WO2020237427A1

WO2020237427A1 - Led soft light strip circuit with which brightness and color temperature are adjusted simultaneously and soft light strip

Info

Publication number: WO2020237427A1
Application number: PCT/CN2019/088339
Authority: WO
Inventors: 薛丹琳
Original assignee: 深圳迪亚士照明科技有限公司
Priority date: 2019-05-24
Filing date: 2019-05-24
Publication date: 2020-12-03

Abstract

Disclosed are an LED soft light strip circuit with which the brightness and color temperature are adjusted simultaneously and a soft light strip. The circuit comprises: a positive electrode bus (26), a negative electrode bus (27), and several LED light-emitting components (22). Each LED light-emitting component comprises: a first LED light string (23) and a second LED light string (24) connected in parallel, a voltage-controlled semiconductor switch transistor (5) connected in the second LED light string, and a delay circuit (25) connected to a control end of the switch transistor. LEDs in either LED light strings are identical in number but different in color temperature. The soft light strip comprises a tape-like substrate and the soft light strip circuit. The positive electrode bus and the negative electrode bus respectively are provided on the rear side of the substrate in the lengthwise direction of the substrate. The several LED light-emitting components are provided on the front side of the substrate in the lengthwise direction of the substrate. A power supply for the present circuit is easy to match, no chromatic aberration is produced with an increase in the length of the light strip, and the consistency of color temperature adjustments is great.

Description

A LED flexible light bar circuit and flexible light bar for synchronously adjusting brightness and color temperature

Technical field

The invention relates to the field of LED lighting, in particular to a circuit for adjusting the brightness and color temperature of an LED flexible light bar, and to a flexible light bar adopting this circuit.

Background technique

The traditional adjustable brightness and color temperature LED flexible light bar adopts two different color temperature LED circuits to adjust separately. The circuit structure requires three power input lines. Such a circuit needs to be equipped with a dedicated dimming and color temperature controller, and Dimming and color temperature have to be adjusted separately, which is not convenient for installation or modification, and adjustment is not convenient.

To this end, people have proposed improvements. Specifically, the number of LEDs in the two LED circuits with different color temperatures is set to be different to form an unbalanced structure. As shown in Figure 1, when the external dimmable LED driving power supply 11 is in a high-brightness output state, its output voltage is high, The current is large, the driving current of the first color temperature LED circuit 12 and the second color temperature LED circuit 13 are equivalent, and the mixed color temperature is higher; when the external dimmable LED driving power supply 11 is in a low-brightness output state, the output voltage is lower and the first The driving current drop of the color temperature LED circuit 12 is much larger than the driving current drop of the second color temperature LED circuit 13. The proportion of low color temperature in the mixed light emitted by the LED light bar increases, so that the overall color temperature of the mixed light is reduced, thereby achieving The purpose of dimming while adjusting the color temperature. In this way, as long as two power input lines, no special dimmable and color temperature controller is needed, the original dimmable function circuit can be connected to realize the function of dimming and color temperature. However, such a circuit also has some defects: 1. It adopts a voltage regulation method, but the voltage regulation LED dimming power supply has been eliminated in the market, which makes it difficult for the user to find a power supply for the flexible light bar. 2. The color temperature change is directly related to the voltage. When the cascade length of the flexible light bar is long, the color difference will occur due to the inconsistent voltage before and after the flexible light bar, that is, the color difference.

Summary of the invention

The purpose of the present invention is to provide a circuit for adjusting the brightness and color temperature of the flexible LED light bar to solve the above-mentioned defects in the prior art.

To achieve the above objectives, the technical solutions adopted by the present invention are as follows:

A circuit for synchronously adjusting brightness and color temperature of an LED flexible light bar, which can be adapted to an external constant voltage PWM output dimming power supply (21), the LED flexible light bar circuit includes:

Positive bus (26);

Negative bus (27); and

A number of LED lighting components (22), each of which includes:

The first LED light string (23) is composed of a first current-limiting resistor (2) and a number of first LEDs (1) in series. One end of the first LED light string is connected to the positive bus bar, and the other end is connected to the The negative bus is connected;

The second LED light string (24) is composed of a second current-limiting resistor (4) and a number of second LEDs (3) in series, the second LED light string (24) and the first LED light string (23) Connected in parallel, the second LED (3) and the first LED (1) have the same number and different color temperature values;

A voltage-controlled semiconductor switch tube (5) connected to the second LED light string (24); and

The delay circuit (25) includes a capacitor (6), a charging resistor (7) and a discharging resistor (8). The capacitor and the discharging resistor are connected in parallel and then connected across the control terminal of the switch tube and the negative bus In between, the charging resistor is connected across the control end of the switch tube and the positive bus.

The driving current I _{WW of the} above-mentioned first LED light string changes with the power supply voltage V _DD , and the driving current I _{CW of the} second LED light string is generated by the switching tube and the delay circuit as compared with the driving current I _WW A delay time t _A. In this way, when in use, the positive bus and the negative bus are connected to an external constant voltage PWM output dimming power supply, and by controlling the duty cycle of the PWM waveform of the power supply voltage V _DD , not only the brightness of the LED light-emitting assembly can be adjusted And due to the above-mentioned delay time t _A , when the duty ratio of the PWM waveform changes, the duration of the high level of the drive current I _CW t _CW.ON and the duration of the high level of the drive current I _WW t _ON are The ratio t _CW.ON /t _ON is changed, so that the overall color temperature of the mixed light emitted by the LED light-emitting assembly is changed, so as to achieve the purpose of adjusting the brightness and color temperature step by step.

In the above solution, the number of LEDs in the two LED light strings is the same, and the brightness and color temperature are adjusted synchronously by adjusting the duty cycle of the PWM waveform. The power supply voltage VDD remains constant, and the length of the flexible light bar will not produce color difference. The above can be cascaded to any length within the allowable range of the dimming power supply without causing color difference.

In the above solution, voltage-controlled semiconductor switching tubes are used, and the switching tubes will not cause deviations in the delay time t _A , so the color temperature adjustment consistency is good, and the product qualification rate is high.

In the above-mentioned brightness and color temperature synchronous adjustment of the LED flexible light bar circuit, preferably, the voltage control type switch tube is a MOS tube.

The present invention also provides a flexible LED light bar with synchronous adjustment of brightness and color temperature. The flexible LED light bar includes: a strip substrate; and the above-mentioned LED flexible light bar circuit; the positive bus and the negative bus are respectively along the The length direction of the substrate is arranged on the back surface of the substrate, and a plurality of the LED light-emitting components are arranged on the front surface of the substrate along the length direction of the substrate.

In the aforementioned brightness and color temperature synchronous adjustment of the LED flexible light bar, preferably, the voltage control type switch tube is a MOS tube.

In the above-mentioned brightness and color temperature synchronous adjustment of the LED flexible light bar, preferably, the surface of the substrate is provided with a mark between the adjacent LED light-emitting components.

In the above-mentioned brightness and color temperature synchronous adjustment of the LED flexible light bar, preferably, the positive bus bar and the negative bus bar are strip-shaped metal foils. After the light bar is cut along the mark, the positive bus bar and the The negative bus bar constitutes a contact electrode at the cut portion and is used to connect with an external constant voltage PWM output dimming power supply.

Compared with the prior art, the present invention has at least the following beneficial effects:

As long as there are two input power lines, only the constant voltage PWM output dimming power supply commonly used in the market can realize the synchronization adjustment effect of brightness and color temperature, and can be connected to any length within the allowable range of the dimming power supply. Cause chromatic aberration. At the same time, the consistency of color temperature adjustment is good, and the product qualification rate is high.

Description of the drawings

Figure 1 is a circuit diagram of an LED flexible light bar with adjustable light and color temperature in the prior art;

Figure 2 is a circuit diagram of the LED flexible light bar of the present invention;

Figure 3 shows the waveform of the working voltage V _DD of the corresponding flexible light bar, the waveform of the driving current I _WW of the first LED string and the waveform of the second LED light when the external constant voltage PWM output dimming power supply is output with different dimming rates. The waveform of the drive current I _CW of the string;

Reference signs: 1. First LED; 2. First current-limiting resistor; 3. Second LED; 4. Second current-limiting resistor; 5. Voltage-controlled semiconductor switch tube; 6. Capacitor; 7. Charging resistor; 8. Discharge resistance; 11. External dimmable LED drive power supply; 12. First color temperature LED circuit; 13. Second color temperature LED circuit; 21. External constant voltage PWM output dimming power supply; 22. LED light-emitting components; 23. The first LED string; 24. The second LED string; 25. Delay circuit; 26. Positive bus; 27. Negative bus.

Detailed ways

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

Please refer to FIG. 2, this circuit for adjusting the brightness and color temperature of the flexible LED light bar includes: a positive bus bar 26, a negative bus bar 27, and a number of LED light-emitting components 22.

Each LED light-emitting component 22 includes: a first LED light string 23, a second LED light string 24, a voltage-controlled semiconductor switch tube 5, and a delay circuit 25.

The first LED light string 23 is composed of a first current-limiting resistor 2 and a plurality of first LEDs 1 connected in series, in a strip shape. One end of the first LED light string 23 is connected to the positive bus 26 and the other end is connected to the negative bus 27.

The second LED light string 24 is composed of a second current-limiting resistor 4 and a number of second LEDs 3 in series, in a strip shape. The second LED light string 24 is connected in parallel with the first LED light string 23. The number is the same as the number of the first LED1, and the color temperature value of the second LED3 is different from the color temperature value of the first LED1. Specifically, in this embodiment, the color temperature value of the first LED1 is smaller than the color temperature value of the second LED3, but the present invention can also be designed in reverse.

The voltage controlled semiconductor switch tube 5 is connected to the second LED light string 24, and the voltage controlled semiconductor switch tube 5 is preferably a MOS tube.

The delay circuit 25 includes a capacitor 6, a charging resistor 7 and a discharging resistor 8. The capacitor 6 and the discharging resistor 8 are connected in parallel between the control terminal of the switch tube 5 and the negative bus 27, and the charging resistor 7 is connected across the Between the control end of the switch tube 5 and the positive bus 26.

As shown in Figure 3, the output voltage of the external constant voltage PWM output dimming power supply 21 is a PWM waveform with a period t _PWM , and the dimming rate is similar to the duty cycle t _{D of the} waveform. When the output dimming rate of the external constant voltage PWM output dimming power supply 21 is 100%, the duty cycle t _D of the output PWM voltage is 100%, the flexible light bar working voltage V _DD is a continuous output, and the first LED string 23 The driving current I _{WW of the} second LED light string 24 and the driving current I _{CW of the} second LED string 24 are also continuous maximum states, and the two color temperatures maintain a fixed ratio, the soft light bar presents the highest brightness and the color temperature is the first LED light The mixed color temperature of the string 23 and the second LED light string 24. The period t _PWM can be any value between 0.0025 milliseconds and 10 milliseconds.

As shown in Fig. 2, the minimum value of the driving current I _WW of the first LED light string 23 is 0, and the maximum value I _WW.max is determined by the light bar operating voltage V _DD , the sum of the forward voltages of all the first LED1 and the first limit. A constant determined by the resistance value of the current resistor 2; the minimum value of the driving current I _CW of the second LED string 24 is 0, and the maximum value I _CW.max is determined by the light bar working voltage _VDD , the sum of the forward voltages of all the second LED3, The resistance value of the second current limiting resistor 4 is a constant determined by the voltage drop between the drain and source of the MOS tube (the switch tube 5).

As shown in Figure 3, when the output dimming rate of the external constant voltage PWM output dimming power supply 21 is reduced, the duty cycle t _{D of the} flexible light bar working voltage V _DD also decreases, and the flexible light bar working voltage V _DD It is a PWM waveform with high and low voltage changes and the dot-to-space ratio t _D <100%. At this time, the driving current I _{WW of the} first LED light string 23 and the driving current I _CW of the second LED light string 24 have different waveforms.

As shown in Fig. 2, since the first LED light string 23 is directly connected to the power supply through the first current limiting resistor 2, the driving current I _{WW of the} first LED light string 23 should follow the change of the power supply voltage V _DD , and its waveform is shown in Fig. As shown in 3, the duration of I _WW.max in any cycle t _PWM is t _ON .

As shown in Figure 2, since the work of the second LED light string 24 is controlled by the MOS tube (the switch tube 5), when the flexible light bar operating voltage V _{DD changes} from low to high, due to the A capacitor 6 is connected between the gate G and the source S, and the capacitor 6 has been fully discharged by the discharge resistor 8 when the flexible light bar operating voltage V _{DD is} at a low level. Therefore, the gate voltage u _GS cannot change suddenly, u _GS <the starting voltage U _T of the MOS tube, and the MOS tube is in the cut-off state, and the driving current I _{CW of the} second LED string 24 remains at 0; it is necessary to wait for the power supply to pass through the charging resistor 7 When the capacitor 6 is charged to u _GS ≥ U _T , the MOS tube is turned on, and the driving current I _{CW of the} second LED string 24 starts to follow the change of the power supply voltage V _DD ; at this time, the driving current I _{CW of the} second LED string 24 A fixed delay time is generated relative to the driving current I _{WW of the} first LED light string 23, as shown in FIG. 3 t _A. Therefore, the duration of I _{CW.max in} any cycle t _PWM is t _CW.ON =t _ON -t _A.

It can be known from the LED lighting principle and the PWM dimming principle that the luminous brightness of the first LED light string 23 and the second LED light string 24 is proportional to the respective driving current and the on-time in the cycle. Since the maximum values of the driving currents I _WW.max and I _CW.max of the two color temperature lamp strings are constant, within a PWM pulse period t _PWM , the luminous brightness of the second LED lamp string 24 is _equal to that of the first LED lamp string 23 The ratio of luminous brightness is determined by t _CW.ON /t _ON , then t _CW.ON /t _ON = (1-t _A /t _ON ) (t _ON ≥ t _A ). Therefore, when the dimming rate decreases, the brightness decreases, and t _ON will also decrease. If t _CW.ON /t _ON decreases, the ratio of low color temperature among the two color temperatures of the soft light bar increases, and the soft light bar emits The overall color temperature of the mixed light becomes smaller. So as to achieve the purpose of weekly adjustment of brightness and color temperature.

As shown in FIG. 2, the light-emitting brightness of the second LED light string 24 and the light-emitting brightness of the first LED light string 23 are reversed to obtain the opposite color temperature change effect.

As shown in Figure 2, changing the parameters of the charging resistor 7 and the capacitor 6 will change the delay time generated by the driving current I _CW of the second LED string 24 relative to the driving current I _WW of the first LED string 23, as shown in the figure T _A shown in 3; thus changing the slope of the color temperature following the change in brightness. The delay time t _A can be any value between 0.001 milliseconds and 5 milliseconds.

It can be seen from the above that the present invention uses two LED light strings with different color temperatures to be connected in parallel to form an LED light-emitting assembly, and the two LED light strings with different color temperatures have the same number of LEDs. Among them, one LED light string directly emits light through a current limiting resistor, and the other LED light string is controlled by a MOS tube to emit light. By controlling the turn-on time of the MOS tube, the ratio of the luminous time of the low color temperature LED string and the high color temperature LED string of two LED strings with different color temperatures under different dimming rates is changed to achieve simultaneous dimming , The color temperature also changes, achieving the purpose of synchronous adjustment of brightness and color temperature.

In this way, as long as two input power lines are required, the constant voltage PWM output dimming power supply that is commonly used in the market can realize the synchronization adjustment effect of brightness and color temperature, and can be connected to any length within the allowable range of the dimming power supply. Will not cause color difference.

Since the voltage-controlled semiconductor switch tube is used, when the capacitor 6 is charged, the charging current will not be shunted by the switch tube and will not cause deviation of the delay time t _A , so the color temperature adjustment consistency is good, and the product qualification rate is high.

All the parts of the invention can find ready-made miniature packaging sizes, can be conveniently arranged on the flexible PCB, and have practical value.

A flexible light bar using the above-mentioned LED flexible light bar circuit structure, the flexible light bar includes a strip substrate, the positive bus bar and the negative bus bar are respectively arranged on the back of the substrate along the length direction of the substrate, The LED light-emitting assembly is arranged on the front surface of the substrate along the length direction of the substrate.

Further, a mark may be provided between the adjacent LED light-emitting components on the surface of the substrate. In this way, people can easily find the head and tail of the LED light-emitting assembly, and can quickly cut.

Further, the positive bus bar and the negative bus bar are made of strip-shaped metal foil. After the light bar is cut along the mark, the positive bus bar and the negative bus bar form a contact electrode at the cutting position, and the cut end After being plugged into the power output socket of the external constant voltage PWM output dimming power supply, the contact electrode contacts with the electrode in the power output socket to realize electrical connection. In this way, the flexible light bar can be used after being cut, and there is no need to install a plug.

The present invention has been described in detail through specific embodiments above. These detailed descriptions are only limited to helping those skilled in the art understand the content of the present invention, and should not be understood as limiting the protection scope of the present invention. Various modifications, equivalent transformations, etc., performed by those skilled in the art on the above solutions under the concept of the present invention should be included in the protection scope of the present invention.

Claims

A circuit for adjusting the brightness and color temperature of an LED flexible light bar can be adapted to an external constant voltage PWM output dimming power supply (21), and is characterized in that the LED flexible light bar circuit includes:

Positive bus (26);

Negative bus (27); and

A number of LED lighting components (22), each of which includes:

The first LED light string (23) is composed of a first current-limiting resistor (2) and a number of first LEDs (1) in series. One end of the first LED light string is connected to the positive bus bar, and the other end is connected to the The negative bus is connected;

The second LED light string (24) is composed of a second current-limiting resistor (4) and a number of second LEDs (3) in series, the second LED light string (24) and the first LED light string (23) Connected in parallel, the second LED (3) and the first LED (1) have the same number and different color temperature values;

A voltage-controlled semiconductor switch tube (5) connected to the second LED light string (24); and

The delay circuit (25) includes a capacitor (6), a charging resistor (7) and a discharging resistor (8). The capacitor and the discharging resistor are connected in parallel and then connected across the control terminal of the switch tube and the negative bus In between, the charging resistor is connected across the control end of the switch tube and the positive bus.
The LED flexible light bar circuit for synchronously adjusting brightness and color temperature of claim 1, wherein the switch tube is a MOS tube.
A LED flexible light bar with synchronous adjustment of brightness and color temperature, characterized in that the LED flexible light bar includes:

Ribbon substrate; and

The LED flexible light bar circuit of claim 1;

The positive bus bar and the negative bus bar are respectively arranged on the back surface of the substrate along the length direction of the substrate, and a plurality of the LED light emitting components are arranged on the front surface of the substrate along the length direction of the substrate.
The LED flexible light bar with synchronous adjustment of brightness and color temperature according to claim 3, wherein the switch tube is a MOS tube.
The LED flexible light bar with synchronous adjustment of brightness and color temperature according to claim 3, wherein the surface of the substrate is provided with a mark between the adjacent LED light-emitting components.
The LED flexible light bar according to claim 5, wherein the positive bus bar and the negative bus bar are strip-shaped metal foils. After the light bar is cut along the mark, the The positive bus bar and the negative bus bar form a contact electrode at the cut portion and are used to connect with an external constant voltage PWM output dimming power supply.