JP6109370B1 - Rotation angle detector - Google Patents

Abstract

Disclosed is a rotation angle detection device capable of reducing a loss of an excitation circuit of a resolver and suppressing an influence on rotation angle detection accuracy. A magnetic field formed by an excitation signal applied to an excitation winding is frequency-modulated by rotation of a rotating electrical machine to generate an induction signal in the induction winding, and applied to the excitation winding of the resolver. Excitation means 3 for outputting a sine wave excitation voltage for output, PWM drive means 4 for outputting an excitation pulse of a PWM signal to be applied to the excitation winding of the resolver 2, and a sine wave output by the excitation means 3 Switching means 6 that switches the excitation voltage and the excitation pulse of the PWM signal output by the PWM drive means 4 and applies it to the excitation winding of the resolver 2, and loss can be reduced and the influence on the rotation angle detection accuracy can be suppressed. The control means 10 which provides a switching signal with respect to the switching means 6 when it will be in a state is provided. [Selection] Figure 1

Description

  The present invention relates to a rotation angle detection device that detects a rotation angle and a rotation speed of a rotating electrical machine such as a motor generator using a resolver.

  2. Description of the Related Art Conventionally, resolvers that are simpler in structure than optical encoders and less error due to temperature change are widely used as rotation angle detection devices that detect the rotation angle and rotation speed of a rotating electrical machine. However, the resolver is easily affected by external magnetic flux generated by a motor coil of a motor generator that is a rotating electrical machine. For this reason, in order to reduce the influence of external magnetic flux, various structural measures are taken for the winding of the resolver. (For example, Patent Document 1)

Japanese Patent No. 5289420

  In a conventional rotation angle detection device using a resolver, in order to further reduce the influence of external magnetic flux, the amplitude or frequency of the excitation signal applied to the excitation winding of the resolver is increased to induce in the induction winding of the resolver. The S / N ratio of the induced signal is improved. However, if the amplitude of the excitation signal applied to the excitation winding is increased, the excitation current increases, so that it is necessary to increase the rated capacity of the switching element used in the excitation circuit of the resolver and the element size increases. In addition, there is a problem in that the amount of heat generated increases due to an increase in power loss due to an increase in power consumption of the excitation circuit of the resolver.

  The present invention has been made to solve the above-described problems, and has an object to provide a rotation angle detection device that can reduce the loss of the excitation circuit of the resolver and can suppress the influence on the rotation angle detection accuracy. To do.

  A rotation angle detection device according to the present invention includes a resolver that generates a induced signal in an induction winding by frequency-modulating a magnetic field formed by an excitation signal applied to an excitation winding by rotation of a rotating electrical machine, and excitation of the resolver An excitation means for outputting a sinusoidal excitation voltage for application to the winding, a PWM drive means for outputting an excitation pulse of a PWM signal for application to the excitation winding of the resolver, and an output by the excitation means Switching means for switching the excitation voltage of the sine wave and the excitation pulse of the PWM signal output by the PWM driving means to apply to the excitation winding of the resolver, and the loss can be reduced and the influence on the rotation angle detection accuracy is suppressed. Control means for providing a switching signal to the switching means when it becomes possible is provided.

  According to this invention, the magnetic field formed by the excitation signal applied to the excitation winding is frequency-modulated by the rotation of the rotating electrical machine to generate the induction signal in the induction winding, and the resolver is applied to the excitation winding of the resolver. Excitation means for outputting a sine wave excitation voltage for output, PWM drive means for outputting an excitation pulse of a PWM signal for application to the excitation winding of the resolver, and excitation for a sine wave output by the excitation means Switching means for switching the voltage and the excitation pulse of the PWM signal output by the PWM drive means to apply to the excitation winding of the resolver, and in a state where loss can be reduced and the influence on the rotation angle detection accuracy can be suppressed. In this case, since the control means for giving a switching signal to the switching means is provided, the loss of the excitation circuit of the resolver can be reduced, and the rotation angle detection accuracy can be improved. Effect there is an effect that it is possible to obtain a rotational angle detecting apparatus capable of suppressing.

It is a block diagram which shows schematic structure of the rotation angle detection apparatus in Embodiment 1 of this invention. It is a circuit diagram which shows an example of the circuit structure of the rotation angle detection apparatus in Embodiment 1 of this invention. It is a flowchart explaining operation | movement of the control means of the rotation angle detection apparatus in Embodiment 1 of this invention. It is explanatory drawing explaining the switching waveform at the time of the PWM drive of the rotation angle detection apparatus in Embodiment 1 of this invention. It is a block diagram which shows schematic structure of the rotation angle detection apparatus in Embodiment 2 of this invention. It is a flowchart explaining operation | movement of the control means of the rotation angle detection apparatus in Embodiment 2 of this invention. It is a block diagram which shows schematic structure of the rotation angle detection apparatus in Embodiment 3 of this invention. It is a flowchart explaining operation | movement of the control means of the rotation angle detection apparatus in Embodiment 3 of this invention. It is a block diagram which shows schematic structure of the rotation angle detection apparatus in Embodiment 4 of this invention. It is a circuit diagram which shows an example of the circuit structure of the rotation angle detection apparatus in Embodiment 4 of this invention. It is a flowchart explaining operation | movement of the control means of the rotation angle detection apparatus in Embodiment 4 of this invention.

Hereinafter, embodiments of the present invention will be described. In the drawings, the same or corresponding parts will be described with the same reference numerals.
Embodiment 1 FIG.
1 is a block diagram showing a schematic configuration of a rotation angle detection device according to Embodiment 1 of the present invention, FIG. 2 is a circuit diagram showing an example of a circuit configuration of the rotation angle detection device according to Embodiment 1 of the present invention, and FIG. FIG. 4 is a flowchart for explaining the operation of the control means of the rotation angle detection device according to the first embodiment of the present invention. FIG. 4 is a diagram for explaining the switching waveform during PWM driving of the rotation angle detection device according to the first embodiment of the present invention. FIG.

  In FIG. 1, a rotation angle detection device 1 includes, for example, a resolver 2 that detects a rotation angle and a rotation speed of a rotating electrical machine (not shown) such as a motor generator, and a sine wave that is applied to an excitation winding of the resolver 2 An excitation means 3 for outputting an excitation signal (voltage), a PWM drive means 4 for outputting an excitation pulse of a PWM signal (Pulse Width Modulation) to be applied to the excitation winding of the resolver 2, and a resolver 2 Excitation current of the resolver 2 by switching the excitation current detection means 5 for detecting the excitation current flowing in the excitation winding, the excitation signal of the sine wave output from the excitation means 3 and the excitation pulse of the PWM signal output from the PWM drive means 4 A switching means 6 to be applied to the windings and a control means 10 for giving a switching signal to the switching means 6 are constituted.

FIG. 2 shows an example of the circuit configuration of each means in FIG. 1, and the detailed configuration of each means will be described below with reference to FIG.
The resolver 2 has an excitation winding and an induction winding. A magnetic field generated by an excitation signal applied to the excitation winding of the resolver 2 is frequency-modulated by rotation of a rotating shaft of a rotating electrical machine (not shown), and is induced as an induction signal in the induction winding of the resolver 2. Therefore, the rotation angle and the rotation speed of the rotating electrical machine can be detected by comparing the excitation signal and the induction signal.

  The excitation means 3 amplifies the sine wave excitation signal output from the control means 10 and applies the sine wave excitation signal to the excitation winding of the resolver 2. Here, when the amplitude of the excitation signal is increased, the amplitude of the excitation current is increased, and the magnetic field formed by the excitation current is also increased. Therefore, the excitation signal is less affected by the external magnetic flux, and the S / N ratio of the induced signal is improved. Thus, the rotation angle detection accuracy is relatively improved. As the excitation means 3, for example, a push-pull type circuit using a transistor, an operational amplifier or the like as shown in FIG. 2 shows a circuit configuration of both positive and negative power supplies, but in the case of a single power supply circuit configuration, push-pull type circuits are provided at both ends of the excitation winding of the resolver 2, respectively.

  The PWM drive unit 4 includes, for example, a triangular wave generation circuit 7 that generates a triangular wave at the same frequency as the carrier frequency of the PWM signal, and a sine wave signal and a triangular wave generation circuit that are input to the operational amplifier of the excitation unit 3 as shown in FIG. A circuit configuration using a comparator for comparing the triangular wave 7 is conceivable.

  The excitation current detection means 5 is provided with a resistor between the resolver 2 and the excitation means 3 as shown in FIG. 2, for example, and the voltage across the resistor is input to the differential amplifier to convert the current signal into a voltage signal. Thus, a configuration for detection is conceivable.

  As shown in FIG. 2, the switching unit 6 is provided in the excitation unit 3, and the switching operation is controlled by a switching signal from the control unit 10. Further, as a specific circuit of the switching means 6, for example, a transistor switch and gate drive circuit or an inverter circuit as shown in FIG. 2 can be considered, and a significant signal (Hi in FIG. 2) is transmitted from the control means 10. Then, the switching unit 6 selects the PWM drive unit 4 in the excitation unit 3 as a current path to the resolver 2 so that an excitation pulse can be applied to the resolver 2.

Based on the sinusoidal excitation signal Vin (θ) and the excitation current IL detected by the excitation current detection means 5, the control means 10 calculates the loss Ptr of the transistor of the excitation means 3 as Ptr = Vin (θ−180 [deg]. ) × IL.
The control means 10 prepares in advance a loss map when an excitation current is applied to the resolver using the PWM drive means 4, and compares it with the calculated transistor loss Ptr to determine the transistor loss Ptr. However, if the loss is larger than the loss when the PWM driving means 4 is used, a switching signal is transmitted to the switching means 6 and the excitation pulse of the PWM signal output from the PWM driving means 4 is used.

Hereinafter, the switching operation of the switching unit 6 by the control unit 10 will be specifically described with reference to the flowchart shown in FIG.
In step S100, the control means 10 reads the excitation current value IL detected by the excitation current detection means 5 while the excitation signal of the sine wave output from the excitation means 3 is applied to the excitation winding of the resolver 2. The process proceeds to step S101.
In step S101, the control means 10 determines the transistor of the excitation means 3 based on the sinusoidal excitation signal Vin (θ) output to the excitation means 3 and the excitation current value IL detected by the excitation current detection means 5. The loss Ptr is calculated and estimated, and the process proceeds to step S102.

In step S102, the control unit 10 compares the estimated transistor loss Ptr of the excitation unit 3 with a loss map when an excitation current is applied to the resolver 2 using the PWM drive unit 4 prepared in advance. If the loss Ptr is larger than the loss when the PWM drive unit 4 is used (YES), the process proceeds to step S103, and if not (NO), the process returns to step S100.
In step S103, the control unit 10 transmits a switching signal (Hi in FIG. 2) to the switching unit 6, and the switching unit 6 selects the PWM driving unit 4 in the excitation unit 3 as a current path to the resolver 2. An excitation pulse is applied to the excitation winding of the resolver 2.

  The method for obtaining the loss map when the excitation current is applied to the resolver 2 using the PWM drive means 4 is a method of estimating by a simulation simulating circuit constants, a method of confirming the loss by actual machine operation, or A method of simply building a switching waveform model as shown in FIG. 4 and estimating the loss can be considered. Here, as an example, a method for estimating the loss using the switching waveform model shown in FIG. 4 will be described.

The loss PtrON in the switching ON period is expressed as follows: PtrON = VB × Ic × using the voltage change 2VB (in the case of both power supplies, VB in the case of a single power supply), the current change Ic, and the ON transient time Ton It can be expressed in Ton / 3.
Similarly, the loss PtrOFF in the switching OFF period can be expressed as PtrOFF = VB × Ic × Toff / 3 using the voltage change 2VB, the current change Ic, and the OFF transient time Toff in the period b in FIG.
Further, the loss PON during the ON period of the transistor is calculated by using the collector-emitter voltage Vce and the excitation current Ic of the transistor and the PWM carrier frequency Fpwm and the duty ratio Duty of the excitation pulse of the PWM signal in the period c of FIG. Vce × Ic × Duty × Fpwm.
Therefore, the loss Ptr_1cyc for one PWM drive cycle is the sum of the above-mentioned losses, and can be estimated by Ptr_1cyc = PtrON + PtrOFF + PON.

  As described above, in the first embodiment, when a sine wave excitation voltage is applied to the excitation winding of the resolver 2 by the excitation unit 3, the control unit 10 detects the excitation detected by the excitation current detection unit 5. When the loss estimation of the excitation means 3 based on the current is large and the loss is reduced by PWM driving the excitation means 3, a switching signal is transmitted to the switching means 6, and the excitation pulse is sent to the resolver 2 by the PWM driving means 4. Therefore, the loss of the excitation means 3 can be reduced. As a result, the size of the circuit element can be reduced and the substrate heat radiation area can be reduced, and the excitation means 3 can be reduced in size. In addition, by applying an excitation pulse to the excitation winding of the resolver 2 by the PWM drive unit 4, it is possible to minimize the influence on the rotation angle detection accuracy.

Embodiment 2. FIG.
FIG. 5 is a block diagram showing a schematic configuration of the rotation angle detection device according to the second embodiment of the present invention, and FIG. 6 is a flowchart for explaining the operation of the control means of the rotation angle detection device according to the second embodiment of the present invention. .
In the first embodiment, when a sine wave excitation voltage is applied to the excitation winding of the resolver 2 by the excitation unit 3, the control unit 10 reduces the loss by PWM driving the excitation unit 3. In the second embodiment, the switching signal is transmitted to the switching unit 6 and the excitation pulse is applied to the excitation winding of the resolver 2 by the PWM driving unit 4. In the second embodiment, the PWM driving unit in the excitation unit 3 is described. 4, when an excitation pulse is applied to the excitation winding of the resolver 2, the control means 10 a shown in FIG. 5 indicates that when the duty ratio (Duty) of the excitation pulse of the PWM signal reaches a predetermined set value, A case where the excitation means 3 is switched from the excitation pulse application by the PWM drive means 4 to the sinusoidal excitation voltage application will be described.
In FIG. 5, the control means 10a reads the excitation pulse output from the PWM drive means 4. Since the configuration of other parts is the same as that of the first embodiment, description thereof is omitted.

Hereinafter, the switching operation of the switching unit 6 by the control unit 10a will be specifically described with reference to the flowchart shown in FIG.
In step S200, in a state where the excitation pulse output from the PWM drive unit 4 is applied to the excitation winding of the resolver 2, the control unit 10a performs the pulse width (time) of the excitation pulse of the PWM signal output from the PWM drive unit 4. ), The duty ratio (ON Duty) of the excitation pulse of the PWM signal is calculated, and the process proceeds to step S201.

  In step S201, the control means 10a proceeds to step S202 if the calculated duty ratio is greater than or equal to the preset maximum threshold value or less than the minimum threshold value (YES), and otherwise ( If NO, the process returns to step S200. Here, as the threshold value, for example, a method of setting a maximum value or a minimum value of a duty ratio (Duty) that can be realized as an excitation pulse in consideration of a slew rate of a transistor constituting the excitation unit 3 can be considered. Alternatively, the maximum value of the duty ratio may be simply set to 100% and the minimum value may be set to 0%.

  In step S202, the control unit 10a transmits a switching signal (Lo in FIG. 2) to the switching unit 6, and the switching unit 6 excites the current path to the resolver 2 from the PWM drive unit 4 in the excitation unit 3. Switching from the application of the pulse to the application of the excitation voltage of the output sine wave from the excitation means 3 is performed.

As described above, in the second embodiment, when the excitation pulse of the PWM signal is applied to the excitation winding of the resolver 2 by the PWM drive unit 4 in the excitation unit 3, the control unit 10a When the duty ratio of the excitation pulse reaches a preset maximum value or minimum value of the duty ratio that can be realized as the excitation pulse, a switching signal is transmitted to the switching means 6, and from the excitation pulse application by the PWM driving means 4. Since switching to the application of the sine wave excitation voltage of the excitation means 3 is performed, waveform distortion can be suppressed in a fine current control region that cannot be realized by PWM driving, and the influence on the rotation angle detection accuracy can be suppressed. Since the loss due to PWM drive is the same as the loss due to the sine wave excitation voltage, the effect on the loss can be minimized. That.
Further, when the duty ratio is not within the maximum value or the minimum value, the excitation winding of the resolver 2 is excited by PWM drive, so that the loss of the excitation means 3 can be reduced and the circuit element size can be reduced. In addition, the heat radiation area of the substrate can be reduced, and the excitation means 3 can be downsized.

Embodiment 3 FIG.
FIG. 7 is a block diagram showing a schematic configuration of a rotation angle detection device according to Embodiment 3 of the present invention, and FIG. 8 is a flowchart for explaining the operation of the control means of the rotation angle detection device according to Embodiment 3 of the present invention. .
In the second embodiment, when the excitation pulse is applied to the excitation winding of the resolver 2 by the PWM drive unit 4 in the excitation unit 3, the control unit 10a performs the duty ratio (Duty) of the excitation pulse of the PWM signal. In the third embodiment, the case where the excitation means 3 is switched from the excitation pulse application by the PWM drive means 4 to the sine wave excitation voltage application has been described. When an excitation pulse is applied to the excitation winding of the resolver 2 by the drive unit 4, the control unit 10b shown in FIG. 7 detects the drive signal of the rotating electrical machine 30 such as a motor generator, A case of switching from excitation pulse application by the PWM drive means 4 to sine wave excitation voltage application will be described.
In FIG. 7, the control means 10b detects and inputs a drive signal for the rotating electrical machine 30 such as a motor generator. Note that the configuration of the other parts is the same as that of the second embodiment, and a description thereof will be omitted.

Hereinafter, the switching operation of the switching unit 6 by the control unit 10b will be specifically described with reference to the flowchart shown in FIG.
In step S300, when the excitation pulse output from the PWM drive unit 4 is applied to the excitation winding of the resolver 2, the control unit 10b detects a drive signal for the rotating electrical machine 30 (YES), the process proceeds to step S301. If not (NO), step S300 is repeated until a drive signal for the rotating electrical machine 30 is detected. The drive signal of the rotating electrical machine 30 is, for example, a Hi or Lo logic signal output by a microcomputer or an integrated circuit for control (ASIC: Application Specific Integrated Circuit) that controls the power generation or driving operation of the rotating electrical machine 30. Conceivable.
In step S301, the control unit 10b transmits a switching signal (Lo in FIG. 2) to the switching unit 6, and the switching unit 6 energizes the current path to the resolver 2 from the PWM drive unit 4 in the excitation unit 3. Switching from the application of the pulse to the application of the excitation voltage of the output sine wave from the excitation means 3 is performed.

As described above, in the third embodiment, when the excitation pulse is applied to the excitation winding of the resolver 2 by the PWM drive unit 4 in the excitation unit 3, the control unit 10 b Is detected, a switching signal is transmitted to the switching means 6 and the excitation means 3 is switched from excitation pulse application by the PWM drive means 4 to sinusoidal excitation voltage application, during power generation where rotation angle detection accuracy is not required, In the standby state in which the operation is stopped, the power consumption of the excitation means 3 can be reduced.
Further, when the rotary electric machine 30 is driven, a sinusoidal excitation voltage is applied to the excitation winding of the resolver 2, so that waveform distortion is suppressed and a highly accurate rotation angle can be detected.

Embodiment 4 FIG.
9 is a block diagram showing a schematic configuration of a rotation angle detection device according to Embodiment 4 of the present invention. FIG. 10 is a circuit diagram showing an example of a circuit configuration of the rotation angle detection device according to Embodiment 4 of the present invention. These are the flowcharts which demonstrate operation | movement of the control means of the rotation angle detection apparatus in Embodiment 4 of this invention.
In the second embodiment, when the excitation pulse is applied to the excitation winding of the resolver 2 by the PWM drive unit 4 in the excitation unit 3, the control unit 10a performs the duty ratio (Duty) of the excitation pulse of the PWM signal. In the fourth embodiment, the excitation means 3 is switched from the excitation pulse application by the PWM drive means 4 to the sine wave excitation voltage application. However, in the fourth embodiment, the PWM in the excitation means 3 is switched. When an excitation pulse is applied to the excitation winding of the resolver 2 by the drive unit 4, the control unit 10c shown in FIG. 9 is configured when the duty ratio (Duty) of the excitation pulse of the PWM signal reaches a predetermined set value. The carrier frequency change means 20 changes the carrier frequency of the PWM drive means 4 to reduce the loss of the excitation means 3 and the influence on the rotation angle detection accuracy. A description will be given of a method to minimize.

  In FIG. 9, the control means 10c reads the excitation pulse output from the PWM drive means 4, and when the duty ratio (Duty) of the excitation pulse of the PWM signal reaches a predetermined set value, the carrier frequency changing means 20 Thus, the carrier frequency of the PWM drive means 4 is changed from the low frequency side to the high frequency side. The carrier frequency changing means 20 has a role of changing the period of the triangular wave in the triangular wave generating circuit 7 corresponding to the carrier frequency of the PWM driving means 4, and a specific configuration of the carrier frequency changing means 20 is, for example, As shown in FIG. 10, a method is conceivable in which the constant of the resistor that sets the period of the triangular wave generating circuit is switched by a signal from the control means 10c.

  In general, when the carrier frequency of PWM control is low, distortion appears in the excitation current waveform of the resolver winding, and the rotation angle detection accuracy decreases. On the other hand, when the carrier frequency of PWM control is increased for the purpose of increasing the rotation angle detection accuracy, there is a problem that switching loss increases and heat generation increases, but the fourth embodiment solves this problem. Is. Note that the configuration of the other parts is the same as that of the second embodiment, and a description thereof will be omitted.

Hereinafter, the carrier frequency changing operation of the carrier frequency changing means 20 by the control means 10c will be specifically described with reference to the flowchart shown in FIG.
In step S400, in a state where the excitation pulse output from the PWM drive unit 4 is applied to the excitation winding of the resolver 2, the control unit 10c controls the pulse width (time) of the excitation pulse of the PWM signal output from the PWM drive unit 4. ), The duty ratio (ON duty) of the excitation pulse of the PWM signal is calculated, and the process proceeds to step 401.

  In step S401, if the calculated duty ratio is greater than or equal to the preset maximum threshold value or less than the minimum threshold value (YES), the control means 10c proceeds to step S402, and otherwise ( If NO, the process returns to step S400. Here, as the threshold value, for example, a method of setting the maximum value or the minimum value of the duty ratio (Duty) that can be realized as the excitation pulse in consideration of the slew rate of the transistor constituting the excitation unit 3 can be considered. Setting is required except when the maximum value of the duty ratio is 100% and the minimum value is 0%.

In step S402, the control means 10c transmits a change signal (Hi in FIG. 10) to the carrier frequency changing means 20, and the carrier frequency changing means 20 changes the carrier frequency of the PWM driving means 4 from the low frequency side to the high frequency side. change.
Note that, as the carrier frequency on the high frequency side, for example, a method of setting the maximum frequency in consideration of the slew rate of the transistors constituting the exciting unit 3 can be considered. Further, as a carrier frequency on the low frequency side (before change), a method of dividing the frequency on the high frequency side after change by an even number can be considered. By dividing by an even number, the duty ratio discontinuity before and after the change of the carrier frequency can be avoided, so that there is an advantage that the excitation waveform does not appear to be distorted when the carrier frequency is changed.

  Although not shown in the flow diagram, as a reverse case to FIG. 11, when the duty ratio exceeds the minimum value and less than the maximum value, the control means 10c sends a change signal (see FIG. 10), the carrier frequency changing means 20 changes the carrier frequency of the PWM driving means 4 from the high frequency side to the low frequency side.

  As described above, in the fourth embodiment, when the excitation pulse is applied to the excitation winding of the resolver 2 by the PWM drive unit 4 in the excitation unit 3, the control unit 10c When the duty ratio reaches a preset maximum value or minimum value of the duty ratio that can be realized as an excitation pulse, a change signal is transmitted to the carrier frequency changing means 20, and the carrier frequency of the PWM driving means 4 is set to a low frequency. Since the waveform is changed from the high-frequency side to the high-frequency side, waveform distortion can be suppressed even at maximal points and minimal points where the rate of change in the sine wave signal is small, and the influence on rotational angle detection accuracy can be suppressed. Except for the point, the carrier frequency is lowered to the low frequency side and the excitation winding of the resolver 2 is excited by PWM drive. It is possible to reduce the quenching loss.

  In the present invention, the embodiments can be freely combined within the scope of the invention, or the embodiments can be appropriately modified and omitted, and the present invention is limited by the above embodiments. is not.

DESCRIPTION OF SYMBOLS 1 Rotation angle detection apparatus, 2 Resolver, 3 Excitation means, 4 PWM drive means, 5 Excitation current detection means, 6 Switching means, 10 Control means

Claims (5)

  A resolver for generating an induction signal in the induction winding by frequency modulation of the magnetic field formed by the excitation signal applied to the excitation winding by rotation of the rotating electrical machine, and a sine wave for applying to the excitation winding of the resolver Excitation means for outputting an excitation voltage, PWM drive means for outputting an excitation pulse of a PWM signal to be applied to the excitation winding of the resolver, a sinusoidal excitation voltage output by the excitation means, and the PWM drive means Switching means for switching the excitation pulse of the PWM signal output by the switch and applying it to the excitation winding of the resolver, and the switching means when the loss can be reduced and the influence on the rotational angle detection accuracy can be suppressed. A rotation angle detecting device comprising a control means for giving a switching signal to.   When the excitation voltage of the sine wave output from the excitation means is applied to the excitation winding of the resolver, the control means holds in advance a loss estimate obtained from the excitation current flowing in the excitation winding of the resolver. The switching means is provided with a signal for switching to the excitation pulse of the PWM signal output from the PWM driving means when the loss is larger than the loss when excited by the output from the PWM driving means. The rotation angle detection device according to claim 1.   When the excitation pulse of the PWM signal output from the PWM drive means is applied to the excitation winding of the resolver, the control means is configured such that the duty ratio of the excitation pulse output from the PWM drive means is preset. 3. The rotation according to claim 1, wherein a signal for switching from the excitation unit to a sine wave excitation voltage output from the excitation unit is provided to the switching unit when the maximum value is below or below a minimum value. Angle detection device.   When the excitation pulse of the PWM signal output from the PWM drive means is applied to the excitation winding of the resolver, the control means detects the drive signal for the rotating electrical machine and The rotation angle detecting device according to any one of claims 1 to 3, wherein a signal for switching to an output sinusoidal excitation voltage is provided from the excitation means. A resolver for generating an induction signal in the induction winding by the frequency modulation of the magnetic field formed by the excitation signal applied to the excitation winding by the rotation of the rotating electrical machine, and a PWM signal for application to the excitation winding of the resolver The PWM drive means for outputting the excitation pulse, the carrier frequency changing means for changing the carrier frequency of the PWM drive means to the low frequency side or the high frequency side, and the duty ratio of the excitation pulse output from the PWM drive means are preset. A rotation angle detecting device comprising: control means for changing the carrier frequency from the low frequency side to the high frequency side by the carrier frequency changing means when the maximum value is equal to or greater than the minimum value or below the minimum value.

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