JP7518745B2 - Resolver Exciter - Google Patents

Description

The present invention relates to a resolver excitation device that excites a resolver.

A resolver that detects the rotation angle of a rotating body includes a rotor that rotates integrally with the rotating body, and a stator that includes a one-phase excitation coil and a two-phase output coil. As shown in JP 2011-195131 A (Patent Document 1), an excitation signal consisting of a sine wave of a predetermined frequency is input to the excitation coil of the resolver. This excitation signal is generated from a PWM (Pulse Width Modulation) signal output from a microcomputer by an excitation circuit having a CR filter circuit in which two primary CR filters are cascaded (connected in series). Then, the rotation angle of the rotating body is obtained by calculating the arctangent of two correlated signals, i.e., a sine wave signal and a cosine wave signal, output from the two-phase output coil of the resolver as a result of excitation of the excitation coil by the excitation signal. In addition, by determining whether the amplitude of the excitation signal output from the excitation circuit exceeds a predetermined threshold, it is possible to detect whether a fault such as a break or short circuit has occurred in the resistor or capacitor of the CR filter circuit.

JP 2011-195131 A

However, in an excitation circuit having such a CR filter circuit, if an open circuit occurs in the capacitor of the first-stage primary CR filter or if a short circuit occurs in the resistor of the second-stage primary CR filter, the amplitude of the excitation signal output from the excitation circuit may not exceed a predetermined threshold for diagnosing a fault, and the fault may not be detected.

The present invention aims to provide a resolver excitation device that can detect a fault or reduce the effect of a fault that may affect angle detection accuracy, even if a break or short occurs in the resistor or capacitor of a CR filter circuit.

The resolver excitation device includes a CR filter circuit that generates an AC signal from a pulse width modulated signal, a voltage follower circuit that converts the impedance of the generated AC signal, an AC coupling that removes DC components from the impedance-converted AC signal, and an RL circuit that transforms the AC signal from which the DC components have been removed to generate an excitation signal. The CR filter circuit includes a first CR filter and a second CR filter that are connected in series, a resistor disposed between the first CR filter and the second CR filter, and a capacitor having one end connected between the first CR filter and the resistor and the other end connected to ground.

According to the present invention, even if an open circuit or short circuit occurs in the resistor or capacitor of a CR filter circuit, which affects the angle detection accuracy, the failure can be detected or the effect of the failure can be reduced.

1 is a system diagram showing an example of an internal combustion engine mounted on a vehicle. FIG. 4 is a partial enlarged view showing an example of a stopper mechanism. FIG. 2 is a structural diagram illustrating an example of a resolver. FIG. 4 is an explanatory diagram showing an example of a resolver output. FIG. 1 is a schematic diagram illustrating an example of a resolver excitation device. FIG. 1 is a schematic diagram showing an example of a CR filter circuit in the prior art. 1 is an explanatory diagram of an excitation signal when a failure occurs in a CR filter circuit in the prior art. FIG. 2 is a schematic diagram illustrating an example of a CR filter circuit according to the present embodiment. 5 is an explanatory diagram of an excitation signal when a failure occurs in the CR filter circuit in the embodiment. FIG.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows an example of an internal combustion engine 100 mounted on a vehicle.

The internal combustion engine 100 has a cylinder block 110, a piston 120 reciprocally inserted into a cylinder bore 112 of the cylinder block 110, a cylinder head 130 in which an intake port 130A and an exhaust port 130B are formed, and an intake valve 132 and an exhaust valve 134 that open and close the opening ends of the intake port 130A and the exhaust port 130B.

The piston 120 is connected to the crankshaft 140 via a connecting rod 150 including a lower link 150A and an upper link 150B. A combustion chamber 160 is formed between the crown surface 120A of the piston 120 and the underside of the cylinder head 130. An ignition plug 170 that ignites the mixture of fuel and air is attached approximately in the center of the cylinder head 130 that forms the combustion chamber 160.

The internal combustion engine 100 also includes a variable valve timing control (VTC) mechanism 180 that changes the phase of the opening timing of the intake valve 132 relative to the crankshaft 140, and a variable compression ratio (VCR) mechanism 190 that changes the volume of the combustion chamber 160 to change the compression ratio.

The VTC mechanism 180 advances or retards the center phase of the operating angle of the intake valve 132 while keeping the operating angle of the intake valve 132 constant by changing the phase of the intake camshaft 200 relative to the crankshaft 140 using an actuator such as an electric motor (not shown). Note that the VTC mechanism 180 is not limited to varying the phase of the intake valve 132, and may vary the phase of at least one of the intake valve 132 and the exhaust valve 134.

The VCR mechanism 190 changes the volume of the combustion chamber 160 of the internal combustion engine 100 by using a multi-link mechanism, such as that disclosed in Japanese Patent Application Laid-Open No. 2002-276446, to vary the compression ratio. An example of the VCR mechanism 190 is described below.

The crankshaft 140 has a plurality of journal portions 140A and a plurality of crank pin portions 140B, and the journal portion 140A is rotatably supported by a main bearing (not shown) of the cylinder block 110. The crank pin portion 140B is eccentric from the journal portion 140A, and the lower link 150A is rotatably connected to the crank pin portion 140B. The lower end side of the upper link 150B is rotatably connected to one end of the lower link 150A by a connecting pin 152, and the upper end side is rotatably connected to the piston 120 by a piston pin 154. The upper end side of the control link 192 is rotatably connected to the other end of the lower link 150A by a connecting pin 194, and the lower end side is rotatably connected to the lower part of the cylinder block 110 via a control shaft 196. In detail, the control shaft 196 is rotatably supported by the cylinder block 110 and has an eccentric cam portion 196A that is eccentric from the center of rotation, and the lower end side of the control link 192 is rotatably fitted into this eccentric cam portion 196A. The rotational position of the control shaft 196 is controlled by an actuator 198 for compression ratio control using an electric motor.

In the VCR mechanism 190 using such a multi-link mechanism, when the control shaft 196 is rotated by the actuator 198, the center position of the eccentric cam portion 196A, that is, the relative position with respect to the cylinder block 110, changes. As a result, when the rocking support position of the lower end of the control link 192 changes, the position of the piston 120 at the piston top dead center (TDC) becomes higher or lower, increasing or decreasing the volume of the combustion chamber 160, and changing the compression ratio of the internal combustion engine 100. At this time, when the operation of the actuator 198 is stopped, the reciprocating motion of the piston 120 rotates the control link 192 relative to the eccentric cam portion 196A of the control shaft 196, and the compression ratio shifts to the lower compression ratio side.

2, the VCR mechanism 190 is provided with a stopper mechanism 210 that regulates the displacement (angle) of the control shaft 196 when it rotates beyond the normal control range RNG1 to define a mechanical rotatable range RNG2. The stopper mechanism 210 has a substantially sector-shaped first member 210A, the essential portion of which is fixed to the control shaft 196, and a plate-shaped second member 210B, which is fixed to the cylinder block 110. The first member 210A rotates integrally with the control shaft 196. The second member 210B abuts against one of the two sides that define the central angle of the first member 210A when the control shaft 196 rotates beyond the maximum compression ratio (upper limit) or the minimum compression ratio (lower limit), which is the normal control range RNG1, and regulates the displacement of the control shaft 196. Here, the stopper mechanism 210 functions when the control shaft 196 exceeds the normal control range, so that the first member 210A and the second member 210B do not come into contact with each other under normal control, and it is possible to suppress, for example, the generation of abnormal noise. Note that the stopper mechanism 210 is not only used to regulate the displacement of the control shaft 196, but also to learn the reference position of the control shaft 196.

The stopper mechanism 210 may be capable of restricting the displacement of at least one of the maximum compression ratio side and the minimum compression ratio side with respect to the rotation of the control shaft 196. In addition, the stopper mechanism 210 is not limited to the substantially sector-shaped first member 210A and the plate-shaped second member 210B, but may be capable of restricting the displacement of the control shaft 196 using two or more members having other shapes.

The VTC mechanism 180 and the VCR mechanism 190 are electronically controlled by a VTC controller 220 and a VCR controller 230, each of which has a built-in microcomputer. The VTC controller 220 and the VCR controller 230 are connected to an engine controller 250, which has a built-in microcomputer and electronically controls the internal combustion engine 100, via, for example, a Controller Area Network (CAN) 240, which is an example of an in-vehicle network. Therefore, the VTC controller 220, the VCR controller 230, and the engine controller 250 can send and receive any data using the CAN 240. Note that the in-vehicle network is not limited to the CAN 240, and any known network such as FlexRay (registered trademark) can be used.

The engine controller 250 receives output signals from a rotation speed sensor 260 that detects the rotation speed Ne of the internal combustion engine 100 and a load sensor 270 that detects the load Q of the internal combustion engine 100 as an example of the operating state of the internal combustion engine 100. Here, as the load Q of the internal combustion engine 100, for example, a state quantity closely related to torque, such as intake negative pressure, intake flow rate, supercharging pressure, accelerator opening, and throttle opening, can be used. The engine controller 250, for example, refers to a map in which target values suitable for the rotation speed and load are set, and determines the target angle of the VTC mechanism 180 and the target compression ratio of the VCR mechanism 190 according to the rotation speed Ne and load Q of the internal combustion engine 100. Then, the engine controller 250 transmits the target angle and the target compression ratio to the VTC controller 220 and the VCR controller 230, respectively, via the CAN 240. In addition, the engine controller 250 may read the rotation speed Ne and load Q of the internal combustion engine 100 from another controller (not shown) connected via the CAN 240, rather than from the output signals of the rotation speed sensor 260 and the load sensor 270.

The VTC controller 220, which has received the target angle, feedback controls the drive current output to the actuator of the VTC mechanism 180 so that the actual angle (actual angle) detected by a sensor (not shown) approaches the target angle. The VCR controller 230, which has received the target compression ratio, feedback controls the drive current output to the actuator 198 of the VCR mechanism 190 so that the actual compression ratio (actual compression ratio) detected by a compression ratio sensor (described later) approaches the target compression ratio. In this way, the VTC mechanism 180 and the VCR mechanism 190 are each controlled to a target value according to the operating state of the internal combustion engine 100.

The compression ratio sensor that detects the actual compression ratio of the internal combustion engine 100 includes a first resolver 280 that detects the relative angle of the output shaft of the actuator 198, and a second resolver 290 that detects the absolute angle of the control shaft 196 connected to the output shaft of the actuator 198 via a reducer 198A. The VCR controller 230 detects the rotation angle of the control shaft 196, in other words, the compression ratio of the internal combustion engine 100, from the output value of the first resolver 280, based on the output value of the second resolver 290 at the time of engine start. This is because the first resolver 280 has high resolution when detecting relative angles, but cannot distinguish between, for example, 0° and 360° of the same phase, and the second resolver 290 can detect the absolute angle of the control shaft 196, but has low resolution when detecting the absolute angle.

The first resolver 280 and the second resolver 290 output two signals, specifically, a sine wave signal and a cosine wave signal, that are correlated according to the rotation angle of the rotor. As shown in FIG. 3, the first resolver 280 has a rotor 282 that rotates integrally with the rotor, and a stator 284 wound with a one-phase excitation coil 284A and two-phase output coils 284B and 284C. Here, the two-phase output coils 284B and 284C of the stator 284 are arranged with an angle difference of 90°. Then, when an excitation signal consisting of an AC current is applied to the excitation coil 284A of the stator 284, a two-phase voltage consisting of a sine wave signal and a cosine wave signal that changes according to the rotation angle (electrical angle) of the rotor is generated in each of the output coils 284B and 284C, as shown in FIG. 4. The second resolver 290 has a similar configuration to the first resolver 280, so its description will be omitted. Therefore, in the following description, when there is no need to distinguish between the first resolver 280 and the second resolver 290, the description of the first resolver 280 will be taken to include the description of the second resolver 290.

The VCR controller 230 can obtain the rotation angle of the rotor by calculating the arctangent of the sine wave signal and the cosine wave signal output from the first resolver 280. The VCR controller 230 can also calculate the sum of squares (sin ² θ+cos ² θ) of the sine wave signal and the cosine wave signal output from the first resolver 280, and can determine whether or not a failure has occurred in the first resolver 280 depending on whether or not this sum of squares is within a normal range. If the VCR controller 230 determines that a failure has occurred in the first resolver 280, it controls the VCR mechanism 190 using the output value of the second resolver 290 instead of the rotation angle obtained from the output value of the first resolver 280 with the output value of the second resolver 290 at the time of engine start as the base point.

Figure 5 shows an example of a resolver excitation circuit 300 that outputs an excitation signal to the first resolver 280. The resolver excitation circuit 300 is an example of a resolver excitation device.

The resolver excitation circuit 300 includes a CR filter circuit 310, a voltage follower circuit 320, an AC coupling 330, and an RL circuit 340, which are connected in series. The CR filter circuit 310 generates an AC signal including an offset voltage (DC component) as shown by B in the figure from a PWM signal output from the VCR controller 230 as shown by A in the figure. The voltage follower circuit 320 converts the impedance of the AC signal generated by the CR filter circuit 310, allowing a large current to flow without changing the voltage (amplitude) of the AC signal. The AC coupling 330 is made of a capacitor having a predetermined capacitance value, and removes the DC component from the AC signal impedance-converted by the voltage follower circuit 320, thereby making the offset voltage of the AC component 0 V as shown by C in the figure. The RL circuit 340 generates an excitation signal to be supplied to the excitation coil 284A of the first resolver 280 by phase-converting the AC signal from which the DC component has been removed by the AC coupling 330.

The voltage follower circuit 320 is an electrical circuit formed by combining an operational amplifier OP having a non-inverting input terminal (+), an inverting input terminal (-), and an output terminal, and a resistor 320R having a predetermined electrical resistance value. Specifically, the non-inverting input terminal (+) of the operational amplifier OP is connected to the output terminal of the CR filter circuit 310. The output terminal of the operational amplifier OP is connected to one terminal of the AC coupling 330, and is also branched off midway and connected to the inverting input terminal (-) of the operational amplifier OP via resistor 320R. Therefore, the voltage follower circuit 320 functions as a non-inverting amplifier circuit with an amplification degree of 1, and converts the impedance of the AC signal.

The RL circuit 340 is an electric circuit configured by connecting in series a resistor 340R having a predetermined electric resistance value and a coil 340L having a predetermined inductance value. Specifically, one terminal of the resistor 340R is connected to the other terminal of the AC coupling 330, and the other terminal of the resistor 340R is connected to one terminal of the coil 340L. The other terminal of the coil 340L is connected to a connector terminal 350 that detachably connects a harness that supplies an excitation signal to one terminal of the excitation coil 284A of the first resolver 280.

In the resolver excitation circuit 300, the electrical path between the voltage follower circuit 320 and the AC coupling 330 is connected to ground GND via resistor 360 having a predetermined electrical resistance value. The other terminal of the excitation coil 284A of the first resolver 280 is connected to an electrical path between resistor 360 and ground GND via connector terminal 350. Therefore, the resistor 360 functions as a pull-down resistor, and it is guaranteed that the AC signal output from the voltage follower circuit 320 has a minimum potential of 0V.

FIG. 6 shows an example of a CR filter circuit 310 in the prior art.
The CR filter circuit 310 is an electric circuit configured by connecting in series a first CR filter 312 including a resistor R1 having a predetermined electric resistance value and a capacitor C1 having a predetermined electric capacitance value, and a second CR filter 314 including a resistor R2 having a predetermined electric resistance value and a capacitor C2 having a predetermined electric capacitance value.

Specifically, one terminal of the resistor R1 in the first CR filter 312 is connected to the VCR controller 230, and the other terminal of the resistor R1 in the first CR filter 312 is connected to one terminal of the resistor R2 in the second CR filter 314. The other terminal of the resistor R2 in the second CR filter 314 is connected to the non-inverting input terminal (+) of the operational amplifier OP in the voltage follower circuit 320. The electric path between the other terminal of the resistor R1 in the first CR filter 312 and one terminal of the resistor R2 in the second CR filter 314 is connected to ground GND via the capacitor C1 in the first CR filter 312. The electric path between the other terminal of the resistor R2 in the second CR filter 314 and the voltage follower circuit 320 is connected to ground GND via the capacitor C2 in the second CR filter 314.

Therefore, the PWM signal output from the VCR controller 230 is smoothed by the CR filter circuit 310, which is made up of a first CR filter 312 and a second CR filter 314 connected in series, and is converted into an AC signal that includes an offset voltage, which is a DC component.

In the CR filter circuit 310 of the conventional technology, if resistor R1 is open, resistor R2 is open, capacitor C1 is shorted, or capacitor C2 is shorted, an AC signal cannot be generated from the PWM signal, and the excitation signal always becomes 0 V. If resistor R1 is shorted or capacitor C2 is open, as shown in FIG. 7, the amplitude of the excitation signal becomes larger by V1 [V] and the period of the excitation signal is delayed by T1 [μs] in half a cycle compared to normal. If resistor R2 is shorted or capacitor C1 is open, as shown in FIG. 7, the amplitude of the excitation signal becomes V2 [V], which is smaller than V1, and the period of the excitation signal is delayed by T2 [μs], which is shorter than T1 in half a cycle compared to normal.

As explained in the background art, by determining whether the amplitude of the excitation signal exceeds a predetermined threshold, it is possible to detect whether a fault has occurred in the resistors R1 and R2 or the capacitors C1 and C2 of the CR filter circuit 310. If the resistor R1 is disconnected, the resistor R2 is disconnected, the capacitor C1 is shorted, or the capacitor C2 is shorted, the amplitude of the excitation signal is always 0V as described above, so that the fault can be detected without checking the amplitude of the excitation signal. As the predetermined threshold for detecting a fault, it is assumed that, for example, the vicinity of the amplitude of the excitation signal when the resistor R2 is shorted or the capacitor C1 is shorted is adopted in order to prevent erroneous diagnosis in consideration of variations. In this case, if the resistor R1 is shorted or the capacitor C2 is disconnected, the amplitude of the excitation signal exceeds the predetermined threshold, so that the fault can be detected. However, if the resistor R2 is shorted or the capacitor C1 is disconnected, the amplitude of the excitation signal is near the predetermined threshold, so that it is possible that the fault cannot be detected.

Next, consider the rotation angle detection accuracy of the first resolver 280. Assume that the allowable rotation angle error is within a range that corresponds to a value slightly smaller than the period delay T2 of the excitation signal compared to normal times. In this case, if resistor R1 is shorted or capacitor C2 is disconnected, the period of the excitation signal is delayed by T1 [μs] per half period, and therefore no error in the rotation angle can be tolerated. Also, if resistor R2 is shorted or capacitor C1 is disconnected, the period of the excitation signal is delayed by T2 [μs] per half period, and therefore no error in the rotation angle can be tolerated.

If resistor R1 is shorted or capacitor C2 is disconnected, an error in the rotation angle cannot be tolerated, but since a fault can be detected as described above, it is possible to deal with this by, for example, switching to a fail-safe mode. However, if resistor R2 is shorted or capacitor C1 is disconnected, an error in the rotation angle cannot be tolerated and there is a possibility that a fault cannot be detected, so, for example, it is not possible to switch to the fail-safe mode, and unexpected control may occur.

As shown in FIG. 8, the CR filter circuit 310 is modified so that even if a fault such as a break or short occurs in the resistor or capacitor, it can be detected, or an error in the rotation angle can be tolerated, thereby preventing unexpected control, for example.

The CR filter circuit 310 in this embodiment is based on the CR filter circuit 310 in the prior art, and a resistor R3 having a predetermined electrical resistance value is disposed in the electrical path located between the first CR filter 312 and the second CR filter 314. In addition, the electrical path located between the first CR filter 312 and the resistor R3 is connected to ground GND via a capacitor C3 having a predetermined electrical capacitance value.

The PWM signal output from the VCR controller 230 is smoothed by the CR filter circuit 310, which is made up of a first CR filter 312 and a second CR filter 314 connected in series and has a resistor R3 and a capacitor C3 placed at a specified location, and is converted into an AC signal that includes an offset voltage, which is a DC component.

In the CR filter circuit 310 in this embodiment, if the resistor R1 is disconnected, the resistor R2 is disconnected, the resistor R3 is disconnected, the capacitor C1 is shorted, the capacitor C2 is shorted, or the capacitor C3 is shorted, an AC signal cannot be generated from the PWM signal, and the excitation signal always becomes 0V. If the resistor R1 is shorted, as shown in FIG. 9, the amplitude of the excitation signal becomes larger by V1 [V] and the period of the excitation signal is delayed by T1 [μs] in a half cycle compared to the normal state. If the resistor R2 is shorted or the resistor R3 is shorted, as shown in FIG. 9, the amplitude of the excitation signal becomes V2 [V] smaller than V1 and the period of the excitation signal becomes equal to the normal state. If the capacitor C1 is disconnected or the capacitor C3 is disconnected, as shown in FIG. 9, the amplitude of the excitation signal becomes V3 [V] smaller than V1 and larger than V2 and the period of the excitation signal is delayed by T3 [μs] shorter than T1 in a half cycle compared to the normal state. When capacitor C2 breaks down, as shown in FIG. 9, the amplitude of the excitation signal becomes V4 [V], which is smaller than V1 and larger than V3, compared to normal conditions, and the period of the excitation signal becomes the same as normal conditions.

In this embodiment, as in the conventional technology, by determining whether the amplitude of the excitation signal exceeds a predetermined threshold, it is possible to detect whether a fault has occurred in the resistors R1, R2, and R3 or the capacitors C1, C2, and C3 of the CR filter circuit 310. When the resistor R1 is disconnected, the resistor R2 is disconnected, the resistor R3 is disconnected, the capacitor C1 is shorted, the capacitor C2 is shorted, or the capacitor C3 is shorted, the amplitude of the excitation signal is always 0 V as described above, so that the fault can be detected without checking the amplitude of the excitation signal. As the predetermined threshold for detecting the fault, for example, the vicinity of the amplitude of the excitation signal when the capacitor C1 is disconnected or the capacitor C3 is disconnected is adopted in order to prevent erroneous diagnosis in consideration of variations. At this time, when the resistor R1 is shorted, the amplitude of the excitation signal exceeds the predetermined threshold, so that the fault can be detected. When the resistor R2 is shorted or the resistor R3 is shorted, the amplitude of the excitation signal is within the predetermined threshold, so that the fault cannot be detected. If capacitor C1 or capacitor C3 is broken, the amplitude of the excitation signal will be close to a certain threshold, so it may not be possible to detect the fault. If capacitor C2 is broken, the amplitude of the excitation signal will exceed the certain threshold, so it is possible to detect the fault.

Next, in this embodiment, the rotation angle detection accuracy of the first resolver 280 will be considered. It is assumed that the allowable rotation angle error is within a range corresponding to a value slightly larger than the period delay T3 of the excitation signal compared to normal. In this case, if resistor R1 is shorted, the period of the excitation signal is delayed by T1 [μs] per half period, so the error in the rotation angle is not allowable. If resistor R2 or resistor R3 is shorted, the period of the excitation signal is delayed by T3 [μs] per half period, but this is within the allowable range, so the error in the rotation angle can be allowed. If capacitor C1 or capacitor C3 is disconnected, the period of the excitation signal is equivalent to that in normal times, so the error in the rotation angle can be allowed. If capacitor C2 is disconnected, the period of the excitation signal is equivalent to that in normal times, so the error in the rotation angle can be allowed.

If resistor R1 is shorted, it is not possible to tolerate an error in the rotation angle, but since a fault can be detected, it is possible to deal with this by, for example, switching to a fail-safe mode. If resistor R2 or resistor R3 is shorted, it is not possible to detect a fault, but since an error in the rotation angle can be tolerated, there is little impact on control. If capacitor C1 or capacitor C3 is disconnected, it may not be possible to detect a fault, but since an error in the rotation angle can be tolerated, there is little impact on control. If capacitor C2 is disconnected, it is possible to detect a fault and since an error in the rotation angle can be tolerated, there is little impact on control.

Therefore, even if a failure occurs in any of the resistors R1, R2, and R3 or the capacitors C1, C2, and C3 of the CR filter circuit 310, the failure can be detected, or the error in the rotation angle caused by the failure can be tolerated, thereby suppressing the effect on control.

A person skilled in the art will easily understand that new embodiments can be created by omitting parts of the technical ideas of the various embodiments described above, combining parts of them as appropriate, or replacing parts of them with well-known technology.

230 VCR controller (microcomputer)
300 Resolver excitation circuit (resolver excitation device)
310 CR filter circuit 312 First CR filter 314 Second CR filter 320 Voltage follower circuit 330 AC coupling 340 RL circuit 360 Resistor OP Operational amplifier R3 Resistor C3 Capacitor GND Ground

Claims (4)

a CR filter circuit for generating an AC signal from a pulse width modulated signal;
a voltage follower circuit that converts the impedance of the generated AC signal;
an AC coupling for removing a DC component from the impedance-converted AC signal;
an RL circuit that generates an excitation signal by performing phase conversion on the AC signal from which the DC component has been removed;
Equipped with
the CR filter circuit includes a first CR filter and a second CR filter connected in series, a resistor disposed between the first CR filter and the second CR filter, and a capacitor having one end connected between the first CR filter and the resistor and the other end connected to ground;
Resolver excitation device. a resistor having one end connected between the voltage follower circuit and the AC coupling and the other end connected to the ground;
The resolver excitation device according to claim 1. The voltage follower circuit is a non-inverting amplifier circuit using an operational amplifier.
3. The resolver excitation device according to claim 1 or 2. The pulse width modulation signal is output from a microcomputer.
The resolver excitation device according to any one of claims 1 to 3.