CN104768280B - Color temperature compensation method for LED lamp - Google Patents

Abstract

The invention discloses a color temperature compensation method of an LED lamp, which utilizes the rule that the color temperature of the LED particle string changes with the change of the working current, reversely solves the working current required for the LED particle string to achieve the expected color temperature; Make the LED particle string A follow the working current Work, LED particle string B according to the working current Work, so as to obtain the mixed light with expected color temperature as CCT and luminous flux as φ. The present invention has the characteristics that the color temperature of the actually obtained mixed light after light mixing has a small deviation from the expected color temperature, and effectively reduces stroboscopic flicker.

Description

Color temperature compensation method of LED lights

technical field

The invention relates to the field of LED lighting, in particular to a color temperature compensation method of an LED lamp which can effectively reduce color temperature deviation.

Background technique

With the development of LED intelligent lighting, the brightness, color temperature, color, scene, etc. of LED can be controlled by various wireless or wired methods, and the control becomes more and more convenient. However, at present, people do not pay enough attention to the light quality and effect of LED lighting, and the stroboscopic problem and color temperature shift of LED have not attracted enough attention.

At present, the dimming of LEDs is usually realized by PWM pulse width modulation, that is, the on-off of a switch is used to adjust the PWM duty cycle of the LED current, so as to realize the adjustment of brightness. The adjustment of color temperature usually uses 2 channels of LED particles with different color temperatures to mix light, that is, to use 6500K cool color temperature LED particles and 3000K warm color temperature LED particles to mix light, and adjust the PWM of these 2 channels of LEDs respectively to realize the adjustment of color temperature and brightness. However, the LED current in the PWM state fluctuates greatly. At high frequencies, the current jumps periodically from 0 to the maximum value. Although the human eye cannot feel the flicker due to visual delay, the high-frequency fluctuations may affect biological The sympathetic nervous system can cause dizziness, vomiting and other symptoms for a long time. High-frequency photography under this light will also show frame loss.

Chinese Patent Authorization Publication No.: CN102595722A, the authorized publication date is July 18, 2012, which discloses a LED color temperature control device, including a regulator and a driver; the regulator includes: a color temperature regulation control panel for switching on and off the power supply And for the operator to send out the color temperature adjustment signal; and the control signal generator, which receives the color temperature adjustment control panel to send out the color temperature adjustment signal and then outputs the corresponding control signal according to the instruction; the driver includes: a microprocessor, which receives the signal from the control signal generator The control signal, after analyzing and calculating the control signal, sends out a PWM regulation signal to change the LED working current; and the constant current drive module outputs a constant LED working current according to the PWM regulation signal provided by the microprocessor. The disadvantage of this invention is that the red shift phenomenon will occur in the LED lamp, and the color temperature deviation is relatively large.

Contents of the invention

The purpose of the present invention is to provide a color temperature compensation method for LED lamps that can effectively reduce the color temperature deviation in order to overcome the disadvantages of the color temperature compensation method in the prior art between the color temperature of the mixed light actually obtained and the expected color temperature. .

In order to achieve the above object, the present invention adopts the following technical solutions:

A color temperature compensation method for an LED lamp. The LED lamp includes a single-chip microcomputer, a filter circuit, and two DC drivers that are electrically connected in sequence, and also includes an LED particle string A with a cool color temperature and an LED particle string A with a warm color temperature that are electrically connected to the two DC drivers, respectively. LED particle string B, 2 groups of LED particle strings include the same number of serial LED particles, and the single-chip microcomputer is electrically connected to the computer through a data line; the color temperature compensation method includes the following steps:

(1-1) Set the color temperature of the LED particle string A as CCTc, and the operating current as Ic; the color temperature of the LED particle string B as CCTw, and the operating current as Iw;

Set the working current of the LED particle string A when the color temperature is CCT and the luminous flux is φ after mixing the light from the LED particle string A and B is I′ _c , and the working current of the LED particle string B is I′ _w ;

(1-2) Let Imax be the maximum operating current of LED particle strings A and B, and there are several pairs of dimming signals and color temperature signals stored in the computer, and the values and dimming signals of I′ _c and I′ _w are recorded and the corresponding relationship table of the corresponding relationship between the color temperature signal pair;

The computer makes the working current Ic of the LED particle string A gradually increase from 0 to Imax by changing the dimming signal and the color temperature signal pair sent to the single-chip microcomputer, and uses a color temperature measuring instrument to detect the output color temperature CCTc of the LED particle string A, and uses the computer Select at least 8 Ic and the corresponding output color temperature CCTc to form a point (Ic, CCTc), and draw the curve 1 of the output color temperature changing with the operating current Ic in the computer;

Make the operating current Iw of the LED particle string B gradually increase from 0 to Imax, use a color temperature measuring instrument to detect the output color temperature CCTw of the LED particle string B, and use a computer to select at least 8 Iw and corresponding output color temperature CCTw to form points (Iw, CCTw ), draw the curve 2 of the output color temperature changing with the operating current Iw in the computer;

(1-3) The computer performs linear fitting on curve 1 and curve 2 respectively, and obtains the linear fitting formula CCTc=d ₁ I _c +d ₂ corresponding to curve 1,

The linear fitting formula corresponding to curve 2 CCTw=g ₁ I _w +g ₂ ; where, d ₁ , d ₂ , g ₁ , and g ₂ are all non-zero real numbers;

(1-4) Set the luminous flux of LED particle string A after light mixing as Φc, and the luminous flux of LED particle string B as Φw,

Then the color temperature CCT after light mixing=(Φc×CCTc+Φw×CCTw)/(Φc+Φw);

(1-5) The computer utilizes the following formula derived according to steps (1-3) and (1-4) to calculate _I′c and _I′w :

CCT=(Φc×CCTc+Φw×CCTw)/φ,

Φc=I′c× _ηc ,Φw= _I′w ×ηw;

CCTc=d ₁ I′ _c +d ₂ , CCTw=g ₁ I′ _w +g ₂ ;

Wherein, φ=Φc+Φw, Φc=Ic×ηc, Φw=Iw×ηw, ηc is the luminous light effect of the set LED particle string A, and ηw is the set LED luminous light effect of the LED particle string B;

(1-6) After obtaining _I'c and _I'w , the computer queries the relational table, and obtains the dimming signal and color temperature signal pair corresponding to _I'c and _I'w and sends them to the single-chip microcomputer, so that the LED particle string A Working according to the working current I' _c , LED particle string B working according to the working current I' _w , to obtain the mixed light with color temperature CCT and luminous flux φ.

Figure 1 and Figure 2 are respectively the curves of the color temperature of a certain brand of LED 6500K and 3000K particles as a function of the operating current. It can be seen from Figure 1 and Figure 2 that the color temperature of the LED particle string will change with the operating current of the LED particle string It can be seen that when the operating current decreases, the color temperature of the two kinds of LED particle strings will have a red shift phenomenon, and the change of the 6500K LED particle string is relatively larger.

In a dimming and color temperature system, it is generally considered that the color temperature (rated color temperature) is constant under different operating currents, and the color temperature after light mixing is the luminous flux-weighted average of the color temperature of the two LED particle strings; but In fact, because the color temperature of LED particle strings will shift under different operating currents, using the weighted average of luminous flux to adjust the color temperature will lead to the inability to obtain the expected color temperature after light mixing. The actual color temperature obtained by the usual color temperature compensation method The color temperature of the mixed light deviates greatly from the expected color temperature.

The present invention proposes a brand-new color temperature compensation method for LED lamps, using the law that the color temperature of LED particle strings will change with the change of operating current, and reversely solves the working current required for LED particle strings to achieve the expected color temperature ; Make the LED particle string A work according to the working current _I′c , and the LED particle string B work according to the working current _I′w , so as to obtain the mixed light with the expected color temperature as CCT and the luminous flux as φ.

The present invention utilizes the law that the color temperature of the LED particle string will change with the change of the working current, calculates and obtains the working current required for the LED particle string to achieve the expected color temperature; The color temperature has a small deviation from the expected color temperature.

Preferably, the rated color temperature of each LED particle in the LED particle string A is 6500K, and the rated color temperature of each LED particle in the LED particle string B is 3000K.

Preferably, the rated color temperature of each LED particle in the LED particle string A is 6500K, and the rated color temperature of each LED particle in the LED particle string B is 2700K.

Preferably, said ηc is equal to ηw.

Preferably, in the step (1-2), the operating current Ic of the LED particle string A gradually increases from 0 to Imax with a step size of 80 to 105 mA.

Preferably, in the step (1-2), the working current Iw of the LED particle string B gradually increases from 0 to Imax with a step size of 90 to 105 mA.

Therefore, the present invention has following beneficial effect:

(1) Using the law that the color temperature of the LED particle string will change with the change of the working current, calculate the working current required for the LED particle string to achieve the expected color temperature;

(2) Make the deviation between the color temperature of the mixed light actually obtained after light mixing and the expected color temperature smaller;

(3) Effectively reduce strobe.

Description of drawings

Fig. 1 is a graph showing that a color temperature of the 6500K LED particle string of the present invention varies with operating current;

Fig. 2 is a graph showing that a color temperature of the 3000K LED particle string of the present invention varies with operating current;

Fig. 3 is a kind of flowchart of the embodiment of the present invention;

Fig. 4 is a circuit diagram of the LED lamp of the present invention.

In the figure: single chip microcomputer 1, filter circuit 2, DC driver 3, LED particles 4.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

The embodiment shown in Figure 4 is a color temperature compensation method for LED lamps. The LED lamp includes a single-chip microcomputer 1, a filter circuit 2, and two DC drivers 3 that are electrically connected in sequence, and also includes cold circuits that are electrically connected to the two DC drivers respectively. The LED particle string A of the color temperature and the LED particle string B of the warm color temperature, each of the two groups of LED particle strings includes two serial LED particles 4, and the single-chip microcomputer is electrically connected to the computer through a data line;

As shown in Figure 3, the color temperature compensation method includes the following steps:

Set the color temperature of the LED particle string A with a cool color temperature of 6500K to CCTc and the operating current to Ic; the color temperature of the LED particle string B with a warm color temperature of 1000K to CCTw and the operating current to Iw;

Set the working current of the LED particle string A when the color temperature is CCT and the luminous flux is φ after mixing the light from the LED particle string A and B is I′ _c , and the working current of the LED particle string B is I′ _w ;

Step 100, draw the curve of color temperature changing with operating current

Let Imax be the maximum operating current of LED particle strings A and B, and there are 2000 pairs of dimming signals and color temperature signals stored in the computer, and the values of I′ _c and I′ _w and the dimming signals and color temperature signals are recorded a correspondence table of correspondences of signal pairs;

The computer makes the working current Ic of the LED particle string A gradually increase from 0 to Imax by changing the dimming signal and the color temperature signal pair sent to the single-chip microcomputer, and uses a color temperature measuring instrument to detect the output color temperature CCTc of the LED particle string A, and uses the computer Select 8 Ic and the corresponding output color temperature CCTc to form a point (Ic, CCTc), and draw the curve 1 of the output color temperature changing with the operating current Ic as shown in Figure 1 in the computer;

Make the working current Iw of the LED particle string B gradually increase from 0 to Imax, use a color temperature measuring instrument to detect the output color temperature CCTw of the LED particle string B, and use a computer to select 8 Iw and the corresponding output color temperature CCTw to form points (Iw, CCTw) , draw the curve 2 of the output color temperature as shown in Figure 2 as the working current Iw changes in the computer;

Step 200, get 2 linear fitting formulas

The computer carries out linear fitting to curve 1 and curve 2 respectively, obtains the linear fitting formula CCTc=0.331I _c +6557 corresponding to curve 1,

The linear fitting formula corresponding to curve 2 CCTw=0.06I _w +2956;

Step 300, obtain the color temperature formula after light mixing

Set the luminous flux of LED particle string A after light mixing to Φc, and the luminous flux of LED particle string B to Φw,

Then the color temperature CCT after light mixing=(Φc×CCTc+Φw×CCTw)/(Φc+Φw);

Step 400, calculate and obtain the working current of the LED particle string in order to achieve the expected color temperature after light mixing

The computer calculates _I'c and _I'w using the following formulas derived from steps 200 and 300:

CCT=(Φc×CCTc+Φw×CCTw)/φ,

Φc=I′c× _ηc ,Φw= _I′w ×ηw;

CCTc= _0.331I'c +6557, CCTw= _0.06I'w +2956;

Wherein, φ=Φc+Φw, Φc=Ic×ηc, Φw=Iw×ηw, ηc is the luminous light effect of the set LED particle string A, and ηw is the set LED luminous light effect of the LED particle string B;

Step 500, obtain the mixed light whose color temperature is CCT and luminous flux is φ

After obtaining _I′c and _I′w , the computer queries the relational table, obtains the dimming signal and color temperature signal pair corresponding to _I′c and _I′w and sends them to the single-chip microcomputer, so that the LED particle string A follows the working current I′ _c works, the LED particle string B works according to the working current I′ _w , and obtains the mixed light with the color temperature of CCT and the luminous flux of φ.

In this embodiment, the rated color temperature of each LED particle in the LED particle string A is 6500K, the rated color temperature of each LED particle in the LED particle string B is 3000K, ηc is equal to ηw, and the operating current Ic of the LED particle string A is 100mA The step size of the LED particle string B gradually increases from 0 to Imax; the working current Iw of the LED particle string B gradually increases from 0 to Imax according to the step size of 95mA.

The usual color temperature compensation method is as follows:

Set the rated color temperature of 6500K LED particle string A as CCT1, operating current I1, and luminous flux as Φ1, and the rated color temperature of 3000K LED particle string B as CCT2, operating current I2, and luminous flux as Φ2. Then the color temperature after light mixing is the weighted average of the luminous flux of the two color temperatures:

CCT＝(Φ1×CCT1+Φ2×CCT2)/(Φ1+Φ2)

Wherein Φ1=I1×η1, Φ2=I2×η2, η1 is the luminous efficacy of the first group of LEDs, and η2 is the luminous efficacy of the second group of LEDs.

To obtain the expected color temperature of CCT after light mixing, adjust the values of I1 and I2 to make the equation true. However, CCT is only the color temperature after light mixing in an ideal state. There is a gap between the actual color temperature and the expected color temperature CCT. 200K error.

As shown in Figure 4, the input voltage Vin drives two LED particle strings A and B through two DC drivers; the single-chip microcomputer receives external dimming signals and toning signals, decodes and calculates them, and outputs two PWM control signals, and PWM1 passes through R1 , C1, R2 filter, PWM2 is filtered by R3, C2, R4, and the DC voltage DIM1 and DIM2 are respectively given to 2 DC drivers. 2 The driver can output a certain DC current according to the input analog voltage to drive the LED particle string to work stably. The duty cycle of the output PWM1 and PWM2 of the microcontroller is corresponding to _I'c and _I'w , thus correcting the effect of the color temperature drift caused by the change of the working current.

The error between the actual output color temperature and the expected color temperature CCT after light mixing in the present invention is 5K; therefore, the present invention has the characteristic that the deviation between the color temperature of the mixed light actually obtained after light mixing and the expected color temperature is small.

It should be understood that this embodiment is only used to illustrate the present invention but not to limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Claims (6)

1. A color temperature compensation method for an LED lamp, characterized in that the LED lamp comprises a single-chip microcomputer (1), a filter circuit (2) and 2 DC drivers (3) electrically connected in sequence, and also includes a connection with the 2 DC drivers The LED particle string A of the cool color temperature and the LED particle string B of the warm color temperature are respectively electrically connected, and the LED particle strings of the two groups include the same number of serial LED particles (4), and the single-chip microcomputer is electrically connected to the computer through a data line; the color temperature compensation The method includes the following steps: (1-1) Set the color temperature of the LED particle string A as CCTc, and the operating current as Ic; the color temperature of the LED particle string B as CCTw, and the operating current as Iw; Set the working current of the LED particle string A when the color temperature is CCT and the luminous flux is φ after mixing the light from the LED particle string A and B is I′ _c , and the working current of the LED particle string B is I′ _w ; (1-2) Let Imax be the maximum operating current of LED particle strings A and B, and there are several pairs of dimming signals and color temperature signals stored in the computer, and the values and dimming signals of I′ _c and I′ _w are recorded and the corresponding relationship table of the corresponding relationship between the color temperature signal pair; The computer makes the working current Ic of the LED particle string A gradually increase from 0 to Imax by changing the dimming signal and the color temperature signal pair sent to the single-chip microcomputer, and uses a color temperature measuring instrument to detect the output color temperature CCTc of the LED particle string A, and uses the computer Select at least 8 Ic and the corresponding output color temperature CCTc to form a point (Ic, CCTc), and draw the curve 1 of the output color temperature changing with the operating current Ic in the computer; Make the operating current Iw of the LED particle string B gradually increase from 0 to Imax, use a color temperature measuring instrument to detect the output color temperature CCTw of the LED particle string B, and use a computer to select at least 8 Iw and corresponding output color temperature CCTw to form points (Iw, CCTw ), draw the curve 2 of the output color temperature changing with the operating current Iw in the computer; (1-3) The computer performs linear fitting on curve 1 and curve 2 respectively, and obtains the linear fitting formula CCTc=d ₁ I _c +d ₂ corresponding to curve 1, The linear fitting formula corresponding to curve 2 CCTw=g ₁ I _w +g ₂ ; where, d ₁ , d ₂ , g ₁ , and g ₂ are all non-zero real numbers; (1-4) Set the luminous flux of LED particle string A after light mixing as Φc, and the luminous flux of LED particle string B as Φw, Then the color temperature CCT after light mixing=(Φc×CCTc+Φw×CCTw)/(Φc+Φw); (1-5) The computer utilizes the following formula derived according to steps (1-3) and (1-4) to calculate _I′c and _I′w : CCT=(Φc×CCTc+Φw×CCTw)/φ, Φc=I′c× _ηc ,Φw= _I′w ×ηw; CCTc=d ₁ I′ _c +d ₂ , CCTw=g ₁ I′ _w +g ₂ ; Wherein, φ=Φc+Φw, Φc=Ic×ηc, Φw=Iw×ηw, ηc is the luminous light effect of the set LED particle string A, and ηw is the set LED luminous light effect of the LED particle string B; (1-6) After obtaining _I'c and _I'w , the computer queries the relational table, and obtains the dimming signal and color temperature signal pair corresponding to _I'c and _I'w and sends them to the single-chip microcomputer, so that the LED particle string A Working according to the working current I' _c , LED particle string B working according to the working current I' _w , to obtain the mixed light with color temperature CCT and luminous flux φ. 2. The color temperature compensation method of an LED lamp according to claim 1, wherein the rated color temperature of each LED particle in the LED particle string A is 6500K, and the rated color temperature of each LED particle in the LED particle string B is 3000K. 3. The color temperature compensation method of an LED lamp according to claim 1, wherein the rated color temperature of each LED particle in the LED particle string A is 6500K, and the rated color temperature of each LED particle in the LED particle string B is 2700K. 4. The method for color temperature compensation of LED lamps according to claim 1, wherein said ηc is equal to ηw. 5. The color temperature compensation method of an LED lamp according to claim 1, wherein the working current Ic of the LED particle string A in the step (1-2) is gradually increased from 0 to Imax according to a step size of 80 to 105mA high. 6. The method for color temperature compensation of LED lamps according to claim 1, characterized in that, in the step (1-2), the operating current Iw of the LED particle string B gradually increases from 0 to Imax according to a step size of 90 to 105mA high.