RU2015618C1 - Method and device for pulse-time conversion of dc voltage into code - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: method of pulse-time conversion of a d. c. voltage into code involves the steps of: forming a main signal initial value proportional to an input one, at a first step, diminishing it up to zero at a second step, filling the time period of the second step with reference-frequency pulses and forming a code by counting them. The method is characterized in that at the first step two signals of one the same frequency and phase are formed one of which is a reference signal and the other is one to be adjusted, varying the phase of the latter by acting on it by an input voltage and forming the main signal initial value from the phase difference between the reference and adjusted signals, at the second step the adjusted signal is affected to the action of main one till reaching phase difference equal zero. The device for effecting method has a voltage-to-time interval converter, comparison unit, time interval meter, control unit. The device is characterized by the use of auxiliary switch, adder, adjustable generator, phase detector, low-pass filter, d. c. amplifier connected in series. EFFECT: enhanced speed with accuracy maintained. 2 cl, 3 dwg

Description

 The invention relates to measuring equipment and can be used when measuring voltage in systems for monitoring the electrical parameters of electronic circuits.

Known methods of time-pulse ADC, which consists in the fact that the measured voltage is compared with a voltage that varies linearly from zero to a value of U _m . The time interval is formed from the beginning of the cycle to the moment of coincidence of the input and linearly varying voltages.

A device for implementing this method comprises a comparison device, the first input of which is the input of the device, and the second input is connected to the output of a voltage linearly varying from zero to U _m , a selector, the first input of which is connected to the output of the comparison device, and the second to the output of the reference generator frequency and counter, the input of which is connected to the output of the selector. The measurement time in this case is constant and equal to the time of the ramp voltage increase from zero to U _m plus the recovery time of the initial state at the output of the ramp generator. This time interval is entirely used to fill the reference frequency pulses only when measuring the maximum input voltage. When measuring low voltages, that part of the measurement time, which is filled with pulses of the reference frequency, is significantly reduced. This leads to inefficiency in the use of devices that implement this method when measuring voltages in a wide dynamic range.

 A known method of time-pulse ADC, which consists in the fact that the input signal is compared with two paraphase sawtooth voltages.

 A device for implementing this method comprises a paraphase sawtooth voltage generator with two outputs, the first of which is connected to the first input of the first comparison device, and the second to the first input of the second comparison device, the second inputs of the comparison device being combined and being the input of the device, the outputs of the comparing device with the inputs of the EXCLUSIVE OR element, the output of the EXCLUSIVE OR element is connected to the first input of the AND element, the second input of which is connected to the output of the pulse generator, and you move - with the input of the counter.

 The disadvantages of these methods and devices that implement them can be attributed to low accuracy due to the influence of non-linearity and steepness of the ramp voltage and low noise immunity to network noise.

 Given the shortcomings, the above methods of time-pulse ADC in the construction of voltmeters are used little.

 The closest in technical essence and the achieved effect to the invention is a time-pulse ADC method, according to which in the first cycle the measured voltage is integrated over a constant time interval, and in the second cycle the voltage is reset using the reference voltage.

 A device for time-pulse conversion of DC voltage to a code selected as a prototype, comprising a voltage converter in a time interval made on an integrator, a comparison device, a time interval meter and a control unit.

 A disadvantage of the known method and device is that most of the measurement time is the time of preparatory operations. The measurement time is the sum of the integration time of the input voltage and the integration time of the reference input voltage, which is opposite in sign. Measurement takes place only in the second measure.

U_xdt =

· t, где RC - постоянная времени интегратора;
t - независимая переменная величина (время).In the first cycle, during the time T _{, the} input voltage U _{x is} integrated, as a result, the voltage at the output of the integrator is
U ₁ =

U _x dt =

· T, where RC is the integrator time constant;
t is an independent variable (time).

At the end of the integration interval, the voltage at the output of the integrator U ₁ = U _x T _and / RC.

·T_и-

U_опdt =

· T_и-

· t, а в конце этого периода
U₂(t) =

· T_и-

· T_x, откуда Т_х = U_x˙Т_и/U_оп.During the second cycle, the reference voltage U _op having the opposite polarity with respect to U _{x is} integrated. The integration of the reference voltage continues until the output voltage of the integrator again becomes equal to zero. Therefore, during the time of the second cycle, the voltage at the output of the integrator
U ₂ (t) =

T _and -

U _op dt =

T _and -

T, and at the end of this period
U ₂ (t) =

T _and -

· T _x , whence T _x = U _x ˙Т _and / U _op .

 Further, the obtained interval is filled with reference frequency pulses, which are counted using a counter.

Thus, the operation of the prototype device that implements the prototype method is divided into two stages: converting the input voltage to the initial amplitude of the decreasing voltage U ₂ (t) (the input voltage is being integrated) and measuring the signal lifetime U ₂ (t) when measuring it from the initial value U ₁ (Т _и ) = U _x ˙Т _and / RC to zero.

The time interval is measured by filling it with pulses of the reference frequency. The interval of existence of voltage U ₂ (t) (at the output of the integrator) is the larger, the greater the voltage U ₁ (T _and ) obtained in the first cycle.

 This method has been widely used to create voltmeters due to a significant increase in accuracy compared to the methods described above, eliminating the influence of the integrator time constant and high noise immunity to network noise.

The measuring time consists of the time of converting an input voltage U _x to the initial amplitude U ₁ (T _i) varying the signal U ₂ (t) - T _u and the lifetime (decrease from U ₁ (T _n) to zero) the signal - T _x:
T _ISM = T _and + T _x .

Under the condition U _{x makc} = U _op , the measurement time of the maximum input voltage U _{x makc} is
T _ISM = 2 ˙ T _x .

Information about the amplitude of the input signal comprises only the time interval T _x, and during the time interval T _and preparatory operations occur. At the same time, T _{n is} commensurate with T _x (they can even be equal). This is a disadvantage of the specified method and device.

 The purpose of the invention is to reduce the time of analog-to-digital conversion by reducing the time of preparatory operations.

The goal is achieved in that they generate a signal of the reference frequency, acting on the input signal U _x , change the phase of the reference signal, form a voltage U _f proportional to the phase difference between the reference U _о and the received U _p as a result of the input voltage U _x signals. The voltage amplitude U _f is the initial amplitude of the changing signal from U _f to zero. The polarity of the voltage U _{f is the} opposite of the polarity of the input voltage U _x . The signal U _f proportional to the phase difference acts on the signal U _p , reducing the resulting phase difference. When the phase difference between the signals U _o and U _p decreases, the voltage U _f decreases. As a result, the signal U _f decreases from the initial value to zero. The time interval of the existence of the signal U _f fill pulses of the reference frequency. The lifetime of the signal U _f (t) is proportional to the initial amplitude of the signal, which, in turn, is proportional to the input voltage. Thus, the goal is achieved in that the initial amplitude U _{f of the} changing signal is determined by the phase difference between the sample and adjustable signals, while the frequency of the adjustable signal is determined by the level of the input signal.

 The goal is also achieved by the fact that in a device containing a voltage converter in a time interval, a comparison unit, a time interval meter and a control unit, a voltage converter in a time interval is made on the basis of a phase locked loop (PLL), including a series-connected key, an adder with two inputs, a tunable generator connected to the first input of the phase detector, a low-pass filter, a DC amplifier connected to the second input of the adder, as well as a generator p exemplary frequency connected to the second input of the phase detector.

 The time interval meter contains an AND element with two inputs, the first input of which is the input of the meter, the second input is connected to the output of the reference frequency generator, and the output is connected to the counter input, the "Reset" input of which is connected to the output of the control unit.

 Comparison of the claimed technical solutions with prototypes made it possible to establish compliance with their criterion of "novelty." When studying other technical solutions, it was determined that the PLL system is widely used in generators, frequency synthesizers, phase calibrators, etc. in order to stabilize the frequency and improve accuracy, but during the pulse ADC in order to improve performance, the PLL system was not used.

 A diagram of a device implementing the method is shown in FIG. 1; control unit circuit - in FIG. 2; timing diagrams explaining the method and operation of the device are shown in FIG. 3.

The proposed method is as follows. Two signals of the same frequency and phase are formed, one of which is called exemplary U _o (t), and the other is tunable U _p (t). The input signal U _x affect the adjustable signal U _p (t) and change the phase of this signal. As a result, a phase difference Δφ appears between the exemplary U _о (t) and the tunable U _p (t) signals. Form a voltage U _f proportional to the phase difference Δ φ. The voltage U _{f is} opposite in sign to the input voltage U _x . Voltage U _f affect the adjustable signal U _p (t) and change the phase of this signal. As a result, the resulting phase difference decreases. When Δ φ decreases, the voltage U _f decreases. The time interval during which the resulting phase difference Δφ is compensated is filled with reference frequency pulses and the voltage U _x is judged by their number, since U _{f is} proportional to the phase difference Δφ, and the phase difference Δφ is proportional to the input voltage U _x . Thus, in the first cycle, a voltage U _f is proportional to the input voltage U _x , in the second cycle, the time interval during which the voltage U _f decreases to zero is filled with reference frequency pulses.

 The device comprises a voltage converter 1 in a time interval, the input of which receives the measured voltage, and the output is connected to the first input of the comparison unit 2. The second input of the comparison unit is connected to a common bus. The meter 3 time intervals connected to the output of block 2 comparison. The control unit 4 is connected to the inputs of the transducer 1 and the meter 3. The voltage transducer 1 in the time interval is based on a PLL system including a key 5 connected in series, an adder 6 with two inputs, an adjustable oscillator 7 connected to the first input of the phase detector 8, filter 9 low frequencies, a DC amplifier 10 connected to the second input of the adder 6, while the reference frequency generator 11 is connected to the second input of the phase detector 8. The control unit 4 is connected to the control input of the key 5 and to the control input of the counter 12 in the time interval meter 3, which also contains a reference frequency generator 13 and an I 14 circuit, one input of which is connected to the output of the comparison unit 2 and the other to the output of the generator 13 reference frequency. The control unit 4 can be made in the form of an sharpener and contains a trigger on the elements 15 and 16 and a pulse sharpener on the elements 17 and 18.

 The device operates as follows.

At the moment of arrival of the signal U _c from the control unit 4 (by the “start” command) to the control input of the key 5, the input voltage U _x through the key 5 is supplied to the first input of the adder 6. Since the second input of the adder 6 comes from the amplifier at the initial time 10, the voltage is equal to zero, then the voltage equal to the input acts on the control element of the adjustable generator 7. Due to the influence of the voltage U _x on the control element of the adjustable generator 7, a phase change in the phase Δφ of the signal of the generator 7 occurs. At the output of the phase detector 8, the voltage U _f is proportional to the phase jump Δφ. The voltage from the output of the phase detector 8 through the filter 9 and the amplifier 10 is supplied to the second input of the adder 6. Since the duration of the control pulse coming to the key 5 is chosen very short (on the order of several nanoseconds), then by the time the signal arrives at the second, the input of the adder 6 , its first input is set to zero voltage. Thus, the voltage from the phase detector 8 U _f through the filter 9, the amplifier 10 and the adder 6 is supplied to the control element of the adjustable generator 7 and reduces the resulting phase difference Δ φ between the signals of the reference 11 and the adjustable 7 generators. Gradually, the phase difference Δ φ is reduced to zero and the voltage at the output of the phase detector 8 U _f becomes equal to zero. When voltage appears at the output of the phase detector, the logical 1 signal appears at the output of the comparison unit 2 and allows the pulses to pass from the reference frequency generator 13 through the I 14 circuit to the counter 12. Before the pulse measurement starts from the control unit 4, all the bits of the counter 12 are reset. After the resulting phase difference Δ φ is compensated and the voltage at the output of the phase detector 8 U _f again becomes less than U _fp , a logical “0” signal appears at the output of the comparison unit 2 and the passage of pulses from the reference frequency generator 13 to the counter stops. The pulse duration at the output of the comparison unit 2 is proportional to the measured voltage U _x . The greater the input voltage U _x , the greater the voltage at the output of the phase detector, and therefore the time during which the voltage arising at the output of the phase detector is compensated. By changing the parameters of the feedback elements of the amplifier filter, it is also possible to change the compensation time of the voltage detector that appeared at the output of the phase detector.

Thus, the operation of devices made according to the specified method is divided into two clock cycles: converting the input voltage to the initial amplitude of the decreasing signal U _f at the output of the phase detector and measuring the lifetime of the signal U _f at the output of the phase detector (U _f > U _fp ).

The measurement time is the sum of the conversion time of the input voltage to the initial amplitude of the signal at the output of the phase detector U _f - T ₁ and the time of existence of this signal - T _x :
T _ISM = T ₁ + T _x .

The compensation time of the voltage U _f arising at the output of the phase detector is entirely determined by the inertia of the feedback circuit, and the time to establish the phase of the adjustable oscillator can be taken equal to zero. Based on the foregoing, the time T ₁ can be considered equal to zero. Hence the measurement time T _ISM = T _x .

Given that at the same reference frequency, resolution, and the same voltage U _{x, the} time T _{x is the} same (the time interval that is filled with the reference frequency) for the inventive device and prototype, they have a 2-time reduction in measurement time, since the prototype T is _iz = 2 T _x , and according to the proposed method, T _ISM = = T _x .

 Thus, the proposed method when measuring the maximum allowable input voltage reduces the conversion time by 2 times. When measuring voltages less than the maximum allowable, time savings are even greater. It is the claimed layout of the circuit and its parameters that reduce the time of voltage measurement.

 Using the proposed method of a time-pulse ADC and a device allows, in comparison with the existing and methods, devices to obtain a significant reduction in measurement time, which is important, for example, when used in monitoring systems of the electrical parameters of electronic circuits. Due to the widespread use in the industry of microprocessors, LSI and analog integrated circuits of increased complexity, difficulties arose due to a sharp increase in the required volume of control and diagnostic operations, which account for about 50% of the total complexity of manufacturing electronic products. Given that when monitoring modern LSIs, the number of test packages can reach 500,000, it becomes obvious the need to reduce the time spent on each operation. This significantly reduces the cost of electronic products. In addition, the invention can be used in experiments to create high-speed multi-bit voltage measuring instruments.

Claims (2)

 1. A method of time-pulse conversion of DC voltage to a code based on the formation at the first stage of the initial value of the main signal proportional to the input voltage, decreasing it to zero at the second stage, filling the time interval from the beginning to the end of the second stage with reference frequency pulses and forming the stroke by counting, characterized in that, in order to improve performance while maintaining accuracy, additionally at the first stage, model and adjustable signals are generated with the same hour The phase and its phase, by affecting the latter by the input voltage, change its phase; when forming the initial value of the main signal, the signal used is the signal opposite in sign to the input voltage and proportional to the phase difference of the reference signal and the signal being modified with the changed phase, and in the second stage, the main signal to be tunable, change its phase until the phase difference between it and the reference signal becomes equal to zero.  2. A device for the time-pulse conversion of DC voltage to a code containing a voltage converter in a time interval, executed on a model frequency generator and a key, the information input of which is an input bus, and the control input is connected to the first output of the control unit, the second output of which is connected to the first input a time interval meter, the outputs of which are the output bus, and the second input is connected to the output of the comparison unit, the inputs of which are connected to the output of the converter in a time interval, characterized in that, in order to improve performance while maintaining accuracy, a series-connected adder, an adjustable oscillator, a phase detector, a low-pass filter and a DC amplifier, the output of which is connected to the first input of the adder, are introduced into the voltage converter at a time interval , the second input of which is connected to the key output, the output of the reference frequency generator is connected to the second input of the phase detector, the output of which is the output of the voltage converter al time.

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