Motor driver circuit for linear motor, positioning device using same, hard disk drive

Abstract

To provide a linear motor driving circuit in which noise can be suppressed.SOLUTION: A logic circuit 220 generates a second code y that linearly changes at an inclination (a) with respect to a first code x that is based on a position command POS of a linear motor 102 which is a driven target. The logic circuit 220 can change the inclination (a). A D / A converter 230 coverts the second code y to an analog control signal VDAC. A driving unit 240 drives the linear motor 102 so as to make a current detection signal VCS which indicates a driving current IDRV for the linear motor 102, close to a target value VREF which linearly changes at an inclination (g) with respect to the control signal VDAC. The driving unit 240 can change the inclination (g). If g=g1 and a=a1 are established in a first state, g=g2 (|g2|>|g1|) and a=a2=a1×(g1 / g2) are established in a second state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a driver circuit for a linear motor. [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] For example, in hard disk drives, a voice coil motor is used as the seek motor that positions the head, and in hard disk drives, it is necessary to suppress noise during reading and writing to the hard disk.

[0005] In applications where the drive circuit must supply a wide range of drive current to the voice coil motor, it is necessary to set the gain of the current detection in the feedback loop high. However, setting the gain high increases the problem of increased noise.

[0006] 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 drive circuit for a linear motor that can suppress noise. [Means for solving the problem]

[0007] One aspect of the present disclosure relates to a motor driver circuit for a linear motor. The motor driver circuit includes a logic circuit that generates a second code that changes linearly with a slope a relative to a first code based on a position command of a linear motor to be driven, the second code being switchable, a D / A converter that converts the second code into an analog control signal, and a current detection signal V that indicates a drive current for the linear motor. CS The target value V changes linearly with the control signal at a slope g. REF and a drive unit that drives the linear motor so that the gradient g approaches a gradient g that is switchable. The motor driver circuit is switchable between a first state and a second state, and in the first state, g = g1 and a = a1, and in the second state, g = g2 (where |g2| > |g1|) and a = a2 = a1 × (g1 / g2).

[0008] 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]

[0009] According to certain aspects of the present disclosure, noise can be suppressed. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram of a positioning device including a motor driver circuit according to the first embodiment. [Figure 2] FIG. 2 is a diagram showing the relationship between the first code x and the second code y in the first state and the second state. [Figure 3] FIG. 3 is a diagram showing input / output characteristics of the motor driver circuit of FIG. [Figure 4]FIG. 4 is a diagram illustrating the operation of the motor driver circuit according to the comparative technique. [Figure 5] FIG. 5 is a circuit diagram showing a specific example of the configuration of the motor driver circuit. [Figure 6] FIG. 6 is a block diagram of a positioning device including a motor driver circuit according to the second embodiment. [Figure 7] FIG. 7 is a time chart illustrating the operation of the motor driver circuit of FIG. [Figure 8] FIG. 8 is a circuit diagram showing a specific example of the configuration of the motor driver circuit. [Figure 9] FIG. 9 is a diagram illustrating the operation of the motor driver circuit of FIG. [Figure 10] FIG. 10 is a diagram showing a hard disk drive equipped with a motor driver circuit. DETAILED DESCRIPTION OF THE INVENTION

[0011] (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.

[0012] A motor driver circuit according to one embodiment includes a logic circuit that generates a second code that changes linearly with a slope a relative to a first code based on a position command for a linear motor to be driven, the second code being switchable with a slope a, a D / A converter that converts the second code into an analog control signal, and a current detection signal V that indicates a drive current for the linear motor. CSThe target value V changes linearly with the control signal at a slope g. REF and a drive unit that drives the linear motor so that the inclination g approaches a value of 1 / g2, and that is switchable between a first state and a second state, where in the first state g=g1 and a=a1, and in the second state g=g2 (where |g2|>|g1|) and a=a2=a1×(g1 / g2).

[0013] The slope g of the drive unit is the gain of the motor driver circuit. By changing the gain g between the first and second states and by changing the slope a of the logic circuit, the linear motor can be continuously controlled with respect to the first code. The gain g2 in the second state is relatively high, which widens the control range of the linear motor's drive current. In the first state, selecting a relatively low gain g1 suppresses noise. In other words, noise can be reduced within a certain current range while maintaining a wide current control range.

[0014] In one embodiment, the motor driver circuit may further include a sample-and-hold circuit connected between the D / A converter and the driver. When the slope a is changed, if the second code changes discontinuously, the control signal output from the D / A converter may overshoot or undershoot, potentially causing glitches in the drive current. By inserting a sample-and-hold circuit and fixing the input to the driver while the control signal is fluctuating, glitches in the drive current can be suppressed.

[0015] When switching from the first state to the second state, the value of the first code is x TH When a=a1, the logic circuit may gradually change the second code from the value when a=a1 to the value when a=a2. While the second code is gradually changing, the sample-and-hold circuit may supply the control signal sampled in the first state to the driver.

[0016] By gradually changing the second code and fixing the control signal using a sample-and-hold circuit during the change, and then switching the control signal to the correct voltage level simultaneously with gain switching after the change is complete, glitches in the drive current can be suppressed.

[0017] When switching from the second state to the first state, the value of the first code is x TH When a=a2, the logic circuit may gradually change the second code from the value when a=a2 to the value when a=a1. The sample-and-hold circuit may sample the control signal before the gradual change starts, and supply the sampled control signal to the driver while the second code is gradually changing. This makes it possible to suppress glitches in the drive current.

[0018] In one embodiment, the sample and hold circuit may include an input node connected to the D / A converter, an output node connected to the driver, a first switch connected between the input node and the output node, a capacitor with one end grounded, a second switch connected between the other end of the capacitor and the input node, a buffer that receives the voltage at the other end of the capacitor, and a third switch connected between the output of the buffer and the output node. The sample and hold circuit may be switchable between a tracking state in which the first switch and the second switch are on and the third switch is off, a hold state in which the first switch and the second switch are off and the third switch is on, and a through state in which the first switch is on and the second switch and the third switch are off.

[0019] In one embodiment, the sample and hold circuit may further be capable of switching between a through state in which the first switch is on and the second switch and the third switch are off.

[0020] In one embodiment, during a transition period between the first state and the second state, the sample and hold circuit may sample the control signal by transitioning from a tracking state to a through state. After the sampling operation of the sample and hold circuit is completed, the logic circuit gradually changes the second code, and when the gradual change of the second code is completed, the gain of the driver changes and the sample and hold circuit transitions to the through state, and then the sample and hold circuit transitions to the tracking state.

[0021] In one embodiment, the driver generates a current detection signal V CS is the target value V REF and an output stage that amplifies the voltage command signal and applies it to the linear motor.

[0022] In one embodiment, the feedback circuit is configured to generate a current sense signal V CS It varies linearly with V CS When V = 0, the predetermined level CMREF The input may include a current sense amplifier that generates a feedback signal such that:

[0023] In one embodiment, the motor driver circuit may further include a sense resistor provided on a path of a drive current of the linear motor. The current sense amplifier includes a first operational amplifier, a first resistor connected between an inverting input of the first operational amplifier and one end of the sense resistor, a second resistor connected between the inverting input of the first operational amplifier and the output of the first operational amplifier, a third resistor connected between a non-inverting input of the first operational amplifier and the other end of the sense resistor, and a voltage V CMREF and a fourth resistor receiving the feedback signal and having the other end connected to the non-inverting input of the first operational amplifier. The feedback signal may be responsive to the output voltage of the first operational amplifier.

[0024] In one embodiment, the feedback circuit may further include an error amplifier that outputs a voltage command signal so that the feedback signal approaches a target level based on the control signal.

[0025] In one embodiment, the error amplifier has a first input node receiving a feedback signal, a second input node receiving a control signal, an inverting input, and a predetermined level V CMREF The voltage command signal may include a second operational amplifier having a non-inverting input and an output for receiving the voltage command signal, a fifth resistor connected between the inverting input of the second operational amplifier and the first input node, and a sixth resistor connected between the inverting input of the second operational amplifier and the second input node. The voltage command signal may correspond to the voltage of the output of the second operational amplifier. The sixth resistor may be a variable resistor. The gain of the driver can be controlled according to the resistance value of the sixth resistor.

[0026] In one embodiment, the output stage may include a first amplifier that non-inverts and amplifies the voltage command signal, and a second amplifier that inverts and amplifies the voltage command signal.

[0027] In one embodiment, the linear motor may be a voice coil motor.

[0028] 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.

[0029] 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.

[0030] A hard disk drive according to one embodiment includes the above-described positioning device.

[0031] (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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 1 is a block diagram of a positioning device 100 including a motor driver circuit 200 according to embodiment 1. The positioning device 100 includes a linear motor 102, a host controller 104, and the motor driver circuit 200.

[0036] 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).

[0037] The motor driver circuit 200 receives the position control data POS and outputs a driving current I DRV is 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

[0038] 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 an interface circuit 210, a logic circuit 220, a D / A converter 230, and a drive unit 240, and is integrated on a single semiconductor substrate.

[0039] The interface circuit 210 is connected to the upper controller 104 and receives the position control data POS. 2 It may be a C (Inter IC) interface or an SPI (Serial Peripheral Interface).

[0040] The logic circuit 220 generates the first code x in accordance with the position control data POS. For example, when the position control data POS is changed, the logic circuit 220 gradually changes the first code x from a value based on the position control data POS before the change to a value based on the position control data POS after the change.

[0041] The logic circuit 220 generates a second code y that changes linearly with respect to the first code x at a gradient a. The logic circuit 220 is configured so that the gradient a can be switched between at least two values ​​a1 and a2. In general terms, y=ax+b …(1) where b is a constant.

[0042] The D / A converter 230 converts the second code y into an analog control signal V DAC For example, the D / A converter 230 includes a conversion unit 232 and a buffer (DAC amplifier) ​​234. The input / output characteristics of the D / A converter 230 are expressed by the following equations. V DAC =K DAC ·y …(2)

[0043] The driving unit 240 supplies the driving current I DRV The current detection signal V CS and the control signal V DAC Receives the current detection signal V CS is the drive current I DRV For example, the current detection signal V CS is the driving current I DRV is proportional to V CS =α I DRV …(3) The following relationship is assumed to hold.

[0044] The driver 240 generates a current detection signal V CS is the target value V REF The linear motor 102 is driven by feedback so that the current detection signal V CS The target value V REF is the control signal V DAC It changes linearly with a slope g against the current. CS The target value V REF and the control signal V DAC The following relationship holds between V REF =g×(V DAC -V0) …(4) V0 is the drive current I DRV The reference voltage V when becomes zero REF and is any constant including zero. g can be positive or negative.

[0045] The slope g is the gain of the driver 240 and can be switched between at least two values ​​g1 and g2. The gain g of the driver 240 is controlled by the logic circuit 220.

[0046] In other words, the feedback drives the current I DRV When is in regulation, V CS =V REF In other words, equations (3) and (4) are equal, so equation (5) holds. α·I DRV =g×(V DAC -V0) …(5)

[0047] Therefore, the drive current I DRV is expressed by equation (6), and the control signal V DAC It varies linearly with I DRV =g / α×(V DAC -V0) …(6) For example, V0 is the first code x with the center value x c When I DRV =0.

[0048] The motor driver circuit 200 is configured to be switchable between a first state φ1 and a second state φ2.

[0049] First state φ1 g=g1, a=a1

[0050] Second state φ2 g=g2 (where |g2|>|g1|) a=a2=a1×(g1 / g2) In other words, the product of g and a is equal in the first state φ1 and the second state φ2.

[0051] For example, the logic circuit 220 adaptively selects the first state φ1 and the second state φ2 according to the value of the first code x. That is, when the first code x is within a predetermined range, the first state φ1 is selected, and when the first code x is outside the predetermined range, the second state φ2 is selected. That is, the logic circuit 220 automatically selects the first state φ1 and the second state φ2 without external control. Here, the predetermined range is x a ~x b and it is assumed that x a <x<x b When, the first state φ1, x<x a or x b <x, the second state φ2 is selected.

[0052] Figure 2 is a diagram showing the relationship between the first code x and the second code y in the first state φ1 and the second state φ2. x a <x<x b In the first state φ1 where, the slope Δy / Δx = a1 of the second code y, and x<x a or x b <x, in the second state φ2, the slope Δy / Δx = a2 of the second code y.

[0053] The above is the configuration of the motor driver circuit 200. Next, its operation will be described.

[0054] (First state φ1) In the first state φ1, y = a1x …(1a) The relationship holds, and the control signal V DAC is V DAC [[ID=4​​​​​​​​​​​​​​​changes linearly with respect to the first code x, and its slope is ΔI DRV / Δx is ΔI DRV / Δx=g1 / α×K DAC a1…(7a) This becomes:

[0055] (Second state φ2) In the second state φ2, y=a2x …(1b) The relationship between the control signal V DAC teeth, V DAC =K DAC a2x …(2b) Substituting this into equation (6) together with g = g2 gives equation (6b). I DRV =g / α×(V DAC -V0)=g2 / α×(K DAC a2x-V0) …(6b) This is the input / output characteristic of the motor driver circuit 200 in the second state φ2, and the drive current I DRV changes linearly with respect to the first code x, and its slope is ΔI DRV / Δx is ΔI DRV / Δx=g2 / α×K DAC a2…(7b) This becomes:

[0056] As mentioned above, a2=a1×(g1 / g2) Substituting this into equation (7b), we get ΔI DRV / Δx=g2 / α×K DAC a1×(g1 / g2)=g1 / α×K DAC a1…(7b') This is consistent with the slope equation (7a) in the first state φ1.

[0057] 3 is a diagram showing the input / output characteristics of the motor driver circuit 200 of FIG. 1. Here, it is assumed that g is positive and V0 is positive in the drive unit 240. The gain g is switched between the first state φ1 and the second state φ2, and the slope a of the logic circuit 220 is switched so that the product of the gain g and the slope a is constant, whereby the first code x and the drive current I DRV In other words, when viewed from the upper controller 104, the input / output characteristics of the motor driver circuit 200 are the same.

[0058] In the first state φ1, a low value g1 is selected as the gain g of the driver 240, so that noise generated by the driver 240 can be suppressed. a ~x b The drive current I DRV Range-I TH ~+I TH In this case, a low gain g1 is selected to suppress noise.

[0059] The advantages of the motor driver circuit 200 become clear when compared with comparable technologies.

[0060] 4 is a diagram illustrating the operation of the motor driver circuit according to the comparative technique. In the comparative technique, a low gain g1 is set over the entire range, and the noise generated by the driving unit 240 can be kept low.

[0061] Here, when the gain g1 of the driver 240 is low, a large drive current I DRV In other words, when it is desired to widen the movable range of the linear motor 102, the control signal V DAC However, the voltage range that any signal can take in an analog circuit is limited to the power supply voltage V DD Therefore, in the region where the first code x is large, the control signal V DAC is clamped, the drive current I DRV The range of

[0062] In the embodiment, since the gain g2 is set high in the second state φ2, the drive current I DRV The maximum value of I MAX can be increased, and the drive current I DRV In the first state φ1, noise can be suppressed by selecting a relatively low gain g1. In other words, noise can be reduced within a certain current range while maintaining a wide current control range.

[0063] Next, a specific example of the configuration of the motor driver circuit 200 will be described.

[0064] The linear motor 102 and the current sense resistor Rs are connected in series between the output pins AOUT and BOUT of the motor driver circuit 200. S is the drive current I DRV A voltage drop proportional to the current sense resistor R is connected between the current sense pins ISNS and KSNS of the motor driver circuit 200. S The voltage drop on the CS is fed back as V CS =R S ×I DRV …(8)

[0065] The driver 240 includes a feedback circuit 250 and an output stage 260. The feedback circuit 250 outputs a current detection signal V CS is the target value V REF The voltage command signal V EAOUT The output stage 260 generates a voltage command signal V EAOUT is amplified and applied to the linear motor 102.

[0066] The feedback circuit 250 includes a current sense amplifier 252 and an error amplifier 254 .

[0067] The current sense amplifier 252 outputs the current detection signal VCS It varies linearly with V CS =0 (i.e. I DRV =0) when the predetermined level V CMREF The feedback signal V FB Generate.

[0068] The current sense amplifier 252 includes a first operational amplifier OA1, a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4.

[0069] The first resistor R1 is connected between the inverting input (-) of the first operational amplifier OA1 and one end (INS 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.

[0070] When R1=R3 and R2=R4, equation (9) holds. V FB =R2 / R1×V CS +V CMREF …(9)

[0071] The error amplifier 254 generates a feedback signal V FB is the control signal V DAC The voltage command signal V is adjusted to approach the target level based on EAOUT Output.

[0072] The error amplifier 254 includes a first input node n1, a second input node n2, a second operational amplifier OA2, a fifth resistor R5, and a sixth resistor R6. The first input node n1 receives a feedback signal V FB is input to the second input node n2, and a control signal V DAC The second operational amplifier OA2 has a reference voltage VCMREF A capacitor and resistor for phase compensation are connected between the inverting input (-, EIN pin) and output (EOUT pin) of the second operational amplifier OA2.

[0073] The 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.

[0074] The inverting input (-) of the error amplifier 254 is (R6·V FB +R5·V DAC ) / (R5+R6) Since virtual grounding is established in the steady state, the common voltage V of the non-inverting input (+) CMREF and we obtain equation (10). (R6·V FB +R5·V DAC ) / (R5+R6)=V CMREF …(10)

[0075] Therefore, in the steady state, equation (11) holds. V FB =-R5 / R6 V DAC +(R5 / R6+1)·V CMREF …(11)

[0076] Substituting equation (9) into equation (11), we get R2 / R1×V CS +V CMREF =-R5 / R6 V DAC +(R5 / R6+1)·V CMREF By transforming this, we obtain equation (12). V CS =-(R5 / R6)(R1 / R2) V DAC +(R5 / R6)·V CMREF =-(R5 / R6)(R1 / R2){V DAC -(R1 / R2) -1·V CMREF} …(12)

[0077] V in equation (4') REF is V CS Since the target value of is given, they are equal in the steady state, and therefore equation (12) and equation (4) are equal. Comparing equation (12) and equation (4), g=-(R5 / R6)(R1 / R2) V0=(R1 / R2) -1 V CMREF If R1=R2, we get the following equation: g=-(R5 / R6) V0=V CMREF

[0078] 5, the sixth resistor R6 is configured as a variable resistor, and the gain g of the driver 240 can be controlled according to the resistance value of the sixth resistor R6. The logic circuit 220 sets the resistance value of the sixth resistor R6 to a relatively high value R6_1 in the first state φ1, and sets the resistance value of the sixth resistor R6 to a relatively low value R6_2 in the second state φ2. Resistor values ​​R6_1 and R6_2 are R6_1=R5 / |g1| R6_2=R5 / |g2| It is sufficient to set it so that

[0079] The output stage 260 includes a first amplifier 262 and a second amplifier 264. The first amplifier 262 outputs a voltage command signal V EAOUT The second amplifier 264 non-inverts and amplifies the voltage command signal V EAOUT is inverted and amplified.

[0080] The first amplifier 262 includes a third operational amplifier OA3 and seventh to tenth resistors R7 to R10. The configuration of the first amplifier 262 is similar to that of the current sense amplifier 252. When R7=R9 and R8=R10, the output voltage V AOUT is expressed by equation (13). V AOUT =R8 / R7×(V EAOUT -VCMREF )+HVPWR …(13)

[0081] The second amplifier 264 includes a fourth operational amplifier OA4 and an eleventh resistor R11 to a fourteenth resistor R14. The configuration of the second amplifier 264 is similar to that of the current sense amplifier 252 and the first amplifier 262. When R11=R13 and R12=R14, the output voltage V of the second amplifier 264 is BOUT is expressed by equation (14). V BOUT =-R12 / R11×(V EAOUT -V CMREF )+HVPWR …(14) In addition, R8 / R7=R12 / R11 is satisfied.

[0082] The above is the configuration of the motor driver circuit 200. According to this motor driver circuit 200, noise is suppressed by lowering the gain g of the drive unit 240 in the first state φ1, and noise is suppressed by increasing the gain g of the drive unit 240 in the second state φ2. DRV The control range can be widened.

[0083] (Embodiment 2) 6 is a block diagram of a positioning device 100A including a motor driver circuit 200A according to embodiment 2. Differences between embodiment 2 and embodiment 1 will be described below.

[0084] The motor driver circuit 200A includes a sample-and-hold circuit 270 in addition to the components of the motor driver circuit 200 in FIG.

[0085] The sample-and-hold circuit 270 is connected between the D / A converter 230 and the driver 240. In the tracking state (through state), the sample-and-hold circuit 270 receives the control signal V DAC is output as it is, and the control signal V DAC is sampled, and in the hold state, the sampled control signal V DAC_SH The output of the sample and hold circuit 270 is V SHWhen written as V during tracking and sampling operation, SH =V DAC and in the hold state, V SH =V DAC_SH is.

[0086] The logic circuit 220 determines whether the first code x is equal to a predetermined value x TH When crossing the x axis, the first state φ1 switches to the second state φ2. TH is x a ,x b is equivalent to

[0087] In the first state φ1 and the second state φ2, the sample and hold circuit 270 is in a tracking state, and V SH =V DAC That is, the motor driver circuit 200A in the first state φ1 and the second state φ2 is equivalent to the motor driver circuit 200 in FIG.

[0088] The above is the configuration of the motor driver circuit 200A.

[0089] To clarify the advantages of the motor driver circuit 200A, a problem that may occur in the motor driver circuit 200 of FIG. 1 will be described.

[0090] 1, the D / A converter 230 includes a conversion unit 232 and a buffer 234. When switching between the first state φ1 and the second state φ2, if the second code y generated by the logic circuit 220 changes discontinuously, if the response speed of the buffer 234 is slow, the control signal V DAC Overshoot, undershoot, and ringing may occur in the control signal V DAC The overshoot, undershoot, and ringing of the drive current I DRV This appears as a glitch.

[0091] Taking this problem into consideration, the operation of the motor driver circuit 200A will be described.

[0092] 7 is a time chart illustrating the operation of the motor driver circuit 200A of FIG. TH When this occurs, the logic circuit 220 generates a trigger for a transition from the first state φ1 to the second state φ2.

[0093] The state before time t0 is the initial state, and the motor driver circuit 200A operates in the first state φ1. That is, the gain of the drive unit 240 is g1, and the slope of the logic circuit 220 is a1. The second code y is expressed as y=a1·x TH where b=0. When the logic circuit 220 transitions from the first state φ1 to the second state φ2, the second code y is calculated as a1·x TH From a2·x TH (time t1 to t2).

[0094] Prior to this gradual change period t1 to t2, the sample-and-hold circuit 270 calculates y=a1·x TH The control signal V DAC is sampled and held during the gradual change period t1 to t2.

[0095] At time t2 when the gradual change period ends, the sample-and-hold circuit 270 is switched from the hold state to the tracking state, and at the same time, the gain of the driver 240 is switched from g1 to g2.

[0096] The above is the transition from the first state φ1 to the second state φ2. Next, the transition from the second state φ2 to the first state φ1 will be explained.

[0097] Between times t2 and t3, the motor driver circuit 200A continues to operate in the second state φ2. During this time, the first code x takes a value according to the position control data POS, and the drive current I DRV also changes.

[0098] At time t3, the first code x reaches a predetermined value x TH When this happens, the logic circuit 220 generates a trigger for a transition from the second state φ2 to the first state φ1.

[0099] When the logic circuit 220 transitions from the second state φ2 to the first state φ1, the logic circuit 220 converts the second code y into a2·x TH From a1·x TH (time t4 to t5).

[0100] Prior to this gradual change period t4 to t5, the sample-and-hold circuit 270 calculates y=a2·x TH The control signal V DAC is sampled and held during the gradual change period t4 to t5.

[0101] At time t5 when the gradual change period ends, the sample and hold circuit 270 is switched from the hold state to the tracking state, and at the same time, the gain of the driver 240 is switched from g2 to g1.

[0102] The above is the transition from the second state φ2 to the first state φ1.

[0103] According to the motor driver circuit 200A, when switching from the first state φ1 to the second state φ2 and from the second state φ2 to the first state φ1, the driving current I DRV This can suppress glitches.

[0104] 8 is a circuit diagram showing a specific example of the configuration of the motor driver circuit 200 A. In the motor driver circuit 200 A, the configuration other than the sample-and-hold circuit 270 is the same as that in FIG.

[0105] The sample and hold circuit 270 includes a capacitor C1, a buffer 272, and first to third switches SW1 to SW3. An input node IN of the sample and hold circuit 270 is connected to the output of the D / A converter 230, and an output node OUT of the sample and hold circuit 270 is connected to the driver 240. The first switch SW1 is connected between the input node IN and the output node OUT. One end of the capacitor C1 is grounded. The second switch SW2 is connected between the other end of the capacitor C1 and the input node IN. The buffer 272 receives the voltage at the other end of the capacitor C1. The third switch SW3 is connected between the output of the buffer 272 and the output node OUT.

[0106] The sample and hold circuit 270 can be switched between the following three states. Tracking status First switch SW1: ON Second switch SW2: ON Third switch SW3: OFF Hold status First switch SW1: OFF Second switch SW2: OFF Third switch SW3: ON Through state First switch SW1: ON Second switch SW2: OFF Third switch SW3: OFF

[0107] The logic circuit 220 controls the state of the sample and hold circuit 270 by switching the first switch SW1 to the third switch SW3 on and off.

[0108] Next, the operation of the motor driver circuit 200A in FIG. 8 will be described.

[0109] 9 is a diagram illustrating the operation of the motor driver circuit 200A of FIG. 8. In FIG. 9, the control signal V DAC , the output voltage V of the buffer 272 BUF , the output voltage V of the sample-and-hold circuit 270 SH , drive current IDRV , the gain g of the driver 240, and the state of the sample and hold circuit 270 are shown.

[0110] Before time t0, the first state φ1 is reached. Similar to the situation in Figure 7, x = x TH Then, a transition trigger from the first state φ1 to the second state φ2 occurs at time t0. The period from time t0 to t2 is the transition period.

[0111] At time t0, the sample-and-hold circuit 270 transitions from the tracking state to the through state. DAC is sampled by the sample-and-hold circuit 270, and then goes into a hold state, and the sampled control signal V DAC Output.

[0112] After the sampling operation of the sample-and-hold circuit 270 is completed at time t1, the logic circuit 220 gradually changes the second code y. DAC At this time, the sample-and-hold circuit 270 is in a hold state, so the signal V input to the driver 240 SH is constant.

[0113] At time t2 after the gradual change of the second code y is completed, the gain of the driver 240 changes from g1 to g2, and the sample-and-hold circuit 270 transitions to the through state. This completes the transition to the second state φ2. Thereafter, at time t3, the sample-and-hold circuit 270 transitions to the tracking state to prepare for the next sampling operation.

[0114] The above is the operation of the motor driver circuit 200A.

[0115] (Application) 10 is a diagram showing a hard disk drive 900 equipped with a motor driver circuit 200. The hard disk drive 900 is equipped with 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.

[0116] The seek motor 912 is a voice coil motor. The motor driver circuit 200 (or 200A) according to the embodiment is built into the motor driver circuit 920 and drives the seek motor 912.

[0117] The seek motor 912 positions the head 906 via the swing arm 904. Low noise is required during the read and write periods of the hard disk, that is, when the head 906 is positioned in a specific area. Therefore, the seek motor 912 is set to a first state φ1 when the seek motor 912 is positioned such that the head 906 is positioned in a valid area on the platter 902, and set to a second state φ2 when the seek motor 912 is positioned such that the head 906 is positioned in any other area. a ,x b By specifying the above, it becomes possible to automatically suppress noise during reading and writing.

[0118] The embodiment has been described above. This embodiment is merely an example, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component and each treatment process, and that such modifications are also within the scope of the present invention. These modifications will be described below.

[0119] (Variation 1) The first state φ1 and the second state φ2 may be manually changeable from the outside in response to a command from the upper controller 104.

[0120] (Variation 2) When the position control data POS is changed by the upper controller 104, the logic circuit 220 may instantaneously change the value of the first code x without gradually changing it.

[0121] (Variation 3) In relation to the second embodiment, the configuration and operation of the sample and hold circuit 270 are not limited to those described above, and other types of sample and hold circuits or track and hold circuits may be used.

[0122] (Variation 4) In the second embodiment, the logic circuit 220 gradually changes the second code y, but this is not limitative and the second code y may be changed in multiple steps. TH and a2·x TH You can switch between them instantly.

[0123] (Variation 5) The configuration of the driver 240 is not limited to that shown in Figures 5 and 8. For example, the error amplifier 254 may have a positive gain. For example, the output stage 260 may be of a single-ended type instead of a differential type.

[0124] (Variation 6) The configuration and type of the linear motor to be driven are not particularly limited. For example, the present disclosure can be applied to driving a spring-return voice coil motor or other linear actuators.

[0125] (Variation 7) 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]

[0126] 100 Positioning device 102 Linear motor 104 Upper controller 200 Motor driver circuit 210 Interface Circuit 220 Logic Circuits 230 D / A converter 232 Conversion Unit 234 buffers 240 Drive Unit 250 Feedback Circuit 252 Current Sense Amplifier 254 Error Amplifier 260 output stage 262 First Amplifier 264 Second Amplifier 270 Sample and hold circuit 272 buffers C1 capacitor SW1 First switch SW2 Second switch SW3 Third switch R1 First resistor R2 2nd resistor R3 3rd resistor R4 4th resistor R5 5th resistor R6 6th resistor R7 7th resistor R8 8th resistor

Claims

1. a logic circuit that generates a second code that changes linearly with a gradient a relative to a first code based on a position command of a linear motor to be driven, the gradient a being switchable; a D / A converter for converting the second code into an analog control signal; A current detection signal V indicating the driving current of the linear motor ＣＳ is a target value V that changes linearly with the gain g in response to the control signal. ＲＥＦ a drive unit that drives the linear motor so that the gain g approaches and the first state and the second state are switchable; In the first state, g = g １ , a=a １ and In the second state, g = g ２ (However, |g ２ |>|g １ |), and a = a ２ = a １ × (g １ / g ２ ) and A motor driver circuit in which a predetermined range is defined for the first code in the logic circuit, and the first state is selected when the first code is within the predetermined range, and the second state is selected when the first code is outside the predetermined range.

2. The motor driver circuit of claim 1, wherein the logic circuit is defined with values ​​xa and xb that satisfy the relationship xa < xb, and selects the first state when the value x of the first code is xa < x < xb, and selects the second state when the value x of the first code is x < xa or xb < x.

3. 3. The motor driver circuit according to claim 1, further comprising a sample-and-hold circuit connected between the D / A converter and the drive unit.

4. When switching from the first state to the second state, the value of the first code is x ＴＨ When a=a, the logic circuit sets the second code as １ From the value when a = a ２ and gradually changes to the value when 4. The motor driver circuit according to claim 3, wherein, while the second code is being gradually changed, the control signal sampled by the sample-and-hold circuit before the second code is gradually changed is supplied to the drive unit.

5. When switching from the second state to the first state, the value of the first code is x ＴＨ When a=a, the logic circuit sets the second code as ２ From the value when a = a １ and gradually changes to the value when 4. The motor driver circuit according to claim 3, wherein the sample-and-hold circuit samples the control signal before the gradual change starts, and supplies the sampled control signal to the drive unit while the second code is gradually changing.

6. The sample and hold circuit an input node connected to the D / A converter; an output node connected to the driver; a first switch connected between the input node and the output node; a capacitor with one end grounded; a second switch connected between the other end of the capacitor and the input node; a buffer that receives the voltage at the other end of the capacitor; a third switch connected between the output of the buffer and the output node; Including, The sample and hold circuit a tracking state in which the first switch and the second switch are on and the third switch is off; 6. The motor driver circuit according to claim 3, wherein the motor driver circuit is switchable between a hold state in which the first switch and the second switch are off and the third switch is on.

7. The sample and hold circuit 7. The motor driver circuit according to claim 6, wherein a through state in which the first switch is on and the second switch and the third switch are off can be further switched.

8. During a transition period between the first state and the second state, the sample-and-hold circuit samples the control signal by transitioning from the tracking state to the through state; After the sample-and-hold circuit has completed the sampling operation, the logic circuit gradually changes the second code; When the gradual change of the second code is completed, the gain of the driver changes and the sample-and-hold circuit transitions to the through state; The motor driver circuit of claim 7 , wherein the sample and hold circuit then transitions to the tracking state.

9. The drive unit is The current detection signal V ＣＳ is the target value V ＲＥＦ a feedback circuit for generating a voltage command signal so as to approximate an output stage that amplifies the voltage command signal and applies it to the linear motor; 9. A motor driver circuit according to claim 1, comprising:

10. The feedback circuit comprises: The current detection signal V ＣＳ and V ＣＳ When V = 0, the predetermined level V ＣＭＲＥＦ 10. The motor driver circuit of claim 9, including a current sense amplifier that generates a feedback signal that is:

11. a sense resistor provided on a path of the drive current of the linear motor; The current sense amplifier A first operational amplifier; a first resistor connected between the inverting input of the first operational amplifier and one end of the sense resistor; a second resistor connected between the inverting input of the first operational amplifier and the output of the first operational amplifier; a third resistor connected between the non-inverting input of the first operational amplifier and the other end of the sense resistor; The predetermined level V ＣＭＲＥＦ a fourth resistor having the other end connected to the non-inverting input of the first operational amplifier; 11. The motor driver circuit of claim 10, comprising: a feedback signal responsive to an output voltage of the first operational amplifier.

12. The feedback circuit comprises:

12. The motor driver circuit according to claim 10, further comprising an error amplifier that outputs the voltage command signal so that the feedback signal approaches a target level based on the control signal.

13. The error amplifier a first input node for receiving the feedback signal; a second input node for receiving the control signal; Inverting input, the predetermined level V ＣＭＲＥＦ a second operational amplifier having a non-inverting input receiving the a fifth resistor connected between the inverting input of the second operational amplifier and the first input node; a sixth resistor connected between the inverting input of the second operational amplifier and the second input node; the voltage command signal is dependent on the voltage of the output of the second operational amplifier; 13. The motor driver circuit of claim 12, wherein the sixth resistor is a variable resistor.

14. The output stage comprises: a first amplifier that non-inverts and amplifies the voltage command signal; a second amplifier that inverts and amplifies the voltage command signal; 14. A motor driver circuit according to any one of claims 9 to 13, comprising:

15. 15. The motor driver circuit according to claim 1, wherein the linear motor is a voice coil motor.

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

17. A linear motor; a motor driver circuit according to any one of claims 1 to 16 for driving the linear motor; A positioning device comprising:

18. A hard disk drive comprising the positioning device according to claim 17.

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