RU2676755C1 - Reference voltage with a reduced noise level generation device - Google Patents

Abstract

FIELD: electrical equipment.SUBSTANCE: invention relates to the field of electrical equipment, in particular to the reference voltage generation devices, and can be used during the stable DC voltage low-noise sources development. Reference voltage with the reduced noises level generation device contains stabilizer, capacitor, scaling voltage repeater, voltage divider, a voltage repeater, subtractor, at that, the scaling voltage repeater contains three resistors and an operational amplifier; repeater voltage divider contains two resistors; repeater voltage repeater contains the operational amplifier; the subtractor contains four resistors and repeater operational amplifier.EFFECT: technical result, which can be achieved with the present invention is in the generated reference voltage noise level reduction and the polarity bringing to the used stabilizer output voltage polarity.1 cl, 6 dwg, 4 tbl

Description

FIELD OF THE INVENTION

The invention relates to the field of electrical engineering, in particular, to devices for generating a reference voltage, and can be used to create low-noise sources of stable DC voltage.

State of the art

A device for generating a reference voltage containing a reference voltage source and a capacitor that acts as a low-pass filter ((https://www.datasheetarchive.com/MAX872-datesheet.html), (Horowitz P., Hill W. The art of circuitry. - M. : World, 1997 - 704 p., See p. 361)).

The disadvantage of this device is a significant level of noise, especially low-frequency

The inefficiency of the low-pass filter is due to the inability to use large capacitors in the filter circuit due to the limited capacitive load of the reference voltage source.

Known low-noise voltage source (low-noise voltage reference), the output signal of which is the difference voltage of two signals previously subjected to low-pass filtering and generated by a zener diode with a forbidden voltage. The basis of the process of implementing the actions of this device (US 4795961 A (Unitrode corporation), 01/03/1989 (5 L))) is the combined cycle system (Ivashchenko NN Automatic regulation. Theory and elements of systems. M., "Engineering" , 1973, 606 pp. - p. 9). At the same time, the feedback signal (the output of the device, the voltage divider 84, the base of transistors 52, 62) acts as a regulatory action.

The disadvantage of this device is a significant noise level due to the fact that the desire to reduce noise in the low and infra-low frequencies is accompanied by an increase in the likelihood of impulse noise, due to the uncorrelated noise components in the signals taken from the collectors of transistors 52, 62 and serving as the basis for the formation of the output voltage source.

A well-known reference voltage source, SU 421002A (All-Union Scientific Research and Design Institute of Scientific Instrument Making), 03/25/1974 (2 l), which, according to the process of implementing actions, is a closed loop system (Ivashchenko NN Automatic regulation. Theory and elements of systems. M., "Mechanical Engineering", 1973, 606 pp. - p. 9). In this case, the feedback signal (capacitor 7, amplifier 5, resistor 6, RC filter 4, acts as the regulatory action), and the output voltage of the stabilizer 1 is used as the control action.

The disadvantage of this device is a significant noise level due to the fact that the phase shift in the feedback circuit generates a dynamic error of the closed-loop control system and leads to a contradiction: the desire to reduce the noise level in the low and infra-low frequencies leads to the preservation (invariance) of the high-frequency noise level.

The closest analogue is the prototype of the claimed technical solution is a device for generating a reference voltage with a low noise level (patent RU 2422874, IPC G05F 3/08, 06/27/2011).

The device for generating a reference voltage with a reduced noise level contains a stabilizer, a capacitor, a subtracter, while the output of the stabilizer directly and through a capacitor is connected, respectively, to the first and second inputs of the subtractor, the output of which is the output of the device for forming a reference voltage with a reduced noise level.

The subtractor contains four resistors and an operational amplifier: the output of the operational amplifier serves as the output of the subtractor; the non-inverting input of the operational amplifier is connected to the second and first contacts, respectively, of the first resistor and second resistor; the inverting input of the operational amplifier is connected to the second and first contacts, respectively, of the third resistor and fourth resistor; the first contacts of the first resistor and the third resistor are, respectively, the first and second inputs of the subtractor; the second contact of the second resistor is grounded; the second contact of the fourth resistor is connected to the output of the operational amplifier.

The degree of suppression of the noise component is largely determined by the time constant of the high-pass filter of the prototype τ _HPF.prot formed by the capacitor C1, the first and second subtractor resistors R1, R2, which means the phase shift of the noise component of the prototype ϕ _SH.S.prot (ω), where ω is the current the frequency allocated by the noise component will be determined by the dependence

At the same time on τ _HPF.prot , R ₁ and R _{2 the} conditions are imposed:

where R ₃ , R ₄ - the resistance of the third and fourth resistors of the subtractor.

Since the fulfillment of condition (3) (namely: τ _HPF.prot >> 1 s) is technically unfeasible (an increase in the nominal values of the elements, in order to increase τ _HPF.prot , will lead to unstable operation of both the operational amplifier of the subtractor and the stabilizer), which means that there will be incomplete suppression of the noise component (in the region of infra-low frequencies), or in other words, there will be narrow-band compensation of the noise component of the output voltage of the stabilizer, due to the occurring phase shift. In particular, modeling the process of forming the reference voltage with a reduced noise level (performed in the Electronics Workbench Multisim 8 Simulation & Capture Version 8.2.12 program), in the case of using elements with maximum permissible parameters: C ₁ = 1 μF; R ₁ = R ₂ = R ₃ = R ₄ = 500 kOhm; (τ _HPF.prot = 1 s), showed the frequency dependence of both the phase shift of the noise component of the prototype ϕ _SH.S.prot (ω) and the noise suppression coefficient of the prototype K _PSh.prot (ω), table 1.

The instantaneous noise output voltage level of the prototype device U _{W. prot} is determined by the expression:

where U _{W. ct} is the instantaneous noise level of the stabilizer;

U _{sh.OU. habit} - instant noise level of the operational amplifier (op-amp) of the subtractor.

Studies have shown the possibility of reducing the noise of the stabilizer (in particular, IC:

- MAX872 (https://pdf1.alldatasheet.com/datasheet-pdf/view/73832/MAXIM/MAX872.html);

- ADR584 (chrome-extension: // oemmndcbldboiebfnladdacbdfmadadm / http: //www.analog.com/media/en/technical-documentation/data-sheets/AD584.pdf),

when using as an op-amp subtractor, IC OR07C, with an equivalent input noise of 0.38 μV (peak-to-peak) in the frequency band 0.1 ÷ 10 Hz (https://pdf1.alldatasheet.com/datasheet-pdf/view/73497/MAXIM/ OP07CCSA.html), table 2.

The disadvantages of the prototype device are:

- a significant level of the noise component of the infra-low-frequency range, while at the same time high requirements for the capacitor value (ideally, for the time constant τ _HPF it is desirable to fulfill the condition: τ _HPF >> 1 s);

- inversion of the polarity of the generated reference voltage relative to the polarity of the output voltage of the used stabilizer.

Disclosure of invention

The technical result that can be achieved using the present invention is to reduce the noise level and bring the polarity of the generated reference voltage to the polarity of the output voltage of the stabilizer used.

The technical result is achieved by the fact that in the device for generating a reference voltage containing a stabilizer, capacitor, subtractor, while the output of the stabilizer is connected to the first contact of the capacitor and the first input of the subtractor, the output of which serves as the output of the device, introduced, connected in series, a scaling voltage follower, divide the voltage and a voltage follower, the second contact of the capacitor connected to the input of the scaling voltage follower, the second input of the subtractor connected to the output m of the voltage follower.

The scaling voltage follower contains three resistors and an operational amplifier: a non-inverting input of the operational amplifier, through the first resistor, connected to the input of the scaling voltage follower; the inverting input of the operational amplifier is connected to the second and first contacts, respectively, of the second and third resistor; the first contact of the second resistor is grounded; the second contact of the third resistor is connected to the output of the operational amplifier, which serves as the output of the scaling voltage follower.

Voltage sharing contains two resistors: the input of the voltage divider is connected to the first contact of the first resistor; the second contact of the first resistor and the first contact of the second resistor are connected to the output of the voltage divider, the second contact of the second resistor is grounded.

The voltage follower contains an operational amplifier, while the non-inverting input of the operational amplifier is connected to the input of the voltage follower, the inverting input of the operational amplifier is connected to the output of the operational amplifier and the output of the voltage follower.

The subtractor contains four resistors and an operational amplifier: the output of the operational amplifier serves as the output of the subtractor; the non-inverting input of the operational amplifier is connected to the second and first contacts, respectively, of the first resistor and second resistor; the inverting input of the operational amplifier is connected to the second and first contacts, respectively, of the third resistor and fourth resistor; the first contacts of the first resistor and the third resistor are, respectively, the first and second inputs of the subtractor; the second contact of the second resistor is grounded; the second contact of the fourth resistor is connected to the output of the operational amplifier.

Brief Description of the Drawings

In FIG. 1 is a functional diagram of a device for generating a reference voltage with a reduced noise level.

In FIG. 2 is a functional diagram of a scaling voltage follower.

In FIG. 3 shows a functional diagram of a voltage divider.

In FIG. 4 is a functional diagram of a voltage follower.

In FIG. 5 is a functional diagram of a subtractor.

In FIG. Figure 6 shows a model of a device for generating a voltage reference with reduced noise level made in the Electronics Workbench Multisim 8 Simulation & Capture Version 8.2.12 program.

The implementation of the invention

The device for generating a reference voltage with a reduced noise level, Fig. 1, contains a stabilizer 1, a capacitor 2, a scaling voltage follower 3, a voltage divider 4, a voltage follower 5, a subtractor 6, wherein the output of the stabilizer 1 is directly connected to the second input of the scaling subtractor 4, and through a series-connected capacitor 2, a scaling voltage follower 3, a voltage divider 4, a voltage follower 5, is connected to the first input of the subtractor 6, the output of which is the output of the device .

The scaling voltage follower 3, FIG. 2, contains three resistors 7 ÷ 9 and an operational amplifier 10, wherein: the non-inverting input of the operational amplifier 10, through a resistor 7, is connected to the input of a scaling voltage follower 3; the inverting input of the operational amplifier 10 is connected to the second and first contacts, respectively, of the resistor 8 and the resistor 9; the first contact of the resistor 8 is grounded; the second contact of the resistor 9 is connected to the output of the operational amplifier 10, which serves as the output of the scaling voltage follower 3.

Share voltage 4, FIG. 3, contains two resistors 11 and 12, moreover: the input of the voltage divider 4 is connected to the first contact of the resistor 11; the second contact of the resistor 11 and the first contact of the resistor 12 are connected to the output of the voltage divider 4, the second contact of the resistor 12 is grounded.

Voltage follower 5, FIG. 4, comprises an operational amplifier 13, wherein: the non-inverting input of the operational amplifier 13 serves as the input of a voltage follower 5; the output of the operational amplifier 13 serves as the output of the voltage follower 5; the inverting input of the operational amplifier 13 is connected to the output of the operational amplifier 13.

Subtractor 6, FIG. 5, contains four resistors 14 ÷ 17 and an operational amplifier 18, moreover: the output of the operational amplifier 18 serves as the output of the subtractor 6; the non-inverting input of the operational amplifier 18 is connected to the second and first contacts, respectively, of the resistor 14 and the resistor 15; the inverting input of the operational amplifier 18 is connected to the second and first contacts, respectively, of the resistor 16 and the resistor 17; the first contacts of the resistor 14 and the resistor 16 are, respectively, the first and second inputs of the subtractor 6; the second contact of the resistor 15 is grounded; the second contact of the resistor 17 is connected to the output of the operational amplifier 18.

A device for forming a voltage reference with a low noise level works as follows.

We will analyze the operation of the device based on the model, FIG. 6, performed in Electronics Workbench Multisim 8 Simulation & Capture Version 8.2.12. A distinctive feature of the model is the presence of: a power supply unit (Blok_Pitania); device load resistance (resistor R10); electrical measuring instruments (ХММ1, ХММ2, Amp1); Oscilloscope (XSC1).

The output signal of the stabilizer 1, contains the noise component U _W (ω), extracted from the output signal using a capacitor 2 (C1) and fed to the input of the scaling voltage follower 3.

The scaling voltage follower 3 is made according to a non-inverting amplifier circuit characterized by the parameters:

where R _I.OU , K _OU - input (differential) resistance and gain of the operational amplifier (OU) 10;

R _{input MPN} , K _MPN - input resistance and gain (transmission) of the scaling voltage follower 3;

R1 ₇ , R2 ₈ , R3 ₉ - 1 ÷ 3 resistors (elements 7 ÷ 9) of the scaling voltage follower 3, with a resistance of 50 kΩ, FIG. four.

The instant noise level U _{w. MPN} (ω), at the output of the scaling voltage follower 3, is described by expression (6);

where U _{W. OU.MPN} (ω) is the instantaneous noise level of the operational amplifier 10 of the scaling voltage follower 3.

According to the accepted values of the resistances of resistors R2 ₈ , R3 ₉ , there is a ratio:

The selected and converted noise component, from the output of the scaling voltage follower 3, is supplied to a voltage divider 4 with a division ratio:

where R4 ₁₁ , R5 ₁₂ - 1 and 2 resistors (elements 11 and 12) voltage divider 4, with a resistance of 500 Ohms, FIG. 6, and then to the voltage follower 5, which functions as a buffer stage.

According to the accepted values of the resistances of the resistors R4 ₁₁ , R5 ₁₂ , there is a ratio:

The instant noise level U _{W. PN} (ω), at the output of the voltage follower 5, is described by the expression (10);

where U _{W. OU.PN} - the instantaneous noise level of the operational amplifier 13 voltage follower 5.

The output signals of the voltage follower 5 and the stabilizer 1 are fed to the inputs of the subtractor 6, which compensates (suppresses) the noise component.

The following condition is imposed on the elements of the subtractor 6:

where R6 ₁₄ , R7 ₁₅ , R8 ₁₆ , R9 ₁₇ - 1 ÷ 4 resistors (elements 14 ÷ 17) of the subtractor 6, FIG. 5, with a resistance of 50 kΩ, FIG. 6.

The instantaneous noise output voltage level of the device U _w (subtractor 6) is determined by the expression:

where U _{sh.OU. habit} - the instantaneous noise level of the operational amplifier 18 of the subtractor 6;

K _PN - noise reduction coefficient of the device.

Due to the advisability of using the same type of operational amplifier as part of the scaling voltage follower 3, voltage follower 5 and subtractor 6 circuits, as well as taking into account expressions (7) and (9), expression (12) takes the form:

where U _{W. OU} - the instantaneous noise level of the operational amplifier used as part of the scaling voltage follower 3, voltage follower 5 and subtractor 6.

The degree of suppression of the noise component in the output voltage of the device is largely determined by the time constant of the high-pass filter of the device τ _HPF formed by the capacitor 2 and the input resistance R in. _{MPN of the} scaling voltage follower 3. The phase shift of the noise component of the stabilizer 1 introduced by the high-pass filter device ϕ _AL (ω), is determined by the expression (14)

Where

where C1 ₂ is the capacitance of capacitor C1, FIG. 6 (element 2, Fig. 1).

In this case, on the _{HPF, the} condition is imposed:

Given the significant input impedance of the operational amplifier 10 used in the scaling voltage follower 3 circuit (for example, IC ОR07С, with parameters R _{input ОУ} = 8 ÷ 33 МОм, K _ОУ = 100 ÷ 120 dB (10 ⁵ ÷ 10 ⁶ ) (http: / /pdf1.alldatasheet.com/datasheet-pdf/view/73497/MAXIM/OP07CCSA.html), as well as the resistance of the resistor R1 ₇ (limiting the input current of the operational amplifier 10), the input impedance of the scaling voltage follower 3-R in. _MPN significantly exceeds 1 GOhm (even taking into account leakage currents), which, in turn, ensures the fulfillment of conditions both (16) and (17)

And it contributes to better suppression of the noise component (especially in the field of infra-low frequencies) in the output signal of the proposed device in comparison with the prototype.

The receipt of signals from the output of the stabilizer 1 to the first input of the subtractor 6 (non-inverting input of the operational amplifier 18) and from the output of the voltage follower 5 to the second input of the subtractor 6 (inverting input of the operational amplifier 18) provides the polarity of the generated reference voltage to the polarity of the output voltage of the used stabilizer.

Simulation of the process of forming the reference voltage with a reduced noise level (performed in the Electronics Workbench Multisim 8 Simulation & Capture Version 8.2.12 program), using a scaling voltage follower 3, voltage follower 5 and subtractor 6, OU IMS OR07C (R _{in. MPN} ≈1 GOhm) and capacitor 2 with capacitance C1 ₂ = 0.1 μF (τ _HPF = 100 s),), as well as 0.01 μF (τ _HPF = 10 s), showed

Studies have shown the possibility of reducing the noise of the stabilizer (in particular, IC MAX872, ADR584 when used as an op amp IC OP07С, and a capacitor 2 with a capacitance C1 ₂ = 0.1 μF, table 4.

As follows from the analysis of the data in tables 1 ÷ 4, the proposed device provides the most significant reduction in the level of the noise component of the output signal in the infra-low frequency range, while reducing the requirements for the capacitance of the capacitor 2.

Claims (1)

A device for generating a reference voltage with a reduced noise level, comprising a stabilizer, a capacitor, a subtracter, while the output of the stabilizer is connected to the first contact of the capacitor and the first input of the subtractor, the output of which serves as the output of the device, characterized in that a scaling voltage follower, a divider, are connected in series voltage and voltage follower, the second contact of the capacitor connected to the input of the scaling voltage follower, the second input of the subtractor connected to the output of the voltage follower, wherein the scaling voltage follower comprises three resistors and an operational amplifier, a non-inverting input of the operational amplifier through the first resistor is connected to the input of the scaling voltage follower; the inverting input of the operational amplifier is connected to the second and first contacts, respectively, of the second and third resistor; the first contact of the second resistor is grounded; the second contact of the third resistor is connected to the output of the operational amplifier, which serves as the output of the scaling voltage follower, while the voltage divider contains two resistors, the input of the voltage divider is connected to the first contact of the first resistor; the second contact of the first resistor and the first contact of the second resistor are connected to the output of the voltage divider, the second contact of the second resistor is grounded, while the voltage follower contains an operational amplifier, the non-inverting input of which is connected to the input of the voltage follower, the inverting input of the operational amplifier is connected to the output of the operational amplifier and the output of the follower voltage, and the subtractor contains four resistors and an operational amplifier, the output of the operational amplifier serves as the output of the subtractor; the non-inverting input of the operational amplifier is connected to the second and first contacts, respectively, of the first resistor and second resistor; the inverting input of the operational amplifier is connected to the second and first contacts, respectively, of the third resistor and fourth resistor; the first contacts of the first resistor and the third resistor are, respectively, the first and second inputs of the subtractor; the second contact of the second resistor is grounded; the second contact of the fourth resistor is connected to the output of the operational amplifier.

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