Motor drive control device, motor unit, electronic circuit, and control method

Abstract

To suppress heat generation in a regeneration circuit.SOLUTION: A motor drive control device 1 has a motor drive circuit 12 driving a motor 2 based on a drive control signal Sd, a regeneration circuit 17 having a resistor 18 and a switching element SWr mutually connected in series between a first line Lp and a second line Lg to which counter electromotive force is supplied from the motor 2, a voltage detection circuit 16 detecting voltage Vpg between the first line Lp and the second line Lg, and outputting a voltage detection signal Sp according to the voltage Vpg, and a control circuit 11 generating the drive control signal Sd and controlling on / off of the switching element SWr by generating a control signal Sx so that the voltage Vpg may not exceed a threshold value Vth. The control circuit 11 increases the threshold value Vth according to a rise of a temperature of the resistor 18.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a motor drive control device, a motor unit, an electronic circuit, and a control method.

Background Art

[0002] In a large-sized motor unit applied to an EBB (Electric Brake Booster) or the like, a regeneration circuit may be provided to absorb (consume) the back electromotive force generated in the coil (inductor) of the motor and suppress the rise in the voltage of the power supply line when the motor decelerates or the like.

[0003] For example, Patent Document 1 discloses a motor drive device including a regeneration consumption circuit having a switching element and a (brake) resistor connected in series between DC power supply lines, and a regeneration control unit that executes regeneration consumption control for consuming the back electromotive force generated with deceleration by turning on the switching element when a detection value of the main circuit voltage, which is the voltage between the DC power supply lines, exceeds a predetermined first threshold voltage during deceleration of the electric motor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the regeneration circuit represented by Patent Document 1, by turning on the switching element, it is possible to suppress the rise in the voltage of the power supply line to which the back electromotive force is supplied from the coil. On the other hand, while the switching element is on, a large current flows, so the switching element and the resistor connected in series to the switching element generate heat. As a countermeasure, it is conceivable to increase the rated power to suppress heat generation in the regeneration circuit, but there is a problem that the size of the resistor increases.

[0006] Therefore, prior to the present invention, the inventor of the present application considered restricting the period during which the switching element is turned on in order to suppress heat generation. That is, the switching element is continuously turned on for a certain period in the regeneration circuit, and then the switching element is turned off. According to this, heat generation of the switching element and the resistor can be suppressed. However, in this method, since the back electromotive force cannot be sufficiently absorbed, it became clear from the study by the inventor that when the switching element is turned off after a certain period of time, the voltage rises sharply again.

[0007] The present invention is for solving the above-described problems, and an object thereof is to suppress heat generation in a regeneration circuit.

Means for Solving the Problems

[0008] A motor drive control device according to a typical embodiment of the present invention includes a motor drive circuit that drives a motor based on a drive control signal for controlling the drive of the motor, a first line to which a back electromotive force is supplied from the motor, and a second line having a lower potential than the first line, a regeneration circuit having a resistor and a switching element connected in series with each other, a voltage detection circuit that detects a voltage between the first line and the second line and outputs a voltage detection signal corresponding to the detected voltage, a control circuit that generates the drive control signal and generates a control signal based on the voltage detection signal so that the voltage between the first line and the second line does not exceed a threshold value, and controls the on / off of the switching element based on the control signal, and the control circuit is characterized in that the threshold value is increased in accordance with an increase in the temperature of the resistor.

Advantages of the Invention

[0009] According to one aspect of the present invention, it is possible to suppress heat generation in the regeneration circuit.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 4

Figure 5

Figure 6

Figure 7A

Figure 7B

Figure 8

Mode for Carrying Out the Invention

[0011] 1. Outline of Embodiment First, an outline of typical embodiments of the invention disclosed in the present application will be described. In the following description, as an example, reference numerals in the drawings corresponding to the components of the invention are described with parentheses.

[0012] [1] A motor drive control device (1, 1A) according to a typical embodiment of the present invention includes a motor drive circuit (12) that drives a motor (2) based on a drive control signal (Sd) for controlling the drive of the motor (2), a first line (Lp) to which a back electromotive force is supplied from the motor, and a regenerative circuit (17) having a resistor (18) and a switching element (SWr) connected in series between the first line and a second line (Lg) having a lower potential than the first line, a voltage detection circuit (16) that detects a voltage (Vpg) between the first line and the second line and outputs a voltage detection signal (Sp) corresponding to the detected voltage, and a control circuit (11, 11A) that generates the drive control signal and generates a control signal (Sx) based on the voltage detection signal so that the voltage between the first line and the second line does not exceed a threshold value (Vth), and controls the on / off of the switching element based on the control signal. The control circuit is characterized in that it increases the threshold value in response to an increase in the temperature of the resistor.

[0013] [2] In the motor drive control device (1) according to [1] above, when a state in which the voltage between the first line and the second line exceeds the threshold value continues for a predetermined time (Tth) while the threshold value is set to a first value (VL), the threshold value may be increased from the first value.

[0014] [3] In the motor drive control device according to [2] above, when the voltage (Vpg) between the first line and the second line drops below the first value while the threshold value is set to a value greater than the first value, the control circuit may lower the threshold value to the first value.

[0015] [4] The motor drive control device (1A) according to [1] above further includes a temperature sensor (20) that detects temperature. When the measured value of the temperature detected by the temperature sensor exceeds a predetermined temperature reference value while the threshold value is set to a first value, the control circuit (11A) may increase the threshold value from the first value.

[0016] 〔5〕In the motor drive control device according to the above 〔4〕, the temperature sensor may be arranged adjacent to the resistor.

[0017] 〔6〕In the motor drive control device according to the above 〔5〕, at least a part of the temperature sensor may be in contact with at least a part of the resistor.

[0018] 〔7〕In the motor drive control device according to any one of the above 〔2〕 to 〔6〕, the control circuit may increase the threshold value from the first value to a second value (VH) greater than the first value.

[0019] 〔8〕In the motor drive control device according to any one of the above 〔1〕 to 〔7〕, when increasing the threshold value, the control circuit may linearly change the threshold value.

[0020] 〔9〕In the motor drive control device according to any one of the above 〔3〕 to 〔8〕, when decreasing the threshold value, the control circuit may linearly change the threshold value.

[0021] 〔10〕In the motor drive control device according to any one of the above 〔1〕 to 〔9〕, the control circuit may generate a PWM signal such that the voltage between the first line and the second line matches the threshold value, and output it as the control signal.

[0022] 〔11〕A motor unit (100) according to a typical embodiment of the present invention includes the motor drive control device (1) according to any one of the above 〔1〕 to 〔10〕, and the motor (2) driven by the motor drive control device.

[0023]

[12] An electronic circuit (30) according to a representative embodiment of the present invention includes a regeneration circuit (17) having a resistor (18) and a switching element (SWr) connected in series between a first line (Lp) supplied with a back electromotive force from a coil and a second line (Lg) having a lower potential than the first line, a voltage detection circuit (16) that detects a voltage (Vpg) between the first line and the second line and outputs a voltage detection signal (Sp) corresponding to the detected voltage, and a control circuit (11) that controls on / off of the switching element so that the voltage between the first line and the second line does not exceed a threshold value (Vth). The control circuit is characterized in that the threshold value is increased in accordance with an increase in the temperature of the resistor.

[0024]

[13] In the electronic circuit according to

[12] above, when a state in which the voltage between the first line and the second line exceeds the threshold value continues for a predetermined time (Tth) while the threshold value is set to a first value, the control circuit may increase the threshold value from the first value.

[0025]

[14] The electronic circuit according to

[12] above further includes a temperature sensor (20) that detects temperature. When a measured value of the temperature detected by the temperature sensor exceeds a predetermined temperature reference value, the control circuit may increase the threshold value from the first value.

[0026]

[15] A control method according to a representative embodiment of the present invention includes a first step (S12) of driving a motor based on a drive control signal for controlling driving of the motor, a second step (S13) of detecting a voltage between a first line supplied with a back electromotive force from the motor and a second line having a lower potential than the first line, a third step (S14) of controlling on / off of a switching element in a regeneration circuit having a resistor and the switching element connected in series between the first line and the second line so that the voltage detected in the second step does not exceed a threshold value, and a fourth step (S15 to S17, S33 to S35) of increasing the threshold value in accordance with an increase in the temperature of the resistor.

[0027] 〔16〕In the control method described in the above

[15] , the fourth step may include a step (S15 to S17) of increasing the threshold value from the first value when a state where the voltage exceeds the threshold value continues for a predetermined time (Tth) while the threshold value is set to the first value.

[0028] 〔17〕In the control method described in the above

[15] , the regeneration circuit includes a temperature sensor (20) for detecting temperature, and the fourth step may include a step (S33 to S35) of increasing the threshold value from the first value when a measured value of the temperature detected by the temperature sensor exceeds a predetermined temperature reference value.

[0029] 〔18〕The control method according to a typical embodiment of the present invention is a control method for a regeneration circuit having a resistor and a switching element connected in series with each other between a first line to which a back electromotive force is supplied from a coil and a second line having a lower potential than the first line, the method including: a first step (S13) of detecting a voltage between the first line and the second line; a second step (S14) of controlling on / off of the switching element (SWr) so that the voltage detected in the first step does not exceed a threshold value; and a third step (S15 to S17, S33 to S35) of increasing the threshold value in response to an increase in temperature of the resistor.

[0030] 〔19〕In the control method described in the above

[18] , the third step may include a step (S15 to S17) of increasing the threshold value from the first value when a state where the voltage exceeds the threshold value continues for a predetermined time (Tth) while the threshold value is set to the first value.

[0031] 〔20〕In the control method described in the above

[18] , the regeneration circuit includes a temperature sensor (20) for detecting temperature, and the third step may include a step (S33 to S35) of increasing the threshold value from the first value when a measured value of the temperature detected by the temperature sensor exceeds a predetermined temperature reference value.

[0032] 2. Specific Examples of Embodiments Hereinafter, specific examples of embodiments of the present invention will be described with reference to the drawings. In the following description, the same reference numerals are given to the common components in each embodiment, and the repeated description will be omitted.

[0033] ≪Embodiment 1≫ FIG. 1 is a diagram showing the configuration of a motor unit 100 including a motor drive control device 1 according to Embodiment 1.

[0034] The motor unit 100 shown in FIG. 1 is applied to, for example, an EBB (Electric Brake Booster) or the like.

[0035] As shown in FIG. 1, the motor unit 100 has, for example, a motor drive control device 1 and a motor 2.

[0036] The motor 2 is, for example, a brushless DC motor. In the present embodiment, the motor 2 is assumed to be a three-phase brushless DC motor having, for example, three-phase coils Lu, Lv, and Lw of U-phase, V-phase, and W-phase and a rotor (not shown). A position detection device 3 is provided around the motor 2.

[0037] The position detection device 3 is a device that generates a position detection signal corresponding to the rotation of the rotor (not shown) of the motor 2. The position detection device 3 is, for example, a HALL element. For example, three HALL elements corresponding to each phase (U-phase, V-phase, W-phase) of the motor 2 are arranged around the rotor of the motor 2 at substantially equal intervals (for example, at an interval of 120 degrees between adjacent ones) as the position detection device 3.

[0038] The three Hall elements each detect the magnetic poles of the rotor, generate and output a Hall signal whose voltage changes according to the rotation of the rotor. The Hall signals output from each Hall element are input as position detection signals Sr to a control circuit 11 described later. The control circuit 11 can detect the rotation state of the motor 2 by obtaining information such as the rotation position and rotation speed information (such as FG signal) of the motor 2 using the Hall signal, and control the driving of the motor 2.

[0039] Note that as the position detection device 3, instead of such a Hall element, for example, an encoder or a resolver may be provided, and their detection signals may be input as position detection signals Sr to the control circuit 11. Further, when the control circuit 11 performs drive control of the motor 2 in a sensorless position method, the position detection device 3 may not be provided.

[0040] The motor drive control device 1 is a device that controls the driving of the motor 2. The motor drive control device 1 has a function of controlling the rotation of the rotor of the motor 2 and, in addition, a function of suppressing an increase in voltage by regenerating the back electromotive force generated in the coils Lu, Lv, and Lw of the motor 2 during deceleration of the rotor.

[0041] Specifically, the motor drive control device 1 has, for example, a control circuit 11, a motor drive circuit 12, a voltage detection circuit 16, and a regeneration circuit 17. Note that the motor drive control device 1 may have other circuits etc. other than the circuits described above.

[0042] The motor drive circuit 12 is a circuit that drives the motor 2 based on a drive control signal Sd for controlling the driving of the motor 2.

[0043] The drive control signal Sd is, for example, a PWM (Pulse Width Modulation) signal. Specifically, the drive control signal Sd includes six types of PWM signals corresponding to the drive transistors Q1 to Q6 switch elements of an inverter circuit 14 described later.

[0044] The motor drive circuit 12 operates by being supplied with a power supply voltage Vdc through a power supply line Lp connected to an external power supply. The motor drive circuit 12 includes, for example, a pre-drive circuit 13 and an inverter circuit 14.

[0045] The pre-drive circuit 13 is a circuit that generates a drive signal for driving the inverter circuit 14 based on the drive control signal Sd output from the control circuit 11. For example, the pre-drive circuit 13 generates six types of drive signals Vuu, Vul, Vvu, Vvl, Vwu, Vwl having sufficient power to drive the control electrodes (gate electrodes) of the respective drive transistors Q1 to Q6 of the inverter circuit 14, which respectively correspond to six types of PWM signals as the drive control signal Sd.

[0046] The inverter circuit 14 is connected between a ground line Lg connected to the ground potential (=0V) and the power supply line Lp, and is a circuit that drives the coils Lu, Lv, Lw of the motor 2 as a load based on the input drive signal. Specifically, as shown in FIG. 1, the inverter circuit 14 has switching legs SWu, SWv, SWw each including two drive transistors connected in series. The corresponding drive signals Vuu, Vul, Vvu, Vvl, Vwu, Vwl (six types of PWM signals) are respectively input to the gate electrodes of the two drive transistors ((Q1, Q2), (Q3, Q4), (Q5, Q6)) constituting each switching leg SWu, SWv, SWw, so that each drive transistor Q1 to Q6 performs an on / off operation (switching operation). As a result, power is supplied from the power supply line Lp to the coils Lu, Lv, Lw of each phase of the motor 2, and the motor 2 rotates.

[0047] An inverter circuit 14 is connected to a current detection circuit 15. The current detection circuit 15 is a circuit for detecting the drive current of the motor 2. The current detection circuit 15 includes, for example, a resistor Rs. The resistor Rs is connected in series with the inverter circuit 14, for example, between a power line Lp and a ground line Lg. The current detection circuit 15 converts the current flowing through the coils Lu, Lv, Lw of the motor 2 into a voltage by the resistor Rs and inputs it to the control circuit 11 as a current detection signal Si.

[0048] Note that when the control circuit 11 performs drive control of the motor 2 without using the detected value of the drive current of the motor 2, the current detection circuit 15 may not be provided. Also, when each transistor Q1 to Q6 of the inverter circuit 14 can be driven without power shortage by the drive control signal Sd, the pre-drive circuit 13 may not be provided.

[0049] A voltage detection circuit 16 is a circuit for detecting the voltage of the power line Lp. Specifically, the voltage detection circuit 16 detects the voltage Vpg between the power line Lp and the ground line Lg and outputs a voltage detection signal Sp corresponding to the detected voltage. For example, the voltage detection circuit 16 is a voltage dividing circuit having a plurality of resistors connected in series between the power line Lp and the ground line Lg, and outputs the voltage obtained by dividing the voltage Vpg between the power line Lp and the ground line Lg as the voltage detection signal Sp.

[0050] Note that the voltage detection circuit 16 may have an analog / digital conversion circuit that converts the divided voltage into a digital signal and outputs it as the voltage detection signal Sp, or an analog / digital conversion circuit may be provided in the control circuit 11 to convert the voltage detection signal Sp as an analog signal into a digital signal by the analog / digital conversion circuit in the control circuit 11.

[0051] The regeneration circuit 17 is a circuit for absorbing the back electromotive force generated in the coils Lu, Lv, and Lw of the motor 2 when the rotor of the motor 2 is decelerated or the like. Specifically, the regeneration circuit 17 has a resistor (R) 18 and a switching element SWr connected in series between a power supply line Lp, which is a first line to which the back electromotive force is supplied from the motor 2, and a ground line Lg, which is a second line having a lower potential than the power supply line Lp. The regeneration circuit 17 further has a pre-drive circuit 19.

[0052] The switching element SWr is, for example, a transistor. As the switching element SWr, for example, a power transistor such as a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor) can be used. In the present embodiment, the case where the switching element SWr is a MOSFET will be taken as an example for explanation.

[0053] As shown in FIG. 1, for example, the source electrode of the MOSFET as the switching element SWr is connected to the ground line Lg, the gate electrode of the MOSFET is connected to the output terminal of the pre-drive circuit 19, and the drain electrode of the MOSFET is connected to one end of the resistor 18. As will be described later, the on / off of the switching element SWr is controlled by a drive signal input to the gate electrode of the switching element SWr from the pre-drive circuit 19 based on the control signal Sx output from the control circuit 11.

[0054] The resistor 18 is a component for limiting the current flowing when the switching element SWr is turned on and consuming the back electromotive force generated from the coils Lu, Lv, and Lw. As the resistor 18, for example, a resistor having an appropriate rated power corresponding to the magnitude of the power to be consumed by the resistor 18 may be selected.

[0055] The pre-drive circuit 19 is a circuit that generates a drive signal for driving the switching element SWr based on the control signal Sx output from the control circuit 11. For example, the pre-drive circuit 19 generates a drive signal having sufficient power to drive the gate electrode of the switching element SWr based on a PWM signal as the control signal Sx described later, and supplies it to the gate electrode of the switching element SWr.

[0056] Note that when the switching element SWr can be driven without power shortage by the control signal Sx, the pre-drive circuit 19 may not be provided. Further, the regeneration circuit 17 may have other components in addition to the resistor 18 and the switching element SWr described above.

[0057] The control circuit 11 is a circuit that comprehensively controls the operation of the motor drive control device 1. The control circuit 11 is, for example, a program processing device having a configuration in which a processor such as a CPU, various storage devices such as RAM, ROM, and flash memory, and peripheral circuits such as a counter (timer), A / D conversion circuit, D / A conversion circuit, clock generation circuit, and input / output interface circuit are connected to each other via a bus or dedicated lines. Specifically, the control circuit 11 is, for example, a microcontroller (MCU: Micro Controller Unit).

[0058] Note that the control circuit 11 and the motor drive circuit 12 may be packaged as one semiconductor integrated circuit device (IC: Integrated Circuit), or the control circuit 11 and the motor drive circuit 12 may be packaged as individual integrated circuit devices.

[0059] The control circuit 11 generates a drive control signal Sd as a function of controlling the rotation of the rotor of the motor 2. For example, a drive command signal Sc output from a host device (not shown), a position detection signal Sr output from the position detection device 3, and a current detection signal Si output from the current detection circuit 15 are input to the control circuit 11.

[0060] The drive command signal Sc is a signal that includes a command related to the drive of the motor 2. The drive command signal Sc includes, for example, a command indicating the target rotational speed (target number of revolutions) of the motor 2. Note that the drive command signal Sc may be various forms of signals such as a PFM signal having a frequency corresponding to the target rotational speed, a PWM signal having a duty ratio corresponding to the target rotational speed, a torque command signal indicating the target value of the torque of the motor 2, etc. Note that in addition to the above-described signals, a temperature detection signal or the like may be input to the control circuit 11 from a temperature sensor.

[0061] Based on the input drive command signal Sc, position detection signal Sr, and current detection signal Si, the control circuit 11 performs known arithmetic processing and the like to generate a drive control signal Sd so that the motor 2 operates in the operating state specified by the drive command signal Sc, and supplies it to the motor drive circuit 12.

[0062] Also, as a function of suppressing an increase in voltage due to the regeneration of the back electromotive force from the coils Lu, Lv, Lw of the motor 2, the control circuit 11 controls the on / off of the switching element Swr so that the voltage Vpg between the power supply line Lp and the ground line Lg does not exceed the threshold value Vth based on the voltage detection signal Sp. For example, the control circuit 11 generates a PWM signal so that the voltage Vpg matches the threshold value Vth, and outputs it as the control signal Sx to control the on / off of the switching element Swr.

[0063] Here, the threshold value Vth is a voltage value that serves as a reference for the activation of the regeneration circuit 17, that is, the execution and stop of the switching of the switching element Swr.

[0064] In this embodiment, the control circuit 11 further has a function of dynamically changing the threshold value Vth. That is, the control circuit 11 increases the threshold value Vth in response to an increase in the temperature of the resistor 18. Specifically, when the voltage Vpg exceeds the threshold value Vth and this state continues for a predetermined time (reference time) Tth while the threshold value Vth is set to the lower limit value VL (an example of the first value), the control circuit 11 increases the threshold value Vth from the lower limit value VL. For example, the control circuit 11 increases the threshold value Vth from the lower limit value VL to the upper limit value VH (an example of the second value) that is greater than the lower limit value VL. When increasing the threshold value Vth, the control circuit 11 changes the threshold value Vth linearly (continuously).

[0065] Also, when the voltage Vpg between the power supply line Lp and the ground line Lg drops below the lower limit value VL while the threshold value Vth is set to a value greater than the lower limit value VL, the control circuit 11 decreases the threshold value Vth to the lower limit value VL. When decreasing the threshold value Vth, the control circuit 11 changes the threshold value Vth linearly (continuously).

[0066] Hereinafter, a configuration example of the control circuit 11 for the control circuit 11 to realize the above-described functions will be described in detail.

[0067] FIG. 2 is a diagram showing an example of the functional block configuration of the control circuit 11 according to Embodiment 1.

[0068] As shown in FIG. 2, the control circuit 11 includes a voltage value acquisition unit 21, a threshold value setting unit 22, a control signal generation unit 23, a storage unit 24, and a drive control signal generation unit 25 as functional blocks for realizing the above-described functions. These functional blocks are realized, for example, in a program processing device as the control circuit 11 when the processor executes various arithmetic processes according to a program stored in the memory and controls peripheral circuits such as a counter and an A / D conversion circuit. Note that some or all of the above functional blocks may be realized by a dedicated hardware logic circuit.

[0069] The drive control signal generation unit 25 is a functional unit that generates a drive control signal Sd. The drive control signal generation unit 25 generates the drive control signal Sd based on the drive command signal Sc, the position detection signal Sr, the current detection signal Si, etc. input to the control circuit 11, so that the motor 2 is in the operating state specified by the drive command signal Sc. For example, the drive control signal generation unit 25 calculates the actual rotational speed of the motor 2 based on the position detection signal Sr, and generates the above-described six types of PWM signals so that the calculated actual rotational speed matches the target rotational speed specified by the drive command signal Sc, and outputs them as the drive control signal Sd. Here, as an arithmetic method for generating the drive control signal Sd by the drive control signal generation unit 25, for example, a known arithmetic method such as PID control or vector control can be adopted.

[0070] The storage unit 24 is a functional unit that stores various parameters for generating the drive control signal Sd and various parameters for controlling the regenerative circuit 17. For example, FIG. 2 typically shows a case where information on the lower limit value VL, the upper limit value VH, and the reference time Tth is stored in the storage unit 24 as parameters for controlling the regenerative circuit 17.

[0071] The voltage value acquisition unit 21 is a functional unit that acquires the value of the voltage Vpg between the power supply line Lp and the ground line Lg. The voltage value acquisition unit 21 calculates and outputs the value of the voltage Vpg between the power supply line Lp and the ground line Lg based on the voltage detection signal Sp. For example, when the voltage detection signal Sp indicates the voltage obtained by dividing the voltage Vpg, the value of the voltage Vpg is calculated from the divided voltage.

[0072] The threshold setting unit 22 is a functional unit that sets a threshold Vth. For example, after the motor drive control device 1 (control circuit 11) is started, the value of the lower limit value VL is read from the storage unit 24, and the lower limit value VL is set as the threshold Vth (Vth = VL). When the threshold Vth is set to the lower limit value VL, the threshold setting unit 22 compares the value of the voltage Vpg calculated by the voltage value acquisition unit 21 with the threshold Vth.

[0073] When the voltage Vpg becomes greater than the threshold value Vth, the threshold setting unit 22 starts measuring time. For example, the threshold setting unit 22 has a counter (CNTR) 220. When the threshold setting unit 22 detects that the voltage Vpg has become greater than the threshold value Vth, it activates the counter 220 to start counting the time T. On the other hand, when the threshold setting unit 22 detects that the voltage Vpg has become less than or equal to the threshold value Vth, it resets the counter (CNTR) 220 to stop measuring the time T.

[0074] When the time T measured by the counter 220 reaches the reference time (an example of a predetermined time) Tth stored in the storage unit 24 (T≧Tth), the threshold setting unit 22 increases the threshold value Vth. When increasing the threshold value Vth, the threshold setting unit 22 changes the threshold value Vth linearly (continuously). For example, the threshold setting unit 22 increases the threshold value Vth by a unit amount Δv1 every unit time Δt1. Then, when the threshold value Vth reaches the upper limit value VH stored in the storage unit 24, the increase of the threshold value Vth is stopped, and the threshold value Vth is fixed at the upper limit value VH (Vth = VH).

[0075] When the voltage Vpg drops below the lower limit value VL while the threshold value Vth is set to a value greater than the lower limit value VL, the threshold setting unit 22 decreases the threshold value Vth to the lower limit value VL. When decreasing the threshold value Vth, the threshold setting unit 22 changes the threshold value Vth linearly (continuously). For example, the threshold setting unit 22 decreases the threshold value Vth by a unit amount Δv2 every unit time Δt2. Then, when the threshold value Vth reaches the lower limit value VL, the decrease of the threshold value Vth is stopped, and the threshold value Vth is fixed at the lower limit value VL (Vth = VL).

[0076] Note that the rate of change Δv1 / Δt1 of the threshold value Vth when increasing the threshold value Vth and the rate of change Δv2 / Δt2 of the threshold value Vth when decreasing the threshold value Vth may be the same or different. For example, the rate of change Δv2 / Δt2 of the threshold value Vth when decreasing the threshold value Vth may be made larger than the rate of change Δv1 / Δt1 of the threshold value Vth when increasing the threshold value Vth, and the threshold value Vth may be quickly returned to the lower limit value VL (initial value).

[0077] The control signal generation unit 23 is a functional unit that generates a control signal Sx for controlling the on / off of the switching element Swr of the regeneration circuit 17.

[0078] When the value of the voltage Vpg acquired by the voltage value acquisition unit 21 is smaller than the threshold value Vth, the control signal generation unit 23 stops the regeneration circuit 17. That is, the control signal generation unit 23 outputs a control signal Sx for turning off the switching element Swr.

[0079] On the other hand, when the voltage Vpg becomes equal to or greater than the threshold value Vth, the control signal generation unit 23 activates the regeneration circuit 17. Specifically, the control signal generation unit 23 generates the control signal Sx so that the voltage Vpg matches the threshold value Vth. For example, the control signal generation unit 23 generates a PWM signal by PI control so that the error between the voltage Vpg and the threshold value Vth becomes small, and outputs it as the control signal Sx. That is, the control signal generation unit 23 generates a PWM signal as the control signal Sx so that the duty ratio increases as the voltage Vpg is larger than the threshold value Vth, and the voltage Vpg becomes less than the threshold value Vth.

[0080] Here, the maximum duty ratio of the PWM signal may be 100% or may be set to a value lower than 100%.

[0081] Next, the flow of the control method of the regeneration circuit 17 in the motor drive control device 1 will be described.

[0082] Figs. 3A and 3B are flowcharts showing the flow of the control method of the regeneration circuit 17 according to Embodiment 1.

[0083] Fig. 4 is a timing chart showing an example of changes in the voltage Vpg between the power line Lp and the ground line Lg and the threshold value Vth when the motor 2 is driven in the motor unit 100 according to Embodiment 1.

[0084] In Fig. 4, the horizontal axis represents time, and the vertical axis represents voltage. Reference numeral 401 represents the change of the voltage Vpg between the power line Lp and the ground line Lg with respect to time, and reference numeral 402 represents the change of the threshold value Vth with respect to time.

[0085] Here, as an example, consider the case where the power supply voltage Vdc = 12V, the lower limit value VL = 14V, the upper limit value VH = 30V, and the regeneration circuit 17 is controlled so that the voltage Vpg between the power line Lp and the ground line Lg does not exceed 35V.

[0086] For example, when the power supply voltage Vdc is applied and the motor drive control device 1 is activated, the threshold setting unit 22 of the control circuit 11 sets the threshold value Vth to the lower limit value VL by the method described above (step S11).

[0087] When the drive command signal Sc is input from the host device, the drive control signal generation unit 25 of the control circuit 11 generates the drive control signal Sd by the method described above and starts driving the motor 2 (step S12). As a result, the motor 2 rotates.

[0088] The control circuit 11 monitors the voltage Vpg and determines whether the voltage Vpg is greater than the threshold value Vth (step S13). When the voltage Vpg is smaller than the threshold value Vth (step S13: NO), the control circuit 11 continues to monitor the voltage Vpg. When the voltage Vpg is equal to or greater than the threshold value Vth (step S13: YES), the control circuit 11 activates the regeneration circuit 17 (step S14).

[0089] For example, as shown in FIG. 4, when deceleration of the motor 2 is instructed by the drive command signal Sc at time t0, the drive control signal generation unit 25 generates a drive control signal Sd so that the motor 2 decelerates. As a result, a back electromotive force is generated in the coils Lu, Lv, and Lw of the motor 2, and when supplied to the power supply line Lp, as shown in FIG. 4, the voltage of the power supply line Lp, that is, the voltage Vpg between the power supply line Lp and the ground line Lg starts to rise from 12V. Then, when the voltage Vpg reaches 14V, which is the threshold value Vth (= VL), at time t1, the control signal generation unit 23 of the control circuit 11 generates a control signal Sx by the method described above to activate the regeneration circuit 17.

[0090] When the regeneration circuit 17 is activated, the threshold setting unit 22 of the control circuit 11 starts measuring the time T by the method described above (step S15). The threshold setting unit 22 determines whether or not the measured time T has reached the reference time Tth (step S16). If the measured time T has not reached the reference time Tth (step S16: NO), the control circuit 11 continues to control the regeneration circuit 17 based on the voltage Vpg and measures the time T (steps S13 to S16). When the voltage Vpg drops below the threshold value Vth, the threshold setting unit 22 resets the measured value of the time T and continues to monitor the voltage Vpg.

[0091] On the other hand, when the measured time T reaches the reference time Tth (step S16: YES), the threshold setting unit 22 of the control circuit 11 raises the threshold value Vth by the method described above (step S17).

[0092] For example, as shown in FIG. 4, at time t1, the regeneration circuit 17 is activated and measurement of the time T starts. After time t1, the switching element Swr in the regeneration circuit 17 is controlled based on the control signal Sx as a PWM signal, and the rise of the voltage Vpg becomes gentle. Then, at time t2 when the measured time T reaches the reference time Tth, the threshold value Vth starts to rise.

[0093] After the start of the increase in the threshold value Vth in step S17, the threshold setting unit 22 of the control circuit 11 determines whether or not the threshold value Vth has reached the upper limit value VH (step S18). If the threshold value Vth has not reached the upper limit value VH (step S18: NO), the threshold setting unit 22 continues to increase the threshold value Vth.

[0094] On the other hand, when the threshold value Vth reaches the upper limit value VH (step S18: YES), the threshold setting unit 22 stops the increase in the threshold value Vth and fixes the threshold value Vth to the upper limit value VH (= 30 V) (step S19).

[0095] For example, as shown in FIG. 4, since the threshold value Vth increases at time t2, the difference between the threshold value Vth and the voltage Vpg becomes small. Therefore, the duty ratio of the control signal generation unit 23 becomes small, and the current flowing through the resistor 18 of the regenerative circuit 17 that suppresses the voltage increase also decreases. As a result, after time t2, the voltage Vpg also increases together with the threshold value Vth. Then, as shown in FIG. 4, at time t3 when the threshold value Vth reaches the upper limit value VH, the threshold value Vth is fixed at the upper limit value VH. Thereby, the control signal generation unit 23 generates the control signal Sx so that the voltage Vpg does not exceed the upper limit value VH (= 30 V) which is the threshold value Vth, and the increase in the voltage Vpg is suppressed.

[0096] After fixing the threshold value Vth to the upper limit value VH in step S19, the threshold setting unit 22 of the control circuit 11 determines whether or not the voltage Vpg has become equal to or lower than the lower limit value VL (step S20). If the voltage Vpg is greater than the lower limit value VL (step S20: NO), the threshold setting unit 22 continues to fix the threshold value Vth to the upper limit value VH. On the other hand, when the voltage Vpg becomes equal to or lower than the lower limit value VL (step S20: YES), the threshold setting unit 22 decreases the threshold value Vth (step S21).

[0097] For example, as shown in FIG. 4, when the threshold voltage Vth reaches the upper limit value VH at time t3, the voltage rise of Vpg is suppressed by the regenerative circuit 17. Thereafter, the deceleration of the motor 2 becomes gentle and the voltage Vpg decreases. When the voltage Vpg becomes smaller than the threshold voltage Vth, the control circuit 11 stops the regenerative circuit 17. That is, the control signal generation unit 23 generates a control signal Sx for turning off the switching element SWr. Thereafter, as shown in FIG. 4, the voltage Vpg further decreases, and at time t4 when the voltage Vpg reaches the lower limit value VL (= 14V), the threshold setting unit 22 decreases the threshold voltage Vth.

[0098] After the start of the decrease in the threshold voltage Vth in step S21, the threshold setting unit 22 of the control circuit 11 determines whether or not the threshold voltage Vth has reached the lower limit value VL (step S22). If the threshold voltage Vth has not reached the lower limit value VL (step S22: NO), the threshold setting unit 22 continues to decrease the threshold voltage Vth.

[0099] On the other hand, when the threshold voltage Vth reaches the lower limit value VL (step S22: YES), the threshold setting unit 22 stops the decrease in the threshold voltage Vth and fixes the threshold voltage Vth to the lower limit value VL (= 14V) (step S23).

[0100] For example, as shown in FIG. 4, after time t4, the threshold voltage Vth continues to decrease, and at time t5 when the threshold voltage Vth reaches the lower limit value VL, the threshold voltage Vth is fixed at the lower limit value VL. As a result, the threshold voltage Vth returns to the initial value set in step S11.

[0101] As described above, in the motor drive control device 1 according to the present embodiment, the control circuit 11 controls the on / off of the switching element SWr of the regenerative circuit 17 so that the voltage Vpg between the power supply line Lp and the ground line Lg does not exceed the threshold voltage Vth. The control circuit 11 increases the threshold voltage Vth in accordance with the increase in the temperature of the resistor 18.

[0102] For example, if the threshold value Vth is fixed at the upper limit value VH, in a situation where the back electromotive force from the coils Lu, Lv, and Lw of the motor 2 as the energy to increase the voltage Vpg is large, the fluctuation of the voltage Vpg becomes large, and it becomes difficult to control the motor 2. Therefore, considering the ease of controlling the motor 2, it is preferable that the fluctuation of the voltage Vpg is small. For example, it is desirable to fix the threshold value Vth at the lower limit value VL. However, when the threshold value Vth is fixed at the lower limit value VL, since the time during which current flows through the regenerative circuit 17 increases, the heat generation of the regenerative circuit 17 (resistor 18 and switching element SWr) increases.

[0103] On the other hand, according to the motor drive control device 1 according to the present embodiment, even when the back electromotive force is large and the voltage Vpg does not sufficiently decrease, the control circuit 11 increases the threshold value Vth in response to the increase in the temperature of the resistor 18. Therefore, compared with the case where the threshold value Vth is fixed at the lower limit value VL, the difference between the voltage Vpg and the threshold value Vth can be made smaller. As a result, it becomes difficult for the duty ratio of the PWM signal as the control signal Sx to reach the maximum value (for example, 100%), and the time during which the switching element SWr is continuously on can be shortened. Therefore, it is possible to suppress the heat generation of the regenerative circuit 17 (resistor 18 and switching element SWr).

[0104] Also, as in the prior study example by the inventor of the present application described above, when the switching element SWr is turned on continuously for a certain period and then turned off, the back electromotive force may not be sufficiently absorbed, and the voltage Vpg may increase. On the other hand, according to the motor drive control device 1 according to the present embodiment, since the switching element SWr performs switching even during the period when the threshold value Vth is increasing, the back electromotive force can be sufficiently absorbed in the regenerative circuit 17. As a result, a sudden increase in the voltage Vpg can be suppressed.

[0105] In this way, according to the motor drive control device 1, it is possible to effectively suppress the increase in the voltage Vpg while suppressing the heat generation in the regenerative circuit 17.

[0106] Also, in the motor drive control device 1, the control circuit 11 starts to increase the threshold value Vth after a predetermined time has elapsed. According to this, it becomes possible to easily estimate the state in which the temperature of the regeneration circuit 17 (resistor 18 and switching element SWr) is rising without separately providing a temperature sensor.

[0107] Also, in the motor drive control device 1, the control circuit 11 raises the threshold value Vth from the lower limit value VL to the upper limit value VH. According to this, the regeneration circuit 17 can be controlled so that the voltage Vpg does not exceed the upper limit value VH.

[0108] Here, it is preferable to set the upper limit value VH to a value smaller than the limit value that the voltage Vpg must not exceed. For example, as in the above example, when the limit value that the voltage Vpg must not exceed is 35V, the upper limit value VH is set to 30V, which is a value lower than 35V. According to this, even when the voltage Vpg exceeds the upper limit value VH (30V) in a state where the threshold value Vth is set to the upper limit value VH (30V), the risk that the voltage Vpg exceeds the limit value (35V) can be reduced.

[0109] Also, in the motor drive control device 1, when the control circuit 11 raises the threshold value Vth, it linearly changes the threshold value Vth. According to this, since the voltage Vpg can be changed gently, it becomes possible to prevent the operation of the motor 2 from becoming unstable.

[0110] Also, in the motor drive control device 1, when the voltage Vpg drops below the lower limit value VL while the threshold value Vth is set to a value greater than the lower limit value VL, the control circuit 11 lowers the threshold value Vth to the lower limit value VL. According to this, since the increased threshold value Vth automatically returns to the initial value, which is the lower limit value VL, it becomes possible to appropriately drive the regeneration circuit 17 according to the magnitude of the voltage Vpg.

[0111] Also, in the motor drive control device 1, the control circuit 11 generates a PWM signal so that the voltage Vpg matches the threshold value Vth, and outputs it as the control signal Sx. According to this, since the on / off of the switching element SWr is controlled by the PWM signal, it becomes possible to make the change in the voltage Vpg smoother.

[0112] ≪Embodiment 2≫ FIG. 5 is a diagram showing the configuration of a motor unit 100A including a motor drive control device 1A according to Embodiment 2.

[0113] The motor drive control device 1A shown in FIG. 5 is different from the motor drive control device 1 according to Embodiment 1 in that the threshold value Vth is dynamically changed based on the measured temperature value by the temperature sensor, and is the same as the motor drive control device 1 in other respects.

[0114] As shown in FIG. 5, the motor drive control device 1A further includes a temperature sensor 20. The temperature sensor 20 is a sensor capable of detecting temperature. As the temperature sensor 20, for example, a device including a thermistor or a thermocouple can be applied. The temperature sensor 20 outputs a detection signal Stmp according to the magnitude of the detected temperature.

[0115] The temperature sensor 20 is preferably arranged so as to be able to measure the temperature of the resistor 18 in the regeneration circuit 17A. For example, the temperature sensor 20 is preferably arranged adjacent to the resistor 18 in the regeneration circuit 17A. Here, adjacent means that the distance between the resistor 18 and the temperature sensor 20 is, for example, 10 mm or less.

[0116] More preferably, the temperature sensor 20 is arranged such that at least a part of the temperature sensor 20 contacts at least a part of the resistor 18. Note that the temperature sensor 20 may be provided as an element of the regeneration circuit 17A, or may be provided as an element of the electronic circuit 30A (motor drive control device 1A).

[0117] Similar to the control circuit 11 according to the first embodiment, the control circuit 11A has a function of dynamically changing the threshold value Vth. That is, the control circuit 11A has a function of increasing the threshold value Vth in response to an increase in the temperature of the resistor 18. Specifically, when the measured value Tmp of the temperature detected by the temperature sensor 20 exceeds a predetermined temperature reference value Tmpth1, the control circuit 11 increases the threshold value Vth from the lower limit value VL (the first value). For example, the control circuit 11A increases the threshold value Vth from the lower limit value VL to an upper limit value VH (an example of the second value) that is greater than the lower limit value VL. When increasing the threshold value Vth, the control circuit 11A, for example, linearly (continuously) changes the threshold value Vth.

[0118] FIG. 6 is a diagram showing an example of the functional block configuration of the control circuit 11A according to the second embodiment.

[0119] As shown in FIG. 6, the control circuit 11A includes a voltage value acquisition unit 21, a threshold value setting unit 22A, a control signal generation unit 23, a storage unit 24A, a drive control signal generation unit 25, and a temperature acquisition unit 26 as functional blocks for realizing the above-described functions. Similar to the functional blocks of the control circuit 11, these functional blocks are realized, for example, in a program processing apparatus as the control circuit 11A when a processor executes various arithmetic processes according to a program stored in a memory and controls peripheral circuits such as a counter and an A / D conversion circuit. Note that some or all of the above functional blocks may be realized by a dedicated hardware logic circuit.

[0120] The temperature acquisition unit 26 is a functional unit that acquires the measured value Tmp of the temperature based on the detection signal Stmp of the temperature output from the temperature sensor 20. The temperature acquisition unit 26 includes, for example, an A / D conversion circuit. For example, the temperature acquisition unit 26 converts the detection signal Stmp (analog signal) of the temperature output from the temperature sensor 20 into a digital value, acquires it as the measured value Tmp of the temperature, and stores it in the storage unit 24A.

[0121] Similar to the storage unit 24 according to the first embodiment, the storage unit 24A stores various parameters for generating the drive control signal Sd and various parameters for controlling the regeneration circuit 17A. For example, the storage unit 24A stores, as parameters for controlling the regeneration circuit 17A, the lower limit value VL, the upper limit value VH, the measured temperature value Tmp, and information such as the temperature reference values Tmpth1 and Tmpth2.

[0122] The threshold setting unit 22A is a functional unit that sets the threshold value Vth. For example, after the motor drive control device 1A (control circuit 11A) is started, the value of the lower limit value VL is read from the storage unit 24A, and the lower limit value VL is set as the threshold value Vth (Vth = VL). The threshold setting unit 22A compares the measured temperature value Tmp measured by the temperature acquisition unit 26 with the temperature reference value Tmpth1.

[0123] When the measured temperature value Tmp of the temperature is lower than the temperature reference value Tmpth1 (Tmp < Tmpth1), the threshold setting unit 22A continues to set the threshold value Vth to the lower limit value VL. On the other hand, for example, when the measured temperature value Tmp of the temperature is equal to or higher than the temperature reference value Tmpth1 (Tmp ≧ Tmpth1), the threshold setting unit 22A increases the threshold value Vth. When increasing the threshold value Vth, the threshold setting unit 22A changes the threshold value Vth linearly (continuously). For example, the threshold setting unit 22A increases the threshold value Vth by a unit amount Δv1 every unit time Δt1. Then, when the threshold value Vth reaches the upper limit value VH stored in the storage unit 24A, the increase of the threshold value Vth is stopped, and the threshold value Vth is fixed to the upper limit value VH (Vth = VH).

[0124] When the measured temperature value Tmp drops below the temperature reference value Tmpth2 while the threshold value Vth is set to a value greater than the lower limit value VL, and when the voltage Vpg becomes less than or equal to the lower limit value VL, the threshold setting unit 22A decreases the threshold value Vth to the lower limit value VL. When decreasing the threshold value Vth, the threshold setting unit 22A changes the threshold value Vth linearly (continuously). For example, the threshold setting unit 22A decreases the threshold value Vth by a unit amount Δv2 every unit time Δt2. When the threshold value Vth reaches the lower limit value VL, the decrease of the threshold value Vth is stopped, and the threshold value Vth is fixed at the lower limit value VL (Vth = VL). Here, the temperature reference value Tmpth1 and the temperature reference value Tmpth2 may be the same value (Tmpth1 = Tmpth2), or the temperature reference value Tmpth2 may be set to a value lower than the temperature reference value Tmpth1 to give the threshold value Vth control hysteresis characteristics (Tmpth1 > Tmpth2).

[0125] Similar to Embodiment 1, the rate of change Δv1 / Δt1 of the threshold value Vth when increasing the threshold value Vth and the rate of change Δv2 / Δt2 of the threshold value Vth when decreasing the threshold value Vth may be the same or different. For example, the rate of change Δv2 / Δt2 of the threshold value Vth when decreasing the threshold value Vth may be made larger than the rate of change Δv1 / Δt1 of the threshold value Vth when increasing the threshold value Vth, so that the threshold value Vth can be quickly returned to the lower limit value VL (initial value).

[0126] Note that the voltage value acquisition unit 21, the control signal generation unit 23, and the drive control signal generation unit 25 operate in the same manner as in Embodiment 1.

[0127] Next, the flow of the control method of the regeneration circuit 17A in the motor drive control device 1A according to Embodiment 2 will be described.

[0128] FIGS. 7A and 7B are flowcharts showing the flow of the control method of the regeneration circuit 17A according to Embodiment 2.

[0129] For example, when the power supply voltage Vdc is applied and the motor drive control device 1A is started, the threshold setting unit 22A of the control circuit 11A sets the threshold Vth to the lower limit value VL by the above-described method (step S31).

[0130] When a drive command signal Sc is input from the host device, the drive control signal generation unit 25 of the control circuit 11A generates a drive control signal Sd by the above-described method and starts driving the motor 2 (step S32). As a result, the motor 2 rotates. At this time, the control circuit 11A also starts controlling the regeneration circuit 17A based on the comparison result between the voltage Vpg and the threshold Vth.

[0131] The control circuit 11A measures the temperature (step S33). Specifically, as described above, the temperature acquisition unit 26 of the control circuit 11A acquires the measured temperature value Tmp based on the temperature detection signal Stmp output from the temperature sensor 20.

[0132] Next, the threshold setting unit 22A of the control circuit 11A determines whether or not the measured temperature value Tmp is equal to or higher than the temperature reference value Tmpth1 (step S34). When the measured temperature value Tmp is lower than the temperature reference value Tmpth1 (step S34: NO), the threshold setting unit 22A continues to monitor the measured temperature value Tmp. When the measured temperature value Tmp is equal to or higher than the temperature reference value Tmpth1 (step S34: YES), the threshold setting unit 22A increases the threshold Vth by the above-described method (step S35).

[0133] After starting to increase the threshold Vth in step S35, the threshold setting unit 22A determines whether or not the threshold Vth has reached the upper limit value VH (step S36). When the threshold Vth has not reached the upper limit value VH (step S36: NO), the threshold setting unit 22A continues to increase the threshold Vth.

[0134] On the other hand, when the threshold Vth reaches the upper limit value VH (step S36: YES), the threshold setting unit 22A stops increasing the threshold Vth and fixes the threshold Vth to the upper limit value VH (= 30V) (step S37).

[0135] After fixing the threshold value Vth to the upper limit value VH in step S37, the threshold setting unit 22A determines whether the measured temperature value Tmp is lower than the temperature reference value Tmpth2 (step S38). When the measured temperature value Tmp of the temperature is equal to or higher than the temperature reference value Tmpth2 (step S38: NO), the threshold setting unit 22A continues to fix the threshold value Vth to the upper limit value VH. On the other hand, when the measured temperature value Tmp of the temperature becomes lower than the temperature reference value Tmpth2 (step S38: YES), the threshold setting unit 22A decreases the threshold value Vth by the method described above (step S38).

[0136] After the start of the decrease of the threshold value Vth in step S38, the threshold setting unit 22A determines whether the threshold value Vth has reached the lower limit value VL (step S40). When the threshold value Vth has not reached the lower limit value VL (step S40: NO), the threshold setting unit 22A continues to decrease the threshold value Vth.

[0137] On the other hand, when the threshold value Vth reaches the lower limit value VL (step S40: YES), the threshold setting unit 22A stops the decrease of the threshold value Vth and fixes the threshold value Vth to the lower limit value VL (= 14V) (step S41). As a result, the threshold value Vth returns to the initial value set in step S31.

[0138] FIG. 8 is a timing chart showing an example of changes in the voltage Vpg between the power supply line Lp and the ground line Lg and the threshold value Vth during the drive of the motor 2 in the motor unit 100A according to the second embodiment.

[0139] In FIG. 8, the horizontal axis represents the temperature around the resistor 18, and the vertical axis represents the voltage. Reference numeral 801 represents the change in the voltage Vpg between the power supply line Lp and the ground line Lg with respect to the temperature, and reference numeral 802 represents the change in the threshold value Vth with respect to the temperature.

[0140] Here, as an example, consider a case where the power supply voltage Vdc = 12V, the lower limit value VL = 14V, the upper limit value VH = 30V, the temperature reference value Tmpth1 = 80 degrees Celsius (°C), and the regeneration circuit 17A is controlled so that the voltage Vpg between the power supply line Lp and the ground line Lg does not exceed 35V.

[0141] As shown in FIG. 8, when the temperature is 25 degrees, assume that the back electromotive force of the motor 2 causes the voltage Vpg to rise and exceed the threshold value Vth (lower limit value VL). At this time, the control circuit 11A generates a PWM signal as the control signal Sx by the method described above and controls the regeneration circuit 17A. At this time, since the voltage Vpg exceeds the threshold value Vth (lower limit value VL), the control circuit 11A increases the duty ratio of the control signal Sx. As a result, the rise of the voltage Vpg becomes gentle, but the average current flowing through the resistor 18 increases, so the temperature of the resistor 18 begins to rise. When the temperature reaches 80 degrees, which is the temperature reference value Tmpth1, the control circuit 11A increases the threshold value Vth. As a result, the difference between the voltage Vpg and the threshold value Vth becomes smaller, so the duty ratio of the control signal Sx decreases, and the average current flowing through the resistor 18 is suppressed. Thereby, it is possible to suppress the rise of the voltage Vpg while suppressing the rise of the temperature of the resistor 18. After that, when the threshold value Vth reaches the upper limit value VH, the control circuit 11A fixes the threshold value Vth at the upper limit value VH.

[0142] As described above, in the motor drive control device 1A according to the second embodiment, when the measured value Tmp of the temperature detected by the temperature sensor 20 exceeds a predetermined temperature reference value Tmpth1, the control circuit 11A raises the threshold value Vth from the lower limit value VL.

[0143] According to this, even when the back electromotive force is large and the voltage Vpg does not sufficiently decrease, the motor drive control device 1A detects an increase in the temperature of the resistor 18 in the regeneration circuit 17A by the temperature sensor 20 and increases the threshold value Vth. Therefore, compared to the case where the threshold value Vth is fixed to the lower limit value VL, the difference between the voltage Vpg and the threshold value Vth can be reduced. As a result, similar to the motor drive control device 1 according to the first embodiment, it becomes difficult for the duty ratio of the PWM signal as the control signal Sx to reach the maximum value (for example, 100%), and the time during which the switching element SWr is continuously on can be shortened. Therefore, it is possible to suppress the heat generation of the regeneration circuit 17A (resistor 18 and switching element SWr).

[0144] Also, by providing the temperature sensor 20, it becomes possible to accurately detect an increase in the temperature of the resistor 18. Further, by arranging the temperature sensor 20 adjacent to the resistor 18, the threshold value Vth can be quickly changed according to the increase in the temperature of the resistor 18, so that it is possible to surely suppress the heat generation of the regeneration circuit 17A. Furthermore, by bringing the temperature sensor 20 into contact with the resistor 18, the increase in the temperature of the resistor 18 can be detected more accurately and more quickly, and the threshold value Vth can be changed. Therefore, it is possible to more surely suppress the heat generation of the regeneration circuit 17A.

[0145] Thus, according to the motor drive control device 1A according to the second embodiment, similar to the motor drive control device 1 according to the first embodiment, it is possible to effectively suppress an increase in the voltage Vpg while suppressing heat generation in the regeneration circuit 17A.

[0146] ≪Expansion of the Embodiment≫ As described above, the invention made by the present inventor has been specifically described based on the embodiments. However, needless to say, the present invention is not limited thereto, and various modifications can be made without departing from the gist thereof.

[0147] For example, in the above embodiment, the type of the motor 2 is not particularly limited. For example, the motor 2 is not limited to a brushless DC motor, and may be a stepping motor.

[0148] Also, in the above embodiment, the case where the control circuit 11 that controls the drive of the motor 2 controls the drives of the regeneration circuits 17, 17A has been illustrated, but it is not limited thereto. For example, a control circuit different from the control circuits 11, 11A (for example, a microcomputer or a dedicated hardware logic circuit, etc.) may be provided separately, and that control circuit may control the drives of the regeneration circuits 17, 17A by the same method as the control circuit 11. In this case, the above control circuit may have at least a voltage value acquisition unit 21, threshold value setting units 22, 22A, a control signal generation unit 23, and storage units 24, 24A (and a temperature acquisition unit 26) as functional blocks.

[0149] Also, in the above embodiment, the case where the regeneration circuits 17, 17A, the voltage detection circuit 16, and the control circuits 11, 11A that control the drives of the motor drive circuit 12 and the regeneration circuits 17, 17A are applied to the motor units 100, 100A has been illustrated, but it is not limited thereto. That is, it is also possible to apply the electronic circuits 30, 30A having the regeneration circuits 17, 17A, the voltage detection circuit 16, and a control circuit (a voltage value acquisition unit 21, threshold value setting units 22, 22A, a control signal generation unit 23, storage units 24, 24A (and a temperature acquisition unit 26)) that controls the drive of the regeneration circuits 17, 17A to other applications provided with coils.

[0150] Also, the flowcharts and timing charts in the above embodiment are examples and are not limited thereto. For example, other processes may be inserted between each step in the flowchart, or the processes may be parallelized.

Explanation of Reference Numerals

[0151] 1, 1A... Motor drive control device, 2... Motor, 3... Position detection device, 11, 11A... Control circuit, 12... Motor drive circuit, 13... Predrive circuit, 14... Inverter circuit, 15... Current detection circuit, 16... Voltage detection circuit, 17, 17A... Regeneration circuit, 18... Resistor, 19... Predrive circuit, 20... Temperature sensor, 21... Voltage value acquisition unit, 22, 22A... Threshold setting unit, 23... Control signal generation unit, 24, 24A... Memory unit, 25... Drive control signal generation unit, 26... Temperature acquisition unit, 220... Counter (CNTR), 100, 100A... Motor unit, 30, 30A... Electronic circuit, Lp... Power supply line (first line), Lg... Ground line (second line), Tth... Reference time, Tmp... Measured value of temperature, Tmpth1, Tmpth2... Temperature reference value, SWr... Switching element, Sp... Voltage detection signal, Sx... Control signal, Si... Current detection signal, Sc... Drive command signal, Sd... Drive control signal, Sr... Position detection signal, Stmp... Detection signal of temperature, VL... Lower limit value (first value), VH... Upper limit value (second value), Vth... Threshold value, Vdc... Power supply voltage, Vpg... Voltage between power supply line Lp and ground line Lg.

Claims

1. A motor drive circuit that drives a motor based on a drive control signal for controlling the drive of the motor, A regenerative circuit having a resistor and a switching element connected in series with each other between a first line to which a back electromotive force is supplied from the motor and a second line having a lower potential than the first line, A voltage detection circuit that detects the voltage between the first line and the second line and outputs a voltage detection signal corresponding to the detected voltage, A control circuit that generates the drive control signal and, based on the voltage detection signal, generates a control signal so that the voltage between the first line and the second line does not exceed a threshold value, and controls the on / off of the switching element based on the control signal, and The control circuit raises the threshold value in response to an increase in the temperature of the resistor A motor drive control device.

2. In the motor drive control device according to Claim 1, When the voltage between the first line and the second line exceeds the threshold value for a predetermined time while the threshold value is set to a first value, the control circuit raises the threshold value from the first value A motor drive control device.

3. In the motor drive control device according to Claim 2, When the voltage between the first line and the second line drops below the first value while the threshold value is set to a value greater than the first value, the control circuit lowers the threshold value to the first value A motor drive control device.

4. In the motor drive control device according to Claim 1, Further comprising a temperature sensor that detects temperature, When the measured value of the temperature detected by the temperature sensor exceeds a predetermined temperature reference value while the threshold value is set to a first value, the control circuit raises the threshold value from the first value A motor drive control device.

5. In the motor drive control device according to Claim 4, The temperature sensor is arranged adjacent to the resistor A motor drive control device.

6. In the motor drive control device according to Claim 5, At least a part of the temperature sensor is in contact with at least a part of the resistor A motor drive control device.

7. In the motor drive control device according to Claim 2 or 4, The control circuit raises the threshold value from the first value to a second value greater than the first value A motor drive control device.

8. In the motor drive control device according to Claim 2 or 4, When increasing the threshold value, the control circuit linearly changes the threshold value. Motor drive control device.

9. In the motor drive control device according to claim 3, When decreasing the threshold value, the control circuit linearly changes the threshold value. Motor drive control device.

10. In the motor drive control device according to claim 2 or 4, The control circuit generates a PWM signal so that the voltage between the first line and the second line matches the threshold value, and outputs it as the control signal. Motor drive control device.

11. A motor drive control device according to any one of claims 1 to 6, And the motor driven by the motor drive control device. Motor unit.

12. A regenerative circuit having a resistor and a switching element connected in series between a first line to which back electromotive force is supplied from a coil and a second line having a lower potential than the first line, A voltage detection circuit that detects the voltage between the first line and the second line and outputs a voltage detection signal corresponding to the detected voltage, A control circuit that controls the on / off of the switching element so that the voltage between the first line and the second line does not exceed a threshold value, The control circuit increases the threshold value in response to an increase in the temperature of the resistor. Electronic circuit.

13. In the electronic circuit according to claim 12, When the voltage between the first line and the second line exceeds the threshold value while the threshold value is set to a first value and this state continues for a predetermined time, the control circuit increases the threshold value from the first value. Electronic circuit.

14. In the electronic circuit according to claim 12, Further comprising a temperature sensor for detecting temperature, When the measured value of the temperature detected by the temperature sensor exceeds a predetermined temperature reference value while the threshold value is set to a first value, the control circuit increases the threshold value from the first value. Electronic circuit.

15. A first step of driving a motor based on a drive control signal for controlling the drive of the motor, A second step of detecting the voltage between a first line to which back electromotive force is supplied from the motor and a second line having a lower potential than the first line. In a regenerative circuit having a resistor and a switching element connected in series between the first line and the second line, a third step of controlling the on / off of the switching element so that the voltage detected in the second step does not exceed a threshold value; a fourth step of increasing the threshold value in response to an increase in the temperature of the resistor, Control method.

16. In the control method according to claim 15, The fourth step includes a step of increasing the threshold value from the first value when a state in which the voltage exceeds the threshold value continues for a predetermined time while the threshold value is set to the first value. Control method.

17. In the control method according to claim 15, The regenerative circuit includes a temperature sensor for detecting temperature, The fourth step includes a step of increasing the threshold value from the first value when a measured value of the temperature detected by the temperature sensor exceeds a predetermined temperature reference value while the threshold value is set to the first value. Control method.

18. A control method for a regenerative circuit having a resistor and a switching element connected in series between a first line supplied with back electromotive force from a coil and a second line having a lower potential than the first line, a first step of detecting a voltage between the first line and the second line; a second step of controlling the on / off of the switching element so that the voltage detected in the first step does not exceed a threshold value; a third step of increasing the threshold value in response to an increase in the temperature of the resistor, Control method.

19. In the control method according to claim 18, The third step includes a step of increasing the threshold value from the first value when a state in which the voltage exceeds the threshold value continues for a predetermined time while the threshold value is set to the first value. Control method.

20. In the control method according to claim 18, The regenerative circuit includes a temperature sensor for detecting temperature, The third step includes a step of increasing the threshold value from the first value when a measured value of the temperature detected by the temperature sensor exceeds a predetermined temperature reference value while the threshold value is set to the first value. Control method.

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