JP2007096376A - Load drive method and load drive apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a load drive method and a load drive apparatus capable of reducing an input offset voltage for a dead band interval. <P>SOLUTION: The load drive method sets a drive signal and a negative feedback amount to zero, attaches an offset correction voltage for canceling the input offset voltage to a reference signal, and outputs the resulting signal, summates an increasing or decreasing offset correction voltage to/from the reference signal, compares an absolute value signal with nearly a minimum voltage of a triangle wave to detect the width of a dead band of input output characteristics, holds the offset correction voltage when an offset adjustment signal is set to a level equivalent to that of a midpoint of the dead band interval to perform driving, releases a state of setting the drive signal and the negative feedback amount to zero to perform ordinary driving. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a load driving method and a load driving device having an offset adjustment function for reducing an input offset voltage in a dead zone.

  In a recording / reproducing apparatus, a load driving apparatus with a pulse width modulation (PWM) output suitable for low power consumption is used for driving an actuator such as a thread or loading that drives an optical pick amplifier for accessing an optical disk in the radial direction of the recording medium. Is used. Furthermore, in order to define the initial position of the actuator, a dead zone where the output voltage is substantially zero is provided in the input / output characteristics of the load driving device.

FIG. 8 shows a conventional load driving device.
The load 29 representing the actuator energization circuit is connected to the output of the load driving device 100 and is operated based on signals input to the drive signal input terminal 21 and the reference signal input terminal 22.

  The load driving device 100 includes an input amplifier 23, an absolute value circuit 24, a pulse width modulation unit 25, a polarity determination unit 26, a triangular wave generation unit 27, a drive output circuit 28, a feedback amplifier 30, a filter 42, and an input resistor 43. Yes.

  The input amplifier 23 has a drive signal A1 shown in FIG. 9A applied to one input terminal IN1 from the drive signal input terminal 21 via the input resistor 43, and a reference signal input terminal 22 to the other input terminal IN2. A signal obtained by differentially amplifying the applied reference signal B1 is output. The output of the input amplifier 23 is connected to one input terminal of the pulse width modulation unit 25 via the absolute value circuit 24. A triangular wave D shown in FIG. 9B is applied from the triangular wave generator 27 to the other input terminal of the pulse width modulator 25. In order to provide a dead band in the input / output characteristics of the load driving device, the triangular wave D is raised from the reference voltage by the DC voltage Va.

  The output of the pulse width modulation unit 25 is connected to one input terminal of the drive output circuit 28. The other input terminal of the drive output circuit 28 is connected to the output terminal of the polarity determination unit 26. The polarity determination unit 26 has one input terminal connected to the drive signal input terminal 21 and the other input terminal connected to the reference signal input terminal 22, and is driven based on the polarity of the difference voltage between the drive signal A1 and the reference signal B1. A signal for switching the direction is output to the drive output circuit 28.

  The drive output circuit 28 generates a signal for driving the load 29 according to the output signal E of the pulse width modulation unit 25 and the output signal of the polarity determination unit 26, and outputs the signal to the load 29 and the feedback amplifier 30. The two output terminals of the drive output circuit 28 are connected to the load 29 and the input terminal of the feedback amplifier 30, respectively. The feedback amplifier 30 differentially amplifies the difference between the output signals of the drive output circuit 28, smooths the difference through the filter 42, and negatively feeds back to the one input terminal of the input amplifier 23. In the load driving device 100 configured as described above, the absolute value signal C shown in FIG. 9B is generated at the output of the absolute value circuit 24, and the output of the pulse width modulation unit 25 is shown in FIG. 9C. The signal E shown is generated. In the signal E, a section where the signal C is lower than the minimum voltage of the triangular wave signal D is a section of the dead zone.

The load driving circuit 100 configured as described above can set the frequency characteristic to be flat or an arbitrary frequency characteristic by adjusting the value of the filter 42.
JP-A-10-135802

  Although the dead zone is set as described above to stabilize the initial position of the control object, recently, with the increase in data recording density, the dead zone described above has been developed for the purpose of good linear input / output characteristics over a wide range. Is required to increase the input dynamic range.

  Furthermore, because of the input offset voltage of the entire system that is generated due to inconsistency of element characteristics in each block constituting the load driving circuit 100, even when the input signal is zero, the output offset voltage does not enter the dead zone. May end up. Therefore, it is necessary to reduce the input offset of the dead zone.

Here, the relationship between the offset voltage of each block in the load driving apparatus 100 and the output offset voltage of the entire system will be specifically described.
In FIG. 8, the amplification factor of the input amplifier 23 is H, the amplification factor obtained by combining the amplification factors of the pulse width modulation unit 25 and the drive output circuit 28 is J, and the amplification factor of the feedback amplifier 30 is multiplied by the resistance value of the filter 42. Assuming that K is K, the amplification factor G of the entire system is expressed by the following equation (1).

G = (H ・ J) / (1-H ・ K ・ J) (1)
Usually, in order to suppress variation, the value of H is increased and the value of K is sufficiently smaller than the value of H. In FIG. 8, the input offset voltage of the input amplifier 23 is a, the input offset voltage of the absolute value circuit 24 is c, the input offset voltage obtained by synthesizing the input offset voltages of the pulse width modulator 25 and the drive output circuit 28 is d, Assuming that the input offset voltage of the feedback amplifier 30 is b, the output offset voltage Vofs of the entire system is expressed by the following equation (2).

Vofs = [{(b · K + a) · H + (c + d)} · J] / (1−H · K · J) (2)
The input offset Vofsi is obtained by dividing equation (2) by equation (1).
Vofsi = (b · K + a) + {(c + d) / H} (3)
It becomes. Since c and d are divided by H, which is a large value, from Equation (3), there is little influence on the input offset voltage of the entire system. Therefore, the values of a and b dominate the input offset voltage. That is, in an apparatus such as an amplifier having an analog MOS configuration with a large mismatch in element characteristics, a, b, c, and d increase, and the input offset voltage of the entire system increases.

  Further, in order to correct the input offset voltage of the entire system to be small with respect to the pulse width modulation output of the load driving device, the output after passing through the LPF having a low offset voltage must be detected. However, it is difficult to detect the dead zone with high accuracy, such as detection of switching noise and ultrafine pulses. Therefore, it is difficult to accurately correct the value of the input offset voltage in the dead zone.

  An object of this invention is to provide the load drive method and load drive device which can reduce the input offset voltage of a dead zone area.

  According to a first aspect of the present invention, a signal obtained by converting a drive signal into an absolute value signal of a signal amplified by an input amplifier is used as a modulated signal, and a voltage corresponding to the dead band of the input / output characteristics is raised from the reference voltage. A pulse width modulation signal is generated from the pulse width modulation unit using the triangular wave as a modulation signal, and a first pulse width modulation signal PWM-modulated is applied to one end of the drive output circuit of the load based on the pulse width modulation signal, A load driving method in which a PWM-modulated second pulse width modulation signal is applied to the other end of the drive output circuit of the load, and the difference between the first and second pulse width modulation signals is negatively fed back. The signal and the negative feedback are set to zero, and an offset correction voltage that increases or decreases is added to the drive signal to detect the width of the dead zone of the input / output characteristics, and the off-state when the dead zone is set to the middle point. While operating Tsu preparative correction voltage holds, it characterized in that the normal operation by releasing the state of setting the drive signal and the negative feedback to zero.

  According to a second aspect of the present invention, a signal obtained by converting a drive signal into an absolute value signal of a signal amplified by an input amplifier is used as a modulated signal, and a voltage corresponding to the dead band of the input / output characteristics is raised from the reference voltage. A pulse width modulation signal is generated from the pulse width modulation unit using the triangular wave as a modulation signal, and a first pulse width modulation signal PWM-modulated is applied to one end of the drive output circuit of the load based on the pulse width modulation signal, A load driving device that applies a PWM-modulated second pulse width modulation signal to the other end of the drive output circuit of the load and negatively feeds back a difference between the first and second pulse width modulation signals. An offset adjustment signal adding section for adding an offset adjustment signal for detecting a voltage and an offset correction voltage for canceling the input offset voltage to the drive signal for output; and the drive signal An input amplifier input signal setting unit that switches the signal to zero, a feedback amplifier input signal setting unit that switches the negative feedback to zero setting, the absolute value signal and the substantially minimum voltage of the triangular wave are compared, and the drive signal is A dead zone determination unit that determines whether the zone is a dead zone, a counter that detects a dead zone width using an output signal of the dead zone determination unit and sets a midpoint of the dead zone, and the offset adjustment in the offset adjustment signal addition unit A clock generation unit that outputs a clock signal that is synchronized with a signal addition timing; and an offset adjustment signal addition unit that generates the offset adjustment signal and the offset correction voltage according to the clock signal and the output signal of the counter. And an offset control unit for outputting a control signal for setting the drive signal and the negative feedback to zero. An increase or decrease offset correction voltage is added to the drive signal to detect the width of the dead zone of the input / output characteristic, and the operation is performed while holding the offset correction voltage when the dead zone is set to the middle point. The signal and the negative feedback are set to zero and the normal operation is performed.

  The load driving device according to claim 3 of the present invention is the load driving device according to claim 2, wherein the triangular wave generating unit that generates the triangular wave uses the output signal of the clock generating unit to add the timing of adding the offset adjustment signal and the triangular wave signal. By outputting a triangular wave signal in synchronization with the timing at which the minimum voltage is reached, the dead zone determination unit is configured to compare the triangular wave signal with the absolute value signal at each timing at which the minimum voltage of the triangular wave signal is output. It is characterized by that.

  According to a fourth aspect of the present invention, there is provided the load driving device according to the second aspect, further comprising a storage unit that stores the offset correction voltage when the offset adjustment signal is set to the midpoint of the dead zone.

  According to a fifth aspect of the present invention, the load drive device according to the second aspect is characterized in that the offset adjustment signal adding unit includes at least one constant current source, at least one resistor, and at least one switch.

  According to a sixth aspect of the present invention, in the load driving device according to the second aspect, the offset adjustment signal adding unit receives one input terminal of the input amplifier that differentially amplifies the reference signal and the drive signal and the reference signal. It has at least 1 resistance arrange | positioned in series between a reference signal input terminal, and at least 1 current source for sending an electric current through the said resistance.

  According to a seventh aspect of the present invention, in the load driving device according to the second aspect, the offset adjustment signal adding unit receives one input terminal of an input amplifier that differentially amplifies the reference signal and the driving signal and the driving signal. It has at least 1 resistance arrange | positioned in series between a drive signal input terminal, and at least 1 current source for sending an electric current through the said resistance.

The load driving device according to an eighth aspect of the present invention is characterized in that, in the sixth or seventh aspect, a resistance value of the resistor or a current value flowing through the resistor is varied.
According to a ninth aspect of the present invention, the load driving method according to the first aspect includes the step of storing the offset correction signal in a storage unit.

  The load driving method according to claim 10 of the present invention is the load driving method according to claim 1, wherein the substantially minimum voltage of the triangular wave signal in the detection step uses the minimum voltage of the triangular signal synchronized with the frequency of the output signal of the clock generation unit. The offset correction voltage is sequentially added or subtracted for each minimum voltage of the triangular wave signal.

  The load driving method according to claim 11 of the present invention is the load driving method according to claim 1, wherein the detection of the dead band width of the output characteristic is performed by comparing the absolute value signal and the substantially minimum voltage of the triangular wave signal to detect the dead band width. The substantially minimum voltage of the triangular wave signal uses a reference voltage that generates the minimum voltage of the triangular wave generating unit, and the control step sequentially adds and controls in synchronization with the frequency of the output signal of the clock generating unit. .

A load driving method according to a twelfth aspect of the present invention is characterized in that, in the first aspect, the offset correction voltage is controlled so as to monotonously increase or monotonously decrease.
The load driving method according to claim 13 of the present invention is characterized in that, in claim 1, the offset correction voltage is controlled by a binary search method for searching for a target correction value while narrowing the search range by half.

  The load driving device of the present invention has an advantageous effect that it can provide a load driving device and a load driving method in which the dead zone input offset voltage is reduced, and when the input signal is zero, the dead zone can be entered and the output offset can be avoided. Play.

Hereinafter, the load driving method of the present invention will be described based on specific embodiments.
In addition, the same code | symbol is attached | subjected and demonstrated to what has the effect | action similar to FIG.

(Embodiment 1)
1 to 4 show (Embodiment 1) of the present invention.
FIG. 1 shows a load driving apparatus according to (Embodiment 1), which is configured by further adding an offset adjustment circuit 200 to the conventional load driving apparatus 100 shown in FIG. Since it has the same structure in the other points, redundant description is omitted. In this (Embodiment 1), the conventional load driving device 100 is referred to as a load driving unit 100A.

  The offset adjustment circuit 200 includes a dead zone determination unit 32, an offset control unit 34, an offset adjustment start signal input terminal 31, an offset adjustment signal addition unit 35, a clock generation unit 46, a counter unit 45, an input amplifier input signal setting unit 37, and a feedback amplifier. An input signal setting unit 38 and switches 40 and 41 are provided.

  The dead zone determination unit 32 connects one input terminal of the comparator to the output terminal of the absolute value circuit 24 via the switch 40 and connects the other input terminal V9 to the output terminal of the triangular wave generation unit 27 via the switch 41. Has been.

  The offset control unit 34 receives a timing instruction to start offset adjustment from the offset adjustment start signal input terminal 31, and receives a timing signal for offset adjustment from the clock generation unit 46. The offset adjustment signal is supplied to the offset adjustment signal adding unit 35, and the switching signal is supplied to the input amplifier input signal setting unit 37, the feedback amplifier input signal setting unit 38, and the switches 40 and 41, respectively.

  The offset adjustment signal adding unit 35 is provided between the reference signal input terminal 22 and the input terminal of the input amplifier 23. The offset adjustment signal from the offset control unit 34 is added to the reference signal B1 supplied from the reference signal input terminal 22. Are added and output.

  The input amplifier input signal setting unit 37 converts an input signal to the input resistor 43 on the load driving unit 100A side into a signal input state from the drive signal input terminal 21 and a signal input state from the reference signal input terminal 22. Switching is performed based on a switching signal from the offset control unit 34.

  The feedback amplifier input signal setting unit 38 includes switches 38a and 38b, and the input signal of the feedback amplifier 30 is in a state of supplying the output signal of the drive output circuit 28 and in a state of supplying the output of the fixed voltage source 38c. It is configured to be switchable.

Here, the principle of offset adjustment for reducing the input offset voltage of the entire system will be described in order to reduce the dead zone input offset in (Embodiment 1).
As an offset adjustment setting, the two input signals of the feedback amplifier 30 are set to the same potential, and the drive signal and the reference signal are set to the same potential.

  By setting the two input signals of the feedback amplifier 30 to the same potential, only one output offset voltage “b · K” of the feedback amplifier 30 is output to one input terminal IN1 of the input amplifier 23. Further, by making the drive signal and the reference signal have the same potential, the output offset voltage “b · K” of the feedback amplifier 30 and the input offset voltage “a” of the input amplifier 23 are summed at the output terminal of the input amplifier 23. A voltage obtained by multiplying the above by H is output. Further, at the output terminal of the absolute value circuit 24, the absolute value circuit 24 is further increased to a voltage obtained by multiplying the sum of the output offset voltage “b · K” of the feedback amplifier 30 and the input offset voltage “a” of the input amplifier 23 by H. Is added to the input offset voltage c.

Further, when divided by the gain of the input amplifier 23 and converted to the input offset voltage Vα, the voltage Vα is expressed by the following equation (4).
Vα = (b · K + a) + c / H (4)
That is, when the offset adjustment setting is performed, the output terminal of the absolute value circuit 24 includes the offset voltages of the input amplifier 23, the feedback amplifier 30, and the absolute value circuit 24 when the drive signal and the reference signal are at the same potential. You will have an input offset voltage.

  Next, when the offset correction voltage Vβ is added to the potential of the reference signal (drive signal) to change the value of the reference signal (drive signal), the input offset voltage Vofsi2 of the entire system is expressed by the following equation (5). .

Vofsi2 = (b · K + a) + {(c + d) / H} −Vβ (5)
The output signal of the absolute value circuit 24 adjusts Vβ so that when the drive signal and the reference signal are at the same potential, the signal for driving the load 29 matches the equivalent signal when located at the midpoint of the dead zone. That is, when Vβ is equal to Vα, the offset voltage of the input amplifier 23, the feedback amplifier 30, and the absolute value circuit 24 can be reduced.

The input offset Vofui3 of the entire system when Vβ = Vα is expressed by the following equation (6).
Vofsi3 = d / H (6)
Accordingly, the main offset factors “a” and “b” can be removed, so that the output offset voltage of the entire system can be reduced. That is, the input offset voltage in the dead zone can be reduced, and the output offset when the input signal is zero can be avoided.

Based on the principle of the offset adjustment described above, an offset correction voltage appropriate for removing the main offset factors a and b is detected.
The configuration of the offset adjustment circuit 200 will be described based on the operation.

FIG. 2 is a flowchart of offset adjustment in the load driving device of (Embodiment 1) of the present invention.
First, in step S <b> 1, an offset adjustment start signal is applied to the offset control unit 34 via the offset adjustment start signal input terminal 31. Although not shown, the offset adjustment start signal may be a signal linked to a standby release signal for enabling the load driving device or a signal linked to application of a power supply voltage. Further, it may be a command signal from a system outside the apparatus.

  In step S <b> 2, the offset control unit 34 switches the input amplifier input signal setting unit 37 to set the reference signal input terminal 22 and the input resistor 43 in order to make the drive signal input to the input amplifier 23 and the reference signal have the same potential. Short circuit. That is, the output signal of the input amplifier input signal setting unit 37 is set to the same potential as the signal input to the reference signal input terminal 22. At the same time, the offset control unit 34 switches the switches 38a and 38b of the feedback amplifier input signal setting unit 38 and connects to the fixed voltage source 38c in order to make the signals input to the two input terminals of the feedback amplifier 30 have the same potential. And give a fixed voltage equal to each other.

  Note that the value of the fixed voltage is preferably 1/0 of the average power supply voltage in consideration of the input voltage dependency of the feedback amplifier 30 because the drive output circuit 28 performs pulse width modulation driving from zero to the power supply voltage. The voltage is about 2.

  Next, in step S3, the offset control unit 34 outputs a control signal that causes the offset adjustment signal adding unit 35 to create an offset adjustment signal. Based on the control signal, the offset adjustment signal adding unit 35 creates an initial signal of the offset adjustment signal. As a result, a signal obtained by adding the initial signal of the offset adjustment signal to the reference signal is input to the other input terminal of the input amplifier 23. A reference signal is applied to one input terminal of the input amplifier 23 via an input resistor 43.

  After the initial signal is input to the input amplifier 23, the offset control unit 34 switches the switch 40 in step S4 to connect the output terminal of the absolute value circuit 24 and the input terminal of the dead zone determination unit 32. At the same time, the offset control unit 34 switches the switch 41 to connect the output terminal of the triangular wave generation unit 27 and the input terminal of the dead zone determination unit 32.

  In step S5, the offset control unit 34 operates the clock generation unit 46 to generate a control signal. The offset adjustment signal adding unit 35 sweeps the voltage range within the offset adjustment target by the control signal of the offset control unit 34, and creates an offset adjustment signal that increases the step from the negative minimum value or decreases the step from the positive maximum value.

  In step S <b> 6, the input amplifier 23 differentially amplifies and outputs the absolute value via the absolute value circuit 24, and outputs the absolute value to one input terminal of the dead zone determination unit 32. The triangular wave signal output from the triangular wave generating unit 27 is applied to the other input terminal of the dead band determining unit 32. The dead zone determination unit 32 detects the timing when the polarity of the difference voltage between the signals applied to both inputs changes, that is, when the dead zone is entered.

In step S7, the counter 45 starts counting the number of offset adjustment steps when the polarity of the output of the dead zone determination unit 32 changes.
In step S8, the polarity is further changed, that is, the timing of exiting from the dead zone is detected, and the counter 45 is stopped. The dead zone width can be detected by the number of steps counted by the counter 45. The counted value is shifted by 1 bit to make the dead band width ½. An offset adjustment signal that is ½ of the dead zone is held, and thereafter, the control signal change is not accepted. At this time, the offset adjustment signal generated by the offset adjustment signal adding unit 35 is set as an offset correction voltage based on the held control signal.

  In step S9, after the offset correction voltage is detected, the input amplifier input signal setting unit 37, the feedback amplifier input signal setting unit 38, and the switches 40 and 41 are restored. Thus, the offset adjustment operation is completed.

  By the offset adjustment described above, the offset voltage components of the input amplifier 23 and the feedback amplifier 30 can be reduced, the input offset voltage in the dead zone can be reduced, and after the offset adjustment, the load can be driven while the offset voltage is reduced.

  In the load driving device of this (Embodiment 1), during offset adjustment, the pulse width modulation unit 25, the polarity determination unit 26, the drive output circuit 28, and the feedback amplifier 30 that have little influence on the output offset voltage of the entire system are not used. . For this reason, the generation of a correction error due to noise mixing can be suppressed by stopping the pulse width modulation signal. Further, as described above, since the amplification factor H of the input amplifier 23 is a large value, the determination accuracy of the offset voltage is good. Furthermore, since the offset correction voltage is added to the reference signal, the frequency characteristics of the entire system are not affected.

FIG. 3 shows a waveform diagram of each signal of the offset adjustment circuit 200.
3A shows the output signal V10 of the dead zone determination unit 32, and FIG. 3B shows the output signal V8 of the absolute value circuit 34 and the output signal V9 of the triangular wave generation unit 27. FIG. 3C shows the offset adjustment signal V11 generated and output by the offset adjustment signal adding unit 35.

In order to facilitate the explanation, conditions are set as follows.
The dead zone determination unit 32 compares the minimum voltage of the triangular wave generation unit 27 with the output signal of the absolute value circuit 24, outputs an L level below the output signal of the triangular wave generation unit 27, and outputs an H level above. . Further, the offset adjustment signal is controlled so as to increase the voltage Vs for one step before the timing at which the triangular wave generator 27 reaches the minimum voltage. The timing to enter the dead zone is between “5 · Vs” and “6 · Vs”, and the timing to exit the dead zone is between “12 · Vs” and “13 · Vs”.

The operation will be described based on the above conditions.
A signal for starting offset adjustment is input to the offset control unit 34 via the offset adjustment start signal input terminal 31. When the offset adjustment start signal is input and 0 [s] (tb0 [s]), the offset signal outputs “1 · Vs”. When the triangular wave generating unit 27 outputs a minimum voltage at ta0 [s] and the triangular wave signal and the output of the absolute value circuit 24 are compared by the dead band determining unit 32 at the same timing, the level of the output signal of the triangular wave generating unit 27 is Since it is equal to or greater than the triangular wave signal, the dead zone determination unit 32 outputs an L level. Next, at tb1 [s], the offset adjustment signal increases by one step and outputs “2 · Vs”. When the triangular wave generator 27 outputs a minimum voltage at ta1 [s] and the triangular wave signal and the output of the absolute value circuit 24 are compared at the same timing by the dead band determining unit 32, similarly, tb2 [s] and ta2 [s] ], Tb3 [s], ta3 [s]... And the offset adjustment signal increase by one step, and then the triangular wave signal is output at the minimum value at the timing when the triangular wave generator 27 outputs the minimum value. The operation of comparing the absolute value signal to which the offset adjustment signal is added is repeated. The timing at which the polarity of the output signal of the dead zone determination unit 32 changes is “6 · Vs”, that is, a value increased by 5 steps, and the timing at which the polarity of the output signal of the dead zone determination unit 32 changes is “13 · Vs”, That is, the value is increased by 12 steps.

  As described above, the dead zone can be detected as “8 · Vs” which is 7 steps by the difference between 12 steps and 5 steps. Further, a 1-bit shift is performed, and ½ of the dead zone is held as three steps.

Next, the offset adjustment signal adding unit 35 will be described with reference to FIG.
4A to 4D show examples of the offset adjustment signal adding unit 35, respectively.
4A includes a resistor R, current sources I1 to I6, and switches S1 to S6. The resistor R is inserted in series between the reference signal input terminal 22 and the input terminal IN2 of the input amplifier 23. Each of the current sources I1, I2, and I3 has one end connected to the power supply and the other end connected between the resistor R and the input terminal IN2 of the input amplifier 23 via the switches S1, S2, and S3. Each of the current sources I4, I5 and I6 has one end connected to the GND and the other end connected to the input terminal IN2 of the input amplifier 23 via the switches S4, S5 and S6. The offset adjustment signal adding unit 35 controls the total current of the current sources I1 to I3 by switching the switches S1 to S3. By flowing the total current through the resistor R, a positive offset adjustment signal (offset correction voltage) can be added to the reference signal applied from the reference signal input terminal 22. In addition, the switches S4 to S6 are controlled to control the total current of the current sources I4 to I6. By flowing the total current through the resistor R, a negative offset adjustment signal (offset correction voltage) can be added to the reference signal.

  Preferably, the current values of the current sources I1 to I6 are equal to each other and the current value for one step. If it does so, what is necessary is just to control the electric current amount of one current source for every step, and control of a total electric current amount does not become complicated. Alternatively, the current value is weighted to 2 to the nth power of 1 time, 2 times, and 4 times the current value for one step. By doing so, the amount of current can be changed in various ways by combining several current sources, so that the number of current sources and the number of switches can be reduced.

  4B has resistors R1 to R3, current sources I7 and I8, and switches S7 to S8. The resistors R1 to R3 are connected in series between the reference signal input terminal 22 and the input terminal IN2 of the input amplifier 23, respectively. The switches S11 to S13 are connected in parallel with the resistors R1, R2, and R3, respectively. Each of the current sources I7 has one end connected to the power supply and the other end connected between the resistor R3 and the input terminal IN2 of the input amplifier 23 via the switch S7. One end of the current source I8 is connected to the GND, and the other end is connected between the resistor R3 and the input terminal IN2 of the input amplifier 23 via the switch S8.

  The offset adjustment signal adding unit 35 controls the combined resistance of the resistors R1 to R3 by switching the switches S11 to S13. A positive offset adjustment signal (offset correction voltage) can be added to the reference signal by passing a current from the current source I7 through the combined resistor. In addition, a negative offset adjustment signal (offset correction voltage) can be added to the reference signal by passing a current from the current source I8 through the combined resistor.

  Preferably, the resistance values of the resistors R1 to R3 are equal to each other and have a resistance value for one step. Then, if one resistance value is short-circuited with a switch for each step, [the combined resistance can be controlled, and the control of the total resistance is not complicated. Alternatively, the resistance value is weighted to a power of 2 that is 1 times, 2 times, and 4 times the resistance value for one step. By doing so, the combined resistance can be varied in various ways by combining several resistors, so that the number of resistors and the number of switches can be reduced.

  The offset adjustment signal adding unit 35 in FIG. 4C includes resistors R4 to R9, current sources I9 and I10, switches S9 and S10, and switches S14 to S20. The current source I9 has one end connected to the power supply and the other end connected to the reference signal input terminal 22 via the switch S9 and resistors R4 to R6. The current source I10 has one end connected to the GND and the other end connected to the reference signal input terminal 22 via the switch S10 and resistors R7 to R9. The switches S14 to S20 are connected between the resistance ends of the resistors R4 to R9 and the input terminal IN2 of the input amplifier 23, respectively.

  The offset adjustment signal adding unit 35 controls the combined resistance of the resistors R4 to R6 and the resistors R7 to R9 by switching the switches S14 to S20. A positive offset adjustment signal (offset correction voltage) can be added to the reference signal by flowing a current from the current source I9 to the combined resistor. In addition, a negative offset adjustment signal (offset correction voltage) can be added to the reference signal by passing a current from the current source I10 through the combined resistor.

  Note that, similarly to the offset adjustment adding unit 35 illustrated in FIG. 4B, the resistance values of the resistors R4 to R9 are preferably equal to each other and the resistance value for one step. If it does so, if one resistance value is short-circuited with a switch for every step, control of synthetic | combination resistance can be performed and control of total resistance will not become complicated. Alternatively, the resistance value is weighted to a power of 2 that is 1 times, 2 times, or 4 times the resistance value for one step. By doing so, the combined resistance can be varied in various ways by combining several resistors, so that the number of resistors and the number of switches can be reduced.

  In the case of the offset adjustment signal adding unit 35 of FIG. 4D, it is effective when there are a plurality of load driving units 100A, and the switches S14 ′ to S20 are further added to the offset adjustment signal adding unit 35 shown in FIG. 'Is added. The switches S14 'to S20' are connected between the respective resistance ends of the resistors R4 to R9 and the input terminal IN2 (shown as IN2 'in FIG. 4) of the input amplifier 23 of another load driving unit 100A. The offset adjustment signal adding unit 35 configured as described above can obtain two outputs for operating the two load driving units 100A. Similarly, according to the desired number of load driving units 100A, if a switch is connected between each resistance end of resistors R4 to R9 and the input terminal of the input amplifier of each load driving unit 100A, a predetermined number of load driving units are provided. Unit 100A can be operated simultaneously.

  4A to 4D, the number of resistors and current sources of each offset adjustment signal adding unit is the offset correction voltage (± ((b XK + a) + c / H)) is the number that can form a total current amount equal to or greater than the value obtained by adding the dead band width.

  Each switch of the offset adjustment signal adding unit 35 may use a zener zap, a fuse, an antifuse, or a PROM as a trimming element. In this case, the offset adjustment is performed only once, and the offset correction voltage obtained thereby is corrected over a long period of time. If such a trimming method is used, the offset adjustment time during driving of the load driving device can be omitted. Further, the offset adjustment for permanently correcting the offset correction voltage may be performed by the customer as a system including the load driving device, or may be corrected at the time of inspection using only the load driving device.

  In the offset adjustment of (Embodiment 1), the offset adjustment signal is added to the reference signal, but the offset adjustment signal may be added to the drive signal. In that case, the offset adjustment signal added to the reference signal may be added to the drive signal with the sign reversed.

  The input amplifier input signal setting unit 37 is not limited to the above configuration, and may be any configuration as long as the drive signal input to the input amplifier 23 and the reference signal can have the same potential. The feedback amplifier input signal setting unit 38 is not limited to the above configuration, and may be any configuration that can set the input signal of the feedback amplifier 30 to the same potential.

  Since this load driving device does not perform pulse width modulation driving during the operation of detecting the offset correction voltage (offset adjustment), the intrusion of the offset correction error due to the pulse width modulation noise can be eliminated, and the offset voltage determination accuracy is improved. it can.

(Embodiment 2)
A load driving apparatus according to (Embodiment 2) of the present invention will be described with reference to FIG.
FIG. 5 shows the load driving device of (Embodiment 2), in which the offset adjustment circuit 200 is changed to an offset adjustment circuit 200A so that three load driving units 100A of (Embodiment 1) can be operated simultaneously. The load driving unit group 100B including the three load driving units 100A and the offset adjustment circuit 200A are provided. Here, the load 29 driven separately by each load driving unit 100A is a loading actuator, a thread actuator or the like in the recording / reproducing apparatus.

  The offset adjustment circuit 200A includes a dead zone determination unit 32, an offset adjustment signal addition unit 35, a feedback amplifier input signal setting unit 38, a drive signal input terminal 21, switches 40 and 41, and a counter of the offset adjustment circuit 200 according to the first embodiment. Instead of 45, the dead zone determination unit group 32A, the offset adjustment signal addition unit group 35A, the offset adjustment signal addition unit group 37A, the feedback amplifier input signal setting unit group 38A, the drive signal input terminal group 21A, the switch groups 40A and 41A, and the counter There are 45 groups.

  Each of the dead zone determination unit group 32A, the offset adjustment signal addition unit group 35A, the feedback amplifier input signal setting unit group 38A, the drive signal input terminal group 21A, and the switch groups 40A and 41A includes three dead zone determination units 32, The offset adjustment signal adding unit 35, three feedback amplifier input signal setting units 38, three drive signal input terminals 21, and three switches 40 and 41 are provided. The offset control unit 34 is commonly used for each element in each group.

  The load driving device of this (Embodiment 2) can be reduced by one offset adjustment even if the offset voltage value of the dead zone differs for each of the three load driving units 100A. Similarly, if the number corresponding to the load driving unit is provided as many as the dead zone determination unit 32, the offset adjustment signal addition unit 35, the feedback amplifier input signal setting unit 38, the drive signal input terminal 21, and the switches 40 and 41, The output offset voltage of the entire system of the plurality of load driving devices can be reduced by one offset adjustment. Furthermore, the time for offset adjustment can be shortened.

(Embodiment 3)
In (Embodiment 1), the output signal of the clock generator 46 is input to the triangular wave generator 27B of the load driver 100A. In the load driver of (Embodiment 3) shown in FIG. 6, the offset controller The only difference is that a reference signal for generating the minimum voltage used in the triangular wave generating unit 27B is used via the switch 41 for the other input terminal V9 of the dead band determining unit 32. About other points, it is the same as that of the load drive device of (Embodiment 1).

  6, the offset adjustment circuit 200B includes a clock generation unit 46, a dead zone determination unit 32, an offset control unit 34B, an offset adjustment signal addition unit 35, an input amplifier input signal setting unit 37, a feedback amplifier input signal setting unit 38, and a switch 40. 41 and a counter 45. The offset adjustment step of the offset adjustment circuit 200B is the same as in (Embodiment 1).

  An offset adjustment signal is applied via the offset adjustment start signal input terminal 31 and outputs a signal for controlling the switches 40 and 41 and a signal for causing the clock generator 46 to generate a clock signal. The clock generation unit 46 generates a clock signal that is a step interval of the offset adjustment signal generated by the offset adjustment signal addition unit 35. The input V9 of the dead zone determination unit 32 is set to a substantially minimum voltage of the triangular wave signal by connecting a signal for generating the minimum voltage used in the triangular wave generation unit 27.

  The load driving device of the third embodiment configured in this manner stably uses the minimum voltage of the triangular wave signal rather than the triangular wave signal that has a short minimum voltage section and may cause overshoot, and stably generates a dead band. It can be detected.

(Embodiment 4)
FIG. 7 shows the load driving device of (Embodiment 4).
This embodiment differs only in that an offset adjustment circuit 200E is provided instead of the offset adjustment circuit 200 of (Embodiment 1). The other points are the same as in (Embodiment 1).

  The offset adjustment circuit 200E includes a dead zone determination unit 32, an offset control unit 34E, an offset adjustment signal addition unit 35, an input amplifier input signal setting unit 37, a feedback amplifier input signal setting unit 38, a switch unit 39, switches 40 and 41, and a storage unit. 44, a counter 45, and a clock generator 46.

  The offset control unit 34E has its input terminal connected to the offset adjustment start signal input terminal 31. The offset control unit 34E is connected to the input amplifier input signal setting unit 37, the feedback amplifier input signal setting unit 38, the switch unit 39, and the switches 40 and 41, respectively. The storage unit 44 is connected to the offset control unit 34E and the offset adjustment signal addition unit 35 via the switch unit 39. The storage unit 44 includes a storage element that can store the offset correction voltage.

The configuration of this (Embodiment 4) will be described in more detail based on the offset adjustment operation.
When the offset adjustment start signal is input via the offset adjustment start signal input terminal 31, the offset control unit 34E controls the switch unit 39 to short-circuit the offset control unit 34E and the offset adjustment signal addition unit 35. After the offset correction voltage is detected and a control signal for causing the offset control unit 34E to create the offset correction voltage is held, the switch unit 39 is switched, the storage unit 44 and the offset control unit 34E are short-circuited, and the storage unit 44 and the offset The adjustment signal adding unit 35 is short-circuited. The control signal held by the offset control unit 34E is stored in the storage unit 44. Thereafter, the control signal stored in the storage unit 44 is read and input to the offset adjustment signal adding unit 35. The other operations are the same as the offset adjustment in (Embodiment 1).

  According to this configuration, since the control signal for generating the offset correction voltage is stored in the storage unit 44, it is not necessary to perform the offset adjustment every time the power is turned on, so that the time required for the offset adjustment can be saved. .

  In each of the above embodiments, the input amplifier 23 includes the input terminal IN1 to which the drive signal A1 is input and the input terminal IN2 to which the reference signal B1 is input, and the offset correction voltage is the input terminal IN1. Alternatively, it may be added to any of the input terminals IN2.

  INDUSTRIAL APPLICABILITY The present invention is useful for a load driving device and a load driving method having an offset adjustment function that reduces an input offset voltage in a dead zone.

Block diagram of a load driving apparatus according to (Embodiment 1) of the present invention Flow chart of offset adjustment of load drive device of embodiment Waveform diagram of each signal of offset adjustment circuit of load drive device of same embodiment Configuration diagram of an offset adjustment signal adding unit of the load driving device of the embodiment The block diagram of the load drive device of (Embodiment 2) of this invention Block diagram of a load driving device of (Embodiment 3) of the present invention Block diagram of a load driving device of (Embodiment 4) of the present invention Block diagram of a conventional load driving device Waveform diagram of each signal of the conventional load driving device

Explanation of symbols

21 drive signal input terminal 21A drive signal input terminal group 22 reference signal input terminal 23 input amplifier 24 absolute value circuit 25 pulse width modulation unit 26 polarity determination unit 27 triangular wave generation unit 28 drive output circuit 29 load 30 feedback amplifier 31 offset adjustment start signal Input terminal 32 Dead band determination unit 32A Dead band determination unit group 34 Offset control unit 35 Offset adjustment signal addition unit 35A Offset adjustment signal addition unit 37 Input amplifier input signal setting unit 37A Offset adjustment signal addition unit group 38 Feedback amplifier input signal setting unit 38A Feedback amplifier input signal setting unit group 39 Switch unit 40, 41 Switch 40A, 41A Switch group 42 Filter 43 Input resistance 44 Storage unit 45 Counter 45A Counter unit 46 Clock generation unit 100 Load drive device 100A Load drive unit 100B Load drive unit group 20 , 200A, 200E offset adjustment circuit

Claims (13)

The signal converted from the absolute value signal of the drive signal amplified by the input amplifier is used as the modulated signal, and the triangular wave lifted from the reference voltage by the voltage corresponding to the dead band of the input / output characteristics is used as the modulation signal. A width modulation signal is created, and a first pulse width modulation signal that is PWM-modulated is applied to one end of a load drive output circuit based on the pulse width modulation signal, and PWM modulation is applied to the other end of the load drive output circuit A load driving method of applying a second pulse width modulation signal and negatively feeding back a difference between the first and second pulse width modulation signals,
Set the drive signal as well as the negative feedback to zero,
Detecting the width of the dead zone of the input / output characteristics by adding an offset correction voltage that increases or decreases to the drive signal;
A load driving method in which the operation is performed while holding the offset correction voltage when the dead zone is set to the middle point, and the driving signal and the negative feedback are released from a state of being set to zero. The signal converted from the absolute value signal of the drive signal amplified by the input amplifier is used as the modulated signal, and the triangular wave lifted from the reference voltage by the voltage corresponding to the dead band of the input / output characteristics is used as the modulation signal. A width modulation signal is created, and a first pulse width modulation signal that is PWM-modulated is applied to one end of a load drive output circuit based on the pulse width modulation signal, and PWM modulation is applied to the other end of the load drive output circuit A load driving device that applies a second pulse width modulation signal and negatively feeds back a difference between the first and second pulse width modulation signals,
An offset adjustment signal adding unit for adding an offset adjustment signal for detecting an input offset voltage and an offset correction voltage for canceling the input offset voltage to the drive signal, and
An input amplifier input signal setting unit for switching the drive signal to zero;
A feedback amplifier input signal setting unit for switching the negative feedback to zero setting;
Comparing the absolute value signal and the substantially minimum voltage of the triangular wave to determine whether the drive signal is a dead band;
A counter that detects the dead zone width using the output signal of the dead zone determination unit and sets the midpoint of the dead zone;
A clock generation unit that outputs a clock signal synchronized with the timing of adding the offset adjustment signal to the offset adjustment signal addition unit;
An offset control unit that outputs a control signal for causing the offset adjustment signal adding unit to create the offset adjustment signal and the offset correction voltage according to the clock signal and the output signal of the counter; The negative feedback is set to zero, the offset correction voltage that increases or decreases is added to the drive signal to detect the width of the dead zone of the input / output characteristics, and the offset correction voltage when the dead zone is set to the midpoint A load driving device configured to perform normal operation while releasing the state in which the drive signal and the negative feedback are set to zero while operating while holding. The triangular wave generating unit that generates a triangular wave uses the output signal of the clock generating unit to synchronize the timing at which the offset adjustment signal is added and the timing at which the triangular wave signal becomes the minimum voltage, thereby outputting the triangular wave signal, The load driving device according to claim 2, wherein the dead zone determination unit is configured to compare the triangular wave signal and the absolute value signal at each timing when the minimum voltage of the triangular wave signal is output.   The load driving device according to claim 2, further comprising a storage unit that stores the offset correction voltage when the offset adjustment signal is set to a midpoint of the dead zone. 3. The load driving device according to claim 2, wherein the offset adjustment signal adding unit includes at least one constant current source, at least one resistor, and at least one switch. The offset adjustment signal adding unit includes at least one resistor arranged in series between one input terminal of an input amplifier that differentially amplifies a reference signal and a drive signal and a reference signal input terminal to which the reference signal is input. The load driving device according to claim 2, further comprising: at least one current source for causing a current to flow through the resistor. The offset adjustment signal adding unit includes at least one resistor arranged in series between one input terminal of an input amplifier that differentially amplifies the reference signal and the drive signal and the drive signal input terminal to which the drive signal is input. The load driving device according to claim 2, further comprising: at least one current source for causing a current to flow through the resistor.   The load driving device according to claim 6 or 7, wherein a resistance value of the resistor or a current value flowing through the resistor is varied. The load driving method according to claim 1, further comprising a step of storing the offset correction signal in a storage unit. The substantially minimum voltage of the triangular wave signal in the detection step uses the minimum voltage of the triangular signal synchronized with the frequency of the output signal of the clock generation unit, and sequentially adds or subtracts the offset correction voltage for each minimum voltage of the triangular wave signal. The load driving method according to claim 1, wherein control is performed. The dead band width of the output characteristic is detected by comparing the absolute value signal and the substantially minimum voltage of the triangular wave signal to detect the dead band width, and the substantially minimum voltage of the triangular wave signal forms the minimum voltage of the triangular wave generating unit. The load driving method according to claim 1, wherein the control step sequentially performs addition control in synchronization with the frequency of the output signal of the clock generation unit using a reference voltage. 2. The load driving method according to claim 1, wherein the offset correction voltage is controlled so as to monotonously increase or monotonously decrease. 2. The load driving method according to claim 1, wherein the offset correction voltage is controlled by a binary search method for searching for a target correction value while narrowing a search range by half.

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