Excitation signal generating device

Abstract

To suppress the collapse of waveform of an excitation signal comprised of a sinusoidal wave even when an AC coupling is short-circuited in an excitation signal generation device.SOLUTION: A resolver excitation circuit 300 cited as an example of an excitation signal generation device comprises: a CR filter circuit 310 generating an AC signal from a pulse width-modulated (PWM) signal; a voltage follower circuit 320 converting the impedance of the generated AC signal; an AC coupling 330 removing a DC component from the impedance-converted AC signal; and an RL circuit 340 phase-converting the AC signal from which the DC component has been removed, thereby generating an excitation signal. The AC coupling 330 is comprised by including two capacitors C1 and C2 which are connected in series.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an excitation signal generating device that generates a sine wave excitation signal. [Background technology]

[0002] As described in Japanese Patent Laid-Open Publication No. 2011-195131 (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 a resolver that 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, and this is then amplified by an operational amplifier, the DC component is removed by AC coupling, and the phase is converted by an RL circuit to generate an excitation signal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-195131 Summary of the Invention [Problem to be solved by the invention]

[0004] 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 does not become 0 [V]. When the offset voltage of the sine wave signal does not become 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, which could reduce the angle detection accuracy of the resolver.

[0005] Therefore, an object of the present invention is to provide an excitation signal generating device that suppresses distortion of the waveform of an excitation signal consisting of a sine wave even when AC coupling is shorted. [Means for solving the problem]

[0006] The excitation signal generating device includes a CR filter circuit that generates an AC signal from a pulse width modulation 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. Same capacity It contains two capacitors. [Effects of the Invention]

[0007] According to the present invention, even if AC coupling is shorted in an excitation signal generating device, it is possible to prevent the waveform of the excitation signal, which is a sine wave, from being distorted. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a system diagram showing an example of an internal combustion engine mounted on a vehicle. [Figure 2] FIG. 4 is a partial enlarged view showing an example of a stopper mechanism. [Figure 3] FIG. 2 is a structural diagram illustrating an example of a resolver. [Figure 4] FIG. 4 is an explanatory diagram illustrating an example of resolver output. [Figure 5] FIG. 2 is a schematic diagram illustrating an example of a resolver excitation circuit. [Figure 6] FIG. 1 is a schematic diagram illustrating an example of a CR filter circuit. [Figure 7] FIG. 1 is a schematic diagram for explaining the problem of AC coupling in the prior art. [Figure 8] FIG. 10 is a schematic diagram showing a modified example of a CR filter circuit. [Figure 9]9 is an explanatory diagram of an excitation signal when a fault occurs in the CR filter circuit shown in FIG. 8. [Figure 10] FIG. 10 is a schematic diagram showing a modified example of a resolver excitation circuit. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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.

[0010] 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.

[0011] Piston 120 is connected to crankshaft 140 via connecting rod 150, which includes lower link 150A and upper link 150B. A combustion chamber 160 is formed between crown surface 120A of piston 120 and the underside of cylinder head 130. An ignition plug 170, which ignites a mixture of fuel and air, is attached approximately in the center of cylinder head 130, which forms combustion chamber 160.

[0012] 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.

[0013] 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, for example, 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.

[0014] The VCR mechanism 190 varies 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, thereby varying the compression ratio. An example of the VCR mechanism 190 will be described below, but other configurations may be used as long as they can perform the required functions.

[0015] Crankshaft 140 has a plurality of journal portions 140A and a plurality of crankpin portions 140B, and journal portions 140A are rotatably supported by main bearings (not shown) of cylinder block 110. Crankpin portions 140B are eccentric from journal portions 140A, and lower link 150A is rotatably connected to crankpin portions 140B. Upper link 150B has its lower end rotatably connected to one end of lower link 150A by connecting pin 152, and its upper end rotatably connected to piston 120 by piston pin 154. Control link 192 has its upper end rotatably connected to the other end of lower link 150A by connecting pin 194, and its lower end rotatably connected to the bottom of cylinder block 110 via control shaft 196. More specifically, control shaft 196 is rotatably supported by cylinder block 110 and has an eccentric cam portion 196A that is eccentric from the center of rotation, with the lower end of control link 192 rotatably fitted into this eccentric cam portion 196A. The rotational position of control shaft 196 is controlled by an actuator 198 for compression ratio control that uses an electric motor.

[0016] In VCR mechanism 190 using such a multi-link mechanism, when control shaft 196 is rotated by actuator 198, the center position of eccentric cam portion 196A, i.e., its relative position with respect to cylinder block 110, changes. As a result, when the swing support position of the lower end of control link 192 changes, the position of piston 120 at piston top dead center (TDC) rises or falls, increasing or decreasing the volume of combustion chamber 160 and changing the compression ratio of internal combustion engine 100. At this time, when operation of actuator 198 is stopped, the reciprocating motion of piston 120 rotates control link 192 relative to eccentric cam portion 196A of control shaft 196, changing the compression ratio toward a lower compression ratio.

[0017] 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 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 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 are within the normal control range RNG1, thereby restricting the displacement of the control shaft 196. Here, stopper mechanism 210 functions when control shaft 196 exceeds normal control range RNG1, so that first member 210A and second member 210B do not come into contact with each other under normal control, making it possible to suppress, for example, the generation of abnormal noise. Note that stopper mechanism 210 not only regulates the displacement of control shaft 196, but can also be used to learn the reference position of control shaft 196.

[0018] It is sufficient for stopper mechanism 210 to restrict displacement of at least one of the maximum compression ratio side and the minimum compression ratio side with respect to the rotation of control shaft 196. Furthermore, stopper mechanism 210 is not limited to substantially sector-shaped first member 210A and plate-shaped second member 210B, and may be any other shape that restricts displacement of control shaft 196 using two or more members.

[0019] 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 known networks such as FlexRay (registered trademark) can also be used.

[0020] 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 examples of operating conditions 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 suited to the rotation speed and load are set, and determines a target angle for the VTC mechanism 180 and a target compression ratio for the VCR mechanism 190, respectively, according to the rotation 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. In addition, 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.

[0021] Upon receiving the target angle, VTC controller 220 feedback-controls the drive current output to the actuator of VTC mechanism 180 so that the actual angle (actual angle) detected by a sensor (not shown) approaches the target angle. Furthermore, VCR controller 230, upon receiving the target compression ratio, feedback-controls the drive current output to actuator 198 of 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 manner, VTC mechanism 180 and VCR mechanism 190 are each controlled to a target value according to the operating state of internal combustion engine 100.

[0022] 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 that 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 rotation angle of the control shaft 196 from the output value of the first resolver 280, in other words, the compression ratio of the internal combustion engine 100. This is because the first resolver 280 has high resolution when detecting absolute angles but cannot distinguish between, for example, 0° and 360° that are in 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.

[0023] The first resolver 280 and the second resolver 290 output two correlated signals, specifically, a sine wave signal and a cosine wave signal, according 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 disposed with an angular difference of 90°. 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. The second resolver 290 has a similar configuration to the first resolver 280, and therefore a description thereof 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.

[0024] 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 obtain the sum of squares (sin 2 θ+cos 2 θ), and depending on whether this sum of squares is within a normal range, it can be determined whether a fault has occurred in first resolver 280. If VCR controller 230 determines that first resolver 280 has a fault, it electronically controls VCR mechanism 190 using the output value of second resolver 290 instead of the rotation angle determined from the output value of first resolver 280, with the output value of second resolver 290 at engine start as the base point.

[0025] 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.

[0026] The resolver excitation circuit 300 is configured with a CR filter circuit 310, a voltage follower circuit 320, an AC coupling 330, and an RL circuit 340, all connected in series. The CR filter circuit 310 generates an AC signal containing a 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 up of a capacitor with a predetermined capacitance value, and 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.

[0027] 6, the CR filter circuit 310 is an electric 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 electric resistance value and a capacitor 312C having a predetermined electric capacitance value. Similarly to the first CR filter 312, the second CR filter 314 is configured to include a resistor 314R having a predetermined electric resistance value and a capacitor 314C having a predetermined electric capacitance value.

[0028] Specifically, one terminal of the resistor 312R in the first CR filter 312 is connected to the VCR controller 230, and the other terminal of the resistor 312R in the first CR filter 312 is connected to one terminal of the resistor 314R in the second CR filter 314. The other terminal of the resistor 314R in the second CR filter 314 is connected to the voltage follower circuit 320. The electrical path between the other terminal of the resistor 312R in the first CR filter 312 and one terminal of the resistor 314R in the second CR filter 314 is connected to ground GND via the capacitor 312C in the first CR filter 312. The electrical path between the other terminal of the resistor 314R in the second CR filter 314 and the voltage follower circuit 320 is connected to ground GND via the capacitor 314C in the second CR filter 314.

[0029] 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 containing an offset voltage, which is a DC component.

[0030] The voltage follower circuit 320 is an electrical circuit configured by combining an operational amplifier OP having 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 an AC coupling 330, and is also branched off midway and connected to the inverting input terminal (-) of the operational amplifier OP via the resistor 320R. Therefore, the voltage follower circuit 320 functions as a non-inverting amplifier circuit with an amplification factor of 1, and converts the impedance of the AC signal.

[0031] The AC coupling 330 is an electric circuit formed by connecting two capacitors C1 and C2 in series, i.e., an electric circuit including two capacitors C1 and C2 connected in series. Specifically, one terminal of the capacitor C1 is connected to the output terminal of the operational amplifier OP of the voltage follower circuit 320, and the other terminal of the capacitor C1 is connected to one terminal of the capacitor C2. The other terminal of the capacitor C2 is connected to the input terminal of the RL circuit 340. Here, it is desirable that the capacitors C1 and C2 have the same capacitance (a predetermined electric capacitance value) so that even if one of them is shorted, the other capacitor can perform the required function. Note that the "same capacitance" does not necessarily mean exactly the same capacitance, but may refer to capacitances that are considered to be approximately the same, including allowable variations, for example.

[0032] 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 one terminal of the excitation coil 284A of the first resolver 280 via a connector CN. In addition, the other terminal of the excitation coil 284A of the first resolver 280 is connected (grounded) via the connector CN.

[0033] In the resolver excitation circuit 300, the electrical path located between the VCR controller 230 and the CR filter circuit 310 is connected to the ground GND via a resistor R1 having a predetermined electrical resistance value. Therefore, the resistor R1 functions as a pull-down resistor, and can ensure that the minimum voltage of the PWM signal output from the VCR controller 230 is 0 [V].

[0034] In addition, in the resolver excitation circuit 300, the electric path located between the voltage follower circuit 320 and the AC coupling 330 is connected to the ground GND via a resistor R2 having a predetermined electric resistance value. Therefore, the resistor R2 functions as a pull-down resistor, and can ensure that the minimum potential of the AC signal output from the voltage follower circuit 320 becomes 0 [V].

[0035] Furthermore, in the resolver excitation circuit 300, the electric path located 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 direction. Therefore, the Zener diodes ZD absorb the surge voltage (back electromotive force) generated in the excitation coil 284A of the first resolver 280, and can prevent excessive current from flowing in each electric element, for example.

[0036] In the resolver excitation circuit 300 of the prior art, the AC coupling 330 is composed of a single capacitor, as shown in Fig. 7. In this case, if the AC coupling 330 is shorted 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, which could result in a decrease in the angle detection accuracy of the resolver.

[0037] 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 is shorted, the DC component can be removed by the other capacitor. Therefore, even if one of the capacitors is shorted, the current output from the voltage follower circuit 320 does not increase, and it is possible to prevent the waveform of the sine wave output from the resolver excitation circuit 300 from being distorted. Note that, since it is extremely rare for both capacitors C1 and C2 to be shorted, this does not usually need to be taken into consideration.

[0038] 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 an 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.

[0039] In the CR filter circuit 310 shown in FIG. 8, if any of resistors 312R, 314R, and R3 is disconnected 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 and the excitation signal period is delayed by T1 [μs] in half cycles compared to normal operation. If any of resistors 314R and 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 any of capacitors 312C and C3 is disconnected, 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 in half cycles compared to normal operation. When the capacitor 314C is disconnected, 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 the normal state, and the period of the excitation signal becomes the same as the normal state.

[0040] 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 the resistors 312R, 314R, and R3 or the capacitors 312C, 314C, and C3 of the CR filter circuit 310. If any of the resistors 312R, 314R, and R3 is disconnected or any of the capacitors 312C, 314C, and C3 is shorted, the amplitude of the excitation signal is always 0 [V], as described above, so that 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 of the capacitors 312C and C3 is disconnected. In this case, if the resistor 312R is shorted, the amplitude of the excitation signal exceeds the predetermined threshold, so that a fault can be detected. If either of the resistors 314R and R3 is shorted, the amplitude of the excitation signal remains within the predetermined threshold, so that 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, which may make it impossible to detect the fault. On the other hand, if capacitor 314C is disconnected, the amplitude of the excitation signal will exceed the predetermined threshold, which makes it possible to detect the fault.

[0041] 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 FIG. 8. Assume that the allowable rotation angle error is within a range 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 is 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 is 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 is the same as normal operation, making the rotation angle error tolerable. If capacitor 314C is disconnected, the excitation signal period is the same as normal operation, making the rotation angle error tolerable.

[0042] If resistor 312R is shorted, it is not possible to tolerate an error in the rotation angle, but since the fault can be detected, 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 a fault, but since the error in the rotation angle can be tolerated, it has little effect on control. If either capacitor 312C or C3 is disconnected, it may not be possible to detect a fault, but since the error in the rotation angle can be tolerated, it has little effect on control. If capacitor 314C is disconnected, it is possible to detect a fault and since the error in the rotation angle can be tolerated, it has little effect on control.

[0043] Therefore, even if a failure occurs in any of the resistors 312R, 314R, R3 and 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 suppressing the impact on control.

[0044] 10, the resolver excitation circuit 300 may output an excitation signal to both the first resolver 280 and the second resolver 290, rather than to just one of them. In this case, the electric path between the resistor R2 and the AC coupling 330 is branched, and the excitation signal is output to the second resolver 290 via an AC coupling 330', an RL circuit 340', a Zener diode ZD', and a connector CN' arranged there. In short, two systems are provided in parallel with the voltage follower circuit 320: an AC coupling 330, an RL circuit 340, and a Zener diode ZD related to the first resolver 280, and an AC coupling 330', an RL circuit 340', and a Zener diode ZD' related to the second resolver 290.

[0045] 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 enables cost reduction and reduction in mounting space compared to a system equipped with two resolver excitation circuits 300. Furthermore, by providing two systems of AC couplings 330, 330', RL circuits 340, 340', and Zener diodes ZD, ZD' in parallel, 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.

[0046] It goes without saying that the electrical resistance values of the resistors, the electrical capacitance values of the capacitors, and the inductance values of the coils used in each of the embodiments described above can be appropriately selected so that they work together to perform the required functions.

[0047] Furthermore, 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 above-described embodiments, combining parts of them appropriately, or replacing parts of them with well-known technology.

[0048] For example, resolver excitation circuit 300 may be mounted on the board of VCR controller 230. Furthermore, resolver excitation circuit 300 is not limited to being provided in VCR controller 230, which electronically controls VCR mechanism 190, but may also be provided in VTC controller 220, which electronically controls VTC 180, or in another controller (not shown). [Explanation of symbols]

[0049] 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

1. 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.

2. 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 .

3. 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.

4. The pulse width modulation signal is output from a microcomputer.

4. The excitation signal generating device according to claim 1.

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