CN102508509A - 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 modification method of electric current/freq converting circuit

Technical field

The present invention relates to a kind of digital modification method of electric current/freq converting circuit, can be used to improve the digital modification method of electric current/freq converting circuit constant multiplier temperature drift characteristic and asymmetry.

Background technology

Electric current/freq converting circuit is accomplished the conversion of the magnitude of current to the pulsed frequency amount, the size of output pulse frequency and input current big or small proportional, thus realization is to the digitizing of magnitude of current analog information.Every milliampere of corresponding output pulse frequency of input current is called the constant multiplier of electric current/freq converting circuit.Because the component parameter of change-over circuit has certain temperature drift characteristic, and positive and negative passage independence and have asymmetry, therefore, be necessary the constant multiplier temperature drift and the asymmetry of electric current/freq converting circuit are revised.

The constant multiplier temperature drift modification method that is used for electric current/freq converting circuit in the past is through three end adjustable current sources with responsive to temperature characteristic feedback constant current source electric current to be exported to realize the quantitative simulation hardware modifications; The constant multiplier asymmetry modification method that is used for electric current/freq converting circuit is through the sample resistance of positive-negative feedback constant current source being regulated the size of change feedback constant current, thereby the positive and negative asymmetry of correction constant multiplier.The resistance that is used to control three end adjustable current source output currents and feedback constant current size need pass through and calculate; 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 about 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: to the deficiency of prior art, a kind of digital modification method of electric current/freq converting circuit is provided.The present invention revises electric current/freq converting circuit, has solved oversize, the not high problem of correction precision of debugging complicacy, circuit board that electric current/freq converting circuit hardware simulation correction exists.

Technical solution of the present invention is:

A kind of digital modification method of electric current/freq converting circuit may further comprise the steps:

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

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

(3) utilize the once item, quadratic term and the biasing coefficient that obtain to concern about the secondary correction of operating ambient temperature to confirming electric current/freq converting circuit forward channel and negative sense passage;

(4) utilize the secondary correction relation of confirming that the output of electric current/freq converting circuit is revised in real time.

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

In said 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, once coefficient, quadratic term coefficient.

In said step (3), electric current/freq converting circuit forward channel and negative sense passage are shown below about the secondary 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 electric current/freq converting circuit forward channel and negative sense passage in the single sampling period;

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

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

The present invention compared with prior art has following advantage:

(1) the digital modification method that is used for the constant multiplier of electric current/freq converting circuit of the present invention; But when concrete the application, can utilize plate level FPGA (field programmable gate array) and a slice 1-wire temperature sensor of a slice programming program; Utilize the correction relation of confirming directly the numeral correction to be carried out in the output of electric current/freq converting circuit and reach constant multiplier correction purpose; Realize that simply, real-time is high.

(2) the digital modification method that is used for the constant multiplier of electric current/freq converting circuit of the present invention; Utilize the correction relation that obtains to revise; Thereby debugging devices such as a large amount of responsive to temperature current sources, precision resistor can have been abandoned; Significantly reduce the area and the quality of circuit board, helped miniaturization, the lighting of change-over circuit.

(3) the digital modification method that is used for the constant multiplier of electric current/freq converting circuit of the present invention can be realized the non-linear correction to constant multiplier, and than the linear correction technique of existing hardware simulation, it is higher to revise precision.

(4) the digital modification method that is used for the constant multiplier of electric current/freq converting circuit of the present invention, the calculating of corrected parameter is simpler, and it is more terse to revise step, has significantly improved production debugging efficient, helps the production mass.

Description of drawings

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

Embodiment

Just combine process flow diagram shown in Figure 1 below, this embodiment is done further introduction.

In electric current/freq converting circuit, be output as the pulse of Transistor-Transistor Logic level, low level is effective, and pulse width is about 4 μ s.Sampling period paired pulses with 5ms is counted.Suppose that electric current/freq converting circuit input current is 1mA, the count value in 200 sampling periods added up that accumulation result is the umber of pulse of 1s, just positive constant multiplier K ₊If input current is-1mA then to be 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 under 11 set environment temperature of-40 ℃ ,-30 ℃ ,-20 ℃ ,-10 ℃, 0 ℃, 10 ℃, 20 ℃, 30 ℃, 40 ℃, 50 ℃, 60 ℃, work respectively, record the positive and negative constant multiplier value K of electric current/freq converting circuit in above-mentioned environment respectively ₊, K _-And the actual working environment temperature T of electric current/freq converting circuit.

With the temperature T is independent variable, with constant multiplier K ₊, K _-Be dependent variable, obtain K respectively through least square fitting ₊, 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 the formula, A ₊, B ₁₊, B ₂₊, A _-, B _1-, B _2-, be respectively biasing, once 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 be accomplished 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 the formula, N ₀₊, N _0-Be respectively and in the single sampling period, revise the preceding forward channel 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 in the single sampling period.

The secondary correction relation that through type (4) and formula (5) are confirmed is compiled into program code, and the mode through program burn writing is solidificated in FPGA inside, forms fixing hardware logic, accomplishes correction work in real time.

In FPGA, at first to N ₀₊And N ₀₊Latch, obtain the actual working environment temperature T of electric current/freq converting circuit through temperature sensor, then according to set secondary correction relation to N ₀₊And N _0-Perform mathematical calculations, with revised count value N ₊, N _-Spread out of and give subsequent process circuit and carry out related application, accomplish numeral and revise.

Claims (5)

1. the digital modification method of an electric current/freq converting circuit is characterized in that may further comprise the steps:

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

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

(3) utilize the once item, quadratic term and the biasing coefficient that obtain to concern about the secondary correction of operating ambient temperature to confirming electric current/freq converting circuit forward channel and negative sense passage;

(4) utilize the secondary correction relation of confirming that the output of electric current/freq converting circuit is revised in real time.

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

3. the digital modification method of a kind of electric current/freq converting circuit according to claim 1 is characterized in that: in said 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 biasing, once coefficient, quadratic term coefficient.

4. the digital modification method of a kind of electric current/freq converting circuit according to claim 1; It is characterized in that: in said step (3), electric current/freq converting circuit forward channel and negative sense passage are shown below about the secondary 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 electric current/freq converting circuit forward channel and negative sense passage in the single sampling period;

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

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

5. the digital modification method of a kind of electric current/freq converting circuit according to claim 2, it 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.

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