KR100362155B1 - Method for adjusting Offset and Gain value of A/D converter - Google Patents

Abstract

A method for adjusting an offset and a gain value of an A / D converter for quickly adjusting an offset and a gain value of an A / D converter, and the offset and gain value adjusting method for an A / D converter using a fuzzy function rule. And setting the gain value to an initial value, and after setting the offset value to an initial value, an optimum offset value is obtained according to a result of comparing the minimum value of the current A / D sampled signal with the previous offset value through the A / D converter. Inferring, setting a gain value as an initial value, and inferring an optimum gain value according to a result of comparing the maximum value of the current A / D sampled signal with the previous gain value through an A / D converter, and inferring Determining whether the offset value has been sampled to the minimum value and ending the inference of the offset value or returning to inferring the optimal offset value, and sampling the inferred offset value to the minimum value. And determining whether the inferred gain value has been sampled to the maximum value and ending the inference of the gain value or returning to inferring the optimal gain value. The offset and gain values of the A / D converter can be adjusted, and the offset and gain values can be inferred quickly and accurately.

Description

How to adjust offset and gain value of A / D converter {Method for adjusting Offset and Gain value of A / D converter}

The present invention relates to an A / D converter, and more particularly, to a method of adjusting offset and gain values of an A / D converter.

Generally, various video devices such as TVs, monitors, projectors, etc. do not output analog video signals as they are, even though they receive analog video. Instead, they are sampled as digital signals through A / D converters, and then various images are processed. Output the signal.

Hereinafter, an offset and gain value adjusting apparatus of an A / D converter according to the prior art will be described with reference to the accompanying drawings.

1 is a block diagram illustrating a schematic configuration of an offset and gain value adjusting device of an A / D converter according to the prior art, and FIGS. 2A and 2B are inaccurately adjusted offset values in the A / D converter shown in FIG. 1. 3A and 3B are diagrams illustrating a case where a gain value is incorrectly adjusted in the A / D converter illustrated in FIG. 1.

As shown in FIG. 1, an offset and gain adjustment device of an A / D converter according to the related art includes a sampling unit 10 for digitally sampling an analog image signal input in accordance with a sampling clock, and the sampling unit 10. A digital image processing unit 20 for receiving an image sampled at 10 and performing image processing on the screen, and an image output unit displaying the digital image signal processed by the digital image processing unit 20 on a screen; It consists of 30.

Here, the sampling unit 10 is a clamp generator 11 for outputting the input analog video signal at a predetermined signal level, and the analog video signal of a predetermined level output from the clamp generator 11 to the sampling AD clock. An A / D converter 12 for sampling and generating a digital video signal, a PLL circuit section 14 for generating a sampling clock synchronized with the pixel frequency of the analog video signal and transmitting the same to the clamp generator 11; A clock generator 15 for generating an AD sampling clock from the sampling clock generated by the PLL circuit unit 14 and transmitting the AD sampling clock to the A / D converter 12 and a sampling clock generated by the clock generator 15. The data buffer 13 is configured to transmit the digital image signal output from the A / D converter 12 to the digital image processor 20.

The operation of the offset and gain value adjusting device of the conventional A / D converter configured as described above will be described in detail as follows.

First, the clamp generator 11 of the sampling unit 10 outputs an analog video signal input in accordance with a clock signal generated by the PLL circuit unit 14 at a predetermined signal level.

Subsequently, the A / D converter 12 of the sampling unit 10 adjusts the analog image signal output at the predetermined level from the clamp generator 11 to the AD sampling clock of the clock generator 15 to convert the analog image signal. Sampling generates a digital video signal.

In this case, when the A / D converter 12 samples, it is very important to accurately adjust offset and gain values, which are reference values for black and white, respectively.

Subsequently, if the offset value and the gain value of the A / D converter 12 are not set correctly, the black color may not be accurately represented as black, or the color of the dark portion may be all sampled as black, or the white portion may be darker than the maximum expressible brightness. Bright colors close to the white area appear saturated, resulting in inaccurate sampling.

That is, when the offset value is set lower than the reference value in the A / D converter 12, black is sampled as gray and appears as shown in FIG. 2A. When the offset value is set higher than the reference value, gray close to black becomes black. It is sampled and shown as shown in FIG. 2B.

Subsequently, when the gain value is set lower than the reference value in the A / D converter 12, white is sampled as light gray and appears as shown in FIG. 3A. When the gain value is set higher than the reference value, light gray close to white is obtained. It is sampled in white and appears as shown in FIG. 3B.

Here, the offset and gain values of the A / D converter 12 are inferred and set by a linear search or a binary search.

The offset and gain values of the A / D converter 12 are set for each of the three colors of R / G / B. Therefore, if the offset and gain values are not set correctly, the influence is applied to each of the three colors of R / G / B. Incorrect sampling results will result.

As a result, even if a digital video signal that is not accurately sampled is processed well, a large portion of the signal is processed with loss, resulting in severe deterioration of image quality.

The offset and gain value adjusting device of the A / D converter according to the related art described above has the following problems.

First, in order to adjust the offset and gain values of the A / D converter using the linear approach and the bipartite approach, the input / output characteristics of the linear and the bipartite approaches must be linear.

Second, it takes a lot of time to infer the correct offset and gain values of the A / D converter using the linear and binary approaches.

Therefore, the present invention has been made to solve the above problems, the offset and gain value of the A / D converter to be able to infer the accurate offset and gain value of the A / D converter more quickly and accurately using the fuzzy rule. The purpose is to provide a method of coordination.

1 is a block diagram showing a schematic configuration of a device for adjusting offset and gain values of an A / D converter according to the prior art;

2A and 2B illustrate a case where an offset value is incorrectly adjusted in the A / D converter illustrated in FIG. 1.

3A and 3B illustrate a case in which a gain value is incorrectly adjusted in the A / D converter shown in FIG. 1.

4 is a view illustrating a test pattern in an offset and gain value adjusting method of an A / D converter according to the present invention.

5A and 5B are diagrams showing the front and rear part purge water of the fuzzy function;

Figures 6a and 6b is a view showing the similarity and results of the electric gun in the fuzzy rule of the present invention

7a and 7b is a view showing the similarity and final correction value of the electric gun in the fuzzy rule of the present invention

8 is a flowchart illustrating a method of adjusting offset and gain values of an A / D converter according to the present invention.

9 is a flowchart illustrating an offset value adjusting method in an offset and gain value adjusting method of an A / D converter according to the present invention.

10 is a flowchart illustrating a method of automatically adjusting gain values in an offset and gain value adjusting method of an A / D converter according to the present invention.

The method for adjusting the offset and gain values of the A / D converter according to the present invention for achieving the above object, in the method for adjusting the offset and gain values of the A / D converter using a fuzzy function rule, the offset and gain values as initial values Setting the offset value and initializing the offset value, and inferring the optimum offset value according to a result of comparing the minimum value of the current A / D sampled signal with the previous offset value through an A / D converter, and gain After the initial value is set, inferring the optimum gain value according to the result of comparing the maximum value of the current A / D sampled signal with the previous gain value through the A / D converter, and inferring the offset value to the minimum value. Determining whether or not it has been sampled, ending the inference of the offset value, or returning to inferring the optimal offset value, and if the inferred offset value is sampled to the minimum value, inferred gain value Makin made to determine whether or not the maximum sampled value, including the step of returning to the step of shutting down or infer the optimum gain value is a gain value speculation has its features.

Hereinafter, an offset and gain value adjusting method of an A / D converter according to the present invention will be described with reference to the accompanying drawings.

4 is a view showing a test pattern in the method of adjusting the offset and gain values of the A / D converter according to the present invention, Figures 5a and 5b is a view showing the front and rear dry purge number of the purge function, Figure 6a and Figure 6b is a view showing the similarity and the result of the electric gun in the fuzzy rule of the present invention, Figures 7a and 7b is a view showing the similarity and the final correction value of the electric gun in the fuzzy rule of the present invention, Figure 8 is in accordance with the present invention 9 is a flowchart illustrating an offset and gain value adjusting method of the A / D converter, FIG. 9 is a flowchart illustrating an offset value adjusting method in the offset and gain value adjusting method of the A / D converter according to the present invention, and FIG. A flowchart illustrating a gain value adjusting method in an offset and gain value adjusting method of an A / D converter according to the present invention.

As shown in FIG. 8, in the method of adjusting the offset and gain values of the A / D converter according to the present invention, first, the offset and gain values are set to initial values (S100).

Subsequently, after setting the offset value to an initial value, an optimal offset value is inferred based on a result of comparing the minimum value of the current A / D sampled signal with the previous offset value through the A / D converter (not shown) (S200). ).

Here, the method of inferring the optimal offset value will be described in detail with reference to FIG. 9. After setting the offset value to an initial value (S210), the minimum value A / D sampled through the A / D converter (not shown) is described. It is detected (S211).

Subsequently, it is determined whether the detected minimum value is '0' (S212).

If the detected minimum value is not '0', a method of inferring an offset correction value to be adjusted currently from the A / D sampled minimum value and the offset correction value immediately before is explained through a fuzzy rule.

IF x _i is A _i THEN u _i is B _i

Where x _i represents the current A / D sampled minimum or maximum value, u _i represents the offset and gain correction values for the current input screen state, A _i is the overall fuzzy number of the fuzzy function, and B _i Is the fuzzy number with respect to the back dry portion correction value of the fuzzy function, the front dry portion is the regular portion before THEN below IF, and the rear dry portion represents the regular portion below THEN.

For example, a conceptual fuzzy function rule may be formed that 'if the sampled minimum value is' 0', the offset correction value is' 0 '.

Here, the control value to be inferred from the fuzzy function's backside may not always be '0' depending on the nature of most system configurations.

As a result, even in the example of the A / D converter, it is impossible to know what the offset value will be between the minimum value and the maximum value.

Therefore, instead of setting the target value to be used in the front part of the fuzzy function as the current output value, the error value, that is, the error value is used in the front part, and the rear part also uses the offset correction value instead of the offset itself. The number of can be reduced to one.

That is, the front key part does not use the control result value, but uses the current error value of the control result value from the final desired state, and the rear key part does not use the control value (offset or gain value) to be inferred as a specific value, but uses the control value. By setting the correction value, ie, the correction value (offset or gain correction value) of the control value to '0', a rule applicable to any control system can be made.

As a result, it is possible to create a fuzzy rule with only one rule without having to make several fuzzy rules according to the condition of the front part and the back part of the fuzzy function.

Subsequently, the integral key fuzzy number, A _i , defined in Equation 1 does not mean a value of a specific point, but a numerical value including a qualitative meaning expressed by an expression of 'A degree'. In the current system (A / D converter) example, which aims to obtain an accurate sampling value by correcting offset and gain values, as shown in FIG. 5A, 'A _min , A _max ' Similar value '.

In addition, the value to be controlled by the fuzzy function is not an offset or a gain value, but an offset correction value that makes an error of a sampling value with respect to a target sampling value for a test pattern '0', and this correction target value is '0'. 'to be.

That is, as illustrated in FIG. 5B, the target value may be interpreted as about a correction value between [U _min , U _max ] around 0 '.

Subsequently, how the comparison between the front and rear part purge water of the purge function and the distinct number obtained in the real system can be made, as shown in FIGS. 5A and 5B. It is the number of consecutive concepts defined around the number.

In this case, the fuzzy function of the corresponding fuzzy number may be a triangular shape, and may be defined in any desired shape such as an asymmetric triangle, a Gaussian function shape, a peak representing a center, and a maximum value of '1'.

In this case, a general fuzzy inference method will be described with reference to FIGS. 6A and 6B.

If the current input, x _i (current A / D sampled minimum or maximum value) defined in Equation 1 is x1, as shown in FIG. 6A, the total dry purge number of the corresponding fuzzy function for x1, ie, The similarity value can be calculated.

When the similarity value w is obtained, it can be deduced from the similarity value w how much the correction value of the fuzzy function post-drying part should be applied.

If there are many current inputs (current A / D sampled minimum or maximum values) of the fuzzy function unit, the similarity value is obtained by taking the lowest value among the similarity values (w) obtained from each fuzzy function or taking a multiplied value. Determine (w).

Then, as shown in FIG. 6A, the fuzzy function portion of the purge function is removed from the fuzzy function portion for the portion exceeding the similarity value w and takes the u value of the point corresponding to the center of gravity from the value of the remaining portion. Inferring the way.

Subsequently, several rules of different cases having different correction values for different input values must coexist, and the results of the rules are inferred as shown in FIG. 6B.

In addition, the proposed fuzzy inference method can infer different back-dry fuzzy values for values that show a difference in sign when the input value (A / D sampled minimum value or maximum value) of the fuzzy function front part is x1 and x2. The method of purging inferred faster and more accurately than the conventional center of gravity method will be described with reference to FIGS. 7A and 7B as follows.

First, in the general fuzzy rule, there is only one inference result obtained from one rule when the similarity values w are the same.

On the other hand, as shown in Figure 7a, for the case of having the same input range and the same correction range, even if a different input value, such as x1, x2 with only one fuzzy rule to enter the correction inferred without defining a separate rule By dividing the range into two parts, the final control (offset or gain) correction can be inferred under the conditions of the health division.

That is, assuming that x1 and x2 are inputs, the similarity values w for the corresponding inputs x1 and x2 may be calculated as shown in FIG. 7A.

Subsequently, a correction range, that is, [U _lower , U _upper ] of the back dry part purge value (correction value) with respect to the similarity value w is calculated as shown in FIG. 7A.

The direction to be corrected from the current correction value can be determined according to whether the current sampling error, that is, the difference between the current A / D sampled minimum value and the preset sampling reference value is positive or negative.

For example, in the case of offset, if the current sampling error is positive, the offset correction value should be corrected in the positive direction. If the current sampling error is negative, the offset correction value should be corrected in the negative direction.

Also, in the case of gain, if the current sampling error (current A / D sampled maximum value-the preset sampling reference value) is positive, the gain correction value should be corrected in the negative direction. It should be corrected in the positive direction.

In this case, as shown in FIG. 7B, the direction of the actual correction value may be determined from the correction range [U _lower , U _upper ] of the correction value, and the current correction value U (k) is the previous correction value U (k -1)) and the median of the boundary (U _lower or U _upper ) of the currently inferred correction interval.

As a result, if the detected minimum value is not '0', the total similarity value w of the fuzzy function with respect to the A / D sampled minimum value is calculated (S213).

Subsequently, the similarity value w of the front part is calculated, and the correction range to be applied to the fuzzy function rear part is calculated from the calculated similarity value w, as shown in FIG. 7A (S214).

In operation S215, it is determined whether a minimum A / D sampled minimum value exceeds a preset sampling reference value.

As a result of the determination (S215), if the current A / D sampled minimum value exceeds the preset sampling reference value, the offset correction value U (k) is It is inferred to (S216), and returns to the step of setting the offset value to the initial value (S210) to set the offset value to the currently inferred offset correction value (U (k)), and then performs the step.

On the other hand, if the determination result (S215), the current A / D sampled minimum value does not exceed the preset sampling reference value, the offset correction value (U (k)) is It is inferred to (S217), and returns to the step of setting the offset value to the initial value (S210) to set the offset value to the currently inferred offset correction value (U (k)), and performs the step.

Subsequently, when the A / D sampled minimum value is '0', it is determined whether the current offset correction value is the same as the previous offset correction value (S218).

As a result of the determination (S218), if the current offset correction value is the same as the previous offset correction value, the adjustment of the offset value is terminated (S220).

On the other hand, if the determination result (S218), the current offset correction value and the previous offset correction value is not the same, by reducing the correction range of the current offset correction value (S219), and setting the offset value to the initial value (S210) Return and perform the step.

In addition, after setting the gain value to an initial value, an optimal gain value is inferred based on a result of comparing the maximum value of the current A / D sampled signal and the previous gain value through the A / D converter (not shown) (S300). ).

A method of inferring the optimal gain value will now be described in detail with reference to FIG. 10.

First, the gain value is set to an initial value (S310).

Subsequently, the A / D sampled maximum value is detected (S311), and it is determined whether the detected maximum value is the maximum value (S312).

As a result of the determination (S312), if the detected maximum value is not the maximum value, the similarity value (w) of the fuzzy function whole unit by the A / D sampled maximum value is calculated (S313), and the fuzzy value is calculated from the similarity value (w). The correction range to be applied to the function back construction unit is calculated (S314).

Here, the method of calculating the correction range of the gain correction value from the similarity value w and the similarity value w of the fuzzy function whole unit is the same as the method of calculating the correction range of the offset correction value.

Subsequently, it is determined whether the maximum A / D sampled maximum value exceeds a preset sampling reference value (S315).

As a result of the determination (S315), if the current A / D sampled maximum value does not exceed the preset sampling reference value, the gain correction value U (k) is It is inferred to (S316), and returns to the step of setting the gain value to the initial value (S310) to set the gain value to the currently inferred gain correction value (U (k)), and performs the step.

On the other hand, if the determination result (S315), the current A / D sampled maximum value exceeds the preset sampling reference value, the gain correction value (U (k)) is It is inferred to (S317), and returns to the step of setting the gain value to the initial value (S310) to set the gain value to the currently inferred gain correction value (U (k)), and performs the step.

Subsequently, in the determination result (S312), if the detected maximum value is the maximum value, it is determined whether the current gain correction value is the same as the previous gain correction value (S318).

As a result of the determination (S318), if the current gain correction value is equal to the previous gain correction value, the adjustment of the gain value is terminated (S320). If the current gain correction value is not equal to the previous gain correction value, the current gain is not the same. The correction range of the correction value is reduced (S319), and the process returns to the step of setting the gain value to an initial value (S310) to perform the corresponding step.

Here, when the inference of the offset and gain values is completed, it is determined whether the inferred offset value has been sampled to the minimum value (S400).

As a result of the determination (S400), if the inferred offset value is not sampled to the minimum value, the process returns to the step of inferring the optimal offset value (S200) and performs the corresponding step.

On the other hand, if the inferred offset value is sampled to the minimum value (S400), it is determined whether the inferred gain value is sampled to the maximum value (S500).

As a result of the determination (S500), if the inferred gain value is sampled to the maximum value, the corresponding offset and gain value inference is terminated, and if the inferred gain value is not sampled to the maximum value, the optimal gain value is inferred. Returning to step S300 to perform the corresponding step.

As described above, the offset and gain value adjusting method of the A / D converter according to the present invention can infer the offset and gain values of the A / D converter more quickly and accurately by using a fuzzy rule.

As described above, the method of adjusting the offset and gain values of the A / D converter according to the present invention has the following effects.

First, fuzzy rules allow offset and gain values to be adjusted for nonlinear inputs and outputs.

Second, the fuzzy rule first limits the correction range of the offset and gain correction values, allowing for faster and more accurate inference of the offset and gain values.

Claims (7)

In the method of adjusting the offset and gain values of the A / D converter using the fuzzy function rule, Setting the offset and gain values to initial values; Setting the offset value as an initial value and inferring an optimal offset value through the A / D converter according to a result of comparing the minimum value of the current A / D sampled signal with the previous offset value; Setting the gain value to an initial value, and inferring an optimum gain value according to a result of comparing a maximum value of a current A / D sampled signal with a previous gain value through the A / D converter; Determining whether the inferred offset value has been sampled to a minimum value and ending the inference of the offset value or returning to inferring the optimal offset value; And, If the inferred offset value is sampled to a minimum value, determining whether the inferred gain value is sampled to a maximum value and ending the inference of the gain value or returning to inferring the optimal gain value. A / D converter offset and gain value adjusting method characterized in that the. The method of claim 1, Inferring the optimum offset value according to the result of comparing the minimum value of the current A / D sampled signal and the previous offset value through the A / D converter Detecting the minimum A / D sampled value through the A / D converter after setting the offset value to an initial value; If the detected minimum value is not '0', the similarity value (w) of the fuzzy function front part is calculated by the A / D sampled minimum value, and is applied to the back-drying part of the corresponding fuzzy function from the calculated similarity value (w). Calculating a correction range of the offset correction value; Inferring an offset correction value according to whether the current A / D sampled minimum value exceeds a preset sampling reference value and returning to setting the offset value as an initial value; If the detected minimum value is '0', determining whether the current offset correction value and the previous offset correction value are the same; If the current offset correction value and the previous offset correction value is not the same, the step of reducing the correction range of the current offset correction value to return to the step of setting the offset value to the initial value A / characterized in that it comprises a How to adjust offset and gain value of D converter. The method of claim 2, Determining whether the current A / D sampled minimum value exceeds a preset sampling reference value If the current A / D sampled minimum value exceeds a preset sampling reference value, the offset correction value U (k) is changed. Reasoning with If the current A / D sampled minimum value does not exceed a preset sampling reference value, the offset correction value U (k) is changed. And adjusting the offset and gain values of the A / D converter. The method of claim 3, wherein The U (k-1) is an offset correction value immediately before the offset correction value U (k), and the U _upper and U _lower are boundaries of the correction range. Way. The method of claim 1, Inferring the optimum gain value according to the result of comparing the maximum value of the current A / D sampled signal and the previous gain value through the A / D converter Detecting the maximum A / D sampled value through the A / D converter after setting the gain value to an initial value; If the detected maximum value is not the maximum value, the similarity value (w) of the fuzzy function front part of the A / D sampled maximum value is calculated, and the gain correction applied to the back-drying part of the fuzzy function from the calculated similarity value (w) Calculating a correction range of the value; Inferring the gain correction value based on whether the current A / D sampled maximum value exceeds a preset sampling reference value and returning to initial setting the gain value; If the detected maximum value is a maximum value, determining whether a current gain correction value and a previous gain correction value are the same; If the current gain correction value and the previous gain correction value are not the same, reducing the correction range of the current gain correction value and returning to setting the gain value to an initial value. How to adjust the offset and gain values of the / D converter. The method of claim 5, The step of determining whether the current A / D sampled maximum value exceeds a preset sampling reference value If the current A / D sampled maximum value exceeds a preset sampling reference value, the gain correction value is changed. Reasoning with If the current A / D sampled maximum value does not exceed a preset sampling reference value, the gain correction value is changed. And adjusting the offset and gain values of the A / D converter. The method of claim 6, U (k-1) is a gain correction value immediately before gain correction value U (k), and U _upper and U _lower are offset ranges of the gain correction value, How to adjust the gain value.