CN102508509B - Digital correction method for current/frequency conversion circuit - Google Patents

Abstract

The invention discloses a digital correction method for a current/frequency conversion circuit. The digital correction method includes a first step of measuring and acquiring positive and negative scale factors and the temperature of a working environment of the current/frequency conversion circuit; a second step of determining second-order relationship of the positive and negative scale factors and the temperature of the working environment; a third step of determining secondary correction relationship of a forward channel and a reverse channel of the conversion circuit relative to the temperature of the working environment according to the second-order relationship of the positive and negative scale factors and the temperature of the working environment; and a fourth step of correcting output of the conversion circuit by the aid of the correction relationship. The digital correction method for the current/frequency conversion circuit solves problems that a hardware analog correction method for a current/frequency conversion circuit is complicated in debugging, a circuit board is overlarge in size, and correction precision is low.

Description

A kind of digital correction method of current/frequency conversion circuit

Technical field

The present invention relates to a kind of digital correction method of current/frequency conversion circuit, can be for improving the digital correction method of current/frequency conversion circuit constant multiplier temperature drift characteristic and asymmetry.

Background technology

Current/frequency conversion circuit completes the magnitude of current to the conversion of pulsed frequency amount, and the size of output pulse frequency and the size of input current are proportional, thereby realizes the digitizing to magnitude of current analog information.Every milliampere of output pulse frequency corresponding to input current is called the constant multiplier of current/frequency conversion circuit.Because the component parameter of change-over circuit has certain temperature drift characteristic, and positive and negative passage independence and there is asymmetry, therefore, be necessary constant multiplier temperature drift and the asymmetry of current/frequency conversion circuit to revise.

The constant multiplier temperature drift modification method for current/frequency conversion circuit is in the past that to feedback constant current source electric current, output realizes quantitative simulation hardware modifications by having three end adjustable current sources of responsive to temperature characteristic; For the constant multiplier asymmetry modification method of current/frequency conversion circuit, be by the sample resistance of positive-negative feedback constant current source is regulated, change the size of feedback constant current, thereby revise the positive and negative asymmetry of constant multiplier.Need to be through calculating for controlling the resistance of three end adjustable current source output currents and feedback constant current size, computing method and testing and measuring technology are complicated, revise precision and be difficult to guarantee, and correction circuit and device take the area of printed circuit board approximately 1/5, be unfavorable for the miniaturization of change-over circuit.

Summary of the invention

Technology of the present invention is dealt with problems and is: for the deficiencies in the prior art, provide a kind of digital correction method of current/frequency conversion circuit.The present invention revises current/frequency conversion circuit, has solved that the debugging that current/frequency conversion circuit hardware simulation correction exists is complicated, circuit board is oversize, revise the not high problem of precision.

Technical solution of the present invention is:

A digital correction method for current/frequency conversion circuit, comprises the following steps:

(1) current/frequency conversion circuit is put into temperature test chamber and work, measure and obtain positive and negative constant multiplier and the operating ambient temperature of current/frequency conversion circuit;

(2), according to the second order relation of positive and negative constant multiplier and operating ambient temperature, determine that positive and negative constant multiplier is about the once item in operating ambient temperature second order expression formula, quadratic term and biasing coefficient;

(3) once item, quadratic term and the biasing coefficient that utilization obtains is to determining that current/frequency conversion circuit forward channel and negative sense passage are about the second-order correction relation of operating ambient temperature;

(4) utilize definite second-order correction relation to revise in real time the output of current/frequency conversion circuit.

In described step (1), according to the actual work temperature environment of current/frequency conversion circuit, temperature test chamber is regulated; And positive and negative constant multiplier and operating ambient temperature under a plurality of actual work temperature environment are measured.Positive and negative constant multiplier and the operating ambient temperature chosen under at least 3 actual work temperature environment are measured.

In described step (2), positive and negative constant multiplier K ₊, K _-as follows about operating ambient temperature T second order expression formula:

K ₊＝A ₊+B ₁₊×T+B ₂₊×T ²

K _-＝A _-+B _1-×T+B _2-×T ²

Wherein, A ₊, B ₁₊, B ₂₊, A _-, B _1-, B _2-, be respectively biasing, Monomial coefficient, quadratic term coefficient.

In described step (3), current/frequency conversion circuit forward channel and negative sense passage are shown below about the second-order correction relation of operating ambient temperature:

$N_{+}=N_{0+}\×(1-\frac{T}{A_{+}}\×(B_{1+}+B_{2+}\×T))$

$N_{-}=K_0\×N_{0-}\×(1-\frac{T}{A_{-}}\×(B_{1-}+B_{2-}\×T))$

Wherein, K ₀=K ₊/ K _-;

N ₀₊and N _0-be respectively the counted number of pulses of current/frequency conversion circuit forward channel and negative sense passage within the single sampling period;

N ₊, N _-be respectively the counted number of pulses of revised forward channel and negative sense passage within the single sampling period;

A ₊, B ₁₊, B ₂₊, A _-, B _1-, B _2-, positive and negative constant multiplier is about the biasing in operating ambient temperature second order expression formula, Monomial coefficient, quadratic term coefficient respectively.

The present invention compared with prior art tool has the following advantages:

(1) digital correction method of the constant multiplier for current/frequency conversion circuit of the present invention, when concrete application, can utilize plate level FPGA (field programmable gate array) and a slice 1-wire temperature sensor that a slice can programming program, utilize definite correction relation directly the output of current/frequency conversion circuit to be carried out to numeral correction and reach constant multiplier correction object, realize simply, real-time is high.

(2) digital correction method of the constant multiplier for current/frequency conversion circuit of the present invention, utilize the correction relation obtaining to revise, thereby the debugging devices such as a large amount of responsive to temperature current sources, precision resistor can have been abandoned, significantly reduce area and the quality of circuit board, be conducive to miniaturization, the lighting of change-over circuit.

(3) digital correction method of the constant multiplier for current/frequency conversion circuit of the present invention, can realize the non-linear correction to constant multiplier, than existing hardware simulation linear revise technology, revises precision higher.

(4) digital correction method of the constant multiplier for current/frequency conversion circuit of the present invention, the calculating of corrected parameter is simpler, revises step more terse, has significantly improved production debugging efficiency, is conducive to production mass.

Accompanying drawing explanation

Fig. 1 is process flow diagram of the present invention.

Embodiment

Below just in conjunction with the process flow diagram shown in Fig. 1, this embodiment is described further.

In current/frequency conversion circuit, be output as the pulse of Transistor-Transistor Logic level, Low level effective, pulse width is about 4 μ s.Sampling period paired pulses with 5ms is counted.Suppose that current/frequency conversion circuit input current is 1mA, the count value in 200 sampling periods is added up, accumulation result is the umber of pulse of 1s, namely positive constant multiplier K ₊; If input current is-1mA, is negative constant multiplier K _-.

Change-over circuit is put into temperature test chamber, actual work temperature environment (40 ℃ to 60 ℃) with change-over circuit described in the present embodiment, make change-over circuit at 11 set environment temperature of-40 ℃ ,-30 ℃ ,-20 ℃ ,-10 ℃, 0 ℃, 10 ℃, 20 ℃, 30 ℃, 40 ℃, 50 ℃, 60 ℃, work respectively, record respectively the positive and negative constant multiplier value K of current/frequency conversion circuit in above-mentioned environment ₊, K _-actual working environment temperature T with current/frequency conversion circuit.

Take temperature T as independent variable, with constant multiplier K ₊, K _-for dependent variable, by least square fitting, obtain respectively K ₊, K _-second order polynomial relation with T:

K ₊＝A ₊+B ₁₊×T+B ₂₊×T ² (1)

K _-＝A _-+B _1-×T+B _2-×T ² (2)

In formula, A ₊, B ₁₊, B ₂₊, A _-, B _1-, B _2-, be respectively biasing, Monomial coefficient, quadratic term coefficient.Obtain K simultaneously ₊with K _-scale-up factor

K ₀＝K ₊/K _- (3)

Formula (1) and formula (2) are the temperature model of positive and negative constant multiplier, and formula (3) is the model of positive and negative constant multiplier asymmetry.According to above model, through type (4), formula (5) can complete numeral and revise.

$N_{+}=N_{0+}\×(1-\frac{T}{A_{+}}\×(B_{1+}+B_{2+}\×T))---\left(4\right)$

$N_{-}=K_0\×N_{0-}\×(1-\frac{T}{A_{-}}\×(B_{1-}+B_{2-}\×T))---\left(5\right)$

In formula, N ₀₊, N _0-be respectively within the single sampling period forward channel before revising and the counted number of pulses of negative sense passage, N ₊, N _-be respectively the counted number of pulses of revised forward channel and negative sense passage within the single sampling period.

Through type (4) and the definite second-order correction relation of formula (5) are compiled into program code, and the mode by program burn writing is solidificated in FPGA inside, forms fixing hardware logic, completes in real time correction work.

In FPGA, first to N ₀₊and N ₀₊latch, by temperature sensor, obtain the actual working environment temperature T of current/frequency conversion circuit, then according to set second-order correction relation to N ₀₊and N _0-perform mathematical calculations, by revised count value N ₊, N _-spread out of and give subsequent process circuit and carry out related application, complete numeral and revise.

Claims (4)

1. a digital correction method for current/frequency conversion circuit, is characterized in that comprising the following steps:

(1) current/frequency conversion circuit is put into temperature test chamber and work, measure and obtain positive and negative constant multiplier and the operating ambient temperature of current/frequency conversion circuit;

(2), according to the second order relation of positive and negative constant multiplier and operating ambient temperature, determine that positive and negative constant multiplier is about the once item in operating ambient temperature second order expression formula, quadratic term and biasing coefficient;

(3) once item, quadratic term and the biasing parameter identification current/frequency conversion circuit forward channel that utilization obtains and negative sense passage are about the second-order correction relation of operating ambient temperature;

Current/frequency conversion circuit forward channel and negative sense passage are shown below about the second-order correction relation of operating ambient temperature:

$N_{+}=N_{0+}\×(1-\frac{T}{A_{+}}\×(B_{1+}+B_{2+}\×T))$

$N_{-}=K_0\×N_{0-}\×(1-\frac{T}{A_{-}}\×(B_{1-}+B_{2-}\×T))$

Wherein, K ₀=K ₊/ K _-;

K ₊, K _-be respectively positive and negative constant multiplier;

N ₀₊and N _0-be respectively the counted number of pulses of current/frequency conversion circuit forward channel and negative sense passage within the single sampling period;

N ₊, N _-be respectively the counted number of pulses of revised forward channel and negative sense passage within the single sampling period;

A ₊, B ₁₊, B ₂₊, A _-, B _1-, B _2-, be respectively positive and negative constant multiplier about the biasing in operating ambient temperature second order expression formula, Monomial coefficient, quadratic term coefficient;

(4) utilize definite second-order correction relation to revise in real time the output of current/frequency conversion circuit.

2. the digital correction method of a kind of current/frequency conversion circuit according to claim 1, is characterized in that: in described step (1), according to the actual work temperature environment of current/frequency conversion circuit, temperature test chamber is regulated; And positive and negative constant multiplier and operating ambient temperature under a plurality of actual work temperature environment are measured.

3. the digital correction method of a kind of current/frequency conversion circuit according to claim 1, is characterized in that: in described step (2), and positive and negative constant multiplier K ₊, K _-as follows about operating ambient temperature T second order expression formula:

K ₊=A ₊+B ₁₊×T+B ₂₊×T ²

K _-=A _-+B _1-×T+B _2-×T ²

Wherein, A ₊, B ₁₊, B ₂₊, A _-, B _1-, B ₂-, be respectively positive and negative constant multiplier about the biasing in operating ambient temperature second order expression formula, Monomial coefficient, quadratic term coefficient.

4. the digital correction method of a kind of current/frequency conversion circuit according to claim 2, is characterized in that: positive and negative constant multiplier and the operating ambient temperature chosen under at least 3 actual work temperature environment are measured.