KR20210034848A - Hybrid-Dimming Control apparatus for Machine Vision LED Light - Google Patents

Abstract

The present invention relates to a hybrid-dimming control device for a machine vision LED light. Provided is the hybrid-dimming control device for the machine vision LED light, wherein when the LED light for machine vision is controlled, an output current and output time can be finely adjusted and, when the hybrid method is applied, high output can be generated in a short period of time, so cumulative heat is hardly generated. The hybrid-dimming control device is effective for image extraction because the output current and on-time can be varied. Since the light output of the LED light for machine vision can be varied, the hybrid-dimming control device has the flexibility to provide an optimal environment for the characteristics of a detection sample.

Description

Hybrid-Dimming Control apparatus for Machine Vision LED Light}

The present invention relates to a hybrid dimming control device capable of controlling an LED lighting device for machine vision with high light intensity, high precision, and high efficiency by applying a hybrid-dimming technology that combines a current control method and a strobe method. will be.

Recently, the government has proposed "low carbon green growth" as a future national vision, and has raised the proportion of the LED lighting industry as part of fostering a low carbon green growth industry. Among the LED lighting industry, machine vision technology used for factory automation is a field required by the manufacturing industry and is growing steadily every year.

This machine vision technology has been widely distributed and used since the late 1980s in the U.S., Japan, and the EU, where the industrial structure is advanced, and is expanding to all industrial fields. It was used as a PCB-related industry, electric component industry, pharmaceutical industry, chemical industry, automobile industry, etc., and its use is gradually expanding. In addition, in relation to this, there have been proposed Patent No. 10-1438340, Patent Publication No. 10-2015-0116247, and the like.

Such machine vision technology requires high speed and high resolution as well as more precise and accurate inspection to improve productivity in many fields such as PCB inspection, LCD panel inspection, and semiconductor inspection. , Fast response characteristics, and precise and accurate light quantity control are required.

The method of controlling the LED lighting for machine vision is largely divided into four types: voltage control, current control, PWM, and strobe method, and each business site adopts and uses a method suitable for the application field.

However, in most LEDs, the current curve changes greatly according to the voltage change, so the voltage control method is not mainly used in industries that require precise control such as machine vision.

In addition, the current control method is a method of varying the amount of light by varying the supply current of the LED, and has a characteristic of linearly changing the amount of light compared to the current change, but has a disadvantage of generating accumulated heat versus power.

Next, the PWM method is a method of varying the amount of light by changing the power supplied to the LED at a constant ON/OFF ratio. Although the circuit configuration is relatively simple and easy to control, the flicker phenomenon occurs according to the driving frequency, resulting in high-speed precision control. Not suitable for

Lastly, the strobe method can produce strong light output in a short time, but has a disadvantage in that it cannot control the amount of light.

Reference 1: Registered Patent No. 10-1438340 Reference 2: Unexamined Patent Publication No. 10-2015-0116247

Therefore, the present invention is to solve these problems, the present invention is a hybrid dimming (Hybrid-Dimming) that combines the current control method and the strobe method to compensate for the disadvantages of the conventional LED driving method and maximize the advantages. Its purpose is to provide a hybrid dimming control device capable of controlling the LED lighting device for machine vision with high light intensity, high precision, and high efficiency by applying technology.

The present invention in order to solve such a technical problem;

A current control unit that controls the amount of current driving the machine vision LED lighting device, a strobe control unit that is connected to the current control unit in a cascade manner and operates as a strobe, a current control signal for current adjustment of the current control unit, and the It provides a hybrid dimming control device for a machine vision LED lighting device, characterized in that it comprises a main controller for outputting a strobe control signal for on-time control of the strobe control unit.

At this time, the current control signal output from the main controller is a digital voltage signal and is converted into an analog voltage signal through a dedicated DA converter to variably control the current control unit, and the strobe control signal output from the main controller passes through a switching unit. It is characterized in that the strobe control unit controls on-time.

In addition, the current control unit is composed of a MOSFET as a first switching element, the strobe control unit is composed of a MOSFET as a second switching element, and the switching unit is composed of a BJT as a third switching element.

In addition, the source terminal of the first switching device is connected to the drain terminal of the second switching device, and the current control signal of the main controller converted into an analog voltage signal through the DA converter through the gate terminal of the first switching device. And a gate terminal of the second switching device is connected to a collector terminal of the third switching device through a resistor to receive a strobe control signal.

In addition, the main controller may variably control an output current of the current control unit and variably control an on-time of the strobe control unit.

In addition, the main controller calculates a deviation between the actual output and an ideal value having a linear characteristic in order to ensure current linearity, and finds a DAC value corresponding to an ideal curve at a predetermined unit interval and finds the DAC value. After checking the result by grasping the characteristics of and applying a log function similar to the increase characteristic curve of the DAC, comparing the result with the ideal value, calculating the deviation, and applying a constant to reduce the deviation, the formula is calculated. It is characterized by linearizing the output of the current by redefining.

According to the present invention, when controlling an LED lighting device for machine vision, the output current and the output time can be finely adjusted, and when this hybrid method is applied, a high output can be produced in a short time, so that cumulative heat is hardly generated and the output current It is also effective for extracting images as the and on-time can be varied.

Further, according to the present invention, since the light output of the LED lighting device for machine vision can be varied, there is also the flexibility to provide an optimal environment suitable for the characteristics of a detection sample.

1 is a block diagram of a hybrid dimming control device of an LED lighting device for machine vision according to the present invention.
2 is a circuit diagram of a hybrid dimming control device of an LED lighting device for machine vision according to the present invention.

Hereinafter, the characteristics of the hybrid dimming control apparatus for a machine vision LED lighting apparatus according to the present invention may be understood by the embodiments described in detail with reference to the accompanying drawings.

Prior to this, terms or words used in the specification and claims should not be construed as being limited to their usual or dictionary meanings, and the inventors appropriately explain the concept of terms in order to explain their own invention in the best way. Based on the principle that it can be defined, it should be interpreted as a meaning and concept consistent with the technical idea of the present invention.

Therefore, the embodiments described in the present specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention, and do not represent all the technical ideas of the present invention, so at the time of the present application, they can be replaced. It should be understood that there may be various equivalents and variations.

Referring to FIG. 1, the hybrid dimming control device of the LED lighting device for machine vision according to the present invention combines a current control method and a strobe method in order to precisely control the brightness of the LED and reduce accumulated heat according to power consumption. It is a device that can control the LED lighting device for machine vision with high light intensity, high precision, and high efficiency by applying Hybrid-Dimming technology.

The hybrid dimming control device of the LED lighting device for machine vision according to the present invention includes a current control unit 10 for controlling the amount of current driving the LED lighting device 1 for machine vision, the current control unit 10 and the cascade ( A strobe control unit 20 that is connected in a cascade method and operates as a strobe, a current control signal for current adjustment of the current control unit 10 and a strobe for on-time control of the strobe control unit 20 It includes a main controller 30 for outputting a control signal.

In addition, the current control signal output from the main controller 30 is a digital voltage signal, which is converted into an analog voltage signal through a dedicated DA converter (DAC) 40, and the current control unit 10 The strobe control signal that is input to and outputs from the main controller 30 controls the strobe control unit 20 on-time through the switching unit 50.

At this time, the current control unit 10 is composed of a field effect transistor (FET) as the first switching element (Q1), the strobe control unit 20 is composed of a FET as the second switching element (Q2), and the switching unit Reference numeral 50 denotes a third switching element Q3 and is preferably composed of a Bipolar Junction Transistor (BJT).

And, the source terminal of the first switching device (Q1) is connected to the drain terminal of the second switching device (Q2), the analog through the DA converter (DAC) 40 through the gate terminal of the first switching device (Q1). A current control signal of the main controller 30 converted and outputted into a type of voltage signal is input, and accordingly, the amount of current of the first switching device Q1 is controlled.

In addition, the gate terminal of the second switching element Q2 is connected to the collector terminal of the third switching element Q3 of the switching unit 50 through a resistor to receive a strobe control signal, and accordingly, the second switching element ( Q2) is switched on and off (ON/OFF) and operates as a strobe.

In addition, the base of the third switching device (Q3) receives the strobe control signal output through the main controller 30 is turned on and off (ON/OFF), and is output as a switching signal to the second switching device (Q2). It is input to the gate of the FET, and accordingly, the second switching device Q2 is switched on and off (ON/OFF).

According to this configuration, the first switching element Q1 operates to control current, and the second switching element Q2 operates as a strobe. At this time, the change of the current of the first switching device (Q1) can be controlled in units of at least 1mA, and the strobe operation of the second switching device (Q2) is operated with an on-time of at least 1us. It is desirable to design it so that it can be used.

For fine adjustment of current and on-time control using the first and second switching devices (Q1, Q2), the main controller 30 uses an ARM-based 32-bit microcontroller unit (MCU). And the maximum operation is 150 DMIPS (Dhrystone Million Instructions Per Second). At this time, DMIPS is expressed as MIPS (Millions of Instructions Per Second), which is the ability to execute a million instructions per second, and is used for smartphones, graphics, and set-top box processors.

Hereinafter, a driving principle of a hybrid dimming control device for a machine vision LED lighting device according to the present invention will be described.

The current control of the FET, which is the first switching device Q1 of the current control unit 10, varies the voltage Vgs, which is a current control signal applied to the gate terminal of the FET, so that it passes from the drain to the source. It controls the current. At this time, the voltage applied to Vgs is controlled by the DA converter (DAC) 40 having 4096 resolutions and can be varied from 0 to 5V, and the Vgs variable range of the first switching device (Q1) is a separate calibration operation. It is set through and the maximum output current can be set in the range desired by the user.

In addition, the strobe control of the FET, which is the second switching device Q2 of the strobe control unit 20, instantaneously turns on and off (ON/OFF) the voltage Vgs, which is the strobe control signal applied to the gate terminal of the FET. Blocks and passes the current flowing from the drain to the source. At this time, the variable of the strobe control signal Vgs is operated through the third switching element (Q3) of the switching unit 50, which is a separate ON/OFF circuit, and can be switched at high speed up to several tens of ns. Designed.

All operations of the current control unit 10 and the strobe control unit 20 operate in synchronization with a trigger signal, which is an external input signal, and current control and on-time control are performed by the MCU, which is the main controller 30. It proceeds sequentially according to the firmware (F/W) design.

Meanwhile, the DA converter (DAC) 40 variably adjusts the current control signal Vgs at a constant rate, but the current flowing through the first switching device Q1 does not guarantee linearity as shown in FIG. 2. Accordingly, in the present invention, a separate equation is applied to ensure the linearity of the current, and as a result of applying the equation, the linearity can be secured as shown in FIG.

Specifically, the conventional control method (Original) applies a method of selectively using the desired range at step 4096, which is the resolution of the DA converter (DAC) 40, and multiplying through the selected range and “current control variable step” And Offset were calculated.

[Original control method (Original)]

# Multiply = (MAX_Step-min_Step) / (APP_MAX-1)

# Offset = min-Step-Multiply

For example, “Current Control Variable Step” is set to 1000 steps (APP_MAX), and the DAC value corresponding to 1-Step, which is the minimum step, is selected as 50 (min-Step), and is 999-Step corresponding to the maximum Step. When applied to 3500 (MAX-Step), Multiply is about 3.456 and Offset is 46.544.

# Current Control Step: 0 ~ 999 (1000-Step)

# min-Step(1-Step): 50 DAC-Step

# MAX-Step(999-Step): 3500 DAC-Step

# Multiply = (3500-50) / (999-1) ≒ 3.456

# Offset = 50-3.456 = 46.544

In such an existing control method (Original), when the “current control variable step” is sequentially increased and varied, as shown in FIG. 4, the variable step increases linearly, but the output current has a nonlinear characteristic.

On the other hand, in the present invention, in order to ensure the linear output characteristic of the current, the linearity was compensated in the following way, and an equation was derived accordingly.

First, a method of calculating an equation for ensuring current linearity according to the present invention is as follows.

① Calculate the deviation between the actual output and the ideal value with linear characteristics. (Calculate the deviation from the ideal)

② Search the DAC value corresponding to the ideal curve at regular unit intervals. (Find the DAC value corresponding to Ideal)

③ Find out the characteristics of the DAC value found in step ② (find the characteristic curve).

④ Apply a log function similar to the DAC's increasing characteristic curve (introduce an applicable function).

⑤ After checking the result by applying the Log function, compare it with the ideal value and calculate the deviation. (Simulation of the equation)

⑥ Apply a constant to reduce the deviation from the ideal value. (Equation correction)

⑦ Redefine the formula with the result obtained in steps ① ~ ⑥. (Redefine the formula)

An equation diagram for ensuring the linear output characteristic of the current is as shown in FIG. 5. At this time,'STEP' in the table means the DAC variable STEP,'Current' is the output current amount (Original),'EQ-Current' is the output current amount (applying formula), and'Equation' means the output linearity formula. .

The following formula can be derived through the formula calculation method and formula diagram for ensuring current linearity according to the present invention, which follows the sequence of the formula calculation steps ① to ⑦.

① EQ_TMP_1 = K3 / MAX_STEP

② EQ_TMP_2 = STEP x EQ_EMP_1

③ EQ_C1 = K3-EQ_TMP_2

④ EQ_TMP_3 = Log10(STEP)

⑤ EQ_TMP_4 = 1 / EQ_TMP_3

⑥ SUB_EQ = (EQ_TMP_4 +K2) x EQ_C1

⑦ EQ_STEP = (K1 + SUB_EQ) x STEP

At this time, K1, K2, K3 are constants.

As a result of applying this formula, it can be seen that the output current linearly increases as the step increases, as shown in FIG. 6.

As a result, referring to Figs. 7 and 8, when the step of the control step is sequentially increased, the output current does not increase linearly, but when the step is increased, the output current is increased. Linearity can be guaranteed.

Hereinafter, the results of applying the conventional control method to the LED lighting device for machine vision and the hybrid dimming control method according to the present invention will be described.

First of all, in the case of current control and output on-time change, when using the hybrid dimming control method according to the present invention, both the output current and on-time can be variable. The degree of freedom for the sample can be increased. 9 is data obtained by measuring the actual output current waveform and the input trigger signal as an operation reference using the current probe of the oscilloscope. The left side shows the case where the output current is set differently while the on-time is fixed. And on the right is the case of setting the On-Time differently while the output current is fixed. At this time, in the case of fixed on-time and current variable on the left, the on-time is 38 ms and the current is changed to 900 mA to 500 mA, and the right is on-time variable and current In the case of fixed, the current is 900mA and the on-time is variable from 38ms to 20ms.

Next, as a result of image processing, when using the conventional stove method, in which the amount of light cannot be adjusted, there is a saturation part as shown in the left side of Fig. 10, which affects image detection, but the hybrid of the present invention When the hybrid dimming control method is applied, since the amount of light can be adjusted, a normal image can be detected as shown in the right side of FIG. 10.

Finally, looking at the cumulative heat generation over time, when the hybrid dimming control method of the present invention is applied, the cumulative heat generation over time is hardly generated as shown in FIG. 12, so that a change in current output characteristics due to heat generation does not occur. Does not. In this case, the thermal test condition is LV-SHL2-60-20-P01 for output lighting, MAX 5[A] for load, TTL 1-Hz for input trigger, and On-Time for output lighting. Is set to 300ms and the accumulated time is 100 minutes. It can be seen that the cumulative amount of heat generated over time remains different from the constant current control method as shown in FIG. 12. In addition, FIG. 13 is a thermal imaging camera measurement screen. It can be seen that the hybrid dimming control method on the upper side rarely generates accumulated heat over time compared to the constant current method on the lower side.

As a result, the hybrid dimming control method of the present invention can finely adjust the output current and the output time, and if such a hybrid method is applied, it is possible to produce high output in a short time, so that the accumulated heat is hardly generated and the output It can be seen that it is effective in extracting an image because the current and on-time can be varied.

In addition, since the hybrid dimming control method of the present invention can vary the light output, it has the flexibility to provide an optimal environment suitable for the characteristics of a detection sample.

The above description is merely illustrative of the technical idea of the present invention, and those of ordinary skill in the technical field to which the present invention pertains are capable of various modifications and variations without departing from the essential characteristics of the present invention. The scope of protection should be interpreted by the claims below, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

1: Machine vision LED lighting device 10: Current control unit
20: strobe control unit 30: main controller
40: DA converter 50: switching unit
Q1: first switching element Q2: second switching element
Q3: 3rd switching device

Claims (6)

A current control unit that controls the amount of current driving the machine vision LED lighting device, a strobe control unit that is connected to the current control unit in a cascade manner to operate as a strobe, a current control signal for current adjustment of the current control unit, and the A hybrid dimming control device for an LED lighting device for machine vision, comprising a main controller for outputting a strobe control signal for on-time control of the strobe control unit.
The method of claim 1,
The current control signal output from the main controller is a digital voltage signal and is converted into an analog voltage signal through a dedicated DA converter to variably control the current control unit,
The strobe control signal output from the main controller controls the strobe control unit on-time through a switching unit (50).
The method of claim 2,
The current control unit is composed of a MOSFET as a first switching element, the strobe control unit is composed of a MOSFET as a second switching element, and the switching unit is composed of a BJT as a third switching element. Hybrid dimming control system.
The method of claim 3,
The source terminal of the first switching device is connected to the drain terminal of the second switching device, and the current control signal of the main controller converted into an analog voltage signal through the DA converter through the gate terminal of the first switching device is input. under,
A hybrid dimming control device for a machine vision LED lighting device, characterized in that the gate terminal of the second switching device is connected to a collector terminal of the third switching device through a resistor to receive a strobe control signal.
The method of claim 1,
The main controller variably controls the output current of the current control unit and variably controls the on-time of the strobe control unit.
The method of claim 1,
The main controller calculates a deviation between the actual output and an ideal value having a linear characteristic in order to ensure current linearity, and finds a DAC value corresponding to an ideal curve at a predetermined unit interval, and the characteristic of the DAC value After checking the result by applying a log function similar to the increase characteristic curve of DAC, calculating the deviation by comparing it with the ideal value, and redefining the formula by applying a constant for reducing the deviation. A hybrid dimming control device for an LED lighting device for machine vision, characterized in that the output of the current is linearized.

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