JP2012068094A - Resolver signal processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resolver signal processing device capable of preventing to the utmost a deterioration in accuracy of an angle detected by a resolver, even in a situation where there are component variation, temperature change, and power supply voltage fluctuation.SOLUTION: According to an embodiment, when a microcomputer 21 outputs a sinusoidal excitation signal Sr to a resolver 2, and processes a cosine signal S3 and a sine signal S4 that are obtained by modulating amplitude of the excitation signal Sr according to a rotation angle of a brushless DC motor 1, an excitation PWM creating unit 25 generates and outputs, when an excitation DUTY for regulating a maximum amplitude of a sine wave is set, and at a rate corresponding to the excitation DUTY, an excitation PWM signal of which DUTY changes according to a change of amplitude for each phase of the sine wave, as an excitation signal S1. Then, an excitation signal control unit 24 adjusts the excitation signal S1 so that the maximum amplitude of a detected excitation signal Sr reaches a prescribed level.

Description

  Embodiments described herein relate generally to a resolver signal processing device that is used to detect a rotation angle of a motor by processing a signal output from a resolver arranged in the motor.

  The resolver signal processing device is provided, for example, in an in-vehicle electronic device such as an EPS (Electric Power Steering) -ECU (Electronic Control Unit), and the rotation angle of the handle shaft is determined based on a signal from a resolver connected to the handle shaft. To detect. For this purpose, a circuit for generating an excitation signal to be supplied to the resolver and a circuit for detecting a sine wave output signal and a cosine wave output signal, which are output signals of the resolver, are provided, and these output signals are multiplied by 1 times the excitation signal cycle. , 2 times, 2.5 times, etc., and the rotation angle of the handle is calculated by performing arctan calculation of both.

  The excitation signal input to the resolver is, for example, a sine wave signal of about 10 kHz, and the excitation signal circuit that generates the excitation signal, for example, when the microcomputer outputs a 10 kHz pulse signal, passes the pulse signal through a low-pass filter. Smooth into a sinusoidal signal. The sine wave signal is amplified to a predetermined amplitude value by an amplifier, a direct current component is cut by a coupling capacitor, and the sine wave signal is input to a resolver as an AC signal based on 0V. b

  Here, if the amplification factor of the amplifier is set high, the amplitude of the excitation signal input to the resolver increases, and the amplitude of the sine wave output signal and cosine wave output signal output from the resolver also increases. Then, since the A / D conversion resolution of the microcomputer (microcomputer) that performs the arctan calculation is increased, the detection accuracy of the rotation angle is improved. However, since the amplification factor is restricted by the power supply (for example, battery voltage) of the amplifier, the maximum amplitude that can be output is determined according to the power supply voltage of the amplifier. For this reason, if the amplification factor is too large, the peak and bottom of the sine wave that is the excitation signal are distorted and the angle detection accuracy decreases.

JP 2000-55695 A

However, if the amplification factor is determined so that the sinusoidal waveform can be maintained under any conditions due to the effects of component variations, temperature changes, and battery voltage fluctuations in the excitation signal circuit, component variations, temperature changes, battery voltage fluctuations, etc. Since the amplification factor has to be set lower than when there is no fluctuation, the detection accuracy of the rotation angle is lowered.
Therefore, a resolver signal processing device is provided that can prevent a decrease in accuracy of the angle detected by the resolver as much as possible even in a situation where there are component variations, temperature changes, and power supply voltage fluctuations.

  According to the embodiment, in the resolver signal processing apparatus that outputs a sinusoidal excitation signal to the resolver and processes the resolver detection signal in which the amplitude of the excitation signal is modulated according to the rotation angle of the motor, the pulse signal output unit includes: When a pulse signal for generating an excitation signal is output, the excitation signal generation unit generates and outputs an excitation signal by smoothing the pulse signal. Then, the amplitude adjustment unit adjusts the excitation signal output to the resolver so that the maximum amplitude of the excitation signal detected by the excitation signal detection unit becomes a predetermined level.

Functional block diagram showing the configuration of the control device according to the first embodiment The figure which shows the specific structure of a filter circuit and an amplifier Flow chart showing initial setting processing Flow chart showing control cycle interrupt processing Timing chart The figure which shows the waveform of excitation PWM signal S1 and excitation signal S2 (A) is a duty 90%, (b) is a diagram showing an excitation PWM signal S1 with a duty of 60%. The figure explaining the state from which the waveform of the excitation signal Sr changes according to the fall of a power supply voltage FIG. 1 equivalent view showing the second embodiment 3 equivalent figure 4 equivalent diagram Figure equivalent to FIG. 7 equivalent diagram

(First embodiment)
Hereinafter, a first embodiment will be described with reference to FIGS. 1 to 8. FIG. 1 is a block diagram showing a main part of a control device configured as, for example, an EPS-ECU (electronic control unit for electric power steering). The control device 20 includes a current detection circuit 5 for detecting a current flowing through the winding of the brushless DC motor 1, and an output terminal of the current detection circuit 5 is an A / D built in a microcomputer (microcomputer) 21. It is connected to the converter 22a. The current detection circuit 5 is configured to detect a terminal voltage of a shunt resistor inserted between the lower arm of the inverter main circuit 3 and the ground, for example.

  The inverter main circuit 3 is configured by, for example, six MOSFETs connected in a three-phase bridge. The six output terminals of the PWM circuit 23 built in the microcomputer 21 are connected to the gates of the FETs constituting the inverter main circuit 3 via the gate drive circuit 4. The inverter main circuit 3 supplies the PWM voltage to the three-phase winding of the brushless DC motor 1.

  The microcomputer 21 outputs a PWM signal (pulse signal) S1 created by an excitation signal control unit (excitation signal detection unit, amplitude adjustment unit) 24 and an excitation PWM creation unit (pulse signal output unit) 25, and the PWM signal S1. Is provided to a filter circuit (excitation signal generation unit) 11 for forming an excitation signal S2 (excitation reference signal). The filter circuit 11 includes a multi-stage low-pass filter for removing harmonics, a buffer operational amplifier, and the like (see FIG. 2). The excitation signal S2 is supplied to the excitation coil of the resolver 2 attached to the brushless DC motor 1 via the amplifier 12.

  A cosine coil and a sine coil (not shown) which are output coils of the resolver 2 are respectively connected to corresponding input terminals (+, −) of the differential amplifier 13, and an output signal of the differential amplifier 13 is The cosine signal S3 and the sine signal S4 (resolver detection signal) are given to the A / D converter 22c of the microcomputer 21. The process for detecting the rotational position Θ of the brushless DC motor 1, which will be schematically described below, is the same as that disclosed in JP-A-2005-210839. The latest data holding unit 26 and the previous data holding unit 27 are connected in series to the A / D converter 22c, and the latest A / D conversion data D1 and D2 are held in the latest data holding unit 26. The previous data holding unit 27 holds the previous A / D conversion data D3 and D4.

  Of the data D1 to D4 held in the latest data holding unit 26 and the previous data holding unit 27, the data D2 and D4 are given to the resolver SIN wave detection unit 28, and the data D1 and D3 are given to the resolver COS wave detection unit 29. It is done. The resolver SIN wave detector 28 calculates SIN data Dy (= D2-D4), and the resolver COS wave detector 29 calculates COS data Dx (= D1-D3). The SIN data Dy and the COS data Dx are given to the Atan calculation unit 30, and arctan (Dy / Dx) or arctan (Dx / Dy) is calculated (Atan calculation) according to the magnitude relationship of these data.

  The result of the Atan calculation is output to the rotation angle calculation unit 31, and the rotation angle calculation unit 31 performs the calculation by distinguishing eight patterns from the relationship between the COS and the SIN data Dx and Dy, and calculates the rotation position Θ. That is, each functional block inside the microcomputer 21 is a block diagram of the calculation process of the rotational position Θ performed in Japanese Patent Laid-Open No. 2005-210839.

  Next, the part that generates the excitation PWM signal S1 will be described. As shown in FIG. 6, the excitation PWM creating unit 25 of the microcomputer 21 outputs the excitation PWM signal S1 so as to generate a sinusoidal excitation signal S2 having a frequency of 10 kHz with a carrier having a frequency of 160 kHz, for example. For this reason, the excitation PWM creating unit 25 is given from the excitation signal control unit 24 the setting parameters of excitation DUTY, excitation phase, excitation PWM (carrier) frequency, and excitation frequency.

  Here, “excitation DUTY” is a parameter that sets a duty that defines the maximum amplitude of the sinusoidal excitation signal S2, and its maximum value is 100%. The “excitation phase” is a parameter for adjusting the output phase of the excitation PWM signal S1 when the excitation PWM generator 25 outputs the excitation PWM signal S1 in synchronization with the system clock signal of the microcomputer 21. When the above-described setting parameters are given, the excitation PWM creating unit 25 generates and outputs an excitation PWM signal S1 according to the setting.

  For example, in the case of the excitation PWM signal S1 shown in FIG. 6, excitation DUTY = 90%, excitation phase = 0 degree, excitation PWM frequency = 160 kHz, and excitation frequency = 10 kHz are set. Then, since the excitation PWM creating unit 25 generates a sine wave with a frequency of 10 kHz, the duty changes according to the amplitude level corresponding to each phase of the sine wave according to the ratio specified by the maximum duty of 90%. It is configured by hardware so as to generate and output a PWM signal having a frequency of 160 kHz. FIG. 7A shows only the excitation PWM signal S1 shown in FIG. 6, and FIG. 7B shows the excitation PWM signal S1 when excitation DUTY = 60%. .

  A drive voltage applied to the inverter main circuit 3, that is, a vehicle battery voltage Vbat, is given to the excitation signal control unit 24, and an excitation signal Sr input to the resolver 2 via the amplifier 12 is differentially applied. An amplified signal is given through an amplifier 32. Although not shown, these voltages are naturally A / D converted. The excitation signal control unit 24 determines some of the parameters to be set in the excitation PWM creation unit 25 according to these voltage levels. The microcomputer 21 is supplied with a control power supply (for example, 5 V) obtained by stepping down the battery voltage Vbat by a power supply circuit (not shown). The power supply of the other components of the control device 20 excluding the microcomputer 21 is a battery. The voltage Vbat is directly supplied.

  FIG. 2 shows a specific configuration of the filter circuit 11 and the amplifier 12. The filter circuit 11 is composed of a secondary RC filter, and the filtered output signal is supplied to the buffer amplifier 33. The output terminal of the buffer amplifier 33 is connected to a resistance element R3 that is an input terminal of the amplifier 12 via a coupling capacitor C1. The resistor element R3 is connected to the inverting input terminal of the operational amplifier 34, and is connected to one end side of the coupling capacitor C3 through a parallel circuit of the resistor element R4 and the capacitor C2.

  The non-inverting input terminal of the operational amplifier 34 is connected to the ground via the resistance element R5 and is connected to the output terminal of the buffer amplifier 35 via the resistance element R6. The buffer amplifier 35 outputs a potential Vbat / 2 obtained by dividing the battery voltage Vbat by 1/2 with the resistance elements R1 and R2. A series circuit of a resistance element R7, diodes D1 and D2, and a resistance element R8 is connected between the battery voltage Vbat and the ground, and an output terminal of the operational amplifier 34 is connected to a common connection point of the diodes D1 and D2. ing.

The collector and base of the NPN transistor Q1 are respectively connected to both ends of the resistor element R7, and the base and collector of the PNP transistor Q2 are respectively connected to both ends of the resistor element R8. The emitters of the NPN transistor Q1 and the PNP transistor Q2 are connected to one end of a coupling capacitor C3 via resistance elements R9 and R10, respectively. The other end of the coupling capacitor C3 is connected to an excitation coil (not shown) of the resolver 2, and an excitation signal Sr with a DC component cut is output.
When the potential at the common connection point of the diodes D1 and D2 applied via the operational amplifier 34 fluctuates, the NPN transistor Q1 and the PNP transistor Q2 are increased or decreased with respect to the potential by the forward voltage Vf of the diodes D1 and D2. Base potential fluctuates. As a result, the on / off states of the transistors Q1 and Q2 change, and the potential on one end side of the coupling capacitor C3 changes.

Here, when the potential at the common connection point (input point) of the capacitor C1 and the resistance element R3 is Vin and the potential at the common connection point (output point) of the resistance elements R9 and R10 is Vout, the following relationship is established.
Vout = R5 / (R5 + R6). (R3 + R4) /R3.Vbat/2
-R4 / R3 · Vin (1)
In the formula (1), when R3 = R5 = Rs and R4 = R6 = Rf,
Vout = Rs / (Rs + Rf). (Rs + Rf) /Rs.Vbat/2
-Rf / Rs · Vin
= Vbat / 2−Rf / Rs · Vin (2)
It becomes. That is, in the amplifier 12, the circuit centered on the operational amplifier 34 is level-shifted so that the input signal Vin becomes a signal whose amplitude swings up and down around the midpoint potential Vbat / 2.

Then, assuming that the voltage drop at the output point with respect to the battery voltage Vbat is Vdrop and the voltage rise at the output point with respect to the ground potential is Vrise, these are expressed by equations (3) and (4), respectively. However, IB is a current flowing through the resistance element R7, and IC is a collector current of the transistor Q1.
Vdrop = R7 · IB + VBE (Q1) + R9 · IC (3)
Vrise = R8 · IB + VBE (Q2) + R10 · IC (4)
That is, the amplification factor of the amplifier 12 is determined by the resistance ratio of the resistance elements R3 and R4 and the resistance ratio of the resistance elements R8 to R10.

  By the way, in order to increase the detection accuracy of the rotation angle Θ, it is desirable to increase the amplitudes of the limit signal S3 and the cosine signal S4 as described above. For this purpose, the amplitude of the excitation signal Sr may be increased. Going back further, for that purpose, the maximum duty of the excitation PWM signal S1 input to the filter circuit 11 may be increased. However, the smoothness and amplification degree of the filter circuit 11 and the amplifier 12 may change depending on circuit component variations and temperature conditions, and accordingly, the maximum amplitude of the excitation signal Sr changes from the initial set value.

  Therefore, in the present embodiment, by detecting the amplitude of the excitation signal Sr, for example, if the amplification degree is higher than when there is no variation, the duty of the excitation PWM signal S1 is reduced and the maximum of the excitation signal Sr is reduced. Adjustment is made so that the amplitude becomes the same value as when there is no variation in circuit components. When the battery voltage Vbat decreases, if the maximum amplitude target value of the excitation signal Sr is the same as when the battery voltage Vbat is a normal level (for example, 12 V), the amplified output level of the amplifier 12 is the battery voltage Vbat. Therefore, as shown in FIG. 8, the top and bottom of the sinusoidal excitation signal are crushed.

  In the case of the amplifier 12 shown in FIG. 2, the positive side amplitude of the output voltage Vout decreases by the voltage drop Vdrop of the equation (3), and the negative side amplitude increases by the voltage rise Vrise of the equation (4). Therefore, the maximum amplitude voltage (Vp-p; peak-to-peak) that can be output by the amplifier 12 is limited by the voltages Vdrop and Vrise above the battery voltage Vbat. In this case, the maximum amplitude value (target value) of the excitation signal Sr is lowered according to the detected level of the battery voltage Vbat.

  Hereinafter, the processing procedure will be described with reference to FIGS. FIG. 3 is a flowchart showing an initial setting process performed by the excitation signal control unit 24 for the excitation PWM creation unit 25. The excitation signal control unit 24 sets an excitation frequency (step S1), an excitation PWM frequency (step S2), an excitation phase (step S3), and an excitation DUTY initial value (step S4). The initial value of excitation DUTY is 50%, for example.

  FIG. 4 is a flowchart showing the control contents of the microcomputer 21 centering on the excitation signal control unit 24, and FIG. 5 is a timing chart showing signal waveforms of each part corresponding to the control contents. The flowchart shown in FIG. 4 is a routine for processing a control cycle interrupt that occurs when the count value of a control cycle counter that performs an up / down count operation with a cycle of 50 μs, for example (see FIG. 5A), becomes zero. Is executed (see FIG. 5B). First, the excitation signal control unit 24 reads the value of the battery voltage Vbat (step S11), and sets an excitation upper limit value and an excitation lower limit value according to the value of the battery voltage Vbat (step S12).

Here, the excitation upper limit value and the excitation lower limit value are values for setting the maximum amplitude target value (Vp-p) of the excitation signal Sr, and for the battery voltage Vbat, the upper limit threshold is set to 7 V, for example, and the lower limit threshold is set to 4 V, for example. Above, set as follows.
Battery voltage Vbat Excitation upper limit, Excitation lower limit (indicated by ±)
7V or more 3V ± 0.1V
Less than 7V and more than 4V Set with 7V and 4V set values by linear interpolation
4V 1.5V ± 0.1V
Less than 4V Excitation impossible (area where control device 20 does not operate)
That is, when the maximum amplitude target value of the excitation signal Sr is 3V and the battery voltage Vbat is 7V or more, it is easy to adjust the maximum amplitude according to the target value. 1V, excitation lower limit 2.9V. Then, if the maximum amplitude is adjusted according to the original target value in a state where the battery voltage Vbat is reduced to less than 7V, the waveform of the excitation signal Sr is distorted as shown in FIG. Therefore, in a region where the battery voltage Vbat is less than 7V and more than 4V, the target value is lowered below 3V. For example, when the battery voltage Vbat = 6V, the excitation upper limit value is 2.6V and the excitation lower limit value is 2.4V.

  In the subsequent step S13, an excitation PWM signal S1 is output by the excitation PWM generator 25 in accordance with the set parameter (see FIG. 5C), and the excitation signal controller 24 outputs the excitation signal Sr via the differential amplifier 32. An A / D conversion value is read (step S14). As shown in FIG. 5E, the A / D conversion of the excitation signal Sr is periodically executed at a timing different from the interrupt processing shown in FIG. 4 (the timing is initially set separately). In step S14, data stored in the data buffer or the like (data immediately before A / D conversion) is read.

  In the next step S15, the number of control cycle interruptions is counted. This is because it is only determined whether or not the count value is an odd number (see step S16, FIG. 5B). 0 and 1 may be alternately repeated. If the count value is an odd number (YES), the value read in step S14 is stored as an “excitation H value” (see step S17, FIG. 5 (f)), and if the count value is an even number (NO). The value read in step S14 is stored as an “excitation L value” (see step S19, FIG. 5G).

In step S18 following step S17, the maximum amplitude value of the excitation signal Sr is determined as follows.
Maximum amplitude value = (Excitation H value)-(Excitation L value)
Calculate with The “excitation L value” here is a value stored in the previous control cycle. In step S20 following step S19, the maximum amplitude value is
Maximum amplitude value = (Excitation L value)-(Excitation H value)
Calculate with The “excitation H value” here is also a value stored in the previous control cycle. That is, the maximum amplitude value (Vp-p) of the excitation signal Sr is obtained from the absolute value of the difference between the “excitation H value” and the “excitation L value”.

  Subsequent steps S21 to S24 are processes in which the excitation signal control unit 24 adjusts the excitation DUTY from the initial value. First, it is determined whether or not the maximum amplitude value of the excitation signal Sr calculated in step S18 or S20 exceeds the excitation upper limit value (step S21). If it exceeds (YES), the DUTY adjustment is performed from the previous set value. The value reduced by a value (for example, 2%) is set in the excitation PWM creating unit 25 as a new excitation DUTY (step S22). If the excitation upper limit is not exceeded (NO), the process proceeds to step S23.

  In step S23, it is determined whether or not the maximum amplitude value of the excitation signal Sr is below the excitation lower limit value. If it is below (YES), a value obtained by adding the DUTY adjustment value to the previous set value is newly excited. DUTY is set in the excitation PWM creating unit 25 (step S24). If it is not below the excitation lower limit value (NO), the maximum amplitude value is not more than the excitation upper limit value and not less than the excitation lower limit value, and the process proceeds to step S25 (same after execution of step S22). . In step S25, the rotation angle Θ detected by the resolver 2 is calculated by the A / D converter 22c to the rotation angle calculation unit 31.

  As described above, according to this embodiment, the microcomputer 21 outputs the sinusoidal excitation signal Sr to the resolver 2, and the cosine signal S3 in which the amplitude of the excitation signal Sr is modulated in accordance with the rotation angle of the brushless DC motor 1. In the case of the sine signal S4, when the excitation DUTY that defines the maximum amplitude of the sine wave is set, the excitation PWM generator 25 changes the amplitude level for each phase of the sine wave at a ratio according to the excitation DUTY. An excitation PWM signal whose duty changes accordingly is generated and output as an excitation signal S1. Then, the excitation signal control unit 24 adjusts the excitation signal S1 so that the maximum amplitude of the detected excitation signal Sr becomes a predetermined level.

  Specifically, when the battery voltage Vbat is 7 V or more, the excitation signal control unit 24 adjusts the excitation signal Sr so that the maximum amplitude of the excitation signal Sr maintains a predetermined maximum value 3 V (Vp-p). When Vbat is less than 7 V, the excitation DUTY setting value is adjusted so that the maximum amplitude of the excitation signal Sr is maximized within a range in which distortion does not occur. That is, when the battery voltage Vbat decreases, the duty of the excitation PWM signal output from the microcomputer 21 is decreased to adjust the amplified output of the amplifier 12 to decrease. Similarly, even when the output of the amplifier 12 tends to exceed the voltage range limited according to the level of the battery voltage Vbat due to circuit variations and temperature changes, the duty of the excitation PWM signal is reduced to amplify the amplifier 12. Adjust the output. Therefore, even in a situation where there is a variation factor that limits the output voltage range of the amplifier 12 as described above, it is possible to prevent the accuracy of the angle detected by the resolver 2 from being lowered as much as possible.

  In addition, the excitation PWM signal S2 whose duty changes with a sinusoidal amplitude rate output from the excitation PWM generator 25 includes a lower frequency component than when an excitation signal having the same frequency is generated from a PWM signal having a constant duty. Therefore, the time constant of the filter circuit 11 can be further reduced. For example, as shown in FIG. 2, the circuit scale can be reduced by reducing the order of the RC filter from the third order to the second order. Further, there is an effect that the response delay of the signal becomes smaller.

(Second Embodiment)
9 to 13 show a second embodiment. The same parts as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. Hereinafter, different parts will be described. In FIG. 9 corresponding to FIG. 1, the control device 50 includes a microcomputer 51 that replaces the microcomputer 21, and the microcomputer 51 replaces the excitation signal control unit 24 and the excitation PWM creation unit 25 with the excitation signal control unit. 52 and a timer function unit 53. When the excitation PWM frequency and the timer DUTY are set by the excitation signal control unit 52, the timer function unit 53 is an excitation PWM that has a constant duty at a carrier frequency of 160 kHz so that the frequency of the excitation PWM signal becomes a set value. Generate and output a signal.

  Next, the operation of the second embodiment will be described with reference to FIGS. In the initial setting process shown in FIG. 10, the excitation signal control unit 52 sets the frequency of the excitation PWM signal S1 (step S31) and the DUTY initial value (H side DUTY, step S32) in the timer function unit 53, respectively. The initial value of excitation DUTY is set to 50% as in the first embodiment. In the control cycle interruption process shown in FIG. 11, step S13 is deleted from the process shown in FIG. 4, and steps S41 to S43 are added.

  If the control cycle interrupt count is an even number (step S16: NO), the H side DUTY of the excitation PWM signal S1 is set (step S41). Here, the H-side DUTY set first is the value initially set in step S31. On the other hand, when the count number is an odd number (step S16: YES), the L side DUTY of the excitation PWM signal S1 is set (step S42). Here, the L-side DUTY set first is a value obtained by subtracting the value initially set in step S31 from 100% (if the excitation DUTY initial value is 50%, it is equal to 50%). This process is performed by performing H side / L side conversion of excitation DUTY in step S43 after executing steps S17 to S24 in the same manner.

  That is, as shown in FIG. 12C or FIG. 13A, when the H-side DUTY is 90%, the timer function unit 53 causes the excitation PWM signal with a duty of 90% when the number of control interrupts is an even number. S1 is generated and output. When the number of control interruptions is an odd number, an excitation PWM signal S1 having a duty of 10% is generated and output. As shown in FIG. 13B, when the H-side DUTY is 60%, the timer function unit 53 generates and outputs the excitation PWM signal S1 with a duty of 60% when the number of times of control interruption is an even number. When the number of control interruptions is an odd number, an excitation PWM signal S1 having a duty of 40% is generated and output.

Further, although the excitation signal Sr and the A / D conversion timing shown in FIGS. 12D and 12E are different from those in FIG. 5, the excitation PWM signal S1 of the second embodiment is the same as that of the first embodiment. Since the frequency component is lower than that of the signal S1, the order of the filter circuit 54 is made larger than that of the filter circuit 11, and as a result, the excitation PWM signal S1 is output at a later timing. . Accordingly, the timing for performing A / D conversion is also different from that of the first embodiment.
As described above, according to the second embodiment, the microcomputer 51 generates and outputs the excitation PWM signal S1 using the timer function unit 53, so that the configuration can be simpler than that of the microcomputer 21.

Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.
For example, the amplitude of the excitation signal S2 may be adjusted by adjusting the amplification factor of the amplifier.
The upper limit threshold and lower limit threshold for the battery voltage Vbat, the excitation upper limit value, the excitation lower limit value, the DUTY adjustment value, etc. for the excitation signal Sr may be changed as appropriate according to the individual design.
The power source need not be limited to batteries.
The present invention is not limited to the one configured as an EPS-ECU, and can be applied to any device that processes resolver signals.

  In the drawings, 1 is a brushless DC motor, 2 is a resolver, 11 is a filter circuit (excitation signal generation unit), 12 is an amplifier, 20 is a control device (resolver signal processing device), 21 is a microcomputer, and 24 is an excitation signal control unit. (Excitation signal detection unit, amplitude adjustment unit), 25 is an excitation PWM creation unit (pulse signal output unit), 50 is a control device (resolver signal processing device), 51 is a microcomputer, 52 is an excitation signal control unit (excitation signal detection) , 53 represents a timer function unit (pulse signal output unit), and 54 represents a filter circuit (excitation signal generation unit).

Claims (4)

In a resolver signal processing device that outputs a sinusoidal excitation signal to a resolver and processes a resolver detection signal in which the amplitude of the excitation signal is modulated according to the rotation angle of the motor.
A pulse signal output unit for outputting a pulse signal for generating the excitation signal;
An excitation signal generator that generates and outputs the excitation signal by smoothing the pulse signal;
An excitation signal detector for detecting the excitation signal;
A resolver signal processing apparatus comprising: an amplitude adjustment unit that adjusts an excitation signal output to the resolver so that the maximum amplitude of the excitation signal detected by the excitation signal detection unit becomes a predetermined level. . The amplitude adjustment unit adjusts the maximum amplitude of the excitation signal detected by the excitation signal detection unit to maintain a predetermined maximum value if the power supply voltage is equal to or higher than a predetermined threshold,
2. The resolver signal according to claim 1, wherein when the power supply voltage falls below a predetermined threshold, the maximum amplitude of the excitation signal detected by the excitation signal detection unit is adjusted to be maximum within a range in which distortion is not distorted. Processing equipment. The pulse signal output unit generates the pulse signal by a PWM (Pulse Width Modulation) method,
The amplitude adjustment unit changes the duty of the pulse signal based on the value of the power supply voltage supplied to the excitation signal generation unit and the amplitude value of the excitation signal detected by the excitation signal detection unit. The resolver signal processing device according to claim 1 or 2. The pulse signal output unit is a pulse whose duty changes according to a change in amplitude with respect to each phase of the sine wave at a ratio according to the maximum duty when a maximum duty defining a maximum amplitude of the sine wave is set. Generate a signal,
The amplitude adjustment unit is configured to set the maximum duty set in the pulse signal output unit based on a value of a power supply voltage supplied to the excitation signal generation unit and an amplitude value of the excitation signal detected by the excitation signal detection unit. The resolver signal processing apparatus according to claim 3, wherein:

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