Electronic circuit
Patent Information
- Application Number
- JP2023131700
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-08-11
- Publication Date
- 2025-02-25
Smart Images
Figure 2025026770000001_ABST
Abstract
Description
[Technical field]
[0001] The present invention relates to an electronic circuit, and is particularly useful when applied to the extraction of minute modulation components. [Background technology]
[0002] As a circuit applied when extracting a modulated component from a drive signal of a predetermined frequency, an electronic circuit shown in FIG. 2 has been conventionally known. As shown in FIG. 2, this electronic circuit has a drive circuit 1, a modulation means 2, and a signal processing unit II. Here, the drive circuit 1 generates a drive signal (A·sinω0) of a predetermined frequency, and amplifies this with an amplifier 6 and supplies it to the modulation means 2. The modulation means 2 modulates the drive signal (A·sinω0) with a physical quantity or chemical quantity based on a physical or chemical phenomenon, and outputs a modulated signal {A·sin(ω0+Δφ)} modulated with the modulation component (Δφ) at this time. Here, the physical quantity or chemical quantity based on a physical or chemical phenomenon is a quantity representing a frequency, phase, delay, etc., and modulation refers to the drive signal being influenced by these quantities to change the physical quantity or chemical quantity (the same applies hereinafter in this specification).
[0003] The signal processing means II receives the modulated signal {A·sin(ω0+Δφ)} and performs a predetermined signal processing to detect the physical or chemical quantity based on the modulated component (Δφ). More specifically, in the case of the electronic circuit shown in Fig. 2, the modulated means 2 outputs two types of modulated signals, positive and negative {±A·sin(ω0+Δφ)}, which are amplified by amplifiers 9 and 12 of the charge amplifier 3 of the signal processing section II, and then the subtractor 15 subtracts the negative modulated signal {-A·sin(ω0+Δφ)} from the positive modulated signal {+A·sin(ω0+Δφ)}. As a result, the subtractor 15 outputs a modulated signal {2·A·sin(ω0+Δφ)} having an amplitude twice that of the detected signal.
[0004] Capacitors 10 and 13 and feedback resistors 11 and 14 are connected in parallel to the operational amplifiers 9 and 12. Furthermore, the two types of modulation signals, positive and negative, {±A·sin(ω0+Δφ)}, become modulation signals {±A·cos(ω0+Δφ)} with a phase shift of 90° by passing through the operational amplifiers 9 and 12.
[0005] The modulation signal {2·A·cos(ω0+Δφ)}, which is the output signal of the subtractor 15, is multiplied by the carrier signal in the multiplier 4 to be synchronously detected. Here, the drive signal (A·sinω0) of a predetermined frequency obtained from the output side of the amplifier 6 is amplified, and the drive signal (A·sinω0) is shaped into a rectangular wave by the comparator 7 to become the carrier signal (A·sinω0). As a result, the multiplication signal {2·A·sin(ω0+Δφ)+(A·sinω0)} output from the multiplier 4 is a signal containing two types of components: a high-frequency component {A·sin(2ω0+Δφ)} that is twice the high-frequency carrier signal (A·sinω0), and a low-frequency component A·sin(Δφ) that represents the modulation amount Δφ. Therefore, if the high-frequency component based on the carrier signal is removed by the low-pass filter 5, a modulation component signal So based on the low-frequency component A·sin(Δφ) is obtained as the output of the low-pass filter 5. This modulated component signal So{=A·sin(Δφ)} represents a specific physical or chemical quantity.
[0006] In this way, a desired physical quantity based on a physical or chemical phenomenon can be detected.
[0007] 2, in order to accurately detect minute modulation components, it is necessary to increase as much as possible the gain of the operational amplifiers 9 and 12. For this reason, the resistance values of the feedback resistors 11 and 14 must be large, for example, about 100 MΩ, in order to increase the gain of the operational amplifiers 9 and 12.
[0008] When forming feedback resistors 11 and 14 with such high resistance values, the area occupied by feedback resistors 11 and 14 becomes enormous when using conventional manufacturing methods, and therefore it is necessary to fabricate ultra-high resistance elements by adding a manufacturing process.
[0009] However, such ultra-high resistance elements are not only difficult to adjust to the desired resistance value, but also require a large installation area and are expensive. As a result, this becomes a fatal flaw when the signal processing section II, which amplifies the minute signal obtained from the modulation component to a sufficient level in this type of electronic circuit and includes a charge amplifier 3 equipped with feedback resistors 11 and 14, is formed as an IC circuit. The signal processing section II in the electronic circuit shown in Figure 2 is composed of an IC circuit together with the drive circuit 1.
[0010] The following documents are known as known documents that disclose an operational amplifier having a high-resistance feedback resistor for amplifying a small signal to a sufficiently large signal. [Prior art documents] [Patent documents]
[0011] [Patent Document 1] JP 2023-013259 A Summary of the Invention [Problem to be solved by the invention]
[0012] In view of the problems with the conventional technology described above, an object of the present invention is to provide an electronic circuit having a charge amplifier that can achieve a high resistance value for a feedback resistor connected to an operational amplifier with a simple and as compact a configuration as possible, and that can be easily realized as an IC circuit. [Means for solving the problem]
[0013] The present invention, which achieves the above object, is based on the following findings.
[0014] A switched capacitor is considered as a small resistive element that can obtain a high resistance value. A switched capacitor is an electronic circuit that generally combines multiple capacitors and multiple switches to limit current or voltage like a resistor, and can function as a resistive element with a desired high resistance value by controlling the frequency of the switching signal that drives the switch. Here, the higher the resistance value, the more it is necessary to switch the switch with a switching signal of a higher frequency.
[0015] A block diagram of an electronic circuit in which the feedback resistor is formed by a switched capacitor is shown in Fig. 3. As shown in the figure, the signal processing section III of this example, which corresponds to the signal processing section II in Fig. 2, can also be formed by an IC circuit together with the drive circuit 1. The feedback resistors 21 and 24 of the charge amplifier 13 formed by the switched capacitor SC are connected to the operational amplifiers 9 and 10 in place of the feedback resistors 11 and 14 of the charge amplifier 3 shown in Fig. 2.
[0016] In Fig. 3, the configuration of other parts except for the feedback resistors 21 and 24 is basically the same as that of the sensor shown in Fig. 2. Therefore, in Fig. 3, the same parts as those in Fig. 2 are given the same reference numbers, and duplicated explanations will be omitted.
[0017] Incidentally, when the feedback resistors 21, 24 are formed by switched capacitor SC, it is necessary to switch the switch of the switched capacitor SC with a high-frequency switching signal. In this case, the frequency of the switching signal needs to be several tens of times higher than the frequency of the carrier signal (A·sinω0) in order to perform good synchronous detection. Therefore, it is impossible to use the carrier signal (A·sinω0) as it is as a switching signal for the switched capacitor SC.
[0018] Therefore, in order to make the switched capacitor SC into a desired high-resistance element, it is conceivable to provide an internal oscillator 16 that outputs a high-frequency signal (for example, about 1 MHz) inside the signal processing circuit III, and to control the on / off switching of the switch of the switched capacitor SC with the output signal {clock signal (N (=rational number; the same applies below) × ω0)} of this internal oscillator 16.
[0019] However, it has been found that in this case, a new problem occurs as described below. That is, since the carrier signal (A·sinω0) and the output signal {clock signal (N×ω0)} of the internal oscillator 16 in this case are asynchronous, the output signal of the subtractor 15 is asynchronous with the modulation signal {2·A·cos(ω0+Δφ+φ beat )}. That is, φ beat This results in low frequency noise due to the generation of
[0020] As a result, the multiplier 4 multiplies the carrier signal (A·sinω0) by the modulation signal {2·A·cos(ω0+Δφ+φ}, which is the output signal of the subtractor 15 containing noise components. beat )} is multiplied by the signal A·sinω0 to obtain a synchronous detection. Here, the drive signal (A·sinω0) of a predetermined frequency obtained from the output side of the amplifier 6 is amplified and shaped into a rectangular wave by the comparator 7 to obtain the carrier signal (A·sinω0). As a result, the multiplier 4 outputs a high-frequency component {A·sin(2ω0+Δφ)} based on the high-frequency carrier signal (A·sinω0) and a noise component φ beat The low-frequency component A·sin(Δφ+φ beat Therefore, if the high frequency components based on the carrier signal are removed by the low pass filter 5, the low frequency components A·sin(Δφ+φ) are output from the low pass filter 5. beat ), a modulated component signal So based on the modulated component signal So is obtained. beat Therefore, a noise component based on the above-mentioned is included, and accurate detection of the modulation amount component is hindered.
[0021] More specifically, since the switched capacitor SC performs sampling operation with the on / off of the switch, if the phase comparison clock based on the carrier signal (A·sinω0) is the reference 0° and the frequency of the switching signal is ωsck, the rising edge of the sampling clock will go back and forth between ±ω0 / (ωsck×180°). For example, if ω0=50kHz and ωsck=600.1kHz, the rising edges of ω0 and ωsck will go back and forth between a phase of 50kHz / 600.1kHz×180°=±15° with a period of |12×50kHz-600.1kHz|=100Hz. If the phase is compared by the multiplier 4 while still including this phase modulation component, it will be observed as a noise component in the modulation component signal So.
[0022] It was found that new problems arise when forming the high-resistance feedback resistors 21, 24 of the operational amplifiers 9, 12 with switched capacitors in order to realize a high-gain charge amplifier 23. In other words, it is not possible to simply apply the synchronous detection carrier signal (A·sinω0) to the switching signal of the switched capacitor, and it has become clear that it is essential to solve the newly identified problems as described above.
[0023] The electronic circuit according to the first aspect of the present invention based on the above findings comprises: An electronic circuit having a drive circuit that generates a drive signal of a predetermined frequency, a modulation means that modulates the drive signal with a physical quantity or a chemical quantity based on a physical or chemical phenomenon and outputs the modulated modulated signal, and a signal processing section that receives the modulated signal, performs predetermined signal processing, and detects the physical quantity or the chemical quantity, The signal processing unit includes: The modulation signal is amplified by an operational amplifier having a feedback resistor formed by a switched capacitor, and the amplified modulation signal is multiplied by a carrier signal formed by the drive signal to generate a multiplication signal, and a low-frequency component of the multiplication signal is extracted by a low-pass filter to generate a modulation component signal representing a component based on an amount of change of the modulation signal relative to the drive signal; The present invention is characterized in that it includes a phase locked loop circuit that uses the carrier signal as an input signal to generate a new output signal that is in phase with the input signal and has a frequency that is a rational multiple of the input signal, and that is configured to use the output signal as a switching signal that switches the switches of the switched capacitor.
[0024] The electronic circuit according to the second aspect comprises: In the electronic circuit according to the first aspect, The modulation signal is generated in two types, positive and negative, and the positive and negative modulation signals are amplified by two systems of the operational amplifiers and their phases are shifted by 90°. Thereafter, the modulation signal obtained by performing a differential operation on the positive modulation signal and the negative modulation signal is multiplied by the carrier signal to generate the multiplied signal, and the multiplied signal is supplied to the low-pass filter.
[0025] The sensor according to the third aspect comprises: In the electronic circuit according to the first or second aspect, The drive circuit and the signal processing section are formed by an IC circuit. Effect of the Invention
[0026] In the present invention, the feedback resistor of the operational amplifier is formed by a switched capacitor, so that a feedback resistor with a high resistance value capable of securing a sufficient amplification factor in the operational amplifier can be formed small and inexpensively. Furthermore, when the drive signal is used as a carrier signal for synchronous detection, a phase locked loop circuit is provided that uses the carrier signal as an input signal, and the switched capacitor is driven by an output signal of the phase locked loop circuit that is in phase with the carrier signal and has a frequency N times that of the carrier signal. This not only makes it easy to obtain a desired high resistance, but also prevents noise components from occurring in the signal after synchronous detection, making it possible to detect the modulation amount component with high accuracy. [Brief description of the drawings]
[0027] [Figure 1] FIG. 2 is a block diagram showing an electronic circuit according to an embodiment of the present invention. [Diagram 2]FIG. 1 is a block diagram showing an electronic circuit according to the prior art. [Diagram 3] FIG. 1 is a block diagram showing another electronic circuit according to the prior art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 is a block diagram showing an electronic circuit according to an embodiment of the present invention. In Fig. 1, the same parts as those in Figs. 2 and 3 are given the same numbers, and duplicated explanations will be omitted.
[0029] As shown in FIG. 1, the phase-locked loop (PLL) circuit 20 shapes the driving signal A×sin(ω0) that drives the modulation means 8 into a rectangular wave by the comparator 7, and generates a new output signal that is in phase with the input signal and has a frequency N times higher (N×ω0=ωsck) using the carrier signal (A·sinω0) used for synchronous detection by the multiplier 4 as an input signal. The switched capacitors SC that form the feedback resistors 31 and 34 in this embodiment are driven by the output signal of the phase-locked loop 20 as a switching signal. That is, each switch is controlled to be on and off by a switching signal having a frequency N times higher than that of the carrier signal (A·sinω0). Here, by increasing N, the frequency ωsck of the switching signal can be made sufficiently high.
[0030] As a result, the gain of the operational amplifiers 9 and 12 of the charge amplifier 33 can be made sufficiently large, and the operational amplifiers 9 and 12 can output a modulation signal {±A·sin(ω0+Δφ)} having a sufficiently large amplitude. Here, the operational amplifiers 9 and 12 use the output signal of the phase-locked loop circuit 20 as a switching signal for the switched capacitor SC, so not only can the carrier signal (A·sinω0) be used as the switching signal for the switched capacitor SC, but the switching signal has a frequency ω0 that is N times that of the carrier signal (A·sinω0) and is precisely in phase with the carrier signal (A·sinω0). As a result, the modulation signal {±A·sin(ω0+Δφ)}, which is the output signal of the operational amplifiers 9 and 12, does not include noise φbeat as in the case shown in FIG. 3.
[0031] Therefore, the subtractor 15 outputs the modulated signal {2·A·sin(ω0+Δφ)}, and the multiplied signal {2·A·sin(ω0+Δφ)+(A·sinω0)} output after synchronous detection by the multiplier 4 is a signal containing two types of components: a high-frequency component {A·sin(2ω0+Δφ)} that is twice the high-frequency carrier signal (A·sinω0), and a low-frequency component A·sin(Δφ) that represents only the modulated component (Δφ). Therefore, if the high-frequency component based on the carrier signal is removed by the low-pass filter 5, the output of the low-pass filter 5 is a modulated component signal So{=A·sin(Δφ)} that is precisely based on the low-frequency component A·sin(Δφ) with the noise φbeat removed.
[0032] In this manner, in this embodiment, the feedback resistors 31, 34 of the operational amplifiers 9, 12 are formed using the switched capacitors SC, so that the feedback resistors 31, 34 having high resistance values capable of ensuring a sufficient amplification factor in the operational amplifiers 9, 12 can be formed small and inexpensively.
[0033] Furthermore, when the drive signal (A·sinω0) for driving the modulation means 2 is used as a carrier signal for synchronous detection, a phase locked loop 20 is provided which uses the carrier signal as an input signal, and the switched capacitor SC is driven by an output signal from the phase locked loop 20 which is in phase with the carrier signal and has a frequency N times that of the carrier signal. This not only makes it easy to obtain a desired high resistance, but also prevents noise φbeat from occurring in the signal after synchronous detection, making it possible to obtain a highly accurate modulated control component signal So which accurately reflects the detection amount. That is, the multiplication signal {2·A·sin(ω0+Δφ)+(A·sinω0)} obtained by synchronous detection is a signal that contains only two types of components: a high-frequency component {A·sin(2ω0+Δφ)} that is twice the high-frequency carrier signal (A·sinω0), and a low-frequency component A·sin(Δφ) that represents the modulation component (Δφ), and by removing the high-frequency component based on the carrier signal using low-pass filter 5, a modulation component signal So based only on the low-frequency component A·sin(Δφ) is obtained as the output of low-pass filter 5. This modulation component signal So{=A·sin(Δφ)} is a signal that represents the inherent physical quantity (angular velocity) of the detection target. [Explanation of symbols]
[0034] I Signal Processing Section 1 Drive circuit 2 Modulation Method 4. Multiplier 5. Low-pass filter 9,12 Operational Amplifiers 20 Phase-locked (PLL) circuit 30 Charge Amplifier 31,34 Feedback resistor (SC)
Claims
1. An electronic circuit having a drive circuit that generates a drive signal of a predetermined frequency, a modulation means that modulates the drive signal with a physical quantity or a chemical quantity based on a physical or chemical phenomenon and outputs the modulated modulated signal, and a signal processing section that receives the modulated signal, performs predetermined signal processing, and detects the physical quantity or the chemical quantity, The signal processing unit includes: The modulation signal is amplified by an operational amplifier having a feedback resistor formed by a switched capacitor, and the amplified modulation signal is multiplied by a carrier signal formed by the drive signal to generate a multiplication signal, and a low-frequency component of the multiplication signal is extracted by a low-pass filter to generate a modulation component signal representing a component based on an amount of change of the modulation signal relative to the drive signal; a phase locked loop circuit that receives the carrier signal as an input signal and generates a new output signal having the same phase as the input signal and a rational multiple of the frequency of the input signal, and that is configured to use the output signal as a switching signal for switching and driving a switch of the switched capacitor.
2. 2. The electronic circuit according to claim 1, the electronic circuit is configured to generate two types of modulation signals, positive and negative, amplify the positive and negative modulation signals by two systems of the operational amplifiers, and shift the phases of the signals by 90°, and then multiply the modulation signal obtained by differentially calculating the positive modulation signal and the negative modulation signal by the carrier signal to generate the multiplied signal, and supply the multiplied signal to the low-pass filter.
3. 3. The electronic circuit according to claim 1, The electronic circuit is characterized in that the drive circuit and the signal processing section are formed by an IC circuit.
Citation Information
Patent Citations
Semiconductor device
JP2023013259A