How to do a good job in the SMT placement of LED module “white balance”?
How to do a good job in the SMT placement of LED module “white balance”?
As we all know, the LED display module is a one by one through the research and determination of parameters, machine mounting, after welding processing, assembly and aging and so on steps produced.
The first step in the process of research and determination of parameters, how to do “white balance” has become a big problem for most of the LED display industry practitioners. So, how to set the LED module in the SMT chip “white balance”? Listen to the company's most professional engineers to you one by one.
The basic principle of full-color LED module is to control the current size through the chip, and then control the brightness of the three colors R (red), G (green), B (blue) to combine a variety of colors. In the numerical definition, we stipulate that the brightness of the three colors are 0-255, when the three colors are the brightest, that is, white. Look at a piece of LED display color is not correct, it depends on the “white balance” adjustment is good. Then, the current, resistance, brightness, coordinates (X,Y), color temperature, is the white balance process directly debugging the effect of the main factors.
We explain in detail from the following six aspects:
First, the current
According to IC and lamp requirements, the lamp carrier current does not exceed 20mA, otherwise it will damage the components or lamp board; according to the actual situation of the company, the current set range: indoor chip pin current (calculated value) does not exceed 16mA, outdoor chip pin current (calculated value) does not exceed 20mA; if the board in the specified range of the board in the debugging of the color is not correct, and according to the actual needs of the current increase or decrease.
The brightness of the module is changed by adjusting the resistance to control the IC pin current, so the resistance and brightness is inversely proportional to the relationship, according to the actual requirements, in order to ensure that the normal brightness of the board and does not deviate from the color of the case, you can control the resistor value in: indoor resistor resistance value
Greater than or equal to 1.1K range, outdoor resistor resistance value greater than or equal to 910R, at the same time in the conventional integrated IC (FM7258EN.x/DP7268) on the board, the line tube pin current peak maximum of not more than 2.5A, the conventional integrated IC (FM7258EN/DP7268B) on the board, the line tube pin current peak
Maximum 2.8A, if the board color is not right or cannot meet the customer's requirements within the specified range, you can notify the technician, so as to make a solution.
Apply the following formula to calculate the output current/resistance of the constant-current chip:
VR-EXT = 1.23V; Gain = 15; IOUT = VR-EXT * (1/Rext) * 15; Rext = (VR-EXT/IOUT) * 15
* VR-EXT in the formula refers to the voltage value at the R-EXT end, Rext refers to the resistor value externally connected to the R-EXT end, IOUT refers to the output electricity, and Gain means (gain/increase). When the resistor value is 930Ω, the output current value is 20mA by formula calculation; when the resistor value is 1860Ω, the output current value is 10mA.
Example: It is known that VR-EXT=1.23V; Rext=930Ω (0.93K). Find the current value of IOUT?
Calculation: IOUT=VR-EXT*(1/Rext)*15
IOUT=1.23*(1/0.93)*15
IOUT=19.8mA≈20mA
The output current of the integrated chip can be calculated by applying the following formula:
VDS=18.6V; IO= {(VDS/R-Rext )+(VDS/G-Rext)+(VDS/B-Rext)} x IO's carry pixel points
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* VDS in the formula is the value of withstand voltage at the output of IOUT of the constant-current chip, and IO is the value of current (in A) at the output of the integrated chip.
IO is the current value (in A) of the output side of the integrated chip, R-Rext, G-Rext, B-Rex are the resistors of the constant-current chip (red, green, blue) connected to the R-Ext side, and the IO carry pixel point is the total pixel point of one line of the light board. When R-Rext, G-Rext, B-Rex resistor value is 1300Ω, IO carry pixel points is 64 points, through the formula to calculate the IO output current value of 2.7A.
Example: It is known that VDS = 18.6V; R-Rext , G-Rext , B-Rext = 1300Ω, 1300Ω, 1300Ω; IO carry pixel points is 64 points, find the current value of IO?
Calculation: IO= {(18.6/1300 +18.6/1300 +18.6/1300) x 64}
IO= {0.0429x 64}
IO= 2.7456A ≈ 2.7A
Brightness
Brightness is based on the “channel models, engineering models, high-end models” three models to determine, or customer requirements to debug the brightness, the brightness of the high-end models against the engineering models to determine the brightness of the company's current three brightness is as follows:
Third, the coordinates
White balance can be adjusted mainly depends on the coordinates are not correct, white balance is actually composed of a two-dimensional concept (X,Y), according to the actual situation of the company's current indoor/outdoor coordinates are: X: 0.2500-0.2600, Y: 0.2600-0.2700 range, no matter what the situation is X value can not be greater than the Y value.
Fourth, color temperature
Color temperature is the screen in the white light to give people the visual temperature difference between warm and cold, the current product, in the usual white balance debugging, the color temperature will be controlled in the indoor 14,000-15,000, outdoor in the 17,000-20,000, but also according to the actual situation of the judgment.
Five, control parameters
Control system parameters, but also an important indicator of a display, in the spirit of the rain system debugging white balance when we set the clock parameters at 16.67HZ, gray level to 4096 standard, brightness efficiency 81.57% can be (excluding the use of double locks and PMW series IC), the height and width of the screen according to the requirements of the box to set the parameters.
Six, debugging white balance
The same batch of lamp beads without repeating the debugging instructions
1. According to the characteristics of the lamp beads, when the use of the same batch of lamp beads in the case of conventional products only need to do a first piece; and when the use of double-locked and PMW series IC should be re-do a first piece.
2. When the customized order has brightness, current and white balance requirements need to re-do the first piece.
All the above parameters are based on conventional products as a standard, other non-standard products need another standard (provided by the technical department), the light gun in the debugging distance of 3-5 meters for the best.
The first step in the process of research and determination of parameters, how to do “white balance” has become a big problem for most of the LED display industry practitioners. So, how to set the LED module in the SMT chip “white balance”? Listen to the company's most professional engineers to you one by one.
The basic principle of full-color LED module is to control the current size through the chip, and then control the brightness of the three colors R (red), G (green), B (blue) to combine a variety of colors. In the numerical definition, we stipulate that the brightness of the three colors are 0-255, when the three colors are the brightest, that is, white. Look at a piece of LED display color is not correct, it depends on the “white balance” adjustment is good. Then, the current, resistance, brightness, coordinates (X,Y), color temperature, is the white balance process directly debugging the effect of the main factors.
We explain in detail from the following six aspects:
First, the current
According to IC and lamp requirements, the lamp carrier current does not exceed 20mA, otherwise it will damage the components or lamp board; according to the actual situation of the company, the current set range: indoor chip pin current (calculated value) does not exceed 16mA, outdoor chip pin current (calculated value) does not exceed 20mA; if the board in the specified range of the board in the debugging of the color is not correct, and according to the actual needs of the current increase or decrease.
The brightness of the module is changed by adjusting the resistance to control the IC pin current, so the resistance and brightness is inversely proportional to the relationship, according to the actual requirements, in order to ensure that the normal brightness of the board and does not deviate from the color of the case, you can control the resistor value in: indoor resistor resistance value
Greater than or equal to 1.1K range, outdoor resistor resistance value greater than or equal to 910R, at the same time in the conventional integrated IC (FM7258EN.x/DP7268) on the board, the line tube pin current peak maximum of not more than 2.5A, the conventional integrated IC (FM7258EN/DP7268B) on the board, the line tube pin current peak
Maximum 2.8A, if the board color is not right or cannot meet the customer's requirements within the specified range, you can notify the technician, so as to make a solution.
Apply the following formula to calculate the output current/resistance of the constant-current chip:
VR-EXT = 1.23V; Gain = 15; IOUT = VR-EXT * (1/Rext) * 15; Rext = (VR-EXT/IOUT) * 15
* VR-EXT in the formula refers to the voltage value at the R-EXT end, Rext refers to the resistor value externally connected to the R-EXT end, IOUT refers to the output electricity, and Gain means (gain/increase). When the resistor value is 930Ω, the output current value is 20mA by formula calculation; when the resistor value is 1860Ω, the output current value is 10mA.
Example: It is known that VR-EXT=1.23V; Rext=930Ω (0.93K). Find the current value of IOUT?
Calculation: IOUT=VR-EXT*(1/Rext)*15
IOUT=1.23*(1/0.93)*15
IOUT=19.8mA≈20mA
The output current of the integrated chip can be calculated by applying the following formula:
VDS=18.6V; IO= {(VDS/R-Rext )+(VDS/G-Rext)+(VDS/B-Rext)} x IO's carry pixel points
}
* VDS in the formula is the value of withstand voltage at the output of IOUT of the constant-current chip, and IO is the value of current (in A) at the output of the integrated chip.
IO is the current value (in A) of the output side of the integrated chip, R-Rext, G-Rext, B-Rex are the resistors of the constant-current chip (red, green, blue) connected to the R-Ext side, and the IO carry pixel point is the total pixel point of one line of the light board. When R-Rext, G-Rext, B-Rex resistor value is 1300Ω, IO carry pixel points is 64 points, through the formula to calculate the IO output current value of 2.7A.
Example: It is known that VDS = 18.6V; R-Rext , G-Rext , B-Rext = 1300Ω, 1300Ω, 1300Ω; IO carry pixel points is 64 points, find the current value of IO?
Calculation: IO= {(18.6/1300 +18.6/1300 +18.6/1300) x 64}
IO= {0.0429x 64}
IO= 2.7456A ≈ 2.7A
Brightness
Brightness is based on the “channel models, engineering models, high-end models” three models to determine, or customer requirements to debug the brightness, the brightness of the high-end models against the engineering models to determine the brightness of the company's current three brightness is as follows:
Third, the coordinates
White balance can be adjusted mainly depends on the coordinates are not correct, white balance is actually composed of a two-dimensional concept (X,Y), according to the actual situation of the company's current indoor/outdoor coordinates are: X: 0.2500-0.2600, Y: 0.2600-0.2700 range, no matter what the situation is X value can not be greater than the Y value.
Fourth, color temperature
Color temperature is the screen in the white light to give people the visual temperature difference between warm and cold, the current product, in the usual white balance debugging, the color temperature will be controlled in the indoor 14,000-15,000, outdoor in the 17,000-20,000, but also according to the actual situation of the judgment.
Five, control parameters
Control system parameters, but also an important indicator of a display, in the spirit of the rain system debugging white balance when we set the clock parameters at 16.67HZ, gray level to 4096 standard, brightness efficiency 81.57% can be (excluding the use of double locks and PMW series IC), the height and width of the screen according to the requirements of the box to set the parameters.
Six, debugging white balance
The same batch of lamp beads without repeating the debugging instructions
1. According to the characteristics of the lamp beads, when the use of the same batch of lamp beads in the case of conventional products only need to do a first piece; and when the use of double-locked and PMW series IC should be re-do a first piece.
2. When the customized order has brightness, current and white balance requirements need to re-do the first piece.
All the above parameters are based on conventional products as a standard, other non-standard products need another standard (provided by the technical department), the light gun in the debugging distance of 3-5 meters for the best.