CN113873718B - Dimming control device - Google Patents
Dimming control device Download PDFInfo
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- CN113873718B CN113873718B CN202111211510.XA CN202111211510A CN113873718B CN 113873718 B CN113873718 B CN 113873718B CN 202111211510 A CN202111211510 A CN 202111211510A CN 113873718 B CN113873718 B CN 113873718B
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- 238000003079 width control Methods 0.000 claims abstract description 118
- 238000004146 energy storage Methods 0.000 claims abstract description 45
- 239000003990 capacitor Substances 0.000 claims abstract description 43
- 230000011664 signaling Effects 0.000 claims abstract description 4
- 238000000034 method Methods 0.000 abstract description 7
- 230000008569 process Effects 0.000 abstract description 7
- 230000010355 oscillation Effects 0.000 abstract description 3
- 239000011324 bead Substances 0.000 description 9
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- 230000009471 action Effects 0.000 description 8
- 238000001514 detection method Methods 0.000 description 6
- 230000008859 change Effects 0.000 description 5
- 238000010586 diagram Methods 0.000 description 3
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- 238000005516 engineering process Methods 0.000 description 2
- 238000005286 illumination Methods 0.000 description 2
- 230000010349 pulsation Effects 0.000 description 2
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- 238000006467 substitution reaction Methods 0.000 description 2
- 230000033228 biological regulation Effects 0.000 description 1
- 238000005282 brightening Methods 0.000 description 1
- 239000003985 ceramic capacitor Substances 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
- H05B45/32—Pulse-control circuits
- H05B45/325—Pulse-width modulation [PWM]
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/10—Controlling the intensity of the light
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
- Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
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Abstract
The invention provides a dimming control device, wherein the device comprises: the pulse width control circuit comprises a light emitting circuit, a pulse width control circuit and an energy supply circuit, wherein the light emitting circuit comprises a light emitting part; the light-emitting part comprises a light source, an energy storage capacitor and a load resistor; the pulse width control circuit is used for accessing a pulse width control signal and controlling whether the energy supply circuit supplies power to the light-emitting circuit in a constant current manner; the power supply circuit can supply power to the light emitting part. According to the dimming control device provided by the embodiment of the invention, a constant-current power supply mode is adopted, and the brightness of the light source can be further reduced through the energy storage capacitor and the load resistor which are mutually matched in parallel at the two ends of the light source, and particularly, under the lowest dimming scale, light rays with lower brightness can be provided; in addition, in the process of starting and stopping power supply of the power supply circuit, voltage ripples and oscillations required to be born by the light source can be absorbed, power supply impact received by the light source can be effectively protected and reduced, flickering of the light source is eliminated, and the light source can stably maintain lower brightness.
Description
Technical Field
The invention relates to the technical field of dimming control, in particular to a dimming control device.
Background
The LED light source is a light source based on a light emitting diode and has the advantages of low energy consumption, short response time, multicolor light emission and the like. With the continuous development of LED technology, LED light sources are widely used, and scenes such as markets and houses can use a large number of lamps using the LED light sources as illumination or decoration, and adjust the brightness of the LED light sources as needed so as to provide comfortable illumination.
At present, many LED light sources can use PWM (Pulse Width Modulation ) technology to adjust the brightness of the light, and in general, the PWM controller can adjust the dimming scale by adjusting the duty ratio, so as to adjust the brightness of the LED light source, and different dimming scales correspond to different brightnesses. In order to meet various demands of users, a plurality of dimming scales need to be set for an LED light source, even 'electrodeless dimming' is realized, currently, the precision or the brightness range of the dimming scales of the brightness of the light source is mainly improved by improving the control effect of PWM, the scheme has higher cost, and the dimming effect under the condition of low brightness is general.
In addition, the LED light source needs to bear ripple waves generated in the circuit in the dimming process, the dimming process is not smooth, the dithering phenomenon is easy to occur, smooth dimming and low-brightness constant current control cannot be really realized, and the dimming stability is poor.
Disclosure of Invention
In order to solve the existing technical problems, an embodiment of the present invention provides a dimming control device, including: the light-emitting device comprises a light-emitting circuit, a pulse width control circuit and an energy supply circuit, wherein the light-emitting circuit comprises a light-emitting part; the light-emitting part comprises a light source, an energy storage capacitor and a load resistor, wherein the energy storage capacitor and the load resistor are connected with the light source in parallel; the pulse width control circuit is used for accessing a pulse width control signal and controlling whether the energy supply circuit supplies power to the light-emitting circuit in a constant current manner according to the pulse width control signal; when the power supply circuit is capable of supplying power to the light emitting circuit, the power supply circuit is capable of supplying power to the light emitting section.
Optionally, the light emitting circuit further comprises an inductor and a freewheeling diode; the inductor is connected in series with the light emitting part, and the flywheel diode is connected in parallel with the inductor and the light emitting part which are connected in series.
Optionally, an enabling end of the pulse width control circuit is used for accessing the pulse width control signal, and an input end of the pulse width control circuit is connected with an output end of the energy supply circuit; the output end of the energy supply circuit is also connected with one end of the light-emitting circuit, and the other end of the light-emitting circuit is connected with the control end of the pulse width control circuit; the control end of the pulse width control circuit is used for controlling whether the other end of the light-emitting circuit is grounded or not according to the pulse width control signal.
Optionally, when the pulse width control signal is at a high level, the other end of the light emitting circuit is grounded through a control terminal of the pulse width control circuit; when the pulse width control signal is at a low level, the other end of the light emitting circuit is not grounded.
Optionally, the pulse width control circuit further comprises a current detection resistor, wherein the current detection resistor is used for detecting the average current of the light emitting circuit.
Optionally, the resistance value of the load resistor is not less than a preset threshold, where the preset threshold is:
wherein V is in Representing the voltage value output by the energy supply circuit, I min Represents a minimum current value, min (I LED ) Current I representing the light source capable of emitting light LED Is a minimum of (2).
Optionally, the number of the light emitting circuits and the pulse width control circuits is the same and is a plurality of, and the plurality of the light emitting circuits and the plurality of the pulse width control circuits share the same energy supply circuit; each pulse width control circuit is used for controlling whether the energy supply circuit supplies power to the corresponding light-emitting circuit in a constant current mode.
Optionally, the light source comprises a plurality of LEDs connected in series, a plurality of LEDs connected in parallel, or a group of LEDs collectively formed by a plurality of series and parallel modes.
Optionally, the frequency of the pulse width control signal is not less than 1000Hz.
According to the dimming control device provided by the embodiment of the invention, a constant-current power supply mode is adopted, and the brightness of the light source can be further reduced through the energy storage capacitor and the load resistor which are mutually matched in parallel at the two ends of the light source, and particularly, under the lowest dimming scale, light rays with lower brightness can be provided; in addition, in the process of starting and stopping power supply of the power supply circuit, voltage ripples and oscillations required to be born by the light source can be absorbed, power supply impact received by the light source can be effectively protected and reduced, flickering of the light source is eliminated, and the light source can stably maintain lower brightness.
Drawings
In order to more clearly describe the embodiments of the present invention or the technical solutions in the background art, the following description will describe the drawings that are required to be used in the embodiments of the present invention or the background art.
Fig. 1 shows a circuit diagram of a dimming control device according to an embodiment of the present invention;
fig. 2 shows a detailed circuit diagram of the dimming control device according to an embodiment of the present invention.
Reference numerals:
10-light-emitting circuit, 11-light-emitting part, 20-pulse width control circuit, 21-enable terminal, 22-input terminal, 23-control terminal, 30-energy supply circuit;
LED 1 -LED n -a light source, R1-load resistor, R2-current sensing resistor, E1-energy storage capacitor, L1-inductance, D1-freewheeling diode.
Detailed Description
The inventors have found that the minimum brightness of the current LED light source still has a certain limitation, for example, when the current dimming scale is minimum (for example, the LED light source can be on under the current dimming scale, but one dimming scale is lowered, the LED light source is turned off), the LED light source cannot continuously adjust the brightness to be lower before the power is turned off, and the brightness corresponding to the current dimming scale can only be changed to be turned off directly when the dimming scale is lower, so that the lower brightness cannot be displayed, and the "minimum brightness" achieved by the LED light source is still brighter for some users.
In carrying out the inventive process, the inventors have found that this problem is caused by: when the current dimming scale is minimum, the voltages at the two ends of the LED light source are basically consistent with the conducting voltage thereof, if the dimming scale is reduced, the voltages at the two ends of the LED light source are smaller than the conducting voltage, so that the LED light source is extinguished, but the current flowing through the LED light source at the moment is not necessarily the minimum current capable of enabling the LED light source to emit light. The embodiment of the invention provides a dimming control device, which reduces the current of an LED light source so as to further reduce the brightness of the LED light source.
Embodiments of the present invention will be described below with reference to the accompanying drawings in the embodiments of the present invention.
Fig. 1 shows a schematic structural diagram of a dimming control device according to an embodiment of the present invention. As shown in fig. 1, the apparatus includes: a light-emitting circuit 10, a pulse width control circuit 20, and an energizing circuit 30, the light-emitting circuit 10 including a light-emitting portion 11; the light-emitting part 11 comprises a light source, an energy storage capacitor E1 and a load resistor R1, wherein the energy storage capacitor E1 and the load resistor R1 are connected with the light source in parallel; the pulse width control circuit 20 is used for switching in a pulse width control signal and controlling whether the energy supply circuit 30 supplies constant current to the light emitting circuit 10 according to the pulse width control signal; when the power supply circuit 30 can supply power to the light emitting circuit 10, the power supply circuit 30 can supply power to the light emitting section 11.
In an embodiment of the present invention, the dimming control device may include the following parts: a light emitting circuit 10 for realizing a light emitting function, a pulse width control circuit 20 for switching in a pulse width control signal, and an energizing circuit 30 for supplying power to the light emitting circuit 10. The power supply circuit 30 may be a circuit having a power supply, and may supply power to the light emitting circuit 10 based on the power supply; alternatively, the power supply circuit 30 may be a circuit to which a power supply is connected, and the power supply circuit 30 may be connected to an external power supply to supply power to the light emitting circuit 10 from the external power supply, for example, the power supply circuit 30 may be a power supply interface or the like. The pulse width control circuit 20 can control whether the power supply circuit 30 and the light emitting circuit 10 can form a loop based on the high and low level in the pulse width control signal, so that it is possible to control whether the power supply circuit 30 supplies power to the light emitting circuit 10, for example, whether the power supply circuit 30 supplies power to the light emitting section 11 of the light emitting circuit 10. For example, when the pulse width control signal is at a high level, the power supply circuit 30 can supply power to the light emitting portion 11 of the light emitting circuit 10; when the pulse width control signal is at a low level, the power supply circuit 30 does not supply power to the light emitting section 11 of the light emitting circuit 10.
In addition, in general, the LED light source operates in a constant current mode to ensure that the LED light source can emit light stably, so that the light emitting circuit 10 operates in a constant current mode. The power supply circuit 30 may be a constant voltage source, and the pulse width control circuit 20 has a capability of controlling a constant current output to the light emitting circuit 10, and under the combined action of the power supply circuit 30 and the pulse width control circuit 20, the constant current may be provided to the light emitting circuit 10, that is, the light emitting circuit 10 receives stable power supply. The pulse width control circuit 20 controls whether the power supply circuit 30 is turned on or not to the light emitting circuit 10, thereby causing the power supply circuit 30 to supply power to the light emitting circuit 10 and causing the light emitting circuit 10 to be in a constant current state under the control of the pulse width control circuit 20. Alternatively, in the case where the power supply circuit 30 is not a constant voltage source, the pulse width control circuit 20 may adjust the magnitude of the current flowing through the light emitting circuit 10 to realize a constant current, that is, the light emitting circuit 10 may be placed in a constant current state by the cooperation of the pulse width control circuit 20 and the power supply circuit 30. In either case, the power supply circuit 30 can supply power to the light emitting circuit 10, and the light emitting circuit 10 can operate in a constant current manner under the control of the pulse width control circuit 20.
The light emitting unit 11 of the light emitting circuit 10 may include, in addition to the light source, an energy storage capacitor E1 and a load resistor R1 connected in parallel with the light source, respectively. The light source may be an LED (light emitting diode, LED bead) light emitting diode. Optionally, the light source comprises a plurality of LEDs connected in series. As shown in fig. 1, the light source is an LED 1 -LED n The light source can be a string of LED lamp beads consisting of a plurality of LEDs connected in series, or can be a group of LED lamp beads formed by a plurality of strings of LED lamp beads connected in parallel.
In the embodiment of the invention, the load resistor R1 in the light-emitting part 11 is connected in parallel with the light source, and when the energy supply circuit 30 supplies power to the light-emitting part 11, the parallel load resistor R1 and the light source can be supplied with power, so that the light source can emit light; further, since the constant current is supplied to the light emitting portion 11 by the power supply circuit 30, the magnitude of the current flowing through the light source can be reduced by the shunt action of the load resistor R1, thereby reducing the light emission luminance of the light source. For example, when the current dimming scale is minimum, if the load resistor R1 is not present, the light source emits light under the action of the smaller current value a; in the embodiment of the invention, the current value of the current flowing through the light source is smaller than the current value a due to the shunt effect of the load resistor R1, that is, the light source can emit light with smaller current, so that the light-emitting brightness of the light source can be further reduced. Therefore, the dimming control device can provide lower-brightness light for a user, and is convenient for the user to use in a scene requiring low-brightness light.
For example, the light source is set as an LED 1 -LED n N is a positive integer, and the resistance value of the load resistor R1 is R 1 The input voltage provided by the power supply circuit 30 is Vin, the maximum current divided by the load resistor R1 is I, and i=vin/R 1 . Because the load resistor R1 is connected in parallel with the LED 1 -LED n The load resistor R1 divides all the light which should flow through the LED 1 -LED n Upper current, thus, when dimming to the lowest dimming level, the LED 1 -LED n The current value flowing through the load resistor R1 is equal to the current value originally flowing through the load resistor R1 at the lowest dimming scale. Therefore, when dimming to the lowest dimming scale, the LED 1 -LED n The current value flowing through the LED is reduced compared with the current value which is not connected in parallel with the load resistor R1 before 1 -LED n Can also maintain a lower brightness of the LED at the lowest dimming level before the load resistor R1 is turned off and connected in parallel 1 -LED n The brightness maintained.
In general, when the power supply circuit 30 supplies power to the light emitting circuit 10 initially (for example, on) or stops supplying power finally (for example, off), the voltage flowing to the light source will ripple, and the voltage on the light source is not stable, so that the light source will flicker. According to the embodiment of the invention, the energy storage capacitor E1 is also connected in parallel at the two ends of the light source, and the energy storage and filtering effects of the energy storage capacitor E1 are utilized to reduce or even eliminate the ripple generated during initial power supply or final power supply stop, prevent current mutation and ensure that the light source can work stably.
Optionally, the capacitance value of the energy storage capacitor E1 may be determined according to a combination of actual requirements and experience. If the capacitance value of the energy storage capacitor E1 is too small, the energy storage and filtering effects cannot be achieved; however, if the capacitance value of the energy storage capacitor E1 is too large, the longer the charge and discharge time of the energy storage capacitor E1 is, the longer the feedback time of the light source is, which is contrary to the actual requirement of the present dimming control device for fast response to realize dimming, and the effect is poor in practical application. Therefore, the embodiment of the invention can lead the capacitance value of the energy storage capacitor E1 to be a relatively proper value, not only can meet the stable filtering of the voltage input to the light source, but also can lead the light source to be more sensitive to light regulation and control, and realize quick feedback.
The energy storage capacitor E1 may be an electrolytic capacitor, a solid capacitor, a ceramic capacitor, or the like, and the energy storage capacitor E1 has the characteristics of low ripple, low internal resistance, and capability of effectively storing electric quantity. In a power supply period of the pulse width control signal, the power supply circuit 30 includes supplying power to the light emitting circuit 10 and thereafter stopping supplying power to the light emitting circuit 10, and the energy storage capacitor E1 is charged at the start of the power supply period and discharged at the end of the power supply period. If the charge of the energy storage capacitor E1 is higher than the discharge charge thereof, the voltage of the energy storage capacitor E1 increases, which results in a decrease in the charge of the energy storage capacitor E1 and an increase in the discharge charge in each power supply period, so that the increasing speed of the voltage of the energy storage capacitor E1 is slowed down until the charge-discharge balance is reached, i.e. the charge quantity is the same as the discharge quantity, so that the voltage of the light emitting circuit 10 remains unchanged at this time, and the voltage of the energy storage capacitor E1 in the light emitting circuit 10 can be stabilized. According to the embodiment of the invention, when the energy supply circuit 30 stops supplying power to the light-emitting circuit 10 and dimming with low brightness is performed, the electric quantity released by the energy storage capacitor E1 can stably reduce the current in the light source, and the light source is prevented from flickering while the light source is kept to be luminous, so that the dimming stability and dimming experience are improved.
The working process of the dimming control device is specifically as follows:
under the action of the pulse width control signal, when the pulse width control circuit 20 controls the energy supply circuit 30 to supply power to the light emitting circuit 10 for the first time, for example, when the power is turned on, the energy supply circuit 30 supplies power to the light source, so that the light source emits light; the energy supply circuit 30 also charges the energy storage capacitor E1. At this time, under the action of the energy storage capacitor E1, the abrupt change of the current of the light source can be avoided, and the abrupt brightening of the light source is avoided. Thereafter, the power supply circuit 30 periodically supplies power to the light emitting circuit 10 in each power supply period of the pulse width control signal. Specifically, in a power supply period, if the pulse width control circuit 20 controls the energy supply circuit 30 to supply power to the light emitting circuit 10, the light source emits light under the action of the energy supply circuit 30, the energy supply circuit 30 charges the energy storage capacitor E1, and the load resistor R1 has a shunt effect, so that the light emitting brightness of the light source can be reduced to a certain extent; if the pulse width control circuit 20 controls the energy supply circuit 30 not to supply power to the light emitting circuit 10, the energy storage capacitor E1 and the light source connected in parallel form a loop, the energy storage capacitor E1 can discharge to the light source, and the light emitting duration of the light source is prolonged; in addition, when the pulse width control circuit 20 controls the power supply circuit 30 to stop supplying power to the light emitting circuit 10, the load resistor R1 can rapidly consume the energy released from the energy storage capacitor E1, and can eliminate static electricity on the light source. When the pulse width control circuit 20 controls the power supply circuit 30 not to supply power to the light emitting circuit 10 for the last time, for example, when the power supply circuit is turned off, the energy storage capacitor E1 discharges to the light source, and at this time, abrupt current change of the light source can be avoided, and abrupt dimming of the light source can be avoided.
According to the dimming control device provided by the embodiment of the invention, based on the combined action of the pulse width control circuit 20 and the energy supply circuit 30, the light-emitting circuit 10 is in a constant current state, and the brightness of a light source can be further reduced through connecting the energy storage capacitor E1 and the load resistor R1 which are mutually matched in parallel at the two ends of the light source, and particularly, under the lowest dimming scale, light rays with lower brightness can be provided; in addition, in the process of starting and stopping power supply of the power supply circuit 30, voltage ripples and oscillations required to be born by the light source can be absorbed, power supply impact received by the light source can be effectively protected and reduced, flicker of the light source is eliminated, and the light source can stably maintain lower brightness.
Optionally, referring to fig. 2, the light emitting circuit 10 further includes an inductance L1 and a flywheel diode D1; the inductor L1 is connected in series with the light emitting part 11, and the freewheeling diode D1 is connected in parallel with the inductor L1 and the light emitting part 11 which are connected in series, that is, after the inductor L1 is connected in series with the light emitting part 11, the serial structure formed by the inductor L1 and the light emitting part is connected in series with the freewheeling diode D1 in parallel.
In the embodiment of the invention, the inductor L1 has the characteristics of voltage reduction and energy storage, and the energy storage cannot be suddenly changed. When the operating frequency (fs) of the pulse width control signal for controlling the constant current power supply of the power supply circuit 30 to the light emitting circuit 10 is higher, the inductance value (L 1 ) The smaller the voltage ripple value (deltau) across the light source o ) The smaller. For example, the power supply circuit 30 provides an input voltage of V in Input to the light source LED 1 -LED n Is V at two ends of voltage o Voltage V of the inductor L1 can be reduced 1 ＝V in -V o The pulse width control circuit 20 has a pulse width control signal duty ratio d=v o /V in Therefore, it can be based on the formula L 1 ＝V in *D(1-D)/(2*k*fs*I max ) Determining the inductance value L of the inductance L1 1 Is of a size of (a) and (b). Wherein k is a correction coefficient, generally 0.05-0.1, I max LED for setting light source 1 -LED n Maximum current value flowing. From the calculation formula of the inductance L1, the inductance L of the inductance L1 can be seen 1 Inversely proportional to the operating frequency fs of the pulse width control signal.
In general, when the power supply circuit 30 supplies power to the light emitting circuit 10 initially (for example, power on) or stops supplying power finally (for example, power off), the inductance L1 causes a very large change in the current in the light emitting circuit 10, so that the current change impact born by the light source is very large, and a stroboscopic effect visible to the naked eye and a howling noise audible to the human ear are easy to occur. According to the embodiment of the invention, the energy storage capacitor E1 is connected in parallel at the two ends of the light source, so that the problems can be effectively avoided. The capacitance value of the energy storage capacitor E1 may be determined according to the voltage pulsation value at two ends of the light source, and the present embodiment may be based on the following empirical formula: c (C) o ＝I max *I max *L 1 /(V o *ΔU o ) Determining the capacitance C of the energy storage capacitor E1 o . Wherein, the light source is set as an LED 1 -LED n N is a positive integer, and is input to the LED 1 -LED n The voltage at two ends of the lamp bead string is V o And the LED 1 -LED n The voltage pulsation value at two ends of the lamp bead string is delta U o 。
Therefore, in the embodiment of the invention, the energy storage capacitor E1 connected in parallel at two ends of the light source can effectively store energy to protect the light source from power supply impact when the energy supply circuit 30 starts to supply power to the light emitting circuit 10, and can timely consume the energy stored in the inductor L1 when the energy supply circuit 30 stops supplying power to the light emitting circuit 10, so that the energy stored in the inductor L1 is prevented from being directly released to the light source to impact the light source, and the energy stored in the inductor L1 is timely consumed and absorbed due to the energy storage capacitor E1, thereby eliminating howling noise caused by abrupt voltage or current change of the inductor L1.
The freewheeling diode D1 connected in parallel to the inductor L1 and the two ends of the light emitting portion 11 in the embodiment of the present invention is a diode used with the inductor L1, when the current loaded by the inductor L1 suddenly changes or decreases, abrupt voltage will be generated at the two ends of the inductor L1, which may cause other components to be broken down or burned out by the induced voltage, such as the light source in the embodiment, which may be broken down and damaged by the voltage released by the instant inductor L1 when the power supply is stopped. In this embodiment, the freewheeling diode D1 cooperating with the inductor L1 is added to the light-emitting circuit 10, so that the current can be further changed more gradually, the occurrence of a surge voltage is avoided, and the light source is further protected.
Optionally, referring to fig. 2, the pulse width control circuit 20 includes an enable terminal 21, an input terminal 22, and a control terminal 23, where the enable terminal 21 of the pulse width control circuit 20 is used to access a pulse width control signal, and the input terminal 22 of the pulse width control circuit 20 is connected to an output terminal of the power supply circuit 30; the output end of the energy supply circuit 30 is also connected with one end of the light-emitting circuit 10, and the other end of the light-emitting circuit 10 is connected with the control end 23 of the pulse width control circuit 20; the control terminal 23 of the pulse width control circuit 20 is used for controlling whether the other end of the light emitting circuit 10 is grounded according to the pulse width control signal.
Wherein the pulse width control signal can be connected to the pulse width control circuit 20 through the enable terminal 21; the voltage output by the energy supply circuit 30 can enter the pulse width control circuit 20 through the input end 22 of the pulse width control circuit 20, and can be connected with one end of the light emitting circuit 10 to supply constant current to the light emitting circuit 10; in addition, the other end of the light emitting circuit 10 may be connected to the control terminal 23 of the pulse width control circuit 20. Under the action of the pulse width control signal connected through the enabling terminal 21, if the control terminal 23 can control the light-emitting circuit 10 and the energy supply circuit 30 to form a loop and conduct; for example, when the pulse width control signal is at a high level, the control terminal 23 is grounded at this time, so that the other end of the light emitting circuit 10 can be grounded through the control terminal 23 of the pulse width control circuit 20, so that the other end of the light emitting circuit 10 is grounded, thereby forming a loop with the power supply circuit 30; at this time, the voltage input from the power supply circuit 30 can flow through the light emitting circuit 10 and be conducted to the ground of the pulse width control circuit 20, so that a closed loop is formed inside the dimming control device. Conversely, if the control terminal 23 is capable of controlling the light emitting circuit 10 to be disconnected from the pulse width control circuit 20; for example, when the pulse width control signal is at a low level, the control terminal 23 is not grounded, so that the other end of the light emitting circuit 10 is not grounded. In the embodiment of the present invention, the PWM control circuit 20 is similar to the switch of the dimming control device, and the PWM control circuit 20 is configured to receive a PWM signal (i.e., a PWM control signal) and control whether each circuit in the dimming control device is turned on or not based on the PWM signal. Alternatively, the pulse width control circuit 20 may comprise a PWM controller having an enable terminal 21, an input terminal 22, and a control terminal 23. The present embodiment is not limited to this, and an existing mature PWM controller may be used.
The pulse width control signal is a digital signal displayed as a continuous, standard waveform, and for example, the digital signal may be output and displayed in the form of a sine wave, a square wave, or the like. The embodiment of the invention adopts square waves to display the pulse width control signal, the pulse width control signal comprises two levels with fixed sizes, namely a low level and a high level, and the continuous time period corresponding to one high level and one low level is called one pulse period (or power supply period), and the pulse control signal comprises a plurality of continuous pulse periods. The pulse control signal may be described in terms of a duty cycle, i.e. the duty cycle represents the proportion of the power-on time relative to the total time in one pulse period. For example, the duty cycle of the square wave is 50%, indicating that the high level and low level occupy 0.5 cycles respectively.
In the embodiment of the present invention, when the pulse control signal is at the high level, the voltage outputted by the power supply circuit 30 can flow to the pulse control circuit through the light emitting circuit 10, and is grounded through the control terminal 23 of the pulse width control circuit 20 to form a conduction. When the pulse control signal is low, the power supply circuit 30 is connected to the light emitting circuit 10, but the power supply circuit and the light emitting circuit cannot form a loop, and are not conducted. The dimming control device can achieve the purpose of controlling current by changing the duty ratio of the pulse width control signal.
Optionally, referring to fig. 2, the pulse width control circuit 20 further includes a current detection resistor R2, where the current detection resistor R2 is used to detect the average current of the light emitting circuit 10.
The current detecting resistor R2, i.e. a current detecting resistor, may be connected in the pulse width control circuit 20, where the current detecting resistor R2 and the detected device are connected in series through an internal circuit of the pulse width control circuit 20, so as to sample the current flowing through the device. In this embodiment, the current detection resistor R2 is used to detect the average current of the light emitting circuit 10, and the current detection resistor R2 ensures that a constant current is realized, so that the current flowing through the light source in the light emitting circuit 10 meets the dimming requirement.
Optionally, the frequency of the pulse width control signal is not less than 1000Hz.
The dimming accuracy of the pwm control circuit 20 is related to the frequency of the pwm control signal and the dimming step. The embodiment of the present invention can set the dimming accuracy of the pulse width control circuit 20 on the basis of the pulse width control signal frequency of not less than 1000Hz. For example, the frequency of the pulse width control signal is 4000Hz, or 4000Hz or more, and the dimming step may be employed at 1000 or more. If the frequency of the 4000Hz pulse width control signal is selected, compared with the current common frequency of the 1000Hz pulse width control signal, the frequency of the 4000Hz pulse width control signal in the same unit time is 4 times of the dimming period of the 1000Hz pulse width control signal, namely 4 times of the dimming depth. The dimming accuracy of the pwm control circuit 20 in this embodiment reaches 1:4000, i.e., 0.025%. The embodiment of the invention determines the pulse width control circuit 20 with high dimming precision by selecting the pulse width control signal with high frequency, thereby realizing high-precision constant-current and accurate control dimming.
Optionally, the resistance value of the load resistor R1 is not less than a preset threshold, where the preset threshold is:
wherein V is in Represents the voltage value output by the energy supply circuit 30, I min Represents a minimum current value, min (I LED ) Current I representing the light source capable of emitting light LED Is a minimum of (2).
In the selection of the resistance value of the load resistor R1, the electric quantity consumed by the load resistor R1 is low, and at the same time, when dimming is performed to the lowest dimming scale (for example, when the light source such as the LED lamp bead string can be on under the current dimming scale, but one dimming scale LED lamp bead string is turned off after being reduced, the current dimming scale can be called the lowest dimming scale), a part of the electric quantity stored in the energy storage capacitor E1 can be consumed by using the load resistor R1, and in addition, the LED lamp bead string needs to be ensured to be kept on, and the macroscopic low light level is emitted. Therefore, the resistance value of the load resistor R1 needs to be set reasonably.
In the embodiment of the invention, since the load resistor R1 is connected in parallel with the light source, the load resistor R1 can divide the current which should flow through the light source entirely into a part, and in order to ensure that the light source can still keep emitting light after the load resistor R1 is divided, the current which needs to flow through the light source is not less than the current I which can make the light source emit light LED I.e. not less than min (I LED ). At the lowest dimming level, the energizing circuit 30 emits light to the lampThe current value provided when the circuit 10 is powered is I min The current value of the shunt of the load resistor R1 is smaller than I min -min(I LED ) At this time, it is ensured that the current value flowing through the light source is larger than min (I LED ) I.e. the light source may emit light.
If the voltage value provided by the power supply circuit 30 is V in The voltage across the load circuit is less than V in Therefore, the maximum value of the load circuit shunt is V in /R 1 . If the maximum value V of the load circuit shunt in /R 1 Not greater than I min -min(I LED ) The light source can be ensured to emit light; thus, the resistance R of the load resistor R1 is obtained 1 Need to be greater than or equal toTherefore, the light-emitting brightness of the light source can be reduced and the power supply can emit light at the lowest dimming scale.
In addition, in the case that the light source is an LED light source, it is known that the current difference of the LED light source at different brightness is large and the voltage difference is small (substantially the same) based on the volt-ampere characteristics of the LED; that is, the current value of the load resistor R1 is not changed much at different brightnesses of the LED light sources, but the current of the LED light sources is large at high brightnesses, and at this time, the current split effect of the load resistor R1 is not obvious, and the current consumed by the load resistor R1 is negligible compared with the whole current, so that the load resistor R1 may not affect the light emission brightness of the LED light sources at high brightnesses. That is, the dimming control means can further lower the minimum brightness of the light source without changing the high brightness of the light source.
The embodiment of the invention can determine the resistance value of the load resistor R1 which needs to be connected in parallel with the light source based on the voltage value output by the energy supply circuit 30, the minimum current value in the light-emitting circuit 10 and the minimum current value which can enable the light source to keep emitting, can enable the light source to further reduce the brightness under the condition of dimming to the lowest scale, and can ensure that the load resistor R1 can realize shunting and simultaneously ensure that the light source keeps emitting.
Alternatively, the number of the light emitting circuits 10 and the pulse width control circuits 20 is the same and plural, and the plural light emitting circuits 10 and the plural pulse width control circuits 20 share the same power supply circuit 30; each pulse width control circuit 20 is for controlling whether the energizing circuit 30 supplies constant current to the corresponding light emitting circuit 10.
In the embodiment of the present invention, a plurality of light emitting circuits 10 and pulse width control circuits 20 may be provided, and each light emitting circuit 10 has a corresponding pulse width control circuit 20 capable of controlling the light emitting circuit 10. The different pulse width control circuits 20 can be used for controlling different light emitting circuits 10 under the scenes of supermarkets, large-scale markets and the like. In addition, in the embodiment of the present invention, a plurality of energy supply circuits 30 do not need to be provided to be matched with a plurality of groups of light emitting circuits 10 and pulse width control circuits 20 one by one, and only one energy supply circuit 30 is needed to perform constant current power supply on different light emitting circuits 10 according to the pulse width control signals output by each pulse width control circuit 20, so that the circuit design is not more complicated due to the fact that a plurality of groups of light emitting circuits 10 and pulse width control circuits 20 are connected.
The foregoing is merely a specific implementation of the embodiment of the present invention, but the protection scope of the embodiment of the present invention is not limited thereto, and any person skilled in the art can easily think about changes or substitutions within the technical scope of the embodiment of the present invention, and the changes or substitutions are covered by the protection scope of the embodiment of the present invention. Therefore, the protection scope of the embodiments of the present invention shall be subject to the protection scope of the claims.
Claims (8)
1. A dimming control device, comprising: the light-emitting device comprises a light-emitting circuit, a pulse width control circuit and an energy supply circuit, wherein the light-emitting circuit comprises a light-emitting part;
the light-emitting part comprises a light source, an energy storage capacitor and a load resistor, wherein the energy storage capacitor and the load resistor are connected with the light source in parallel;
the pulse width control circuit is used for accessing a pulse width control signal and controlling whether the energy supply circuit supplies power to the light-emitting circuit in a constant current mode according to the pulse width control signal, wherein the light-emitting circuit works in a constant current mode;
when the energy supply circuit can supply power to the light emitting circuit, the energy supply circuit can supply power to the light emitting part;
wherein, the resistance value of the load resistor is not less than a preset threshold value, and the preset threshold value is:
wherein V is in Representing the voltage value output by the energy supply circuit, I min Represents a minimum current value, min (I LED ) Current I representing the light source capable of emitting light LED Is a minimum of (2).
2. The apparatus of claim 1, wherein the light emitting circuit further comprises an inductor and a freewheeling diode;
the inductor is connected in series with the light emitting part, and the flywheel diode is connected in parallel with the inductor and the light emitting part which are connected in series.
3. The apparatus of claim 1, wherein an enable terminal of the pulse width control circuit is configured to access the pulse width control signal, and an input terminal of the pulse width control circuit is connected to an output terminal of the power supply circuit;
the output end of the energy supply circuit is also connected with one end of the light-emitting circuit, and the other end of the light-emitting circuit is connected with the control end of the pulse width control circuit;
the control end of the pulse width control circuit is used for controlling whether the other end of the light-emitting circuit is grounded or not according to the pulse width control signal.
4. A device according to claim 3, wherein when the pulse width control signal is at a high level, the other end of the light emitting circuit is grounded through a control terminal of the pulse width control circuit;
when the pulse width control signal is at a low level, the other end of the light emitting circuit is not grounded.
5. The apparatus of claim 1, wherein the pulse width control circuit further comprises a current sensing resistor for sensing an average current of the light emitting circuit.
6. The apparatus of any one of claims 1-5, wherein the number of light emitting circuits and the pulse width control circuits are the same and are plural, and wherein the plurality of light emitting circuits and the plurality of pulse width control circuits share the same power supply circuit;
each pulse width control circuit is used for controlling whether the energy supply circuit supplies power to the corresponding light-emitting circuit in a constant current mode.
7. The device of any of claims 1-5, wherein the light source comprises a plurality of LEDs in series, a plurality of LEDs in parallel, or a group of LEDs collectively formed by a plurality of series and parallel arrangements.
8. The apparatus of any of claims 1-5, wherein the pulse width control signal has a frequency of not less than 1000Hz.
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