A multi-channel synchronous dimming circuit

Abstract

The present invention relates to the field of load driving technology, and discloses a multi-channel synchronous dimming circuit, comprising a voltage control module, a plurality of load branches, a current regulating module, a dimming signal output module and a dimming signal coupling module, wherein the load branch comprises a load and a switch tube electrically connected in series, the dimming signal output module is used to input a PWM signal for independently dimming the corresponding load to each load branch, and the dimming signal coupling module is used to couple the plurality of PWM signals into a control signal for performing total dimming and output it, so that not only can the purpose of single-channel and arbitrary multi-channel dimming without mutual influence be achieved under the condition of unchanged output power, but also the cost of adding an additional channel can be limited to adding a switch tube, and in the subsequent circuit, it is an inductor-free application and will not cause strong EMC problems, so that in practical applications, the volume and cost control of the driving power supply can have significant advantages.

Description

Technical Field

[0001] The present invention belongs to the technical field of load driving, and in particular, relates to a multi-channel synchronous dimming circuit. Background Art

[0002] As the LED (Light-Emitting Diode) dimming power supply market has put forward higher standards for dimming depth, multi-channel, output flicker-free and product cost, the existing technologies / solutions are increasingly difficult to meet these requirements, especially for solutions with high requirements for multiple indicators. It is more difficult to achieve a suitable balance. Either the cost is too high or the performance does not meet the requirements. For example, the application of multi-channel dimming and color adjustment / RGB dimming can highlight this contradiction. In detail, the market's requirements trend is not only to require no flicker, lower THD (Total Harmonic Distortion), higher light efficiency and lower dimming brightness, but also to be more sensitive to cost, safety certification, stability, dimming mode, multi-channel and application scenarios. Simply put, all these requirements and indicators need to be met. To meet such a comprehensive requirement, it is not simply to take one or several solutions and splice and / or expand them at will. This is a pain point that has always existed in the industry. To solve it, it is necessary to start from the architecture and underlying principles.

[0003] From another perspective, from the perspective of specific isolated drive applications, most of the current topologies used for single-channel dimming or multi-channel dimming are AC to DC (i.e., used to achieve constant voltage), and then DC to DC (i.e., used to achieve constant current); each output channel requires an independent DC to DC converter, which results in multi-channel applications. The power supply design, volume, cost, processing, reliability, EMC (Electromagnetic Compatibility, electromagnetic compatibility, refers to the ability of a device or system to operate in accordance with requirements in its electromagnetic environment and not cause unbearable electromagnetic interference to any device in its environment) and certification are all subject to great restrictions, especially in high-power applications, there are even few options. Summary of the invention

[0004] In order to solve the multiple constraints faced by existing driving circuits in multi-channel applications, the purpose of the present invention is to provide a multi-channel synchronous dimming circuit, which can not only achieve single-channel and arbitrary multi-channel dimming without mutual influence under the condition of unchanged output power, but also make the cost of adding an additional channel limited to adding a switch tube instead of a whole circuit device, and in the subsequent circuit, it is an inductor-free application, and will not cause strong EMC problems like the inductor in DC-to-DC applications. Therefore, in practical applications, the volume and cost control of the driving power supply can be significantly advantageous, which is convenient for practical application and promotion.

[0005] The technical solution adopted by the present invention is: a multi-channel synchronous dimming circuit, including a voltage control module, N load branches, a current regulation module, a dimming signal output module and a dimming signal coupling module, wherein the load branch includes a load and a switch tube electrically connected in series, N represents a positive integer not less than 2, and the load is a light-emitting lamp;

[0006] The voltage control module is used to convert the input voltage into a DC voltage and output it;

[0007] The positive terminals of the N load branches are respectively connected to the voltage output terminal of the voltage control module, the negative terminals of the N load branches are respectively connected to one end of the current regulating module, and the other end of the current regulating module is grounded;

[0008] The N PWM signal output ends of the dimming signal output module are connected to the controlled ends of the switch tubes in the N load branches one by one, and the N PWM signal output ends are also connected to the N signal input ends of the dimming signal coupling module one by one, and the signal output end of the dimming signal coupling module is connected to the dimming signal input end of the current regulation module;

[0009] The dimming signal output module is used to input a PWM signal for independently dimming the corresponding load to each of the N load branches;

[0010] The dimming signal coupling module is used to couple the PWM signals from the N PWM signal output terminals into a control signal for overall dimming of the N load branches and output the control signal, wherein the overall dimming coefficient K of the control signal satisfies:

[0011] K=(K1*I1+K2*I2+…+K n *I n +…+K N *I N ) / I

[0012] Where, I represents the total current flowing through the N load branches, n represents a positive integer not greater than N, and I n represents the load operating current of the nth load branch among the N load branches, K n represents a dimming coefficient corresponding to the nth load branch;

[0013] The current regulating module is used to regulate the total current flowing through the N load branches according to the control signal so as to make the voltages at both ends of the N load branches match the voltage of the voltage output end.

[0014] Based on the above invention, a load driving scheme for multi-channel synchronous dimming based on dimming signal coupling technology is provided, which includes a voltage control module, multiple load branches, a current regulation module, a dimming signal output module and a dimming signal coupling module, wherein the load branch includes a load and a switch tube electrically connected in series, the dimming signal output module is used to input a PWM signal for independently dimming the corresponding load to each load branch in the multiple load branches, and the dimming signal coupling module is used to couple the multiple PWM signals into a control signal for overall dimming of the multiple load branches and output it. The current regulation module is used to achieve load matching and adjust the total current flowing through the multiple load branches according to the control signal. This not only can achieve single-channel and arbitrarily multi-channel dimming without mutual influence under the condition of unchanged output power, but also can make the cost of adding an additional channel limited to adding a switch tube instead of a whole circuit device, and in the subsequent circuit, it is an inductor-free application, and will not cause strong EMC problems like the inductor in DC-DC applications. Therefore, in practical applications, the volume and cost control of the driving power supply can be significantly advantageous, which is convenient for practical application and promotion.

[0015] In a possible design, when the voltage control module has an output voltage adjustment feedback port, it also includes a signal sampling and trimming module, a signal processing module and a feedback module, wherein the signal input end of the signal sampling and trimming module is connected to the negative terminal, the signal output end of the signal sampling and trimming module is connected to the signal input end of the signal processing module, the signal output end of the signal processing module is connected to the second signal input end of the feedback module, the communication end of the signal processing module is connected to the current regulation module, the first signal input end of the feedback module is connected to the voltage output end, and the signal output end of the feedback module is connected to the output voltage adjustment feedback port;

[0016] The signal sampling and trimming module is used to perform trimming processing on the second sampling signal from the negative terminal, and send the trimmed signal obtained by processing to the signal processing module, wherein the trimming processing includes filtering processing, voltage division and limiting processing, and integration processing performed in sequence;

[0017] The signal processing module is used to perform signal processing on the trimmed signal according to the control signal from the current regulation module to obtain a mixed signal whose frequency component is nonlinearly negatively correlated with the total load current after dimming, and send the mixed signal to the feedback module;

[0018] The feedback module is used to superimpose the mixed signal and the first sampling signal from the voltage output end and feed them into the output voltage adjustment feedback port, so that the voltage control module dynamically adjusts the output voltage according to the fed-in signal, so that during the entire dimming process, the difference between the output voltage of the voltage control module and the voltage at both ends is always in a constant state preset by the circuit.

[0019] In one possible design, the signal processing module is also used to trigger sending an alarm signal to the current regulation module when the second sampling signal or the mixed signal is found to be abnormal, so that when the current regulation module receives the alarm signal, it adjusts the total current flowing through the N load branches to zero, thereby achieving the purpose of protecting the load by shutting off the current.

[0020] In a possible design, the trimmed signal is processed according to the control signal from the current regulating module to obtain a mixed signal whose frequency component is nonlinearly negatively correlated with the total current of the load after dimming, including:

[0021] According to the control signal from the current regulation module, some frequency components in the trimmed signal are attenuated to a degree that is nonlinearly negatively correlated with the total current of the load after dimming, so as to obtain a mixed signal whose frequency components are nonlinearly negatively correlated with the total current of the load after dimming, and when the total current of the load after dimming is in a completely dimmed-off state, all frequency components in the trimmed signal are completely attenuated so that no signal is output to the feedback module.

[0022] In a possible design, sending the mixed signal to the feedback module includes:

[0023] After performing at least one integration process on the mixed signal, the mixed signal is amplified and sent to the feedback module.

[0024] In a possible design, the signal sampling method of the signal sampling and trimming module is a direct sampling method or an indirect sampling method, wherein the direct sampling method includes a resistor voltage division and current shunt sampling method, a transistor current shunt sampling method, an operational amplifier lossless sampling method, an optocoupler isolation sampling method and / or a digital sampling method based on an MCU chip, and the indirect sampling method refers to a sampling method that increases the voltage through voltage superposition processing technology.

[0025] In one possible design, the voltage control module adopts a switching power supply including an inductive element circuit unit and a switch control circuit unit, wherein the inductive element circuit unit includes an inductor and / or a transformer, and the controlled end of the switch control circuit unit serves as an output voltage adjustment feedback port.

[0026] In one possible design, the current regulation module includes an integrated current stabilization circuit unit and a logic judgment unit, wherein the current stabilization circuit unit is used to draw the current flowing through the load to ground, and the logic judgment unit is used to adjust the total current flowing through the N load branches according to the control signal.

[0027] In one possible design, the dimming signal output module uses a wireless remote control circuit based on 2.4Ghz wireless technology, WiFi wireless technology, Bluetooth wireless technology and / or DALI wireless technology.

[0028] In a possible design, the switch tube is a transistor, a metal oxide semiconductor field effect transistor, an insulated gate bipolar transistor or a silicon controlled thyristor.

[0029] The beneficial effects of the present invention are:

[0030] (1) The present invention provides a load driving scheme for multi-channel synchronous dimming based on dimming signal coupling technology, which includes a voltage control module, multiple load branches, a current regulation module, a dimming signal output module and a dimming signal coupling module, wherein the load branch includes a load and a switch tube electrically connected in series, the dimming signal output module is used to input a PWM signal for independently dimming the corresponding load to each of the multiple load branches, and the dimming signal coupling module is used to couple the multiple PWM signals into a control signal for overall dimming of the multiple load branches and output it. The current regulating module is used to achieve load matching and adjust the total current flowing through the multiple load branches according to the control signal. In this way, not only can the single-channel and any multi-channel dimming be achieved without mutual influence under the condition of unchanged output power, but also the cost of adding an additional channel is limited to adding a switch tube instead of a whole circuit device, and in the subsequent circuit, there is no inductor application, which will not cause strong EMC problems like the inductor in DC to DC applications. Therefore, in practical applications, the volume and cost control of the driving power supply can be significantly advantageous, which is convenient for practical application and promotion;

[0031] (2) Through the configuration of the signal sampling and trimming module, the signal processing module and the feedback module, the difference between the output voltage of the voltage control module and the voltage across the load can be always in a constant state preset by the circuit during the entire dimming process, thereby achieving the goal of the output voltage of the front-stage circuit and the output current of the rear-stage circuit being stable and without fluctuation, and the rear-stage circuit being always in a high-efficiency working state, thereby effectively improving the dimming performance;

[0032] (3) The current size of each channel can be independently controlled and adjusted by PWM to achieve high-precision color temperature / color difference control;

[0033] (4) Since this circuit has no electrolytic capacitors and inductors in the later stage, it can be easily made into an integrated circuit and modularized to achieve ultra-small size, low cost and high power drive applications;

[0034] (5) Since this circuit has no inductance in the later stage, it is of great help to solve the EMC problem of the driver. It not only reduces the EMC cost of the whole machine, but also accelerates the design of the solution and the stability and anti-interference of the driver.

[0035] (6) Since the current regulation action of the subsequent stage is synchronized with the high level of the dimming signal, and when any dimming signal is at a high level, the subsequent stage has current output, and vice versa, it can be supplied as needed, thereby achieving good dimming performance and effective protection function;

[0036] (7) It can have multi-channel, precise control, and synchronization of dimming and constant current, and realize the load abnormality protection function of any channel. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 It is a structural schematic diagram of a multi-channel synchronous dimming circuit provided by the present invention.

[0039] Figure 2 It is a structural schematic diagram of a multi-channel synchronous dimming circuit using an indirect sampling method provided by the present invention.

[0040] Figure 3 This is a first waveform timing example diagram of the dimming signal coupling processing provided by the present invention.

[0041] Figure 4 This is a second waveform timing example diagram of the dimming signal coupling processing provided by the present invention. DETAILED DESCRIPTION

[0042] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be noted that although the description of these embodiments is used to help understand the present invention, it does not constitute a limitation of the present invention. The specific structures and functional details disclosed herein are only used to describe the exemplary embodiments of the present invention. However, the present invention can be embodied in many alternative forms, and it should not be understood that the present invention is limited to the embodiments set forth herein.

[0043] It should be understood that although the terms first and second, etc. may be used herein to describe various objects, these objects should not be limited by these terms. These terms are only used to distinguish one object from another object. For example, a first object can be referred to as a second object, and similarly, a second object can be referred to as a first object without departing from the scope of the exemplary embodiments of the present invention.

[0044] It should be understood that the term "and / or" that may appear in this article is merely a description of the association relationship between associated objects, indicating that there may be three relationships. For example, A and / or B can represent three situations: A exists alone, B exists alone, or A and B exist at the same time; the term " / and" that may appear in this article describes another type of association object relationship, indicating that there may be two relationships. For example, A / and B can represent two situations: A exists alone or A and B exist at the same time; in addition, the character " / " that may appear in this article generally indicates that the previous and next associated objects are in an "or" relationship.

[0045] Embodiment 1

[0046] like Figure 1 As shown, the multi-channel synchronous dimming circuit provided in this embodiment includes but is not limited to a voltage control module, N load branches, a current regulation module, a dimming signal output module and a dimming signal coupling module, wherein the load branch includes a load and a switch tube (K1 / K2 / KN) electrically connected in series, N represents a positive integer not less than 2, and the load is a light-emitting lamp; the voltage control module is used to convert the input voltage into a DC voltage and output it; the positive terminals of the N load branches are respectively connected to the voltage output terminal V0 of the voltage control module, the negative terminals V1 of the N load branches are respectively connected to one end of the current regulation module, and the other end of the current regulation module is grounded; N PWM (Pulse Width The PWM signal output terminals are connected to the controlled terminals of the switch tubes in the N load branches one by one, and the N PWM signal output terminals are also connected to the N signal input terminals of the dimming signal coupling module one by one, and the signal output terminal of the dimming signal coupling module is connected to the dimming signal input terminal of the current regulation module; the dimming signal output module is used to input a PWM signal for independently dimming the corresponding load to each load branch in the N load branches; the dimming signal coupling module is used to couple the PWM signals from the N PWM signal output terminals into a control signal for overall dimming of the N load branches and output it, wherein the overall dimming coefficient K of the control signal satisfies:

[0047] K=(K1*I1+K2*I2+…+K n *I n +…+K N *I N ) / I

[0048] Where, I represents the total current flowing through the N load branches, n represents a positive integer not greater than N, and I n represents the load operating current of the nth load branch among the N load branches, K n represents a dimming coefficient corresponding to the nth load branch;

[0049] The current regulating module is used to regulate the total current flowing through the N load branches according to the control signal so as to make the voltages at both ends of the N load branches match the voltage of the voltage output terminal (V0).

[0050] like Figure 1As shown, in the specific structure of the multi-channel synchronous dimming circuit, the topology of the voltage control module can be but not limited to a buck, boost or buck-boost circuit structure, and the specific forms include but are not limited to isolation, non-isolation, flyback or forward, etc. In order to dynamically adjust the output voltage by feedback, the voltage control module preferably requires an output voltage adjustment feedback port FB, that is, the voltage control module can be but not limited to a switching power supply including an inductive element circuit unit (represented by HP in the figure) and a switch control circuit unit, wherein the inductive element circuit unit includes but is not limited to an inductor and / or a transformer, etc., and the controlled end of the switch control circuit unit serves as the output voltage adjustment feedback port FB. The switching power supply can be, but is not limited to, various existing buck, boost or buck-boost circuits that implement flyback / forward and have the output voltage adjustment feedback port FB. Regardless of whether it is a high PFC (Power Factor Correction) application or a low PFC application, an isolated application or a non-isolated application, and whether the power range is high power or low power, as long as it has the output voltage adjustment feedback port FB, it can be linked with the subsequent circuit (such as the current regulation module) to achieve the corresponding voltage control application. The input voltage is represented by VIN in the accompanying drawings, which can be an AC voltage or a DC voltage. The switch control circuit unit can be, but is not limited to, using an existing circuit structure based on a control chip, a switch tube, and a drive circuit to realize the function of dynamically adjusting the output voltage according to the feed-in signal. In addition, the voltage output terminal V0 of the voltage control module can be specifically connected to the positive ends of the N load branches through a bus.

[0051] The load may specifically include various types of linear loads or nonlinear loads that require constant current operation, such as LED (Light-Emitting Diode) lamps and other light-emitting lamps. The switch tube (K1 / K2 / KN) is used to be responsible for the conduction / disconnection of the corresponding load branch, which may be, but not limited to, a crystal triode, a metal oxide semiconductor field effect transistor, an insulated gate bipolar transistor or a thyristor. Since the N load branches are electrically connected in parallel between the voltage output terminal V0 and the negative terminal V1, in each load branch, the corresponding load can be independently dimmed by the corresponding switch tube based on the input corresponding PWM signal. The voltage at both ends of each load branch is the voltage difference between the voltage output terminal V0 and the negative terminal V1. The voltage at both ends can range from a low voltage of a few volts to a high voltage of hundreds of volts. The current flowing through the load can be from a few milliamperes to a few amperes, and the working power of the load can be from a few watts to a few hundred watts. In addition, if the light-emitting lamp is replaced by a battery, a heating wire, a pure resistor, etc., a multi-channel synchronous current regulation circuit can also be obtained.

[0052] The current regulation module specifically includes but is not limited to an integrated current stabilization circuit unit and a logic judgment unit, wherein the current stabilization circuit unit is used to achieve load matching and lead the current flowing through the load to the ground, and the logic judgment unit is used to adjust the total current flowing through the N load branches according to the control signal, thereby taking into account various protections required for dimming and load constant current operation. Since the negative terminal V1 is a node of voltage to ground, and its voltage value is the difference between the voltage of the voltage output terminal V0 and the voltage of the two ends of the N load branches, it can directly reflect the matching of the current voltage at both ends of the N load branches with the voltage of the voltage output terminal V0. For example, when the voltage of the voltage output terminal V0 is greater than the voltage at both ends of the N load branches, the voltage of the negative terminal V1 is also greater, and when the voltage of the voltage output terminal V0 is equal to the voltage at both ends of the N load branches, the voltage of the negative terminal V1 is approximately equal to 0V (at this time, the voltage at both ends of the N load branches matches the voltage of the voltage output terminal V0, that is, load matching is achieved). In addition, the control signal may be, but is not limited to, an analog signal, a digital signal or a PWM signal, and the current stabilization circuit unit may be implemented using an existing adjustable constant current circuit.

[0053] The dimming signal output module is responsible for generating PWM signals for executing corresponding dimming actions for each load branch; in order to achieve the purpose of remote control dimming, the dimming signal output module preferably adopts a remote control circuit based on 2.4Ghz wireless technology, WiFi wireless technology, Bluetooth wireless technology and / or DALI (Digital Addressable Lighting Interface, Chinese translation of digital addressable lighting interface, is a data transmission protocol that defines the communication method between electronic ballast and device controller) communication technology. In addition, the power supply end of the dimming signal output module can be connected to an independent power supply VDD, or it can be directly connected to the voltage output end V0; the grounding end of the dimming signal output module can be independently grounded, or it can be directly connected to the negative terminal V1, such as Figure 1 shown.

[0054] The dimming signal coupling module is responsible for fully synchronizing the dimming actions of the N load branches with the dimming actions of the current regulation module, that is, when any one or several load branches perform a dimming action (which is performed by inputting a PWM signal for independent dimming at the controlled end of the corresponding switch tube), by adopting a multi-channel dimming signal coupling technology, the input PWM signals of these load branches are merged into a single control signal and given to the current regulation module, so that it cooperates with the dimming action of any one or several load branches to turn on / off the output current, ensuring that the associated actions at the two locations are high-speed responsive, without delay and stagnation. Specifically, when any PWM signal is valid, the output current is immediately turned on, otherwise the output current is immediately turned off, so that it is turned on immediately when it should be turned on, and turned off immediately when it should be turned on. This has a very great effect on current overshoot, load abnormality protection and standby power consumption.

[0055] The multi-channel dimming signal coupling technology can be specifically performed by performing "OR gate" logic processing on the PWM signals from the N PWM signal output terminals (i.e., superimposing each PWM signal for independent dimming in a unit cycle time, such as Figure 3 Or as shown in 4, it becomes a new control signal, which can be in the form of high or low level, or it can continue to be a PWM waveform). After receiving the control signal in the form of high or low level or PWM waveform, the current regulation module can use its effective level to control the opening and closing of the constant current source. For example, for high-level effective applications, when the control signal is at a high level, the constant current source starts to work and outputs current, otherwise the constant current source is turned off and no current is output; this action completely synchronizes the PWM signals of the N PWM signal output ends, and the constant current is turned on when there is a signal, and the constant current is turned off when there is no signal, which can well avoid some unnecessary opening or malfunction; it can achieve precise upper and lower linkage effects, especially in dimming and color adjustment applications, with excellent dimming performance effects; and the application is very flexible, and two-way CW dimming and color adjustment, RGB dimming or CW+RGB dimming can be easily realized. At the same time, since the cost of adding an extra channel (i.e., a load branch) is limited to adding a switch tube instead of a whole circuit device, and there is no inductor in the subsequent circuit, it will not cause strong EMC problems like the inductor in DC-to-DC applications. Therefore, in practical applications, the volume and cost control of the driving power supply can have significant advantages, that is, any number of channels can be easily realized at a very low cost. In addition, the dimming coefficient refers to the multiple by which the load operating current is reduced, which can also be called the dimming depth. Its value range is [0,1]. When the dimming coefficient is 0, it is in the dimming off state.

[0056] Preferably, when the voltage control module has an output voltage adjustment feedback port FB, it also includes a signal sampling and trimming module, a signal processing module and a feedback module, wherein the signal input end of the signal sampling and trimming module is connected to the negative terminal V1, the signal output end of the signal sampling and trimming module is connected to the signal input end of the signal processing module, the signal output end of the signal processing module is connected to the second signal input end of the feedback module, the communication end of the signal processing module is connected to the current regulation module, the first signal input end of the feedback module is connected to the voltage output end V0, and the signal output end of the feedback module is connected to the output voltage adjustment feedback port FB; the signal sampling and trimming module is used to perform trimming processing on the second sampling signal from the negative terminal V1, and send the trimmed signal obtained by processing to the signal processing module Module, wherein the trimming process includes but is not limited to filtering process, voltage division and voltage limiting process and integration process performed in sequence; the signal processing module is used to perform signal processing on the trimmed signal according to the control signal from the current regulation module to obtain a mixed signal whose frequency component is nonlinearly negatively correlated with the total load current after dimming, and send the mixed signal to the feedback module; the feedback module is used to superimpose the mixed signal and the first sampling signal from the voltage output terminal V0 and feed it into the output voltage adjustment feedback port FB, so that the voltage control module dynamically adjusts the output voltage according to the fed-in signal, so that in the entire dimming process (i.e., the dimming depth is from 0% to 100%), the difference between the output voltage of the voltage control module and the voltage at both ends is always in a constant state preset by the circuit.

[0057] The signal sampling mode of the signal sampling and trimming module is a direct sampling mode or an indirect sampling mode. The direct sampling mode includes but is not limited to a resistor voltage division and current shunting sampling mode, a transistor current shunting sampling mode, an operational amplifier lossless sampling mode, an optocoupler isolation sampling mode and / or a digital sampling mode based on an MCU (Microcontroller Unit) chip, etc., which can be applied to the case where the voltage of the negative terminal V1 is relatively high, so that even after the voltage division and current shunting process, there is still a relatively high voltage component to meet the subsequent trimming process. The indirect sampling mode refers to a sampling mode that uses a voltage superposition processing technology to increase the voltage, that is, for the scenario where the voltage of the negative terminal V1 is relatively low, considering that its voltage component after direct sampling cannot meet the trimming process of the subsequent circuit, it is necessary to superimpose a fixed voltage Vg on the voltage of the negative terminal V1. The voltage Vg can be set according to the actual application, and can be obtained by various circuits that can achieve constant voltage output, such as a voltage regulator diode, a transistor, or even an LDO (Low Dropout Regulator, linear voltage regulator circuit) regulator, combined with the voltage of the voltage output terminal V0, that is, Figure 2 As shown, the final output voltage signal Vx is equal to the sum of the voltage of the negative terminal V1 and the voltage Vg. Therefore, regardless of the direct sampling method or the indirect sampling method, the voltage signal of the negative terminal V1 can be accurately collected in the end.

[0058] Since the load operates in a stable constant current state when not dimming, that is, the voltages at both ends of the N load branches are also in a constant state. If it is described in detail as the load of an LED lamp, the LED lamp is constant current and has no flicker. Therefore, it can be inferred that: when the entire circuit is stable, the voltage at the negative terminal V1 is also a relatively stable value, that is, the waveform should be the result of subtracting the voltages at both ends of the N load branches from the ripple waveform voltage at the voltage output terminal V0. For a single-stage high PFC project, the ripple in the ripple waveform voltage is an industrial frequency ripple, and if it is a two-stage topology or a low PFC structure, the ripple is a DC voltage. At the same time, during the dimming process, the voltage at the negative terminal V1 will have a high-frequency component superimposed on the waveform when not dimming. This high-frequency component is consistent with the PWM pulse frequency of the control signal (generally several kHz to tens of kHz). At this time, the voltage at the negative terminal V1 is composed of three components: the ripple waveform voltage of the voltage output terminal V0, the voltages at both ends of the N load branches, and the high-frequency component; and as the dimming depth is different, the ripple in the ripple waveform voltage will change accordingly, and the voltages at both ends of the N load branches will also be affected by this. In order to ensure the continuity and consistency of the ripple voltage at the voltage output terminal V0 and the voltages at both ends of the N load branches at different dimming depths, it is necessary to perform a series of trimming processes on the sampled signal waveform, the first of which is filtering (i.e. removing interference signals and some high-frequency components); the second is voltage division and voltage limiting (i.e. the voltage division is for the convenience of circuit processing, and the voltage limiting is to deal with the damage to the circuit caused by the excessive voltage at the negative terminal V1, such as when the load is abnormal, the voltage at the negative terminal V1 will become very high); the last is integration processing (i.e. removing the influence of power frequency ripple).

[0059] Considering that the voltage signal of the negative terminal V1 will become extremely complex and changeable during dimming, and is directly related to the control signal, in order to make the voltages at both ends of the N load branches accurately match the voltage of the voltage output terminal V0, it is necessary to perform a part of the frequency component attenuation processing on the current trimmed signal according to the control signal to ensure that the mixed signal given to the feedback module will not be distorted and overshot, that is, according to the control signal from the current regulation module, the trimmed signal is processed to obtain a mixed signal whose frequency component is nonlinearly negatively correlated with the total current of the load after dimming, including but not limited to: according to the control signal from the current regulation module, attenuation processing is performed on some frequency components in the trimmed signal whose attenuation degree is nonlinearly negatively correlated with the total current of the load after dimming, to obtain a mixed signal whose frequency component is nonlinearly negatively correlated with the total current of the load after dimming, and when the total current of the load after dimming is in a completely dimmed-off state, all frequency components in the trimmed signal are completely attenuated so that no signal is output to the feedback module. In addition, the mixed signal is sent to the feedback module, including but not limited to: after the mixed signal is integrated at least once, it is amplified (i.e., the signal obtained by the integration processing is amplified again) and sent to the feedback module, wherein the purpose of the at least one integration processing is to ensure the integrity and dynamics of the mixed signal, and it can also prevent signal distortion and overshoot, which is the key point of the stability of the entire circuit. In addition, before the signal processing module performs signal processing on the trimmed signal, it can also first perform current limiting and integration processing on the trimmed signal, that is, due to the complexity of the voltage and current of the negative terminal V1 in the change amplitude and waveform, it is necessary to further thoroughly eliminate interference clutter and abnormal waveforms to prepare for the next signal processing.

[0060] In summary, the working process of the signal sampling and trimming module, the signal processing module and the feedback module includes but is not limited to the following two logics:

[0061] (A) The matching logic between the voltage of the voltage output terminal V0 and the voltages at both ends of the N load branches, that is, this logic is based on non-dimming, and its action path is to first sample the voltage signal of the negative terminal V1 and complete the corresponding trimming and other processing to obtain a positively correlated and amplified mixed signal. From the above, it can be understood that when the voltage of the negative terminal V1 increases, it means that the voltages at both ends of the N load branches decrease. If it is not adjusted at this time, the power consumption generated by the voltage of the negative terminal V1 multiplied by the current will be dissipated by the current regulation module, causing the temperature of the current regulation module to rise or even burn out; at this time, through the reverse The feedback module superimposes the mixed signal and the first sampling signal from the voltage output terminal V0 and feeds them into the output voltage adjustment feedback port FB. The voltage control module can be used to reduce the voltage of the voltage output terminal V0, so that the voltage of the negative terminal V1 will also be reduced to a preset value accordingly. Conversely, the voltage of the voltage output terminal V0 is increased to increase the voltage of the negative terminal V1, so that the current regulation module works normally and does not enter a non-constant current state. In this way, the current regulation module can be dynamically and continuously kept in the best working state at all times, and the stability and good working efficiency of the entire voltage control function circuit are also guaranteed;

[0062] (B) The logic of dynamically adjusting the voltage of the voltage output terminal V0 during the dimming process, that is, adding a dimming state on the basis of non-dimming. Although only the dimming state is added, the complexity of the entire circuit has increased a lot. It can be divided into two states for explanation. The first is the dimming state, and the second is the complete dimming-off state (even if all loads are dimmed off). Complete dimming-off is an extreme case of dimming, so the impact of this complete dimming-off state on the entire circuit is also extreme. In the dimming state, since the voltage waveform of the negative terminal V1 will be superimposed with high-frequency ripples, this high-frequency ripple can be regarded as a high-frequency square wave superimposed with low-frequency ripples after sampling and trimming processing, and when the total load current size / dimming brightness after dimming becomes lower and lower, the amplitude of this waveform will increase accordingly. In this way, after sampling and trimming processing, the signal will show an upward trend as the total load current after dimming becomes lower, and eventually the voltage of the voltage output terminal V0 will decrease as the total load current after dimming becomes smaller, which has a significant adverse effect on the dimming effect. At this time, it is necessary to adjust the voltage waveform according to the control signal. The second sampling signal from the negative terminal V1 is processed to obtain a mixed signal whose frequency component (i.e., the vibration amplitude of the frequency point signal) is nonlinearly negatively correlated with the total current of the load after dimming, so as to offset the influence of a part of the rising trend; and as the total current after dimming becomes smaller, the more frequency components of the mixed signal will be extracted by the low level, so that it will remain unchanged or even show a downward trend (here, this adjustment can be achieved by setting a suitable attenuation parameter), and finally the voltage of the voltage output terminal V0 will remain unchanged or show an upward trend, so that the dimming effect is fully guaranteed. In the completely dimmed-out state, since the total current of the load after dimming is zero at this time, the frequency component extracted in the mixed signal is also the largest. In order to ensure that the frequency component extracted by the mixed signal can be arbitrarily set, it is necessary to add a corresponding circuit to make a logical judgment, so that it can be ensured that the signal given to the feedback module in the completely dimmed-out state is lower than the threshold, that is, at this time, the feedback module only receives the first sampling signal from the voltage output terminal V0, which makes the voltage control module output the highest voltage and the no-load voltage. In addition, if the total current is increased from 0 after dimming, the logical processing process is the opposite of the above description, which will not be repeated here; and during the entire dimming process, the difference between the output voltage of the voltage control module and the voltage at both ends is always in a constant state preset by the circuit. The specific manifestation is: during the entire dimming process, the output voltage of the voltage control module is stable and has no fluctuations (that is, including stable rise, stable fall and stable maintenance), the output current of the current regulation module is stable and has no fluctuations (that is, including stable rise, stable fall and stable maintenance), and the current regulation module is in a high-efficiency working state (that is, the negative terminal V1 will always be in a low-voltage state, the internal power dissipation is low, and thus it can work efficiently).

[0063] Preferably, the signal processing module is further configured to trigger sending an alarm signal to the current regulating module when the second sampling signal or the mixed signal is found to be abnormal, so that the current regulating module adjusts the total current flowing through the N load branches to zero upon receiving the alarm signal, thereby protecting the load by shutting off the current. Figure 1 As shown, the aforementioned current shut-off action can be executed by the logic judgment unit. For example, when it is found that the voltages at both ends of the N load branches are smaller than the preset value or even 0 (i.e., short circuit), the aforementioned current shut-off action can be used to achieve the purpose of load abnormality protection.

[0064] In summary, the multi-channel synchronous dimming circuit provided by this embodiment has the following technical effects:

[0065] (1) This embodiment provides a load driving scheme for multi-channel synchronous dimming based on dimming signal coupling technology, that is, it includes a voltage control module, multiple load branches, a current regulation module, a dimming signal output module and a dimming signal coupling module, wherein the load branch includes a load and a switch tube electrically connected in series, the dimming signal output module is used to input a PWM signal for independently dimming the corresponding load to each of the multiple load branches, and the dimming signal coupling module is used to couple the multiple PWM signals into a control signal for overall dimming of the multiple load branches and output it. The current regulating module is used to achieve load matching and adjust the total current flowing through the multiple load branches according to the control signal. In this way, not only can the single-channel and any multi-channel dimming be achieved without mutual influence under the condition of unchanged output power, but also the cost of adding an additional channel is limited to adding a switch tube instead of a whole circuit device, and in the subsequent circuit, there is no inductor application, which will not cause strong EMC problems like the inductor in DC to DC applications. Therefore, in practical applications, the volume and cost control of the driving power supply can be significantly advantageous, which is convenient for practical application and promotion;

[0066] (2) Through the configuration of the signal sampling and trimming module, the signal processing module and the feedback module, the difference between the output voltage of the voltage control module and the voltage across the load can be always in a constant state preset by the circuit during the entire dimming process, thereby achieving the goal of the output voltage of the front-stage circuit and the output current of the rear-stage circuit being stable and without fluctuation, and the rear-stage circuit being always in a high-efficiency working state, thereby effectively improving the dimming performance;

[0067] (3) The current size of each channel can be independently controlled and adjusted by PWM to achieve high-precision color temperature / color difference control;

[0068] (4) Since this circuit has no electrolytic capacitors and inductors in the later stage, it can be easily made into an integrated circuit and modularized to achieve ultra-small size, low cost and high power drive applications;

[0069] (5) Since this circuit has no inductance, it is of great help to solve the EMC problem of the driver. It not only reduces the EMC cost of the whole machine, but also accelerates the design of the solution and the stability and anti-interference of the driver.

[0070] (6) Since the current regulation action of the subsequent stage is synchronized with the high level of the dimming signal, and when any dimming signal is at a high level, the subsequent stage has current output, and vice versa, it can be supplied as needed, thereby achieving good dimming performance and effective protection function;

[0071] (7) It can have multi-channel, precise control, and synchronization of dimming and constant current, and realize the load abnormality protection function of any channel.

[0072] Finally, it should be noted that the present invention is not limited to the above optional implementations, and anyone can derive other various forms of products under the enlightenment of the present invention. The above specific implementations should not be understood as limiting the scope of protection of the present invention. The scope of protection of the present invention should be based on the definition in the claims, and the description can be used to interpret the claims.

Claims

1. A multi-channel synchronous dimming circuit, characterized in that: It includes a voltage control module, N load branches, a current regulation module, a dimming signal output module and a dimming signal coupling module, wherein the load branch includes a load and a switch tube electrically connected in series, N represents a positive integer not less than 2, and the load is a light-emitting lamp; The voltage control module is used to convert the input voltage into a DC voltage and output it; The positive terminals of the N load branches are respectively connected to the voltage output terminal (V0) of the voltage control module, the negative terminals (V1) of the N load branches are respectively connected to one end of the current regulation module, and the other end of the current regulation module is grounded; The N PWM signal output ends of the dimming signal output module are connected to the controlled ends of the switch tubes in the N load branches one by one, and the N PWM signal output ends are also connected to the N signal input ends of the dimming signal coupling module one by one, and the signal output end of the dimming signal coupling module is connected to the dimming signal input end of the current regulation module; The dimming signal output module is used to input a PWM signal for independently dimming the corresponding load to each of the N load branches; The dimming signal coupling module is used to couple the PWM signals from the N PWM signal output terminals into a control signal for overall dimming of the N load branches and output the control signal, wherein the overall dimming coefficient K of the control signal satisfies: K=(K1*I1+K2*I2+…+K n *I n +…+K N *I N ) / I Where, I represents the total current flowing through the N load branches, n represents a positive integer not greater than N, and I n represents the load operating current of the nth load branch among the N load branches, K n represents a dimming coefficient corresponding to the nth load branch; The current regulating module is used to regulate the total current flowing through the N load branches according to the control signal so as to make the voltages at both ends of the N load branches match the voltage of the voltage output terminal (V0); When the voltage control module has an output voltage adjustment feedback port (FB), the multi-channel synchronous dimming circuit further includes a signal sampling and trimming module, a signal processing module and a feedback module, wherein the signal input end of the signal sampling and trimming module is connected to the negative terminal (V1), the signal output end of the signal sampling and trimming module is connected to the signal input end of the signal processing module, the signal output end of the signal processing module is connected to the second signal input end of the feedback module, the communication end of the signal processing module is connected to the current regulation module, the first signal input end of the feedback module is connected to the voltage output end (V0), and the signal output end of the feedback module is connected to the output voltage adjustment feedback port (FB); The signal sampling and trimming module is used to perform trimming processing on the second sampling signal from the negative terminal (V1), and send the trimmed signal obtained by processing to the signal processing module, wherein the trimming processing includes filtering processing, voltage division and limiting processing, and integration processing performed in sequence; The signal processing module is used to perform signal processing on the trimmed signal according to the control signal from the current regulating module to obtain a mixed signal whose frequency component is nonlinearly negatively correlated with the total current of the load after dimming, and send the mixed signal to the feedback module, wherein the signal processing on the trimmed signal according to the control signal from the current regulating module to obtain a mixed signal whose frequency component is nonlinearly negatively correlated with the total current of the load after dimming specifically includes: according to the control signal from the current regulating module, performing attenuation processing on some frequency components in the trimmed signal with an attenuation degree nonlinearly negatively correlated with the total current of the load after dimming to obtain a mixed signal whose frequency component is nonlinearly negatively correlated with the total current of the load after dimming, and when the total current of the load after dimming is in a completely dimmed-off state, performing complete attenuation processing on all frequency components in the trimmed signal so that no signal is output to the feedback module; The feedback module is used to superimpose the mixed signal and the first sampling signal from the voltage output terminal (V0) and feed them into the output voltage adjustment feedback port (FB), so that the voltage control module dynamically adjusts the output voltage according to the fed-in signal, so that during the entire dimming process, the difference between the output voltage of the voltage control module and the voltage at both ends is always in a constant state preset by the circuit.

2. The multi-channel synchronous dimming circuit according to claim 1, characterized in that: The signal processing module is also used to trigger the sending of an alarm signal to the current regulation module when the second sampling signal or the mixed signal is found to be abnormal, so that the current regulation module adjusts the total current flowing through the N load branches to zero when receiving the alarm signal, thereby achieving the purpose of protecting the load by shutting off the current.

3. The multi-channel synchronous dimming circuit according to claim 1, characterized in that: Sending the mixed signal to the feedback module comprises: After performing at least one integration process on the mixed signal, the mixed signal is amplified and sent to the feedback module.

4. The multi-channel synchronous dimming circuit according to claim 1, characterized in that: The signal sampling method of the signal sampling and trimming module is a direct sampling method or an indirect sampling method, wherein the direct sampling method includes a resistor voltage division and current shunt sampling method, a transistor current shunt sampling method, an operational amplifier lossless sampling method, an optocoupler isolation sampling method and / or a digital sampling method based on an MCU chip, and the indirect sampling method refers to a sampling method that increases the voltage through voltage superposition processing technology.

5. The multi-channel synchronous dimming circuit according to claim 1, characterized in that: The voltage control module adopts a switching power supply including an inductive element circuit unit and a switch control circuit unit, wherein the inductive element circuit unit includes an inductor and / or a transformer, and the controlled end of the switch control circuit unit serves as an output voltage adjustment feedback port (FB).

6. The multi-channel synchronous dimming circuit according to claim 1, characterized in that: The current regulation module includes an integrated current stabilization circuit unit and a logic judgment unit, wherein the current stabilization circuit unit is used to lead the current flowing through the load to the ground, and the logic judgment unit is used to adjust the total current flowing through the N load branches according to the control signal.

7. The multi-channel synchronous dimming circuit according to claim 1, characterized in that: The dimming signal output module adopts a wireless remote control circuit based on 2.4Ghz wireless technology, WiFi wireless technology, Bluetooth wireless technology and / or DALI wireless technology.

8. The multi-channel synchronous dimming circuit according to claim 1, characterized in that: The switch tube is a crystal triode, a metal oxide semi-conductor field effect transistor, an insulated gate bipolar transistor or a silicon controlled thyristor.

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