JPH087607B2 - Power supply calibration method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a calibration method of a power supply device that outputs an analog signal corresponding to a digital value.

[Prior Art] Conventionally, there is a test device for testing the characteristics of an analog circuit with the assistance of a computer. This device applies an analog test voltage (or current) to the analog circuit that is the circuit under test, measures the output voltage (or current) at that time, and tests the characteristics of the analog circuit from the relationship of the input / output signals. It is a thing. In this case, as a device for measuring the output of the analog signal and the analog output signal of the circuit under test, a device usually called a measurement unit is used. The measuring unit is connected to a host computer and has functions such as outputting an analog voltage and measuring an output voltage from the device under test according to a test program executed by the computer. In addition, in order to simplify the description, a case of voltage output and voltage measurement will be described as an example.

The analog voltage applied to the circuit under test is output from the voltage output card of the measurement unit. This voltage output card is a power supply consisting of a part that generates a control voltage and a voltage output circuit [usually called an automatic voltage regulator (AVR)] that is configured to output an analog voltage corresponding to this control voltage. Built-in device.

[Problems to be Solved by the Invention] In the conventional AVR for such a measuring card, the ratio of the output voltage of the AVR to the control voltage is adjusted by hardware at some points in the full scale and adjusted. There is.

However, when the AVR output voltage does not change linearly with respect to the control voltage as shown in FIG. 4, an output error occurs. That is, in FIG. 4, the solid line represents the AVR output voltage y with respect to the actual control voltage x, and the dotted line represents the ideal control voltage x vs. AVR output voltage y. In this case, when the control voltage is x ₁ ,
The actual AVR output voltage is y ₁ , the ideal AVR output voltage is y ₀ , and the error is (y ₀ −y ₁ ). As described above, when the AVR output voltage does not change linearly, the conventional adjustment method has a problem that an output error occurs.

The present invention has been made in view of these points.
An object of the present invention is to provide a calibration method for performing calibration so that a control voltage output with a small error can be obtained even when the relationship between the control voltage of R and the output voltage is not linear (relation of a linear expression).

[Means for Solving Problems] In order to achieve such an object, according to the present invention, when a control voltage is applied to a voltage output circuit, an analog voltage corresponding to the control voltage is output from the voltage output circuit. In the power supply device configured as described above, the control voltage is applied, the analog output voltage value of the voltage output circuit at that time is read, the difference between the output voltage value and the target voltage value is determined, and the target voltage value is finally determined. It is characterized in that the control voltage is calibrated in accordance with the following procedure by providing means having a function of approximating the relation between the control voltage in the vicinity and the analog output voltage of the voltage output circuit by a linear expression.

When a target value y ₀ is obtained in a predetermined linear expression y = ax + b, x value x ₁ x ₁ = (y ₀ −b) / a is given as a control voltage to the voltage output circuit, and measured at that time. The step of obtaining the difference | y ₀ −y ₁ | of the actual output voltage y ₁ with respect to the target value y ₀ .

If the difference is equal to or less than the predetermined maximum error and exceeds the predetermined setting error, the point p ₁ obtained in the step is
In the equation y−y ₁ = a (x−x ₁ ) of a straight line passing through (x ₁ , y ₁ ) and having a slope a, the target value y ₀ can be obtained x value x ₂ x ₂ = (y ₀ −y ₁ ) / a−x ₁ is given to the voltage output circuit as a new control voltage,
The step of obtaining the difference | y ₀ −y ₂ | of the actual output voltage y ₂ measured at that time with respect to the target value y ₀ .

If the difference is equal to or less than the predetermined maximum error and exceeds the predetermined setting error, the point p ₁ obtained in the step is
In the equation y−y ₁ = (x ₂ −x ₁ ) (x−x ₁ ) / (y ₂ −y ₁ ) of the straight line passing through (x ₁ , y ₁ ) and p ₂ (x ₂ , y ₂ ), The target value y ₀ is obtained x value x ₃ x ₃ = (y ₀ −y ₁ ) (x ₂ −x ₁ ) / (y ₂ −y ₁ ) + x ₁ is given to the voltage output circuit as a new control voltage. ,
The step of obtaining the difference | y ₀ −y ₃ | of the actual output voltage y ₃ measured at that time with respect to the target value y ₀ .

If the error | y ₀ −y ₃ | is less than or equal to the maximum error and less than or equal to the set accuracy, the slope a ′ and the intercept b ′ obtained from the linear equation assumed in the above step are used as the coefficients of the final approximate linear equation and The process of saving as a constant.

The new slope a ′ in this case is a ′ = (x ₂ −x ₁ ) / (y ₂ −y ₁ ), and the new intercept b ′ is b ′ = y ₁ − (x ₂ −x ₁ ) × _{It is 1} / (y ₂ −y ₁ ).

In each of the above steps, if the difference is less than the set accuracy,
The process immediately shifts to the above process, and in each of the above processes, the calibration operation is stopped both when the difference exceeds the maximum error and when the difference obtained in the above process is larger than the set error.

[Embodiment] FIG. 1 is a principle flow of the calibration method of the present invention. In the present invention, in the vicinity of the normal AVR output voltage (hereinafter referred to as the target output voltage) in which the error is within the specified allowable range,
Apply the control voltage and measure the output voltage of the AVR at that time (hereinafter this operation is called set measure).
Then, the difference (absolute error) between the measured output voltage and the target output voltage is obtained.

Such a set / measure operation is performed up to three times to obtain the control voltage corresponding to the target output voltage.

 The procedure of the method of the present invention will be described in detail below.

First, it is assumed that the control voltage x and the output voltage y have a relationship of y = ax + b (1). Therefore, in the above equation (1), the value x of x ₁ x ₁ = (y ₀ −b) / a when y = y ₀ is applied to the AVR as a control voltage, and the output voltage at that time is measured. The measured output voltage is y ₁ .

It is determined whether the difference | y ₀ −y ₁ | between the target output voltage y ₀ and the measured voltage y ₁ is less than or equal to the specified maximum error. The maximum error is determined by the system, but it is a fairly large error.

If the error is less than or equal to the maximum error, it is further determined whether or not the difference is less than or equal to the setting accuracy (so-called allowable error).

If the set accuracy is exceeded, then perform the second AVR set measure.

The control voltage x _{2 at} this time is determined as follows. As shown in FIG. 2, a straight line having a slope of a through the point P ₁ (x ₁ , y ₁ ) in the _first set measure is y−y ₁ = a (x−x ₁ ).・ It is (2). Therefore, in the formula (2), x when y = y ₀
The value x ₂ of x is x ₂ = (y ₀ −y ₁ ) / a−x ₁ , and this is the control voltage for the second set measure.

The output voltage when this control voltage x ₂ is given is
Suppose it was y ₂ .

Therefore, it is determined whether the error | y ₀ −y ₂ | is less than or equal to the maximum error.

If the above error is less than or equal to the maximum error, then it is determined whether or not the error is less than or equal to the setting accuracy.

If the above error exceeds the set accuracy, then perform the third AVR set measure.

The control voltage x _{3 at} this time is determined as follows. As shown in FIG. 2, the measurement points P ₁ (x ₁ , y ₁ ) and P _{2 in the first} and _second set measures were set.
The formula of a straight line passing through (x ₂ , y ₂ ) is y−y ₁ = (x ₂ −x ₁ ) · (x−x ₁ / (y ₂ −y ₁ ) ...
(3) Therefore, in the equation (3), x when y = y ₀
The value of x ₃ is x ₃ = (y ₀ −y ₁ ) (x ₂ −x ₁ ) / (y ₂ −y ₁ ) + x ₁ , and this is the control voltage for the third set measure. .

The output voltage when this control voltage x ₃ is given is
Suppose it was y ₃ .

Determine whether the error | y ₀ −y ₃ | is less than or equal to the maximum error.

If the above error is less than or equal to the maximum error, then it is determined whether or not the error is less than or equal to the setting accuracy.

If the error is equal to or less than the set accuracy, a new slope a ′ and intercept b ′ are obtained from equation (3) and stored, and the calibration operation is completed.

New slope a _{'is, a' = (x 2 -x} 1) / (y 2 -y 1) new intercept b _{'is, b' = y 1 - (} x 2 -x 1) · x 1 / ( y ₂ −y ₁ ).

In each of the maximum error determinations, if the error exceeds the maximum error and if the error in the setting accuracy determination performed after the third set measure is larger than the setting accuracy, the AVR setting is stopped.

On the other hand, if the error in each setting accuracy determination before the third set measure is equal to or less than the setting accuracy, the process immediately shifts to the above.

In this way, a new coefficient a'and a constant b'are obtained, and when setting y ₀ thereafter, x is obtained from the equation y = a'x + b 'and set as the control voltage.

As described above, the control voltage when obtaining the output voltage y _{0 of the} AVR can be calibrated. The control voltage can be obtained for each of the other output voltages by the above method.

FIG. 3 is a block diagram showing an embodiment of an apparatus for carrying out the method of the present invention. In the figure, 1 is an analog circuit under test, 2 is an AVR, 3 is a controller, 4 is a digital / analog converter (hereinafter referred to as D / A converter), 5 is a switch, and 6 is an analog / digital converter (hereinafter referred to as A / A converter). It is called D converter).

The controller 3 has a function of executing the set-measure operation, generating a control voltage, reading a measured value, and determining the magnitude of the error.

The controller 3 gives each of the control voltages x ₁ , x ₂ , x ₃ to the D / A converter 4 as a digital value. The D / A converter 4 converts this into an analog signal and inputs it to the AVR 2. The output voltages y ₁ , y ₂ , y ₃ of the AVR are applied to the analog circuit under test 1,
This output voltage is led to the A / D converter 6 through the switch 5 which is on / off controlled by the controller 3, digitized here, and then input to the controller 3.

In such a configuration, the controller 5 controls the switch 5 to be turned on to enter the calibration mode, and then the first
The set measure and the error are determined according to the flow shown in the figure, and finally an approximate linear expression near the output voltage y ₀ is obtained.

When the calibration mode ends, the switch 5 is turned off under the control of the controller 3.

[Effects of the Invention] As described in detail above, according to the present invention, when determining the second and third AVR control voltages, the first measured data and the first and second measured data, respectively. Since it is calculated based on the actual measurement data of
There is little deviation from the AVR setting target value, and it is possible to quickly converge to the target value.

Further, since the inclination a ′ and the cutting edge b ′ obtained by performing the calibration once are saved and can be used in the next calibration, the target value is converged with a smaller number of times from the next time. be able to. In normal test equipment, the output voltage of the AVR is often constant at the rated input voltage of the analog circuit under test even if the test item changes, and a ', b'approximated in the vicinity are used. Since it converges quickly, the practical effect is great.

[Brief description of drawings]

FIG. 1 is a flow chart of the principle of the calibration method of the present invention, FIG. 2 is an explanatory diagram showing the relationship between the control voltage and the AVR output voltage for explaining the principle of the calibration method of the present invention, and FIG. 3 is the method of the present invention. FIG. 4 is a configuration diagram showing an embodiment of an apparatus for carrying out the present invention, and FIG. 4 is a characteristic diagram showing a relationship between a control voltage and an AVR output voltage. 1 ... Analog circuit under test, 2 ... AVR, 3 ... Controller, 4 ... D / A converter, 5 ... Switch, 6 ... A / D converter.

Claims (1)

[Claims] 1. A power supply output device configured such that when a control voltage is applied to a voltage output circuit, an analog voltage corresponding to the control voltage is output from the voltage output circuit. The analog output voltage value of the voltage output circuit is read, the difference between the output voltage value and the target voltage value is judged, and finally the relationship between the control voltage near the target voltage value and the analog output voltage of the voltage output circuit is expressed by a linear expression. A method of calibrating a power supply device, characterized in that the control voltage is calibrated in accordance with the following procedure, which is provided with a means having a function approximating to. When a target value y ₀ is obtained in a predetermined linear expression y = ax + b, x value x ₁ x ₁ = (y ₀ −b) / a is given as a control voltage to the voltage output circuit, and measured at that time. The step of obtaining the difference | y ₀ −y ₁ | of the actual output voltage y ₁ with respect to the target value y ₀ . If the difference is equal to or less than the predetermined maximum error and exceeds the predetermined setting error, the point p ₁ obtained in the step is
In the equation y−y ₁ = a (x−x ₁ ) of a straight line passing through (x ₁ , y ₁ ) and having a slope a, the target value y ₀ can be obtained x value x ₂ x ₂ = (y ₀ −y ₁ ) / a−x ₁ is given to the voltage output circuit as a new control voltage,
The step of obtaining the difference | y ₀ −y ₂ | of the actual output voltage y ₂ measured at that time with respect to the target value y ₀ . If the difference is equal to or less than the predetermined maximum error and exceeds the predetermined setting error, the point p ₁ obtained in the step is
In the equation y−y ₁ = (x ₂ −x ₁ ) (x−x ₁ ) / (y ₂ −y ₁ ) of the straight line passing through (x ₁ , y ₁ ) and p ₂ (x ₂ , y ₂ ), The target value y ₀ is obtained x value x ₃ x ₃ = (y ₀ −y ₁ ) (x ₂ −x ₁ ) / (y ₂ −y ₁ ) + x ₁ is given to the voltage output circuit as a new control voltage. ,
The step of obtaining the difference | y ₀ −y ₃ | of the actual output voltage y ₃ measured at that time with respect to the target value y ₀ . If the error | y ₀ −y ₃ | is less than or equal to the maximum error and less than or equal to the set accuracy, the slope a ′ and the intercept b ′ obtained from the linear equation assumed in the above step are used as the coefficients of the final approximate linear equation and The process of saving as a constant. The new slope a ′ in this case is a ′ = (x ₂ −x ₁ ) / (y ₂ −y ₁ ), and the new intercept b ′ is b ′ = y ₁ − (x ₂ −x ₁ ) × _{It is 1} / (y ₂ −y ₁ ). In each of the above steps, if the difference is less than the set accuracy,
The process immediately shifts to the above process, and in each of the above processes, the calibration operation is stopped both when the difference exceeds the maximum error and when the difference obtained in the above process is larger than the set error.