RU2466493C1 - Method to generate reference voltage - Google Patents

Abstract

FIELD: electric engineering.

SUBSTANCE: method to generate reference voltage is characterised by the fact that a noise component is identified in stabilized voltage for further subtraction of the noise component from the stabilised voltage, at the same time, prior to identification of a noise component from the stabilised voltage, the operation of stabilised output voltage spectrum conversion is carried out, providing for narrowing of the spectral band of the noise component in the reference voltage source signal, both at the side of infralow and ultrahigh frequencies.

EFFECT: method provides for mobile start-up and braking without use of additional equipment.

10 dwg

Description

FIELD OF THE INVENTION

The invention relates to the field of electrical engineering, in particular to methods of forming a reference voltage, and can be used to create sources of stable DC voltage.

State of the art

A known method of forming a reference voltage, including the operation of: stabilizing the output voltage; subsequent filtering of the output voltage ((http://www.datasheetarchive.com/MAX872-datasheet.html), (Horowitz P., Hill W. Art of circuitry. - M.: Mir, 1997 - 704 p., see p. 361)).

The disadvantage of this method and device for its implementation is a significant level of low-frequency noise.

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

A known method of generating a reference voltage based on a low-noise voltage reference (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. The implementation process of this method (US 4795961A (Unitrode corporation), 01/03/1989 (5 L)) is based on a combined cycle system (Ivashchenko NN Automatic regulation. Theory and elements of systems. M.: "Engineering", 1973, 606 p. - p. 9). In this case, the feedback signal (the output of the device, the voltage divider 84, the base of transistors 52, 62) acts as a regulatory influence.

The disadvantage of this method is a significant level of noise, accompanied by impulse noise.

A known method of forming a reference voltage on the basis of a reference voltage source, SU 421002 (All-Union Scientific Research and Design Institute of Scientific Instrument Engineering), 03/25/1974 (2 l)), which, according to the process of implementation of the method, is a closed loop system (N. Ivashchenko. N. Automatic Regulation, Theory and Elements of Systems, Moscow: Mashinostroenie, 1973, 606 pp. - p. 9). In this case, the feedback signal (capacitor 7, amplifier 5, resistor 6, RC filter 4 acts as a regulatory action), and the output voltage of the stabilizer 1 acts as a control action), Fig. 1, description of the invention to AC SU 421002.

The phase shift of the feedback circuit generates a dynamic error of the closed-loop control system.

The phase shift of the feedback circuit is due to the structure of the circuit itself.

1. The RC filter 4 is a multi-link (n-link) with the time constant of the links τ _LF.i and phase response of the form (1):

2. The process of generating a difference signal and its inversion by amplifier 5 is assumed without a significant time delay (without phase shift). Inverting provides a negative feedback mode.

3. The capacitor 7 with the internal resistance of the stabilizer 1 (at the connection point of the capacitor 7) form an RC filter, which is an RF element with a time constant τ _RF and phase- _frequency response of the form (2):

4. In general, the feedback circuit, and therefore the regulatory effect, is characterized by the phase response of the form (3):

As

where R ₈ , R ₉ is the resistance of the quenching resistors 8 and 9 (usually not more than 350 Ohms);

R _vn.ip - internal resistance of the power source (usually not more than 100 Ohms);

R _output.sc.n is the output resistance of the load circuit of the reference voltage source (of the order of 500 Ohms in the region of infralow frequencies and tens of Ohms in the region of high frequencies, we take 100 Ohms);

C ₇ is the capacitance of capacitor 7 (as a rule, no more than 2.2 μF), we have: τ _HF = 4.95 · 10 ^-4 s.

That is, the cutoff frequency of the RF link is 2020.202 rad / s or 321.525 Hz (the normalized noise range of the voltage sources is [0.1 ÷ 10] Hz) ( http://www.datasheetarchive.com/MAX872-datasheet.htm ).

In the case of establishing a resistor 6 with a resistance of the order of 1 MΩ equal to the total resistance of the filter 4 resistors and using capacitors with a capacitance of 2.2 μF in the filter links 4, the magnitude of the phase shift of the regulatory action in the normalized frequency range, depending on the number of filter links 4, will be, according to table 1:

Table 1 The number of links, n φ, [°], at f = 0.1 Hz φ, [°], at = 0.15 Hz φ, [°], at f = 10 Hz one 35.87 25.72 -1.37 2 20.68 -2.09 -90.12 3 15.77 -13.98 -178.05 four 13.73 -19.63 -265.15

From an analysis of the results obtained, we can conclude that there is a certain decrease in the noise level only in a narrow interval of the normalized frequency range, primarily the infralow (in the vicinity of 0.15 Hz), since only for it the conditions for the formation of negative feedback are satisfied. Due to the occurrence of positive feedback in a significant region of the normalized frequency range, the process of suppressing infra-low frequencies at the output of the reference voltage source is accompanied by the occurrence of pulsed interference.

As for the medium and high frequencies (more than 10 Hz), the degree of noise suppression is largely determined by the capacitance of the capacitor 3, the value of which is limited by the value of the capacitive load of the reference voltage source.

The disadvantage of this method is a significant level of noise, accompanied by impulse noise.

A known method of forming a reference voltage with a reduced noise level (RF patent No. 2422874), based on the principles of open-loop systems and including operations:

1) stabilization of the output voltage;

2) the allocation of the noise (variable) component of the output voltage by means of a high-pass filter;

3) compensation of the noise (variable) component in the stabilized voltage.

The degree of suppression of the noise component is largely determined by the time constant of the subtractor circuit 3 τ _in (Figs. 1 ÷ 3, patent specification No. 2422874), which, in fact, is an RC high-pass filter with a phase response of the form:

Where

where C1 ₂ is the capacitance of the capacitor 2;

R1 ₄ - resistance of the first resistor 4;

R2 ₅ - resistance of the second resistor 5.

Moreover, on τ _in , R1 ₄ and R2 _{5 the} conditions are imposed:

where R3 ₆ is the resistance of the third resistor 6;

R4 ₅ - resistance of the fourth resistor 7.

Since the condition (7), namely: τ _a → ∞, in the case of elements with typical parameters (C1 = 2.2 microfarads _2; R1 = R2 _{4 5 6} = R3 = R4 = 500 k ₇₎ is not feasible, then there is incomplete suppression of the noise component (in the region of infra-low frequencies), or in other words, there is narrow-band compensation of the noise component of the output voltage, due to the occurring phase shift, table 2.

table 2 φ, [°], at f = 0.1 Hz φ, [°], at f = 0.15 Hz φ, [°], at f = 10 Hz φ, [°], at f = 100 Hz 35,883 25,747 0.414 0,041

The disadvantage of this method is the significant level of infra-low frequencies at the output of the reference voltage source, while at the same time high requirements for the time constant of the subtractor circuit (τ _in ≥1 (ideally, >> 1)).

Disclosure of invention

The technical result that can be achieved using the present invention is to reduce the noise level.

The technical result is achieved by the fact that in the method of forming the reference voltage, with a reduced noise level, based on the principles of open-loop systems and including the operation of stabilizing the output voltage, isolating the noise (variable) component of the output voltage using a high-pass filter, compensating the noise (variable) component in stabilized voltage, the operation of converting the spectrum of the stabilized output voltage is introduced, which is carried out until the noise (variable) with leaving the output voltage through a high-pass filter.

Brief Description of the Drawings

Figure 1 presents a functional diagram of a device that implements a method of forming a reference voltage.

Figure 2 presents the functional diagram of the subtractor.

Figure 3 presents the functional diagram of the Converter.

Figure 4 presents a model of a device that implements a method of forming a reference voltage, made in the program Electronics Workbench Multisim 8 Simulation & Capture Version 8.2.12.

Figure 5 presents the timing diagram of the output voltage of the power supply unit.

Figure 6 presents a graph of the noise component of the output signal of the reference voltage source.

7 is a graph of the converted noise component of the output signal of the reference voltage source.

On Fig presents a graph of the noise component of the output signal of the device implementing the method of forming the reference voltage for the case of C1 ₁₀ = C2 ₃ = 0.5 μF and R1 ₁₁ = R2 ₁₂ = R3 ₁₃ = R4 ₁₄ = R5 ₅ = R6 ₆ = R7 ₇ = R8 ₈ = 500 kOhm.

Figure 9 presents a graph of the noise component of the output signal of the prototype, for the case of C1 ₂ = 0.5 μF and R1 ₄ = R2 ₅ = R3 ₆ = R4 ₇ = 500 kOhm.

Figure 10 presents a graph of the noise component of the output signal of the prototype, for the case of C1 ₂ = 10 μF and R1 ₄ = R2 ₅ = R3 ₆ = R4 ₇ = 500 kOhm.

The implementation of the invention

The essence of the proposed method is to perform the following operations:

1) stabilization of the output voltage;

2) spectrum conversion of stabilized output voltage;

3) the allocation of the noise (variable) component of the converted output voltage by means of a high-pass filter;

4) compensation of the noise (variable) component of the output voltage.

A device for implementing the method of generating a reference voltage, Fig. 1, contains a reference voltage source 1, a converter 2, a separation capacitor 3, a subtractor 4, wherein the output of the reference voltage source 1 is connected to the input of the converter 2, the output of which, directly and through the isolation capacitor 3, connected, respectively, with the first and second inputs of the subtractor 4, the output of which is the output of the device implementing the method of forming the reference voltage.

The subtractor 4, figure 2, contains four resistors 5 ÷ 8 and an operational amplifier 9, moreover: the output of the operational amplifier 9 serves as the output of the subtractor 4; the non-inverting input of the operational amplifier 9 is connected to the second and first contacts, respectively, of the first resistor 5 and the second resistor 6; the inverting input of the operational amplifier 9 is connected to the second and first contacts, respectively, of the third resistor 7 and the fourth resistor 8; the first contacts of the first resistor 5 and the third resistor 7 are, respectively, the first and second inputs of the subtractor 4; the second contact of the second resistor 6 is grounded; the second contact of the fourth resistor 8 is connected to the output of the operational amplifier 9.

Converter 2, figure 3, contains a capacitor 10, four resistors 11 ÷ 14 and an operational amplifier 15, moreover: the output of the operational amplifier 15 serves as the output of the converter 2; the non-inverting input of the operational amplifier 15 is connected to the second and first contacts, respectively, of the first resistor 11 and the second resistor 12; the inverting input of the operational amplifier 15 is connected to the second and first contacts, respectively, of the third resistor 13 and the fourth resistor 14; the input of the converter 2 is connected directly and through a capacitor 10 to the first contacts of the third resistor 13 and the first resistor 11; the second contact of the second resistor 12 is grounded; the second contact of the fourth resistor 14 is connected to the output of the operational amplifier 15.

A device for implementing the method of forming the reference voltage operates as follows.

An analysis of the operation of the device will be based on the model, figure 4, made in the program 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 R9); electrical measuring instruments (ХММ1, ХММ2, U3); Oscilloscopes (XSC1, XSC2, XSC3).

Timing diagrams of the output voltage of the power supply unit of the device for implementing the method of forming the reference voltage are shown in Fig.5.

The output signal of the reference voltage source, for example, in the case of using the IC MAX6250 http://www.datasheets.maxim-ic.com/en/ds/MAX6225 - MAX6250.pdf), contains the noise component U ₁ (Fig.6), lower the spectral composition threshold of which corresponds to the infra-low frequency region (of the order of 0.1 Hz).

The Converter 2 reduces the level, but first of all it narrows the spectral band of the noise component of the signal of the reference voltage source 1, moreover, along with lowering the upper limit, the lower limit of the spectral band of the noise component of the signal component of the signal of the reference voltage source 1 is increased (Fig. 7). This effect is provided due to the algorithm of the converter 2:

1) the group delay of the envelope of the noise component of the signal of the reference voltage source 1, arising due to the passage of the signal through the high-pass filter formed by the capacitor 10, the first resistor 11 and the second resistor 12 (Figs. 3, 4)

where φ _pr (w) is the phase shift introduced by the high-pass filter

τ _vpr - time constant of the high-pass filter of the converter 2

C1 ₁₀ - capacitance of the capacitor 10;

R1 ₁₁ is the resistance of the first resistor 11;

R2 ₁₂ is the resistance of the second resistor 12;

2) subtracting from the signal the source of the reference voltage 1 of the delayed envelope of its noise component.

In this case, the condition is imposed on the resistance value of the resistors of the transducer 2:

Due to the non-periodicity and non-sinusoidality of the shape of the envelope of the noise component of the signal of the reference voltage source 1 and the frequency dependence of the group delay

infra-low-frequency and low-frequency fragments of the envelope of the noise component will undergo crushing and partial suppression, and high-frequency components will be suppressed (Fig. 7).

The noise component of the signal of the Converter 2 is allocated using the capacitor 3 (C2), (figure 4).

The allocated noise component and the output signal of the converter 2 are fed to the inputs of the subtractor 4, which compensates (suppresses) the noise component.

The value of the resistance of the resistors of the subtractor 4 imposes the condition:

where R5 ₅ , R6 ₆ , R7 ₇ , R8 ₈ is the resistance of the first resistor 5, the second resistor 6, the third resistor 7, and the fourth resistor 8.

The time constant of the circuit τ _in subtractor 4, which is, in fact, an RC filter of high frequencies, τ _in = τ _rf , is determined by the dependence

where C2 ₃ is the capacitance of the isolation capacitor 2.

Due to preliminary transformation of the spectrum of the noise component of the output signal of the reference voltage source 1, condition (14) is easily satisfied (in the case of the prototype, τ _rf ≥1 (ideally, >> 1)).

Timing diagram of the noise component of the output signal of a device that implements a method of generating a reference voltage in the case of C1 ₁₀ = C2 ₃ = 0.5 μF and R1 ₁₁ = R2 ₁₂ = R3 ₁₃ = R4 ₁₄ = R5 ₅ = R6 ₆ = R7 ₇ = R8 ₈ = 500 kOhm is shown in FIG.

The timing diagram of the noise component of the output signal of the prototype, implemented with the same parameters of the power supply and the reference voltage source, in the case of C1 ₂ = 0.5 μF and R1 ₄ = R2 ₅ = R3 ₆ = R4 ₇ = 500 kOhm, is shown in Fig. 9 .

The timing diagram of the noise component of the output signal of the prototype, implemented with the same parameters of the power supply and the reference voltage source, in the case of C1 ₂ = 10 μF and R1 ₄ = R2 ₅ = R3 ₆ = R4 ₇ = 500 kOhm, is presented in Fig. 10.

As follows from the analysis of Figs. 8, 9, there is a decrease in the level of the noise component of the output signal of the reference voltage source 1 by 20,000 and 1,500 times, respectively. That is, the introduction of the conversion operation of the spectrum of the stabilized output voltage leads to a decrease in noise level (relative to the prototype) by more than 13.3 times.

As follows from the analysis of Figs. 8, 10, the introduction of the spectrum conversion operation of the stabilized output voltage leads to a significant reduction in the time constant requirements of the high-frequency link circuit (relative to the prototype) by more than 20 times.

Claims (1)

A method of generating a reference voltage, according to which a noise component is extracted from the stabilized voltage for subsequent subtraction of the noise component from the stabilized voltage, characterized in that the isolation of the noise component from the stabilized voltage is preceded by the operation of converting the spectrum of the stabilized output voltage, which reduces the spectral band of the noise component of the signal of the reference voltage source from both infralow and ult avysokih frequencies.

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