Rotary transformer signal detection circuit and detection method thereof

Abstract

The present invention provides a rotary transformer signal detection circuit and a detection method thereof. The rotary transformer signal detection circuit can separate and detect an angle signal without affecting an original control rotary transformer signal and can be used outside a rotary transformer unit. The rotary transformer signal detection circuit (100) comprises: a plurality of pairs of branch lines (5c, 5d; 6c, 6d; 7c, 7d) branched from between the rotary transformer (80) and the RDC (90); a detection circuit (10) that inputs a pair of angle signals output from the output coils (6, 7) of the rotary transformer (80) into the detection circuit (10) as differential signals 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), and outputs a single-ended signal; 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 from 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 separate and detect rotation angle information 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, with the increasing severity of environmental issues such as air pollution and global warming caused by emissions from fuel-powered vehicles, electric vehicles (EVs) have rapidly gained popularity. EVs use electricity from their batteries to drive electric motors, controlling the rotation of the motors to control the vehicle's speed. To effectively control the rotation of electric motors, accurate measurement of the rotation angle is necessary. Resolvers are a well-known rotation angle measurement device (rotation angle sensor).

[0003] Figure 8 A resolver unit 200 is shown as an example. It includes a single-phase excitation, two-phase output resolver 80, a resolver-to-digital converter (RDC) 90, and a control IC 95. The excitation coil 5 of the resolver 80 includes a primary excitation coil 5-1, located on the stator. A differential AC signal (excitation signal) of an arbitrary frequency is supplied by the RDC 90 via signal lines 5a and 5b. A secondary excitation coil 5-2, located on the rotor coaxially connected to the motor, is magnetically coupled to the primary excitation coil 5-1 and generates an AC signal. The sinusoidal coil 6 of the resolver 80 is located on the stator. It receives a carrier wave with the same frequency as the excitation signal from the secondary excitation coil 5-2 and outputs a sinusoidal signal (comprising a sine wave and a carrier wave) to the RDC 90 via signal lines 6a and 6b. This sinusoidal wave corresponds to the rotor's rotational angle. 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 the RDC90 via signal lines 7a and 7b. The cosine wave corresponds to the rotation angle of the rotor, and the phase of the sine wave relative to the sine wave signal is substantially shifted by 90°.

[0004] Figure 8The illustrated RDC 90 calculates the motor's rotation angle and rotation speed based on a differential AC signal of an arbitrary frequency supplied to the excitation coil 5 of the resolver 80 and the sine wave and cosine wave signals output from the sine wave coil 6 and cosine wave coil 7, and outputs these digital signals to the control IC 95. Based on the digital rotation angle and speed signals input from the RDC 90, the control IC 95 sends a control signal to an inverter (not shown) to control the motor's rotation speed.

[0005] There are cases where motor developers for 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 purposes and performance evaluation (for the purpose of establishing performance comparison indices). Figure 8 As shown, RDC 90 and control IC 95 are typically integrated into engine control unit (ECU) 210. Therefore, it is impossible to detect the resolver signal from ECU 210 without loss of integrity outside resolver unit 200. Furthermore, it is unknown what control processing is performed within the black-boxed ECU 210. Specifically, it is unknown what resolver signal waveform is output from the inverter to the motor and at what rotation angle.

[0006] As a prior art for separately detecting resolver signals, Patent Document 1 discloses a waveform measurement device comprising: a zero-crossing detector that detects the zero crossing of the excitation signal input to the resolver; a holding unit that holds an angle detection signal, the amplitude of which changes based on the rotation angle output by the resolver after a period Δt following the zero-crossing detection; and an angle calculation unit that calculates the rotation angle based on the held angle detection signal. While Patent Document 1 illustrates a waveform measurement device that branches the resolver signals (excitation signal, first detection signal, and second detection signal) between the resolver and the ECU via separate single lines, the specific structure of the branching is not disclosed.

[0007] As shown in Patent Document 1, when a single branch line is used, the branch line's ground wire must be shared with the resolver and the ECU. This generates noise, adversely affecting the resolver signal used for motor control (control resolver signal). Furthermore, simply branching the line increases the number of paths, resulting in insufficient current for the control resolver signal, making it impossible to accurately measure the rotation angle in existing ECUs. In other words, the waveform measurement device of Patent Document 1 cannot detect the resolver signal separately without adversely affecting existing rotation angle measurement.

[0008] Another possible approach is to use a differential probe to separately detect the resolver signal waveform from a pair of signal lines 5a, 5b; 6a, 6b; and 7a, 7b between resolver 80 and RDC 90. A differential probe uses two probes and a transmission line connected to each probe to transmit the differential voltage signal between two points to a waveform measurement instrument such as an oscilloscope. However, because the differential probe's pair of differential inputs are internally grounded via resistors, noise can enter depending on the resistor value, affecting the resolver signal waveform and preventing accurate measurement.

[0009] As mentioned above, even when attempts have been made to separate and detect angle information from the resolver, it has been practically impossible to separate and detect resolver signals from the RDC within the integrated ECU. In other words, in existing waveform measurement devices that simply branch the signal lines of existing resolver units, the control resolver signals are affected by the noise and impedance generated by the branch, leading to erroneous RDC detection. Furthermore, when using differential probes for detection, the waveform of the resolver signal cannot be accurately measured due to the influence of noise. In other words, with existing technology, it is impossible to separate and detect angle signals externally while the existing resolver unit is operating.

[0010] Prior art literature

[0011] Patent Literature

[0012] Patent Document 1: Japanese Patent Application Laid-Open No. 2013-127409 Summary of the Invention

[0013] Technical problem to be solved by the invention

[0014] 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.

[0015] Technical means to solve the problem

[0016] 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 having an excitation coil 5 and output coils 6, 7, and the RDC receiving an angle signal corresponding to the rotation angle of the motor from the rotary transformer 80; a detection circuit 10, which outputs the angle signal from the output line of the rotary transformer 80 via at least one pair of the output branch lines 6c, 6d; 7c, 7d among the plurality of pairs of branch lines 5c, 5d; 6c, 6d; 7c, 7d. 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.

[0017] In resolver signal detection circuit 100 of the present invention, angle signal separation and detection are not based on a single line referenced by ground line 9 of resolver unit 200 (resolver 80 and resolver-digital converter 90). Instead, detection circuit 10 separates and detects the angle signal as a pair of differential signals via a pair of output branch lines 6c, 6d; and 7c, 7d. Consequently, the present invention allows for high-precision separation and detection of the angle signal from resolver 80 outside resolver unit 200 while ensuring normal operation of resolver 80 and resolver-digital converter 90, without adversely affecting the control resolver signal within resolver unit 200 due to current loss or noise.

[0018] In an embodiment of the resolver signal detection circuit 100 of the present invention, the 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 resolver digital converter 90 to the excitation coil 5. The excitation signal is input as a differential signal from the resolver digital converter 90 to the detection circuit 10 via the pair of excitation signal branch lines 5c, 5d.

[0019] Output coils 6 and 7 include a sine wave coil 6 that outputs a sine wave signal as an angle signal, and a cosine wave coil 7 that outputs a cosine wave signal as an angle signal, with the phase of the cosine wave signal being substantially offset by 90° relative to the sine wave signal from sine wave coil 6. Multiple pairs of branch lines 5c, 5d, 6c, 6d, and 7c, 7d include a pair of excitation signal branch lines 5c, 5d that branch the excitation signal input from resolver-digital converter 90 to excitation coil 5; a pair of sine wave signal branch lines 6c and 6d that serve as a pair of output branch lines that branch the sine wave signal input from sine wave coil 6 to resolver-digital converter 90; and a pair of cosine wave signal branch lines 7c and 7d that serve as output branch lines that branch the cosine wave signal input from cosine wave coil 7 to resolver-digital converter 90.

[0020] 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 and 5d; a second detection circuit 10 connected to the sine wave coil 6 via a pair of sine wave signal branch lines 6c and 6d; and a third detection circuit 10 connected to the cosine wave coil 7 via a pair of cosine wave signal branch lines 7c and 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. 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.

[0021] Detection circuit 10 is an instrumentation amplifier 11 or 10a, or a circuit 10b equivalent to instrumentation amplifier 11, which is composed of detection amplifiers 12, 13, and 14 and detection resistors R19-R29. It outputs a single-ended signal based on the detection circuit potential Vg within resolver signal detection circuit 100.

[0022] Inverting amplifier circuit 20 includes: an input resistor R1, one end of which is connected to detection circuit 10; a gain amplifier 21 having an inverting input terminal connected to the other end of input resistor R1 and a non-inverting input terminal connected to the detection circuit potential Vg within resolver signal detection circuit 100; and a feedback resistor R3, one end of which is connected to the inverting input terminal and the other end of which is connected to the output terminal of gain amplifier 21, respectively. Feedback resistor R3 is a variable resistor.

[0023] The low-pass filter circuit 30 is a Butterworth filter circuit composed of a filter amplifier 31 , filter resistors R5 - R9 , and capacitors C1 and C2 .

[0024] 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, which apply offset voltage when converting single-ended signals into differential signals.

[0025] The resolver signal detection method of the present invention includes the following steps: a resolver 80 including an excitation coil 5 and output coils 6 and 7 outputs an angle signal corresponding to the rotation angle of the motor to a resolver digital converter 90; a step of inputting a pair of angle signals output from the output coils 6 and 7 of the resolver 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, and 7c branching between the resolver 80 and the resolver digital converter 90, and causing the detection circuit to output a single-ended signal; a step of amplifying or attenuating the single-ended signal from the detection circuit 10 by an inverting amplifier circuit 20 connected to the detection circuit 10; a step of removing noise from the single-ended signal amplified or attenuated by the inverting amplifier circuit 20 by a low-pass filter circuit 30; and a step of converting the single-ended signal, after noise has been removed by the low-pass filter circuit 30, into a differential signal by a differential output circuit 40 connected to the low-pass filter circuit 30 and outputting the differential signal.

[0026] Effects of the Invention

[0027] The resolver signal detection circuit of the present invention allows the motor and resolver unit of an electric vehicle to operate normally while simultaneously acquiring an angle signal (detecting the resolver signal) from outside the resolver unit as motor rotation angle information, thereby accurately evaluating the motor's output performance. Furthermore, the present invention enables non-destructive separation and detection of the angle signal even while the vehicle equipped with the motor is in motion. This allows the motor's rotation angle and speed to be measured alongside data on noise, vibration, road conditions, torque, and other factors during driving, thereby obtaining useful driving data. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 1 is a block diagram showing a resolver signal detection circuit according to the present invention.

[0029] Figure 2 1 is a circuit diagram showing a resolver signal detection circuit according to the present invention.

[0030] Figure 3 is a circuit diagram showing an embodiment of a detection circuit.

[0031] Figure 4is a circuit diagram showing an embodiment of a differential output circuit.

[0032] Figure 5 FIG. 1 is a waveform diagram showing a resolver signal detected after being processed by the resolver signal detection circuit of the present invention.

[0033] Figure 6 1 is a waveform diagram showing a resolver signal detected by a conventional detection method (common ground single-wire branch detection).

[0034] Figure 7 1 is a waveform diagram showing a resolver signal detected by a conventional detection method (differential probe detection).

[0035] Figure 8 It is a schematic diagram showing a resolver unit. DETAILED DESCRIPTION

[0036] refer to Figures 1 to 8 Embodiments of the resolver signal detection circuit of the present invention will be described. The following embodiments are merely illustrative and do not limit the technical scope of the present invention.

[0037] 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 illustrated resolver signal detection circuit 100 comprises: a plurality of pairs of branch lines 5c, 5d; 6c, 6d; 7c, 7d, branching off from signal lines 5a, 5b, 6a, 6b, 7a, 7b between the resolver 80 and the resolver-to-digital converter (RDC) 90; a four-stage circuit comprising a detection circuit 10, an inverting amplifier circuit 20, a low-pass filter circuit 30, and a differential output circuit 40.

[0038] In the first stage, detection circuit 10 receives a pair of angle signals output from output coils 6 and 7 of resolver 80 as differential signals via at least one pair of output branch lines 6c, 6d, and 7c, 7d from among multiple pairs of branch lines 5c, 5d, 6c, 6d, and 7c, 7d between resolver 80 and engine control unit (ECU) 210. It also receives a pair of excitation signals output from RDC 90 as differential signals via another pair of branch lines (excitation signal branch lines) 5c, 5d, and outputs a single-ended signal. Detection circuit 10 can detect a detection resolver signal including an angle signal without affecting the current of the control resolver signal within resolver unit 200. In this manual, the resolver signals, which consist of an excitation signal, a sine wave signal (including a sine wave and a carrier), and a cosine wave signal (including a cosine wave and a carrier), are separated and detected by branch lines 5c, 5d; 6c, 6d; and 7c, 7d. These signals are referred to as detection resolver signals, while the signals input and output to RDC 90 are referred to as control resolver signals. Furthermore, the resolver signals (the sine wave signal and the cosine wave signal) containing rotation angle information are referred to as angle signals.

[0039] 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 high-frequency noise from the single-ended signal after amplification or attenuation by 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 noise removal by the low-pass filter circuit 30, into a differential signal for output. This allows the detection resolver signal, including the angle signal, to be used outside the resolver unit 200.

[0040] The rotary transformer 80 is a 1-phase excitation 2-phase output type rotary transformer 80 ( Figure 8 ), outputting an angle signal corresponding to the motor's rotation angle, and comprising: an excitation coil 5, to which RDC 90 supplies the 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 RDC 90; this sine wave depends on the rotation angle; and 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 RDC 90. This cosine wave is substantially 90° phase-shifted relative to the sine wave contained in the sine wave signal from sine wave coil 6. Resolver 80 is not limited to a single-phase excitation, two-phase output type; a two-phase excitation, single-phase output type resolver (not shown) may also be used.

[0041] 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; and 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 this embodiment, there is no adverse effect on the control rotary transformer signals (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 detection rotary transformer signals 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 this embodiment, as 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.

[0042] exist Figure 1In the illustrated resolver signal detection circuit 100, detection circuit 10 includes: a first detection circuit 10 connected to excitation coil 5 via a pair of excitation signal branch lines 5c and 5d; a second detection circuit 10 connected to sine wave coil 6 via a pair of sine wave signal branch lines 6c and 6d; and a third detection circuit 10 connected to cosine wave coil 7 via a pair of cosine wave signal branch lines 7c and 7d. In resolver signal detection circuit 100, first detection circuit 10 is connected in series with first inverting amplifier circuit 20, first low-pass filter circuit 30, and first differential output circuit 40 to form an excitation signal processing unit 105; second detection circuit 10 is connected in series with second inverting amplifier circuit 20, second low-pass filter circuit 30, and second differential output circuit 40 to form a sine wave signal processing unit 106; and third detection circuit 10 is connected in series with third inverting amplifier circuit 20, third low-pass filter circuit 30, and third differential output circuit 40 to form a cosine wave signal processing unit 107.

[0043] Figure 2 The specific circuit diagram of the resolver signal detection circuit 100 is shown as an example. 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 achieved, 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".

[0044] Figure 2 The detection circuits 10 and 10a shown are instrumentation amplifiers 11. The differential signal (detected resolver signal) from resolver 80 is input to its two input terminals via a pair of branch lines 5c, 5d; 6c, 6d; and 7c, 7d. Instrumentation amplifier 11 then outputs a single-ended signal based on the detection circuit potential Vg within resolver signal detection circuit 100. Given the large amplitude of the detected resolver signal, instrumentation amplifier 11 preferably has an attenuation function. Figure 2 The instrumentation amplifier 11 shown (and equivalent to the one described later) Figure 3Circuit 10b of instrumentation amplifier 11, due to its high input impedance, can isolate and detect weak angle signals outside resolver unit 200 while minimizing the current flowing from resolver 80 into detection circuit 10. Furthermore, detection circuit 10 does not share a reference potential with resolver unit 200's ground line 9. Instead, it outputs a single-ended signal based on detection circuit potential Vg within resolver signal detection circuit 100. Therefore, in this embodiment, current reduction in resolver unit 200 and the generation of noise caused by sharing ground line 9 can be avoided. Furthermore, the angle signal can be isolated and detected while maintaining normal operation of resolver unit 200.

[0045] In this embodiment, the angle signal is directly input to Figure 2 Instrumentation amplifier 11 (or later described Figure 3 Detection amplifiers 12 and 13 are used to achieve high-impedance input. While ideally, the input impedance of an operational amplifier is infinite, it is actually several hundred MΩ to several hundred GΩ. This value is sufficiently large compared to the input and output impedances of resolver 80 and RDC 90 (several hundred Ω). Furthermore, in detection circuits 10, 10a, and 10b of this embodiment, the angle signal, which is a floating signal, is separated and detected using a low current due to the high impedance, thereby preventing any impact on the resolver control signals in resolver 80 and RDC 90.

[0046] Figure 3 As another embodiment of the detection circuit 10, a circuit (three-amplifier differential amplifier circuit) 10b equivalent to the instrumentation 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 resolver 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. Each output terminal of the operational amplifiers 12 and 13 is fed back to the inverting input terminal via resistors R19 and R25, and is 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 fed back 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 with 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), which reduces the number of operational amplifiers and reduces the cost.

[0047] Figure 2The inverting amplifier circuit 20 shown in FIG. 1 includes 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 input resistor R1 and a non-inverting input terminal connected to the detection circuit potential Vg within the resolver signal detection circuit 100; and 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. Feedback resistor R3 is a variable resistor. Inverting amplifier circuit 20 amplifies or attenuates the amplitude of the single-ended signal from detection circuit 10 using the gain factor (-R1 / R3), obtained by dividing input resistor R1 by feedback resistor R3 and then performing a negative inversion. The gain factor can be adjusted to any desired value, thereby controlling the amplitude of the signal output from inverting amplifier circuit 20. 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 within resolver signal detection circuit 100 , thereby determining the amplitude of the signal output from differential output circuit 40 .

[0048] 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, the 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 each connected to a reference potential Vg. In the present invention, the number of low-pass filter circuits determined by the number of integration circuit stages of resistors and capacitors is not limited to Figure 2 In addition, the low-pass filter circuit 30 is not limited to an active filter composed of an operational amplifier 31, and can also be a passive filter composed of a resistor, a capacitor and a coil.

[0049] 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 connected to the other ends of the resistors R11 and R13, respectively. The two output terminals of the fully differential amplifier 41 are respectively fed back 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 that of the resolver unit 200 outside the resolver unit 200 as a detection resolver signal. Furthermore, offset voltage input units 45 and 46 are included. When converting the single-ended signal from the low-pass filter circuit 30 into a differential signal, these units apply an offset voltage (adjustment voltage) Vos to the fully differential amplifier 41 (and differential conversion amplifiers 42 and 43). By applying offset voltage Vos via the offset voltage input units 45 and 46, the differential signal can be directly input to a single-power-supply resolver-to-digital converter (RDC) (not shown) connected to the subsequent stage of the differential output circuit 40, accurately measuring the rotation angle.

[0050] Figure 4 A differential conversion circuit 40b is shown as another embodiment of the differential output circuit 40. It is composed of differential conversion amplifiers 42 and 43 and differential conversion resistors R31-R45. Specifically, the circuit includes resistors R33 and R41, one end of which is connected to the low-pass filter circuit 30; resistors R31 and 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 ends of resistors R31 and R33; and an operational amplifier 43, whose inverting input terminal and non-inverting input terminal are respectively connected to the other ends of resistors R39 and R41. The output terminal of the operational amplifier 42 is feedback-connected to its inverting input terminal via resistor R35, and the output terminal of the operational amplifier 43 is feedback-connected to its non-inverting input terminal via resistor R43. The differential conversion circuit 40b also includes an offset voltage input unit 46. The non-inverting and inverting input terminals of the operational amplifiers 42 and 43 are respectively connected to the offset power supply via resistors R37 and R45.

[0051] 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 with packaged resistors. Figure 1 and Figure 2Although the subsequent stages of resolver signal detection circuit 100 are not shown, differential output circuit 40 is connected to an RDC (not shown) to calculate the numerical values ​​of the rotation angle and rotation speed of the target motor.

[0052] exist Figure 4 In the differential output circuit 40b, although 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 offset voltage input sections 45 and 46 are shown in the differential output circuits 40, 40a, and 40b, for example, when angle calculation is performed using a data latch or the calculation function of a high-performance oscilloscope, or when angle signal data is obtained by 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.

[0053] Hereinafter, embodiments of the resolver signal detection method of the present invention will be described.

[0054] In the resolver signal detection method, resolver unit 200 routinely measures the rotation angle by supplying an excitation signal to excitation coil 5 of resolver 80. Resolver 80 then outputs an angle signal corresponding to the motor's rotation angle to RDC 90 from output coils 6 and 7. Specifically, sine coil 6 of the output coil outputs a sinusoidal signal consisting of a carrier wave and a sine wave. The carrier wave has the same frequency as the excitation signal, and the sine wave depends on the rotation angle of resolver 80. Cosine coil 7 of the output coil outputs a cosine wave signal consisting of a carrier wave and a cosine wave. The carrier wave has the same frequency as the excitation signal, and the phase of the cosine wave is substantially 90° relative to the sine wave of the sine wave signal.

[0055] exist Figure 2 In the first stage detection circuit 10 shown, the signal lines 5a, 5b; 6a, 6b; 7a, 7b branched from the rotary transformer 80 and the RDC 90 are Figure 1Wires 5c, 5d; 6c, 6d; and 7c, 7d shown in the figure separate and detect the detection resolver signals, which include a pair of angle signals, into differential signals. Specifically, the excitation signal input from RDC 90 to excitation coil 5 is separated and detected via a pair of excitation signal branch lines 5c, 5d. The sine wave signal input from sine coil 6 to RDC 90 is separated and detected via a pair of sine wave signal branch lines 6c, 6d. The cosine wave signal input from cosine coil 7 to RDC 90 is separated and detected via a pair of cosine wave signal branch lines 7c, 7d. In detection circuit 10, a single-ended signal with a gain set to 1, for example, is output via instrumentation amplifiers 11, 10a or circuit 10b consisting of sense amplifiers 12-14 and sense resistors R19-R29.

[0056] Figure 2 The second-stage inverting amplifier circuit 20 shown receives a single-ended signal from the preceding detection circuit 10. This signal is then fed through input resistor R1 to the inverting input terminal of a gain amplifier (operational amplifier) ​​21. The output signal of operational amplifier 21 is fed back negatively via variable resistor R3, and inverting amplifier circuit 20 outputs the single-ended signal amplified or attenuated to the desired gain ratio (-R1 / R3).

[0057] 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 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 cutoff characteristics (cutoff frequency) and the phase characteristics (phase change) can be set by the filter resistors R5, R7, R9 and the capacitors C1 and C2. The cutoff 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 cutoff frequency (=1 / (2π(C1·C2·R7·R9)) 0.5 )) is set to 50kHz, and the phase change (delay phase) at a cutoff frequency of 50kHz is set to -90°. Furthermore, based on a rotational speed of 20,000 rpm (an electrical frequency of 330 Hz) for resolver 80, the design suppresses the phase change relative to a signal at a frequency of 400 Hz to below 0.1°. Furthermore, to ensure the conversion accuracy of the RDC connected to resolver signal detection circuit 100, the design suppresses the phase change at a typical excitation signal frequency of 10 kHz to below 40°.

[0058] exist Figure 2 In the fourth-stage differential output circuit 40 shown, the single-ended signal, after noise has been removed by the low-pass filter circuit 30 connected to the preceding stage, is input to the inverting input terminal of a fully differential amplifier (operational amplifier) ​​41 via resistor R11 and converted into a differential signal. A differential signal corresponding to the differential signal of resolver unit 200 is then output from the output terminal of operational amplifier 41 to an RDC (not shown). While the RDC can calculate the actual values ​​of the rotation angle and rotation speed based on the output differential signal, it cannot accurately calculate the rotation angle when the differential signal is centered around 0V. Therefore, an offset voltage Vos (e.g., 2.5V) is applied to the differential output circuit 40. The rotation angle and other values ​​calculated by the RDC can be transmitted as digital signals (serial or parallel) and speed pulses (e.g., ABZ phase signals for encoders) to a control IC, measurement IC, etc. (not shown) for use in evaluating motor control.

[0059] Although the differential output circuits 40 , 40 a , and 40 b are shown in the above embodiment, a single-ended signal may be directly output from the low-pass filter circuit 30 , and the rotation angle value may be calculated using an oscilloscope, a PC, or the like.

[0060] The following describes the voltage waveform of the angle signal (cosine signal) output from resolver 80 and the error reporting of RDC 90 by comparing an embodiment of the present invention with a comparative example based on the prior art. In both the embodiment and the comparative example, the cosine wave signal is evaluated. However, since the three pairs of signal lines 5a, 5b; 6a, 6b; and 7a, 7b are identical, the three pairs of branch lines 5c, 5d; 6c, 6d; and 7c, 7d are also identical, and the circuit configurations of the processing units 105, 106, and 107 for the excitation signal, sine wave signal, and cosine wave signal are also identical, it is expected that the excitation signal and sine wave signal can also obtain the same evaluation results as the cosine wave signal.

[0061] [Evaluation system]

[0062] The evaluation system of the embodiment is configured as follows: a resolver signal detection circuit 100 ( Figure 1 and Figure 2 ) is connected to the rear stage of 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 8Resolver unit 200 is not equipped with resolver signal detection circuit 100. Resolver unit 200 in the example evaluation system and the comparative example evaluation system includes resolver 80 (manufactured by Tamagawa Seiki Co., Ltd.) and RDC (RDC-100, manufactured by Atsense Co., Ltd.) 90. RDC 90 converts resolver signals into digital signals and also outputs rotation angle and rotation speed, and reports errors (signal degradation and signal loss).

[0063] [Example 1]

[0064] In the embodiment evaluation system ( Figure 1 ), the voltage waveform (angle signal) between the measurement points A2 and 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 measurement points A2 and B2 processed by the cosine wave signal processing unit 107 is treated as a single-ended signal by a differential input amplifier, insulated by an isolation amplifier, and measured by an oscilloscope through a BNC terminal. In order to input the RDC to the subsequent 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.

[0065] [Comparative Example 1]

[0066] In the comparative example evaluation system ( Figure 8 ), a passive probe was used with an oscilloscope to measure the voltage waveform (angle signal) between measurement point A1 on signal line 7a and measurement point G on ground line 9 of RDC 90 (Comparative Example 1). The voltage waveform in Comparative Example 1 is comparable to the voltage waveform in the conventional detection method described in Patent Document 1, namely, the single-line branch detection method using a common ground with the ECU.

[0067] [Comparative Example 2]

[0068] In the comparative example evaluation system ( Figure 8 ), 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).

[0069] In Example 1, measuring between A2 and B2 is equivalent to measuring between A1 and B1 via resolver signal detection circuit 100. In Comparative Example 1, one end is connected to measurement point G (ground line 9) and A1 is measured. In Comparative Example 2, A1 and B1 are measured. These three measurements can be said to be performed at essentially the same location. Furthermore, the voltage waveform between A1 and B1 on the pair of signal lines 7a and 7b is equivalent to the voltage waveform of the control resolver signal. Therefore, by measuring the voltage waveforms (detected resolver signals including angle signals) of Example 1 (the present invention), Comparative Example 1 (single-line branch detection with a common ground), and Comparative Example 2 (differential probe detection), it is possible to confirm whether there is any influence on the control resolver signal under various conditions.

[0070] [Evaluation results: Example 1]

[0071] The voltage waveform of Example 1 (between measurement 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 to ). Figure 5 (a) (horizontal axis: -25ms to 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) shows that a carrier with almost no noise was measured. In Example 1, there was no false report of signal degradation or signal loss from the RDC 90.

[0072] [Evaluation results: Comparative Example 1]

[0073] The voltage waveform of Comparative Example 1 (between measurement points A1-G) is shown in the figure below: Figure 6 (a) and 6(b). Figure 6 (a) (horizontal axis: -20ms to 20ms) and Figure 6 (a) (horizontal axis: -200 μs to 200 μs) shows 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.

[0074] [Evaluation results: Comparative Example 2]

[0075] The voltage waveform of Comparative Example 2 (between measurement points A1 and B1) is as follows: Figure 7 (a) and 7(b). Figure 7 (a) (horizontal axis: -50ms to 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) shows that noise is present at the peak of the carrier wave reflected inside the measured cosine wave. In Comparative Example 2, as in Comparative Example 1, the frequency of false reports of signal degradation due to noise from RDC 90 is high.

[0076] [Seminar]

[0077] 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 noise flowing in from the differential probe. It is believed that this noise influx caused signal degradation, and in Comparative Examples 1 and 2, the RDC 90 issued an erroneous report of signal degradation.

[0078] [in conclusion]

[0079] In Example 1, since a clear voltage waveform ( Figure 5 ), and there is no error report from the RDC 90, thus confirming that the resolver signal detection circuit 100 of the present invention can separate and detect a clear angle signal from which noise has been removed without adversely affecting the control resolver signal input and output to the RDC 90.

[0080] In Comparative Example 1, a large amount of noise was measured ( Figure 6 ), the noise was measured in Comparative Example 2 ( Figure 7 ), and frequent error reports from RDC 90 occurred. Therefore, it was confirmed that single-wire detection (Comparative Example 1) using a common ground with ECU 210, as in the prior art, and detection using a differential probe (Comparative Example 2) were unable to separate and detect clear angle signals, and adversely affected the control resolver signal.

[0081] Industrial Applicability

[0082] The resolver signal detection circuit according to the present invention uses the motor angle signal as a differential signal input without affecting the resolver signal used to control the resolver unit. Therefore, it can be used for signal detection other than resolvers, such as magnetic encoders, differential signal communication, and Wheatstone bridge circuits.

[0083] Description of Reference Numerals

[0084] 5: Excitation coil; 6: Output coil (sine wave coil); 7: Output coil (cosine wave coil); 5c, 5d: Branch lines (excitation signal branch line); 6c, 6d: Branch lines (output branch line, sine wave signal branch line); 7c, 7d: Branch lines (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 an 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: resolver; 90: resolver digital converter (RDC); 100: resolver signal detection circuit; 105: excitation signal processing unit; 106: sine wave signal processing unit; 107: cosine wave signal processing unit; 200: resolver unit; C1, C2: capacitors; R1: input resistor; R3: feedback resistor; R5-R9: filter resistors; R19-R29: detection resistors; 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 resolver and a resolver digital converter, the resolver having an excitation coil and an output coil, and the resolver digital converter receiving an angle signal corresponding to a rotation angle of the motor from the resolver; A detection circuit, wherein a pair of angle signals are input as differential signals from an output coil of a 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 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, wherein 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 that outputs a sine wave signal as an angle signal; and The cosine wave coil outputs a cosine wave signal as an angle signal, and the phase of the cosine wave signal is substantially offset by 90° relative to the sine wave signal of the sine wave coil; Multiple 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: The 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 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, wherein: 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 using the detection circuit potential within the resolver signal detection circuit as a reference.

6. The resolver signal detection circuit according to claim 1, wherein: The inverting amplifier circuit has: An input resistor, one end of the input resistor is connected to the detection circuit; a gain amplifier having an inverting input terminal connected to the other end of the input resistor and 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, wherein: 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, wherein: 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. The differential output circuit 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 into a detection circuit via at least one pair of output branch lines among a plurality of pairs of branch lines branched between the resolver and the resolver digital converter, and the detection circuit outputting a single-ended signal; The inverting amplifier circuit connected to the detection circuit amplifies or attenuates the single-ended signal from the detection circuit; A low-pass filter circuit connected to the inverting amplifier circuit removes noise from the single-ended signal after being amplified or attenuated by the inverting amplifier circuit; The differential output circuit connected to the low-pass filter circuit converts the single-ended signal after noise is removed by the low-pass filter circuit into a differential signal and outputs the differential signal.

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