Dimming system, dimming method and dimming lamp for driving light-emitting device based on double pulse width modulation signals

Abstract

The invention discloses a dimming system, a dimming method and a dimming lamp for driving a light-emitting device based on double pulse width modulation signals, and in the dimming system, a first driving circuit receives a first pulse width modulation signal and controls and outputs a first driving current to drive the light-emitting device according to the first pulse width modulation signal. The second driving circuit receives a second pulse width modulation signal and controls to output a second driving current, the second driving current value is smaller than the first driving current, and the duty ratio of the first pulse width modulation signal is reduced and the duty ratio of the second pulse width modulation signal is increased at least in a preset reduction stage of the expected brightness of the light emitting device. According to the dimming system and the dimming method, the dimming depth of the lamp under low brightness can be increased, and stroboflash is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of lamp dimming, and particularly to a dimming system, a dimming method, and a dimming lamp for driving a light-emitting device based on a dual pulse-width modulation signal. Background Art

[0002] In modern lighting systems, dimming technology plays a crucial role. Dimming can not only create a more comfortable light environment to meet the lighting needs in different scenarios but also significantly improve energy efficiency. Among various dimming technologies, pulse-width modulation (PWM) dimming has become the most widely used mainstream technology in the field of LED lighting due to its wide dimming range, high control precision, and ease of digital control. The basic principle of PWM dimming is to quickly switch the driving current of the LED and adjust the ratio of the current conduction time (Ton time) to the off time (Toff time) within a cycle, that is, the duty cycle. The higher the duty cycle, the longer the Ton time, the greater the average current of the LED, and the higher the brightness; conversely, the lower the duty cycle, the shorter the Ton time, and the lower the brightness. To avoid the human eye perceiving the light flicker, PWM dimming usually adopts a relatively high switching frequency, such as several hundred hertz or even higher.

[0003] However, the existing PWM dimming technology faces significant technical bottlenecks when achieving deep dimming, especially when pursuing extremely low brightness. To obtain lower brightness, the traditional approach is to significantly reduce the duty cycle of the PWM signal. However, when the duty cycle is extremely small, the Ton time will become very short, and the too short Ton time may exceed the minimum conduction time limit of some power chips, resulting in the chip being unable to work properly, the dimming control being ineffective or unstable, and even abnormal phenomena such as light flicker occurring. To avoid affecting the normal operation of the power chip, existing dimming lamps will reduce the dimming depth at low brightness or reduce the frequency of the PWM signal. Although reducing the PWM signal frequency can extend the Ton time, too low a PWM frequency will enable the human eye to perceive the periodic flicker of the light, that is, the stroboscopic phenomenon. Stroboscopy not only reduces the comfort of lighting but may even cause visual fatigue and health problems when exposed to a stroboscopic environment for a long time.

[0004] Therefore, the current PWM dimming technology has problems of insufficient dimming depth at low brightness and easy occurrence of stroboscopy. Summary of the Invention

[0005] The object of the present invention is to overcome the above-mentioned defects or problems existing in the background art, and provide a dimming system, a dimming method, and a dimming lamp for driving a light-emitting device based on a dual pulse-width modulation signal. The dimming system and the dimming method can increase the dimming depth of the lamp at low brightness, reduce stroboscopy, or provide a material basis for solving the above-mentioned defects or problems.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] Technical solution 1: A dimming system for driving a light-emitting device based on dual pulse-width modulation signals, which includes: a first driving circuit configured to receive a first pulse-width modulation signal and control a first driving current output to the light-emitting device according to the first pulse-width modulation signal; a second driving circuit configured to receive a second pulse-width modulation signal and control a second driving current output to the light-emitting device according to the second pulse-width modulation signal; the second driving current is less than the first driving current; and wherein, the first driving circuit and the second driving circuit are connected in parallel to the light-emitting device and respectively control current output in response to the first pulse-width modulation signal and the second pulse-width modulation signal to jointly determine the desired brightness of the light-emitting device; wherein, at least in a preset reduction stage of the desired brightness of the light-emitting device, the duty cycle of the first pulse-width modulation signal decreases and is accompanied by an increase in the duty cycle of the second pulse-width modulation signal.

[0008] Technical solution 2 based on Technical solution 1: In another preset reduction stage of the desired brightness of the light-emitting device, the duty cycle of the first pulse-width modulation signal decreases, and the duty cycle of the second pulse-width modulation signal remains at a preset first value; the first value is greater than or equal to 0 and less than or equal to 1.

[0009] Technical solution 3 based on Technical solution 1: When the desired brightness of the light-emitting device decreases to a preset first threshold, the duty cycle of the first pulse-width modulation signal is adjusted to a preset second value, and the duty cycle of the second pulse-width modulation signal increases to its maximum value; the second value is equal to 0 or close to 0.

[0010] Technical solution 4 based on Technical solution 3: After the desired brightness of the light-emitting device decreases to be lower than the first threshold, the desired brightness of the light-emitting device is further reduced by reducing the duty cycle of the second pulse-width modulation signal.

[0011] Technical solution 5 based on Technical solution 4: Both the first driving circuit and the second driving circuit are independent constant-current driving circuits controlled by a constant-current chip.

[0012] Technical solution 6 based on Technical solution 4: The first driving circuit adopts a buck-type constant-current driving circuit, and the second driving circuit adopts a linear constant-current driving circuit.

[0013] Technical solution 7 based on Technical solution 4: The first driving circuit adopts a constant-current driving circuit controlled by a constant-current chip; the second driving circuit is connected to the first driving circuit, and the second driving current is adjusted through a current-limiting module; the current-limiting module includes a current-limiting resistor and a current-limiting switch, and the current-limiting switch is configured to receive the second pulse-width modulation signal and be controlled to be turned off or on.

[0014] Technical solution eight based on technical solution one: It further includes a control module, which is used to output the first pulse width modulation signal and the second pulse width modulation signal to the first driving circuit and the second driving circuit respectively according to the expected brightness of the above-mentioned light-emitting device.

[0015] In addition, the present invention also provides technical solution nine: A dimming method for driving a light-emitting device based on dual pulse width modulation signals, which includes: obtaining the expected brightness of the light-emitting device; based on the expected brightness, adjusting the duty cycles of the first pulse width modulation signal and the second pulse width modulation signal; the adjustment method is: in the process of reducing the brightness of the light-emitting device, reducing the duty cycle of the first pulse width modulation signal and simultaneously increasing the duty cycle of the second pulse width modulation signal; and, when the expected brightness of the light-emitting device is reduced to a preset first threshold, reducing the duty cycle of the first pulse width modulation signal to 0 and increasing the duty cycle of the second pulse width modulation signal to its maximum value; and, after the expected brightness of the light-emitting device is reduced to below the first threshold, in the process of reducing the expected brightness of the light-emitting device, reducing the duty cycle of the second pulse width modulation signal; using the first pulse width modulation signal and the second pulse width modulation signal to control the output currents of the first driving circuit and the second driving circuit respectively to drive the light-emitting device; the first driving circuit and the second driving circuit are connected in parallel to the light-emitting device.

[0016] In addition, the present invention also provides technical solution ten: A dimming lamp, which includes a light-emitting device and a dimming module, and is characterized in that the dimming module adopts the dimming system for driving the light-emitting device based on dual pulse width modulation signals according to any one of technical solutions one to eight.

[0017] As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following beneficial effects:

[0018] Technical solution one provides a dimming system for driving a light-emitting device based on dual pulse width modulation signals. This dimming system uses dual pulse width modulation signals to drive the first driving circuit and the second driving circuit to output the first driving current and the second driving current to the light-emitting device respectively, where the first driving current is greater than the second driving current; at the same time, when the expected brightness of the light-emitting device decreases, gradually reducing the first driving current and gradually increasing the second driving current realizes deep dimming at low brightness and improves the problem of easy strobing during dimming at low brightness.

[0019] Among them, the key technical means of Technical Solution 1 lies in setting two drive circuits that can respectively receive different pulse-width modulation signals, and making the first drive current greater than the second drive current. Among them, at least in a preset expected brightness reduction stage, as the expected brightness of the light-emitting device decreases, the duty cycle of the second pulse-width modulation signal is gradually increased. This is actually equivalent to introducing a smaller current channel for auxiliary dimming on the basis of the original first drive current. And as the expected brightness of the light-emitting device gradually decreases, the duty cycle of the first pulse-width modulation signal gradually decreases, while the duty cycle of the second pulse-width modulation signal gradually increases, which is equivalent to the proportion of the second drive current in the total drive current of the light-emitting device gradually increasing. When the expected brightness of the light-emitting device is relatively low, the light-emitting device can still be dimmed by adjusting the duty cycle of the second pulse-width modulation signal. Since the second drive current is overall smaller than the first drive current, the maximum expected brightness of the light-emitting device driven by the second drive current is also significantly lower than the maximum expected brightness of the light-emitting device driven by the first drive current. Therefore, during the dimming process by the second drive current, the light-emitting device can perform deep dimming under low-brightness conditions, and at this time, the second pulse-width modulation signal can still maintain a relatively high frequency, thus improving the problem of stroboscopic that is likely to occur during dimming at low brightness.

[0020] Moreover, compared with the conventional pulse-width modulation dimming technology, in Technical Solution 1, two independent drive circuits are creatively adopted to drive the light-emitting device. Since these two independent drive circuits can simultaneously output two drive currents with different magnitudes to the light-emitting device to achieve the drive of the light-emitting device, under high-brightness conditions, the light-emitting device can be mainly driven by the first drive circuit with a larger current. Under low-brightness conditions, the light-emitting device can be mainly driven by the second drive circuit with a smaller current. And in the middle brightness section, the light-emitting device can be driven by the first start circuit and the second drive circuit simultaneously. And during the process of the expected brightness gradually decreasing, this technical solution adopts the strategy of gradually reducing the first start current and gradually increasing the second drive current, so that it can gradually transition to mainly dimming the light-emitting device through the second drive circuit during this process, making the brightness change of the light-emitting device smoother, with better linearity, and enabling continuous dimming within a wider range, avoiding the brightness jump of the light-emitting device, and effectively improving the user experience.

[0021] In the second technical solution, during the stage of decreasing the desired brightness of another preset light-emitting device, the duty cycle of the first pulse-width modulation signal is decreased to reduce the current output of the first driving circuit. At the same time, the duty cycle of the second pulse-width modulation signal is maintained at a preset first value, which is greater than or equal to 0 and less than or equal to 1. That is to say, the current of the second driving circuit is kept constant. At this time, the total current output is the sum of the current of the first driving circuit and the current of the second driving circuit. And since the current of the first driving circuit is much larger than that of the second driving circuit, as the current of the first driving circuit decreases, the desired brightness of the light-emitting device will also decrease significantly, achieving the purpose of reducing the brightness of the light-emitting device. Moreover, since only the duty cycle of the first pulse-width modulation signal needs to be adjusted at this time, the control complexity is greatly reduced.

[0022] In the third technical solution, a first threshold of the desired brightness is preset in advance. When the desired brightness of the light-emitting device gradually decreases to the first threshold, the duty cycle of the first pulse-width modulation signal is controlled to a set second value, which is equal to 0 or close to 0. That is, the first driving current output by the first driving circuit is controlled to be in a state of stopping output or only outputting a very small value. When the first driving circuit stops outputting the first driving current and at the same time the duty cycle of the second pulse-width modulation signal increases to the maximum, the second driving current output by the second driving circuit is the largest at this time. At this time, the desired brightness of the light-emitting device decreases to a low brightness. And under this low brightness condition, since the second driving current is at the maximum value, there is still enough margin to further adjust the desired brightness of the light-emitting device, thereby realizing deep dimming under low brightness. Generally speaking, the preset threshold is used as the trigger condition for switching the dimming strategy. By precisely controlling the change of the duty cycles of the first and second pulse-width modulation signals at the threshold, a smooth switching of the driving circuit is achieved, thus avoiding brightness jumps and laying a foundation for subsequent fine dimming at low brightness, and ultimately optimizing the user experience of smoothly transitioning from a higher brightness to a lower brightness.

[0023] In the fourth technical solution, after the desired brightness of the light-emitting device is lower than the first threshold, the system switches to dimming through the second driving circuit. Since the second driving current is itself smaller than the first driving current, decreasing the duty cycle of the second pulse-width modulation signal will further reduce the average current output to the light-emitting device, realizing refined control of the extremely low brightness region, expanding the dimming range, and improving the dimming quality and user experience in an extremely dark environment.

[0024] In Technical Solution Five, both the first driving circuit and the second driving circuit are independent constant-current driving circuits controlled by a constant-current chip. The constant-current chip can accurately control the output current and make it unaffected by factors such as input voltage fluctuations and changes in the characteristics of light-emitting devices, maintaining the constancy of the output current. The accurate constant-current control enables a more linear relationship between the current output and the duty cycle of the pulse-width modulation signal, thereby improving the dimming accuracy and allowing users to precisely control the brightness level by adjusting the pulse-width modulation signal. The independent constant-current control circuits avoid the mutual influence between the first driving circuit and the second driving circuit, enabling each driving circuit to work independently and stably, and improving the reliability of the entire dimming system.

[0025] In Technical Solution Six, the first driving circuit adopts a buck-type constant-current driving circuit, and the second driving circuit adopts a linear constant-current driving circuit. The first driving circuit is responsible for outputting a relatively large driving current and is the main current source at high brightness. Adopting a buck-type constant-current driving with higher efficiency can effectively reduce the energy loss during high-brightness operation, improve the overall system efficiency, and reduce heat generation. The second driving circuit is responsible for outputting a relatively small driving current and operates at low brightness. At this time, the current demand is small, and the efficiency loss of the linear constant-current driving is relatively insignificant. However, its advantages of simple structure and low cost are manifested, which can reduce the system cost and complexity while ensuring the low-brightness dimming function. By using an efficient buck-type driver on the high-current path and a low-cost linear driver on the low-current path, a balance between efficiency and cost is achieved, optimizing the overall system design.

[0026] In Technical Solution Seven, the second driving circuit uses a simple current-limiting resistor and a switch controlled by the second pulse-width modulation signal to form a current-limiting module, which realizes an economical, efficient, and simplified limitation and control of the second driving current, reduces the system complexity and cost, and at the same time meets the requirements of the dual pulse-width modulation dimming system for the second driving current.

[0027] In Technical Solution Eight, by adding a control module and taking the desired brightness as the input, the control module can automatically generate appropriate dual pulse-width modulation signals according to a preset dimming algorithm, thereby realizing an intelligent automatic dimming function, improving the usability and intelligence level of the system, and making it easier to integrate into various intelligent lighting application scenarios. The desired brightness signal can come from various sources such as user input, ambient light sensors, and smart home systems, enabling the system to support multiple intelligent control methods, such as manual dimming, automatic dimming, and scene linkage.

[0028] Technical solution nine provides a dimming method for driving a light-emitting device based on dual pulse-width modulation signals. The key technical means lies in coordinately adjusting the duty cycles of the first pulse-width modulation signal and the second pulse-width modulation signal, rather than individually adjusting one pulse-width modulation signal, thereby achieving deep dimming at low brightness, improving the problem of stroboscopic that is prone to occur during dimming at low brightness, and at the same time, the change in brightness is smooth and linear, avoiding brightness jumps.

[0029] Technical solution ten provides a dimming lamp, which adopts the above dimming system, can achieve deep dimming at low brightness, can improve the problem of stroboscopic that is prone to occur during dimming at low brightness, and at the same time, the change in brightness is smooth and linear. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for description in the embodiments. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0031] Figure 1 It is a schematic block diagram of a dimming system for driving a light-emitting device based on dual pulse-width modulation signals according to an embodiment of the present invention;

[0032] Figure 2 It is a schematic circuit diagram of the dimming system according to Embodiment 1 of the present invention;

[0033] Figure 3 It is a schematic circuit diagram of the dimming system according to Embodiment 2 of the present invention;

[0034] Figure 4 It is a schematic circuit diagram of the dimming system according to Embodiment 3 of the present invention.

[0035] MAIN REFERENCE NUMERAL DESCRIPTION:

[0036] Light-emitting device 10; First driving circuit 20; Second driving circuit 30; Control module 40. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are the preferred embodiments of the present invention and should not be regarded as excluding other embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0038] In the claims, the description and the above-mentioned drawings of the present invention, unless otherwise clearly defined, when terms such as "first", "second" or "third" are used, they are only used to distinguish different objects and not to describe a specific order.

[0039] In the claims, the description and the above-mentioned drawings of the present invention, unless otherwise clearly defined, for orientation terms, when terms such as "center", "horizontal", "vertical", "longitudinal", "level", "top", "bottom", "inner", "outer", "upper", "lower", "front", "rear", "left", "right", "clockwise", "counterclockwise" etc. are used to indicate the orientation or position relationship, it is based on the orientation and position relationship shown in the drawings, and it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, so it should not be construed as limiting the specific protection scope of the present invention.

[0040] In the claims, the description and the above-mentioned drawings of the present invention, unless otherwise clearly defined, when the terms "fixed connection" or "fixedly connected" are used, they should be understood in a broad sense, that is, any connection method without displacement relationship and relative rotation relationship between the two, that is, it includes non-detachable fixed connection, detachable fixed connection, being integrated as a whole, and being fixed connected through other devices or elements.

[0041] In the claims, the description and the above-mentioned drawings of the present invention, when terms such as "comprise", "have" and their variants are used, are intended to mean "including but not limited to".

[0042] Embodiment 1

[0043] Embodiment 1 relates to a dimming system for driving a light-emitting device 10 based on a dual pulse-width modulation signal. The dimming system is used to adjust the brightness of the light-emitting device 10, and the light-emitting device 10 is a plurality of series-connected LED chips.

[0044] Refer to Figure 1, the dimming system includes a control module 40, a first driving circuit 20, and a second driving circuit 30. The control module 40 is configured to output a first pulse width modulation signal and a second pulse width modulation signal to the first driving circuit 20 and the second driving circuit 30 respectively according to the desired brightness of the light emitting device 10. The first driving circuit 20 is configured to receive the first pulse width modulation signal and control the output of a first driving current to the light emitting device 10 according to the first pulse width modulation signal. The second driving circuit 30 is configured to receive the second pulse width modulation signal and control the output of a second driving current to the light emitting device 10 according to the second pulse width modulation signal. The second driving current is less than the first driving current. Wherein, the first driving circuit 20 and the second driving circuit 30 are connected in parallel to the light emitting device 10 and respectively control the current output in response to the first pulse width modulation signal and the second pulse width modulation signal to jointly determine the desired brightness of the light emitting device 10. Wherein, at least in a preset reduction stage of the desired brightness of the light emitting device 10, the duty cycle of the first pulse width modulation signal decreases and is accompanied by an increase in the duty cycle of the second pulse width modulation signal.

[0045] Further, in another preset reduction stage of the desired brightness of the light emitting device 10, the duty cycle of the first pulse width modulation signal decreases and the duty cycle of the second pulse width modulation signal remains at a preset first value. The first value is greater than or equal to 0 and less than or equal to 1. Keeping the current of the second driving circuit constant, the total current output at this time is the sum of the current of the first driving circuit and the current of the second driving circuit. And since the current of the first driving circuit is much larger than that of the second driving circuit, as the current of the first driving circuit decreases, the desired brightness of the light emitting device will also decrease significantly, achieving the purpose of reducing the brightness of the light emitting device. And, since only the duty cycle of the first pulse width modulation signal needs to be adjusted at this time, the control complexity is greatly reduced.

[0046] Further, when the desired brightness of the light emitting device 10 decreases to a preset first threshold, the duty cycle of the first pulse width modulation signal is adjusted to a preset second value, and the duty cycle of the second pulse width modulation signal increases to its maximum value. The second value is equal to 0 or close to 0. And, after the desired brightness of the light emitting device 10 decreases to be lower than the first threshold, the desired brightness of the light emitting device 10 is further reduced by reducing the duty cycle of the second pulse width modulation signal.

[0047] Among them, the control module 40 is responsible for receiving the externally input desired brightness signal and generating two independent pulse width modulation signals based on this signal: the first pulse width modulation signal is output to the first driving circuit 20 to control the magnitude of the first driving current; the second pulse width modulation signal is output to the second driving circuit 30 to control the magnitude of the second driving current. The input of the control module 40 is the "desired brightness signal", which refers to the brightness level that the user hopes the lamp to reach or the brightness level that the control system attempts to make the lamp reach. The desired brightness signal can have multiple sources. For example: User manual adjustment: directly set the brightness through methods such as a knob, slider, touch screen, etc.; Ambient light sensor: automatically adjust the lamp brightness according to the ambient light intensity; Smart home system: receive instructions from the central control system to achieve scene linkage or timed switching of the lamp. The output of the control module 40 is two independent pulse width modulation signals. The duty cycles of these two signals are adjustable. By adjusting the duty cycle, the magnitude of the output current of the corresponding driving circuit is controlled, thereby changing the brightness of the light emitting device 10. The control module 40 internally contains a preset dimming algorithm or curve, and this algorithm determines the specific relationship between the desired brightness and the duty cycles of the two pulse width modulation signals. The control module 40 can be implemented in various ways, such as an application specific integrated circuit (ASIC), a microcontroller (MCU), or a digital signal processor (DSP). Those skilled in the art can implement the above-mentioned control module 40 based on the content disclosed in this specification and in combination with the common general knowledge in the art.

[0048] The first driving circuit 20 and the second driving circuit 30 respectively receive the first pulse width modulation signal and the second pulse width modulation signal output by the control module 40, and can control the first driving current and the second driving current according to the received pulse width modulation signals. Here, controlling the first driving current and the second driving current means controlling the average current output by the driving circuit to the light emitting device 10 by changing the duty cycle of the pulse width modulation signal. The higher the duty cycle, the greater the average current, and the higher the brightness of the light emitting device 10; the lower the duty cycle, the smaller the average current, and the lower the brightness of the light emitting device 10.

[0049] The first driving circuit 20 and the second driving circuit 30 are usually constant current driving circuits that can provide a constant current, and generally include a switching element, an energy storage element, a feedback circuit, and a control chip. Among them, the switching element is usually a metal oxide semiconductor field effect transistor or a bipolar transistor, which acts as an electronic switch and conducts or turns off according to the control of the pulse width modulation signal. The energy storage element is usually an inductor suitable for a buck or boost driving circuit or a capacitor suitable for a linear driving circuit, which is used to smooth the current fluctuation and provide a relatively stable output current. The feedback circuit is an optional part, which is used to monitor the output current or voltage, and compare the feedback signal with a reference value to achieve more accurate current control. The feedback circuit can automatically adjust the duty cycle of the pulse width modulation signal to compensate for the influence of input voltage, load change or other factors. The control chip refers to a dedicated constant current control chip, which is used to process the pulse width modulation signal and control the conduction and turn-off of the switching element.

[0050] In the dimming system involved in the present invention, the key lies in the control of the first pulse width modulation signal and the second pulse width modulation signal. Specifically, in the high brightness region, which is set as the region where the desired brightness is higher than the second threshold, in this region, the light emitting device 10 is supplied with current through the first driving circuit 20, and the duty cycle of the second pulse width modulation signal received by the second driving circuit 30 is 0. Then, when the desired brightness of the light emitting device 10 decreases to be lower than the second threshold and higher than the first threshold, that is, in the medium brightness region, in this region, the light emitting device 10 is supplied with current through the first driving circuit 20 and the second driving circuit 30 at the same time, and both the first pulse width modulation signal and the second pulse width modulation signal are not 0. And, in the medium brightness region, as the desired brightness decreases, the duty cycle of the first pulse width modulation signal gradually decreases, and the duty cycle of the second pulse width modulation signal gradually increases. Then, when the desired brightness of the light emitting device 10 decreases to the first threshold, at this time, the duty cycle of the first pulse width modulation signal decreases to 0, the first driving circuit 20 does not supply current to the light emitting device 10, and at the same time, the duty cycle of the second pulse width modulation signal increases to the maximum value, and the second driving circuit 30 outputs its maximum current to the light emitting device 10. Then, when the desired brightness of the light emitting device 10 decreases to be lower than the first threshold, at this time, the duty cycle of the second pulse width modulation signal gradually decreases until the desired brightness reaches the lowest threshold.

[0051] Among them, a first threshold of an expected brightness is preset in advance. When the expected brightness of the light-emitting device 10 gradually decreases to the first threshold, the first pulse-width modulation signal is controlled to a set second value, and the second value is equal to 0 or close to 0, that is, the first driving current output by the first driving circuit is controlled to be in a state of stopping output or only outputting a minimum value. When the first driving circuit 20 stops outputting the first driving current and the duty cycle of the second pulse-width modulation signal increases to the maximum, at this time, the second driving current output by the second driving circuit 30 is the largest, and the expected brightness of the light-emitting device 10 decreases to a low brightness. And under this low brightness condition, since the second driving current is at the maximum value, there is still enough margin to further adjust the expected brightness of the light-emitting device 10, so as to achieve deep dimming at low brightness. Overall, the preset threshold is used as a trigger condition for the switching of the dimming strategy. By precisely controlling the change of the duty cycles of the first and second pulse-width modulation signals at the threshold, a smooth switching of the driving circuit is achieved, thereby avoiding brightness jumps and laying a foundation for subsequent fine dimming at low brightness, and finally optimizing the user experience of smoothly transitioning from a higher brightness to a lower brightness. In addition, after the expected brightness of the light-emitting device 10 is lower than the first threshold, the system switches to dimming through the second driving circuit 30. Since the second driving current is itself smaller than the first driving current, reducing the duty cycle of the second pulse-width modulation signal will further reduce the average current output to the light-emitting device 10, realizing fine control of the extremely low brightness area, expanding the dimming range, and improving the dimming quality and user experience in an extremely dark environment.

[0052] The above dimming system uses dual pulse width modulation signals to drive the first driving circuit 20 and the second driving circuit 30 respectively to output a first driving current and a second driving current to the light emitting device 10, where the first driving current is greater than the second driving current; at the same time, when the desired brightness of the light emitting device 10 decreases, the first driving current is gradually decreased and the second driving current is gradually increased, realizing deep dimming at low brightness and improving the problem of stroboscopic that is prone to occur during dimming at low brightness. Among them, two driving circuits that can receive different pulse width modulation signals respectively are set, and the first driving current is made greater than the second driving current. Among them, at least in a preset desired brightness decreasing stage, as the desired brightness of the light emitting device 10 decreases, the duty cycle of the second pulse width modulation signal is gradually increased. This is actually equivalent to introducing a smaller current channel for auxiliary dimming on the basis of the original first driving current. And as the desired brightness of the light emitting device 10 gradually decreases, the duty cycle of the first pulse width modulation signal gradually decreases, while the duty cycle of the second pulse width modulation signal gradually increases, which is equivalent to the proportion of the second driving current in the total driving current of the light emitting device 10 gradually increasing. When the desired brightness of the light emitting device 10 is relatively low, the light emitting device 10 can still be dimmed by adjusting the duty cycle of the second pulse width modulation signal. Since the second driving current is overall smaller than the first driving current, the maximum desired brightness of the light emitting device 10 driven by the second driving current is also significantly lower than the maximum desired brightness of the light emitting device 10 driven by the first driving current. Therefore, during the dimming process by the second driving current, the light emitting device 10 can perform deep dimming under low brightness conditions, and at this time, the second pulse width modulation signal can still be maintained at a relatively high frequency, thus improving the problem of stroboscopic that is prone to occur during dimming at low brightness. And, compared with the conventional pulse width modulation dimming technology, in Technical Solution 1, two independent driving circuits are creatively used to drive the light emitting device 10. Since these two independent driving circuits can simultaneously output two driving currents with different magnitudes to the light emitting device 10 to realize the driving of the light emitting device 10, under high brightness conditions, the light emitting device 10 can be mainly driven by the first driving circuit 20 with a larger current. Under low brightness conditions, the light emitting device 10 can be mainly driven by the second driving circuit 30 with a smaller current. And when in the middle brightness section, the light emitting device 10 can be driven by the first starting circuit and the second driving circuit 30 simultaneously. And during the process of gradually decreasing the desired brightness, this technical solution adopts the strategy of gradually decreasing the first starting current and gradually increasing the second driving current, so that it can gradually transition to mainly dimming the light emitting device 10 through the second driving circuit 30 during this process, making the brightness change of the light emitting device 10 smoother, with better linearity, and realizing continuous dimming within a wider range, avoiding the brightness jump of the light emitting device 10 and effectively improving the user experience.

[0053] In this embodiment, the first driving circuit 20 and the second driving circuit 30 are both set as independent constant-current driving circuits controlled by a constant-current chip. The constant-current chip can accurately control the output current and make it unaffected by factors such as input voltage fluctuations and changes in the characteristics of the light-emitting device 10, maintaining the constancy of the output current. The precise constant-current control enables a more linear relationship between the current output and the duty cycle of the pulse-width modulation signal, thereby improving the dimming accuracy and allowing the user to accurately control the brightness level by adjusting the pulse-width modulation signal. The independent constant-current control circuits avoid the mutual influence between the first driving circuit 20 and the second driving circuit 30, enabling each driving circuit to work independently and stably, and improving the reliability of the entire dimming system.

[0054] In addition, the maximum value of the second driving current is set to 1% to 10% of the maximum value of the first driving current. By reasonably defining the ratio range of the second driving current relative to the first driving current, the current magnitude grading of the two driving circuits is clarified, and the current distribution in the high and low brightness regions is optimized, ensuring both the fineness of low-brightness dimming and taking into account high-brightness efficiency and system safety, and enhancing the performance balance of the overall dimming system.

[0055] Specifically, referring to Figure 2 , which shows the circuit structure of the dimming system adopted in this embodiment, mainly including a first driving circuit 20, a second driving circuit 30, and a light-emitting device 10. The first driving circuit 20 receives a first pulse-width modulation signal, and the second driving circuit 30 receives a second pulse-width modulation signal. Among them, the circuit structures of the first driving circuit 20 are the same, and the difference between them lies in the magnitude of the output current. Hereinafter, the driving circuit adopted in this embodiment will be described by taking the first driving circuit 20 as an example.

[0056] The first driving circuit 20 of this embodiment includes an inductor L1, a diode D11, an integrated circuit U1, resistors R11, R12, R13, R14, R15, R17, capacitors C11, C12, C14, C15, and a diode D12. The integrated circuit U1 herein is a general-purpose constant-current control chip in the art, and TPS61165, TPS92510, etc. can be selected according to actual situations.

[0057] Among them, the input power supply: V24+ is connected to one end of the inductor L1 and the cathode of the diode D11. V24+ is the DC input voltage of the circuit. Inductor L1: One end is connected to V24+, and the other end is connected to the SW (Switching) pin of the integrated circuit U1. Diode D11: The cathode is connected to V24+, and the anode is connected to the node of L1 and the SW pin of U1. D11 serves as a freewheeling diode in the buck converter to provide a path for the inductor current. Integrated circuit U1: This is a constant current control chip, and its pin functions are as follows: OGND (Output Ground): Output ground, connected to the circuit ground GND; Ires (Current setting resistor): Current setting resistor pin, connected to the resistor R12; the resistance value of R12 determines the magnitude of the drive current; DIM (Dimming): Dimming input pin, connected to the external PWM signal PWM1 through the resistor R17 and the capacitor C15; the PWM1 signal is used to control the brightness of the LED; VDD: Power supply voltage input pin of the IC, used to supply power for the IC itself to work; COMP (Compensation): Compensation pin, connected to the compensation network composed of the resistors R15 and the capacitors C12, C14; Vout (Voltage Output feedback): Output voltage feedback pin, connected to the output terminal through the resistors R13 and R14; OVP (Over Voltage Protection): Overvoltage protection pin, also sets the overvoltage protection threshold through the resistors R13 and R14; CS (Current Sense): Current detection pin, connected to the output terminal through the resistors R11 and R12, used to detect the output current; SW (Switching): Switching pin, connected to the anode of the inductor L1 and the diode D11. Resistors R11 and R12: Current detection resistors, R12 is the Ires resistor, and they are jointly used to set and detect the current flowing through the LED. Resistors R13 and R14: Form a voltage dividing resistor network for output voltage feedback and overvoltage protection. Resistors R15, capacitor C12 and C14: Form the compensation network of the DC-DC converter, used to stabilize the feedback loop and prevent oscillation. Resistors R17 and capacitor C15: Form the input filter circuit of the PWM dimming signal PWM1, filter out high-frequency interference, and make the dimming signal more stable. Diode D12: Output rectifier diode, connected between the output terminal of U1 and the LED string, and the LED string is the above-mentioned light-emitting device 10.

[0058] The structure of the second driving circuit 30 is the same as that of the first driving circuit 20. By setting different Ires resistors (R12 and R22), the first driving circuit 20 and the second driving circuit 30 can output different maximum currents. The diodes D12 and D22 play an isolation role to prevent mutual influence between the two driving circuits.

[0059] Example 2

[0060] The difference between Example 2 and Example 1 is that the first driving circuit 20 adopts a buck-type constant-current driving circuit, and the second driving circuit 30 adopts a linear constant-current driving circuit. The first driving circuit 20 is responsible for outputting a relatively large driving current and is the main current source at high brightness. By adopting a buck-type constant-current driving with higher efficiency, it can effectively reduce the energy loss during high-brightness operation, improve the overall efficiency of the system, and reduce heat generation. The second driving circuit 30 is responsible for outputting a relatively small driving current and operates at low brightness. At this time, the current demand is small, and the efficiency loss of linear constant-current driving is relatively insignificant. However, its advantages of simple structure and low cost are reflected, and it can reduce the system cost and complexity while ensuring the low-brightness dimming function. By using an efficient buck-type drive on the high-current path and a low-cost linear drive on the low-current path, a balance between efficiency and cost is achieved, and the overall system design is optimized.

[0061] Specifically, referring to Figure 3 , it shows the circuit structure of the dimming system adopted in this embodiment. Among them, the first driving circuit 20 includes an integrated circuit U1, a triode Q1, an inductor L1, a diode D31, resistors R1, R2, R3, R4, R5, capacitors C1, C2, C3, and a diode E1. The integrated circuit U1 among them is a general-purpose constant-current control chip in the art.

[0062] Among them, the input power supply: DC40V+ is connected to one end of the inductor L1 and the cathode of the diode D31. DC40V+ is the DC input voltage of the circuit. Integrated circuit U1: This is a constant current control chip, and its pin functions are as follows: VDD: the power supply voltage input pin of the IC; NC: unconnected pin; GND: circuit ground; PWM: the pulse width modulation input pin, connected to the external PWM signal PWM1 through the resistor R5 and the capacitor C3; Gate: the gate drive output pin, connected to the base of the triode Q1; S: the current detection input pin, connected to one end of the current detection resistor R1. Triode Q1: NPN type triode, used as a switching device. The collector of this triode is connected to the node of the inductor L1 and the anode of the diode D31; the base is connected to the Gate pin of the IC U3, and the switching state is controlled by the output signal of U3; the emitter is connected to the other end of the current detection resistor R1 and finally connected to the circuit ground GND. Inductor L1: One end is connected to DC40V+, and the other end is connected to the node of the collector of the triode Q1 and the anode of the diode D31. Diode D31: The cathode is connected to DC40V+, and the anode is connected to the node of L1 and the Q1 collector. Resistor R1: Current detection resistor, connected between the emitter of the triode Q1 and the circuit ground GND. U1 detects the voltage on R1 through the S pin to achieve constant current control. Resistors R2 and capacitor C1: form a feedback network. Resistor R3: serves as a pull-up resistor. Resistors R4 and capacitor C2: constitute a power supply filter circuit to filter out power supply noise and improve system stability. Resistors R5 and capacitor C3: form an input filter circuit for the PWM dimming signal PWM1. Diode E1: connected in series at the output end as an output rectifier diode.

[0063] The second drive circuit 30 includes an integrated circuit U2, resistors R6, R7, R8, R9, R10, and R11. The integrated circuit U1 therein is a general linear constant current control chip in the art.

[0064] Among them, the input power supply: DC40V+ also serves as the input power supply of the second driving circuit 30 and is shared with the first driving circuit 20. Integrated circuit U2: This is a linear constant current control chip, and its pin functions are as follows: Drain: Drain pin, connected to resistor R11; Vin: Input voltage pin, also connected to the input power supply DC40V+; NC: Unconnected pin; GND: Circuit ground; DIM: Dimming input pin, connected to the external PWM signal PWM2 through resistor R8; CS: Current setting / current detection pin, connected to the output terminal and GND through resistors R7, R9, and R10; VD: Voltage Drive pin. Resistor R6: Connected in series at the input end as an input protection resistor. Resistors R7, R9, and R10: Form a current setting resistor network for setting the output current of the linear constant current driver U2. R7 and R9 are used as voltage dividing resistors, and R10 is used as a trimming resistor. Resistor R8: Connected to the PWM2 signal for controlling the dimming input of the linear constant current driver. R11 is connected to the light-emitting device 10.

[0065] Embodiment 3

[0066] The difference between Embodiment 3 and Embodiment 1 is that the first driving circuit 20 adopts a constant current driving circuit controlled by a constant current chip; the second driving circuit 30 is connected to the first driving circuit 20, and the second driving current is adjusted through a current limiting module; the current limiting module includes a current limiting resistor and a current limiting switch, and the current limiting switch is configured to receive the second pulse width modulation signal and. In this embodiment, the second driving circuit 30 uses a simple current limiting resistor and a switch controlled by the second pulse width modulation signal to form a current limiting module, realizing an economical, efficient, and simplified limitation and control of the second driving current, reducing the system complexity and cost, and simultaneously meeting the requirements of the dual pulse width modulation dimming system for the second driving current.

[0067] Specifically, referring to Figure 4 , which shows the circuit structure of the dimming system adopted in this embodiment. Among them, the structure of the first driving circuit 20 in this embodiment is the same as that of the first driving circuit 20 in Embodiment 2 and will not be elaborated here. The second driving circuit 30 includes a triode Q2 and a resistor R21, where the triode Q2 is the above-mentioned current limiting switch and the resistor R21 is the above-mentioned current limiting resistor. The collector of the triode Q2 is connected to the resistor R21, the base is connected to the external PWM signal PWM2, and the emitter is connected to the circuit ground. The resistor R21 is connected as a current limiting resistor between the collector of the triode Q2 and the anode of the LED string.

[0068] Embodiment 4

[0069] Embodiment 4 of the present invention relates to a dimming method for driving a light-emitting device 10 based on dual pulse width modulation signals, which includes the following steps:

[0070] Step 1: Obtain the desired brightness of the light-emitting device 10;

[0071] Step 2: Based on the desired brightness, adjust the duty cycles of the first pulse-width modulation signal and the second pulse-width modulation signal; the adjustment method is: in the process of reducing the brightness of the light-emitting device 10, reduce the duty cycle of the first pulse-width modulation signal, and at the same time increase the duty cycle of the second pulse-width modulation signal; and, when the desired brightness of the light-emitting device 10 is reduced to a preset first threshold, reduce the duty cycle of the first pulse-width modulation signal to 0, and increase the duty cycle of the second pulse-width modulation signal to its maximum value; and, after the desired brightness of the light-emitting device 10 is reduced to below the first threshold, in the process of reducing the desired brightness of the light-emitting device 10, reduce the duty cycle of the second pulse-width modulation signal;

[0072] Step 3: Use the first pulse-width modulation signal and the second pulse-width modulation signal to control the output currents of the first driving circuit 20 and the second driving circuit 30 respectively to drive the light-emitting device 10; the first driving circuit 20 and the second driving circuit 30 are connected in parallel to the light-emitting device 10.

[0073] For the specific content and implementation manner of the above steps, reference can be made to the descriptions of Embodiments 1 to 3 of this specification, and details are not elaborated here. By adopting this dimming method, deep dimming at low brightness is achieved, and the problem of easy occurrence of stroboscopic during dimming at low brightness is improved. At the same time, the change of brightness is smooth and linear, and brightness jump can be avoided.

[0074] Embodiment 5

[0075] Embodiment 5 of the present invention relates to a dimming lamp, which includes a light-emitting device 10 and a dimming module. The dimming module adopts the dimming system for driving the light-emitting device 10 based on a dual pulse-width modulation signal as described in any one of Embodiments 1 to 3. By adopting the above dimming system, this dimming lamp can achieve deep dimming at low brightness, improve the problem of easy occurrence of stroboscopic during dimming at low brightness, and at the same time the brightness change is smooth and linear.

[0076] The descriptions of the above specification and embodiments are used to explain the protection scope of the present invention, but do not constitute a limitation on the protection scope of the present invention. Through the inspiration of the present invention or the above embodiments, those of ordinary skill in the art, combined with common general knowledge, ordinary technical knowledge in this field, and / or existing technologies, through logical analysis, reasoning, or limited experiments, modifications, equivalent replacements, or other improvements to the embodiments of the present invention or some of its technical features can be obtained, and all should be included within the protection scope of the present invention.

Claims

1. A dimming system for driving a light emitting device based on a dual pulse width modulation signal, characterized in that: include: A first drive circuit (20) configured to receive a first pulse width modulation signal and control a first drive current output to the light emitting device (10) according to the first pulse width modulation signal; a second drive circuit (30) configured to receive a second pulse width modulation signal and control a second drive current output to the light emitting device (10) according to the second pulse width modulation signal; the second drive current being smaller than the first drive current; and The first drive circuit (20) and the second drive circuit (30) are connected in parallel to the light-emitting device (10), and respectively control the current output in response to the first pulse width modulation signal and the second pulse width modulation signal, so as to jointly determine the desired brightness of the light-emitting device (10); Wherein, at least in a preset phase of decreasing the expected brightness of the light emitting device (10), the duty cycle of the first pulse width modulation signal decreases, and the duty cycle of the second pulse width modulation signal increases.

2. A dimming system for driving a light emitting device based on a dual pulse width modulation signal as claimed in claim 1, characterized in that: In another preset phase of decreasing the expected brightness of the light emitting device (10), the duty cycle of the first pulse width modulation signal decreases, and the duty cycle of the second pulse width modulation signal is maintained at a preset first value; the first value is greater than or equal to 0 and less than or equal to 1.

3. A dimming system for driving a light emitting device based on a dual pulse width modulation signal as claimed in claim 1, characterized in that: When the desired brightness of the light emitting device (10) decreases to a preset first threshold value, the duty cycle of the first pulse width modulation signal is adjusted to a preset second value, and the duty cycle of the second pulse width modulation signal is increased to its maximum value; The second value is equal to 0 or close to 0.

4. A dimming system for driving a light emitting device based on a dual pulse width modulation signal as claimed in claim 3, characterized in that: After the expected brightness of the light emitting device (10) decreases to below the first threshold, the expected brightness of the light emitting device (10) is further reduced by reducing the duty cycle of the second pulse width modulation signal.

5. A dimming system for driving a light emitting device based on a dual pulse width modulation signal as claimed in claim 4, characterized in that: The first drive circuit (20) and the second drive circuit (30) are both independent constant current drive circuits controlled by a constant current chip.

6. A dimming system for driving a light emitting device based on a dual pulse width modulation signal as claimed in claim 4, characterized in that: The first drive circuit (20) adopts a step-down constant current drive circuit, and the second drive circuit (30) adopts a linear constant current drive circuit.

7. A dimming system for driving a light emitting device based on a dual pulse width modulation signal as claimed in claim 4, characterized in that: The first drive circuit (20) adopts a constant current drive circuit controlled by a constant current chip; the second drive circuit (30) is connected to the first drive circuit (20) and adjusts the second drive current through a current limiting module; the current limiting module comprises a current limiting resistor and a current limiting switch, and the current limiting switch is configured to receive the second pulse width modulation signal and be controlled to open or close.

8. A dimming system for driving a light emitting device based on a dual pulse width modulation signal as claimed in claim 1, characterized in that: It also includes a control module (40) for outputting the first pulse width modulation signal and the second pulse width modulation signal to the first drive circuit (20) and the second drive circuit (30) respectively according to the desired brightness of the light-emitting device (10).

9. A dimming method for driving a light emitting device based on a dual pulse width modulation signal, characterized in that: include: Obtaining a desired brightness of the light emitting device (10); Based on the expected brightness, the duty cycle of the first pulse width modulation signal and the second pulse width modulation signal are adjusted, the adjustment method comprising: at least in a preset stage of reducing the expected brightness of the light emitting device (10), the duty cycle of the first pulse width modulation signal is reduced, and the duty cycle of the second pulse width modulation signal is increased; The first pulse width modulation signal and the second pulse width modulation signal are used to control the output current of the first drive circuit (20) and the second drive circuit (30) respectively, so as to drive the light emitting device (10); the first drive circuit (20) and the second drive circuit (30) are connected in parallel to the light emitting device (10).

10. A dimming lamp, comprising a light emitting device (10) and a dimming module, characterized in that: The dimming module adopts the dimming system based on dual pulse width modulation signal driving the light emitting device as described in any one of claims 1 to 8.

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