IC2. IC2 adds information on the U-phase upper arm to the received data packet and sends it to IC3. Similarly, IC3 to IC6 respectively add information on the V-phase lower arm, V-phase upper arm, W-phase lower arm, and W-phase upper arm to the data packet. IC0 receives the data packet sent by IC6 and grasps the information of each driver unit 11.

[0086] As described above, the sixth embodiment provides the following effects. When each driver unit 11 receives a drive instruction data packet, it adds the state data obtained by sensing to the data packet, and then sends the data packet to the IC (i.e., the communication device) located at the next position or the next arrangement on the downstream side in the daisy chain in the connection communication order. As a result, the control unit 6 can grasp the information about each driver unit 11.

[0087] (Seventh Embodiment)

[0088] In the seventh embodiment, for example, as Figure 23As shown, when the control unit 6 detects a communication interruption between the driver units 11(3) and 11(4), the control unit 6 stops the communication via the daisy chain. In the daisy chain communication, port A of the insulation communication circuit 13 is used as the transmission end, and port B is used as the reception end. Assume the situation where the control unit 6 stops the daisy chain communication as described above. In this case, the control unit 6 switches to perform two-way communication with IC1 to IC3 using port A and perform two-way communication with IC6 to IC4 using port B.

[0089] As Figure 24 shown, assume that the control unit 6 detects a communication interruption (S51) between IC_X and IC_Y (X < Y). For example, in the Figure 23 example shown, the control unit 6 can grasp the occurrence of a communication interruption between IC3 and IC4 by being notified of a communication interruption from IC4 to IC6. In this case, X = 3 and Y = 4.

[0090] Next, the control unit 6 configures a communication chain to perform one-way communication on the IC0 → IC1 →... → IC_X side (S52), and configures a communication chain to perform one-way communication on the IC0 → IC6 →... → IC_Y side (S53). Then, the control unit 6 generates a drive instruction for IC_N (S54). When N is X or less (S55: Yes), the control unit 6 sends the drive instruction through the path on the IC0 → IC1 →... → IC_X side (S56). Then, IC0 to IC_X reverse and send the information of each driver unit 11 through the path of IC_X →... → IC1 → IC0 (S57). On the other hand, if N is greater than X (S55: No), the control unit 6 sends the drive instruction through the path on the IC0 → IC6 →... → IC_Y side (S58). Then, IC_Y to IC6 reverse and send the information of each driver unit 11 through the route of IC_Y →... → IC6 → IC0 (S59).

[0091] As described above, the seventh embodiment provides the following. When the control unit 6 detects a communication interruption in any connection path between the driver units 11, it also constitutes a path for starting communication from the side of the driver unit 11(6) located at the end of the daisy chain. In other words, in response to detecting that a communication interruption has occurred between any two of the plurality of slave devices arranged adjacent to each other in the communication connection order in the daisy chain, the master device is configured to create a communication path, wherein the last slave device arranged in the communication connection order from the master device in the daisy chain among the plurality of slave devices is set to be in the first position arranged from the master device in the communication connection order in the created communication path. As a result, the motor 3 can be driven even in the event of an abnormality, and the vehicle can perform an evacuation action.

[0092] (Eighth Embodiment)

[0093] The eighth embodiment is a variation related to the arrangement of the insulation communication circuit 13 in the control unit 6. As Figure 25 shown, the insulation communication circuit 13 can be integrated inside the microcomputer 31 constituting the control unit 6, or the insulation communication circuit 13 can be arranged outside the microcomputer 31.

[0094] (Ninth Embodiment)

[0095] The ninth embodiment is a variation related to the arrangement of the insulation communication circuit 14 in the driver unit 11. As Figure 26 shown, the insulation communication circuit 14 can be arranged outside the IC 12. The insulation communication circuit 14 can be built in a power card configured to be able to dissipate heat from both sides of the resin mold.

[0096] (Tenth Embodiment)

[0097] In Figure 27 the tenth embodiment shown, the control unit 6 includes three insulation communication circuits 13U, 13V, and 13W corresponding to the U-phase, V-phase, and W-phase. The insulation communication circuit 13U is connected to the driver units 11(1) and 11(2) in a daisy chain. The insulation communication circuit 13V is connected to the driver units 11(3) and 11(4) in a daisy chain. The insulation communication circuit 13W is connected to the driver units 11(5) and 11(6) in a daisy chain.

[0098] In this case, as Figure 28 shown, the control unit 6 outputs drive commands to the IC1, IC3, and IC5 respectively. The migration of the execution of the drive command is such that the output timing of the gate drive signals between the upper arm and the lower arm in each of the U-phase, V-phase, and W-phase is equal. With this configuration, the delay time of the communication signal can be shortened.

[0099] (Eleventh Embodiment)

[0100] The eleventh embodiment shows a case where it is applied to a multilevel inverter. Figure 29 It is the main circuit 33 of a three-level inverter, in which each arm is formed by connecting four IGBTs 32 in series. In this case, as Figure 30 shown, the driver units 11(1) to 11(4) correspond to the U-phase arm; the driver units 11(5) to 11(8) correspond to the V-phase arm; and the driver units 11(9) to 11(12) correspond to the W-phase arm. Then, the control unit 6 and the driver units 11(1) to 11(12) are connected in a daisy chain.

[0101] (Twelfth Embodiment)

[0102] Figure 31 The twelfth embodiment shown shows a case where the present disclosure is applied to a battery monitoring device 42 connected to an assembled battery 41, in which x unit cells 40 are connected in series. The battery monitoring device 42 includes (i) a battery ECU 43 serving as an IC0 and (ii) battery ICs 44(1) to 44(x) serving as IC1 to IC_x. The battery ICs 44(1) to 44(x) are respectively connected to the corresponding unit cells 40(1) to 40(x). The battery ECU 43 and the battery ICs 44(1) to 44(x) are connected in a daisy chain.

[0103] In the battery monitoring device 42 configured as described above, the battery ECU 43 measures each delay time in the same manner as in the first embodiment, and sends the migration time to each of the battery ICs 44(1) to 44(x). Then, for example, each of the battery ICs 44(1) to 44(x) synchronizes the timing of measuring the voltage of each unit cell 40(1) to 40(x) according to the corresponding migration time. As described above, when applied to the battery monitoring device 42, simultaneity of the data obtained by measurement can be ensured for each of the unit cells 40(1) to 40(x).

[0104] (Other Embodiments)

[0105] The present disclosure can be applied to, but is not limited to, the gate driver circuit of an inverter and a battery monitoring device. It can be applied to synchronize the processing times of each slave device in a system in which a master device and a plurality of slave devices are connected in a daisy chain for communication. Although the present disclosure has been described according to embodiments, it should be understood that the present disclosure is not limited to such embodiments or configurations. The present disclosure incorporates various modifications and variations within the equivalent scope. In addition, various combinations and configurations, as well as other combinations and configurations including only one element, more, or less, are within the scope and spirit of the present disclosure.

Claims

1. A communication system, comprising communication devices that communicate with each other in a daisy chain form, wherein the communication devices comprise: a master device; and a plurality of slave devices, which are arranged in the daisy chain from the master device in the communication connection order from the first position to the last, wherein: the master device and the plurality of slave devices respectively include corresponding insulated communication circuits; the master device is configured to (i) with respect to a first slave device that is any one of the plurality of slave devices, during a measurement period, measure a first communication delay time between the master device and the first slave device starting from a first response time in response to sending to the first slave device, (ii) calculate a first migration time of the first slave device based on the measured first communication delay time, the first migration time being calculated to allow a first moment when the first slave device outputs a first signal to be equal to a second moment when a second slave device outputs a second signal, the second slave device being any one of the plurality of slave devices other than the first slave device, and (iii) send the first migration time to the first slave device; and after receiving the first migration time, in response to receiving an instruction to output the first signal from the master device, the first slave device is configured to execute the output of the first signal at a time after a time of the first migration time from the time when the instruction to output the first signal is received from the master device.

2. The communication system according to claim 1, wherein: in response to being activated, the master device is configured to send a plurality of identity data to respectively identify the plurality of slave devices.

3. The communication system according to claim 1, wherein: the plurality of slave devices are configured to respectively output corresponding drive signals to corresponding switching elements included in a power conversion circuit configured to convert direct current into alternating current.

4. The communication system according to claim 3, wherein: the master device is configured to generate drive instructions to be respectively sent to the plurality of slave devices by a space vector method, and at the start of a control period of the space vector method, send the drive instructions, each drive instruction including a level value of a corresponding drive signal and a duration of the level value in the control period; and the first slave device that is any one of the plurality of slave devices is configured to output a drive signal to the corresponding switching element based on the level value and the duration included in the received drive instruction.

5. The communication system according to claim 4, wherein: in response to receiving the drive instruction, the first slave device that is any one of the plurality of slave devices is configured to add status data obtained by sensing to the drive instruction, and then send the drive instruction added with the status data to a communication device arranged next in the communication connection order in the daisy chain.

6. The communication system according to any one of claims 1 to 5, wherein: The first slave device, being any one of the plurality of slave devices, is configured to return a response to the master device in a direction opposite to the direction of receiving the transmission from the master device during the measurement period.

7. The communication system according to any one of claims 1 to 5, wherein, the master device is configured to send a synchronization signal to the first slave device, being any one of the plurality of slave devices; the first slave device includes (i) an oscillation circuit whose clock frequency is adjustable, and (ii) a counter configured to count using the clock signal output by the oscillation circuit; and the first slave device is configured to count the interval time of outputting the synchronization signal as a count value using the counter and adjust the clock frequency to make the count value become a predetermined value.

8. The communication system according to any one of claims 1 to 5, wherein: the master device is configured to measure and monitor the total delay time from the time of sending a signal to the third slave device, being the first one arranged in the communication connection order in the daisy chain among the plurality of slave devices to the time of receiving a response from the fourth slave device, being the last one arranged in the communication connection order in the daisy chain among the plurality of slave devices; and in response to the total delay time having changed relative to a previous measured value, the master device is configured to correct the first migration time of the first slave device, being any one of the plurality of slave devices, according to the ratio of the change.

9. The communication system according to any one of claims 1 to 5, wherein: in response to detecting a communication interruption in the daisy chain between any two slave devices arranged adjacent to each other in the communication connection order in the daisy chain among the plurality of slave devices, the master device is configured to create a communication path, wherein the third slave device, being the last one arranged in the communication connection order from the master device in the daisy chain among the plurality of slave devices, is set to be arranged first in the communication connection order from the master device in the created communication path.

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