Circuit equipment and motor control system

Abstract

To provide a circuit device or the like that can appropriately control the first decay time in motor drive. [Solution] The circuit device 100 includes a current detection circuit 110 that detects the current IS flowing through the motor 20, and a control circuit 120 that controls the drive circuit 150 that drives the motor 20 based on the detection result of the current detection circuit 110. The control circuit 120 includes a charge time measurement unit 122 that measures the charge time tCHG of the motor drive by the drive circuit 150, and a calculation unit 123 that calculates the FastRatio, which is the ratio of the first decay time tFD to the motor drive decay time tDT, according to the measured charge time tCHG.

Description

Technical Field

[0001] The present invention relates to a circuit device, a motor control system, and the like.

Background Art

[0002] Patent Document 1 discloses an apparatus for controlling a stepping motor. When the current exceeds the setpoint level after a blanking period has elapsed since the start of charging, the apparatus transitions the motor drive to fast decay. When the current is below the setpoint level after a blanking period has elapsed since the start of fast decay, the apparatus transitions the motor drive to slow decay. When the current does not exceed the setpoint level after a blanking period has elapsed since the start of charging, the apparatus increases the current as it is and transitions the motor drive to slow decay when the current reaches the setpoint level.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, when a fixed blanking period has elapsed since the start of charging, the current flowing through the motor is compared with the setpoint level, and only the control of decay is switched based on the result. Therefore, there is a risk that the motor current may not be appropriately controlled. For example, there is a risk that suppression of current ripple may be insufficient due to excessive decay, or there may be a disturbance in the current waveform due to insufficient decay.

Means for Solving the Problems

[0005] One aspect of the present disclosure relates to a circuit device including a current detection circuit for detecting a current flowing through a motor, and a control circuit for controlling a drive circuit that drives the motor based on the detection result of the current detection circuit, wherein the control circuit includes a charge time measurement unit for measuring the charge time of the motor drive by the drive circuit, and a calculation unit for calculating the ratio of the first decay time to the decay time of the motor drive according to the measured charge time.

[0006] Another aspect of this disclosure relates to a motor control system including the above-described circuit device and the motor. [Brief explanation of the drawing]

[0007] [Figure 1] An example configuration of a motor control system. [Figure 2] Detailed configuration example of current detection circuit and drive circuit. [Figure 3] An example of the first simulated waveform of motor current when using conventional mixed decay. [Figure 4] A second example of a simulated motor current waveform using conventional mixed decay. [Figure 5] Detailed configuration example of the control circuit in this embodiment. [Figure 6] A diagram illustrating the decay time control performed by the control circuit. [Figure 7] Waveform examples illustrating improved current tracking performance. [Figure 8] A waveform example illustrating the improvement of current ripple. [Figure 9] A waveform example illustrating the improvement of current ripple. [Figure 10] An example of a waveform for the target current value in microstepping control. [Figure 11] An example of a waveform for the target current value in 2-2 phase control. [Figure 12] A waveform example illustrating the effect of resetting the first decay time ratio in 2-2 phase control. [Figure 13]A waveform example illustrating the effect of resetting the first decay time ratio in 2-2 phase control. [Figure 14] An example flow for charge decay control, including charge skipping. [Figure 15] Waveform example illustrating the improvement in current tracking performance due to charge skipping. [Figure 16] State transition diagram of this embodiment. [Figure 17] A state transition diagram of mixed decay as a comparative example. [Modes for carrying out the invention]

[0008] Preferred embodiments of this disclosure will be described in detail below. Note that these embodiments are not intended to unduly limit the scope of the claims, and not all configurations described in these embodiments are necessarily essential.

[0009] Figure 1 shows an example configuration of a motor control system 300. The motor control system 300 includes a motor 20, a circuit device 100 which is a motor driver, a first sense resistor RS1, and a second sense resistor RS2. Sense resistors are also called shunt resistors. The circuit device 100 is, for example, an integrated circuit device in which multiple circuit elements are integrated on a semiconductor substrate. Below, an example is described in which the motor 20 is a stepping motor including a first coil 11 and a second coil 12, but the motor 20 may also be a multiphase stepping motor.

[0010] The circuit device 100 includes a first drive circuit 151 that drives the first coil 11 of the motor 20, and a first current detection circuit 111 that detects the first current flowing through the first sense resistor RS1. The circuit device also includes terminals TSA, TSB, TDA, and TDB. The terminal TSA is connected to one end of the first sense resistor RS1 and the first drive circuit 151. The terminal TSB is connected to one end of the first sense resistor RS1 and the first current detection circuit 111. The terminal TDA is connected to one end of the first coil 11 and the first drive circuit 151. The terminal TDB is connected to the other end of the first coil 11 and the first drive circuit 151.

[0011] Further, the circuit device 100 includes a second drive circuit 152 that drives the second coil 12 of the motor 20, and a second current detection circuit 112 that detects the second current flowing through the second sense resistor RS2. The circuit device also includes terminals TSC, TSD, TDC, and TDD. The terminal TSC is connected to one end of the second sense resistor RS2 and the second drive circuit 152. The terminal TSD is connected to one end of the second sense resistor RS2 and the second current detection circuit 112. The terminal TDC is connected to one end of the second coil 12 and the second drive circuit 152. The terminal TDD is connected to the other end of the second coil 12 and the second drive circuit 152.

[0012] FIG. 2 is a detailed configuration example of the current detection circuit 110 and the drive circuit 150. The current detection circuit 110, the drive circuit 150, the coil 10, and the sense resistor RS in FIG. 2 correspond to the first current detection circuit 111, the first drive circuit 151, the first coil 11, and the first sense resistor RS1 in FIG. 1, or the second current detection circuit 112, the second drive circuit 152, the second coil 12, and the second sense resistor RS2. Also, the terminals TD1, TD2, TS1, and TS2 in FIG. 2 correspond to the terminals TDA, TDB, TSA, and TSB in FIG. 1, or the terminals TDC, TDD, TSC, and TSD.

[0013] The current detection circuit 110 detects whether the input voltage VIP from the terminal TS2 exceeds the voltage corresponding to the target current value, and outputs a current detection signal ITRIP which is the detection result. The input voltage VIP is the voltage corresponding to the current flowing through the sense resistor RS, and VIP = RS × IS during the charging period. IS is the current flowing through the coil and is equivalent to the current flowing through the sense resistor RS. Hereinafter, the current IS may be referred to as the motor current. The current detection circuit 110 includes an amplifier circuit 160, a D / A conversion circuit 190, and a comparator 115.

[0014] The amplifier circuit 160 amplifies the input voltage VIP and outputs the amplified voltage as the output voltage VOUT. The amplifier circuit 160 is, for example, a forward amplifier circuit composed of an operational amplifier and a resistor.

[0015] The D / A conversion circuit 190 performs D / A conversion on the instruction data SDAC indicating the target current value, and outputs the result as the output voltage VDAC. The D / A conversion circuit 190 includes, for example, a ladder resistor circuit and a selection circuit. The ladder resistor circuit divides the power supply voltage VDD into a plurality of voltages. The selection circuit selects a voltage corresponding to the instruction data SDAC from the plurality of voltages and outputs the selected voltage as the output voltage VDAC. The instruction data SDAC is written, for example, from an external processing device of the circuit device 100 to a register (not shown) in the circuit device 100.

[0016] The output voltage VOUT of the amplifier circuit 160 is input to the first input terminal of the comparator 115, and the output voltage VDAC of the D / A conversion circuit 190 is input to the second input terminal. The comparator 115 compares the output voltage VOUT of the amplifier circuit 160 with the output voltage VDAC of the D / A conversion circuit 190, and outputs the result as the current detection signal ITRIP. In the example of FIG. 2, the first input terminal is the positive input terminal and the second input terminal is the negative input terminal, but the reverse may also be possible.

[0017] The drive circuit 150 is an H-bridge circuit and includes switch elements SWA to SWD. One end of switch element SWA is connected to a power node to which the power supply voltage VDD is supplied, and the other end is connected to terminal TD1. One end of switch element SWB is connected to a power node, and the other end is connected to terminal TD2. One end of switch element SWC is connected to terminal TD1, and the other end is connected to terminal TS1. One end of switch element SWD is connected to terminal TD2, and the other end is connected to terminal TS1. Switch element SWA is controlled to be on or off by a pre-drive signal CSA from the control circuit 120. Similarly, switch elements SWB, SWC, and SWD are controlled to be on or off by pre-drive signals CSB, CSC, and CSD from the control circuit 120. Switch elements SWA and SWB are high-side transistors, for example, P-type MOS transistors or N-type MOS transistors. Switch elements SWC and SWD are low-side transistors, for example, N-type MOS transistors.

[0018] The control circuit 120 outputs pre-drive signals CSA, CSB, CSC, and CSD to switch the switch elements of the drive circuit 150 based on the current detection signal ITRIP. The direction of the arrow attached to coil 10 in Figure 2 is considered the positive direction of the current IS. When a positive current IS flows, the control circuit 120 turns on switch elements SWA and SWD and turns off switch elements SWB and SWC during charging. During fast decay, the control circuit 120 turns on switch elements SWB and SWC and turns off switch elements SWA and SWD. During slow decay, the control circuit 120 turns on switch elements SWC and SWD and turns off switch elements SWA and SWB. On the other hand, when a negative current IS flows, the control circuit 120 turns on switch elements SWB and SWC and turns off switch elements SWA and SWD during charging. During the fast decay, the control circuit 120 turns on the switch elements SWA and SWD and turns off the switch elements SWB and SWC. During the slow decay, the control circuit 120 turns on the switch elements SWC and SWD and turns off the switch elements SWA and SWB.

[0019] Figure 3 shows an example of the first simulation waveform of the motor current when using conventional mixed decay. In mixed decay, both fast decay and slow decay are performed, and the fast decay time and slow decay time are fixed. Figure 3 shows the signal waveform of the current flowing through the coil of an HB motor under 1500 pps microstepping control. The unit of the horizontal axis is μsec, and the unit of the vertical axis is mA.

[0020] The target current value is a waveform that approximates a sine wave using microstepping. Ideally, the current flowing through the coil should be a sine wave that traces the sine wave of the target current value. However, as shown in the current waveform in the area indicated by the dotted circle A1, when the absolute value of the target current value decreases, the motor current deviates from the target current due to the motor's back electromotive force. The faster the motor rotates, the larger the back electromotive force becomes, making the above deviation more likely to occur. When such current waveform disturbances occur, the motor vibration increases, making it more prone to losing steps, or the motor noise increases.

[0021] Figure 4 shows a second simulation waveform example of motor current when using conventional mixed decay. Figure 4 shows the signal waveform of the current flowing through the coil of an HB motor under 400 pps microstepping control. The units for each axis are the same as in Figure 3.

[0022] In Figure 4, the current waveform is not distorted due to the low rotational speed. However, in mixed decay, the time of the first decay is fixed, resulting in excessive decay and charging, which increases the current ripple ΔLPa. Since the coil's energy is discharged during decay, a large decay time causes excess energy to be discharged. This leads to either increased current consumption to recharge the discharged energy, or increased heat generation due to the discharge of excess energy. Furthermore, since the torque is controlled by the motor current, a large ripple results in large torque fluctuations.

[0023] Therefore, in this embodiment, the control circuit 120 changes the ratio of the first decay time to the decay time according to the charge time. Figure 5 shows a detailed configuration example of the control circuit 120 in this embodiment. The control circuit 120 includes a charge decay control unit 121, a charge time measurement unit 122, and a calculation unit 123. Figure 6 is an explanatory diagram of the decay time control performed by the control circuit 120.

[0024] The charge-decay control unit 121 controls the pre-drive signals CSA, CSB, CSC, and CSD to cause the drive circuit 150 to perform charging, fast decay, or slow decay. The on / off states of the switch elements SWA, SWB, SWC, and SWD in each state are as described above.

[0025] The charge decay control unit 121 maintains the charge for at least the blanking time tBL after the charging has started. After the blanking time tBL has elapsed, when the current detection signal ITRIP changes from a low level to a high level, that is, when it is detected that the current IS flowing through the coil 10 has reached the target current value, the charge decay control unit 121 terminates the charge.

[0026] The charge decay control unit 121 enables the charge enable signal ENC from disabled when charging begins, and disables the charge enable signal ENC from enabled when charging ends. The charge time measurement unit 122 measures the time during which the charge enable signal ENC is enabled as the charge time tCHG. For example, the charge time measurement unit 122 is a counter and measures the charge time tCHG by performing a counting operation when the charge enable signal ENC is enabled.

[0027] The calculation unit 123 determines the fast decay time tFD and the slow decay time tSD by PID control according to the charge time tCHG.

[0028] Specifically, the calculation unit 123 calculates the difference tDF between the charge time tCHG and the target time tTG using the following equations (1) and (2). The blanking time tBL and the set value tSET are predetermined values. For example, both the blanking time tBL and the set value tSET are 1 μsec, but are not limited to this. tDF = tTG - tCHG ... (1) tTG = tBL + tSET ... (2)

[0029] The calculation unit 123 uses the difference tDF to calculate the FastRatio, which is the ratio of the first decay time tFD to the decay time tDT, according to equations (3) to (6) below. n is a number indicating the calculation timing in the time series. Kp, Ki, and Kd are the gains of each term in the PID control and are set in advance. * indicates multiplication. k indicates the number of stages in the FIFO memory that temporarily stores dataP. FastRatio(n) = FastRatio(n-1) +(Kp*dataP(n))+(Ki*dataI(n))+(Kd*dataD(n)) ···(3) dataP(n)=tDF / tDT ···(4) dataI(n)=dataP(n)+dataP(n-1)+ ··· +dataP(nk-1) ···(5) dataD(n)=dataP(n-1)-dataP(n) ···(6)

[0030] The calculation unit 123 uses the ratio FastRatio(n) to calculate the fast decay time tFD and the slow decay time tSD according to equations (7) and (8) below. The decay time tDT is a preset value. tFD=tDT*FastRatio(n) ···(7) tSD = tDT - tFD ... (8)

[0031] The target time tTG, decay time tDT, and gains Kp, Ki, and Kd are set, for example, by an external processing unit to a register (not shown) within the circuit device 100, or are pre-stored in a non-volatile memory (not shown) included in the circuit device 100.

[0032] The charge decay control unit 121 initiates fast decay, then initiates slow decay after the fast decay time tFD has elapsed, and restarts charging after the slow decay time tSD has elapsed. Thereafter, the same decay time control is repeated.

[0033] According to the PID control described above, the FastRatio, which is the ratio of the fast decay time tFD, is adaptively controlled according to the charge time tCHG. That is, when the motor current is significantly lower than the target current value, the charge time tCHG increases, and the fast decay time tFD decreases. Conversely, when the difference between the motor current and the target current value is small, the charge time tCHG decreases, and the fast decay time tFD increases. This improves the motor current's ability to track the target current value, thereby reducing the current waveform distortion mentioned above. Also, because the fast decay time tFD is not fixed, current ripple can be reduced.

[0034] The calculation unit 123 may also calculate the ratio FastRatio(n) by PD control as shown in equation (9) below. The same effect as above can be obtained by PD control. FastRatio(n)=FastRatio(n-1)+(Kp*dataP(n))+(Kd*dataD(n)) ···(9)

[0035] Figure 7 shows an example waveform illustrating the improvement in current tracking performance. Figure 7 shows the signal waveform of the current flowing through the coil of the HB motor in 1500 pps microstep control. The units for each axis are the same as in Figure 3. The upper figure is an example of a simulated motor current waveform when using conventional mixed decay, and is a reproduction of Figure 3. The lower figure is an example of a simulated motor current waveform when PID control of this embodiment is performed.

[0036] The induced current generated in the motor by back electromotive force cannot be completely attenuated by fast decay and slow decay, resulting in the current waveform distortion shown in the upper figure. In this embodiment, when the motor current is likely to exceed the target current value, the charge time is shortened, and the proportion of the fast decay time is increased by PID control. As a result, the induced current generated in the motor can be attenuated, and the tracking ability of the motor current with respect to the target current value is improved, as shown in the lower figure.

[0037] Figures 8 and 9 show waveform examples illustrating the improvement of current ripple. Figures 8 and 9 show the signal waveforms of the current flowing through the coil of the HB motor in 400 pps microstep control. The units for each axis are the same as in Figure 3. Figure 8 is an example of a simulation waveform when using conventional mixed decay. The lower panel is an enlarged view of a part of the upper panel. Figure 9 is an example of a simulation waveform when PID control of this embodiment is performed. The lower panel is an enlarged view of a part of the upper panel.

[0038] In mixed decay, the first decay time is fixed, so it is set to ensure the necessary first decay time under the most severe decay conditions. Therefore, under less severe decay conditions, the first decay is excessive, resulting in a large current drop, which is repeatedly restored by charging. Consequently, as shown in Figure 8, the current ripple ΔLPa is large in mixed decay. According to this embodiment, the ratio of the first decay time is optimized by PID calculation, so an appropriate first decay time is achieved under both severe and less severe decay conditions. When decay is not severe, the slow decay time becomes longer, and the current drop is small. Consequently, as shown in Figure 9, the current ripple ΔLPb is small in this embodiment.

[0039] The embodiments described below may be added to the embodiments shown in Figures 1 to 9 described above.

[0040] An embodiment for resetting the FastRatio(n) ratio of the first decay time tFD will be described using Figures 10 to 13.

[0041] Figure 10 shows an example of the waveform of the target current value in microstep control. In Figure 10, the target current value is shown as a sine wave, but in reality, a sine wave is approximated by discretely changing the target current value through microstepping. In this embodiment, instruction data SDAC indicating the target current value is further input to the calculation unit 123. As shown by the dotted circles B1 and B2, in the first PID calculation after the target current value crosses zero, the calculation unit 123 resets the ratio FastRatio(n) of the first decay time tFD to its initial value. Specifically, when the calculation unit 123 performs the first PID calculation after the target current value changes from zero to a non-zero value, it does not calculate the ratio FastRatio(n) using the above equation (3), but uses a predetermined initial value as the ratio FastRatio(n). In microstep control, the initial value is, for example, 0%.

[0042] In microstep control, the absolute value of the target current decreases before the target current value becomes zero, so the first decay time tFD is short. After the target current value passes zero, the absolute value of the target current value increases, so the first decay time tFD is long. In other words, the trend of the ratio FastRatio(n) changes at the point when the target current value becomes zero. By resetting the ratio FastRatio(n) at such a boundary without using equation (3) above, it is possible to quickly follow the change in the above trend, thus further improving the motor current's ability to follow the target current value.

[0043] Figure 11 shows an example of the waveform of the target current value in 2-2 phase control. In this example, instruction data SDAC indicating the target current value is further input to the calculation unit 123. In 2-2 phase control, there are only two types of target current values: positive and negative. As shown by the dotted circles C1 and C2, in the first PID calculation after the target current value crosses zero, the calculation unit 123 resets the FastRatio(n) ratio of the first decay time tFD to its initial value. Specifically, when the calculation unit 123 performs the first PID calculation after the positive and negative values ​​of the target current value have switched, it does not calculate the FastRatio(n) ratio using equation (3) above, but uses a predetermined initial value as the FastRatio(n) ratio. In microstep control, the initial value is a value greater than zero, for example, 25%. Note that a similar reset can also be applied to 1-2 phase control.

[0044] Figures 12 and 13 are waveform examples illustrating the effect of resetting the first decay time ratio in 2-2 phase control. The units for each axis are the same as in Figure 3. Figure 12 is an example of a simulated motor current waveform without resetting, and Figure 13 is an example of a simulated motor current waveform with resetting.

[0045] In 2-2 phase control, when the positive and negative values ​​of the target current switch, a long charging period is performed to reverse the direction of the motor current. At this time, the charging time tCHG becomes very long, so the fast decay time tFD determined by equation (3) above becomes long, and there is a possibility that excessive fast decay will occur. As shown by the dotted circles D1 and D2 in Figure 12, excessive fast decay causes the motor current to exceed the target current value by a large margin. According to this embodiment, by resetting the ratio FastRatio(n) at the timing when the target current value crosses zero, an appropriate fast decay time is achieved. Also, since the target current value becomes constant after the switch, a certain amount of fast decay time is required, so the reset value of the ratio FastRatio is set to a value greater than zero. As shown by the dotted circles E1 and E2 in Figure 13, the discrepancy between the motor current and the target current value is reduced because the fast decay time ratio has been reset.

[0046] An embodiment of charge skipping will be described using Figures 14 and 15.

[0047] Figure 14 shows an example of a charge decay control flow including charge skipping. In step S1, the charge decay control unit 121 determines whether the motor current exceeds the target current value before charging begins.

[0048] If the motor current does not exceed the target current value in step S1, the charge decay control unit 121 performs the charge in step S2. When the motor current exceeds the target current value due to the charge, the charge decay control unit 121 performs PID control to determine the FastRatio, performs the fast decay in step S3 and the slow decay in step S4, and returns to step S1.

[0049] If the motor current exceeds the target current value in step S1, the charge decay control unit 121 skips the charge in step S2, sets the charge time tCHG to zero, and performs PID control to determine the FastRatio. The charge decay control unit 121 then performs the fast decay in step S3 and the slow decay in step S4, and returns to step S1.

[0050] Figure 15 shows an example waveform illustrating the improvement in current tracking performance due to charge skipping. Figure 15 shows the signal waveform of the current flowing through the coil of a PM motor in 280 pps microstepping control. The units for each axis are the same as in Figure 3. The solid line shows the motor current waveform, and the dotted line shows the target current value waveform. The target current value is shown as a sine wave, but in reality, it is a waveform that approximates a sine wave by microstepping. The upper figure is an example of a simulated waveform without charge skipping. The lower figure is an example of a simulated waveform with charge skipping.

[0051] In mixed decay, charging occurs for at least the blanking time tBL, so charging always occurs even when the motor current exceeds the target current value. Therefore, as shown by the dotted circle F1 in the upper figure, the motor current's ability to track the target current value deteriorates as the absolute value of the target current value decreases. According to this embodiment, when the motor current exceeds the target current value, the charging time is shortened, and the first decay time becomes zero through PID calculation. By utilizing this to skip charging, charging does not occur and only decay takes place. As a result, as shown by the dotted circle F2 in the lower figure, the motor current's ability to track the target current value can be improved.

[0052] Using Figures 16 and 17, embodiments for skipping the first decay or slow decay will be described.

[0053] Figure 16 is a state transition diagram of this embodiment. The charge decay control unit 121 transitions to the first decay state of state ST2 when condition CA1 is met during the charge in state ST1. Condition CA1 is that the blanking time tBL has elapsed, the motor current has exceeded the target current value, and the first decay time tFD is not zero.

[0054] The charge decay control unit 121 transitions to the slow decay state of state ST3 when condition CA2 is met during the first decay of state ST2. Condition CA2 is that the first decay time tFD, obtained by PID calculation, has elapsed.

[0055] The charge decay control unit 121 transitions to the charge state of ST1 when condition CA3 is met during the slow decay of state ST3. Condition CA3 is that the slow decay time tSD, obtained by PID calculation, has elapsed.

[0056] The charge decay control unit 121 skips the slow decay of state ST3 and transitions to the charge state ST1 when condition CA4 is met during the first decay of state ST2. Condition CA4 is that the first decay time tFD obtained by PID calculation has elapsed, and the slow decay time tSD obtained by PID calculation is zero. In this case, the FastRatio is 100%, and the first decay time tFD is the same as the decay time tDT.

[0057] The charge decay control unit 121 skips the fast decay of state ST2 and transitions to the slow decay of state ST3 when condition CA5 is met during charging in state ST1. Condition CA5 is that the blanking time tBL has elapsed, the motor current has exceeded the target current value, and the fast decay time tFD is zero. In this case, the FastRatio is 0%, and the slow decay time tSD is the same as the decay time tDT.

[0058] Figure 17 shows a state transition diagram of mixed decay as a comparative example. The charge decay control unit 121 transitions to the first decay state of ST2 when condition CB1 is met during charging in state ST1. Condition CB1 is that the blanking time tBL has elapsed and the motor current has exceeded the target current value.

[0059] The charge decay control unit 121 transitions to the slow decay state of state ST3 when condition CB2 is met during the first decay of state ST2. Condition CB2 is that a fixed first decay time tFD has elapsed.

[0060] The charge decay control unit 121 transitions to charge state ST1 when condition CB3 is met during the slow decay of state ST3. Condition CB3 is that a fixed slow decay time tSD has elapsed.

[0061] In mixed decay, both fast decay and slow decay always occur, which can lead to excessive or insufficient decay. According to this embodiment shown in Figure 16, fast decay or slow decay is adaptively skipped based on PID control, thus reducing excessive or insufficient decay. This further improves the motor current's ability to track the target current value, or further reduces current ripple.

[0062] In this embodiment described above, the circuit device 100 includes a current detection circuit 110 that detects the current IS flowing through the motor 20, and a control circuit 120 that controls the drive circuit 150 that drives the motor 20 based on the detection result of the current detection circuit 110. The control circuit 120 includes a charge time measurement unit 122 that measures the charge time tCHG of the motor drive by the drive circuit 150, and a calculation unit 123 that calculates the FastRatio, which is the ratio of the first decay time tFD to the decay time tDT of the motor drive, according to the measured charge time tCHG.

[0063] According to this embodiment, the first decay time tFD is adaptively controlled according to the charge time tCHG. This reduces the excess or deficiency of the decay, thereby improving the motor current's ability to track the target current value or reducing current ripple.

[0064] Furthermore, as explained in equations (1) to (9) above, the calculation unit 123 may increase the FastRatio of the fast decay time tFD as the charge time tCHG decreases.

[0065] When the current IS flowing through the motor 20 is close to or exceeds the target current value, the charge time tCHG is shortened. At this time, by lengthening the first decay time tFD, the induced current of the motor 20 can be attenuated by the first decay. This improves the motor current's ability to track the target current value.

[0066] Furthermore, as explained in equations (1) to (9) above, the calculation unit 123 may calculate the FastRatio, which is the ratio of the first decay time tFD, according to the difference tDF between the charge time tCHG and the target time tTG.

[0067] According to this embodiment, when the charge time tCHG and the target time tTG diverge, the charge time tCHG can be brought to converge to the target time tTG by increasing or decreasing the FastRatio of the fast decay time tFD. By performing such adaptive control of the fast decay time tFD, the responsiveness of the motor current to the target current value is improved, or current ripple is reduced.

[0068] Furthermore, as explained in equations (1) to (9) above, the calculation unit 123 may calculate the FastRatio, which is the ratio of the first decay time tFD, in accordance with the difference tDF and the change in the difference tDF. In the example of equations (1) to (9) above, dataD corresponds to the "change in the difference tDF".

[0069] According to this embodiment, the fast decay time tFD and the slow decay time tSD can be determined by PD control based on the charge time tCHG.

[0070] Furthermore, as explained in equations (1) to (8) above, the calculation unit 123 may also calculate the FastRatio, the ratio of the first decay time tFD, in accordance with the difference tDF, the cumulative value of the difference tDF, and the change in the difference tDF. In the example of equations (1) to (8) above, dataI corresponds to the "cumulative value of the difference tDF".

[0071] According to this embodiment, the fast decay time tFD and the slow decay time tSD can be determined by PID control based on the charge time tCHG.

[0072] Furthermore, as explained in equations (1) to (9) above, the calculation unit 123 may update the FastRatio by determining the change in the FastRatio ratio from the charge time tCHG to the first decay time tFD at the end of motor drive charging, and adding this change to the previous FastRatio ratio. Note that the "change in the FastRatio ratio" corresponds to the 2nd to 4th terms on the right side in the example of equation (3) above, and to the 2nd and 3rd terms on the right side in the example of equation (9) above.

[0073] According to this embodiment, the change in the FastRatio ratio of the first decay time tFD is determined based on the charge time tCHG, and the FastRatio ratio is updated based on this change, thereby calculating the FastRatio ratio according to the charge time tCHG.

[0074] Furthermore, as explained in Figures 10 to 13, the calculation unit 123 may reset the FastRatio, the ratio of the fast decay time tFD, to its initial value when the target current value of the current IS flowing through the motor 20 crosses zero. Note that "crossing zero" of the target current value means that the target current value changes from zero to positive or negative, from positive to negative, or from negative to positive.

[0075] When the target current value crosses zero, the required amount of fast decay changes significantly before and after the crossover, which may impair the motor current's ability to track the target current value. In this embodiment, when the target current value crosses zero, the previous ratio FastRatio is reset to its initial value rather than being updated based on the change. This makes it easier to maintain current tracking even when the required amount of fast decay changes significantly.

[0076] Furthermore, as explained in Figures 10 to 13, the initial value may be zero in the microstep control of motor 20. The initial value may also be a value greater than zero in the two-phase control of motor 20.

[0077] In microstep control, immediately after the target current crosses zero, charging is dominant and a small fast decay is sufficient, so the FastRatio (ratio of the fast decay time tFD) can be zero. In two-phase control, immediately after the target current crosses zero, a certain amount of fast decay is necessary because a long charging period has occurred, so the FastRatio (ratio of the fast decay time tFD) should be set to a value greater than zero.

[0078] In this embodiment, the control circuit 120 may also include a charge-decay control unit 121 that controls the charging and decay of the motor drive. The charge-decay control unit 121 may perform charging from the start of charging until the current value detected by the current detection circuit 110 exceeds the target current value of the current IS flowing to the motor 20. The charge-decay control unit 121 may control the fast decay and slow decay using a fast decay time tFD and a slow decay time tSD based on the fast decay time tFD ratio (FastRatio).

[0079] According to this embodiment, the charge decay control unit 121 can control the fast decay and slow decay based on the FastRatio, which is the ratio of the fast decay time tFD calculated by the calculation unit 123.

[0080] Furthermore, as explained in Figures 14 and 15, the charge decay control unit 121 may skip charging if the current value detected by the current detection circuit 110 exceeds the target current value before charging begins.

[0081] According to this embodiment, in situations where the motor current exceeds the target current value, the charge time tCHG becomes shorter, and the first decay time tFD becomes zero through PID calculation. By utilizing this, charging is skipped, and only decay occurs without charging. This improves the motor current's ability to track the target current value.

[0082] Furthermore, as explained in Figures 16 and 17, the charge decay control unit 121 may skip the motor drive fast decay control process if the FastRatio, which is the ratio of the fast decay time tFD determined according to the charge time tCHG, becomes zero. The charge decay control unit 121 may also skip the motor drive slow decay control process if the slow decay time tSD, which is based on the FastRatio, which is the ratio of the fast decay time tFD determined according to the charge time tCHG, becomes zero.

[0083] According to this embodiment, since fast decay or slow decay is adaptively skipped based on PID control, excessive or insufficient decay can be reduced. This further improves the motor current's ability to track the target current value, or further reduces current ripple.

[0084] In this embodiment, the calculation unit 123 may set the time at a ratio FastRatio determined according to the charge time tCHG from a given decay time tDT as the first decay time tFD, and set the time other than the first decay time tFD as the slow decay time tSD.

[0085] According to this embodiment, the fast decay time tFD and the slow decay time tSD are determined from the FastRatio, which is determined according to the charge time tCHG.

[0086] In this embodiment, the current detection circuit 110 may also detect whether the current IS flowing through the motor 20 has reached a target current value. The charge time measurement unit 122 may measure the time from when the motor drive charging starts until it is detected that the current IS flowing through the motor 20 has reached a target current value as the charge time tCHG.

[0087] According to this embodiment, a charge time tCHG is obtained that corresponds to the degree of deviation between the motor current at the start of charging and the target current value, and the first decay time tFD is controlled according to the charge time tCHG. By performing such adaptive control of the first decay time tFD, the responsiveness of the motor current to the target current value is improved, or current ripple is reduced.

[0088] In this embodiment, the motor 20 may be a stepping motor, and the drive circuit 150 may be a bridge circuit.

[0089] In this embodiment, the motor control system 300 includes the circuit device 100 described in any of the above descriptions and the motor 20.

[0090] Although this embodiment has been described in detail above, it will be readily apparent to those skilled in the art that many modifications are possible without substantially departing from the novelty and effects of this disclosure. Therefore, all such modifications are included within the scope of this disclosure. For example, any term that appears at least once in the specification or drawings together with a broader or synonymous term may be replaced with that different term anywhere in the specification or drawings. Furthermore, all combinations of this embodiment and its modifications are also included within the scope of this disclosure. In addition, the configuration and operation of the current detection circuit, control circuit, drive circuit, circuit device, motor, and motor control system, etc., are not limited to those described in this embodiment, and various modifications are possible. [Explanation of Symbols]

[0091] 10... Coil, 20... Motor, 100... Circuit device, 110... Current detection circuit, 115... Comparator, 120... Control circuit, 121... Charge decay control unit, 122... Charge time measurement unit, 123... Calculation unit, 150... Drive circuit, 160... Amplification circuit, 190... D / A conversion circuit, 300... Motor control system, ENC... Charge enable signal, ITRIP... Current detection signal, RS... Sense resistor, tBL... Blanking time, tCHG... Charge time, tDF... Difference, tDT... Decay time, tFD... Fast decay time, tSD... Slow decay time, tTG... Target time

Claims

1. A current detection circuit that detects the current flowing through the motor, A control circuit that controls the drive circuit for driving the motor based on the detection result of the current detection circuit, Includes, The aforementioned control circuit is A charge time measurement unit for measuring the charge time of the motor drive by the aforementioned drive circuit, A calculation unit that calculates the ratio of the first decay time to the motor drive decay time according to the measured charge time, A circuit device characterized by including the following.

2. In the circuit device described in claim 1, The aforementioned arithmetic unit, A circuit device characterized in that the shorter the charge time, the larger the ratio of the first decay time.

3. In the circuit device described in claim 1, The aforementioned arithmetic unit, A circuit device characterized by calculating the ratio of the first decay time according to the difference between the charge time and the target time.

4. In the circuit device described in claim 3, The aforementioned arithmetic unit, A circuit device characterized by calculating the ratio of the first decay time in accordance with the difference and the change in the difference.

5. In the circuit device described in claim 4, The aforementioned arithmetic unit, A circuit device characterized by calculating the ratio of the first decay time according to the difference, the cumulative value of the difference, and the change in the difference.

6. In the circuit device described in claim 1, The aforementioned arithmetic unit, A circuit device characterized in that, at the end of the motor drive charge, the amount of change in the ratio of the charge time to the first decay time is determined, and the ratio is updated by adding the amount of change to the previous ratio.

7. In the circuit device described in claim 6, The aforementioned arithmetic unit, A circuit device characterized in that when the target current value of the current flowing through the motor crosses zero, the ratio of the first decay time is reset to an initial value.

8. In the circuit device described in claim 7, The aforementioned initial value is, In the microstepping control of the motor, the value is zero. A circuit device characterized in that the two-phase control of the motor is greater than zero.

9. In the circuit device described in claim 1, The aforementioned control circuit is Includes a charge-decay control unit that controls the charging and decay of the motor drive, The charge decay control unit is, After the charging starts, the charging is continued until the current value detected by the current detection circuit exceeds the target current value of the current flowing through the motor. A circuit device characterized by controlling the fast decay and slow decay based on the ratio of the fast decay time and the slow decay time.

10. In the circuit device described in claim 9, The charge decay control unit is, A circuit device characterized in that, before the start of the charge, if the current value detected by the current detection circuit exceeds the target current value, the charge is skipped.

11. In the circuit device described in claim 9, The charge decay control unit is, If the ratio of the first decay time determined according to the charge time becomes zero, the control process for the motor drive's first decay is skipped. A circuit device characterized in that, when the slow decay time, which is based on the ratio of the first decay time determined according to the charge time, becomes zero, the control process for the slow decay of the motor drive is skipped.

12. In the circuit device described in claim 1, The aforementioned arithmetic unit, A circuit device characterized in that, of a given decay time, a proportion of the time determined according to the charge time is set as the first decay time, and the time other than the first decay time is set as the slow decay time.

13. In the circuit device described in claim 1, The current detection circuit is, The system detects whether the current flowing through the motor has reached a target current value. The aforementioned charging time measurement unit is A circuit device characterized in that it measures the time from when the motor drive charging is started until it is detected that the current flowing through the motor has reached the target current value as the charging time.

14. In the circuit device described in claim 1, The motor is a stepping motor, The aforementioned drive circuit is a bridge circuit, and the circuit device is characterized in that it is a bridge circuit.

15. A circuit device according to any one of claims 1 to 14, The aforementioned motor, A motor control system characterized by including the following.

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