JP7723550B2 - Excitation signal generation device - Google Patents

Description

The present invention relates to an excitation signal generating device that generates a sine wave excitation signal.

As described in JP 2011-195131 A (Patent Document 1), an excitation signal consisting of a sine wave of a predetermined frequency generated by a resolver excitation circuit is input to the excitation coil of the resolver, which detects the rotation angle of a rotating body. In the resolver excitation circuit, a PWM (Pulse Width Modulation) signal output from a microcomputer is converted into a sine wave containing a DC component (offset voltage) by a CR filter circuit, amplified by an operational amplifier, the DC component is removed by AC coupling, and the excitation signal is generated by phase conversion by an RL circuit.

JP 2011-195131 A

However, if the AC coupling in the resolver excitation circuit shorts out for some reason, the DC component is not removed from the sine wave signal amplified by the operational amplifier, and the offset voltage of the sine wave signal will no longer be 0 V. When the offset voltage of the sine wave signal no longer becomes 0 V, the current output from the resolver excitation circuit increases and exceeds the capabilities of the operational amplifier. As a result, the waveform of the sine wave output from the resolver excitation circuit becomes distorted, potentially reducing the resolver's angle detection accuracy.

The present invention aims to provide an excitation signal generating device that suppresses distortion of the waveform of a sine wave excitation signal even when the AC coupling is shorted.

The excitation signal generator 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 a DC component from the impedance-converted AC signal, and an RL circuit that generates an excitation signal by performing phase conversion on the AC signal from which the DC component has been removed. The AC coupling includes two capacitors of the same capacity connected in series.

According to the present invention, even if the AC coupling in the excitation signal generating device shorts out, distortion of the waveform of the excitation signal, which is a sine wave, can be suppressed.

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 illustrating an example of resolver output. FIG. 2 is a schematic diagram illustrating an example of a resolver excitation circuit. FIG. 2 is a schematic diagram illustrating an example of a CR filter circuit. FIG. 1 is a schematic diagram for explaining the problem of AC coupling in the prior art. FIG. 10 is a schematic diagram showing a modified example of a CR filter circuit. 9 is an explanatory diagram of an excitation signal when a failure occurs in the CR filter circuit shown in FIG. 8 . FIG. 10 is a schematic diagram showing a modified example of a resolver excitation circuit.

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 open 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, which includes 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, which ignites the fuel-air mixture, is attached approximately in the center of the cylinder head 130, which 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 intake valve 132 operating angle while keeping the intake valve 132 operating angle constant by changing the phase of the intake camshaft 200 relative to the crankshaft 140, for example, 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 also vary the phase of at least one of the intake valve 132 and the exhaust valve 134.

The VCR mechanism 190 uses a multi-link mechanism, such as that disclosed in Japanese Patent Application Laid-Open No. 2002-276446, to change the volume of the combustion chamber 160 of the internal combustion engine 100, thereby varying the compression ratio. An example of a VCR mechanism 190 is described below, but other configurations may be used as long as they are capable of performing the required functions.

The crankshaft 140 has multiple journal portions 140A and multiple crankpin portions 140B, with the journal portions 140A rotatably supported by main bearings (not shown) of the cylinder block 110. The crankpin portions 140B are eccentric from the journal portions 140A, and are rotatably connected to the lower link 150A. The lower end of the upper link 150B is rotatably connected to one end of the lower link 150A by a connecting pin 152, and its upper end is rotatably connected to the piston 120 by a piston pin 154. The upper end of the control link 192 is rotatably connected to the other end of the lower link 150A by a connecting pin 194, and its lower end 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, with the lower end of the control link 192 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 that uses an electric motor.

In a 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, i.e., its 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 piston top dead center (TDC) rises or falls, increasing or decreasing the volume of the combustion chamber 160 and changing the compression ratio of the internal combustion engine 100. When the operation of the actuator 198 is stopped at this time, the reciprocating motion of the piston 120 rotates the control link 192 relative to the eccentric cam portion 196A of the control shaft 196, changing the compression ratio toward a lower compression ratio.

As shown in FIG. 2, the VCR mechanism 190 is equipped with a stopper mechanism 210 that restricts the displacement (angle) of the control shaft 196 when it rotates beyond the normal control range RNG1, thereby defining a mechanical rotatable range RNG2. The stopper mechanism 210 includes a substantially fan-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, thereby restricting the displacement of the control shaft 196 when the control shaft 196 rotates beyond the maximum compression ratio (upper limit) or minimum compression ratio (lower limit), which are the normal control range RNG1. Here, the stopper mechanism 210 functions when the control shaft 196 exceeds the normal control range RNG1, so that the first member 210A and the second member 210B do not come into contact during normal control, thereby suppressing, for example, the generation of abnormal noise. Note that the stopper mechanism 210 not only regulates the displacement of the control shaft 196, but can also be used to learn the reference position of the control shaft 196.

The stopper mechanism 210 may be configured to restrict displacement of at least one of the maximum and minimum compression ratio sides with respect to the rotation of the control shaft 196. Furthermore, the stopper mechanism 210 is not limited to a substantially sector-shaped first member 210A and a plate-shaped second member 210B, and may be configured to restrict displacement of the control shaft 196 using two or more members of other shapes.

The VTC mechanism 180 and the VCR mechanism 190 are electronically controlled by a VTC controller 220 and a VCR controller 230, respectively, which each have 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; known networks such as FlexRay (registered trademark) can also be used.

The engine controller 250 receives output signals from a rotational speed sensor 260 that detects the rotational 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 examples of the operating state of the internal combustion engine 100. Here, the load Q of the internal combustion engine 100 can be, for example, a state quantity closely related to torque, such as intake vacuum, intake flow rate, boost pressure, accelerator opening, or throttle opening. The engine controller 250, for example, references a map in which target values appropriate for the rotational 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, respectively, according to the rotational speed Ne and load Q of the internal combustion engine 100. The engine controller 250 then transmits the target angle to the VTC controller 220 and the target compression ratio to the VCR controller 230 via the CAN 240. The engine controller 250 may read the rotation speed Ne and load Q of the internal combustion engine 100 not only from the output signals of the rotation speed sensor 260 and the load sensor 270, but also from another controller (not shown) connected via the CAN 240.

Upon receiving the target angle, the VTC controller 220 performs feedback control of 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. Furthermore, upon receiving the target compression ratio, the VCR controller 230 performs feedback control of 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 below) 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, which is connected to the output shaft of the actuator 198 via a reducer 198A. The VCR controller 230 then uses the output value of the second resolver 290 at engine start as a base point and detects the rotational 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. This is because the first resolver 280 has high resolution when detecting absolute angles but cannot distinguish between, for example, 0° and 360° of the same phase, while the second resolver 290 can detect the absolute angle of the control shaft 196 but has low resolution when detecting absolute angles.

The first resolver 280 and the second resolver 290 output two correlated signals, specifically, a sine wave signal and a cosine wave signal, that correspond to the rotation angle of the rotor. As shown in FIG. 3, the first resolver 280 includes 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. The two-phase output coils 284B and 284C of the stator 284 are positioned with a 90° angular difference. 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 is generated in each of the output coils 284B and 284C, as shown in FIG. 4, which varies depending on the rotation angle (electrical angle) of the rotor. The second resolver 290 has a similar configuration to the first resolver 280, and therefore its description will be omitted. Therefore, in the following description, unless it is necessary 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 determine the rotation angle of the rotor by calculating the arctangent of the sine wave signal and 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 cosine wave signal output from the first resolver 280, and diagnose whether a fault has occurred in the first resolver 280 depending on whether this sum of squares is within a normal range. If the VCR controller 230 diagnoses that a fault has occurred in the first resolver 280, the VCR controller 230 electronically controls the VCR mechanism 190 using the output value of the second resolver 290 instead of the rotation angle determined from the output value of the first resolver 280, using the output value of the second resolver 290 at 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 an excitation signal generating device.

The resolver excitation circuit 300 is configured with a series-connected CR filter circuit 310, a voltage follower circuit 320, an AC coupling 330, and an RL circuit 340. The CR filter circuit 310 generates an AC signal containing a DC component, as shown by B in the figure, from the 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, consisting of a capacitor with a predetermined capacitance, removes the DC component from the AC signal whose impedance has been converted by the voltage follower circuit 320, thereby setting the offset voltage of the AC component to 0 V, as shown by C in the figure. The RL circuit 340 converts the phase of the AC signal from which the DC component has been removed by the AC coupling 330, thereby generating an excitation signal consisting of a sine wave to be supplied to the excitation coil 284A of the first resolver 280.

As shown in FIG. 6, the CR filter circuit 310 is an electrical circuit configured by connecting a first CR filter 312 and a second CR filter 314 in series. The first CR filter 312 is configured to include a resistor 312R having a predetermined electrical resistance value and a capacitor 312C having a predetermined electrical capacitance value. Similarly to the first CR filter 312, the second CR filter 314 is configured to include a resistor 314R having a predetermined electrical resistance value and a capacitor 314C having a predetermined electrical capacitance value.

Specifically, one terminal of resistor 312R in the first CR filter 312 is connected to the VCR controller 230, and the other terminal of resistor 312R in the first CR filter 312 is connected to one terminal of resistor 314R in the second CR filter 314. The other terminal of resistor 314R in the second CR filter 314 is connected to the voltage follower circuit 320. The electrical path between the other terminal of resistor 312R in the first CR filter 312 and one terminal of resistor 314R in the second CR filter 314 is connected to ground GND via capacitor 312C in the first CR filter 312. The electrical path between the other terminal of resistor 314R in the second CR filter 314 and the voltage follower circuit 320 is connected to ground GND via capacitor 314C 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 composed of a first CR filter 312 and a second CR filter 314 connected in series, and converted into an AC signal that includes an offset voltage, which is a DC component.

The voltage follower circuit 320 is an electrical circuit configured by combining an operational amplifier OP, which has a non-inverting input terminal (+), an inverting input terminal (-), and an output terminal, with a resistor 320R having a predetermined electrical resistance. 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 factor of 1, converting the impedance of the AC signal.

The AC coupling 330 is an electrical circuit formed by connecting two capacitors C1 and C2 in series, i.e., an electrical circuit including two capacitors C1 and C2 connected in series. Specifically, one terminal of capacitor C1 is connected to the output terminal of the operational amplifier OP of the voltage follower circuit 320, and the other terminal of capacitor C1 is connected to one terminal of capacitor C2. The other terminal of capacitor C2 is connected to the input terminal of the RL circuit 340. Here, capacitors C1 and C2 desirably have the same capacitance (a predetermined electrical capacitance value) so that even if one of them shorts out, the other capacitor can still perform its required function. Note that "the same capacitance" does not necessarily mean exactly the same capacitance, but rather refers to capacitances that are considered to be approximately the same, including allowable variations, for example.

The RL circuit 340 is an electrical circuit configured by connecting in series a resistor 340R having a predetermined electrical 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 one terminal of the excitation coil 284A of the first resolver 280 via the connector CN. The other terminal of the excitation coil 284A of the first resolver 280 is connected (earthed) to ground via the connector CN.

In the resolver excitation circuit 300, the electrical path between the VCR controller 230 and the CR filter circuit 310 is connected to ground GND via resistor R1, which has a predetermined electrical resistance. Therefore, resistor R1 functions as a pull-down resistor, ensuring that the minimum voltage of the PWM signal output from the VCR controller 230 is 0 V.

In addition, 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 R2, which has a predetermined electrical resistance. Therefore, resistor R2 functions as a pull-down resistor, ensuring that the minimum potential of the AC signal output from the voltage follower circuit 320 is 0 V.

Furthermore, in the resolver excitation circuit 300, the electrical path between the RL circuit 340 and the connector CN is connected to ground GND via two Zener diodes ZD connected in series and in reverse. Therefore, the Zener diodes ZD absorb surge voltages (back electromotive forces) generated in the excitation coil 284A of the first resolver 280, preventing excessive current from flowing through each electrical element, for example.

In the resolver excitation circuit 300 of the prior art, as shown in Figure 7, the AC coupling 330 consists of a single capacitor. In this case, if the AC coupling 330 shorts out for some reason, the DC component cannot be removed from the AC signal that has been impedance-converted by the voltage follower circuit 320, and an offset voltage remains superimposed on the AC signal, as shown by C in the figure. As a result, the current output from the voltage follower circuit 320 increases and exceeds the capacity of the operational amplifier OP, causing the waveform of the sine wave output from the resolver excitation circuit 300 to become distorted, potentially reducing the resolver's angle detection accuracy.

However, in the resolver excitation circuit 300 of this embodiment, the AC coupling 330 is configured to include two capacitors C1 and C2 connected in series, so even if one of the capacitors shorts out, the DC component can be removed by the other capacitor. Therefore, even if one of the capacitors shorts out, the current output from the voltage follower circuit 320 does not increase, and the waveform of the sine wave output from the resolver excitation circuit 300 can be prevented from becoming distorted. Note that, since it is extremely rare for both capacitors C1 and C2 to short out at the same time, this is usually not something that needs to be taken into consideration.

FIG. 8 shows an example of a modified example of the CR filter circuit 310. In FIG.
6 is used as a basic configuration, and as shown in Fig. 8, 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 resistance value.

In the CR filter circuit 310 shown in FIG. 8, if any of resistors 312R, 314R, and R3 is broken, or any of capacitors 312C, 314C, and C3 is shorted, an AC signal cannot be generated from the PWM signal, and the excitation signal always remains at 0 [V]. If resistor 312R is shorted, as shown in FIG. 9, the amplitude V1 [V] of the excitation signal increases compared to normal operation, and the excitation signal period is delayed by T1 [μs] per half cycle. If either resistor 314R or R3 is shorted, as shown in FIG. 9, the amplitude of the excitation signal becomes V2 [V], which is smaller than V1, and the excitation signal period becomes the same as normal operation. If either capacitor 312C or C3 is broken, as shown in FIG. 9, the amplitude of the excitation signal becomes V3 [V], which is smaller than V1 but larger than V2, and the excitation signal period is delayed by T3 [μs], which is shorter than T1 per half cycle. When capacitor 314C is disconnected, as shown in Figure 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.

Therefore, by determining whether the amplitude of the excitation signal exceeds a predetermined threshold, it is possible to detect whether a fault has occurred in resistors 312R, 314R, and R3 or capacitors 312C, 314C, and C3 of the CR filter circuit 310. If any of resistors 312R, 314R, and R3 is broken, or if any of capacitors 312C, 314C, and C3 is shorted, the amplitude of the excitation signal will always be 0 [V], as described above, and a fault can be detected without checking the amplitude of the excitation signal. To prevent erroneous diagnosis by taking into account variations, the predetermined threshold for fault detection is set to, for example, the amplitude of the excitation signal when either capacitor 312C or C3 is broken. In this case, if resistor 312R is shorted, the amplitude of the excitation signal will exceed the predetermined threshold, allowing for fault detection. If either resistor 314R or R3 is shorted, the amplitude of the excitation signal will remain within the predetermined threshold, and therefore a fault cannot be detected. If either capacitor 312C or C3 is disconnected, the amplitude of the excitation signal will be close to the predetermined threshold, making it possible that the fault cannot be detected. Furthermore, if capacitor 314C is disconnected, the amplitude of the excitation signal will exceed the predetermined threshold, making it possible to detect the fault.

Next, consider the rotation angle detection accuracy of the first resolver 280 in the resolver excitation circuit 300 equipped with the CR filter circuit 310 shown in Figure 8. Assume that the allowable rotation angle error is within a range corresponding to a value slightly larger than the excitation signal period delay T3 compared to normal operation. In this case, if resistor 312R is shorted, the excitation signal period will be delayed by T1 [μs] per half period, making the rotation angle error unacceptable. If either resistor 314R or R3 is shorted, the excitation signal period will be delayed by T3 [μs] per half period, but this is within the allowable range, making the rotation angle error tolerable. If either capacitor 312C or C3 is disconnected, the excitation signal period will be the same as normal operation, making the rotation angle error tolerable. If capacitor 314C is disconnected, the excitation signal period will be the same as normal operation, making the rotation angle error tolerable.

If resistor 312R is shorted, it is not possible to tolerate errors in the rotation angle, but the fault can be detected, so it is possible to deal with this by, for example, switching to fail-safe mode. If either resistor 314R or R3 is shorted, it is not possible to detect the fault, but it is possible to tolerate errors in the rotation angle, so there is little impact on control. If either capacitor 312C or C3 is disconnected, it may not be possible to detect the fault, but it is possible to tolerate errors in the rotation angle, so there is little impact on control. If capacitor 314C is disconnected, it is possible to detect the fault and it is possible to tolerate errors in the rotation angle, so there is little impact on control.

Therefore, even if a failure occurs in any of resistors 312R, 314R, R3 or capacitors 312C, 314C, 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 minimizing the impact on control.

If there is sufficient output capacity for the voltage follower circuit 320, as shown in FIG. 10, the resolver excitation circuit 300 may output an excitation signal to both the first resolver 280 and the second resolver 290, rather than just one of them. In this case, the electrical path between resistor R2 and AC coupling 330 is branched, and the excitation signal is output to the second resolver 290 via the AC coupling 330', RL circuit 340', Zener diode ZD', and connector CN' arranged there. In other words, two parallel systems are provided for the voltage follower circuit 320: the AC coupling 330, RL circuit 340, and Zener diode ZD for the first resolver 280, and the AC coupling 330', RL circuit 340', and Zener diode ZD' for the second resolver 290.

In this way, excitation signals can be output from a single resolver excitation circuit 300 to both the first resolver 280 and the second resolver 290, which reduces costs and installation space compared to a system equipped with two resolver excitation circuits 300. Furthermore, by providing two parallel systems of AC couplings 330, 330', RL circuits 340, 340', and Zener diodes ZD, ZD', it is possible to output excitation signals suited to the characteristics of each resolver, even if the characteristics of the first resolver 280 and the second resolver 290 are different.

It goes without saying that the electrical resistance values of the resistors, capacitance values of the capacitors, and inductance values of the coils used in each of the embodiments described above can be selected appropriately so that they work together to perform the required functions.

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

For example, the resolver excitation circuit 300 may be mounted on the board of the VCR controller 230. Furthermore, the resolver excitation circuit 300 is not limited to being provided in the VCR controller 230 that electronically controls the VCR mechanism 190, but may also be provided in the VTC controller 220 that electronically controls the VTC 180, or in another controller (not shown).

300...Resolver excitation circuit (excitation signal generator) 310...CR filter circuit 320...Voltage follower circuit 330...AC coupling 340...RL circuit C1...Capacitor C2...Capacitor

Claims (4)

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 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 AC coupling includes two capacitors of the same capacitance connected in series.
Excitation signal generation device. two systems of the AC coupling and the RL circuit are provided for the voltage follower circuit, and the two systems of the AC coupling and the RL circuit are connected in parallel with each other;
The excitation signal generating device according to claim 1 . The excitation signal generated by the RL circuit is output to a resolver.
3. The excitation signal generating device according to claim 1 or 2. The pulse width modulation signal is output from a microcomputer.
4. The excitation signal generating device according to claim 1.