CN114867154A - Multichannel synchronous dimming circuit - Google Patents

Abstract

The invention relates to the technical field of load driving, and discloses a multichannel synchronous dimming circuit which comprises a voltage control module, a plurality of load branches, a current regulation module, a dimming signal output module and a dimming signal coupling module, wherein the load branches comprise loads and switching tubes which are electrically connected in series, the dimming signal output module is used for inputting PWM (pulse width modulation) signals for independently dimming corresponding loads to each load branch, the dimming signal coupling module is used for coupling a plurality of PWM signals into a control signal for carrying out total dimming and outputting the control signal, so that the aims of single-channel dimming and any multichannel dimming without mutual influence can be realized under the condition that the output power is not changed, the cost of adding an additional channel is limited to adding one switching tube, and the application is carried out without inductance in a rear-stage circuit, the method does not generate strong EMC problem, so that the volume and cost control of the driving power supply can have an advantage in practical application.

Description

Multichannel synchronous dimming circuit

Technical Field

The invention belongs to the technical field of load driving, and particularly relates to a multichannel synchronous dimming circuit.

Background

With the demands of higher standards of Light-Emitting Diode (LED) dimming power supply market on dimming depth, multiple channels, no stroboflash output, product cost and the like, the existing technologies/solutions are increasingly difficult to meet the demands, and especially, it is more difficult to obtain proper balance for multi-index high-demand solutions, which is either too high in cost or not high in performance, for example, the contradiction can be more prominent for application of multi-channel dimming and toning/RGB dimming. In detail, the market trend is to require not only no stroboflash, lower THD (Total Harmonic Distortion), higher lighting effect and lower dimming brightness, but also more sensitive to cost, security certification, stability, dimming mode, multiple channels and application scenarios, which are simply required to be satisfied. The requirement of such an integrated structure is met, the realization can be realized without simply taking one scheme or randomly splicing and/or expanding a plurality of schemes, which is a pain point existing in the industry all the time, and the realization can be realized only by starting from a framework and a bottom layer principle.

In another aspect, in terms of specific isolated driving applications, most of the topology structures used in the current single-channel dimming or multi-channel dimming are AC-to-DC (i.e., for achieving the purpose of constant voltage), and then DC-to-DC (i.e., for achieving the purpose of constant current); each output channel needs an independent DC to DC, which results in that in multi-channel applications, the design, volume, cost, processing, reliability, EMC (Electromagnetic Compatibility, which refers to the ability of a device or system to operate in its Electromagnetic environment without generating intolerable Electromagnetic interference to any device in its environment) and certification of a power supply are greatly restricted, especially in high-power applications, even some options are available.

Disclosure of Invention

In order to solve the problem of multi-party restriction in the multi-channel application of the conventional driving circuit, the invention aims to provide a multi-channel synchronous dimming circuit, which can realize the purposes of single-channel and any multi-channel dimming without mutual influence under the condition of unchanged output power, can limit the cost of adding an additional channel to only adding one switching tube instead of a whole circuit device, is applied in a post-stage circuit without inductance, and cannot generate strong EMC (electro magnetic compatibility) problems like inductance in DC-to-DC application, so that the volume and cost control of a driving power supply in practical application has the characteristic of remarkable advantages, and is convenient for practical application and popularization.

The technical scheme adopted by the invention is as follows: a multi-channel synchronous dimming circuit comprises 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 branches comprise a load and a switch tube which are 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 for converting the input voltage into direct current voltage and outputting the direct current voltage;

the positive ends of the N load branches are respectively connected with the voltage output end of the voltage control module, the negative ends of the N load branches are respectively connected with 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 respectively connected with the controlled ends of the switch tubes in the N load branches in a one-to-one correspondence manner, the N PWM signal output ends are also respectively connected with the N signal input ends of the dimming signal coupling module in a one-to-one correspondence manner, and the signal output end of the dimming signal coupling module is connected with the dimming signal input end of the current adjusting module;

the dimming signal output module is configured to input a PWM signal for independently dimming a corresponding load to each load branch of the N load branches;

the dimming signal coupling module is configured to couple the PWM signals from the N PWM signal output ends into a control signal for performing total dimming on the N load branches, and output the control signal, where a total dimming coefficient K of the control signal satisfies:

K＝(K ₁ *I ₁ +K ₂ *I ₂ +…+K _n *I _n +…+K _N *I _N )/I

wherein I represents the total current flowing through the N load branches, N represents a positive integer not greater than N, and I _n Representing a load operating current, K, of an nth load branch of said N load branches _n Representing a dimming coefficient corresponding to the nth load branch;

and the current regulating module is used for regulating the total current flowing through the N load branches according to the control signal so as to enable the voltages at two ends of the N load branches to be matched with the voltage at the voltage output end.

Based on the above disclosure, a load driving scheme for performing multi-channel synchronous dimming based on a dimming signal coupling technology is provided, which includes a voltage control module, a plurality of load branches, a current regulation module, a dimming signal output module and a dimming signal coupling module, where the load branches include a load and a switching tube electrically connected in series, the dimming signal output module is configured to input a PWM signal for performing independent dimming on a corresponding load to each load branch in the plurality of load branches, the dimming signal coupling module is configured to couple a plurality of PWM signals into a control signal for performing total dimming on the plurality of load branches and output the control signal, the current regulation module is configured to implement load matching and adjust the total current flowing through the plurality of load branches according to the control signal, so that under the condition that the output power is not changed, the purpose that single channel and arbitrary multichannel are adjusted luminance and can not influence each other is realized, can also make the cost of adding an extra channel only limit to increase a switch tube, rather than a monoblock circuit device to and there is not inductance application in the back stage circuit, can not produce strong EMC problem like the inductance in the DC changes DC application, consequently can make drive power supply's volume and cost control have the advantage and show the characteristics in practical application, be convenient for practical application and popularization.

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

the signal sampling trimming module is used for trimming a second sampling signal from the negative electrode end and sending the trimmed signal obtained by processing to the signal processing module, wherein the trimming processing comprises filtering processing, voltage division and voltage limitation processing and integration processing which are sequentially carried out;

the signal processing module is used for carrying out signal processing on the trimmed signal according to the control signal from the current regulating module to obtain a mixed signal of which the frequency component is in nonlinear negative correlation with the total load current after dimming, and sending the mixed signal to the feedback module;

the feedback module is configured to feed the mixed signal and a first sampling signal from the voltage output end into the output voltage adjustment feedback port in a superimposed manner, so that the voltage control module dynamically adjusts the output voltage according to the fed signal, and a difference between the output voltage of the voltage control module and the voltages at the two ends is always in a constant state preset by the circuit in the whole dimming process.

In a possible design, the signal processing module is further configured to trigger 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 regulates the total current flowing through the N load branches to zero when receiving the alarm signal, and the purpose of protecting the load by turning off the current is achieved.

In one possible design, the signal processing the trimmed signal according to the control signal from the current adjusting module to obtain a mixed signal with a frequency component that is nonlinearly inversely related to the total current of the load after dimming includes:

and according to the control signal from the current regulation module, carrying out attenuation processing on part of frequency components in the trimmed signal, wherein the attenuation processing is in nonlinear negative correlation with the total load current after dimming, so as to obtain a mixed signal, the frequency components of which are in nonlinear negative correlation with the total load current after dimming, and when the total load current after dimming is in a complete dimming state, carrying out complete attenuation processing on all frequency components in the trimmed signal, so that no signal is output to the feedback module.

In one possible design, feeding the mixed signal into the feedback module includes:

and after the mixed signal is subjected to at least one-time integration processing, the mixed signal is amplified and sent to the feedback module.

In one possible design, the signal sampling mode of the signal sampling trimming module is a direct sampling mode or an indirect sampling mode, wherein the direct sampling mode includes a resistance voltage division shunt sampling mode, a triode shunt sampling mode, an operational amplifier lossless sampling mode, an optical coupling isolation sampling mode and/or a digital sampling mode based on an MCU chip, and the indirect sampling mode is a sampling mode for improving voltage by a voltage superposition processing technology.

In one possible design, the voltage control module employs a switching power supply including an inductive element circuit unit and a switching control circuit unit, where the inductive element circuit unit includes an inductor and/or a transformer, and a controlled terminal of the switching control circuit unit serves as an output voltage regulation feedback port.

In one possible design, the current regulation module includes a current stabilizing circuit unit and a logic judgment unit, which are integrated, wherein the current stabilizing circuit unit is configured to draw a current flowing through the load to ground, and the logic judgment unit is configured to regulate a total current flowing through the N load branches according to the control signal.

In one possible design, the dimming signal output module employs a wireless remote control circuit based on 2.4Ghz wireless technology, WiFi wireless technology, bluetooth wireless technology, and/or DALI wireless technology.

In one possible design, the switch tube is a transistor, a metal oxide semiconductor field effect transistor, an insulated gate bipolar transistor or a thyristor.

The invention has the beneficial effects that:

(1) the invention provides a load driving scheme for multi-channel synchronous dimming based on a dimming signal coupling technology, which comprises a voltage control module, a plurality of load branches, a current regulation module, a dimming signal output module and a dimming signal coupling module, wherein the load branches comprise loads and switching tubes which are electrically connected in series, the dimming signal output module is used for inputting PWM (pulse width modulation) signals for independently dimming corresponding loads to each load branch in the plurality of load branches, the dimming signal coupling module is used for coupling the plurality of PWM signals into a control signal for carrying out total dimming on the plurality of load branches and outputting the control signal, the current regulation module is used for realizing load matching and regulating the total current flowing through the plurality of load branches according to the control signal, so that under the condition that the output power is not changed, the purpose of single-channel and any multi-channel dimming without mutual influence is achieved, the cost of adding an additional channel is limited to adding one switching tube instead of a whole circuit device, and the additional channel is applied in a post-stage circuit without inductance, so that the problem of strong EMC caused by inductance in DC-to-DC application is solved, and therefore, the volume and cost control of the driving power supply has the remarkable advantages in practical application, and the practical application and popularization are facilitated;

(2) through the configuration of the signal sampling trimming module, the signal processing module and the feedback module, the difference value between the output voltage of the voltage control module and the voltage at two ends of the load is always in a constant state preset by the circuit in the whole dimming process, so that the purposes that the output voltage of a front-stage circuit and the output current of a rear-stage circuit are stable and free of fluctuation, and meanwhile, the rear-stage circuit is always in a high-efficiency working state are achieved, and the dimming performance is effectively improved;

(3) the current of each channel can be independently and accurately controlled and adjusted through PWM, and high-precision color temperature/color difference control is realized;

(4) because the circuit has no electrolytic capacitor and no inductance at the rear stage, the circuit can be conveniently made into an integrated circuit and modularized, and the driving application of ultra-small volume, low cost and high power is realized;

(5) because the circuit has no inductance at the rear stage, the circuit has great help to drive the EMC problem, not only reduces the EMC cost of the whole machine, but also accelerates the design of the scheme and the stability and the anti-interference performance of the drive;

(6) because the rear-stage current regulation action is synchronous with the high level of the dimming signal, and when any dimming signal is at the high level, the rear stage outputs current, otherwise, the rear stage does not output current, the current can be supplied at any time, and further good dimming performance and effective protection function are realized;

(7) the load protection circuit has the advantages of multiple channels, accurate control, light dimming and constant current synchronism, and the function of load abnormity protection of any channel is realized.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a multi-channel synchronous dimming circuit provided by the invention.

Fig. 2 is a schematic structural diagram of the multichannel synchronous dimming circuit adopting the indirect sampling mode provided by the invention.

Fig. 3 is a timing diagram of a first waveform of the dimming signal coupling process according to the present invention.

Fig. 4 is a timing diagram of a second waveform of the dimming signal coupling process according to the present invention.

Detailed Description

The invention is further described with reference to the following figures and specific examples. It should be noted that the description of the embodiments is provided to help understanding of the present invention, but the present invention is not limited thereto. Specific structural and functional details disclosed herein are merely illustrative of example embodiments of the invention. This invention may, however, be embodied in many alternate forms and should not be construed as limited to the embodiments set forth herein.

It will be understood that, although the terms first, 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. For example, a first object may be referred to as a second object, and similarly, a second object may be referred to as a first object, without departing from the scope of example embodiments of the present invention.

It should be understood that, for the term "and/or" as may appear herein, it is merely an associative relationship that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, B exists alone or A and B exist at the same time; for the term "/and" as may appear herein, which describes another associative object relationship, it means that two relationships may exist, e.g., a/and B, may mean: a exists singly or A and B exist simultaneously; in addition, for the character "/" that may appear herein, it generally means that the former and latter associated objects are in an "or" relationship.

Example one

As shown in fig. 1, the multichannel 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, where the load branches include a load and a switching tube (K1/K2/KN) electrically connected in series, N represents a positive integer no less than 2, and the load is a light emitting lamp; the voltage control module is used for converting the input voltage into direct current voltage and outputting the direct current voltage; the positive ends of the N load branches are respectively connected with a voltage output end V0 of the voltage control module, the negative ends V1 of the N load branches are respectively connected with one end of the current regulation module, and the other end of the current regulation module is grounded; n PWM (Pulse Width Modulation) signal output ends of the dimming signal output module are respectively connected with the controlled ends of the switch tubes in the N load branches in a one-to-one correspondence manner, the N PWM signal output ends are also respectively connected with N signal input ends of the dimming signal coupling module in a one-to-one correspondence manner, and the signal output end of the dimming signal coupling module is connected with the dimming signal input end of the current adjusting module; the dimming signal output module is configured to input a PWM signal for independently dimming a corresponding load to each load branch of the N load branches; the dimming signal coupling module is configured to couple the PWM signals from the N PWM signal output ends into a control signal for performing total dimming on the N load branches, and output the control signal, where a total dimming coefficient K of the control signal satisfies:

K＝(K ₁ *I ₁ +K ₂ *I ₂ +…+K _n *I _n +…+K _N *I _N )/I

wherein I represents the total current flowing through the N load branches, N represents a positive integer not greater than N, and I _n Representing a load operating current, K, of an nth load branch of said N load branches _n Representing a dimming coefficient corresponding to the nth load branch;

the current adjusting module is used for adjusting the total current flowing through the N load branches according to the control signal so as to enable the voltages at two ends of the N load branches to be matched with the voltage of the voltage output end (V0).

As shown in fig. 1, in a specific structure of the multichannel synchronous dimming circuit, the topology of the voltage control module may be, but is not limited to, a buck, boost or buck-boost circuit structure, and specific forms include, but are not limited to, isolated, non-isolated, flyback or forward, etc. In order to dynamically adjust the output voltage in a feedback manner, the voltage control module preferably needs an output voltage adjustment feedback port FB, that is, the voltage control module can, but is not limited to, adopt a switching power supply including an inductive element circuit unit (denoted by HP in the drawings) and a switching control circuit unit, wherein the inductive element circuit unit includes, but is not limited to, an inductor and/or a transformer, etc., and a controlled terminal of the switching control circuit unit serves as the output voltage adjustment feedback port FB. The switching Power supply can be but not limited to adopt various existing buck, boost or buck-boost circuits which realize flyback/forward and are provided with the output voltage regulation feedback port FB, and no matter whether high PFC (Power Factor Correction) application or low PFC application, isolated application or non-isolated application is adopted, and whether the Power range is high Power or low Power, as long as the switching Power supply is provided with the output voltage regulation feedback port FB, the switching Power supply can be linked with a post-stage circuit (such as the current regulation module) to realize corresponding voltage control application. The input voltage is denoted by VIN in the figure and may be either an ac voltage or a dc voltage. The switch control circuit unit can be, but is not limited to, adopt an existing circuit structure based on a control chip, a switching tube, a driving circuit and the like to realize a function of dynamically adjusting the output voltage according to the feed-in signal. In addition, the voltage output end V0 of the voltage control module may be connected to the positive terminals of the N load branches respectively through a bus.

The load may specifically include various linear loads or non-linear loads that require constant current operation, such as Light-Emitting diodes (LEDs) and other Light-Emitting lamps. The switch tube (K1/K2/KN) is responsible for the on/off of the corresponding load branch, which may be, but not limited to, a transistor, a mosfet, an igbt, a thyristor, or the like. 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 purpose of independently dimming the corresponding load can be achieved through the corresponding switch tube based on the corresponding input PWM signal. The voltage across each load branch is the voltage difference between the voltage output terminal V0 and the negative terminal V1, the voltage across each load branch may vary from a few volts at low voltage to hundreds of volts at high voltage, the current flowing through the load may range from a few milliamperes to a few amperes, and the operating power of the load may range from a few watts to hundreds of watts. In addition, if the luminescent lamp is replaced by a battery, a heating wire, a pure resistor and the like, a multi-channel synchronous current regulation circuit can be obtained.

The current regulation module specifically includes, but is not limited to, a current stabilization circuit unit and a logic judgment unit which are integrated, wherein the current stabilization circuit unit is used for realizing load matching and leading out current flowing through the load to the ground, and the logic judgment unit is used for regulating the total current flowing through the N load branches according to the control signal, so that various protections required by dimming and load constant-current work can be considered. Since the negative terminal V1 is a node of voltage to ground, and the voltage value is the difference between the voltage at the voltage output terminal V0 and the voltages at the two ends of the N load branches, the matching between the current voltages at the two ends of the N load branches and the voltage at the voltage output terminal V0 can be directly reflected, for example, when the voltage at the voltage output terminal V0 is greater than the voltages at the two ends of the N load branches, the voltage at the negative terminal V1 is also greater, and when the voltage at the voltage output terminal V0 is equal to the voltages at the two ends of the N load branches, the voltage at the negative terminal V1 is approximately equal to 0V (when the voltages at the two ends of the N load branches are matched with the voltage at the voltage output terminal V0, that is, load matching is achieved). In addition, the control signal can be but is not limited to an analog signal, a digital signal or a PWM signal, and the current stabilizing circuit unit can be implemented by using an existing adjustable constant current circuit.

The dimming signal output module is used for generating PWM signals for executing corresponding dimming actions for each load branch circuit; for the purpose of remote 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, which is a protocol for data transmission and defines a communication mode between the electronic ballast and the device controller) communication technology. In addition, the power supply end of the dimming signal output module may be connected to an independent power supply VDD, or may be directly connected to the voltage output end V0; the ground terminal of the dimming signal output module may be independently grounded, or may be directly connected to the negative terminal V1, as shown in fig. 1.

The dimming signal coupling module is used for completely synchronizing the dimming actions of the N load branches with the dimming action of the current regulation module, that is, when any one or more load branches perform dimming actions (which are performed by inputting PWM signals for independent dimming at the controlled ends of the corresponding switching tubes), the input PWM signals of the load branches are fused into a single control signal by adopting a multi-channel dimming signal coupling technology and are sent to the current regulation module, so that the current regulation module performs on/off actions of output current in coordination with the dimming actions of any one or more load branches, and it is ensured that the associated actions at two places are high-speed response, delay-free and stagnation-free, specifically, when any PWM signal is effective, the output current is immediately turned on, otherwise, the output current is immediately turned off, and the on is immediately performed, the switch-off is immediately switched off, so that the current overshoot, the load abnormal protection and the standby power consumption have great effects.

The multi-channel dimming signal coupling technique may specifically be to perform an or gate logic processing on the PWM signals from the N PWM signal output terminals (i.e. to superimpose the PWM signals for independent dimming in a unit period time as shown in fig. 3 or 4, so as to become a new control signal, specifically, in a high-low level form, or continuously, in a PWM waveform). After receiving the control signal in the form of high and low levels or PWM waveform, the current regulation module may control the on and off of the constant current source by using the active level thereof, for example, for high level active application, when the control signal is high level, the constant current source starts to operate and outputs current, otherwise, the constant current source is turned off and no current is output; the action completely synchronizes the PWM signals of the N PWM signal output ends, the constant current is started when the signals exist, and the constant current is closed when the signals do not exist, so that unnecessary starting or misoperation can be well avoided; the precise up-down linkage effect is achieved, and particularly in the application of dimming and color mixing, the LED dimming lamp has an excellent dimming performance effect; and the application is very flexible, and two paths of CW dimming and color modulation, RGB dimming or CW + RGB dimming can be easily realized. Meanwhile, the cost of adding an additional channel (namely a load branch circuit) is limited to adding a switching tube instead of a whole circuit device, and the application of no inductor in a post-stage circuit does not generate a strong EMC problem like the inductor in the application of converting DC into DC, so that the volume and the cost control of the driving power supply have the remarkable advantages in practical application, namely any multiple channels can be easily realized with very low cost. In addition, the dimming coefficient is a multiple of the reduction of the load working current, and may also be called a dimming depth, and the value range is [0,1], and when the dimming coefficient is 0, the dimming state is the off state.

Preferably, when the voltage control module has an output voltage adjustment feedback port FB, the voltage control module further includes a signal sampling trimming module, a signal processing module and a feedback module, wherein a signal input end of the signal sampling trimming module is connected to the negative terminal V1, a signal output end of the signal sampling trimming module is connected to a signal input end of the signal processing module, a signal output end of the signal processing module is connected to a second signal input end of the feedback module, a communication end of the signal processing module is connected to the current regulation module, a first signal input end of the feedback module is connected to the voltage output end V0, and a signal output end of the feedback module is connected to the output voltage adjustment feedback port FB; the signal sampling trimming module is configured to perform trimming processing on the second sampling signal from the negative terminal V1, and send a trimmed signal obtained by the trimming processing to the signal processing module, where the trimming processing includes, but is not limited to, filtering processing, voltage division and voltage limitation processing, integration processing, and the like that are performed in sequence; the signal processing module is used for carrying out signal processing on the trimmed signal according to the control signal from the current regulating module to obtain a mixed signal of which the frequency component is in nonlinear negative correlation with the total load current after dimming, and sending the mixed signal to the feedback module; the feedback module is configured to feed the mixed signal and the first sampling signal from the voltage output terminal V0 into the output voltage adjustment feedback port FB in a superimposed manner, so that the voltage control module dynamically adjusts the output voltage according to the fed signal, and a difference between the output voltage of the voltage control module and the voltages at the two ends is always in a constant state preset by a circuit in the whole dimming process (i.e., the dimming depth is from 0% to 100%).

The signal sampling mode of the signal sampling trimming module is a direct sampling mode or an indirect sampling mode. The direct sampling mode includes, but is not limited to, a resistive voltage-dividing shunt sampling mode, a triode shunt sampling mode, an operational amplifier lossless sampling mode, an optical coupling isolation sampling mode, and/or a digital sampling mode based on an MCU (micro controller Unit) chip, and the like, and is applicable to a case where the voltage of the negative terminal V1 is high, so that even after voltage-dividing shunt processing, a high voltage component is still present to meet the requirement of subsequent finishing processing. The indirect sampling method is a sampling method for increasing voltage by using a voltage superposition processing technology, that is, considering that a voltage component of the voltage at the negative end V1 cannot meet the trimming processing of a circuit after direct sampling, a fixed voltage Vg needs to be superposed on the voltage at the negative end V1, and the voltage Vg can be set according to practical applications, and specifically, the voltage Vg can be obtained by combining the voltage at the voltage output end V0 with various circuits capable of realizing constant voltage output, such as a zener diode, a triode, a Low Dropout Regulator (LDO), and a linear Regulator (linear Regulator) Regulator, that is, as shown in fig. 2, a final output voltage signal Vx is equal to the sum of the voltage at the negative end V1 and the voltage Vg. Therefore, the voltage signal of the negative terminal V1 can be accurately acquired finally regardless of the direct sampling mode or the indirect sampling mode.

When the light is not modulated, the load works in a stable constant current state, namely, the voltages at two ends of the N load branches are also in a constant state, if the load of the LED lamp is used for detailed description, the LED lamp is constant current and has no stroboflash, so that the following steps can be deduced: when the whole circuit is stable, the voltage at the negative terminal V1 is also a relatively stable value, that is, the waveform condition should be the result of subtracting the voltages at the two ends of the N load branches from the ripple-shaped voltage at the voltage output terminal V0, wherein, for the item of single-stage high PFC, the ripple in the ripple-shaped voltage is the power frequency ripple, and if the two-stage topology or the low PFC structure is adopted, the ripple is the dc voltage. Meanwhile, in the dimming process, the voltage of the negative terminal V1 is superimposed with a high frequency component on the basis of the waveform of the dimming signal, the high frequency component is consistent with the PWM pulse frequency (generally, several KHz to several tens KHz) of the control signal, and at this time, the voltage of the negative terminal V1 is composed of three components: the ripple-shaped voltage of the voltage output terminal V0, the voltages at two ends of the N load branches and the high-frequency component; furthermore, as the dimming depth is different, the ripple in the ripple-shaped voltage varies, and the voltages across the N load branches are also affected by the ripple. In order to ensure the continuity and consistency of the ripple-shaped voltage at the voltage output end V0 and the voltages at the two ends of the N load branches under different dimming depths, a series of trimming processes are required to be performed on the sampled signal waveform, namely, a filtering process (i.e., removing an interference signal and a part of high-frequency components); secondly, voltage division and voltage limitation processing (namely, the voltage division is for the convenience of processing of the circuit, and the voltage limitation is for the purpose of dealing with the damage of the overhigh voltage of the negative terminal V1 to the circuit, such as the voltage of the negative terminal V1 becomes very high when the load is abnormal); and finally, integrating (namely removing the influence of power frequency ripples).

Considering that the voltage signal at the negative terminal V1 becomes extremely complex and variable during dimming and is directly related to the control signal, in order to make the voltages at the two terminals of the N load branches exactly match the voltage at the voltage output terminal V0, it is necessary to perform a partial frequency component attenuation process on the current trimmed signal according to the control signal, so as to ensure that the mixed signal to the feedback module is not distorted or overshot, i.e., the trimmed signal is signal-processed according to the control signal from the current regulation module, so as to obtain a mixed signal whose frequency component is nonlinearly inversely related to the total current magnitude of the load after dimming, including but not limited to: and according to the control signal from the current regulation module, carrying out attenuation processing on part of frequency components in the trimmed signal, wherein the attenuation processing is in nonlinear negative correlation with the total load current after dimming, so as to obtain a mixed signal, the frequency components of which are in nonlinear negative correlation with the total load current after dimming, and when the total load current after dimming is in a complete dimming state, carrying out complete attenuation processing on all frequency components in the trimmed signal, so that no signal is output to the feedback module. In another specific embodiment, the feeding the mixed signal to the feedback module includes, but is not limited to: after the mixed signal is subjected to at least one integration processing, the mixed signal is amplified (i.e. the signal obtained by the integration processing is subjected to the signal amplification processing again) and then is sent to the feedback module, wherein the at least one integration processing is performed to ensure the integrity and the dynamic property of the mixed signal, and meanwhile, the signal distortion and the overshoot can be prevented, which is a key point of the stability of the whole circuit. In addition, before the signal processing module performs signal processing on the trimmed signal, the signal processing module may also perform current limiting and integration processing on the trimmed signal, that is, due to complexity of the voltage and current of the negative end V1 in terms of variation amplitude and waveform, interference noise and abnormal waveform need to be further thoroughly eliminated, so as to prepare for subsequent signal processing.

In summary, the working processes of the signal sampling trimming module, the signal processing module and the feedback module include, but are not limited to, the following two logic:

(A) the voltage of the voltage output end V0 and the voltages at the two ends of the N load branches are matched, that is, the logic is established on the basis of non-dimming, the operation path is to sample the voltage signal of the negative end V1 and complete the corresponding trimming and other processing, so as to obtain a positive correlated and amplified mixed signal, it is understood from the above that when the voltage of the negative end V1 becomes large, it means that the voltages at the two ends of the N load branches become small, and if no adjustment is performed, the power consumption generated by multiplying the voltage of the negative end V1 by the current is dissipated by the current adjusting module, so that the temperature of the current adjusting module rises and even is burned out; at this time, the feedback module superimposes the mixed signal and the first sampling signal from the voltage output end V0 to feed into the output voltage adjustment feedback port FB, and the voltage control module can be used to reduce the voltage of the voltage output end V0, so that the voltage of the negative electrode end V1 can be correspondingly reduced to a preset value, otherwise, the voltage of the voltage output end V0 is increased to increase the voltage of the negative electrode end V1, so that the current adjustment module can work normally and cannot enter a non-constant current state, so that the current adjustment module can be dynamically and continuously in an optimal working state all the time, and the stability and good working efficiency of the whole voltage control functional circuit are ensured;

(B) the logic for dynamically adjusting the voltage at the voltage output V0 during dimming is to add dimming states on a non-dimming basis, although only dimming states are added, the complexity of the whole circuit is increased a lot, and here we can describe two states, the first is dimming state, the second is full dimming state (even if all loads are dimmed), and full dimming is the extreme case of dimming, and then the effect of this full dimming state on the whole circuit is extreme. In a dimming state, because the voltage waveform of the negative terminal V1 overlaps a high-frequency ripple, the high-frequency ripple can be regarded as a high-frequency square wave overlapping a low-frequency ripple after being subjected to sampling trimming processing, and the amplitude of the waveform is correspondingly increased under the condition that the load total current/dimming brightness after dimming is lower and lower, so that after being subjected to sampling trimming processing, a signal tends to rise along with the load total current after dimming, and finally the voltage of the voltage output terminal V0 is reduced along with the load total current after dimming, which has an obvious adverse effect on the dimming effect, at this time, a second sampling signal from the negative terminal V1 needs to be subjected to signal processing according to the control signal, so as to obtain a mixed signal of which the frequency component (i.e. the vibration amplitude of the frequency point signal) is in nonlinear negative correlation with the load total current after dimming, in order to counteract a part of the effect of the rising trend; and as the total current is smaller after dimming, the more frequency components of the mixed signal are drawn by the low level, so that the mixed signal is kept unchanged or in a descending trend (here, the adjustment can be realized only by setting a proper attenuation parameter), and finally, the voltage of the voltage output end V0 is kept unchanged or in an ascending trend, so that the dimming effect is fully ensured. In the complete dimming state, since the total load current is zero after dimming, the frequency component extracted from the mixed signal is the largest, and in order to ensure that the frequency component extracted from the mixed signal can be set arbitrarily, a corresponding circuit needs to be added to make a logic judgment, so that it can be ensured that the signal given to the feedback module is lower than a threshold value in the complete dimming state, that is, the feedback module only receives the first sampling signal from the voltage output end V0, so that the voltage control module outputs the highest voltage and the no-load voltage. In addition, if the total current is increased from 0 after dimming, the logic processing procedure is contrary to the foregoing description, and is not described herein again; and in the whole dimming process, the specific representation that the difference value between the output voltage of the voltage control module and the voltages at the two ends is always in a constant state preset by a circuit is as follows: in the whole dimming process, the output voltage of the voltage control module is stable and has no fluctuation (i.e. including stable rising, stable falling and stable maintaining), the output current of the current regulation module is stable and has no fluctuation (i.e. including stable rising, stable falling and stable maintaining), and the current regulation module is in a high-efficiency working state (i.e. the negative terminal V1 is always in a low-voltage state, the internal dissipated power is low, and thus the high-efficiency working is possible).

Preferably, the signal processing module is further configured to trigger sending of an alarm signal to the current adjusting module when the second sampling signal or the mixed signal is found to be abnormal, so that the current adjusting module adjusts the total current flowing through the N load branches to zero when receiving the alarm signal, and the purpose of protecting the load by turning off the current is achieved. As shown in fig. 1, the current shutdown operation may be performed by the logic determining unit, for example, when the voltages at the two ends of the N load branches are found to be smaller than a preset value or even 0 (i.e., short circuit), the load abnormal protection purpose may be achieved through the current shutdown operation.

To sum up, the multi-channel synchronous dimming circuit provided by the embodiment has the following technical effects:

(1) the embodiment provides a load driving scheme for performing multi-channel synchronous dimming based on a dimming signal coupling technology, which includes a voltage control module, a plurality of load branches, a current adjustment module, a dimming signal output module and a dimming signal coupling module, where the load branches include a load and a switching tube electrically connected in series, the dimming signal output module is configured to input a PWM signal for performing independent dimming on a corresponding load to each load branch in the plurality of load branches, the dimming signal coupling module is configured to couple a plurality of PWM signals into a control signal for performing total dimming on the plurality of load branches and output the control signal, the current adjustment module is configured to implement load matching and adjust a total current flowing through the plurality of load branches according to the control signal, so that under the condition that output power is not changed, the purpose of single-channel and any multi-channel dimming without mutual influence is achieved, the cost of adding an additional channel is limited to adding one switching tube instead of a whole circuit device, and the additional channel is applied in a post-stage circuit without inductance, so that the problem of strong EMC caused by inductance in DC-to-DC application is solved, and therefore, the volume and cost control of the driving power supply has the remarkable advantages in practical application, and the practical application and popularization are facilitated;

(2) through the configuration of the signal sampling trimming module, the signal processing module and the feedback module, the difference value between the output voltage of the voltage control module and the voltage at two ends of the load is always in a constant state preset by the circuit in the whole dimming process, so that the purposes that the output voltage of a front-stage circuit and the output current of a rear-stage circuit are stable and free of fluctuation, and meanwhile, the rear-stage circuit is always in a high-efficiency working state are achieved, and the dimming performance is effectively improved;

(3) the current of each channel can be independently and accurately controlled and adjusted through PWM, and high-precision color temperature/color difference control is realized;

(4) because the circuit has no electrolytic capacitor and no inductance at the rear stage, the circuit can be conveniently made into an integrated circuit and modularized, and the driving application of ultra-small volume, low cost and high power is realized;

(5) because the circuit has no inductance, the circuit has great help to drive the EMC problem, not only reduces the EMC cost of the whole machine, but also accelerates the design of the scheme and the stability and the anti-interference performance of the drive;

(6) because the rear-stage current regulation action is synchronous with the high level of the dimming signal, and when any dimming signal is at the high level, the rear stage outputs current, otherwise, the rear stage does not output current, the current can be supplied at any time, and further good dimming performance and effective protection function are realized;

(7) the load protection circuit has the advantages of multiple channels, accurate control, light dimming and constant current synchronism, and the function of load abnormity protection of any channel is realized.

Finally, it should be noted that the present invention is not limited to the above alternative embodiments, and that any person can obtain other products in various forms in the light of the present invention. The above detailed description should not be taken as limiting the scope of the invention, which is defined in the claims, and which the description is intended to be interpreted accordingly.

Claims (10)

1. A multi-channel synchronous dimming circuit is characterized by comprising 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 branches comprise a load and a switching tube which are 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 for converting the input voltage into direct current voltage and outputting the direct current voltage;

the positive ends of the N load branches are respectively connected with a voltage output end (V0) of the voltage control module, the negative ends (V1) of the N load branches are respectively connected with 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 respectively connected with the controlled ends of the switch tubes in the N load branches in a one-to-one correspondence manner, the N PWM signal output ends are also respectively connected with the N signal input ends of the dimming signal coupling module in a one-to-one correspondence manner, and the signal output end of the dimming signal coupling module is connected with the dimming signal input end of the current adjusting module;

the dimming signal output module is configured to input a PWM signal for independently dimming a corresponding load to each load branch of the N load branches;

the dimming signal coupling module is configured to couple the PWM signals from the N PWM signal output ends into a control signal for performing total dimming on the N load branches, and output the control signal, where a total dimming coefficient K of the control signal satisfies:

K＝(K ₁ *I ₁ +K ₂ *I ₂ +…+K _n *I _n +…+K _N *I _N )/I

wherein I represents the total current flowing through the N load branches, N represents a positive integer not greater than N, and I _n Representing a load operating current, K, of an nth load branch of said N load branches _n Representing a dimming coefficient corresponding to the nth load branch;

the current adjusting module is used for adjusting the total current flowing through the N load branches according to the control signal so as to enable the voltages at two ends of the N load branches to be matched with the voltage of the voltage output end (V0).

2. The multi-channel synchronous dimming circuit of claim 1, further comprising a signal sampling trimming module, a signal processing module and a feedback module when the voltage control module has an output voltage regulation feedback port (FB), wherein a signal input terminal of the signal sampling trimming module is connected to the negative terminal (V1), a signal output terminal of the signal sampling trimming module is connected to the signal input terminal of the signal processing module, a signal output terminal of the signal processing module is connected to the second signal input terminal of the feedback module, a communication terminal of the signal processing module is connected to the current regulation module, a first signal input terminal of the feedback module is connected to the voltage output terminal (V0), and a signal output terminal of the feedback module is connected to the output voltage regulation feedback port (FB);

the signal sampling trimming module is used for trimming a second sampling signal from the negative electrode end (V1) and sending the trimmed signal obtained by processing to the signal processing module, wherein the trimming processing comprises filtering processing, voltage division and voltage limitation processing and integration processing which are sequentially carried out;

the signal processing module is used for carrying out signal processing on the trimmed signal according to the control signal from the current regulating module to obtain a mixed signal of which the frequency component is in nonlinear negative correlation with the total load current after dimming, and sending the mixed signal to the feedback module;

the feedback module is configured to feed the mixed signal and a first sampling signal from the voltage output end (V0) into the output voltage adjustment feedback port (FB) in a superimposed manner, so that the voltage control module dynamically adjusts the output voltage according to the fed signal, and the difference between the output voltage of the voltage control module and the voltages at the two ends is always in a constant state preset by a circuit in the whole dimming process.

3. The multi-channel synchronous dimming circuit according to claim 2, wherein the signal processing module is further configured to trigger 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 regulates 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 turning off the current.

4. The multi-channel synchronous dimming circuit of claim 2, wherein the trimmed signal is signal-processed according to the control signal from the current regulation module to obtain a mixed signal with a frequency component having a non-linear negative correlation with the total current of the load after dimming, comprising:

and according to the control signal from the current regulation module, carrying out attenuation processing on part of frequency components in the trimmed signal, wherein the attenuation processing is in nonlinear negative correlation with the total load current after dimming, so as to obtain a mixed signal, the frequency components of which are in nonlinear negative correlation with the total load current after dimming, and when the total load current after dimming is in a complete dimming state, carrying out complete attenuation processing on all frequency components in the trimmed signal, so that no signal is output to the feedback module.

5. The multi-channel synchronous dimming circuit of claim 2, wherein feeding the mixed signal into the feedback module comprises:

and after the mixed signal is subjected to at least one-time integration processing, the mixed signal is amplified and sent to the feedback module.

6. The multi-channel synchronous dimming circuit according to claim 2, wherein the signal sampling mode of the signal sampling trimming module is a direct sampling mode or an indirect sampling mode, wherein the direct sampling mode includes a resistance voltage division shunt sampling mode, a triode shunt sampling mode, an operational amplifier lossless sampling mode, an optical coupling isolation sampling mode and/or a digital sampling mode based on an MCU chip, and the indirect sampling mode is a sampling mode for boosting voltage by a voltage superposition processing technology.

7. The multi-channel synchronous dimming circuit of claim 1, wherein the voltage control module employs a switching power supply comprising an inductive element circuit unit and a switching control circuit unit, wherein the inductive element circuit unit comprises an inductor and/or a transformer, and a controlled terminal of the switching control circuit unit is used as an output voltage regulation feedback port (FB).

8. The multi-channel synchronous dimming circuit of claim 1, wherein the current regulation module comprises a current stabilization circuit unit and a logic judgment unit, wherein the current stabilization circuit unit and the logic judgment unit are integrated, the current stabilization circuit unit is configured to draw a current flowing through the load to ground, and the logic judgment unit is configured to regulate a total current flowing through the N load branches according to the control signal.

9. The multi-channel synchronous dimming circuit of claim 1, wherein the dimming signal output module employs a wireless remote control circuit based on 2.4Ghz wireless technology, WiFi wireless technology, bluetooth wireless technology, and/or DALI wireless technology.

10. The multi-channel synchronous dimming circuit of claim 1, wherein the switch transistor is a triode transistor, a metal oxide semiconductor field effect transistor, an insulated gate bipolar transistor or a silicon controlled thyristor.

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