Rotary transformer signal detection circuit and detection method thereof

Abstract

The present invention provides a resolver signal detection circuit and a detection method thereof, the resolver signal detection circuit can separately detect an angle signal without affecting an original resolver signal for control, and can be used outside a resolver unit. A resolver signal detection circuit (100) is provided with: a plurality of pairs of branch lines (5c, 5d; 6c, 6d; 7c, 7d) branched from between the resolver (80) and the RDC (90); a detection circuit (10) for detecting a pair of angle signals output from the output coils (6, 7) of the resolver (80) via a plurality of pairs of branch lines (5c, 5d; 6c, 6d; 7c, 7d), at least one pair of output branch lines (6c, 6d; 7c, 7d) that are inputted as differential signals to the detection circuit (10) and that output single-ended signals; an inverting amplifier circuit (20) that amplifies or attenuates the single-ended signal from the detection circuit (10); a low-pass filter circuit (30) that removes noise of the single-ended signal amplified or attenuated by the inverting amplifier circuit (20); and a differential output circuit (40) that converts the single-ended signal from which the noise has been removed by the low-pass filter circuit (30) into a differential signal and outputs the differential signal.

Description

Technical Field

[0001] The present invention relates to a resolver signal detection circuit and a detection method thereof, which can detect rotation angle information separately from a resolver unit for measuring the rotation angle of an electric motor without affecting an existing control resolver signal. Background Art

[0002] In recent years, as environmental problems such as air pollution and global warming caused by exhaust gases from fuel vehicles have become increasingly serious, electric vehicles (EVs) have become increasingly popular. Electric vehicles drive electric motors using the power of the battery they carry, and the speed of the electric vehicle is controlled by controlling the rotation of the electric motor. In order to effectively control the rotation of the electric motor, it is necessary to accurately measure the rotation angle, and a rotary transformer is known as a rotation angle measurement device (rotation angle sensor).

[0003] Figure 8 The rotary transformer unit 200 is illustrated, which includes: a 1-phase excitation 2-phase output type rotary transformer 80, a rotary transformer digital converter (RDC) 90, and a control IC 95. The excitation coil 5 of the rotary transformer 80 includes: a primary excitation coil 5-1, which is provided on the stator, and is supplied with a differential AC signal (excitation signal) of an arbitrary frequency by the RDC 90 via signal lines 5a and 5b; a secondary excitation coil 5-2, which is provided on the rotor (rotor) coaxially connected to the motor, is magnetically connected to the primary excitation coil 5-1 and generates an AC signal. The sine wave coil 6 of the rotary transformer (resolver) 80 is provided on the stator, receives a carrier with the same frequency as the excitation signal from the secondary excitation coil 5-2, and outputs a sine wave signal (including a sine wave and a carrier) in which a sine wave is carried in the carrier to the RDC 90 via signal lines 6a and 6b, and the sine wave corresponds to the rotation angle of the rotor. The cosine wave coil 7 of the rotating transformer 80 is arranged on the stator, receives a carrier with the same frequency as the excitation signal from the secondary excitation coil 5-2, and outputs a cosine wave signal (including a cosine wave and a carrier) containing a cosine wave in the carrier to RDC90 via signal lines 7a and 7b. The cosine wave corresponds to the rotation angle of the rotor and is substantially shifted by 90° relative to the phase of the sine wave of the sine wave signal.

[0004] Figure 8The RDC 90 shown calculates the rotation angle and rotation speed of the motor based on the differential AC signal of an arbitrary frequency supplied to the exciting coil 5 of the rotary transformer 80 and the sine wave signal and cosine wave signal output from the sine wave coil 6 and the cosine wave coil 7, and outputs the calculated value as a digital signal to the control IC 95. The control IC 95 sends a control signal to an inverter (not shown) based on the digital signal of the rotation angle and speed input from the RDC 90 to control the rotation speed of the motor.

[0005] There are cases where motor developers of electric vehicles (including hybrid vehicles, plug-in hybrid vehicles, and electric two-wheeled vehicles) wish to detect and analyze resolver signals from resolvers of other companies' or their own motors for research and development and performance evaluation (for the purpose of establishing performance comparison indicators). Figure 8 As shown, the RDC 90 and the control IC 95 are usually integrated as an engine control unit (ECU) 210, so the resolver signal cannot be separated and detected from the ECU 210 without loss outside the resolver unit 200. In addition, it is unknown what kind of control processing is performed inside the black-boxed ECU 210. Specifically, it is unknown what kind of resolver signal and what kind of rotation angle the control signal waveform output from the inverter to the motor is based on.

[0006] As a prior art for separating and detecting resolver signals, the waveform measuring device of Patent Document 1 comprises: a zero-crossing detection unit for detecting the zero-crossing of an excitation signal input to the resolver; a holding unit for holding an angle detection signal, the amplitude of which changes according to the rotation angle output by the resolver after Δt after the zero-crossing is detected; and an angle calculation unit for calculating the rotation angle based on the held angle detection signal. In Patent Document 1, although a waveform measuring device is illustrated in which resolver signals (excitation signal, first detection signal, and second detection signal) are branched between the resolver and the ECU through single lines, the specific structure of the branch is not disclosed.

[0007] As shown in Patent Document 1, when the branch line is a single line, the ground line of the branch line needs to be shared with the resolver and the ECU. In this case, due to the generation of noise, the resolver signal (control resolver signal) used for motor control will be adversely affected. In addition, if the branch line is simply shunted, the current of the control resolver signal will be insufficient due to the increase in the path, so that the rotation angle cannot be accurately measured in the existing ECU. That is, the waveform measurement device of Patent Document 1 cannot separate and detect the resolver signal without adversely affecting the existing rotation angle measurement.

[0008] On the other hand, a method of using a differential probe to separate and detect the waveform of the resolver signal from a pair of signal lines 5a, 5b; 6a, 6b; 7a, 7b between the resolver 80 and the RDC 90 is also considered. The differential probe is a device that sends the differential voltage signal between two points to a waveform measuring instrument such as an oscilloscope through two probes and a transmission line connected to each probe. However, since a pair of differential inputs of the differential probe are grounded internally via a resistor, noise may enter depending on the resistance value, and the waveform of the resolver signal cannot be accurately measured due to the influence of the noise.

[0009] As described above, even if attempts are made to separate the detection angle information from the resolver, it is impossible to separate the detection resolver signal from the RDC in the integrated ECU at a realistic angle. In other words, in the existing waveform measurement device that simply shunts the signal line of the existing resolver unit, the control resolver signal is affected by the noise and impedance generated by the shunt, so that the RDC detects an error. In addition, in the detection using a differential probe, the waveform of the resolver signal cannot be accurately measured due to the influence of noise. That is, in the prior art, it is impossible to separate the detection angle signal outside the existing resolver unit while the existing resolver unit is working. Prior art literature Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2013-127409 Summary of the invention Technical problem to be solved by the invention

[0011] Therefore, an object of the present invention is to provide a resolver signal detection circuit and a detection method thereof, which can separate and detect an angle signal without affecting a control resolver signal of an existing resolver unit and can be used outside the resolver unit. Technical means of solving problems

[0012] The rotary transformer signal detection circuit of the present invention comprises: a plurality of pairs of branch lines 5c, 5d; 6c, 6d; 7c, 7d, which are branched from between the rotary transformer 80 and the RDC 90, the rotary transformer 80 comprises an excitation coil 5 and output coils 6, 7, and the RDC receives an angle signal corresponding to the rotation angle of the motor from the rotary transformer 80; the detection circuit 10, via at least one pair of output branch lines 6c, 6d; 7c, 7d among the plurality of pairs of branch lines 5c, 5d; 6c, 6d; 7c, 7d, from the output line of the rotary transformer 80 Circles 6 and 7 input a pair of angle signals as differential signals to the detection circuit 10, and the detection circuit 10 outputs a single-ended signal; the inverting amplifier circuit 20 is connected to the detection circuit 10, and amplifies or attenuates the single-ended signal from the detection circuit 10; the low-pass filter circuit 30 is connected to the inverting amplifier circuit 20, and removes the noise of the single-ended signal after being amplified or attenuated in the inverting amplifier circuit 20; the differential output circuit 40 is connected to the low-pass filter circuit 30, and converts the single-ended signal after the noise is removed in the low-pass filter circuit 30 into a differential signal and outputs it.

[0013] In the resolver signal detection circuit 100 of the present invention, the angle signal is separated and detected not by a single line based on the potential of the ground line 9 of the resolver unit 200 (resolver 80 and resolver digital converter 90), but by a pair of output branch lines 6c, 6d; 7c, 7d, as a pair of differential signals by the detection circuit 10. Therefore, in the present invention, the angle signal from the resolver 80 can be separated and detected with high precision outside the resolver unit 200 while the resolver 80 and the resolver digital converter 90 are operating normally, without causing adverse effects such as current reduction and noise on the control resolver signal in the resolver unit 200.

[0014] In an embodiment of the rotary transformer signal detection circuit 100 of the present invention, multiple pairs of branch lines 5c, 5d; 6c, 6d; 7c, 7d include a pair of excitation signal branch lines 5c, 5d, which branch the excitation signal input from the rotary transformer digital converter 90 to the excitation coil 5, and the excitation signal is input to the detection circuit 10 as a differential signal from the rotary transformer digital converter 90 via a pair of excitation signal branch lines 5c, 5d. The output coils 6 and 7 include: a sine wave coil 6 that outputs a sine wave signal as an angle signal; a cosine wave coil 7 that outputs a cosine wave signal as an angle signal, and the phase of the cosine wave signal is substantially shifted by 90° relative to the sine wave signal of the sine wave coil 6. The plurality of pairs of branch lines 5c, 5d; 6c, 6d; 7c, 7d include: a pair of excitation signal branch lines 5c, 5d that branch the excitation signal input from the rotary transformer digital converter 90 to the excitation coil 5; a pair of sine wave signal branch lines 6c; 6d that serve as a pair of output branch lines that branch the sine wave signal input from the sine wave coil 6 to the rotary transformer digital converter 90; and a pair of cosine wave signal branch lines 7c; 7d that serve as output branch lines that branch the cosine wave signal input from the cosine wave coil 7 to the rotary transformer digital converter 90. The detection circuit 10 includes: a first detection circuit 10 connected to the excitation coil 5 via a pair of excitation signal branch lines 5c, 5d; a second detection circuit 10 connected to the sine wave coil 6 via a pair of sine wave signal branch lines 6c, 6d; and a third detection circuit 10 connected to the cosine wave coil 7 via a pair of cosine wave signal branch lines 7c, 7d. A first inverting amplifier circuit 20, a first low-pass filter circuit 30, and a first differential output circuit 40 are connected in series with the first detection circuit 10 to form an excitation signal processing unit 105; a second inverting amplifier circuit 20, a second low-pass filter circuit 30, and a second differential output circuit 40 are connected in series with the second detection circuit 10 to form a sine wave signal processing unit 106; and a third inverting amplifier circuit 20, a third low-pass filter circuit 30, and a third differential output circuit 40 are connected in series with the third detection circuit 10 to form a cosine wave signal processing unit 107. The detection circuit 10 is an instrumentation amplifier 11, 10a, or a circuit 10b equivalent to the instrumentation amplifier 11 composed of detection amplifiers 12, 13, 14 and detection resistors R19-R29, and outputs a single-ended signal based on the detection circuit potential Vg inside the resolver signal detection circuit 100. The inverting amplifier circuit 20 comprises: an input resistor R1, one end of which is connected to the detection circuit 10; a gain amplifier 21, which has an inverting input terminal connected to the other end of the input resistor R1 and a non-inverting input terminal connected to the detection circuit potential Vg inside the rotary transformer signal detection circuit 100; a feedback resistor R3, one end and the other end of which are respectively connected to the inverting input terminal and the output terminal of the gain amplifier 21, and the feedback resistor R3 is a variable resistor. The low-pass filter circuit 30 is a Butterworth filter circuit composed of a filter amplifier 31 , filter resistors R5 - R9 , and capacitors C1 , C2 . The differential output circuit 40 is a circuit 40a including a fully differential amplifier 41, or a differential conversion circuit 40b composed of differential conversion amplifiers 42, 43 and differential conversion resistors R31-R45, including offset voltage input parts 45, 46, and the offset voltage input parts 45, 46 apply an offset voltage when converting a single-ended signal into a differential signal.

[0015] The rotary transformer signal detection method of the present invention comprises the following steps: a step of causing a rotary transformer 80 having an excitation coil 5 and output coils 6 and 7 to output an angle signal corresponding to the rotation angle of the motor to a rotary transformer digital converter 90; a step of inputting a pair of angle signals output from the output coils 6 and 7 of the rotary transformer 80 as differential signals to a detection circuit 10 via at least one pair of output branch lines 6c, 6d, 7c, and 7d among a plurality of pairs of branch lines 5c, 5d, 6c, 6d, 7c, and 7d branched from between the rotary transformer 80 and the rotary transformer digital converter 90, and causing the detection circuit to output a single-ended signal; a step of causing an inverting amplifier circuit 20 connected to the detection circuit 10 to amplify or attenuate the single-ended signal from the detection circuit 10; a step of causing a low-pass filter circuit 30 connected to the inverting amplifier circuit 20 to remove noise from the single-ended signal amplified or attenuated in the inverting amplifier circuit 20; and a step of causing a differential output circuit 40 connected to the low-pass filter circuit 30 to convert the single-ended signal after the noise is removed in the low-pass filter circuit 30 into a differential signal and output the differential signal. Effects of the Invention

[0016] The rotary transformer signal detection circuit of the present invention can obtain an angle signal (detect a rotary transformer signal) from the outside of the rotary transformer unit as the rotation angle information of the motor while the motor and the rotary transformer unit for the electric vehicle are working normally, so that the output performance of the motor can be accurately evaluated. In addition, in the present invention, even if the car equipped with the motor is running, the angle signal can be separated and detected without loss, and the motor rotation angle and speed can be measured together with the data of noise, vibration, road conditions, torque, etc. during driving, so as to obtain useful driving data. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a block diagram showing a resolver signal detection circuit according to the present invention. Figure 2 : is a circuit diagram showing a resolver signal detection circuit according to the present invention. Figure 3 is a circuit diagram showing an embodiment of a detection circuit. Figure 4 is a circuit diagram showing an embodiment of a differential output circuit. Figure 51 is a waveform diagram showing a resolver signal detected after being processed by the resolver signal detection circuit of the present invention. Figure 6 1 is a waveform diagram showing a resolver signal detected by a conventional detection method (common ground single-line branch detection). Figure 7 FIG. 1 is a waveform diagram showing a resolver signal detected by a conventional detection method (differential probe detection). Figure 8 1 is a schematic diagram showing a resolver unit. DETAILED DESCRIPTION

[0018] refer to Figures 1 to 8 Embodiments of the resolver signal detection circuit of the present invention will be described. The following embodiments are illustrative only and do not limit the technical scope of the present invention. Figure 1 1 is a block diagram schematically showing resolver signal detection circuit 100 of the present invention connected in shunt to resolver unit 200 . Figure 1 The rotary transformer signal detection circuit 100 shown has: a plurality of pairs of branch lines 5c, 5d; 6c, 6d; 7c, 7d, branched from the signal lines 5a.5b; 6a.6b; 7a.7b between the rotary transformer 80 and the rotary transformer digital converter (RDC) 90; a four-stage circuit, namely, a detection circuit 10, an inverting amplifier circuit 20, a low-pass filter circuit 30 and a differential output circuit 40.

[0019] For the detection circuit 10 in the first stage, a pair of angle signals output from the output coils 6 and 7 of the resolver 80 are input as differential signals via at least one pair of output branch lines 6c, 6d; 7c, 7d among the plurality of branch lines 5c, 5d; 6c, 6d; 7c, 7d between the resolver 80 and the engine control unit (ECU) 210, and a pair of excitation signals output from the RDC 90 are input as differential signals via another pair of branch lines (excitation signal branch lines) 5c, 5d, and a single-ended signal is output. According to the detection circuit 10, the detection resolver signal including the angle signal can be detected without affecting the current of the control resolver signal in the resolver unit 200. In this specification, regarding the resolver signal composed of the excitation signal, the sine wave signal (including the sine wave and the carrier) and the cosine wave signal (including the cosine wave and the carrier), the signal detected by the branch lines 5c, 5d; 6c, 6d; 7c, 7d is called the detection resolver signal, and the signal input and output to the RDC90 is called the control resolver signal. In addition, the signal (sine wave signal and cosine wave signal) containing the rotation angle information in the resolver signal is called the angle signal.

[0020] The second-stage inverting amplifier circuit 20 is connected to the detection circuit 10, and amplifies or attenuates the single-ended signal from the detection circuit 10 to an arbitrary amplitude. The third-stage low-pass filter circuit 30 is connected to the inverting amplifier circuit 20, and removes the high-frequency noise of the single-ended signal amplified or attenuated in the inverting amplifier circuit 20. The fourth-stage differential output circuit 40 is connected to the low-pass filter circuit 30, and converts the single-ended signal after the noise is removed in the low-pass filter circuit 30 into a differential signal and outputs it. As a result, the detection resolver signal including the angle signal can be used outside the resolver unit 200.

[0021] The rotary transformer 80 is a 1-phase excitation 2-phase output type rotary transformer 80 ( Figure 8 ), outputs an angle signal corresponding to the rotation angle of the motor, and comprises: an excitation coil 5, to which RDC90 supplies an excitation signal as a carrier; a sine wave coil (output coil) 6, which outputs a sine wave signal containing a sine wave in the carrier as an angle signal to RDC90, and the sine wave depends on the rotation angle; a cosine wave coil (output coil) 7, which outputs a cosine wave signal containing a cosine wave in the carrier as an angle signal to RDC90, and the phase of the cosine wave is substantially offset by 90° relative to the sine wave contained in the sine wave signal of the sine wave coil 6. The rotary transformer 80 is not limited to a 1-phase excitation 2-phase output type, and a 2-phase excitation 1-phase output type rotary transformer (not shown) may also be used.

[0022] like Figure 1As shown, multiple pairs of branch lines 5c, 5d; 6c, 6d; 7c, 7d branched out from the signal lines 5a, 5b; 6a, 6b; 7a, 7b between the rotating transformer 80 and the RDC90 include: a pair of excitation signal branch lines 5c, 5d, which branch the excitation signal input from the RDC90 to the excitation coil 5; a pair of sine wave signal branch lines 6c; 6d, which are a pair of output branch lines for branching the sine wave signal input from the sine wave coil 6 to the RDC90; a pair of cosine wave signal branch lines 7c; 7d, which are a pair of output branch lines for branching the cosine wave signal input from the cosine wave coil 7 to the RDC90. Therefore, in the present embodiment, there is no adverse effect on the control rotary transformer signal (excitation signal, sine wave signal and cosine wave signal for motor control) between the rotary transformer 80 and the RDC90, and while the rotary transformer 80 and the RDC90 are operating normally, the excitation signal, sine wave signal and cosine wave signal can be extracted with high precision outside the rotary transformer unit 200 as a detection rotary transformer signal through each pair of branch lines 5c, 5d; 6c, 6d; 7c, 7d of the excitation signal, sine wave signal and cosine wave signal. In particular, when the rotary transformer signal is detected by separating the signal lines 5a and 5b of the excitation signal through the existing technology (common ground single-line branch detection, differential probe detection), the excitation signal is affected by the current reduction and noise in the signal lines 5a and 5b, and becomes unable to excite the excitation coil 5, thereby failing to output the angle signal normally from the rotary transformer 80. In contrast, in the present embodiment, if Figure 1 As shown, since there is a pair of excitation signal branch lines 5c, 5d, and the excitation signal is input as a differential signal from the RDC90 via the excitation signal branch lines 5c, 5d to the high impedance detection circuit 10, the disadvantage of the prior art that the excitation coil 5 cannot be excited can be avoided.

[0023] exist Figure 1In the resolver signal detection circuit 100 shown, the detection circuit 10 includes: a first detection circuit 10 connected to the excitation coil 5 via a pair of excitation signal branch lines 5c, 5d; a second detection circuit 10 connected to the sine wave coil 6 via a pair of sine wave signal branch lines 6c, 6d; and a third detection circuit 10 connected to the cosine wave coil 7 via a pair of cosine wave signal branch lines 7c, 7d. In the resolver signal detection circuit 100, the first detection circuit 10 is connected in series with the first inverting amplifier circuit 20, the first low-pass filter circuit 30, and the first differential output circuit 40, and constitutes an excitation signal processing unit 105; the second detection circuit 10 is connected in series with the second inverting amplifier circuit 20, the second low-pass filter circuit 30, and the second differential output circuit 40, and constitutes a sine wave signal processing unit 106; and the third detection circuit 10 is connected in series with the third inverting amplifier circuit 20, the third low-pass filter circuit 30, and the third differential output circuit 40, and constitutes a cosine wave signal processing unit 107.

[0024] Figure 2 The specific circuit diagram of the resolver signal detection circuit 100 is illustrated. Since the internal electrical and mechanical structures of the excitation signal processing unit 105, the sine wave signal processing unit 106, and the cosine wave signal processing unit 107 are substantially the same, a simple circuit structure can be implemented, thereby reducing manufacturing costs. Figure 2 Only one internal structure of the processing units 105, 106, and 107 is illustrated, and the records of "first", "second", and "third" are omitted below, and they are simply represented as "detection circuit 10", "inverting amplifier circuit 20", "low-pass filter circuit 30", and "differential output circuit 40".

[0025] Figure 2 The detection circuits 10 and 10a shown are instrument amplifiers 11. The differential signal (detection resolver signal) from the resolver 80 is input to two input terminals of the instrument amplifier 11 through a pair of branch lines 5c, 5d; 6c, 6d; 7c, 7d, and a single-ended signal is output from an output terminal based on the detection circuit potential Vg inside the resolver signal detection circuit 100. Considering that the amplitude of the detection resolver signal is large, the instrument amplifier 11 preferably has an attenuation function. Figure 2 The instrumentation amplifier 11 shown (and equivalent to the instrumentation amplifier 11 described later) Figure 3The circuit 10b of the instrumentation amplifier 11 can suppress the current flowing from the resolver 80 to the minimum and detect the weak angle signal outside the resolver unit 200 due to its high input impedance characteristics. In addition, in the detection circuit 10, its reference potential is not shared with the ground line 9 of the resolver unit 200, but a single-ended signal is output based on the detection circuit potential Vg inside the resolver signal detection circuit 100. Therefore, in this embodiment, the current reduction of the resolver unit 200 can be avoided, the generation of noise caused by the sharing of the ground line 9 can be avoided, and the angle signal can be separated and detected while the resolver unit 200 is operating normally.

[0026] In this embodiment, the angle signal is directly input to Figure 2 Instrument amplifier 11 (or later described Figure 3 The detection amplifier 12, 13) realizes high impedance input. Regarding the input impedance, although the ideal operational amplifier is infinite, it is actually several hundred MΩ to several hundred GΩ. This value is large enough relative to the input and output impedance (several hundred Ω) of the resolver 80 and the RDC 90, and in the detection circuits 10, 10a, 10b of the present embodiment, the angle signal as a floating signal is separated and detected by a small current due to high impedance, so as not to affect the resolver signal for control in the resolver 80 and the RDC 90.

[0027] Figure 3 As another embodiment of the detection circuit 10, a circuit (three-amplifier differential amplifier circuit) 10b equivalent to the instrument amplifier 11 composed of detection amplifiers (operational amplifiers) 12-14 and detection resistors (resistors) R19-R29 is shown. Specifically, there are two operational amplifiers 12 and 13, and the differential signal (detection of the rotary transformer signal) is input from a pair of branch lines 5c, 5d; 6c, 6d; 7c, 7d to each non-inverting input terminal of the two operational amplifiers 12 and 13, and each output terminal of the operational amplifiers 12 and 13 is respectively connected to the inverting input terminal via resistors R19 and R25, and is respectively connected to a pair of input terminals of the operational amplifier 14 via resistors R21 and R27. The output terminal of the operational amplifier 14 is connected to the inverting input terminal via resistor R23, and the non-inverting input terminal of the operational amplifier 14 is connected to the detection circuit potential Vg via resistor R29. Although in Figure 3 Although a circuit 10b including three operational amplifiers 12-14 is shown, a circuit equivalent to the instrumentation amplifier 11 (dual amplifier type differential amplifier circuit) can also be formed by two operational amplifiers (not shown), so that the number of operational amplifiers is reduced and the cost is lower.

[0028] Figure 2The inverting amplifier circuit 20 shown has: an input resistor R1, one end of which is connected to the detection circuit 10; an amplifier (operational amplifier) ​​21, having an inverting input terminal connected to the other end of the input resistor R1 and a non-inverting input terminal connected to the detection circuit potential Vg inside the resolver signal detection circuit 100; a feedback resistor R3, both ends of which are connected to the inverting input terminal and output terminal of the gain amplifier (operational amplifier) ​​21, and the feedback resistor R3 is a variable resistor. The inverting amplifier circuit 20 amplifies or attenuates the amplitude of the single-ended signal from the detection circuit 10 using the value (-R1 / R3) obtained by dividing the input resistor R1 by the feedback resistor R3 and negatively inverting it as the amplification factor. The resistance value of the feedback resistor R3 can be adjusted to change the amplification factor to an arbitrary value, so that the amplitude of the signal output from the inverting amplifier circuit 20 can be controlled. The single-ended signal output from detection circuit 10 and input to differential output circuit 40 is amplified by inverting amplifier circuit 20 with reference to reference potential Vg in resolver signal detection circuit 100 , and determines the amplitude of the signal output from differential output circuit 40 .

[0029] Figure 2 The low-pass filter circuit 30 shown is a noise removal circuit, which is a multi-stage feedback low-pass filter circuit composed of a filter amplifier (operational amplifier) ​​31, filter resistors (resistors) R5-R9 and capacitors C1 and C2, and is a second-order Butterworth filter circuit. Specifically, Figure 2 As shown, the low-pass filter circuit 30 includes: a resistor R5, one end of which is connected to the inverting amplifier circuit 20; resistors R7, R9 and a capacitor C1, one end of which is connected to the other end of the resistor R5; a capacitor C2, one end of which is connected to the other end of the resistor R9; and an operational amplifier 31, an inverting input terminal of which is connected to the resistor R7 and the other end of the capacitor C2. The output terminal of the operational amplifier 31 is feedback-connected to its inverting input terminal via the resistors R9, R7 and the capacitor C2. The non-inverting input terminal of the operational amplifier 31 and the other end of the capacitor C1 are respectively connected to a reference potential Vg. In the present invention, the number of low-pass filter circuits determined by the number of integrating circuit stages of resistors and capacitors is not limited to Figure 2 The two-stage circuit shown may be one or more than one-stage circuit. In addition, the low-pass filter circuit 30 is not limited to an active filter formed by an operational amplifier 31, but may also be a passive filter formed by a resistor, a capacitor, and a coil.

[0030] Figure 2The differential output circuit 40 shown is a circuit 40a including a fully differential amplifier 41, specifically, it comprises: a resistor R11, one end of which is connected to the low-pass filter circuit 30; a resistor R13, one end of which is connected to the detection circuit potential Vg; and a fully differential amplifier 41, whose inverting input terminal and non-inverting input terminal are respectively connected to the other ends of the resistors R11 and R13. The two output terminals of the fully differential amplifier 41 are respectively feedback-connected to its inverting and non-inverting input terminals via resistors R15 and R17. Thus, the circuit 40a including the fully differential amplifier 41 (and the circuit described later) Figure 4 The differential output circuit 40b) can restore the same differential signal as the resolver unit 200 outside the resolver unit 200 as a detection resolver signal. In addition, offset voltage input units 45 and 46 are included, which apply an offset voltage (adjustment voltage) Vos to the full differential amplifier 41 (and differential conversion amplifiers 42 and 43) when converting the single-ended signal from the low-pass filter circuit 30 into a differential signal. By applying the offset voltage Vos by the offset voltage input units 45 and 46, the differential signal can be directly input to the single-power drive resolver digital converter (RDC) (not shown) connected to the subsequent stage of the differential output circuit 40, and the rotation angle can be accurately measured.

[0031] Figure 4 A differential conversion circuit 40b as another embodiment of the differential output circuit 40 is shown, which is composed of differential conversion amplifiers 42, 43 and differential conversion resistors R31-R45. Specifically, the circuit includes: resistors R33, R41, one end of which is connected to the low-pass filter circuit 30; resistors R31, R39, one end of which is connected to the detection circuit potential Vg; an operational amplifier 42, whose inverting input terminal and non-inverting input terminal are respectively connected to the other end of the resistors R31, R33; an operational amplifier 43, whose inverting input terminal and non-inverting input terminal are respectively connected to the other end of the resistors R39, R41. The output terminal of the operational amplifier 42 is feedback-connected to its inverting input terminal via the resistor R35, and the output terminal of the operational amplifier 43 is feedback-connected to its non-inverting input terminal via the resistor R43. The differential conversion circuit 40b also has an offset voltage input unit 46, and the non-inverting and inverting input terminals of the operational amplifiers 42, 43 are respectively connected to the offset power supply via the resistors R37, R45.

[0032] The gain of the circuit 40a including the fully differential amplifier 41 is set by the values ​​of the resistors R11-R17, and the gain of the differential conversion circuit 40b is set by the values ​​of the resistors R31, R35, R41, and R43. Since high-precision impedance matching is required between the differential output circuit 40 and its output target, it is preferable to use a fixed-gain differential output circuit 40 in which the resistors are packaged. Figure 1 and Figure 2Although the subsequent stage of resolver signal detection circuit 100 is not shown, differential output circuit 40 is connected to an RDC (not shown) to calculate the numerical values ​​of the rotation angle and the rotation speed of the target motor.

[0033] exist Figure 4 In the differential output circuit 40b, although the two operational amplifiers 42 and 43 are connected in parallel, as another embodiment, a differential output can also be obtained by connecting two first and second operational amplifiers in series (not shown). Specifically, the output of the first operational amplifier is used as a differential output and as an input of the second operational amplifier; the output of the second operational amplifier is used as another differential output. Figure 2 as well as Figure 4 Although the offset voltage input parts 45 and 46 are shown in the differential output circuits 40, 40a and 40b, for example, when the angle calculation is performed using a data latch or a calculation function of a high-performance oscilloscope, or when the angle signal data is obtained through a personal computer (PC) and then calculated, it is not necessary to apply the offset voltage Vos to the differential output circuits 40, 40a and 40b.

[0034] Hereinafter, an embodiment of the resolver signal detection method of the present invention will be described. In the resolver signal detection method, as a normal operation of the resolver unit 200 to measure the rotation angle, the resolver digital converter (RDC) 90 supplies an excitation signal to the excitation coil 5 of the resolver 80, and the resolver 80 outputs an angle signal corresponding to the rotation angle of the motor from the output coils 6 and 7 to the RDC 90. Specifically, a sine wave signal including a carrier wave and a sine wave is output from the sine wave coil 6 of the output coil, the carrier wave has the same frequency as the excitation signal, and the sine wave depends on the rotation angle of the resolver 80, and a cosine wave signal including a carrier wave and a cosine wave is output from the cosine wave coil 7 of the output coil, the carrier wave has the same frequency as the excitation signal, and the phase of the cosine wave is substantially shifted by 90° relative to the sine wave of the sine wave signal.

[0035] exist Figure 2 In the first stage detection circuit 10 shown in the figure, the signal lines 5a, 5b; 6a, 6b; 7a, 7b branched from the rotary transformer 80 and the RDC 90 are Figure 15c, 5d; 6c, 6d; 7c, 7d shown, separate and detect the detection rotary transformer signal containing a pair of angle signals as differential signals. Specifically, the excitation signal input from RDC90 to the excitation coil 5 is separated and detected via a pair of excitation signal branch lines 5c, 5d, the sine wave signal input from the sine wave coil 6 to RDC90 is separated and detected via a pair of sine wave signal branch lines 6c; 6d, and the cosine wave signal input from the cosine wave coil 7 to RDC90 is separated and detected via a pair of cosine wave signal branch lines 7c; 7d. In the detection circuit 10, a single-ended signal with a gain set to 1 is output, for example, through the instrument amplifier 11, 10a or the circuit 10b composed of the detection amplifier 12-14 and the detection resistor R19-R29.

[0036] Figure 2 The second-stage inverting amplifier circuit 20 shown is input with a single-ended signal from the detection circuit 10 of the previous stage, and the single-ended signal is input to the inverting input terminal of the gain amplifier (operational amplifier) ​​21 via the input resistor R1. The output signal of the operational amplifier 21 is negatively fed back via the variable resistor R3, and the inverting amplifier circuit 20 outputs a single-ended signal amplified or attenuated to the required amplification factor (-R1 / R3).

[0037] exist Figure 2 In the third-stage low-pass filter circuit (Butterworth circuit) 30 shown, the amplified or attenuated single-ended signal is input by the inverting amplifier circuit 20 connected to the previous stage, and the high-frequency noise is removed. The low-pass filter circuit 30 is constructed as an inverting circuit in the same manner as the inverting amplifier circuit 20 of the previous stage, so that the single-ended signal output from the low-pass filter circuit 30 is restored to a non-inverting signal. In the low-pass filter circuit 30, the cut-off characteristics (cut-off frequency) and the phase characteristics (phase change) can be set by the filter resistors R5, R7, R9 and the capacitors C1 and C2. The cut-off frequency refers to the frequency at which the gain of the signal is reduced by 3dB from the passband, and the phase change refers to the phase difference between the input and output signals. In this embodiment, for example, the resistance values ​​of R5, R7 and R9 are 5.6kΩ, 12kΩ and 5.6kΩ respectively, the electrostatic capacitances C1 and C2 of the capacitors are 680pF and 220pF respectively, and the cut-off frequency (=1 / (2π(C1·C2·R7·R9)) 0.5 )) is set to 50kHz, and the phase change (delay phase) at the cutoff frequency of 50kHz is set to -90°. In addition, based on the rotation speed of the resolver 80 of 20000rpm (the frequency of the electrical angle is 330Hz), it is designed to suppress the phase change relative to the signal with a frequency of 400Hz to less than 0.1°. Furthermore, in order to ensure the conversion accuracy of the RDC connected to the resolver signal detection circuit 100, it is designed to suppress the phase change at a typical excitation signal frequency of 10kHz to less than 40°.

[0038] exist Figure 2 In the fourth-stage differential output circuit 40 shown, the single-ended signal from which the noise is removed in the low-pass filter circuit 30 connected to the previous stage is input to the inverting input terminal of the full differential amplifier (operational amplifier) ​​41 through the resistor R11 and converted into a differential signal, and then the differential signal corresponding to the differential signal of the resolver unit 200 is output from the output terminal of the operational amplifier 41 to the RDC (not shown). In the RDC, although the actual values ​​of the rotation angle and the rotation speed can be calculated based on the output differential signal, when the differential signal is centered at 0V, the rotation angle and the like cannot be accurately calculated, so it is necessary to apply an offset voltage Vos (for example, 2.5V) to the differential output circuit 40. The numerical values ​​of the rotation angle and the like calculated in the RDC can be sent to the control IC, the measurement IC, etc. (not shown) as digital signals (serial signals, parallel signals, etc.) and speed pulses (ABZ phase signals for encoders, etc.), and used to evaluate the motor control.

[0039] Although the differential output circuits 40, 40a, 40b are shown in the above embodiment, a single-ended signal may be directly output from the low-pass filter circuit 30, and the value of the rotation angle may be calculated by an oscilloscope, a PC, or the like.

[0040] Hereinafter, the voltage waveform of the angle signal (cosine signal) output from the rotary transformer 80 and the error report of the RDC 90 will be described by comparing the embodiment according to the present invention and the comparative example according to the prior art. In the embodiment and the comparative example, the cosine wave signal is evaluated, but since each of the three pairs of signal lines 5a, 5b; 6a, 6b; 7a, 7b is identical to each other, each of the three pairs of branch lines 5c, 5d; 6c, 6d; 7c, 7d is also identical to each other, and the circuit structures of the processing units 105, 106, 107 of the excitation signal, the sine wave signal, and the cosine wave signal are also identical to each other, it can be considered that the excitation signal and the sine wave signal can also obtain the same evaluation results as the cosine wave signal.

[0041] [Evaluation system] The evaluation system of the embodiment is configured as follows: a resolver signal detection circuit 100 ( Figure 1 and Figure 2 ) is connected to an RDC (U6805, manufactured by Tamagawa Seiki Co., Ltd.) not shown in the figure. On the other hand, the comparative example evaluation system is: Figure 8The resolver unit 200 is not provided with the resolver signal detection circuit 100. The resolver unit 200 of the embodiment evaluation system and the comparative example evaluation system includes a resolver (manufactured by Tamagawa Seiki Co., Ltd.) 80 and an RDC (RDC-100, manufactured by Atsense Co., Ltd.) 90. The RDC 90 has a function of converting the resolver signal into a digital signal, and also has functions such as outputting the rotation angle, outputting the rotation speed, and reporting errors (signal degradation and signal loss).

[0042] [Example 1] In the embodiment evaluation system ( Figure 1 ), the voltage waveform (angle signal) between the measuring points A2-B2 processed by the resolver signal detection circuit 100 of the present invention is measured by an oscilloscope (Example 1). Specifically, without using a probe, the differential signal between the measuring points A2-B2 processed by the cosine wave signal processing unit 107 is used as a single-ended signal by a differential input amplifier, and is insulated by an insulating amplifier, and is measured by an oscilloscope through a BNC terminal. In order to input the RDC to the rear stage of the resolver signal detection circuit 100, the variable resistor R3 of the inverting amplifier circuit 20 is adjusted so that the maximum output value of the resolver signal detection circuit 100 is 3.2V. p-p about.

[0043] [Comparative Example 1] In the comparative example evaluation system ( Figure 8 ), a passive probe is used to measure the voltage waveform (angle signal) between the measurement point A1 of the signal line 7a and the measurement point G of the ground line 9 of the RDC90 through an oscilloscope (Comparative Example 1). The voltage waveform of Comparative Example 1 is equivalent to the voltage waveform in the existing detection method shown in the above-mentioned patent document 1, that is, the single-line branch detection method with a common ground with the ECU.

[0044] [Comparative Example 2] In the comparative example evaluation system ( Figure 8 ) in which a voltage waveform (angle signal) between measurement points A1-B1 of a pair of signal lines 7a and 7b is measured by an oscilloscope using a differential probe (Comparative Example 2).

[0045] The measurement between A2-B2 in Example 1 is equivalent to the measurement between A1-B1 via the rotary transformer signal detection circuit 100; Comparative Example 1 connects one end to the measurement point G (ground wire 9) and measures A1; Comparative Example 2 measures between A1-B1; these three can be said to be measurements performed at the same location in essence. In addition, the voltage waveform between A1-B1 on a pair of signal lines 7a, 7b is equivalent to the voltage waveform of the control rotary transformer signal. Therefore, by measuring the voltage waveforms (detection rotary transformer signal including the angle signal) of Example 1 (the present invention), Comparative Example 1 (single-line branch detection with common ground) and Comparative Example 2 (differential probe detection), it can be confirmed whether there is an influence on the control rotary transformer signal under various conditions.

[0046] [Evaluation results: Example 1] The voltage waveform of Example 1 (between measuring points A2-B2) is as follows: Figure 5 (a) and 5(b). The horizontal axis is time and the vertical axis is voltage value ( Figure 6 , Figure 7 The same applies). Figure 5 (a) (horizontal axis: -25ms~25ms) It can be seen that a clear cosine wave is measured. Figure 5 (a) After Figure 5 (b) (horizontal axis: -100 μs to 100 μs) It can be seen that a carrier with almost no noise is measured. In Example 1, no false report of signal degradation or signal loss is notified from the RDC 90.

[0047] [Evaluation results: Comparative example 1] The voltage waveform of Comparative Example 1 (between measurement points A1-G) is as follows: Figure 6 (a) and 6(b). Figure 6 (a) (horizontal axis: -20ms~20ms) and Figure 6 (a) (horizontal axis: -200 μs to 200 μs) It can be seen that a large amount of noise is measured. In Comparative Example 1, the frequency of false reports of signal degradation due to noise from the RDC 90 is high.

[0048] [Evaluation results: Comparative Example 2] The voltage waveform of Comparative Example 2 (between measuring points A1 and B1) is as follows: Figure 7 (a) and 7(b). Figure 7 (a) (horizontal axis: -50ms~50ms) It can be seen that a relatively clear cosine wave is measured. Figure 7 (a) After Figure 7(b) (horizontal axis: -200μs to 200μs) It can be seen that noise appears at the peak of the carrier reflected inside the measured cosine wave. In Comparative Example 2, as in Comparative Example 1, the frequency of false reports of signal degradation caused by noise from RDC90 is high.

[0049] [Research] It is considered that the voltage waveform of Comparative Example 1 (single-line branch detection with common ground) appears as follows Figure 6 The cause of the noise shown is the inflow of noise from the ground line 9 shared with the ECU 210. It is considered that the voltage waveform of the comparative example 2 (differential probe detection) appears as follows Figure 7 The cause of the noise shown is the inflow of noise from the differential probe. It is considered that the signal is degraded due to the inflow of noise, and in Comparative Examples 1 and 2, an erroneous report of signal degradation is issued from the RDC90.

[0050] [in conclusion] In Example 1, since a clear voltage waveform ( Figure 5 ), and there is no error report from RDC90, so it can be confirmed that in the resolver signal detection circuit 100 of the present invention, a clear angle signal with noise removed can be separated and detected without adversely affecting the control resolver signal input and output to RDC90. In Comparative Example 1, a large amount of noise was measured ( Figure 6 ), the noise was measured in Comparative Example 2 ( Figure 7 ), and error reports from RDC90 appear frequently. Therefore, it can be confirmed that the single-line detection (Comparative Example 1) that shares the same ground with ECU210 as the prior art and the detection using a differential probe (Comparative Example 2) cannot separate and detect clear angle signals, and will have an adverse effect on the control resolver signal. Industrial Applicability

[0051] The resolver signal detection circuit according to the present invention uses the angle signal of the motor as a differential signal input without affecting the resolver signal for controlling the resolver unit. Therefore, it can be used for signal detection other than resolvers, such as magnetic encoders, differential signal communications, and Wheatstone bridges. Description of Reference Numerals

[0052] 5: Excitation coil; 6: Output coil (sine wave coil); 7: Output coil (cosine wave coil); 5c, 5d: Branch line (excitation signal branch line); 6c, 6d: Branch line (output branch line, sine wave signal branch line); 7c, 7d: Branch line (output branch line, cosine wave signal branch line); 10: Detection circuit (first detection circuit 10, second detection circuit 10, third detection circuit 10); 10a, 11: Instrumentation amplifier; 10b: Circuit equivalent to instrumentation amplifier; 12, 13, 14: Detection amplifier (operational amplifier); 20: Inverting amplifier circuit; 21: Gain amplifier (operational amplifier); 30: Low-pass Filter circuit; 31: filter amplifier (operational amplifier); 40: differential output circuit; 40a: circuit including a fully differential amplifier; 41: fully differential amplifier; 45, 46: offset voltage input unit; 80: rotary transformer; 90: rotary transformer digital converter (RDC); 100: rotary transformer signal detection circuit; 105: excitation signal processing unit; 106: sine wave signal processing unit; 107: cosine wave signal processing unit; 200: rotary transformer unit; C1, C2: capacitors; R1: input resistor; R3: feedback resistor; R5-R9: filter resistor; R19-R29: detection resistor; Vg: detection circuit potential.

Claims

1. A rotary transformer signal detection circuit, characterized in that: have: A plurality of pairs of branch lines are branched from between a rotary transformer and a rotary transformer digital converter, the rotary transformer having an excitation coil and an output coil, and the rotary transformer digital converter receives an angle signal corresponding to a rotation angle of the motor from the rotary transformer; A detection circuit, wherein a pair of angle signals are input as differential signals from the output coil of the rotary transformer via at least one pair of output branch lines among the plurality of pairs of branch lines, and the detection circuit outputs a single-ended signal; An inverting amplifier circuit is connected to the detection circuit to amplify or attenuate the single-ended signal from the detection circuit; A low-pass filter circuit is connected to the inverting amplifier circuit to remove noise from the single-ended signal after being amplified or attenuated by the inverting amplifier circuit; as well as The differential output circuit is connected to the low-pass filter circuit, converts the single-ended signal after noise is removed in the low-pass filter circuit into a differential signal and outputs the differential signal.

2. The rotary transformer signal detection circuit according to claim 1, characterized in that: The plurality of pairs of branch lines include a pair of excitation signal branch lines, and the pair of excitation signal branch lines branches the excitation signal input from the rotary transformer digital converter to the excitation coil; The excitation signal is input as a differential signal from the resolver digital converter to the detection circuit via a pair of excitation signal branch lines.

3. The rotary transformer signal detection circuit according to claim 1, characterized in that: The output coil has: a sine wave coil, outputting a sine wave signal as an angle signal; and A cosine wave coil outputs a cosine wave signal as an angle signal, wherein the phase of the cosine wave signal is substantially offset by 90° relative to the sine wave signal of the sine wave coil; Multiple pairs of branch lines have: A pair of excitation signal branch lines for branching the excitation signal input from the rotary transformer digital converter to the excitation coil; a pair of sinusoidal wave signal branch lines, serving as a pair of output branch lines for branching the sinusoidal wave signal input from the sinusoidal wave coil to the resolver digital converter; and The pair of cosine wave signal branch lines serve as a pair of output branch lines for branching the cosine wave signal input from the cosine wave coil to the resolver digital converter.

4. The rotary transformer signal detection circuit according to claim 3, characterized in that: The detection circuit has: A first detection circuit is connected to the excitation coil via a pair of excitation signal branch lines; The second detection circuit is connected to the sine wave coil via a pair of sine wave signal branch lines; A third detection circuit is connected to the cosine wave coil via a pair of cosine wave signal branch lines; The first inverting amplifier circuit, the first low-pass filter circuit, and the first differential output circuit are connected in series to the first detection circuit to form an excitation signal processing unit. The second inverting amplifier circuit, the second low-pass filter circuit, and the second differential output circuit are connected in series to the second detection circuit to form a sine wave signal processing unit. The third inverting amplifier circuit, the third low-pass filter circuit, and the third differential output circuit are connected in series to the third detection circuit to form a cosine wave signal processing unit.

5. The resolver signal detection circuit according to claim 1, characterized in that: The detection circuit is an instrumentation amplifier or a circuit equivalent to an instrumentation amplifier composed of a detection amplifier and a detection resistor, and outputs a single-ended signal with the detection circuit potential inside the resolver signal detection circuit as a reference.

6. The resolver signal detection circuit according to claim 1, characterized in that: The inverting amplifier circuit has: An input resistor, one end of which is connected to a detection circuit; a gain amplifier having an inverting input terminal connected to the other end of the input resistor and having a non-inverting input terminal connected to a detection circuit potential inside the resolver signal detection circuit; as well as A feedback resistor, one end and the other end of the feedback resistor are respectively connected to the inverting input terminal and the output terminal of the gain amplifier; The feedback resistor is a variable resistor.

7. The resolver signal detection circuit according to claim 1, characterized in that: The low-pass filter circuit is a Butterworth filter circuit composed of a filter amplifier, a filter resistor and a capacitor.

8. The resolver signal detection circuit according to claim 1, characterized in that: The differential output circuit is a circuit including a fully differential amplifier, or a differential conversion circuit composed of a differential conversion amplifier and a differential conversion resistor, and includes an offset voltage input section that applies an offset voltage when converting a single-ended signal into a differential signal.

9. A rotary transformer signal detection method, characterized in that: The following steps are involved: A step of causing a resolver including an excitation coil and an output coil to output an angle signal corresponding to a rotation angle of the motor to a resolver digital converter; A step of inputting a pair of angle signals output from an output coil of the resolver as differential signals to a detection circuit via at least one pair of output branch lines among a plurality of pairs of branch lines branched from between the resolver and the resolver digital converter, and the detection circuit outputting a single-ended signal; The step of amplifying or attenuating a single-ended signal from the detection circuit by an inverting amplifier circuit connected to the detection circuit; A step of removing noise from the single-ended signal after being amplified or attenuated by the inverting amplifier circuit by a low-pass filter circuit connected to the inverting amplifier circuit; The differential output circuit connected to the low-pass filter circuit converts the single-ended signal after noise is removed in the low-pass filter circuit into a differential signal and outputs the differential signal.

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