Motor driver circuit, positioning device using the same, hard disk drive, and motor driving method

Abstract

To improve accuracy of current detection.SOLUTION: An A / D converter converts an error signal VERR based on an error between a current feedback signal VFB and a reference signal VDAC into a digital signal DERR at the timing of an S / H signal. In a first mode, a compensator uses a value A1 of the error signal captured by the A / D converter at the timing of a negative edge of a first pulse PWMA as a value A1' of the error signal at the timing of a positive edge of a second pulse PWMB.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a motor driver circuit. [Background technology]

[0002] Linear motors (linear actuators) are used in a variety of electronic devices and industrial machines to position objects. A voice coil motor is a type of linear motor that can control the position of a mover depending on the drive current supplied. The drive circuit of a voice coil motor performs feedback control to bring the current flowing through the voice coil motor closer to the target current that defines the target position. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-161807 Summary of the Invention [Problem to be solved by the invention]

[0004] There are two types of driver circuits for constant current driven motors: analog and digital. Analog driver circuits are difficult to design because they require phase compensation of the error amplifier. In contrast, digital types make phase compensation easy by using a PI controller or PID controller.

[0005] In the digital system, the current flowing through the motor must be converted into a digital signal. Figure 1 is a diagram explaining current detection.

[0006] A sense resistor Rs and a current sense amplifier AMP1 are provided for current detection. The sense resistor Rs is connected in series with the motor M between the A-phase output (AOUT) and B-phase output (BOUT) of the motor driver circuit. The drive current I DRVA voltage drop Vcs proportional to the sense resistor Rs occurs. The current sense amplifier AMP1 amplifies the voltage drop Vcs across the sense resistor Rs and outputs the current feedback signal V FB Generate.

[0007] The present inventors have studied current detection using the sense resistor Rs and have come to recognize the following problem.

[0008] In a PWM-driven system, AOUT and BOUT switch (transition) independently. The common-mode components of the two input voltages Va and Vb of the current sense amplifier AMP1 are relatively less affected by the transition of BOUT, and more affected by the transition of AOUT.

[0009] That is, the AC CMRR (Common Mode Rejection Ratio) of the current sense amplifier AMP1 differs during the transition of AOUT and during the transition of BOUT, causing an error in current detection.

[0010] The present disclosure has been made in view of the above-mentioned problems, and one exemplary purpose of an embodiment thereof is to provide a driver circuit with improved accuracy in current detection. [Means for solving the problem]

[0011] One aspect of the present disclosure relates to a motor driver circuit, comprising: a first output terminal to be connected to a first end of a motor to be driven via a sense resistor; a second output terminal to be connected to a second end of the motor; an error detector that generates an error signal based on an error between a current feedback signal based on a voltage drop across the sense resistor and a reference signal; an A / D converter that converts the error signal into a digital signal and receives it; a compensator that generates a voltage command value based on the error signal received by the A / D converter; a D / A converter that converts the voltage command value into an analog control signal; a pulse width modulator that compares the analog control signal with a first triangular wave to generate a first pulse, compares the analog control signal with a second triangular wave that is in phase opposite to the first triangular wave to generate a second pulse; and an output stage that generates a first drive voltage corresponding to the first pulse at the first output terminal and a second drive voltage corresponding to the second pulse at the second output terminal. In the first mode, the compensator uses the error signal captured by the A / D converter at the timing of the negative edge of the first pulse as the error signal at the timing of the positive edge of the second pulse.

[0012] Another aspect of the present disclosure is a motor driver circuit. The motor driver circuit includes a first output terminal to be connected to a first end of a motor to be driven via a sense resistor, a second output terminal to be connected to a second end of the motor, a current sense amplifier that generates a current feedback signal based on the voltage drop across the sense resistor, a feedback controller that generates a voltage command value so that the current feedback signal approaches a reference signal, a pulse width modulator that generates a first pulse and a second pulse having complementary duty cycles according to the voltage command value, the first pulse and the second pulse having centers of high periods aligned with each other, and an output stage that generates a first drive voltage according to the first pulse at the first output terminal and a second drive voltage according to the second pulse at the second output terminal. The feedback controller includes an A / D converter that converts an analog signal according to the current feedback signal into a digital signal and receives the digital signal, and a digital circuit that processes the digital signal to generate a voltage command value. In the first mode, the digital circuit uses the digital signal captured by the A / D converter at the timing of the negative edge of the first pulse as the digital signal at the timing of the positive edge of the second pulse.

[0013] Yet another aspect of the present disclosure is a motor driving method. The driving method includes the steps of connecting a sense resistor in series with a first end of the motor, generating a current feedback signal based on a voltage drop across the sense resistor, generating an error signal corresponding to an error between the current feedback signal and a reference signal, converting the error signal into a digital signal using an A / D converter, generating a voltage command value corresponding to the digital signal, converting the voltage command value into an analog control signal, comparing the analog control signal with a first triangular wave to generate a first pulse, comparing the analog control signal with a second triangular wave that is out of phase with the first triangular wave to generate a second pulse, and applying a first drive voltage corresponding to the first pulse and a second drive voltage corresponding to the second pulse to the motor. In a first mode, the step of generating the voltage command value uses the digital signal captured by the A / D converter at the timing of the negative edge of the first pulse as a digital signal at the timing of the positive edge of the second pulse.

[0014] Yet another aspect of the present disclosure is also a motor driving method. This driving method includes the steps of connecting a sense resistor in series with a first end of the motor, generating a current feedback signal based on a voltage drop across the sense resistor, generating a voltage command value so that the current feedback signal approaches a reference signal, generating a first pulse and a second pulse having complementary duty cycles according to the voltage command value, the first pulse and the second pulse having a center of a high section of the first pulse aligned with a center of a high section of the second pulse, and applying a first drive voltage according to the first pulse and a second drive voltage according to the second pulse to the motor. The step of generating a voltage command value includes the steps of converting an analog signal according to the current feedback signal into a digital signal by an A / D converter and acquiring the digital signal, and processing the digital signal to generate a voltage command value. In a first mode, the step of generating a voltage command value uses the digital signal acquired by the A / D converter at the timing of the negative edge of the first pulse as the digital signal at the timing of the positive edge of the second pulse.

[0015] Any combination of the above elements, or mutual substitution of elements or expressions between methods, devices, systems, etc., are also valid aspects of the present invention or the present disclosure. Furthermore, the description in this section (Means for Solving the Problems) does not explain all essential features of the present invention, and therefore, subcombinations of the described features may also constitute the present invention. [Effects of the Invention]

[0016] According to certain aspects of the present disclosure, the accuracy of current detection can be improved. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram illustrating current detection. [Figure 2] FIG. 2 is a block diagram of a positioning device including a motor driver circuit according to the embodiment. [Figure 3] FIG. 3 is a diagram showing input / output characteristics of the motor driver circuit of FIG. [Figure 4] FIG. 4 is an operation waveform diagram of the motor driver circuit in the first mode. [Figure 5] FIG. 5 is an operational waveform diagram of the motor driver circuit in the second mode. [Figure 6] FIG. 6 is a circuit diagram showing an example of the configuration of the current sense amplifier and the error detection amplifier. [Figure 7] FIG. 7 is a circuit diagram of a motor driver circuit according to another embodiment. [Figure 8] FIG. 8 is a circuit diagram of a motor driver circuit according to another embodiment. [Figure 9] FIG. 9 is a diagram showing a hard disk drive equipped with a motor driver circuit. DETAILED DESCRIPTION OF THE INVENTION

[0018] (Outline of the embodiment) A summary of some exemplary embodiments of the present disclosure is provided. This summary is intended to provide a simplified overview of some concepts of one or more embodiments in order to provide a basic understanding of the embodiments as a prelude to the more detailed description that follows. It is not intended to limit the scope of the invention or disclosure. This summary is not an exhaustive overview of all possible embodiments, and is not intended to identify key elements of all embodiments or to delineate the scope of some or all aspects. For convenience, the term "one embodiment" may refer to one embodiment (example or variant) or multiple embodiments (examples or variants) disclosed herein.

[0019] A motor driver circuit according to one embodiment includes a first output terminal to be connected to a first end of a motor to be driven via a sense resistor, a second output terminal to be connected to a second end of the motor, an error detector that generates an error signal based on an error between a current feedback signal based on a voltage drop across the sense resistor and a reference signal, an A / D converter that converts the error signal into a digital signal and receives it, a compensator that generates a voltage command value based on the error signal received by the A / D converter, a D / A converter that converts the voltage command value into an analog control signal, a pulse width modulator that compares the analog control signal with a first triangular wave to generate a first pulse, compares the analog control signal with a second triangular wave that is out of phase with the first triangular wave to generate a second pulse, and an output stage that generates a first drive voltage at the first output terminal corresponding to the first pulse and a second drive voltage at the second output terminal corresponding to the second pulse. In a first mode, the compensator uses the error signal received by the A / D converter at the timing of the negative edge of the first pulse as the error signal at the timing of the positive edge of the second pulse.

[0020] In a system that uses PWM drive and detects current using a sense resistor connected in series with the motor, the sense resistor introduces asymmetry into the output stage. Specifically, the AC-CMRR differs when the first output transitions and when the second output transitions, resulting in errors in current detection. Therefore, by copying the error signal acquired using the transition of the first pulse as a trigger and using it as the error signal when the second pulse transitions, the effect of the difference in AC CMRR between the first and second output terminals can be reduced, improving current detection accuracy. In addition, because the negative edge of the first pulse occurs before the transition of the first drive voltage, current detection is possible without being affected by the transition of the first drive voltage.

[0021] In one embodiment, in the first mode, the compensator may use the error signal captured by the A / D converter at the timing of the positive edge of the first pulse as the error signal at the timing of the negative edge of the second pulse.

[0022] In one embodiment, in the second mode, the compensator may use the error signal captured by the A / D converter at the timing of the positive edge of the second pulse as the error signal at the timing of the negative edge of the first pulse. If the current detection accuracy decreases at the timing of the transition of the first pulse, the compensator can improve the current detection accuracy by switching to the second mode and using the error signal captured based on the second pulse.

[0023] In one embodiment, in the second mode, the compensator may use the error signal captured by the A / D converter at the timing of the negative edge of the second pulse as the error signal at the timing of the positive edge of the first pulse.

[0024] In one embodiment, the first mode and the second mode may be switchable depending on the voltage command value. As the voltage command value increases, the low period of the first pulse becomes shorter. As a result, current detection at the timing of the positive edge of the first pulse may be affected by the transition of the first drive voltage immediately before that, which may result in a decrease in current detection accuracy. Therefore, when the voltage command value is high, the second mode is adopted, and current detection is switched to one based on the second pulse, thereby suppressing a decrease in current detection accuracy.

[0025] A motor driver circuit according to one embodiment includes a first output terminal to be connected to a first end of a motor to be driven via a sense resistor, a second output terminal to be connected to a second end of the motor, a current sense amplifier to generate a current feedback signal based on the voltage drop across the sense resistor, a feedback controller to generate a voltage command value so that the current feedback signal approaches a reference signal, a pulse width modulator to generate a first pulse and a second pulse having complementary duty cycles according to the voltage command value, the first pulse and the second pulse having a center of a high period of the first pulse aligned with a center of a high period of the second pulse, and an output stage to generate a first drive voltage according to the first pulse at the first output terminal and a second drive voltage according to the second pulse at the second output terminal. The feedback controller includes an A / D converter that converts an analog signal according to the current feedback signal into a digital signal and captures it, and a digital circuit that processes the digital signal to generate a voltage command value. In a first mode, the digital circuit uses the digital signal captured by the A / D converter at the timing of the negative edge of the first pulse as the digital signal at the timing of the positive edge of the second pulse.

[0026] In one embodiment, in the first mode, the digital circuit may use the digital signal captured by the A / D converter at the timing of the positive edge of the first pulse as the digital signal at the timing of the negative edge of the second pulse.

[0027] In one embodiment, in the second mode, the digital circuit may use the digital signal captured by the A / D converter at the timing of the positive edge of the second pulse as the digital signal at the timing of the negative edge of the first pulse.

[0028] In one embodiment, in the second mode, the digital circuit may use the digital signal captured by the A / D converter at the timing of the negative edge of the second pulse as the digital signal at the timing of the positive edge of the first pulse.

[0029] In one embodiment, the first mode and the second mode may be switchable depending on the voltage command value.

[0030] In one embodiment, the motor may be a linear motor. In one embodiment, the linear motor may be a voice coil motor.

[0031] In one embodiment, the motor driver circuit may be monolithically integrated on a single semiconductor substrate. "Monolithic integration" includes cases where all of the circuit components are formed on a semiconductor substrate, or where the main components of the circuit are integrated, and some resistors and capacitors for adjusting circuit constants may be provided outside the semiconductor substrate. By integrating the circuit on a single chip, the circuit area can be reduced and the characteristics of the circuit elements can be maintained uniformly.

[0032] A positioning device according to one embodiment includes a linear motor and any of the above-described motor driver circuits that drive the linear motor.

[0033] A hard disk drive according to one embodiment includes the above-described positioning device.

[0034] (Embodiment) Preferred embodiments will be described below with reference to the drawings. The same or equivalent components, parts, and processes shown in each drawing will be given the same reference numerals, and redundant explanations will be omitted as appropriate. Furthermore, the embodiments are examples and do not limit the disclosure and invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the disclosure and invention.

[0035] In this specification, "a state in which component A is connected to component B" includes a case in which component A and component B are directly physically connected, and a case in which component A and component B are indirectly connected via other components that do not substantially affect the electrical connection state between them or impair the function or effect achieved by their combination.

[0036] Similarly, "a state in which component C is provided between component A and component B" includes not only cases in which components A and C, or components B and C, are directly connected, but also cases in which they are indirectly connected via other components that do not substantially affect the electrical connection state between them or impair the functions or effects achieved by their combination.

[0037] In addition, the vertical and horizontal axes of the waveform diagrams and time charts shown in this specification have been appropriately enlarged or reduced to facilitate understanding, and each waveform shown has also been simplified to facilitate understanding.

[0038] 2 is a block diagram of a positioning device 100 including a motor driver circuit 200 according to an embodiment. The positioning device 100 includes a linear motor 102, a host controller 104, the motor driver circuit 200, and a sense resistor Rs.

[0039] The upper controller 104 comprehensively controls the positioning device 100. The upper controller 104 generates position control data POS indicating a target position of the linear motor 102, and transmits the position control data POS to the motor driver circuit 200. The upper controller 104 is configured by, for example, a microcontroller, an FPGA (Field Programmable Gate Array), or an ASIC (Application Specific Integrated Circuit).

[0040] The motor driver circuit 200 receives the position control data POS and outputs a driving current I DRVis supplied to the linear motor 102. The linear motor 102 is, for example, a voice coil motor, and its mover is driven by a driving current I DRV The displacement is determined by the amount of

[0041] Next, we will explain the configuration of the motor driver circuit 200. The motor driver circuit 200 is a functional IC (Integrated Circuit) that includes a current command generation unit 210, a feedback controller 220, a pulse width modulator 240, a current sense amplifier 250, and an output stage 260, and is integrated on a single semiconductor substrate.

[0042] The motor driver circuit 200 includes a first output terminal (A-phase output) AOUT, a second output terminal (B-phase output) BOUT, and a current detection terminal ISNS. One end of the linear motor 102 is connected to the AOUT terminal via a sense resistor Rs. The other end of the linear motor 102 is connected to the BOUT terminal. The ISNS terminal is connected to one end of the linear motor 102.

[0043] The current command generator 210 generates a driving current I DRV Analog command signal V indicating the target value DAC For example, the current command generating unit 210 includes an interface circuit 212, a logic circuit 214, and a D / A converter 216. The interface circuit 212 is connected to the upper controller 104 and receives various control data including the position control data POS. The interface circuit 212 generates, for example, I 2The interface circuit 212 may be an C (Inter IC) interface or an SPI (Serial Peripheral Interface). For example, the control data from the interface circuit 212 includes a code indicating a target position of the mover of the linear motor 102. The logic circuit 214 outputs a control code based on the received code to the D / A converter 216. The control code may be the same as the code received from the upper controller 104, or may be a different code obtained by calculating the received code. The D / A converter 216 converts the control code generated by the logic circuit 214 into an analog command signal V DAC Convert to.

[0044] The configuration of the current command generating unit 210 is not limited to this, and an analog command signal V DAC The configuration may be such that the sensor receives the signal.

[0045] The current sense amplifier 250 is connected to the AOUT terminal and the ISNS terminal, and detects the drive current I flowing through the linear motor 102 based on the voltage drop across the sense resistor Rs. DRV Current feedback signal V FB In addition to the AOUT terminal, a terminal KSNS for current detection may be added, and the current sense amplifier 250 may amplify the potential difference between the terminals ISNS and KSNS.

[0046] For example, the current feedback signal V FB is expressed by equation (1). k, V CMREF is an arbitrary constant. V FB =k×I DRV +V CMREF …(1)

[0047] The feedback controller 220 generates a current feedback signal V FB is the reference signal, and the analog command signal V DAC The voltage command value V is set by feedback so that it approaches CTRL Generate.

[0048] The feedback controller 220 includes an error detection amplifier 230, an A / D converter 222, a digital compensator 224, and a D / A converter 226. The error detection amplifier 230 outputs a current feedback signal V FB and analog command signal V DAC The drive current I DRV and its target amount I REF Analog error signal V indicating the error between ERR Generate. V ERR =(I REF -I DRV )×g g is a finite gain.

[0049] The A / D converter 222 converts the analog error signal V generated by the error detection amplifier 230 into ERR is the digital error signal D ERR Convert the analog error signal V ERR is the drive current I DRV Specifically, it is a signal that indicates the drive current I DRV and a signal indicating the error between the target amount and the actual amount.

[0050] The digital compensator 224 converts the digital error signal D ERR Based on this, the digital control amount D CTRL The digital compensator 224 includes a PI (proportional integral) compensator and a PID (proportional integral derivative) compensator. The PI compensator generates a digital error signal D ERR Proportional gain K P and multiplying it to generate a digital error signal D ERR The integral value of integral gain K I and add them together to get the digital control amount D CTRL Generate.

[0051] The PID compensator generates a digital error signal D ERR Proportional gain K P and multiplying it to generate a digital error signal D ERR The integral value of integral gain K I and multiplying it to generate a digital error signal D ERR The differential gain K Dand add them together to get the digital control amount D CTRL The PI compensator and PID compensator are also called PI controllers and PID controllers. The PI compensator and PID compensator can be selected depending on the characteristics of the controlled object.

[0052] The D / A converter 226 outputs the digital control variable D CTRL analog control signal V CTRL Converts the analog control signal V CTRL is a command value of the voltage to be applied between both ends of the linear motor 102, and is also called a voltage command value.

[0053] The pulse width modulator 240 outputs a voltage command value V CTRL The duty cycle of the PWMA signal is determined by the voltage command value V. CTRL The duty cycle of the PWM signal is positively correlated with the voltage command value V CTRL The center of the high section of the PWMA signal is aligned on the time axis with the center of the high section of the PWMB signal, and the center of the low section of the PWMA signal is aligned on the time axis with the center of the low section of the PWMB signal.

[0054] The configuration of the pulse width modulator 240 is not particularly limited, and can be configured using known technology.

[0055] The pulse width modulator 240 generates a first triangular wave TRIA and a second triangular wave TRIB that are in opposite phases to each other, and combines the first triangular wave TRIA with a voltage command value V CTRL The first pulse PWMA is generated by comparing the second triangular wave TRIB with the voltage command value V CTRL A second pulse PWMA can be generated by comparing the two.

[0056] The output stage 260 outputs a first driving voltage V to the AOUT terminal in response to the first pulse PWMA. OUTA In response to the second pulse PWMB, the second drive voltage V is generated at the BOUT pin.OUTB The output stage 260 includes a first driver 262 and a second driver 264.

[0057] The first driver 262 generates a pulsed first driving voltage V OUTA is generated at the AOUT terminal and supplied to one end of the linear motor 102 via the sense resistor Rs. The second driver 264 generates a pulsed second drive voltage V OUTB is generated at the BOUT terminal and supplied to the other end of the linear motor 102.

[0058] Specifically, the output stage 260 repeats four periods φ1 to φ4. (i) First period φ1 A-phase drive voltage V OUTA is low, B phase drive voltage V OUTB Garo (ii) Second period φ2 A-phase drive voltage V OUTA is high, B phase drive voltage V OUTB Garo (iii) Third period φ3 A-phase drive voltage V OUTA is high, B phase drive voltage V OUTB High (iv) 4th period φ4 A-phase drive voltage V OUTA is high, B phase drive voltage V OUTB Garo

[0059] The length of the first period φ1 is equal to the length of the third period φ3, and the length of the second period φ2 is equal to the length of the fourth period φ4.

[0060] The A / D converter 222 is triggered by a timing signal corresponding to the edges of the first pulse PWMA and the second pulse PWMB generated by the pulse width modulator 240, and generates the analog error signal V ERR is the digital error signal D ERRThat is, the A / D converter 222 converts the digital error signal D into a digital error signal D at the timing of the positive edge and negative edge of the first pulse PWMA and the timing of the positive edge and negative edge of the second pulse PWMB. ERR It is possible to incorporate.

[0061] The motor driver circuit 200 is switchable between a first mode and a second mode.

[0062] (First mode) In the first mode, the feedback controller 220 operates based on the first pulse PWMA.

[0063] In the first mode, the digital compensator 224 converts the error signal D captured by the A / D converter 222 at the timing of the negative edge of the first pulse PWMA. ERR is used as an error signal in the timing of the positive edge of the second pulse PWMB.

[0064] In the first mode, the digital compensator 224 converts the error signal D captured by the A / D converter 222 at the timing of the positive edge of the first pulse PWMA. ERR The error signal D at the timing of the negative edge of the second pulse PWMB ERR Use as.

[0065] (Second mode) In the second mode, the feedback controller 220 operates based on the second pulse PWMB.

[0066] In the second mode, the digital compensator 224 converts the error signal D captured by the A / D converter 222 at the timing of the positive edge of the second pulse PWMB into ERR The error signal D at the timing of the negative edge of the first pulse PWMA ERR Use as.

[0067] In the second mode, the digital compensator 224 uses the error signal D captured by the A / D converter 222 at the timing of the negative edge of the second pulse PWMB ERR as the error signal D at the timing of the positive edge of the first pulse PWMA ERR .

[0068] The above is the configuration of the positioning device 100. Next, its operation will be described. FIG. 3 is a diagram showing the input / output characteristics of the motor driver circuit 200 in FIG. 2. By the feedback control by the digital compensator 224, feedback is applied so that the error between the current feedback signal V <000...​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​The error signal D is output data from the A / D converter 222 and is captured at the timing of the negative edge of the first pulse PWMA. ERR is expressed as Ax, and the error signal D captured at the timing of the positive edge of the first pulse PWMA ERR is denoted as Bx.

[0072] The error signal D, which is output data from the A / D converter 222 and is captured at the timing of the positive edge of the second pulse PWMB, ERR is expressed as Cx, and the error signal D captured at the timing of the negative edge of the second pulse PWMB ERR is expressed as Dx, where x represents the PWM cycle.

[0073] 4 shows data referenced by the digital compensator 224. In the first mode, the error signal Ax captured at the timing of the negative edge of the first pulse PWMA is used as the error signal Ax' at the timing of the positive edge of the second pulse PWMB.

[0074] In the first mode, the error signal Bx captured at the timing of the positive edge of the first pulse PWMA is used as the error signal Bx' at the timing of the negative edge of the second pulse PWMB.

[0075] The above is the operation of the first mode.

[0076] In a system that uses PWM drive and detects current using a sense resistor Rs connected in series with the motor, the sense resistor Rs introduces asymmetry into the output stage. Specifically, the AC-CMRR differs when the A-phase output transitions and when the B-phase output transitions, resulting in errors in current detection. Therefore, by copying the error signals Ax and Bx acquired using the transition of the first pulse PWMA as a trigger and using these as error signals Ax' and Bx' when the second pulse PWMB transitions, the effect of the difference in AC CMRR between the A-phase output and the B-phase output can be reduced, improving current detection accuracy.

[0077] The first driver 262 generates a first driving voltage V OUTA Therefore, the first driving voltage V OUTA is delayed with respect to the first pulse PWMA. In other words, the first pulse PWMA is delayed by the first driving voltage V OUTA Therefore, the sampling timing based on the negative edge of the first pulse PWMA precedes the first driving voltage V OUTA occurs before the high-to-low transition of the first drive voltage V OUTA Similarly, the sampling timing based on the positive edge of the first pulse PWMA is OUTA Since the data Bx also occurs before the low-to-high transition of the first drive voltage V OUTA Since it is not affected by the transition of

[0078] Next, the second mode will be described.

[0079] 5 is an operation waveform diagram of the second mode of the motor driver circuit 200. In the second mode, the error signal Cx acquired at the timing of the positive edge of the second pulse PWMB is used as the error signal Cx' at the timing of the negative edge of the first pulse PWMA.

[0080] In the second mode, the error signal Dx captured at the timing of the negative edge of the second pulse PWMB is used as the error signal Dx' at the timing of the positive edge of the first pulse PWMA.

[0081] This is the operation of the second mode. As shown in FIG. 5, when the low period of the first pulse PWMA becomes shorter, the timing of the positive edge of the first pulse PWMA becomes shorter than the timing of the first driving voltage V OUTA In this case, when operating in the first mode, the current detection result B1 at the timing of the positive edge of the first pulse PWMA is close to the falling edge of the first drive voltage V OUTAIn such a case, the current detection accuracy is reduced by selecting the second mode. Specifically, the timing of the positive edge of the second pulse PWMB is affected by the transition of the negative edge of the first drive voltage V that precedes it. OUTA Since the current detection result of C1 is sufficiently far from the positive edge transition of

[0082] The timing of the negative edge of the second pulse PWMB is determined by the second drive voltage V OUTB where the second drive voltage V OUTB The effect of the transition of the first drive voltage V OUTA Since the transition of the negative edge of the second pulse PWMB is sufficiently small compared to the transition of the negative edge of the second pulse PWMB, the current detection result D1 of the negative edge of the second pulse PWMB can also be said to be highly accurate.

[0083] For example, the voltage command value D CTRL is greater than a predetermined threshold, the second mode is selected, and the voltage command value D CTRL When is smaller than a predetermined threshold, the first mode is selected, thereby enabling accurate current detection at all times.

[0084] Next, configuration examples of the current sense amplifier 250 and the error detection amplifier 230 will be described.

[0085] FIG. 6 is a circuit diagram showing an example of the configuration of the current sense amplifier 250 and the error detection amplifier 230. As shown in FIG.

[0086] The sense resistor Rs is driven by the drive current I DRV A voltage drop proportional to the voltage drop V across the sense resistor Rs occurs between the current sense pins ISNS and KSNS(AOUT) of the motor driver circuit 200. CS is fed back. V CS =R S ×I DRV

[0087] The current sense amplifier 250 detects the voltage VCS It varies linearly with V CS =0 (i.e. I DRV =0) when the predetermined level V CMREF The current feedback signal V FB Generate.

[0088] The current sense amplifier 250 includes a first operational amplifier OA1, a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4.

[0089] The first resistor R1 is connected between the inverting input (-) of the first operational amplifier OA1 and one end (ISNS pin) of the sense resistor Rs. The second resistor R2 is connected between the inverting input (-) of the first operational amplifier OA1 and the output of the first operational amplifier OA1. The third resistor R3 is connected between the non-inverting input (+) of the first operational amplifier OA1 and the other end (KSNS pin) of the sense resistor Rs. The fourth resistor R4 has one end connected to a predetermined level of voltage V CMREF The other end is connected to the non-inverting input (+) of the first operational amplifier OA1. FB is dependent on the output voltage of the first operational amplifier OA1.

[0090] When R1=R3 and R2=R4, the following equation holds true: V FB =R2 / R1×V CS +V CMREF

[0091] The error detection amplifier 230 includes a first input node n1, a second input node n2, an output node n3, a second operational amplifier OA2, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, and a capacitor C1. The first input node n1 receives a current feedback signal V FB is input to the second input node n2, and an analog command signal V DAC is entered.

[0092] The second operational amplifier OA2, the fifth resistor R5, the sixth resistor R6, and the seventh resistor R7 form a summing amplifier. The second operational amplifier OA2 has a reference voltage V CMREFThe fifth resistor R5 is connected between the inverting input (-) of the second operational amplifier OA2 and the first input node n1. The sixth resistor R6 is connected between the inverting input (-) of the second operational amplifier OA2 and the second input node n2. The voltage command signal V EAOUT may respond to the voltage at the output of the second operational amplifier OA2. A seventh resistor R7 is connected between the inverting input (-) of the second operational amplifier OA2 and its output.

[0093] Feedback voltage V FB The gain g of the summing circuit for is R7 / R5.

[0094] An eighth resistor R8 is connected between the output of the second operational amplifier OA2 and the output node n3 of the error detection amplifier 230. A capacitor C1 is connected to the output node n3. The eighth resistor R8 and the capacitor C1 form a low-pass filter. This low-pass filter functions as an anti-aliasing filter for the A / D converter 222 in the subsequent stage.

[0095] The above is an example of the configuration of the current sense amplifier 250 and the error detection amplifier 230.

[0096] 7 is a circuit diagram of a motor driver circuit 200A according to another embodiment. A current command generating unit 210A generates a target code (digital command value) D REF to the feedback controller 220A. The A / D converter 222 of the feedback controller 220A outputs the current feedback signal V FB The digital feedback value D FB The error detector 232 is a subtractor that converts the digital feedback value D FB and target code D REF Error D ERR The rest is the same as in Figure 2.

[0097] According to the motor driver circuit 200A of FIG. 7, the same effects as those of the motor driver circuit 200 of FIG. 2 can be obtained.

[0098] The motor driver circuit 200 in Fig. 2 has advantages over the motor driver circuit 200A in Fig. 7. These advantages will be described below.

[0099] In the motor driver circuit 200A of FIG. 7, the current feedback signal V FB In the steady state where the feedback loop is stabilized, the error D ERR is zero, so D REF =D FB In other words, the digital command value D REF When you change the value of FB The current feedback signal V, which is the input of the A / D converter 222, is FB That is, in the motor driver circuit 200A of FIG. 7, the digital command value D REF In response to changes in FB Therefore, it is necessary to select a high-bit A / D converter 222.

[0100] The advantages of the motor driver circuit 200 in FIG. 2 over the motor driver circuit 200A in FIG. 7 will be described. In the motor driver circuit 200 in FIG. 2, attention is focused on the input of the A / D converter 222. The input of the A / D converter 222 is an analog error signal V ERR In the steady state where the feedback loop is stabilized, the drive current I DRV Target Level I REF Regardless of the analog command signal V DAC Regardless of the magnitude of the analog error signal V ERR is substantially zero. Therefore, the fluctuation range of the input voltage of the A / D converter 222 is narrower than in the case of FIG. 7. This makes it possible to use an A / D converter 222 with fewer bits than the A / D converter 222 of FIG. 7. By using a lower-bit A / D converter 222, the chip cost and power consumption of the motor driver circuit 200 can be reduced.

[0101] In addition, in the motor driver circuit 200, the gain of the error detection amplifier 230 can be increased because, regardless of the gain, in the steady state, the error signal V ERR , that is, the input of the A / D converter 222 takes on a voltage level corresponding to zero. Increasing the gain of the error detection amplifier 230 has the same effect as increasing the number of bits (resolution) of the A / D converter 222. Therefore, for this reason as well, the motor driver circuit 200 can reduce the number of bits of the A / D converter 222.

[0102] For example, if a 16-bit A / D converter 222 is required in the motor driver circuit 200A of Fig. 7, the number of bits of the A / D converter 222 can be reduced to 12 bits in the motor driver circuit 200 of Fig. 2. A SAR (successive approximation) DAC can be used as the low-bit A / D converter 222, but other formats may also be adopted.

[0103] 8 is a circuit diagram of a motor driver circuit 200B according to another embodiment. In the motor driver circuit 200B, a pulse width modulator 240B is configured as a digital circuit, and the D / A converter 226 is omitted from the feedback controller 220B.

[0104] According to the motor driver circuit 200B of FIG. 8, the same effects as those of the motor driver circuit 200 of FIG. 2 can be obtained.

[0105] (Application) 9 is a diagram showing a hard disk drive 900 equipped with a motor driver circuit 200. The hard disk drive 900 includes a platter 902, a swing arm 904, a head 906, a spindle motor 910, a seek motor 912, and a motor driver circuit 920. The motor driver circuit 920 drives the spindle motor 910 and the seek motor 912.

[0106] The seek motor 912 is a voice coil motor. The motor driver circuit 200 (or 200A) according to the embodiment is built into a motor driver circuit 920, and drives the seek motor 912. The seek motor 912 positions the head 906 via the swing arm 904.

[0107] In this disclosure, the configuration or type of the linear motor to be driven is not particularly limited. For example, this disclosure can also be applied to driving a spring-return voice coil motor or other linear actuator. Alternatively, the motor to be driven may be a spindle motor.

[0108] The application of the positioning device 100 is not limited to hard disk drives, and it can also be applied to a positioning mechanism for a camera lens, etc. [Explanation of symbols]

[0109] 100 Positioning device 102 Linear motor 104 Upper controller 200 Motor driver circuit 210 Current command generation section 212 Interface Circuit 214 Logic Circuits 216 D / A converter 220 Feedback Controller 222 A / D converter 224 Digital Compensator 226 D / A converter 230 Error Detection Amplifier 240 Pulse Width Modulator 250 Current Sense Amplifier 260 output stage 262 1st Driver 264 Second Driver R1 First resistor R2 2nd resistor R3 3rd resistor R4 4th resistor R5 5th resistor R6 6th resistor R7 7th resistor R8 8th resistor OA1 operational amplifier OA2 Op Amp

Claims

1. a first output terminal to be connected to a first end of a motor to be driven via a sense resistor; a second output terminal to be connected to a second end of the motor; an error detector that generates an error signal based on an error between a current feedback signal based on a voltage drop across the sense resistor and a reference signal; an A / D converter that converts the error signal into a digital signal and captures it; a compensator that generates a voltage command value based on the error signal captured by the A / D converter; a D / A converter for converting the voltage command value into an analog control signal; a pulse width modulator that compares the analog control signal with a first triangular wave to generate a first pulse, and compares the analog control signal with a second triangular wave that is out of phase with the first triangular wave to generate a second pulse; an output stage that generates a first drive voltage at the first output terminal in response to the first pulse and generates a second drive voltage at the second output terminal in response to the second pulse; Equipped with In a first mode, the compensator uses the error signal captured by the A / D converter at the timing of the negative edge of the first pulse as the error signal at the timing of the positive edge of the second pulse.

2. 2. The motor driver circuit according to claim 1, wherein in the first mode, the compensator uses the error signal captured by the A / D converter at the timing of the positive edge of the first pulse as the error signal at the timing of the negative edge of the second pulse.

3. 3. The motor driver circuit according to claim 1, wherein in the second mode, the compensator uses the error signal captured by the A / D converter at the timing of the positive edge of the second pulse as the error signal at the timing of the negative edge of the first pulse.

4. 4. The motor driver circuit according to claim 3, wherein in the second mode, the compensator uses the error signal captured by the A / D converter at the timing of the negative edge of the second pulse as the error signal at the timing of the positive edge of the first pulse.

5. 5. The motor driver circuit according to claim 3, wherein the first mode and the second mode are switchable in accordance with the voltage command value.

6. a first output terminal to be connected to a first end of a motor to be driven via a sense resistor; a second output terminal to be connected to a second end of the motor; a current sense amplifier that generates a current feedback signal based on the voltage drop across the sense resistor; a feedback controller that generates a voltage command value so that the current feedback signal approaches a reference signal; a pulse width modulator that generates a first pulse and a second pulse having complementary duty cycles according to the voltage command value, the first pulse and the second pulse having a center of a high section of the first pulse aligned with a center of a high section of the second pulse; an output stage that generates a first drive voltage at the first output terminal in response to the first pulse and generates a second drive voltage at the second output terminal in response to the second pulse; Equipped with The feedback controller an A / D converter that converts an analog signal corresponding to the current feedback signal into a digital signal and takes it in; a digital circuit that processes the digital signal and generates the voltage command value; Including, In a first mode, the digital circuit uses the digital signal captured by the A / D converter at the timing of the negative edge of the first pulse as the digital signal at the timing of the positive edge of the second pulse.

7. 7. The motor driver circuit according to claim 6, wherein in the first mode, the digital circuit uses the digital signal captured by the A / D converter at the timing of the positive edge of the first pulse as the digital signal at the timing of the negative edge of the second pulse.

8. 8. The motor driver circuit according to claim 6, wherein in the second mode, the digital circuit uses the digital signal captured by the A / D converter at the timing of the positive edge of the second pulse as the digital signal at the timing of the negative edge of the first pulse.

9. 9. The motor driver circuit according to claim 8, wherein in the second mode, the digital circuit uses the digital signal captured by the A / D converter at the timing of the negative edge of the second pulse as the digital signal at the timing of the positive edge of the first pulse.

10. 10. The motor driver circuit according to claim 8, wherein the first mode and the second mode are switchable in accordance with the voltage command value.

11. 11. The motor driver circuit according to claim 1, wherein the motor is a linear motor.

12. The motor driver circuit of claim 11, wherein the linear motor is a voice coil motor.

13. 13. The motor driver circuit according to claim 1, which is monolithically integrated on a single semiconductor substrate.

14. A linear motor; a motor driver circuit according to any one of claims 1 to 13 for driving the linear motor; A positioning device comprising:

15. A hard disk drive comprising the positioning device according to claim 14.

16. A method for driving a motor, comprising: connecting a sense resistor in series with a first end of the motor; generating a current feedback signal based on a voltage drop across the sense resistor; generating an error signal responsive to an error between the current feedback signal and a reference signal; an A / D converter converting the error signal into a digital signal and capturing the digital signal; generating a voltage command value according to the digital signal; converting the voltage command value into an analog control signal; generating a first pulse by comparing the analog control signal with a first triangular wave, and generating a second pulse by comparing the analog control signal with a second triangular wave that is out of phase with the first triangular wave; applying a first drive voltage corresponding to the first pulse and a second drive voltage corresponding to the second pulse to the motor; Equipped with a driving method in which, in a first mode, the step of generating the voltage command value uses the digital signal captured by the A / D converter at the timing of the negative edge of the first pulse as the digital signal at the timing of the positive edge of the second pulse.

17. A method for driving a motor, comprising: connecting a sense resistor in series with a first end of the motor; generating a current feedback signal based on a voltage drop across the sense resistor; generating a voltage command value so that the current feedback signal approaches a reference signal; generating a first pulse and a second pulse having complementary duty cycles according to the voltage command value, wherein a center of a high section of the first pulse and a center of a high section of the second pulse are aligned; applying a first drive voltage corresponding to the first pulse and a second drive voltage corresponding to the second pulse to the motor; Equipped with The step of generating a voltage command value includes: an A / D converter converting an analog signal corresponding to the current feedback signal into a digital signal and acquiring the digital signal; processing the digital signal to generate the voltage command value; Including, a driving method in which, in a first mode, the step of generating the voltage command value uses the digital signal captured by the A / D converter at the timing of the negative edge of the first pulse as the digital signal at the timing of the positive edge of the second pulse.

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