Multi-color temperature tunable light illumination device

Abstract

The application discloses a multi-color-temperature adjustable light illumination device, comprising: a multi-path LED string, comprising at least two paths of LED strings connected in parallel with each other, the color temperatures of the LED strings being different from each other, each path of the LED strings being configured to be connected between a positive terminal and a negative terminal or connected between the positive terminal and the negative terminal via one or more auxiliary elements; a color temperature stabilizing module, connected in series to at least two paths of the LED strings in the multi-path LED string, the color temperature stabilizing module comprising one of a transistor unit, a current mirror unit and a standard current source unit; a switching module, connected to the multi-path LED string, the switching module selectively switching a current path of each path of the LED strings in the multi-path LED string to the positive terminal or the negative terminal. The color temperature stabilizing module enables the mixed color temperature of the multi-color-temperature illumination device to always maintain a stable color temperature during dimming, while keeping the illumination device low in cost.

Description

Technical Field

[0001] This application relates to color temperature adjustment of lighting devices, and in particular, to a multi-color temperature dimmable lighting device that can maintain a stable color temperature during dimming. Background Technology

[0002] For dimmable lighting fixtures with multiple color temperatures, the common method is to achieve multi-color temperature adjustment by mixing LEDs of different color temperatures. For example, by adjusting the current ratio, 2700K and 6500K LEDs can be mixed to produce different color temperatures such as 2700K, 3000K, 4000K, 5000K, and 6500K. However, when the lighting fixture undergoes dimming, especially during the process of adjusting from high brightness to low brightness (e.g., 10%), the dynamic resistance of the LED increases as the current decreases. Therefore, at intermediate color temperature levels (e.g., 3000K and 5000K), dimming to low brightness causes a significant shift in the color temperature of the lighting fixture, making it difficult to maintain color temperature stability during dimming.

[0003] Therefore, an improved circuit design is desired that can maintain a stable color temperature during dimming without increasing the cost of the lighting device, and can even lower the color temperature as needed to achieve warm dimming when the brightness of the lighting device decreases. Utility Model Content

[0004] This application is made in view of the above-mentioned problems. The main purpose of this application is to provide a multi-color temperature dimmable lighting device with an improved circuit design, so as to solve the technical problem that the mixed color temperature of the multi-color temperature lighting device is difficult to maintain stable during the dimming process, resulting in a decrease in the lighting performance of the lighting device and a degradation of the user experience.

[0005] To achieve the above objectives, according to one aspect of this application, a multi-color-temperature dimmable lighting device is provided, characterized in that it comprises: a multi-LED string, including at least two LED strings connected in parallel with each other, the LED strings having different color temperatures, each LED string being configured to be connected between a positive terminal and a negative terminal or connected between the positive and negative terminals via one or more auxiliary elements; a color-temperature stabilization module, connected in series with at least two of the multi-LED strings, the color-temperature stabilization module including one of a transistor unit, a current mirror unit, and a standard current source unit; and a switching module, connected to the multi-LED strings, the switching module selectively switching the current path of each LED string in the multi-LED strings to the positive or negative terminal.

[0006] In this way, a multi-color-temperature dimmable lighting device is provided, which has a color-temperature stabilization module that can further stabilize the mixed color temperature during the dimming process of the dimmable lighting device. This ensures that when the lighting device is dimmed to a low brightness, even if the resistance of the connected LED string increases as the current flowing through it decreases, the series-connected color-temperature stabilization module can compensate for the impact of the resistance change of the LED string on the current ratio of different LED strings. This reduces the change in the current ratio of different LED strings during the dimming process, thereby maintaining the stability of the preset mixed color temperature and improving the lighting performance and user experience of the lighting device.

[0007] Furthermore, according to one embodiment of this application, in the case where the color temperature stabilization module includes a transistor unit and the multi-channel LED string consists of a first LED string having a first color temperature and a second LED string having a second color temperature different from the first color temperature, the color temperature stabilization module consists of a common resistor and a transistor unit.

[0008] Furthermore, according to one embodiment of this application, the transistor unit includes a first transistor and a second transistor, a first terminal of a common resistor is connected to the positive terminal, the first transistor is connected in series to a first LED string, the second transistor is connected in series to a second LED string, and the bases of the first transistor and the second transistor are both connected to the second terminal of the common resistor.

[0009] In this way, by connecting each LED string in series with a transistor unit, the series-connected transistor unit compensates for the impact of resistance variations in the LED string on the current ratio flowing through different LED strings, thereby reducing the variation in the current ratio of different LED strings during dimming and maintaining the stability of the preset mixed color temperature.

[0010] Furthermore, according to one embodiment of this application, the base-emitter voltage of the first transistor is equal to the base-emitter voltage of the second transistor.

[0011] In this way, by connecting each LED string in series with a transistor unit and making the base-emitter voltages of the series-connected transistor units the same, the influence of the resistance variation of the LED string on the current ratio flowing through different LED strings is compensated, thereby reducing the change in the current ratio of LED strings in different paths during dimming and maintaining the stability of the preset mixed color temperature.

[0012] Furthermore, according to one embodiment of this application, when the color temperature stabilization module includes the current mirror unit and the multi-channel LED string is composed of a first LED string having a first color temperature and a second LED string having a second color temperature different from the first color temperature, the color temperature stabilization module is composed of a ratio setting unit, the current mirror unit, and a reference current unit.

[0013] Further, according to one embodiment of this application, the first input terminal of the current mirror unit is connected to the ratio setting unit to receive a first ratio setting command for the first LED string and a second ratio setting command for the second LED string; the second input terminal of the current mirror unit is connected to the reference current unit to receive a reference current signal; the first output terminal of the current mirror unit is connected to the first LED string; the second output terminal of the current mirror unit is connected to the second LED string; the current mirror unit outputs a first current determined based on the first ratio setting command and the reference current signal to the first LED string; and the current mirror unit outputs a second current determined based on the second ratio setting command and the reference current signal to the second LED string.

[0014] In this way, the current mirror can provide an output current that is highly matched with the reference current (input current). This not only compensates for the influence of the resistance change of the LED string on the current ratio of different LED strings, but also reduces the change of the current ratio of different LED strings during dimming to maintain the stability of the preset mixed color temperature. In addition, the current mirror has high precision and is easy to integrate at high density.

[0015] Furthermore, according to one embodiment of this application, the reference current signal of the reference current unit changes dynamically during the dimming process of the dimmable lighting device.

[0016] In this way, the reference current signal of the reference current unit changes dynamically during the dimming process of the dimmable lighting device, thereby enabling the feedback mechanism to reduce the change in the current ratio of different LED strings during the dimming process, and thus maintain the stability of the preset mixed color temperature.

[0017] Furthermore, according to one embodiment of this application, when the color temperature stabilization module includes a standard current source unit and the multi-channel LED string is composed of a first LED string having a first color temperature and a second LED string having a second color temperature different from the first color temperature, the color temperature stabilization module is composed of the standard current source unit, a ratio setting unit, a first reference current unit, and a second reference current unit.

[0018] Further, according to one embodiment of this application, the standard current source unit includes a first standard current source and a second standard current source. A first input terminal of the first standard current source is connected to the ratio setting unit to receive a first ratio setting command for the first LED string. A first input terminal of the second standard current source is connected to the ratio setting unit to receive a second ratio setting command for the second LED string. A second input terminal of the first standard current source is connected to the first reference current unit to receive a first reference current signal. A second input terminal of the second standard current source is connected to the second reference current unit to receive a second reference current signal. An output terminal of the first standard current source is connected to the first LED string. An output terminal of the second standard current source is connected to the second LED string. The first standard current source outputs a first current determined based on the first ratio setting command and the first reference current signal to the first LED string. The second standard current source outputs a second current determined based on the second ratio setting command and the second reference current signal to the second LED string.

[0019] In this way, a standard current source can accurately replicate or scale the current, thereby providing an output current that is highly matched to the reference current (input current), or a multi-channel output current that is scaled proportionally. This not only compensates for the impact of resistance variations in the LED string on the current ratio flowing through different LED strings, reducing the variation in the current ratio of different LED strings during dimming to maintain the stability of the preset mixed color temperature, but also features low loss, high efficiency, and ease of high-density integration of the standard current source.

[0020] Furthermore, according to one embodiment of this application, the switching module selectively switches the current path of each LED string in the multi-channel LED string to the positive or negative terminal, including: the switching module directly connects at least one LED string in the multi-channel LED string between the positive and negative terminals according to the user's operation instruction, or connects at least one LED string in the multi-channel LED string between the positive and negative terminals via one of the auxiliary components.

[0021] In this way, by enabling LED strings to be connected to resistive elements with different resistance values, one LED string can be connected in parallel with other LED strings according to different resistance / current ratios, thereby generating more mixed color temperature levels for the lighting device. These mixed color temperatures can remain stable during dimming as needed, or achieve a warm dimming effect as dimming is reduced.

[0022] Furthermore, according to one embodiment of this application, the switching module is a mechanical switching element or an electronic switching element, wherein the mechanical switching element includes a single-pole switch or a multi-pole switch.

[0023] In this way, by combining multi-pole or single-pole switches, the color temperature of the dimmable lighting device of this application can be switched.

[0024] In this application embodiment, a dimmable lighting device for multiple color temperatures is provided to at least solve the technical problem in the prior art that the mixed color temperature of multiple color temperature lighting devices is difficult to maintain stable during the dimming process, resulting in a decrease in the lighting performance of the lighting device. This achieves the technical effect of maintaining a stable mixed color temperature of the multiple color temperature lighting device during the dimming process, while maintaining the low cost of the lighting device. Attached Figure Description

[0025] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0026] Figure 1 This is a schematic diagram showing the measurement results of the color temperature change with brightness in a traditional multi-color temperature dimmable lighting device.

[0027] Figure 2 This is a schematic diagram of a multi-color temperature dimmable lighting device according to an embodiment of this application;

[0028] Figure 3 This is a schematic diagram of a multi-color temperature dimmable lighting device according to the first embodiment of this application;

[0029] Figure 4 This is a schematic diagram of a color temperature stabilization module according to the first embodiment of this application;

[0030] Figure 5 This is a schematic diagram of a color temperature stabilization module according to the second embodiment of this application;

[0031] Figure 6 This is a schematic diagram of a color temperature stabilization module according to a third embodiment of this application.

[0032] The above figures include the following reference numerals:

[0033] 10: Multi-color temperature dimmable lighting device

[0034] 102: Power Supply

[0035] 104: Rectifier Circuit

[0036] 106: Constant Current Driver Chip

[0037] 108: Color Temperature Stabilization Module

[0038] 110: Switching Module

[0039] 302: Power supply

[0040] 304: Common Resistor

[0041] 306: First transistor

[0042] 308: Second transistor

[0043] 310: Common Connection Point

[0044] 312, 314: Resistors

[0045] 402: Ratio Setting Unit

[0046] 404: Reference Current Unit

[0047] 406: Current Mirror Unit

[0048] 408: First LED string

[0049] 410: Second LED string

[0050] 502: First Reference Current Unit

[0051] 504: Ratio Setting Unit

[0052] 506: Second Reference Current Unit

[0053] 508: First Standard Current Source

[0054] 510: Second Standard Current Source

[0055] 512: First LED string

[0056] 514: Second LED string Detailed Implementation

[0057] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present application.

[0058] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that comprises a series of steps, modules, or units is not necessarily limited to those explicitly listed, but may include other steps, modules, or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0059] In this application, a dimmable lighting device refers to a lighting device whose brightness can be adjusted by regulating the average current flowing through the LED string through various means such as controlling the magnitude, phase, and pulse duty cycle of the output voltage or current. Dimmable lighting devices can employ various methods to achieve dimming, including TRIAC dimming, intelligent dimming (including PWM dimming and analog dimming), and adjustable resistor dimming. This application does not limit the dimming method. For example, a dimmable lighting device can use a phase-cut dimmer, also known as a phase-controlled dimmer, which is an electronic device widely used to adjust the brightness of AC-powered lighting equipment. The main function of a phase-cut dimmer is to control the brightness of the lamp by changing the conduction angle (i.e., phase angle) of a sine wave. Specifically, within each AC cycle, the phase-cut dimmer delays the conduction time of the sine wave, thereby cutting off a portion of the waveform in the first or second half, reducing the effective value of the voltage and current actually supplied to the bulb, thus achieving brightness adjustment. Through the phase control described above, phase-cut dimmers can effectively reduce bulb power consumption, achieving energy savings. Phase-cut dimmers can provide smooth brightness adjustment within a certain range, from full brightness to off, which can enhance the comfort and ambiance of the lighting environment in many situations.

[0060] This application proposes a dimmable lighting device with multiple color temperatures, incorporating LED strings of different color temperatures. The desired color temperature is achieved by adjusting the current ratio passing through these LED strings. In this application, each LED string consists of one or more LEDs.

[0061] In traditional dimmable lighting fixtures with multiple color temperatures, multi-color temperature adjustment is achieved by selectively connecting LED strings of different color temperatures in series with one of multiple resistors, thereby mixing these LED strings at different current ratios. For example, a traditional dimmable lighting fixture may include a first LED string with a color temperature of 2700K and a second LED string with a color temperature of 6500K. A traditional dimmable lighting fixture may also include a single-pole switch having a fixed terminal connected to the negative terminal of a power supply, a movable terminal connected to the fixed terminal, and multiple contacts. The movable terminal of the single-pole switch is configured to switch connections between the multiple contacts to activate only the first LED string, or only the second LED string, or directly connect the first and second LED strings in parallel, or connect a parallel circuit of the first LED string and the second LED string connected in series with a resistor, or connect a parallel circuit of the second LED string and the first LED string connected in series with a resistor. By operating the movable end of a single-pole switch to toggle connections between multiple contacts, the user can enable the lighting device to display five color temperatures: 2700K, 3000K, 4000K, 5000K, and 6000K. Thus, the lighting device can display the color temperature of the first LED string, the color temperature of the second LED string, or a mixed color temperature obtained by combining the first and second LED strings in different proportions.

[0062] When dimming a dimmable lighting device within a high brightness range (e.g., 80% to 100%), the current change caused by dimming has a relatively small impact on the dynamic resistance of the LEDs because the LEDs in the LED string are operating in the linear approximation region. However, when dimming from a high brightness range to a low brightness range (e.g., 1% to 30%, 5% to 30%, 10% to 30%, 10% to 20%), the current through the LEDs decreases significantly due to the lower brightness. At this point, the LEDs are operating in the exponential growth region, and the forward voltage of the LEDs decreases only slightly, resulting in a significant increase in the dynamic resistance of the LEDs.

[0063] When a lighting device dims from a higher brightness (e.g., 80%, 90%, 100%) to a lower brightness (e.g., 10%, 20%, 30%), the resistance of the LED strings increases significantly, while the resistance of the resistor connected in series with the LED strings remains constant. Therefore, compared to before dimming, the resistance ratio of the branch containing the first and second LED strings changes, resulting in a change in the current ratio flowing through the first and second LED strings. Consequently, the mixed color temperature also changes. Specifically, compared to before dimming, the proportion of current received by the LED strings that originally had relatively lower current increases after dimming, causing the mixed color temperature to shift towards the direction of the LED strings with relatively lower current.

[0064] Figure 1This is a schematic diagram showing the measurement results of color temperature changes with brightness in a traditional dimmable lighting device. Figure 1 The horizontal axis represents brightness, and the vertical axis represents color temperature (CCT). Curve g1' corresponds to a color temperature of 6500K, curve g2' to 5000K, curve g3' to 4000K, curve g4' to 3000K, and curve g5' to 2700K. For example... Figure 1 As shown, when the mixed color temperature is 3000K, as the dimming brightness decreases to lower levels (e.g., 10%, 20%, 30%, etc.), the color temperature deviates from 3000K towards higher color temperatures. Correspondingly, when the mixed color temperature is 5000K, as the dimming brightness decreases to lower levels (e.g., 10%, 20%, 30%, etc.), the color temperature deviates from 5000K towards lower color temperatures. This makes it difficult to maintain a stable mixed color temperature for the lighting fixture 100' during dimming.

[0065] For example, in a traditional dimmable lighting device, each LED string consists of 8 LEDs, the LED model is 2835, the forward voltage Vf is 18V, the rated power is 1W, the color temperature of the first LED string is 2700K and the color temperature of the second LED string is 6500K, the measured color temperature values ​​during the dimming process are shown in Table 1:

[0066] Table 1

[0067] dimming 2700K 3000K 4000K 5000K 6500K 100％ 2701 3080 3784 5139 6615 80％ 2690 3072 3743 5043 6484 50％ 2667 3077 3686 4853 6327 20％ 2642 3152 3611 4480 6243 10％ 2619 3392 3542 3778 6331

[0068] As shown in Table 1, with a mixed color temperature of 3000K, the actual mixed color temperature changes as follows during the dimming process from 100% to 80% to 50% to 20%: 3080K → 3072K → 3077K → 3152K. With a mixed color temperature of 5000K, the actual mixed color temperature changes as follows during the dimming process from 100% to 80% to 50% to 20%: 5139K → 5043K → 4853K → 4480K. Clearly, as... Figure 1 As shown in Table 1, when the mixed color temperature is 3000K, as the dimming brightness decreases to lower levels (e.g., 10%, 20%, 30%, etc.), the color temperature deviates from 3000K towards higher color temperatures. Furthermore, when the mixed color temperature is 5000K, as the dimming brightness decreases to lower levels (e.g., 10%, 20%, 30%, etc.), the color temperature deviates from 5000K towards even lower color temperatures. This makes it difficult to maintain a stable mixed color temperature for the lighting fixture during dimming.

[0069] This application is made in view of the above circumstances. The purpose of this application is to provide a multi-color temperature dimmable lighting device with an improved circuit design, which can keep the mixed color temperature of the multi-color temperature lighting device stable during the dimming process, and also keep the lighting device at low cost.

[0070] To this end, this application provides a multi-color-temperature dimmable lighting device, comprising: a multi-LED string, including at least two LED strings connected in parallel with each other, the at least two LED strings having different color temperatures, each LED string being configured to be connected between the positive and negative terminals of a power supply or connected between the positive and negative terminals of a power supply via a resistor; a color-temperature stabilizing module, connected in series to each of the multi-LED strings, the color-temperature stabilizing module including one of a transistor unit, a current mirror unit, and a standard current source unit; and a switching module, connected to the multi-LED string, the switching module selectively switching the current path of each LED string in the multi-LED string to the positive or negative terminal of the power supply.

[0071] In the dimmable lighting device with multiple color temperatures according to this application, due to the configuration of the aforementioned color temperature stabilization module, especially the configuration of one of the transistor unit, current mirror unit, and standard current source unit connected in series to each of the multiple LED strings, when each of the multiple LED strings is connected to the negative terminal of the power supply via the color temperature stabilization module and optionally via a resistor to generate the desired mixed color temperature, when the lighting device is at high brightness, the current flowing through the corresponding LED string and the color temperature stabilization module is large. At this time, the resistance of one of the transistor unit, current mirror unit, and standard current source unit is small, and the current flowing through these LED strings will be mainly determined by the resistance of the LED strings connected in the circuit and the resistance of the resistive element connected in series to the LED strings. As the brightness of the lighting device decreases due to dimming, especially when the brightness of the lighting device is reduced to a lower brightness, the resistance of the LED strings will increase significantly with the decrease of current, and the influence of the resistive element connected in series to the LED strings on the current becomes less significant. However, the resistance of one of the transistor unit, current mirror unit, or standard current source unit in each LED string connected in series in a multi-LED string also increases significantly as the current decreases. Therefore, by appropriately selecting the parameters / models of the transistor unit, current mirror unit, and standard current source unit, during dimming at lower brightness, the transistor unit, current mirror unit, and standard current source unit can offset the effect of the increased resistance of the LED string on the current ratio of the branch containing that LED string compared to the branches containing other LED strings, so that the current ratio of the branch containing that LED string remains close to the current ratio of the branches containing other LED strings under high brightness conditions. This reduces the mixed color temperature deviation of the lighting device during dimming, keeping the mixed color temperature of the lighting device stable during dimming.

[0072] Next, refer to Figures 2 to 6 Specific embodiments of this application are described in detail. Figure 2 This is a schematic diagram of a multi-color temperature dimmable lighting device according to an embodiment of this application. Figure 3 This is a schematic diagram of a multi-color temperature dimmable lighting device according to the first embodiment of this application. Figure 4 This is a schematic diagram of a color temperature stabilization module according to the first embodiment of this application. Figure 5 This is a schematic diagram of a color temperature stabilization module according to a second embodiment of this application. Figure 6 This is a schematic diagram of a color temperature stabilization module according to a third embodiment of this application. It should be noted that, for simplicity, in... Figures 2 to 6 In this paper, multiple LED strings in a lighting device are shown as only two LED strings. However, those skilled in the art will understand that in the embodiments of this application, the dimmable lighting device may contain more LED strings.

[0073] like Figure 2 As shown, the multi-color temperature dimmable lighting device 10 according to an embodiment of this application includes two LED strings. To distinguish them, in... Figure 2 The diagram shows a first LED string consisting of C1, C2, C3, C4, C5, C6, C7, and C8, and a second LED string consisting of W1, W2, W3, W4, W5, W6, W7, and W8. The first and second LED strings, connected in parallel, have different color temperatures. Each of the first and second LED strings is configured to be connected between the positive and negative terminals of the power supply 102. The multi-color-temperature dimmable lighting device 10 also includes a color-temperature stabilization module 108, which is connected in series to the first and second LED strings, as shown in the following reference. Figures 3 to 6 In further detail, the color temperature stabilization module 108 may include one of a transistor unit, a current mirror unit, or a standard current source unit. Furthermore, the multi-color temperature dimmable lighting device 10 may also include a rectified current circuit 104 and a constant current drive chip 106. The rectified circuit 104 may be configured to supply rectified DC current to the LED strings. Furthermore, the multi-color temperature dimmable lighting device 10 may also include a switching module 110 connected to the first LED string and the second LED string, the switching module 110 selectively switching the current path of each LED string in the first and second LED strings to the negative terminal of the power supply 102. Figure 2As shown, the switching module 110 uses DIP switches, which have five DIP travel distances: T1 indicates a short circuit between pins 1 and 4, and between pins 9 and 12; T2 indicates a short circuit between pins 2 and 4, and between pins 9 and 11; T3 indicates a short circuit between pins 3 and 4, and between pins 9 and 10; T4 indicates a short circuit between pins 5 and 4, and between pins 9 and 8; and T5 indicates a short circuit between pins 6 and 4, and between pins 9 and 7. Figure 2 As shown, the first LED string can have the following current paths to the negative terminal of power supply 102: the first LED string is directly connected to pins 6 and 7 inside the terminal; the first LED string is connected to pin 8 inside the terminal via resistors R11 and R12; the first LED string is connected to pin 10 inside the terminal via resistors R9 and R10; the first LED string is connected to pin 11 inside the terminal via resistors R7 and R8. The second LED string can have the following current paths to the negative terminal of power supply 102: the second LED string is directly connected to pins 1 and 12 inside the terminal; the second LED string is connected to pin 2 inside the terminal via resistors R1 and R2; the second LED string is connected to pin 3 inside the terminal via resistors R3 and R4; the second LED string is connected to pin 5 inside the terminal via resistors R5 and R6. Therefore, by operating the switching module 110, the current path of each LED string in the first and second LED strings to the negative terminal of the power supply can be selectively switched. By appropriately selecting the resistance values ​​of resistors R1 to R12, multi-color temperature output of the dimmable lighting device can be achieved. Although as Figure 2 As shown, the switching module 110 is implemented using DIP terminals. However, it can be understood that, depending on actual needs, the switching module 110 can be other types of mechanical or electronic switching elements, and the mechanical switching elements can also include single-pole switches or multi-pole switches.

[0074] When the multi-color-temperature dimmable lighting device 10 undergoes dimming operation, especially during the adjustment from high brightness to low brightness (e.g., 10%), the dynamic resistance of the first and second LED strings increases as the current decreases. Therefore, the preset current ratio between the first and second LED strings changes undesirably, causing the color temperature of the multi-color-temperature dimmable lighting device 10 to become unstable during dimming operation. In this application, a color temperature stabilization module 108 is connected in series with the first and second LED strings. The color temperature stabilization module 108 compensates for the change in the current ratio between the LED strings caused by the dynamic resistance of the first and second LED strings, ensuring that the preset current ratio between the first and second LED strings remains unchanged, thereby maintaining the color temperature of the multi-color-temperature dimmable lighting device 10 stable during dimming operation.

[0075] Specifically, the color temperature stabilization module 108 can be implemented in roughly three ways: the color temperature stabilization module 108 includes a transistor unit, the color temperature stabilization module 108 includes a current mirror unit, and the color temperature stabilization module 108 includes a standard current source unit. The following will refer to... Figures 3 to 6 These three implementation methods will be described in detail.

[0076] like Figure 3 As shown, the multi-color temperature dimmable lighting device 20 according to the first embodiment of this application includes two LED strings. To distinguish them, in... Figure 3 The diagram shows a first LED string composed of C1, C2, C3, C4, C5, C6, C7, and C8, and a second LED string composed of W1, W2, W3, W4, W5, W6, W7, and W8. The first and second LED strings, connected in parallel, have different color temperatures. Each of the first and second LED strings is configured to be connected between the positive and negative terminals of the power supply 202. The multi-color-temperature dimmable lighting device 20 also includes a color-temperature stabilizing module connected in series with the first and second LED strings. Specifically, the color-temperature stabilizing module 108 consists of a common resistor 212, a first transistor 214, and a second transistor 216. Furthermore, the multi-color-temperature dimmable lighting device 20 may also include a rectified current circuit 204 and a constant current driver chip 206. The rectified circuit 204 can be configured to supply rectified DC current to the LED strings. Furthermore, the multi-color-temperature dimmable lighting device 20 may also include a switching module 210 connected to the first LED string and the second LED string. The switching module 210 selectively switches the current path of each LED string in the first and second LED strings to the negative terminal of the power supply 202. Figure 3 As shown, the switching module 210 uses DIP switches, which have five DIP travel distances: T1 indicates a short circuit between pins 1 and 4, and between pins 9 and 12; T2 indicates a short circuit between pins 2 and 4, and between pins 9 and 11; T3 indicates a short circuit between pins 3 and 4, and between pins 9 and 10; T4 indicates a short circuit between pins 5 and 4, and between pins 9 and 8; and T5 indicates a short circuit between pins 6 and 4, and between pins 9 and 7. Figure 3As shown, the first LED string can have the following current paths to the negative terminal of power supply 202: the first LED string is directly connected to pins 6 and 7 inside the terminal; the first LED string is connected to pin 8 inside the terminal via resistors R11 and R12; the first LED string is connected to pin 10 inside the terminal via resistors R9 and R10; the first LED string is connected to pin 11 inside the terminal via resistors R7 and R8. The second LED string can have the following current paths to the negative terminal of power supply 202: the second LED string is directly connected to pins 1 and 12 inside the terminal; the second LED string is connected to pin 2 inside the terminal via resistors R1 and R2; the second LED string is connected to pin 3 inside the terminal via resistors R3 and R4; the second LED string is connected to pin 5 inside the terminal via resistors R5 and R6. Therefore, by operating the switching module 210, the current path of each LED string in the first and second LED strings to the negative terminal of the power supply can be selectively switched. By appropriately selecting the resistance values ​​of resistors R1 to R12, multi-color temperature output of the dimmable lighting device can be achieved. Although as Figure 3 As shown, the switching module 210 is implemented using DIP terminals. However, it can be understood that, depending on actual needs, the switching module 210 can be other types of mechanical or electronic switching elements, and the mechanical switching elements can also include single-pole switches or multi-pole switches.

[0077] When the multi-color temperature dimmable lighting device 20 undergoes a dimming operation, especially during the process of adjusting from high brightness to low brightness (e.g., 10%), the dynamic resistance of the first LED string and the second LED string increases as the current decreases. Therefore, the preset current ratio between the first LED string and the second LED string will change undesirably, so that the color temperature of the multi-color temperature dimmable lighting device 20 cannot remain stable during the dimming operation. In the first embodiment of this application, the color temperature stabilization module consists of a common resistor 212, a first transistor 214, and a second transistor 216. The first terminal of the common resistor 212 is connected to the positive terminal of the power supply 202. The collector of the first transistor 214 is connected to C8 of the first LED string, and the emitter of the first transistor 214 is connected to multiple resistors or directly to the terminal of the switching module 210. The collector of the second transistor 216 is connected to W8 of the second LED string, and the emitter of the second transistor 216 is connected to multiple resistors or directly to the terminal of the switching module 210. The bases of both the first transistor 214 and the second transistor 216 are connected to a common connection point, and the second terminal of the common resistor 212 is also connected to this common connection point. The base-emitter voltage of the first transistor 214 is equal to the base-emitter voltage of the second transistor 216.

[0078] The following will refer to Figure 4 right Figure 3The color temperature stabilization module will be described in detail.

[0079] Figure 4 This is a schematic diagram of the color temperature stabilization module according to the first embodiment of this application, as shown below. Figure 4 The color temperature stabilization module shown can be combined with Figure 2 or Figure 3 This is used in the multi-color temperature dimmable lighting device shown. Figure 4 The diagram shows a first LED string consisting of D1, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, D12, and D13, and a second LED string consisting of D14, D15, D16, D17, D18, D19, D20, D21, D22, D23, D24, D25, and D26. The first and second LED strings, connected in parallel, have different color temperatures. Each LED string is configured to be connected between the positive and negative terminals of power supply 302. Figure 4 The color temperature stabilization module shown consists of a common resistor 304, a first transistor 306, and a second transistor 308. The first terminal of the common resistor 304 is connected to the positive terminal of the power supply 302. The collector of the first transistor 306 is connected to D13 of the first LED string, and the emitter of the first transistor 306 is connected to resistor 312. The collector of the second transistor 308 is connected to D26 of the second LED string, and the emitter of the second transistor 306 is connected to resistor 314. The bases of both the first transistor 306 and the second transistor 308 are connected to a common connection point 310. The second terminal of the common resistor is also connected to the common connection point 310. The base-emitter voltage of the first transistor 306 is equal to the base-emitter voltage of the second transistor 308.

[0080] To illustrate the function of the color temperature stabilization module, the current of power supply 302 was first set to 100mA. Then, the resistance ratio of resistors 312 and 314 was changed to test the current changes of the first and second LED strings, as shown in Table 2.

[0081] Table 2

[0082]

[0083] As shown in Table 2, the current ratio between the first LED string and the second LED string is approximately equal to the resistance ratio between resistor 312 and resistor 314.

[0084] Next, given the dimmable characteristics of the multi-color-temperature dimmable lighting device, and considering that the output current of the driver will change with the dimming operation, the current changes of the first LED string and the second LED string are shown in Table 3 when the resistance ratio of resistors 312 and 314 is fixed and the current of power supply 302 is changed:

[0085] Table 3

[0086]

[0087] As shown in Table 3, even when dimmed to 5%, the current ratio of the first LED string and the second LED string remains unchanged. Since the base-emitter voltage of the first transistor 306 is equal to the base-emitter voltage of the second transistor 308, the current ratio between the current flowing through the first LED string and the current flowing through the second LED string remains unchanged when the resistance ratio of the resistor 312 connected in series with the first LED string and the resistor 314 connected in series with the second LED string is fixed. Therefore, the color temperature of the multi-color-temperature dimmable lighting device does not change during dimming operation. Depending on the needs, the first transistor 306 and the second transistor 308 can be implemented using various transistors. Furthermore, when implementing the color temperature stabilization module using a chip, a MOSFET can be utilized. In the implementation using a MOSFET, the MOSFET, through current plus feedback, not only compensates for the influence of the resistance change of the LED string on the current ratio flowing through different LED strings, reducing the change in the current ratio of different LED strings during dimming to maintain the stability of the preset mixed color temperature, but also, MOSFETs have low conduction losses, high efficiency, and are easy to integrate at high density.

[0088] Figure 5 This is a schematic diagram of the color temperature stabilization module according to the second embodiment of this application, as shown below. Figure 5 The color temperature stabilization module shown can be combined with Figure 2 This is used in the multi-color temperature dimmable lighting device shown. Figure 5 The color temperature stabilization module shown consists of a ratio setting unit 402, a current mirror unit 406, and a reference current unit 404. Since the current mirror unit is typically implemented as an integrated circuit unit, therefore, as... Figure 5The color temperature stabilization module shown is described using a functional block diagram. The first input terminal of the current mirror unit 406 is connected to the ratio setting unit 402 to receive a first ratio setting command for the first LED string 408 and a second ratio setting command for the second LED string 410. The second input terminal of the current mirror unit 406 is connected to the reference current unit 404 to receive a reference current signal. The first output terminal of the current mirror unit 406 is connected to the first LED string 408, and the second output terminal is connected to the second LED string 410. The current mirror unit 406 outputs a first current determined based on the first ratio setting command and the reference current signal to the first LED string 408, and outputs a second current determined based on the second ratio setting command and the reference current signal to the second LED string 410. The color temperature stabilization module according to the second embodiment of this application uses a current mirror because a current mirror can accurately replicate or scale current, providing an output current that is highly matched to the reference current (input current), i.e., I... out =k×I ref Where k is a ratio coefficient. For example, the ratio setting unit 402 can set the first ratio setting command for the first LED string 408 to 1:10, and the ratio setting unit 402 can set the first ratio setting command for the second LED string 410 to 1:5. Therefore, the current ratio between the first LED string 408 and the second LED string 410 is fixed at 2:1. This current ratio will not change even during dimming because the reference current signal output by the reference current unit 404 will change dynamically with the dimming process. The current mirror unit 406 can output a current that is highly matched with the reference current to the first LED string 408 and the second LED string 410. That is, the current mirror unit 406 will output the first current determined based on the first ratio setting command and the dynamically changing reference current signal to the first LED string 408, and the current mirror unit 406 will output the second current determined based on the second ratio setting command and the dynamically changing reference current signal to the second LED string 410. Therefore, even during dimming, the current ratio between the first LED string 408 and the second LED string 410 is fixed to the original setting value.

[0089] Figure 6 This is a schematic diagram of a color temperature stabilization module according to a third embodiment of this application, as shown below. Figure 6 The color temperature stabilization module shown can be combined with Figure 2 This is used in the multi-color temperature dimmable lighting device shown. Since standard current sources are typically in the form of integrated circuit units, therefore, as... Figure 6 The color temperature stabilization module shown is described using a functional block diagram. For example... Figure 6The color temperature stabilization module shown consists of a first standard current source 508, a second standard current source 510, a ratio setting unit 504, a first reference current unit 502, and a second reference current unit 506. The first input terminal of the first standard current source 508 is connected to the ratio setting unit 504 to receive a first ratio setting command for the first LED string 512. The first input terminal of the second standard current source 510 is connected to the ratio setting unit 504 to receive a second ratio setting command for the second LED string 514. The second input terminal of the first standard current source 508 is connected to the first reference current unit 502 to receive a first reference current signal. The second input terminal of the second standard current source 510 is connected to the second reference current unit 506 to receive a second reference current signal. The output terminal of the first standard current source 508 is connected to the first LED string 512. The output terminal of the second standard current source 510 is connected to the second LED string 514. The first standard current source 508 outputs a first current determined based on the first ratio setting command and the first reference current signal to the first LED string 512. The second standard current source 510 outputs a second current determined based on the second ratio setting command and the second reference current signal to the second LED string 514. The color temperature stabilization module according to the third embodiment of this application adopts the form of a standard current source because a standard current source can accurately replicate or scale the current, providing an output current that is highly matched to the reference current (input current), i.e., I out =k×I ref Where k is a ratio coefficient. For example, the ratio setting unit 504 can set the first ratio setting command for the first LED string 512 to 1:10, and the ratio setting unit 504 can set the first ratio setting command for the second LED string 514 to 1:5. Therefore, the current ratio between the first LED string 512 and the second LED string 514 is fixed to 2:1. The current ratio remains unchanged even during dimming because the reference current signal output by the reference current unit 502 dynamically changes with the dimming process. The first standard current source 508 outputs a current highly matched to the reference current to the first LED string 512, and the second standard current source 510 outputs a current highly matched to the reference current to the second LED string 410. That is, the first standard current source 508 outputs a first current determined based on the first ratio setting command and the dynamically changing reference current signal to the first LED string 512, and the second standard current source 510 outputs a second current determined based on the second ratio setting command and the dynamically changing reference current signal to the second LED string 514. Therefore, even during dimming, the current ratio between the first LED string 512 and the second LED string 514 is fixed to the original setting value. Furthermore, although... Figure 6The ratio setting unit 504 is set to be shared by the first standard current source 508 and the second standard current source 510. However, according to actual needs, separate ratio setting units can be set for the first standard current source 508 and the second standard current source 510 respectively.

[0090] In this application embodiment, a dimmable lighting device for multiple color temperatures is provided to at least solve the technical problem in the prior art that the mixed color temperature of multiple color temperature lighting devices is difficult to maintain stable during the dimming process, resulting in a decrease in the lighting performance of the lighting device. This achieves the technical effect of keeping the mixed color temperature of the multiple color temperature lighting device stable during the dimming process, while maintaining the low cost of the lighting device.

[0091] In the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0092] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units or modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units, modules, or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling, direct coupling, or communication connection may be through some interfaces; the indirect coupling or communication connection of modules or units may be electrical or other forms.

[0093] The units or modules described as separate components may or may not be physically separate. The components shown as units or modules may or may not be physical units or modules; that is, they may be located in one place or distributed across multiple network units or modules. Some or all of the units or modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0094] Furthermore, the functional units or modules in the various embodiments of this application can be integrated into one processing unit or module, or each unit or module can exist physically separately, or two or more units or modules can be integrated into one unit or module. The integrated units or modules described above can be implemented in hardware or in the form of software functional units or modules.

[0095] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

Claims

1. A dimmable lighting device (10) with multiple color temperatures, characterized in that, include: A multi-channel LED string, comprising at least two LED strings connected in parallel to each other, wherein the LED strings have different color temperatures, and each LED string is configured to be connected between the positive and negative terminals or connected between the positive and negative terminals via one or more auxiliary elements; A color temperature stabilization module (108) is connected in series to at least two of the multiple LED strings. The color temperature stabilization module includes one of a transistor unit, a current mirror unit, and a standard current source unit. as well as A switching module (110) is connected to the multi-channel LED string, and the switching module selectively switches the current path of each LED string in the multi-channel LED string to the positive or negative terminal.

2. The dimmable lighting device with multiple color temperatures according to claim 1, characterized in that, In the case where the color temperature stabilization module includes the transistor unit and the multi-channel LED string consists of a first LED string having a first color temperature and a second LED string having a second color temperature different from the first color temperature, the color temperature stabilization module consists of a common resistor (304) and the transistor unit.

3. The dimmable lighting device with multiple color temperatures according to claim 2, characterized in that, The transistor unit includes a first transistor (306) and a second transistor (308). The first end of the common resistor is connected to the positive terminal. The first transistor is connected in series to the first LED string, and the second transistor is connected in series to the second LED string. The base of the first transistor and the base of the second transistor are both connected to the second end of the common resistor.

4. The dimmable lighting device with multiple color temperatures according to claim 3, characterized in that, The base-emitter voltage of the first transistor is equal to the base-emitter voltage of the second transistor.

5. The dimmable lighting device with multiple color temperatures according to claim 1, characterized in that, In the case where the color temperature stabilization module includes the current mirror unit and the multi-channel LED string consists of a first LED string with a first color temperature and a second LED string with a second color temperature different from the first color temperature, the color temperature stabilization module consists of a ratio setting unit, the current mirror unit (406), and a reference current unit.

6. The dimmable lighting device with multiple color temperatures according to claim 5, characterized in that, The first input terminal of the current mirror unit is connected to the ratio setting unit to receive a first ratio setting command for the first LED string and a second ratio setting command for the second LED string. The second input terminal of the current mirror unit is connected to the reference current unit to receive a reference current signal. The first output terminal of the current mirror unit is connected to the first LED string, and the second output terminal of the current mirror unit is connected to the second LED string. The current mirror unit outputs a first current determined based on the first ratio setting command and the reference current signal to the first LED string, and outputs a second current determined based on the second ratio setting command and the reference current signal to the second LED string.

7. The dimmable lighting device with multiple color temperatures according to claim 5 or 6, characterized in that, The reference current signal of the reference current unit changes dynamically during the dimming process of the dimmable lighting device.

8. The dimmable lighting device with multiple color temperatures according to claim 1, characterized in that, In the case where the color temperature stabilization module includes a standard current source unit and the multi-channel LED string consists of a first LED string with a first color temperature and a second LED string with a second color temperature different from the first color temperature, the color temperature stabilization module is composed of the standard current source unit, the ratio setting unit, the first reference current unit (502), and the second reference current unit (506).

9. The dimmable lighting device with multiple color temperatures according to claim 8, characterized in that, The standard current source unit includes a first standard current source (508) and a second standard current source (510). The first input terminal of the first standard current source is connected to the ratio setting unit to receive a first ratio setting command for the first LED string. The first input terminal of the second standard current source is connected to the ratio setting unit to receive a second ratio setting command for the second LED string. The second input terminal of the first standard current source is connected to the first reference current unit to receive a first reference current signal. The second input terminal of the second standard current source is connected to the second reference current unit to receive a second reference current signal. The output terminal of the first standard current source is connected to the first LED string. The output terminal of the second standard current source is connected to the second LED string. The first standard current source outputs a first current determined based on the first ratio setting command and the first reference current signal to the first LED string. The second standard current source outputs a second current determined based on the second ratio setting command and the second reference current signal to the second LED string.

10. The multi-color temperature dimmable lighting device according to claim 8 or 9, characterized in that, The reference current signal of each of the first reference current unit (502) and the second reference current unit (506) changes dynamically during the dimming process of the dimmable lighting device.

11. The dimmable lighting device with multiple color temperatures according to claim 1, characterized in that, The switching module selectively switches the current path of each LED string in the multi-channel LED string to the positive or negative terminal, including: the switching module directly connects at least one LED string in the multi-channel LED string between the positive and negative terminals according to the user's operation instructions, or connects at least one LED string in the multi-channel LED string between the positive and negative terminals via one of the auxiliary components.

12. The dimmable lighting device with multiple color temperatures according to claim 1, characterized in that, The switching module is a mechanical switching element or an electronic switching element, wherein the mechanical switching element includes a single-pole switch or a multi-pole switch.

13. The multi-color temperature dimmable lighting device according to claim 1, characterized in that, At least one of the current mirror unit and the standard current source unit is an integrated circuit unit.

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