Motor drive control device and motor unit

Abstract

This reduces the ringing caused by the back electromotive force generated when the motor is driven. [Solution] The motor drive control device 1 is characterized by comprising: a control circuit 2 that has input terminals Pu, Pv, Pw for inputting back electromotive force generated in coils Lu, Lv, Lw in the motor 10, and generates a drive control signal Sd for controlling the drive of the motor 10 based on the detection result of the back electromotive force input to the input terminals Pu, Pv, Pw; a drive circuit 3 that drives the motor 10 based on the drive control signal Sd; and an RCD snubber circuit 7 that is connected between the coils Lu, Lv, Lw and their respective input terminals Pu, Pv, Pw, suppresses fluctuations in the voltage input to each input terminal Pu, Pv, Pw, and clamps the negative voltage input to each input terminal Pu, Pv, Pw.

Description

Technical Field

[0001] The present invention relates to a motor drive control device and a motor unit.

Background Art

[0002] As a motor drive control method, a sensorless method is known in which the position of the rotor is estimated by detecting the zero crossing of the back electromotive force (induced voltage) generated in the coil of the non-powered phase of the motor, and the motor is driven and controlled (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Generally, ringing occurs in the waveform of the back electromotive force when the motor is driven. In particular, when the rotational speed of the motor is high, when the load of the motor is large, and when the drive voltage of the motor is large, the ringing tends to increase. When large ringing occurs in the back electromotive force, a control circuit that controls the motor by the sensorless method may erroneously detect the ringing voltage superimposed on the waveform of the back electromotive force as the zero crossing of the back electromotive force, and it may not be possible to detect the accurate zero crossing of the back electromotive force, and there is a risk that the drive of the motor becomes unstable.

[0005] The present invention is for solving the above-described problems, and an object thereof is to reduce the ringing of the back electromotive force generated when the motor is driven.

Means for Solving the Problems

[0006] A motor drive control device according to a typical embodiment of the present invention is characterized by comprising: a motor having a stator and rotor including coils of multiple phases, each having an input terminal for inputting a back electromotive force generated in the coils, a control circuit that generates a drive control signal for controlling the driving of the motor based on the detection result of the back electromotive force input to the input terminals, a drive circuit that drives the motor based on the drive control signal, and an RCD snubber circuit connected between the coils and each of the input terminals, which suppresses fluctuations in the voltage input to each of the input terminals and clamps the negative voltages input to each of the input terminals. [Effects of the Invention]

[0007] According to one aspect of the present invention, it is possible to reduce the ringing of the back electromotive force generated when the motor is driven. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows the configuration of a motor unit equipped with a motor drive control device according to Embodiment 1. [Figure 2A] This figure shows an example of experimental results for voltage in a motor drive control device according to Embodiment 1. [Figure 2B] This figure shows an example of experimental results for voltage in a motor drive control device without an RCD snubber circuit, as a comparative example of the motor drive control device according to Embodiment 1. [Figure 3] This figure shows the configuration of a motor unit equipped with a motor drive control device according to Embodiment 2. [Figure 4] This figure shows the configuration of a motor unit equipped with a motor drive control device according to Embodiment 3. [Figure 5] This figure shows the configuration of a motor unit equipped with a motor drive control device according to Embodiment 4. [Modes for carrying out the invention]

[0009] 1. Overview of the Embodiment First, a general overview of a typical embodiment of the invention disclosed in this application will be provided. In the following description, as an example, reference numerals on the drawings corresponding to the components of the invention are indicated in parentheses.

[0010] [1] A motor drive control device (1) according to a typical embodiment of the present invention is a motor (10) having a stator and rotor including a plurality of phase coils (Lu, Lv, Lw), and each phase having input terminals (Pu, Pv, Pw) for inputting the back electromotive force generated in the coils, and a control circuit (2) that generates a drive control signal (Sd) for controlling the drive of the motor based on the detection result of the back electromotive force input to the input terminals, a drive circuit (3) that drives the motor based on the drive control signal, and an RCD snubber circuit (7, 7A, 7B, 7C) connected between the coils and each of the input terminals, which suppresses fluctuations in the voltage input to each of the input terminals and clamps the negative voltage input to each of the input terminals.

[0011] [2] In the motor drive control device (1) described in [1] above, the RCD snubber circuit (7) includes pairs of circuit elements (Sn1, Sn2, Sn3) which are connected in series with each other and are provided between the input terminals of each phase, and diodes (D1, D2, D3) provided corresponding to each pair of circuit elements, wherein the anode electrode side of the diode is connected to an intermediate node (N1, N2, N3) to which the resistor and capacitor of the corresponding pair of circuit elements are connected, and the cathode electrode side of the diode is connected to the input terminal to which one terminal of the corresponding pair of circuit elements is connected.

[0012] [3] In the motor drive control device (1A) described in [1] above, the RCD snubber circuit (7A) includes pairs of circuit elements (Sn1, Sn2, Sn3) which are connected in series with each other and are provided between the input terminals of each phase, and diodes (D1, D2, D3) which are provided corresponding to each pair of circuit elements, wherein the anode electrode side of the diode is connected to ground potential and the cathode electrode side of the diode is connected to an intermediate node in which the resistor and the capacitor in the corresponding pair of circuit elements are connected.

[0013] [4] In the motor drive control device (1B) described in [1] above, the RCD snubber circuit (7B) includes pairs of circuit elements (Sn1, Sn2, Sn3) that include a resistor (Rs) and a capacitor (Cs) connected in series with each other, provided corresponding to each input terminal of each phase, and diodes (D1, D2, D3) provided corresponding to each pair of circuit elements, wherein one terminal of the pair of circuit elements is connected to the input terminal corresponding to that pair of circuit elements, the other terminal of the pair of circuit elements is connected in common with the other terminal of another pair of circuit elements, the anode side of the diode is connected to an intermediate node (N1, N2, N3) in the pair of circuit elements corresponding to the diode to which the resistor and the capacitor are connected, and the cathode side of the diode is connected to the input terminal to which one terminal of the pair of circuit elements corresponding to the diode is connected.

[0014] [5] In the motor drive control device (1C) described in [1] above, the RCD snubber rotation The path (7C) includes circuit element pairs (Sn1, Sn2, Sn3) each provided corresponding to each of the input terminals of each phase and including a resistor (Rs) and a capacitor (Cs) connected in series to each other, and diodes (D1, D2, D3) provided corresponding to each of the circuit element pairs. One terminal of the circuit element pair is connected to the input terminal corresponding to the circuit element pair, the other terminal of the circuit element pair is commonly connected to the other terminal of the other circuit element pair, the anode electrode side of the diode is connected to the ground potential (GND), and the cathode electrode side of the diode may be connected to an intermediate node (N1, N2, N3) where the resistor and the capacitor in the circuit element pair corresponding to the diode are connected.

[0015] 〔6〕The motor units (20, 20A, 20B, 20C) according to the typical embodiments of the present invention include the motor drive control device (1, 1A, 1B, 1C) described in any one of the above 〔1〕 to 〔5〕, and the motor (10) driven by the motor drive control device, and are characterized by this.

[0016] 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 repeated descriptions are omitted.

[0017] ≪Embodiment 1≫ FIG. 1 is a diagram showing the configuration of a motor unit 20 including a motor drive control device 1 according to Embodiment 1.

[0018] As shown in FIG. 1, the motor unit 20 has, for example, a motor 10 and a motor drive control device 1.

[0019] The motor 10 is a motor having a stator (not shown) and a rotor (not shown) that include coils of a plurality of phases. For example, the motor 10 is a three-phase brushless DC motor having a stator and a rotor that include coils Lu, Lv, and Lw of three phases, such as a U phase, a V phase, and a W phase. The coils Lu, Lv, and Lw are, for example, Y-connected to each other, but are not limited thereto. In the following description, when the coils Lu, Lv, and Lw are not distinguished from each other, they may be referred to as "coil L".

[0020] The motor drive control device 1 is a device that controls the drive of the motor 10. The motor drive control device 1 has, for example, a sensorless drive control function that estimates the position of the rotor by detecting the zero cross of the back electromotive voltage (induced voltage) generated in the non-conducting phase coil of the motor 10 and performs drive control of the motor 10.

[0021] Specifically, the motor drive control device 1 includes a control circuit 2, a drive circuit 3, a back electromotive voltage detection circuit 6, and an RCD snubber circuit 7.

[0022] The control circuit 2 is a circuit that comprehensively controls the operation of the motor drive control device 1. The control circuit 2 is, for example, a program processing device having a configuration in which a processor such as a CPU, various storage devices such as a RAM, a ROM, and a flash memory, and peripheral circuits such as a counter (timer), an A / D conversion circuit, a D / A conversion circuit, a clock generation circuit, and an input / output interface circuit are connected to each other via a bus or a dedicated line. For example, the control circuit 2 is a microcontroller (MCU: Micro Controller Unit). The control circuit 2 is supplied with, for example, a power supply voltage Vdd. In the following description, the reference symbol Vdd represents not only the power supply voltage but also the power supply line (node) to which the power supply voltage is supplied.

[0023] The control circuit 2 has input terminals Pu, Pv, and Pw for inputting the back electromotive force (induced voltage) generated in the coils Lu, Lv, and Lw of each phase. The input terminals Pu, Pv, and Pw are provided corresponding to each phase of the motor 10. Specifically, input terminal Pu is for inputting the back electromotive force generated in the U-phase coil Lu, input terminal Pv is for inputting the back electromotive force generated in the V-phase coil Lv, and input terminal Pw is for inputting the back electromotive force generated in the W-phase coil Lw.

[0024] The control circuit 2 generates a drive control signal Sd for controlling the drive of the motor 10 based on known sensorless motor drive control technology. Specifically, the control circuit 2 generates a drive control signal Sd for controlling the drive of the motor 10 based on the detection results of the back electromotive force input to the input terminals Pu, Pv, and Pw. More specifically, when the back electromotive force generated in coil L is input to the input terminals Pu, Pv, and Pw of the control circuit 2 via the back electromotive force detection circuit 6 and the RCD snubber circuit 7, the control circuit 2 detects the zero-crossing of the back electromotive force generated in the non-energized phase coil L. Here, the zero-crossing of the back electromotive force refers to the timing when the back electromotive force switches from positive to negative or negative to positive with respect to the reference voltage.

[0025] The control circuit 2 rotates the motor 10 by generating a drive control signal Sd to switch the energized phase coil L based on the detection result of the back electromotive force crossing zero. For example, the control circuit 2 generates a drive control signal Sd to switch the energized phase coil L based on the detection result of the back electromotive force crossing zero so that the motor enters a drive state specified by a drive command signal Sc supplied from an external source (e.g., a higher-level device).

[0026] Here, the drive command signal Sc is a signal including a command related to the drive of the motor 10. For example, it includes a command indicating the target rotational speed (target number of revolutions) of the motor 10. Note that the drive command signal Sc may be various types 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 10, etc.

[0027] For example, when the drive command signal Sc includes a command indicating the target rotational speed of the motor 10, the control circuit 2 generates a drive control signal Sd based on the detection result of the zero cross of the back electromotive voltage so that the rotational speed of the motor 10 becomes the target rotational speed specified by the drive command signal Sc.

[0028] 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 the inverter circuit 5 described later.

[0029] The drive circuit 3 is a circuit that drives the motor 10 based on the drive control signal Sd. The drive circuit 3 and the control circuit 2 may be configured to be packaged as one semiconductor integrated circuit device (IC: Integrated Circuit), or may be configured to be individually packaged as separate integrated circuit devices.

[0030] A power supply voltage Vcc is supplied to the drive circuit 3. For example, Vdd < Vcc. Hereinafter, the reference symbol Vcc represents not only the power supply voltage but also the power supply line (node) to which the power supply voltage is supplied.

[0031] As shown in FIG. 1, the drive circuit 3 has, for example, a pre-drive circuit 4 and an inverter circuit 5.

[0032] The pre-drive circuit 4 is based on the drive control signal Sd output from the control circuit 2, and This circuit generates drive signals to drive the inverter circuit 5. For example, the pre-drive circuit 4 generates six types of drive signals Vuh, Vul, Vvh, Vvl, Vwh, and Vwl, each corresponding to one of the six types of PWM signals as the drive control signal Sd, and having sufficient power to drive the control electrodes (gate electrodes) of each drive transistor Q1 to Q6 in the inverter circuit 5.

[0033] The inverter circuit 5 is a circuit that drives the coils Lu, Lv, and Lw of the motor 10, which is the load, based on six types of input drive signals Vuh, Vul, Vvh, Vvl, Vwh, and Vwl. The inverter circuit 5 is connected between the power line Vcc and the ground potential GND (=0V).

[0034] As shown in Figure 1, the inverter circuit 5 has drive transistors Q1, Q2, Q3, Q4, Q5, and Q6. Drive transistors Q1 and Q2 are connected in series between the power supply line Vcc and the ground potential GND. Drive transistors Q3 and Q4 are connected in series between the power supply line Vcc and the ground potential GND. Drive transistors Q5 and Q6 are connected in series between the power supply line Vcc and the ground potential GND.

[0035] The driver transistors Q1, Q3, and Q5 are, for example, P-channel type MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors). The driver transistors Q2, Q4, and Q6 are, for example, N-channel type MOSFET transistors. Note that the types of driver transistors Q1, Q2, Q3, Q4, Q5, and Q6 are not limited to the examples given above.

[0036] In the inverter circuit 5, the corresponding drive signals Vuh, Vul, Vvh, Vvl, Vwh, and Vwl (six types of PWM signals) are input to the gate electrodes of each drive transistor Q1, Q2, Q3, Q4, Q5, and Q6, respectively, causing each drive transistor Q1 to Q6 to perform on / off operation (switching operation). As a result, power is supplied from the power line Vcc to the coils Lu, Lv, and Lw of each phase of the motor 10, causing the motor 10 to rotate.

[0037] Furthermore, the inverter circuit 5 may be connected to a current sensor (for example, a shunt resistor) for detecting the current flowing through the coils Lu, Lv, and Lw of each phase. Also, if the drive control signal Sd can drive each of the drive transistors Q1 to Q6 of the inverter circuit 5 without power shortage, the pre-drive circuit 4 does not need to be provided.

[0038] The back electromotive force detection circuit 6 is a circuit that detects the back electromotive force (induced voltage) generated in the coils Lu, Lv, and Lw when the drive circuit 3 is driving the motor 10 based on the drive control signal Sd. The back electromotive force detection circuit 6 includes, for example, a voltage divider circuit that divides and outputs the voltage at one terminal of each phase coil Lu, Lv, and Lw.

[0039] For example, the back electromotive force detection circuit 6 includes resistors R2u and R1u connected in series between node Nu, to which one terminal of the U-phase coil Lu is connected, and ground potential GND. The back electromotive force detection circuit 6 includes resistors R2v and R1v connected in series between node Nv, to which one terminal of the V-phase coil Lv is connected, and ground potential GND. The back electromotive force detection circuit 6 includes resistors R2w and R1w connected in series between node Nw, to which one terminal of the W-phase coil Lw is connected, and ground potential GND.

[0040] The RCD snubber circuit 7 suppresses voltage fluctuations input to each input terminal Pu, Pv, and Pw of the control circuit 2, and also suppresses negative current input to each input terminal Pu, Pv, and Pw. This is a circuit that clamps pressure.

[0041] The RCD snubber circuit 7 is provided between the back electromotive force detection circuit 6 and the input terminals Pu, Pv, and Pw of the control circuit 2. The RCD snubber circuit 7 suppresses fluctuations in the back electromotive force input to the input terminals Pu, Pv, and Pw via the back electromotive force detection circuit 6, and also limits the decrease in the voltage input to the input terminals Pu, Pv, and Pw when the voltage input to the input terminals Pu, Pv, and Pw becomes a negative voltage.

[0042] More specifically, the RCD snubber circuit 7 includes the circuit element pairs Sn1, Sn2, and Sn3, and the rectifier elements D1, D2, and D3.

[0043] The circuit element pairs Sn1, Sn2, and Sn3 include a resistor Rs and a capacitor Cs connected in series with each other. As shown in Figure 1, the circuit element pairs Sn1, Sn2, and Sn3 are provided between the input terminals Pu, Pv, and Pw of each phase of the control circuit 2, respectively. Specifically, one terminal of circuit element pair Sn1 is connected to input terminal Pu, and the other terminal of circuit element pair Sn1 is connected to input terminal Pv. One terminal of circuit element pair Sn2 is connected to input terminal Pv, and the other terminal of circuit element pair Sn2 is connected to input terminal Pw. One terminal of circuit element pair Sn3 is connected to input terminal Pw, and the other terminal of circuit element pair Sn3 is connected to input terminal Pu. In other words, the circuit element pairs Sn1, Sn2, and Sn3 are delta-connected between the input terminals Pu, Pv, and Pw.

[0044] More specifically, in circuit element pair Sn1, one terminal of capacitor Cs is connected to input terminal Pu, the other terminal of capacitor Cs is connected to one terminal of resistor Rs, and the other terminal of resistor Rs is connected to input terminal Pv. In circuit element pair Sn2, one terminal of capacitor Cs is connected to input terminal Pv, the other terminal of capacitor Cs is connected to one terminal of resistor Rs, and the other terminal of resistor Rs is connected to input terminal Pw. In circuit element pair Sn3, one terminal of capacitor Cs is connected to input terminal Pw, the other terminal of capacitor Cs is connected to one terminal of resistor Rs, and the other terminal of resistor Rs is connected to input terminal Pu.

[0045] Rectifier elements D1, D2, and D3 are provided in correspondence to each pair of circuit elements Sn1, Sn2, and Sn3. Rectifier elements D1, D2, and D3 allow current flowing in a predetermined direction to pass through while clamping the voltage, and interrupt current flowing in the opposite direction. Rectifier elements D1, D2, and D3 are, for example, diodes. The type of diode is not particularly limited.

[0046] In the following explanation, rectifier elements D1, D2, and D3 will be referred to as "diodes D1, D2, and D3," and when diodes D1, D2, and D3 are not distinguished, they will be referred to as "diode D." Also, when circuit element pairs Sn1, Sn2, and Sn3 are not distinguished, they will be referred to as "circuit element pair Sn."

[0047] The anode side of diode D is connected to an intermediate node where the resistor Rs and capacitor Cs of the circuit element pair Sn corresponding to diode D are connected, and the cathode side of diode D is connected to input terminals Pu, Pv, and Pw, to which one terminal of the circuit element pair Sn corresponding to diode D is connected.

[0048] For example, as shown in Figure 1, the anode electrode of rectifier element D1 is connected to an intermediate node N1 to which the resistor Rs and capacitor Cs of circuit element pair Sn1 are connected, and the cathode electrode of rectifier element D1 is connected to the input terminal Pu (one terminal of circuit element pair Sn1). The anode electrode of rectifier element D2 is connected to an intermediate node to which the resistor Rs and capacitor Cs of circuit element pair Sn2 are connected. It is connected to node N2, and the cathode electrode of rectifier element D2 is connected to input terminal Pv (one terminal of circuit element pair Sn2). The anode electrode of rectifier element D3 is connected to intermediate node N3, where the resistor Rs and capacitor Cs of circuit element pair Sn3 are connected, and the cathode electrode of rectifier element D3 is connected to input terminal Pw (one terminal of circuit element pair Sn3).

[0049] According to the RCD snubber circuit 7 of Embodiment 1, the ringing of the back electromotive force input to the input terminals Pu, Pv, and Pw of the control circuit 2 can be reduced. This will be explained in detail below with reference to Figures 2A and 2B.

[0050] Figure 2A shows an example of experimental results for the voltage in the motor drive control device 1 according to Embodiment 1.

[0051] Figure 2B shows an example of experimental voltage results for a motor drive control device without an RCD snubber circuit 7, as a comparative example of the motor drive control device 1 according to Embodiment 1.

[0052] In the graphs shown in Figures 2A and 2B, the horizontal axis represents time and the vertical axis represents voltage. The upper part of Figures 2A and 2B shows the voltage between the terminals of the motor coil (winding voltage), while the lower part of Figures 2A and 2B shows the voltages input to the control circuit's input terminals Pu, Pv, and Pw (voltages divided by the back EMF detection circuit 6). The scale of the vertical axis in the upper part of Figures 2A and 2B is the same as the scale of the vertical axis (voltage) in the lower part of Figures 2B.

[0053] As shown in Figure 2B, if an RCD snubber circuit 7 is not provided between the back electromotive force detection circuit 6 and the control circuit 2, a large ringing occurs in the voltage input to the control circuit 2. In contrast, as shown in Figure 2A, according to the motor drive control device 1 of Embodiment 1, by providing an RCD snubber circuit 7 between the back electromotive force detection circuit 6 and the control circuit 2, fluctuations in the back electromotive force, i.e., the voltages at the input terminals Pu, Pv, Pw of the control circuit 2, are suppressed. That is, when a positive induced voltage is generated in the coil L of the non-energized phase among the coils Lu, Lv, Lw, current flows from the node where the induced voltage was generated among the nodes Nu, Nv, Nw through the back electromotive force detection circuit 6 to the resistor Rs and capacitor Cs of the circuit element pair Sn, thereby consuming energy in the resistor Rs. This suppresses sharp fluctuations in the voltages (back electromotive force) input to the input terminals Pu, Pv, and Pw of the control circuit 2, thereby reducing ringing. This prevents the control circuit 2 from erroneously detecting zero-crossings of the back electromotive force, and enables stable drive control of the motor 10.

[0054] Furthermore, the anode electrode side of diode D is connected to an intermediate node where the resistor Rs and capacitor Cs of the circuit element pair Sn corresponding to diode D are connected, and the cathode electrode side of diode D is connected to one terminal of the circuit element pair Sn corresponding to diode D. As a result, even if the voltage input to input terminals Pu, Pv, Pw becomes a negative voltage, the rectifier elements D1, D2, and D3 clamp the negative voltage input to input terminals Pu, Pv, Pw, thereby limiting the negative voltage applied to control circuit 2 and preventing failure of control circuit 2. Specifically, the negative voltage input to input terminals Pu, Pv, Pw is clamped by the forward voltage of diode D. For example, if the forward voltage of diode D is approximately 0.7V, the negative voltage input to input terminals Pu, Pv, Pw is clamped at approximately -0.7V. If the allowable negative voltage range at the input terminals Pu, Pv, and Pw of the control circuit 2 is smaller than the clamp voltage of diode D, the negative voltage applied to the input terminals Pu, Pv, and Pw can be limited, thereby preventing failure of the control circuit 2.

[0055] <Embodiment 2> Figure 3 shows a motor unit 20A equipped with a motor drive control device 1A according to Embodiment 2. This is a diagram showing the configuration.

[0056] The motor unit 20A shown in Figure 3 differs from the motor unit 20 according to Embodiment 1 in the connection point of the diode in the RCD snubber circuit, but is otherwise the same as the motor unit 20 according to Embodiment 1.

[0057] Specifically, the RCD snubber circuit 7A has circuit element pairs Sn1, Sn2, Sn3 and diodes D1, D2, D3. Similar to the RCD snubber circuit 7 according to Embodiment 1, the circuit element pairs Sn1, Sn2, and Sn3 are provided between the input terminals Pu, Pv, and Pw of each phase, respectively. That is, circuit element pair Sn1 is connected between input terminal Pu and input terminal Pv, circuit element pair Sn2 is connected between input terminal Pv and input terminal Pw, and circuit element pair Sn3 is connected between input terminal Pv and input terminal Pw.

[0058] In the RCD snubber circuit 7A according to Embodiment 2, the anode electrode side of the diode D is connected to ground potential GND, and the cathode electrode side of the diode D is connected to an intermediate node where the resistor Rs and capacitor Cs of the circuit element pair Sn corresponding to the diode D are connected.

[0059] For example, as shown in Figure 3, the anode electrode of rectifier element D1 is connected to ground potential GND, and the cathode electrode of rectifier element D1 is connected to intermediate node N1, to which the resistor Rs and capacitor Cs of circuit element pair Sn1 are connected. The anode electrode of rectifier element D2 is connected to ground potential GND, and the cathode electrode of rectifier element D2 is connected to intermediate node N2, to which the resistor Rs and capacitor Cs of circuit element pair Sn2 are connected. The anode electrode of rectifier element D3 is connected to ground potential GND, and the cathode electrode of rectifier element D3 is connected to intermediate node N3, to which the resistor Rs and capacitor Cs of circuit element pair Sn3 are connected.

[0060] As described above, the RCD snubber circuit 7A according to Embodiment 2 can reduce ringing of the voltage (back electromotive force) input to the input terminals Pu, Pv, and Pw of the control circuit 2, similar to the RCD snubber circuit 7 according to Embodiment 1.

[0061] Furthermore, the anode electrode side of diode D is connected to ground potential, and the cathode electrode side of diode D is connected to an intermediate node where the resistor Rs and capacitor Cs of the circuit element pair Sn corresponding to diode D are connected. As a result, even if the voltage input to input terminals Pu, Pv, and Pw becomes negative, the voltage input to input terminals Pu, Pv, and Pw is clamped with respect to ground potential GND. This limits the negative voltage applied to control circuit 2, thereby preventing failure of control circuit 2.

[0062] <Embodiment 3> Figure 4 shows the configuration of a motor unit 20B equipped with a motor drive control device 1B according to Embodiment 3.

[0063] The motor unit 20B shown in Figure 4 differs from the motor unit 20 according to Embodiment 1 in the connection points of the circuit element pairs and diodes of the RCD snubber circuit, but is otherwise the same as the motor unit 20 according to Embodiment 1.

[0064] Specifically, the RCD snubber circuit 7B has the same circuit element pairs Sn1, Sn2, Sn3 and diodes D1, D2, D3 as the RCD snubber circuit 7 according to Embodiment 1.

[0065] The circuit element pairs Sn1, Sn2, and Sn3 correspond to each of the input terminals Pu, Pv, and Pw for each phase. Specifically, one terminal of a pair of circuit elements Sn is connected to the corresponding input terminal, and the other terminal of a pair of circuit elements Sn is connected in common with the other terminal of another pair of circuit elements Sn. In other words, the pairs of circuit elements Sn1, Sn2, and Sn3 are Y-connected between the input terminals Pu, Pv, and Pw.

[0066] For example, as shown in Figure 4, one terminal of circuit element pair Sn1 is connected to input terminal Pu, and the other terminal of circuit element pair Sn1 is connected to common node Nn. One terminal of circuit element pair Sn2 is connected to input terminal Pv, and the other terminal of circuit element pair Sn2 is connected to common node Nn. One terminal of circuit element pair Sn3 is connected to input terminal Pw, and the other terminal of circuit element pair Sn3 is connected to common node Nn.

[0067] In the RCD snubber circuit 7B, the anode side of diode D is connected to an intermediate node where the resistor Rs and capacitor Cs of the circuit element pair Sn corresponding to diode D are connected, and the cathode side of diode D is connected to one terminal of the circuit element pair Sn corresponding to diode D.

[0068] For example, as shown in Figure 4, the anode electrode of diode D1 is connected to intermediate node N1, which is connected to the resistor Rs and capacitor Cs of circuit element pair Sn1, and the cathode electrode of diode D1 is connected to input terminal Pu (one terminal of circuit element pair Sn1). The anode electrode of diode D2 is connected to intermediate node N2, which is connected to the resistor Rs and capacitor Cs of circuit element pair Sn2, and the cathode electrode of diode D2 is connected to input terminal Pv (one terminal of circuit element pair Sn1). The anode electrode of diode D3 is connected to intermediate node N3, which is connected to the resistor Rs and capacitor Cs of circuit element pair Sn3, and the cathode electrode of diode D3 is connected to input terminal Pw (one terminal of circuit element pair Sn1).

[0069] As described above, the RCD snubber circuit 7B according to Embodiment 3 can reduce ringing of the voltage (back electromotive force) input to the input terminals Pu, Pv, and Pw of the control circuit 2, similar to the RCD snubber circuit 7 according to Embodiment 1.

[0070] Furthermore, the anode electrode side of diode D is connected to an intermediate node where the resistor Rs and capacitor Cs of the circuit element pair Sn corresponding to diode D are connected, and the cathode electrode side of diode D is connected to one terminal of the circuit element pair Sn corresponding to diode D. With this configuration, even if the voltage input to input terminals Pu, Pv, and Pw becomes negative, the voltage input to input terminals Pu, Pv, and Pw is clamped with reference to the voltage of the common node Nn. This limits the negative voltage applied to control circuit 2, thereby preventing failure of control circuit 2.

[0071] <Embodiment 4> Figure 5 shows the configuration of a motor unit 20C equipped with a motor drive control device 1C according to Embodiment 4.

[0072] The motor unit 20C shown in Figure 5 differs from the motor unit 20 according to Embodiment 1 in the connection points of the circuit element pairs and diodes of the RCD snubber circuit, but is otherwise the same as the motor unit 20 according to Embodiment 1.

[0073] Specifically, the RCD snubber circuit 7C has circuit element pairs Sn1, Sn2, Sn3 and diodes D1, D2, D3. Similar to the RCD snubber circuit 7B according to Embodiment 3, the circuit element pairs Sn1, Sn2, Sn3 are provided corresponding to each of the input terminals Pu, Pv, and Pw for each phase.

[0074] In the RCD snubber circuit 7C, the anode side of diode D is connected to ground potential GND, and the cathode side of diode D is connected to an intermediate node where the resistor Rs and capacitor Cs of the circuit element pair Sn corresponding to diode D are connected.

[0075] For example, as shown in Figure 5, the anode electrode of diode D1 is connected to ground potential GND, and the cathode electrode of diode D1 is connected to intermediate node N1, which is connected to the resistor Rs and capacitor Cs of circuit element pair Sn1. The anode electrode of diode D2 is connected to ground potential GND, and the cathode electrode of diode D2 is connected to intermediate node N2, which is connected to the resistor Rs and capacitor Cs of circuit element pair Sn2. The anode electrode of diode D3 is connected to ground potential GND, and the cathode electrode of diode D3 is connected to intermediate node N3, which is connected to the resistor Rs and capacitor Cs of circuit element pair Sn3.

[0076] As described above, the RCD snubber circuit 7C according to Embodiment 4 can reduce ringing of the voltage (back electromotive force) input to the input terminals Pu, Pv, and Pw of the control circuit 2, similar to the RCD snubber circuit 7 according to Embodiment 1.

[0077] Furthermore, the anode electrode side of diode D is connected to ground potential GND, and the cathode electrode side of diode D is connected to an intermediate node where the resistor Rs and capacitor Cs of the circuit element pair Sn corresponding to diode D are connected. As a result, even if the voltage input to input terminals Pu, Pv, and Pw becomes negative, the voltage input to input terminals Pu, Pv, and Pw is clamped with respect to ground potential GND. This limits the negative voltage applied to control circuit 2, thereby preventing failure of control circuit 2.

[0078] <<Extension of the Embodiment>> Although the present inventors have described the invention in detail based on embodiments, it goes without saying that the present invention is not limited thereto and can be modified in various ways without departing from its essence.

[0079] For example, in the above embodiment, the motor 10 is described as a three-phase brushless DC motor, but the invention is not limited to this, and the motor 10 may be a stepping motor.

[0080] Furthermore, while the above embodiment illustrates the application of the RCD snubber circuits 7, 7A, 7B, and 7C to a motor drive control device that performs sensorless motor drive control, the embodiment is not limited to this, and the RCD snubber circuits 7, 7A, 7B, and 7C can be applied to various electronic circuits that detect the back electromotive force of a coil. For example, the RCD snubber circuits 7, 7A, 7B, and 7C according to this embodiment can be applied to a motor drive control device that determines whether a motor has lost step based on the detection result of the back electromotive force. [Explanation of Symbols]

[0081] 1, 1A, 1B, 1C, 1D... Motor drive control device, 2... Control circuit, 3... Drive circuit, 4... Pre-drive circuit, 5... Inverter circuit, 6... Back EMF detection circuit, 7, 7A, 7B, 7C... RCD snubber circuit, 10... Motor, 20, 20A, 20B, 20C... Motor unit, N1, N2, N3... Intermediate node, Nn... Common node, Cs... Capacitor, Rs... Resistor, Sn1, Sn2, Sn3... Circuit element pair, D1, D2, D3... Rectifier element (diode), Pu, Pv, Pw... Input terminal, Vdd, Vcc... Power supply voltage (power line), GND... Ground potential, Lu, Lv, Lw... Coil.

Claims

1. A motor having a stator and rotor including coils of multiple phases, each of which has an input terminal for inputting the back electromotive force generated in the coils, and a control circuit that generates a drive control signal for controlling the drive of the motor based on the detection result of the back electromotive force input to the input terminal, A drive circuit that drives the motor based on the drive control signal, The system includes an RCD snubber circuit connected between the coil and each of the input terminals, which suppresses fluctuations in the voltage input to each of the input terminals and clamps negative voltages input to each of the input terminals. Motor drive control device.

2. In the motor drive control device according to claim 1, The RCD snubber circuit includes a pair of circuit elements, each provided between the input terminals of each phase, which are connected in series with each other, and a diode provided corresponding to each pair of circuit elements. The anode side of the diode is connected to an intermediate node in the circuit element pair corresponding to the diode, where the resistor and the capacitor are connected, and the cathode side of the diode is connected to the input terminal to which one terminal of the circuit element pair corresponding to the diode is connected. Motor drive control device.

3. In the motor drive control device according to claim 1, The RCD snubber circuit includes a pair of circuit elements, each provided between the input terminals of each phase, which are connected in series with each other, and a diode provided corresponding to each pair of circuit elements. The anode side of the diode is connected to ground potential, and the cathode side of the diode is connected to an intermediate node in the circuit element pair corresponding to the diode, where the resistor and the capacitor are connected. Motor drive control device.

4. In the motor drive control device according to claim 1, The RCD snubber circuit includes a pair of circuit elements, each corresponding to the input terminal of each phase, which includes a resistor and a capacitor connected in series with each other, and a diode, which is provided corresponding to each pair of circuit elements. One terminal of the pair of circuit elements is connected to the input terminal corresponding to that pair of circuit elements, and the other terminal of the pair of circuit elements is connected in common with the other terminal of another pair of circuit elements. The anode side of the diode is connected to an intermediate node in the circuit element pair corresponding to the diode, where the resistor and the capacitor are connected, and the cathode side of the diode is connected to the input terminal to which one terminal of the circuit element pair corresponding to the diode is connected. Motor drive control device.

5. In the motor drive control device according to claim 1, The RCD snubber circuit includes a pair of circuit elements, each corresponding to the input terminal of each phase, which includes a resistor and a capacitor connected in series with each other, and a diode, which is provided corresponding to each pair of circuit elements. One terminal of the pair of circuit elements is connected to the input terminal corresponding to that pair of circuit elements, and the other terminal of the pair of circuit elements is connected in common with the other terminal of another pair of circuit elements. The anode electrode side of the diode is connected to ground potential, and the cathode of the diode The diode electrode side is connected to an intermediate node in the circuit element pair corresponding to the diode, where the resistor and the capacitor are connected. Motor drive control device.

6. A motor drive control device according to any one of claims 1 to 5, The motor is driven by the motor drive control device. Motor unit.

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