Conversion circuit and electronic circuit

Abstract

The invention relates to a conversion circuit and an electronic circuit. A conversion circuit for converting an input current into an output voltage includes: a first terminal that is an input unit for the input current; the second terminal is a grounding terminal; a third terminal that is an output unit for outputting the voltage and that supplies the power supply voltage via a power supply resistor; a first resistor, one end of which is connected to the first terminal and the other end of which is connected to the third terminal; and a voltage regulator that detects a deviation between the voltage of the first terminal and a preset reference voltage, and when the voltage of the first terminal is higher than the reference voltage, adjusts the amount of current flowing from the third terminal to the second terminal according to the magnitude of the deviation, reduces the voltage of the third terminal, and adjusts the amount of current flowing from the third terminal to the second terminal. The voltage of the first terminal is maintained as a reference voltage, and the gain of the conversion circuit is determined by the first resistor.

Description

Technical Field

[0001] The present invention relates to a conversion circuit and an electronic circuit. Background Art

[0002] Circuits and components used as a power supply include, for example, a condenser microphone unit, a sensor, etc. For example, when it is a condenser microphone, it generally adopts a structure integrated with an FET (Field Effect Transistor), or an external FET is used. Therefore, when using a condenser microphone, it is necessary to supply a power supply voltage to the FET.

[0003] Figure 15 FIG. showing an example of a microphone circuit and input / output signals in the prior art. When the microphone mic is a condenser microphone, as Figure 15 shown, a power supply voltage Vcc is supplied via a resistor R L In addition, an FET is included inside the microphone mic. Also, an input signal (reference numeral g902) collected by the microphone mic is output via a capacitor C O When the change in the current flowing through the microphone mic is ΔImic and the change in the power supply voltage Vcc caused by noise is ΔVcc, the voltage change ΔVout of the output signal output from the output terminal Vout is represented by ΔVcc - R L ×ΔImic. When noise (reference numeral g901) is mixed in the power supply, since the ΔVout includes the ΔVcc term, power supply noise (reference numeral g903) is superimposed on the output signal.

[0004] In order to cope with the noise superimposed on the output of such a condenser microphone, the following solution has been proposed. It is configured to use an operational amplifier, and by capacitive coupling with the internal power supply wiring, apply the noise component superimposed on the power supply voltage Vcc to the non-inverting input terminal of the operational amplifier, thereby using the operational amplifier to cancel the noise component (for example, see Patent Document 1).

[0005] The fundamental background of the proposed solution for such a circuit structure aimed at canceling the noise component lies not only in that power supply noise is easily superimposed on the signal, but also in the case where the sensor and the electronic circuit (such as an amplifier circuit) are often separately arranged. For example, when an amplifier circuit is arranged near the sensor, in addition to applying a weak voltage for the sensor, a stable power supply for the amplifier circuit is also necessary. As a result, the sensor and the electronic circuit are separately arranged, and external noises such as power supply noise and transmission line noise are superimposed on the signal.

[0006]

Prior Art Documents

[0007]

Patent Documents

[0008]

Patent Document 1

[0009]

Technical Problem to be Solved by the Invention

[0010] However, in the technology described in Patent Document 1, it is necessary to provide a plurality of external circuit elements for a microphone or a microphone unit. Moreover, the circuit described in Patent Document 1 is a dedicated circuit for a condenser microphone and is difficult to be applied to other elements such as sensors.

[0011] The present invention has been made in view of the above problems, and an object thereof is to provide a conversion circuit and an electronic circuit capable of reducing noise superposition.

[0012]

Technical Solution for Solving the Technical Problem

[0013] (1) To achieve the above object, a conversion circuit according to one aspect of the present invention is a conversion circuit that converts an input current into an output voltage, and includes: a first terminal, which is an input portion of the input current; a second terminal, which is a ground terminal; a third terminal, which is a power supply portion of the conversion circuit and an output portion of the output voltage; a first resistor, one end of which is connected to the first terminal and the other end of which is connected to the third terminal; and a voltage regulator, which is controlled as follows: detecting a deviation between the voltage of the first terminal and a preset reference voltage, and when the voltage of the first terminal is higher than the reference voltage, adjusting the amount of current flowing from the third terminal to the second terminal according to the magnitude of the deviation to maintain the voltage of the first terminal at the reference voltage, and determining the gain through the first resistor.

[0014] (2) Further, in the conversion circuit of the above (1), the current flowing from the third terminal to the second terminal is a sink current, and the sink current is supplied to the third terminal from outside the conversion circuit.

[0015] (3) In addition, in the circuit of the above (1) or (2), the following technical solution may be adopted: the voltage regulator includes a variable shunt regulator, a reference terminal of the variable shunt regulator is connected to the first terminal, an anode terminal of the variable shunt regulator is connected to the second terminal, and a cathode terminal of the variable shunt regulator is connected to the third terminal.

[0016] (4) In addition, in the conversion circuit of the above (1) or (2), the following technical solution can be adopted: The voltage regulator includes: an operational amplifier and a first NPN transistor. The non-inverting input terminal of the operational amplifier is connected to the first terminal, the reference voltage is input to the inverting input terminal of the operational amplifier, the output terminal of the operational amplifier is connected to the base of the first transistor, the collector of the first transistor is connected to the third terminal, and the emitter of the first transistor is connected to the second terminal.

[0017] (5) In addition, in the conversion circuit of the above (1) or (2), the following technical solution can be adopted: The voltage regulator includes: a first NPN transistor, a second NPN transistor, and a second resistor. The base of the first transistor is connected to the first terminal, the emitter of the first transistor is connected to the second terminal via the second resistor, the emitter of the first transistor is connected to the base of the second transistor, the collector of the first transistor is connected to the collector of the second transistor, the collector of the second transistor is connected to the third terminal, and the emitter of the second transistor is connected to the second terminal.

[0018] (6) In addition, in the conversion circuit of the above (1) or (2), the following technical solution can be adopted: The voltage regulator includes: a first NPN transistor, a second NPN transistor, a third PNP transistor, a fourth NPN transistor, a second resistor, a third resistor, and a fourth resistor. The base of the first transistor is connected to the first terminal, the emitter of the first transistor is connected to the second terminal via the second resistor, the emitter of the first transistor is connected to the base of the second transistor, the collector of the first transistor is connected to the third terminal, the emitter of the second transistor is connected to the second terminal, the collector of the second transistor is connected to the third terminal via the third resistor, the collector of the second transistor is connected to the base of the third transistor, the emitter of the third transistor is connected to the third terminal, the collector of the third transistor is connected to the base of the fourth transistor, the collector of the third transistor is connected to the second terminal via the fourth resistor, the collector of the fourth transistor is connected to the third terminal, and the emitter of the fourth transistor is connected to the second terminal.

[0019] (7) In addition, in the conversion circuit of the above (1) or (2), the following technical solutions can be adopted: The voltage regulator includes: a first NPN transistor, a second NPN transistor, a third PNP transistor, a second resistor, and a third resistor. The base of the first transistor is connected to the first terminal. The emitter of the first transistor is connected to the second terminal via the second resistor. The emitter of the first transistor is connected to the base of the second transistor. The collector of the first transistor is connected to the third terminal. The emitter of the second transistor is connected to the second terminal. The collector of the second transistor is connected to the third terminal via the third resistor. The collector of the second transistor is connected to the base of the third transistor. The emitter of the third transistor is connected to the third terminal. The collector of the third transistor is connected to the second terminal.

[0020] (8) In addition, in the conversion circuit of the above (1) or (2), the following technical solutions can be adopted: The voltage regulator includes: a first field-effect transistor, a second field-effect transistor, and a second resistor. The gate of the first field-effect transistor is connected to the first terminal. The source of the first field-effect transistor is connected to the second terminal via the second resistor. The source of the first transistor is connected to the gate of the second field-effect transistor. The drain of the first field-effect transistor is connected to the drain of the second field-effect transistor. The drain of the second field-effect transistor is connected to the third terminal. The source of the second field-effect transistor is connected to the second terminal.

[0021] (9) In addition, in the conversion circuit of the above (1) or (2), the following technical solutions can be adopted: The voltage regulator includes: an operational amplifier and a diode. The non-inverting input terminal of the operational amplifier is connected to the first terminal. The reference voltage is input to the inverting input terminal of the operational amplifier. The output terminal of the operational amplifier is connected to the anode of the diode. The cathode of the diode is connected to the second terminal.

[0022] (10) In addition, in the conversion circuit of the above (9), the following technical solutions can be adopted: The positive power supply terminal of the operational amplifier is connected to the third terminal. The negative power supply terminal of the operational amplifier is connected to the second terminal.

[0023] (11) In addition, in the conversion circuit of at least one of the above (1) to (10), the following technical solutions can be adopted: The output impedance of the conversion circuit is 1 Ω or less.

[0024] (12) Additionally, for the conversion circuit of at least one of the above (1) to (10), the following technical solutions can be adopted: having at least one of the following: a power supply resistor with one end connected to the third terminal and the other end connected to the power supply voltage; a capacitor with one end connected to the third terminal and the other end serving as the output terminal to the load side; a capacitor with one end connected to the third terminal and the other end connected to the first terminal.

[0025] (13) To achieve the above objective, an electronic circuit related to a technical solution of the present invention includes the conversion circuit of at least one of the above (1) to (12) and a sensor connected to the input section.

[0026] (14) In the electronic circuit of the above (13), the following technical solution can be adopted: the sensor is one of a condenser microphone, a piezoelectric sensor, a pressure sensor, an acceleration sensor, an optical sensor, and a quartz crystal resonator.

[0027]

Invention Effects

[0028] According to (1) to (14), the superposition of noise can be reduced. Description of the Drawings

[0029] Figure 1 A diagram showing the equivalent circuit of a condenser microphone, a power supply circuit, and a condenser microphone unit at the operating point.

[0030] Figure 2 A diagram showing an example of the electronic circuit of the first embodiment.

[0031] Figure 3 A diagram showing an example of the electronic circuit of the second embodiment.

[0032] Figure 4 A diagram showing a modification example of the second embodiment.

[0033] Figure 5 A diagram showing an example of the signal waveform when collecting an audio signal using a microphone unit.

[0034] Figure 6 A diagram showing an example of the result of measuring the power supply voltage variation suppression ratio.

[0035] Figure 7 A diagram showing an example of the result of measuring the relationship between the power supply voltage Vcc and the output voltage output from the output terminal Vout in the electronic circuit.

[0036] Figure 8 A diagram showing an example of the structure of the electronic circuit of the third embodiment.

[0037] Figure 9A diagram showing the relationship between the power supply voltage Vcc and the output voltage output from the output terminal Vout in the third embodiment.

[0038] Figure 10 A diagram showing a structural example of the electronic circuit in the fourth embodiment.

[0039] Figure 11 A diagram showing the relationship between the power supply voltage Vcc and the output voltage output from the output terminal Vout in the fourth embodiment.

[0040] Figure 12 A diagram showing a structural example of the electronic circuit in the fifth embodiment.

[0041] Figure 13 A diagram showing the relationship between the power supply voltage Vcc and the output voltage output from the output terminal Vout in the fifth embodiment.

[0042] Figure 14 A diagram showing a structural example of the electronic circuit when the sensor is a quartz crystal resonator.

[0043] Figure 15 A diagram showing an example of a microphone circuit and input / output signals in the prior art.

[0044] Figure 16 A diagram showing a structural example of the electronic circuit in the sixth embodiment.

[0045] Figure 17 A diagram showing a structural example of the electronic circuit in the seventh embodiment.

[0046] Explanation of reference numerals

[0047] 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G... Electronic circuits

[0048] 2, 2E... Sensors

[0049] 3, 3A, 3B, 3C, 3D, 3E, 3F... Conversion circuits

[0050] C f ,C O ... Capacitors

[0051] D... Diodes

[0052] R a ,R b ,R c ,R d ,R e ,R f ,R g ,R h ,R i ,RL …resistors,

[0053] Tr1, Tr21…field effect transistors,

[0054] Tr2, Tr3, Tr4, Tr5, Tr6, Tr7, Tr8, Tr9, Tr10, Tr11…transistors,

[0055] FET1, FET2…field effect transistors,

[0056] 31, 31A…operational amplifiers,

[0057] 32…variable shunt regulators,

[0058] pin1…the first terminal,

[0059] pin2…the second terminal,

[0060] pin3…the third terminal,

[0061] C m …condenser microphones,

[0062] X…quartz crystal resonators,

[0063] V ref …reference power supplies,

[0064] Vcc…power supply voltage,

[0065] Vout…output terminal / output voltage,

[0066] 101, 101A, 101B, 101C, 101D, 101E, 101F…voltage regulators,

[0067] Vpin1…the voltage of the first terminal. Detailed implementation manners

[0068] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, in the drawings used in the following description, the scales of the respective components have been appropriately changed so that each component can be recognized at a discernible size.

[0069] In addition, in all the drawings illustrating the embodiments, components having the same functions are denoted by the same reference numerals, and repeated descriptions are omitted.

[0070] Moreover, "based on XX" as described in the present application means "at least based on XX", and also includes cases where other elements are also based on in addition to XX. In addition, "based on XX" is not limited to the case of directly adopting XX, but also includes cases based on operations or processing performed on XX. "XX" is any element (for example, any information).

[0071] First, a general circuit when using a condenser microphone and an equivalent circuit of the condenser microphone unit at the operating point will be described.

[0072] Figure 1 A diagram showing the condenser microphone, the power supply circuit, and the equivalent circuit of the condenser microphone unit at the operating point.

[0073] The diagram with reference numeral g11 is an example of the condenser microphone and the power supply circuit. As shown in the diagram with reference numeral g11, the condenser microphone unit ECM includes, for example: a condenser microphone C m , a resistor R m , and an FET Q m . One end of the condenser microphone C m is connected to one end of the resistor R m and the gate of the FET Q m , and the other end is grounded (GND). The other end of the resistor R m is grounded. The drain of the FET Q m is connected to the resistor R L and one end of the capacitor C O , and the source is grounded. The other end of the resistor R L is connected to the power supply voltage Vcc. The other end of the capacitor C O is connected to the output terminal V out .

[0074] The resistor R m is the input bias resistor of the FET Q m . The FET Q m functions as an impedance converter. The resistor R L is a load resistor that supplies the power supply voltage Vcc to the FET Q m . The capacitor C O is a capacitor for blocking the AC component.

[0075] The diagram with reference numeral g12 is the equivalent circuit of the condenser microphone unit ECM at the operating point. The equivalent circuit of the condenser microphone unit ECM at the operating point can be represented by a condenser microphone C m , a resistor R m , a current source g m , and a fixed resistor R mo .

[0076] As described using Figure 1 , the equivalent circuit of the condenser microphone unit ECM can be regarded as a current source. Therefore, in order to reduce the power supply noise ΔVcc mixed in the power supply voltage Vcc, a circuit structure whose output term does not include the power supply noise ΔVcc can be adopted.

[0077] (First Embodiment)

[0078] Figure 2 A diagram showing an example of an electronic circuit according to the first embodiment. As Figure 2 shown, the electronic circuit 1 includes a sensor 2 and a conversion circuit 3. In addition, in each of the following embodiments, a microphone unit is used as an example of the sensor 2 for description, but the sensor 2 is not limited to the microphone unit. As will be described later, for example, it can be a piezoelectric sensor or the like.

[0079] The sensor 2 is, for example, a condenser microphone unit ECM. For example, the sensor 2 includes: a condenser microphone C m , a resistor R a , and a field effect transistor Tr1.

[0080] The conversion circuit 3 includes, for example: a capacitor C f , a resistor R b (first resistor), a reference power supply V ref , an operational amplifier 31, and a transistor Tr2 (first transistor). In addition, the conversion circuit 3 may further include a resistor R L (power supply resistor) and a capacitor C O .

[0081] The voltage regulator 101 includes, for example: an operational amplifier 31, a transistor Tr2 (first transistor), and a reference power supply V ref . In addition, the conversion circuit 3 may not include the anti-oscillation capacitor C f .

[0082] Next, the connection structure of the conversion circuit 3 will be described.

[0083] One end of the capacitor C f is connected to one end of the resistor R b , one end of the resistor R L , one end of the capacitor C O , and the collector of the transistor Tr2, and the other end is connected to the other end of the resistor R b , the non-inverting input terminal (+) of the operational amplifier 31, and the output of the sensor 2.

[0084] In the operational amplifier 31, its inverting input terminal (-) is connected to the positive electrode of the reference power supply V ref , and its output terminal is connected to the base of the transistor Tr2. In addition, the positive power supply terminal +V of the operational amplifier 31 is connected to one end of the resistor R L , its negative power supply terminal -V is grounded, and the emitter of the transistor Tr2 is grounded.

[0085] The negative electrode of the reference power supply V ref is grounded. In addition, the reference power supply V refFor example, it can be a Zener diode circuit. In this case, for example, it can be as follows: One end of another first resistor (not shown) is connected to one end of resistor R L One end of the other first resistor is connected to the cathode of another first Zener diode (not shown) and the inverting input terminal of the operational amplifier 31, and the anode of the other first Zener diode is grounded.

[0086] Resistor R L The other end is connected to the power supply voltage Vcc.

[0087] Capacitor C O The other end is connected to the output terminal Vout.

[0088] Next, a first terminal, a second terminal, and a third terminal are defined in the conversion circuit 3.

[0089] In the conversion circuit 3, the intersection of the output terminal of the sensor 2 (the drain of the field effect transistor Tr1), the other end of the resistor R b the other end of the capacitor C f the other end, and the non-inverting input terminal of the operational amplifier 31 is defined as the first terminal pin1. Thus, the first terminal pin1 is the input part of the conversion circuit 3. And the voltage of the first terminal pin1 is set as Vpin1.

[0090] The intersection of the emitter of the transistor Tr2 and the negative pole of the reference power supply V ref is defined as the second terminal pin2. In addition, the second terminal pin2 is grounded. The negative power supply terminal -V of the operational amplifier 31 is connected to the second terminal pin2.

[0091] Resistor R b One end of the capacitor C f One end, the collector of the transistor Tr2, one end of the resistor R L One end of the capacitor C O One end of the intersection is defined as the third terminal pin3. Thus, the third terminal pin3 is the power supply part and output part of the conversion circuit 3. The positive power supply terminal +V of the operational amplifier 31 is connected to the third terminal pin3.

[0092] In addition, instead of connecting the positive power supply terminal +V and the negative power supply terminal -V of the operational amplifier 31 to the third terminal pin3 and the second terminal pin2, they can be connected to other external power supplies (not shown).

[0093] In the conversion circuit 3, the gain (R b Is / Is) is determined by the resistor R bA decision. In addition, the current Is is the signal current of the condenser microphone unit ECM. In the conversion circuit 3, the operational amplifier 31 is, for example, an OP amplifier and functions as an error circuit that detects the error between the signal input to the non-inverting input terminal and the voltage of the reference power supply. Through the conversion circuit 3, the signal current of the condenser microphone unit ECM is converted into a voltage. The voltage regulator 101 controls the output voltage. In addition, the voltage regulator 101 controls the output voltage by drawing in current.

[0094] That is to say, the voltage regulator 101 is controlled in the following manner: it detects the deviation between the voltage of the first terminal and a preset reference voltage. When the voltage of the first terminal is higher than the reference voltage, according to the magnitude of the deviation, it adjusts the amount of current flowing from the third terminal to the second terminal to a value that can be allowed within the power supply voltage / current specification range, lowers the voltage of the third terminal, and maintains the voltage of the first terminal at the reference voltage. And the current flowing from the third terminal to the second terminal is the drawn-in current (current absorption).

[0095] On the other hand, when the voltage of the first terminal is lower than the reference voltage, it operates in the following manner: it adjusts the drawn-in current to raise the voltage of the third terminal to a value that can be allowed within the power supply voltage / current specification range and maintains the voltage of the first terminal at the reference voltage.

[0096] And when the voltage of the first terminal is equal to the reference voltage, it maintains the amount of the drawn-in current, and the voltage of the first terminal and the reference voltage also remain equal.

[0097] Thus, the voltage Vpin1 of the first terminal is adjusted to be equal to the reference power supply V through the above feedback loop. ref And the voltage for the sensor is applied to the condenser microphone unit ECM.

[0098] In addition, when the signal current of the condenser microphone unit ECM as a sensor is set to I s , it can be approximated that all of the I s ejected from the first terminal pin1 flows through the resistor R b , and when the voltage Vpin1 of the first terminal can be approximated to be equal to the reference power supply V through the above feedback circuit ref , the output voltage is the voltage represented by V ref + I s × R b .

[0099] As described above, according to the structure of this embodiment, through the sufficient operation of the feedback circuit, the output impedance of the third terminal can be reduced, and the anti-external noise performance is remarkable.

[0100] Furthermore, since the output section of the conversion circuit is a current-sinking structure rather than a current-sourcing structure, in this embodiment, the power supply section and the output section of the conversion circuit can share the same terminal, and it is beneficial to operate at a level where a weak voltage for the sensor is applied.

[0101] The above features are also common to the conversion circuits (3A, 3B, 3C, 3D, 3E, 3F) described later.

[0102] Since the output of the conversion circuit 3 does not include ΔVcc in its output items, the conversion circuit 3 of this embodiment has a circuit structure with significantly excellent anti-extraneous noise performance.

[0103] Thus, according to this embodiment, it is possible to reduce the power supply noise superimposed on the microphone output. And, according to this embodiment, since noise can be reduced, even a signal weaker than that of the prior art will not be submerged in the noise, thereby enabling recording and playback of a weaker signal.

[0104] (Second Embodiment)

[0105] Figure 3 FIG. is a diagram showing an example of an electronic circuit of the second embodiment. As Figure 3 shown, the electronic circuit 1A includes a sensor 2 and a conversion circuit 3A.

[0106] The sensor 2 is, for example, a condenser microphone unit ECM. For example, the sensor 2 includes: a condenser microphone C m , a resistor R a , and a field effect transistor Tr1.

[0107] The conversion circuit 3A includes, for example: a capacitor C f , a resistor R b (first resistor), and a variable shunt regulator 32. In addition, the conversion circuit 3A may further include a resistor R L (power supply resistor) and a capacitor C O .

[0108] In the conversion circuit 3A, the voltage regulator 101A is a variable shunt regulator 32. In addition, the conversion circuit 3A may not include a capacitor C f for anti-oscillation.

[0109] Next, the connection structure of the conversion circuit 3A will be described.

[0110] One end of the capacitor C f is connected to one end of the resistor R b , one end of the resistor R L , one end of the capacitor C O , and the cathode of the variable shunt regulator 32, and the other end is connected to the resistor R bThe other end, the reference terminal of the variable shunt regulator 32, and the output of the sensor 2 (the drain of the field effect transistor Tr1).

[0111] The anode of the variable shunt regulator 32 is grounded.

[0112] Resistor R L The other end is connected to the power supply voltage Vcc.

[0113] Capacitor C O The other end is connected to the output terminal Vout.

[0114] Next, a first terminal, a second terminal, and a third terminal are defined in the conversion circuit 3A.

[0115] In the conversion circuit 3A, the output terminal of the sensor 2 (the drain of the field effect transistor Tr1), the other end of the resistor R b the other end of the capacitor C f The intersection of the other end of the capacitor C, the reference terminal of the variable shunt regulator 32 is defined as the first terminal pin1. Thus, the first terminal pin1 is the input section of the conversion circuit 3A. And the voltage of the first terminal pin1 is set as Vpin1.

[0116] The anode of the variable shunt regulator 32 is used as the second terminal pin2. In addition, the second terminal pin2 is grounded.

[0117] One end of the resistor R b one end of the capacitor C f one end of the capacitor C, the anode of the variable shunt regulator 32, one end of the resistor R L one end of the capacitor C O The intersection of one end of the capacitor C is defined as the third terminal pin3. Thus, the third terminal pin3 is the power supply section and output section of the conversion circuit 3A.

[0118] And in the conversion circuit 3A, the gain (R b Is / Is) is determined by the resistor R b The regulator 101A (variable shunt regulator 32) controls the output voltage. In addition, the regulator 101A controls the output voltage by drawing in current.

[0119] In addition, in this structure, the reference voltage V ref is the voltage between the reference terminal of the variable shunt regulator 32 and the second terminal pin2.

[0120] That is to say, the voltage regulator 101A (variable shunt regulator 32) is controlled in the following manner: the deviation between the voltage of the first terminal and a preset reference voltage is detected. When the voltage of the first terminal is higher than the reference voltage, according to the magnitude of the deviation, the amount of current flowing from the third terminal to the second terminal is adjusted to a value that can be permitted within the power supply voltage / current specification range, the voltage of the third terminal is lowered, and the voltage of the first terminal is maintained at the reference voltage. Moreover, the current flowing from the third terminal to the second terminal is a sucking current (current absorption). In addition, when the voltage of the first terminal is lower than the reference voltage and when it is equal to the reference voltage, the same operations as in the first embodiment are performed.

[0121] In Figure 3 the structure of, the equivalent circuit of the variable shunt regulator 32 can be represented by the operational amplifier 31 and the reference power supply V ref and the transistor Tr2 of the first embodiment. That is, according to this embodiment, by using the variable shunt regulator 32 to implement the conversion circuit 3 of the first embodiment, the reference power supply V ref is not required, nor is the power supply to the operational amplifier 31 required, and the circuit structure can be further simplified. That is, in the structure of the second embodiment, the equivalent circuit of the variable shunt regulator 32 can be represented by Figure 2 the equivalent circuit of the structure of.

[0122] Therefore, according to this embodiment, the power supply noise superimposed on the microphone output can be reduced. And according to this embodiment, since the noise can be reduced, compared with the prior art, even weaker signals will not be submerged in the noise, thus realizing the recording and playback of even weaker signals.

[0123] Figure 4 FIG. is a diagram showing a modified example of the second embodiment.

[0124] Figure 4 FIG. is a structural example in which a resistor R L and a capacitor C O are provided on the device side. The device is a device that inputs the outputs of the sensor 2 and the conversion circuit 3A, such as a recording device, an IC recorder, etc. Thus, a structure in which power is supplied to the microphone on the device side is, for example, referred to as a "plug-in power supply method". The conversion circuit 3A can also operate under weak voltage application conditions such as those of a sensor (microphone) that is susceptible to external noise, etc. Different from the prior art, it can be arranged near the sensor where it is sometimes difficult to ensure a stable power supply. In addition, for the above-mentioned conversion circuit 3 and the conversion circuits 3B, 3C, 3D described later, a structure such as Figure 4 shown can be adopted, that is, a structure in which power is supplied to the microphone on the device side.

[0125] When the device is, for example, an IC recorder or the like, since there is also a digital circuit inside the device, the power supply may be mixed with interference such as digital noise. As Figure 15 shown, in the prior art, when the sensor 2 is directly connected to the device, the influence of such power supply noise is significant.

[0126] In Figure 3 and Figure 4 's circuit structure, the output impedance can be made much lower than that of the condenser microphone unit ECM. For example, for the measured value of the output impedance in the DC component, the condenser microphone unit ECM is 2.6 kΩ, and in contrast, it is 0.42 Ω when the conversion circuit 3A is adopted. In addition, for the measured value of the output impedance in the AC component of 1 kHz, the condenser microphone unit ECM is 1.9 kΩ, and in contrast, it is 0.37 Ω when the conversion circuit 3A is adopted. Thus, by adopting the circuit structure of the present embodiment, the output impedance can be reduced, thereby forming a structure with significantly excellent performance against external noises including power supply noise and transmission line noise. In addition, the above-mentioned measured values are only examples and are not limited thereto.

[0127] Figure 5 FIG. is a diagram showing an example of a signal waveform when an audio signal is collected using a microphone unit. In addition, when confirming, the audio signal when making an "ah ~~" sound toward the condenser microphone is collected. The waveform of reference numeral g21 is the output signal waveform in the following case: the condenser microphone unit ECM is connected to the resistor R L and the capacitor C O , and a noise of 100 mV is superimposed on the power supply voltage (Vcc) supplied via the resistor R L . The waveform of reference numeral g22 is the output signal waveform in the following case: the condenser microphone unit ECM is connected to the conversion circuit 3A, and is connected to the resistor R p－p and the capacitor C L , and a noise of 100 mV is superimposed on the power supply supplied via the resistor R O . In L , the horizontal axis represents time (seconds), and the vertical axis represents the output voltage (V). In addition, the measurement conditions are that Vcc is 2.7 V and R p－p = 2.2 kΩ. Figure 5 In L

[0128] Figure 5 As shown, after adopting the conversion circuit 3A of the present embodiment, even when power supply noise is superimposed, the influence on the output signal can be reduced.

[0129] Figure 5 Next, an example of the result of measuring the power supply voltage fluctuation suppression ratio will be described, which quantitatively evaluates the power supply noise elimination effect qualitatively shown in Figure 5 .

[0130] Figure 6 A graph showing an example of the result of measuring the power supply voltage variation suppression ratio. The horizontal axis represents the frequency (Hz), and the vertical axis represents the power supply voltage variation suppression ratio PSRR (Power Supply Rejection Ratio) (dB). Line g31 represents the PSRR of the condenser microphone unit ECM without the conversion circuit 3A. When the conversion circuit 3A is not provided, the PSRR is only about 1.3 dB. As described, the power supply noise ΔVcc mixed into the power supply voltage Vcc is hardly attenuated and is directly superimposed on the output signal ΔVout. In contrast, line g32 is the PSRR when the conversion circuit 3A is adopted. When the conversion circuit 3A is provided, the PSRR is 67 dB, and it can be seen that the power supply noise ΔVcc can be significantly eliminated compared with the case where the conversion circuit 3A is not provided. In addition, Figure 1 the measured values shown are only examples and are not limited thereto. Figure 6 As can be seen from this, by adopting the conversion circuit 3A of the present embodiment, the PSRR can be improved by more than 65 dB, that is, the amplitude of the power supply noise can be reduced to about 1 / 1000.

[0131]

[0132] Next, the relationship between the power supply voltage Vcc and the output voltage output from the output terminal Vout in the electronic circuit will be described.

[0133] Figure 7 An example of the result of measuring the relationship between the power supply voltage Vcc and the output voltage output from the output terminal Vout in the electronic circuit. The horizontal axis is the power supply voltage Vcc (V), and the vertical axis is the output voltage (V) output from the output terminal Vout. Line g41 is the measurement result of the condenser microphone unit ECM without the conversion circuit 3A, and line g42 is the measurement result when the conversion circuit 3A is provided. In addition, the measurement conditions are that R b is 2.2 kΩ, and C f is 1.2 nF. In addition, the specification characteristics of the condenser microphone used in the measurement are as follows: the sensitivity at 1 kHz is -42.0 ± 2.0 dB, the recommended power supply voltage is 1.5 V, the recommended value of the load resistance R L is 1.0 kΩ, the power supply voltage range is 1.0 to 10.0 V, and the frequency characteristic is 50 to 16,000 Hz. And, the specification characteristics of the variable shunt regulator adopted by the conversion circuit 3A are as follows: the voltage value supplied to the reference terminal is 1.24 V, the output impedance is standard 0.25 Ω, and the output voltage is from the voltage value supplied to the reference terminal to 18 V. That is, in the present embodiment, the output impedance of the conversion circuit 3A is 1 Ω or less.

[0134] Figure 7 As Figure 7As shown, when the conversion circuit 3A is not adopted, the curves in each interval all have slopes, and the output voltage output from the output terminal Vout will vary with the power supply voltage Vcc. Therefore, the variation of the power supply voltage Vcc becomes noise.

[0135] In contrast, according to the structure of the present embodiment, when the conversion circuit 3A is provided, under the condition that the power supply voltage Vcc is 2.1V or higher, the output voltage output from the output terminal Vout remains constant regardless of the power supply voltage Vcc and will not become noise even if the power supply voltage Vcc varies. And, according to the structure of the present embodiment, since the output impedance can be reduced, a structure with significantly improved anti-external noise performance is formed. Also, according to the present embodiment, since noise can be reduced, compared with the prior art, even weaker signals will not be submerged in noise, thus enabling the recording and playback of even weaker signals.

[0136] (Third Embodiment)

[0137] Next, an example of using transistors with a Darlington connection structure in the conversion circuit will be described.

[0138] Figure 8 FIG. is a diagram showing a structural example of the electronic circuit of the third embodiment. As Figure 8 shown, the electronic circuit 1B includes a sensor 2 and a conversion circuit 3B.

[0139] The sensor 2 is, for example, a condenser microphone unit ECM. The condenser microphone unit ECM, for example, includes: a condenser microphone C m , a resistor R a , and a field effect transistor Tr1.

[0140] The conversion circuit 3B, for example, includes: a capacitor C f , a resistor R b (first resistor), a transistor Tr3 (first transistor), a transistor Tr4 (second transistor), a resistor R c (second resistor). In addition, the conversion circuit 3B may further include a resistor R L (power supply resistor) and a capacitor C O . In addition, the conversion circuit 3B may not include the anti-oscillation capacitor C f . And, the transistors Tr3 and Tr4 are NPN-type transistors.

[0141] The voltage regulator 101B, for example, includes: Tr3 (first transistor), a transistor Tr4 (second transistor), a resistor Rc (third resistor).

[0142] Next, the connection structure of the conversion circuit 3B will be described.

[0143] Capacitor C f, one end of which is connected to resistor R b One end of L One end of capacitor C O One end of, the collector of transistor Tr3, and the collector of transistor Tr4, and the other end is connected to resistor R b The other end of, the base of transistor Tr3, and the output of sensor 2.

[0144] The emitter of transistor Tr3 is connected to one end of resistor R c And the base of transistor Tr4. Moreover, transistors Tr3 and Tr4 are connected in Darlington configuration.

[0145] Resistor R c The other end is grounded.

[0146] The emitter of transistor Tr4 is grounded.

[0147] Resistor R L The other end is connected to the power supply voltage Vcc.

[0148] Capacitor C O The other end is connected to the output terminal Vout.

[0149] Next, in conversion circuit 3B, a first terminal, a second terminal, and a third terminal are defined.

[0150] In conversion circuit 3B, the output terminal of sensor 2 (the drain of field effect transistor Tr1), the other end of resistor R b The other end of, the other end of capacitor C f The other end of, and the intersection with the base of transistor Tr3 are defined as the first terminal pin1. Thus, the first terminal pin1 is the input section of conversion circuit 3B. And the voltage of the first terminal pin1 is set as Vpin1.

[0151] The intersection of the emitter of transistor Tr4 and the other end of resistor R c is defined as the second terminal pin2. In addition, the second terminal pin2 is grounded.

[0152] Resistor R b One end of, one end of capacitor C f One end of, the collector of transistor Tr3, the collector of transistor Tr4, one end of resistor R L One end of, one end of capacitor C O One end of are defined as the third terminal pin3. Thus, the third terminal pin3 is the power supply section and the output section of conversion circuit 3B.

[0153] Moreover, in conversion circuit 3B, the gain (R b Is / Is) is determined by resistor Rb Determination. The voltage regulator 101B controls the output voltage. In addition, the voltage regulator 101B controls the output voltage by drawing in current.

[0154] In addition, in this structure, the reference voltage V ref is the voltage between the base of the transistor Tr3 and the second terminal pin2.

[0155] In the present embodiment, the voltage regulator 101B is controlled as follows: the deviation between the voltage of the first terminal and a preset reference voltage is detected. When the voltage of the first terminal is higher than the reference voltage, according to the magnitude of the deviation, the amount of current flowing from the third terminal to the second terminal is adjusted to a value that can be allowed within the specification range of the power supply voltage / current, the voltage of the third terminal is lowered, and the voltage of the first terminal is maintained at the reference voltage. And the current flowing from the third terminal to the second terminal is the drawn-in current (current absorption). In addition, when the voltage of the first terminal is lower than the reference voltage and when it is equal to the reference voltage, the same operations as in the first embodiment are performed.

[0156] Figure 9 FIG. is a diagram showing the relationship between the power supply voltage Vcc and the output voltage output from the output terminal Vout in the third embodiment. The horizontal axis is the power supply voltage Vcc (V), and the vertical axis is the output voltage Vout (V) output from the output terminal Vout. Figure 9 The measurement conditions are as follows. Regarding the sensor 2 as a current source g m and the resistor R mo in the equivalent circuit (see Figure 1 ), the resistor R mo is 100 kΩ, the resistor R b is 2.2 kΩ, and the resistor R L is 2.2 kΩ. And the resistor R c is 10 kΩ (line g51), 100 kΩ (line g52), 1 MΩ (line g53), 10 MΩ (line g54). This indicates that the reference voltage can be adjusted by the value of the resistor R c . In addition, the current output value of the current source gm is 0.16 mA.

[0157] According to the structure of the third embodiment, the relationship between the power supply voltage Vcc and the output voltage output from the output terminal Vout is as Figure 9 shown. When the power supply voltage Vcc is about 2 V or more, even if the power supply voltage Vcc changes, the output voltage output from the output terminal Vout remains substantially constant. Therefore, the influence of noise mixed in the power supply voltage Vcc can be reduced. And according to the present embodiment, since noise can be reduced, signals that are weaker than those in the prior art will not be drowned out by noise, thus enabling recording and playback of weaker signals.

[0158] (Fourth Embodiment)

[0159] Next, a second example of a transistor using a Darlington connection structure in the conversion circuit will be described.

[0160] Figure 10 FIG. for showing a structural example of the electronic circuit of the fourth embodiment. As Figure 10 shown, the electronic circuit 1C includes a sensor 2 and a conversion circuit 3C.

[0161] The sensor 2 is, for example, a condenser microphone unit ECM. The condenser microphone unit ECM, for example, includes: a condenser microphone C m , a resistor R a , and a field effect transistor Tr1.

[0162] The conversion circuit 3C, for example, includes: a capacitor C f , a resistor R b (first resistor), a transistor Tr5 (first transistor), a transistor Tr6 (second transistor), a transistor Tr7 (third transistor), a transistor Tr8 (fourth transistor), a resistor R d (second resistor), a resistor R e (third resistor), a resistor R f (fourth resistor). In addition, the conversion circuit 3C may further include a resistor R L (power supply resistor) and a capacitor C O . In addition, the conversion circuit 3C may not include the anti-oscillation capacitor C f . And, the transistors Tr5, Tr6, and Tr8 are NPN-type transistors. The transistor Tr7 is a PNP-type transistor.

[0163] The voltage regulator 101C, for example, includes: a transistor Tr5 (first transistor), a transistor Tr6 (second transistor), a transistor Tr7 (third transistor), a transistor Tr8 (fourth transistor), a resistor R d (second resistor), a resistor R e (third resistor), a resistor R f (fourth resistor).

[0164] Next, the connection structure of the conversion circuit 3C will be described.

[0165] The capacitor C f , one end of which is connected to one end of the resistor R b , one end of the resistor R L , one end of the capacitor C O , the collector of the transistor Tr5, one end of the resistor Re, the emitter of the transistor Tr7, and the collector of the transistor Tr8, and the other end is connected to the resistor R bThe other end, the base of transistor Tr5, and the output of sensor 2.

[0166] The emitter of transistor Tr5 is connected to one end of resistor R d and the base of transistor Tr6. Moreover, transistors Tr5 and Tr6 are connected in Darlington configuration.

[0167] Resistor R d The other end is grounded.

[0168] The collector of transistor Tr6 is connected to the other end of resistor R e and the base of transistor Tr7, and the emitter is grounded.

[0169] The collector of transistor Tr7 is connected to one end of resistor R f and the base of transistor Tr8. Moreover, transistors Tr7 and Tr8 are connected in inverse Darlington configuration.

[0170] Resistor R f The other end is grounded.

[0171] The emitter of transistor Tr8 is grounded.

[0172] Resistor R L The other end is connected to the power supply voltage Vcc.

[0173] Capacitor C O The other end is connected to the output terminal Vout.

[0174] Next, in the conversion circuit 3C, a first terminal, a second terminal, and a third terminal are defined.

[0175] In the conversion circuit 3C, the output terminal of sensor 2 (the drain of field effect transistor Tr1) is connected to the other end of resistor R b and the other end of capacitor C f and the intersection of the other end and the base of transistor Tr5 is defined as the first terminal pin1. Thus, the first terminal pin1 is the input section of the conversion circuit 3C. And the voltage of the first terminal pin1 is set as Vpin1.

[0176] The emitter of transistor Tr8, the other end of resistor R f the emitter of transistor Tr6, the other end of resistor R d The intersection of the other end is defined as the second terminal pin2. In addition, the second terminal pin2 is grounded.

[0177] Resistor R b One end, the one end of capacitor C f the collector of transistor Tr5, the other end of resistor R eOne end, the emitter of transistor Tr7, the collector of transistor Tr8, and capacitor R L One end, and capacitor C O The intersection of one end and the power supply section and output section of the conversion circuit 3C is defined as the third terminal pin3.

[0178] Moreover, in the conversion circuit 3C, the gain (R b Is / Is) is determined by resistor R b The voltage regulator 101C controls the output voltage. In addition, the voltage regulator 101C controls the output voltage by drawing in current.

[0179] In addition, in this structure, the reference voltage V ref Is the voltage between the base of transistor Tr5 and the second terminal pin2.

[0180] That is to say, the voltage regulator 101C controls in the following way: detecting the deviation between the voltage of the first terminal and the preset reference voltage, when the voltage of the first terminal is higher than the reference voltage, according to the magnitude of the deviation, adjusting the current flowing from the third terminal to the second terminal to a value that can be allowed within the power supply voltage / current specification range, lowering the voltage of the third terminal, and maintaining the voltage of the first terminal as the reference voltage. And the current flowing from the third terminal to the second terminal is the drawn-in current (current absorption).

[0181] In addition, when the voltage of the first terminal is lower than the reference voltage and when it is equal to the reference voltage, the same operations as in the first embodiment are performed.

[0182] Figure 11 It is a diagram showing the relationship between the power supply voltage Vcc and the output voltage output from the output terminal Vout in the fourth embodiment. The horizontal axis is the power supply voltage Vcc (V), and the vertical axis is the output voltage (V) output from the output terminal Vout. Figure 11 The measurement conditions of m Are as follows: regarding the sensor 2 as a current source g mo And the equivalent circuit of resistor R Figure 1 ) When, resistor R mo Is 100 kΩ, resistor R b Is 2.2 kΩ, resistor R e Is 10 kΩ, resistor R f Is 5 kΩ, resistor R L Is 2.2 kΩ. And resistor R d Is 10 kΩ (line g61), 100 kΩ (line g62), 1 MΩ (line g63), 10 MΩ (line g64). This indicates that it is possible to pass through resistor R dAdjust the reference voltage of the value. In addition, the current output value of the current source gm is 0.16 mA.

[0183] According to the structure of the fourth embodiment, the relationship between the power supply voltage Vcc and the output voltage output from the output terminal Vout is as Figure 11 shown. When the power supply voltage Vcc is 2 V or more, even if the power supply voltage Vcc changes, the output voltage output from the output terminal Vout remains constant. Therefore, the influence of noise mixed into the power supply voltage Vcc can be reduced. And according to this embodiment, since noise can be reduced, even a weaker signal compared with the prior art will not be submerged in the noise, thereby realizing the recording and playback of a weaker signal. In particular, Figure 11 the flat part in Figure 9 is much less inclined compared with that of the third embodiment. From this, it can be known that the fourth embodiment is particularly excellent in terms of output impedance and external noise resistance performance compared with the third embodiment.

[0184] (Fifth Embodiment)

[0185] Next, a third example of a transistor using a Darlington connection structure in the conversion circuit will be described.

[0186] Figure 12 FIG. is a diagram showing a structural example of the electronic circuit of the fifth embodiment. As Figure 12 shown, the electronic circuit 1D includes a sensor 2 and a conversion circuit 3D.

[0187] The sensor 2 is, for example, a condenser microphone unit ECM. The condenser microphone unit ECM, for example, includes: a condenser microphone C m , a resistor R a , and a field effect transistor Tr1.

[0188] The conversion circuit 3D includes, for example: a capacitor C f , a resistor R b (first resistor), a transistor Tr9 (first transistor), a transistor Tr10 (second transistor), a transistor Tr11 (third transistor), a resistor R g (second resistor), a resistor R h (third resistor). In addition, the conversion circuit 3D may further include a resistor R L (power supply resistor) and a capacitor C O . In addition, the conversion circuit 3D may not include the anti-oscillation capacitor C f . And the transistor Tr9 and the transistor Tr10 are NPN-type transistors. The transistor Tr11 is a PNP-type transistor.

[0189] The voltage regulator 101D includes, for example: a transistor Tr9 (first transistor), a transistor Tr10 (second transistor), a transistor Tr11 (third transistor), a resistor R g (second resistor), a resistor R h (third resistor).

[0190] Next, the connection structure of the conversion circuit 3D will be described.

[0191] A capacitor C f , one end of which is connected to one end of the resistor R b , one end of the resistor R L , one end of the capacitor C O , one end of the transistor Tr9's collector, one end of the resistor R h and the emitter of the transistor Tr11, and the other end is connected to the other end of the resistor R b , the base of the transistor Tr9 and the output of the sensor 2 (the drain of the field-effect transistor Tr1).

[0192] The emitter of the transistor Tr9 is connected to one end of the resistor R g and the base of the transistor Tr10. Also, the transistors Tr9 and Tr10 are connected in a Darlington configuration.

[0193] The resistor R g 's other end is grounded.

[0194] The collector of the transistor Tr10 is connected to the other end of the resistor R h and the base of the transistor Tr11, and the emitter is grounded.

[0195] The collector of the transistor Tr11 is grounded.

[0196] The resistor R L 's other end is connected to the power supply voltage Vcc.

[0197] The capacitor C O 's other end is connected to the output terminal Vout.

[0198] Next, in the conversion circuit 3D, a first terminal, a second terminal, and a third terminal are defined.

[0199] In the conversion circuit 3D, the intersection of the output terminal of the sensor 2 (the drain of the field-effect transistor Tr1), the other end of the resistor R b , the other end of the capacitor C f , and the base of the transistor Tr9 is defined as the first terminal pin1. Thus, the first terminal pin1 is the input part of the conversion circuit 3D. And the voltage of the first terminal pin1 is set as Vpin1.

[0200] The intersection of the collector of transistor Tr11, the emitter of transistor Tr10, and the other end of resistor R g is defined as the second terminal pin2. In addition, the second terminal pin2 is grounded. One end of resistor R b , one end of capacitor C f , the collector of transistor Tr9, one end of resistor R h , the emitter of transistor Tr11, one end of capacitor R L , one end of capacitor C O The intersection of one ends is defined as the third terminal pin3. Thus, the third terminal pin3 is the power supply part of the conversion circuit 3D and is also the output part.

[0201] Moreover, in the conversion circuit 3D, the gain (R b Is / Is) is determined by resistor R b . The voltage regulator 101D controls the output voltage. In addition, the voltage regulator 101D controls the output voltage by drawing in current.

[0202] In addition, in this structure, the reference voltage V ref is the voltage between the base of transistor Tr9 and the second terminal pin2.

[0203] The voltage regulator 101D is controlled as follows: It detects the deviation between the voltage of the first terminal and a preset reference voltage. When the voltage of the first terminal is higher than the reference voltage, according to the magnitude of the deviation, it adjusts the amount of current flowing from the third terminal to the second terminal within the allowable range of the power supply voltage / current, reduces the voltage of the third terminal, and maintains the voltage of the first terminal at the reference voltage. And the current flowing from the third terminal to the second terminal is a drawn-in current (current absorption).

[0204] In addition, when the voltage of the first terminal is lower than the reference voltage and when it is equal to the reference voltage, the same operations as in the first embodiment are performed.

[0205] Figure 13 Fig. is a diagram showing the relationship between the power supply voltage Vcc and the output voltage output from the output terminal Vout in the fifth embodiment. The horizontal axis is the power supply voltage Vcc (V), and the vertical axis is the output voltage Vout (V) output from the output terminal Vout. Figure 13 The measurement conditions are as follows: Regarding the sensor 2 as a current source g m and the equivalent circuit of resistor R mo (see Figure 1 ), when resistor R mo is 100 kΩ, resistor R b is 2.2 kΩ, resistor R h is 10 kΩ, resistor R Lis 2.2 kΩ. And, the resistor R g is 10 kΩ (line g71), 100 kΩ (line g72), 1 MΩ (line g73), 10 MΩ (line g74). This means that the reference voltage can be adjusted by the value of the resistor R g . In addition, the current output value of the current source gm is 0.16 mA.

[0206] According to the structure of the fifth embodiment, the relationship between the power supply voltage Vcc and the output voltage output from the output terminal Vout is as Figure 13 shown. When the power supply voltage Vcc is 2 V or more, even if the power supply voltage Vcc changes, the output voltage output from the output terminal Vout remains constant. Therefore, the influence of the noise mixed into the power supply voltage Vcc can be reduced. And, according to this embodiment, since the noise can be reduced, even a weaker signal than the prior art will not be drowned out by the noise, so that the recording and playback of a weaker signal can be realized, and a balance between mountability and external noise resistance performance can be achieved.

[0207] (Example of a sensor)

[0208] In addition, in each of the above embodiments, an example in which the sensor 2 is a condenser microphone unit has been described, but it is not limited thereto. The sensor 2 can be, for example, a condenser microphone element, or can also be a sensor with a high output impedance, such as a pressure sensor, a piezoelectric sensor, a quartz crystal resonator, an acceleration sensor, an optical sensor, etc.

[0209] Figure 14 is a diagram showing a structural example of an electronic circuit when the sensor is a quartz crystal resonator.

[0210] Since the impedance of a quartz crystal resonator is usually high, for example, several tens of kΩ, etc., noise may be mixed in when connected to other circuits. Therefore, as Figure 14 the sensor 2E in shows, a structure is known in which the impedance is reduced by combining the quartz crystal resonator X with the field effect transistor Tr21. In the Figure 14 structure of the sensor 2E shown, the impedance can be reduced from about 10 14 Ω to about 100 Ω. And, in the electronic circuit 1E in which the aforementioned conversion circuit 3A is connected to such a sensor 2E, since the output impedance can be further reduced, the influence of the noise can be further reduced. In addition, the conversion circuit can be the aforementioned conversion circuits 3, 3B, 3C, and 3D.

[0211] In addition, since a quartz crystal has a piezoelectric effect, for example, in a piezoelectric acceleration sensor, a structure in which a capacitor and a resistor are connected in parallel to a quartz crystal resonator X between the quartz crystal resonator X and a field effect transistor Tr21 is known (for example, refer to Reference 1). Also, by connecting the aforementioned conversion circuit 3 or the like to such a sensor, since the output impedance can be further reduced, the influence of noise can be further reduced. And, according to this embodiment, since noise can be reduced, even a weaker signal compared with the prior art will not be drowned out by noise, and thus the signal can be detected.

[0212] Reference 1; Conversion types of accelerometers (piezoelectric type (PE), piezoresistive type (PR), capacitive type (VC) sensors), Toyo Technology Co., Ltd., February 16, 2022, Internet search: October 26, 2022

[0213] <URL; https: / / www.toyo.co.jp / mecha / casestudy / detail / id=34295>

[0214] (Sixth Embodiment)

[0215] Next, an example in which a field effect transistor (FET) is used in the conversion circuit will be described.

[0216] Figure 16 FIG. is a diagram showing a structural example of an electronic circuit of the sixth embodiment. As Figure 16 shown, the electronic circuit 1F includes a sensor 2 and a conversion circuit 3E.

[0217] The sensor 2 is, for example, a condenser microphone unit ECM. The condenser microphone unit ECM, for example, includes: a condenser microphone C m , a resistor R a , and a field effect transistor Tr1.

[0218] The conversion circuit 3E, for example, includes: a capacitor C f , a resistor R b (first resistor), a field effect transistor FET1 (first field effect transistor), a field effect transistor FET2 (second field effect transistor), a resistor R i (second resistor). In addition, the conversion circuit 3E may further include a resistor R L (power supply resistor) and a capacitor C O . In addition, the conversion circuit 3E may not include the anti-oscillation capacitor C f . And, the field effect transistor FET1 and the field effect transistor FET2 are, for example, any type of FET such as a MOSFET, MESFET, SiC FET, GaN FET, GaAs FET.

[0219] The voltage regulator 101E includes, for example: a field effect transistor FET1 (first field effect transistor), a field effect transistor FET2 (second field effect transistor), and a resistor R i (second resistor).

[0220] Next, the connection structure of the conversion circuit 3E will be described.

[0221] A capacitor C f , one end of which is connected to one end of the resistor R b one end of the resistor R L one end of the capacitor C O one end of the capacitor C, the drain terminal t2 of the field effect transistor FET1, and the drain terminal t5 of the field effect transistor FET2, and the other end is connected to the other end of the resistor R b the other end of the resistor R, the gate terminal t1 of the field effect transistor FET1, and the output of the sensor 2.

[0222] The source terminal t3 of the field effect transistor FET1 is connected to one end of the resistor R i one end of the resistor R and the gate terminal t4 of the field effect transistor FET2.

[0223] The resistor R i the other end of which is grounded.

[0224] The source terminal t6 of the field effect transistor FET2 is grounded.

[0225] The resistor R L the other end of which is connected to the power supply voltage Vcc.

[0226] The capacitor C O the other end of which is connected to the output terminal Vout.

[0227] Next, a first terminal, a second terminal, and a third terminal are defined in the conversion circuit 3E.

[0228] In the conversion circuit 3E, the output terminal of the sensor 2 (the drain of the field effect transistor Tr1), the other end of the resistor R b the other end of the resistor R, the other end of the capacitor C f the other end of the capacitor C, and the intersection of the gate terminal t1 of the field effect transistor FET1 are defined as the first terminal pin1. Thus, the first terminal pin1 is the input part of the conversion circuit 3E. And the voltage of the first terminal pin1 is set as Vpin1.

[0229] The intersection of the source terminal t6 of the field effect transistor FET2 and the other end of the resistor R i is defined as the second terminal pin2. In addition, the second terminal pin2 is grounded.

[0230] The resistor Rb One end of, and capacitor C f One end of, the drain terminal t2 of field effect transistor FET1, the drain terminal t5 of field effect transistor FET2, and resistor R L One end of, and capacitor C O The intersection of one end of is defined as the third terminal pin3. Thus, the third terminal pin3 is the power supply part of the conversion circuit 3E and also the output part.

[0231] Moreover, in the conversion circuit 3E, the gain (R b Is / Is) is determined by resistor R b The voltage regulator 101E controls the output voltage. In addition, the voltage regulator 101E controls the output voltage by drawing in current.

[0232] In addition, in this structure, the reference voltage V ref Is the voltage between the gate terminal t1 of field effect transistor FET1 and the second terminal pin2.

[0233] In this embodiment, the voltage regulator 101E is controlled as follows: the deviation between the voltage of the first terminal and a preset reference voltage is detected. When the voltage of the first terminal is higher than the reference voltage, according to the magnitude of the deviation, the current flowing from the third terminal to the second terminal is adjusted to a value that can be allowed within the power supply voltage / current specification range, the voltage of the third terminal is lowered, and the voltage of the first terminal is maintained at the reference voltage. And the current flowing from the third terminal to the second terminal is a drawn-in current (current absorption).

[0234] In addition, when the voltage of the first terminal is lower than the reference voltage and when it is equal to the reference voltage, the same operations as in the first embodiment are performed.

[0235] (Seventh Embodiment)

[0236] Figure 17 FIG. shows an example of an electronic circuit of the seventh embodiment. As Figure 17 shown, the electronic circuit 1G includes a sensor 2 and a conversion circuit 3F.

[0237] The sensor 2 is, for example, a condenser microphone unit ECM. The condenser microphone unit ECM, for example, includes: a condenser microphone C m Resistor R a Field effect transistor Tr1.

[0238] The conversion circuit 3F, for example, includes: capacitor C f Resistor R b (First resistor), reference power supply V ref, an operational amplifier 31A, and a diode D. Additionally, the conversion circuit 3F may include a resistor in place of the diode D. Furthermore, the conversion circuit 3F may also include a resistor R L (power supply resistor) and a capacitor C O .

[0239] The voltage regulator 101F includes, for example: an operational amplifier 31A, a diode D, and a reference power supply V ref .

[0240] Next, the connection structure of the conversion circuit 3F will be described.

[0241] The capacitor C f , one end of which is connected to one end of the resistor R b , one end of the resistor R L , one end of the capacitor C O , and the other end is connected to the other end of the resistor R b , the non-inverting input terminal (+) of the operational amplifier 31A, and the output of the sensor 2.

[0242] In the operational amplifier 31A, its inverting input terminal (-) is connected to the positive electrode of the reference power supply V ref , and its output terminal is connected to the anode of the diode D. Additionally, the positive power supply terminal +V of the operational amplifier 31A is connected to one end of the resistor R L , its negative power supply terminal -V is grounded, and the cathode of the diode D is grounded.

[0243] The reference power supply V ref , the negative electrode of which is grounded. Additionally, the reference power supply V ref may be, for example, a Zener diode circuit. In this case, for example, it may be as follows: one end of another first resistor (not shown) is connected to one end of the resistor R L , the other end of the other first resistor is connected to the cathode of another first Zener diode (not shown) and the inverting input terminal of the operational amplifier 31A, and the anode of the other first Zener diode is grounded.

[0244] The other end of the resistor R L is connected to the power supply voltage Vcc.

[0245] The other end of the capacitor C O is connected to the output terminal Vout.

[0246] Next, a first terminal, a second terminal, and a third terminal are defined in the conversion circuit 3F.

[0247] In the conversion circuit 3F, the output terminal of the sensor 2 (the drain of the field effect transistor Tr1), the other end of the resistor R b , and the other end of the capacitor C fThe intersection of the other end and the non-inverting input terminal of the operational amplifier 31A is defined as the first terminal pin1. Thus, the first terminal pin1 is the input section of the conversion circuit 3F. Also, the voltage of the first terminal pin1 is set as Vpin1.

[0248] The intersection of the cathode of the diode D and the negative electrode of the reference power supply V ref is defined as the second terminal pin2. In addition, the second terminal pin2 is grounded. The negative power supply terminal -V of the operational amplifier 31A is connected to the second terminal pin2.

[0249] The intersection of one end of the resistor R b and one end of the capacitor C f and one end of the resistor R L and one end of the capacitor C O is defined as the third terminal pin3. Thus, the third terminal pin3 is the power supply section of the conversion circuit 3F and also the output section. The positive power supply terminal +V of the operational amplifier 31A is connected to the third terminal pin3.

[0250] In the conversion circuit 3F, the gain (R b Is / Is) is determined by the resistor R b . Also, the current Is is the signal current of the condenser microphone unit ECM. In the conversion circuit 3F, the operational amplifier 31A is, for example, an OP amplifier and functions as an error circuit that detects the error between the signal input to the non-inverting input terminal and the voltage of the reference power supply. In the conversion circuit 3F, the signal current of the condenser microphone unit ECM is converted into a voltage. The voltage regulator 101F controls the output voltage. Also, the voltage regulator 101F controls the output voltage by sucking in current.

[0251] That is to say, the voltage regulator 101F controls in the following manner: detecting the deviation between the voltage of the first terminal and a preset reference voltage, when the voltage of the first terminal is higher than the reference voltage, adjusting the amount of current flowing from the third terminal to the second terminal to a value that can be allowed within the power supply voltage / current specification range according to the size of the deviation, lowering the voltage of the third terminal, and maintaining the voltage of the first terminal as the reference voltage. And the current flowing from the third terminal to the second terminal is the sucking-in current (current absorption).

[0252] On the other hand, when the voltage of the first terminal is lower than the reference voltage, it operates in the following manner: adjusting the sucking-in current, raising the voltage of the third terminal to a value that can be allowed within the power supply voltage / current specification range, and maintaining the voltage of the first terminal as the reference voltage.

[0253] Also, when the voltage of the first terminal is equal to the reference voltage, the current amount of the suction current is maintained, and the voltage of the first terminal and the reference voltage are also maintained in an equal state.

[0254] Thus, the voltage Vpin1 of the first terminal is adjusted to be equal to the reference power supply V through the above feedback loop. ref The voltage for the sensor is applied to the condenser microphone unit ECM.

[0255] As described above, the electronic circuit 1 (or 1A, 1B, 1C, 1D, 1F, 1G) of each embodiment is a circuit that converts the current output of the sensor 2 (or 2E) into a voltage output, and it includes a conversion circuit 3 (or 3A, 3B, 3C, 3D, 3E, 3F) that outputs a voltage. The conversion circuit 3 (or 3A, 3B, 3C, 3D, 3E, 3F) includes: a first terminal pin1, a second terminal pin2, and a third terminal pin3. For the electronic circuit 1 (or 1A, 1B, 1C, 1D, 1F, 1G) of each embodiment, the first terminal pin1 is an input part, which includes a power supply circuit part that supplies a stable voltage to one of the circuit, the component, and the sensor, and is connected to one of the circuit, the component, and the sensor 2 (or 2E). And, the second terminal pin2 of the electronic circuit 1 (or 1A, 1B, 1C, 1D, 1F, 1G) of each embodiment is grounded. Further, the third terminal pin3 of the electronic circuit 1 (or 1A, 1B, 1C, 1D, 1F, 1G) of each embodiment is a power supply part of the conversion circuit 3 (or 3A, 3B, 3C, 3D, 3E, 3F) and is an output part. The third terminal pin3 supplies power to the conversion circuit from the power supply voltage Vcc via the resistor R. L Supply power to the conversion circuit.

[0256] Thus, according to the above-described embodiments, even when noise of the power supply voltage Vcc is superimposed, the influence of the noise can be reduced. And, according to the above-described embodiments, since the noise can be reduced, a signal weaker than that of the prior art will not be submerged in the noise, and thus the signal can be detected. The conversion circuit (3 or 3A, 3B, 3C, 3D, 3E, 3F) can be arranged near the sensor where it is sometimes difficult to ensure a stable power supply.

[0257] In addition, although the conversion circuits (3 or 3A, 3B, 3C, 3D, 3E, 3F) shown in the above embodiments are circuits with significantly different appearances, their equivalent circuits when highly simplified are exactly the same. In addition, the features described for one conversion circuit (3 or 3A, 3B, 3C, 3D, 3E, 3F) are only repetitive descriptions omitted, and these features also apply to other conversion circuits (3 or 3A, 3B, 3C, 3D, 3E, 3F).

[0258] As described above, although the embodiments for carrying out the present invention are illustrated by the implementation examples, the present invention is not limited to any of these embodiments, and various modifications and substitutions can be made without departing from the gist of the present invention.

[0259] In addition, the sixth embodiment is equivalent to implementing the functions achieved by the transistors (Tr3, Tr4) included in the conversion circuit (3B) of the third embodiment by field effect transistors (FET1, FET2). Similarly, it is also possible to use field effect transistors to implement the functions achieved by the transistors (Tr2, Tr5, Tr6, Tr7, Tr8, Tr9, Tr10, Tr11) included in the respective conversion circuits (3, 3C, 3D) of the first embodiment, the fourth embodiment, and the fifth embodiment.

Claims

1. A conversion circuit that converts an input current into an output voltage, characterized in that, Comprising: A first terminal, which is the input part of the input current; A second terminal, which is the ground terminal; A third terminal, which is the output part of the output voltage, and supplies the power supply voltage via a power supply resistance; A first resistor, one end of which is connected to the first terminal and the other end is connected to the third terminal; and A voltage regulator, which is controlled in the following manner: detecting the deviation between the voltage of the first terminal and a preset reference voltage, and when the voltage of the first terminal is higher than the reference voltage, adjusting the amount of current flowing from the third terminal to the second terminal according to the magnitude of the deviation, and maintaining the voltage of the first terminal as the reference voltage, Determining the gain of the conversion circuit through the first resistor.

2. The conversion circuit according to claim 1, wherein The current flowing from the third terminal to the second terminal is a sink current, and the sink current is supplied to the third terminal from outside the conversion circuit.

3. The conversion circuit according to claim 1 or 2, wherein The voltage regulator comprises a variable shunt regulator, The reference terminal of the variable shunt regulator is connected to the first terminal, The anode terminal of the variable shunt regulator is connected to the second terminal, The cathode terminal of the variable shunt regulator is connected to the third terminal.

4. The conversion circuit according to claim 1 or 2, wherein The voltage regulator comprises an operational amplifier and a first NPN transistor, The non-inverting input terminal of the operational amplifier is connected to the first terminal, The reference voltage is input to the inverting input terminal of the operational amplifier, The output terminal of the operational amplifier is connected to the base of the first transistor, The collector of the first transistor is connected to the third terminal, The emitter of the first transistor is connected to the second terminal.

5. The conversion circuit according to claim 1 or 2, wherein The voltage regulator comprises a first NPN transistor, a second NPN transistor and a second resistor, The base of the first transistor is connected to the first terminal, The emitter of the first transistor is connected to the second terminal via the second resistor, The emitter of the first transistor is connected to the base of the second transistor, The collector of the first transistor is connected to the collector of the second transistor, The collector of the second transistor is connected to the third terminal, The emitter of the second transistor is connected to the second terminal.

6. The conversion circuit according to claim 1 or 2, wherein The voltage regulator comprises a first NPN transistor, a second NPN transistor, a third PNP transistor, a fourth NPN transistor, a second resistor, a third resistor and a fourth resistor, The base of the first transistor is connected to the first terminal, The emitter of the first transistor is connected to the second terminal via the second resistor, The emitter of the first transistor is connected to the base of the second transistor, The collector of the first transistor is connected to the third terminal, The emitter of the second transistor is connected to the second terminal, The collector of the second transistor is connected to the third terminal via the third resistor. The collector of the second transistor is connected to the base of the third transistor. The emitter of the third transistor is connected to the third terminal. The collector of the third transistor is connected to the base of the fourth transistor. The collector of the third transistor is connected to the second terminal via the fourth resistor. The collector of the fourth transistor is connected to the third terminal. The emitter of the fourth transistor is connected to the second terminal.

7. The conversion circuit according to claim 1 or 2, characterized in that The voltage regulator includes: a first NPN transistor, a second NPN transistor, a third PNP transistor, a second resistor, and a third resistor. The base of the first transistor is connected to the first terminal. The emitter of the first transistor is connected to the second terminal via the second resistor. The emitter of the first transistor is connected to the base of the second transistor. The collector of the first transistor is connected to the third terminal. The emitter of the second transistor is connected to the second terminal. The collector of the second transistor is connected to the third terminal via the third resistor. The collector of the second transistor is connected to the base of the third transistor. The emitter of the third transistor is connected to the third terminal. The collector of the third transistor is connected to the second terminal.

8. The conversion circuit according to claim 1 or 2, characterized in that The output impedance of the conversion circuit is 1 Ω or less.

9. The conversion circuit according to claim 1 or 2, characterized in that It includes at least one of the following: a power supply resistor with one end connected to the third terminal and the other end connected to the power supply voltage; a capacitor with one end connected to the third terminal and the other end serving as an output terminal to the load side; a capacitor with one end connected to the third terminal and the other end connected to the first terminal.

10. The conversion circuit according to claim 1 or 2, characterized in that The voltage regulator includes: a first field effect transistor, a second field effect transistor, and a second resistor. The gate of the first field effect transistor is connected to the first terminal. The source of the first field effect transistor is connected to the second terminal via the second resistor. The source of the first field effect transistor is connected to the gate of the second field effect transistor. The drain of the first field effect transistor is connected to the drain of the second field effect transistor. The drain of the second field effect transistor is connected to the third terminal. The source of the second field effect transistor is connected to the second terminal.

11. The conversion circuit according to claim 1 or 2, characterized in that The voltage regulator includes: an operational amplifier and a diode. The non-inverting input terminal of the operational amplifier is connected to the first terminal. The reference voltage is input to the inverting input terminal of the operational amplifier. The output terminal of the operational amplifier is connected to the anode of the diode. The cathode of the diode is connected to the second terminal.

12. The conversion circuit according to claim 11, characterized in that the positive power supply terminal of the operational amplifier is connected to the third terminal, the negative power supply terminal of the operational amplifier is connected to the second terminal.

13. An electronic circuit, characterized in that, comprising: the conversion circuit according to claim 1 or 2; a sensor connected to the input section.

14. The electronic circuit according to claim 13, characterized in that the sensor is one of a condenser microphone, a piezoelectric sensor, a pressure sensor, an acceleration sensor, an optical sensor, and a quartz crystal resonator.

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