CN111200892A - LED control device, circuit and control method thereof - Google Patents
LED control device, circuit and control method thereof Download PDFInfo
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Abstract
The invention discloses an LED control device, a circuit and a control method thereof, wherein the LED control circuit comprises a control module, at least one LED lamp string and constant current source modules with the number corresponding to that of the LED lamp strings; the control module is used for outputting dimming voltage to the constant current source module according to an externally input dimming signal; the constant current source module is used for adjusting the working current of the LED lamp string according to the dimming voltage; the control module is further used for comparing the voltage value of the dimming signal with at least one preset comparison voltage, selecting a corresponding power supply voltage according to a comparison result, outputting the power supply voltage to the constant current source module, and controlling the difference value between the power supply voltage and the output voltage of the constant current source module, so that the light emitting flicker of the LED lamp string when the brightness is reduced and the conduction radiation caused by sudden change of the working current are avoided.
Description
Technical Field
The invention relates to the technical field of LEDs, in particular to an LED control device, circuit and control method.
Background
In LED dimming applications, a constant current circuit is usually used to control the current of the LED string to make it emit light, the constant current circuit is composed of an operational amplifier and an N-type MOS transistor, and the current flowing through the LED string can be controlled by adjusting the voltage at the positive input end of the operational amplifier, so as to implement dimming applications.
As shown in fig. 1, the power supply of the operational amplifier is terminated with VDDO, when the line voltage is less than the LED string voltage, the inverting input terminal of the operational amplifier is grounded through the sampling resistor, the output voltage of the operational amplifier is VDD0, the MOS transistor Q is turned on, when the line voltage rises and is greater than the sum of the LED string voltage and the Vds voltage of the MOS transistor, the LED string starts to have current flowing, the inverting input terminal voltage of the operational amplifier is equal to Rcs0 + Iled0, Iled0 is the LED string current, when the dimming voltage is not changed, the inverting input terminal voltage of the operational amplifier changes to the output terminal voltage stabilization and requires response time, the output terminal voltage of the operational amplifier drops from VDD0 to Vs0 in the response time, Vs0 is the output voltage when the operational amplifier corresponding to the dimming voltage is stabilized, the LED string current also drops from VDD0 to the LED string constant current set by the dimming voltage, i.e., dimming voltage/Rcs 0. During the time when the output end voltage of the operational amplifier changes from VDD0 to Vs0, which is determined by the response time of the operational amplifier, the LED string current generates sudden change, and the magnitude of the sudden change is determined by the difference between VDD0 and Vs 0. When the dimming voltage is adjusted to be smaller by the controller, the output voltage Vs0 is smaller when the operational amplifier is stable, and the difference between VDD0-Vs0 is larger, so that the current jump of the LED string is larger, and a series of problems such as low power factor, harmonic deterioration and conducted radiation are caused, and even when the brightness of the LED string is adjusted to be a certain degree, the current jump causes the LED string to flicker.
Thus, the prior art has yet to be improved and enhanced.
Disclosure of Invention
In view of the above-mentioned shortcomings of the prior art, the present invention provides an LED control device, an LED control circuit and an LED control method, which can effectively avoid the light-emitting flicker of the LED string during dimming and the conduction radiation caused by the sudden change of the operating current.
In order to achieve the purpose, the invention adopts the following technical scheme:
an LED control circuit comprises a control module, at least one LED lamp string and constant current source modules, wherein the number of the constant current source modules corresponds to that of the LED lamp strings; the control module is used for outputting dimming voltage to the constant current source module according to an externally input dimming signal; the constant current source module is used for adjusting the working current of the LED lamp string according to the dimming voltage; the control module is further configured to compare the voltage value of the dimming signal with at least one preset comparison voltage, select a corresponding supply voltage according to a comparison result, output the corresponding supply voltage to the constant current source module, and control a difference between the supply voltage and an output voltage of the constant current source module.
In the LED control circuit, the control module is specifically configured to compare a voltage value of the dimming signal with a first preset comparison voltage and a second preset comparison voltage, and output a first power supply voltage to the constant current source module when the voltage value of the dimming signal is smaller than the first preset comparison voltage; when the voltage value of the dimming signal is greater than the first preset comparison voltage and less than the second preset voltage, outputting a second power supply voltage to the constant current source module; when the voltage value of the dimming signal is greater than the second preset voltage, outputting a third power supply voltage to the constant current source module; the first preset comparison voltage is smaller than the second preset comparison voltage.
In the LED control circuit, the control module comprises a comparison unit, a control unit and a voltage output unit; the voltage output unit is used for outputting the power supply voltage to the constant current source module according to a reference voltage; the comparison unit is used for comparing the voltage value of the dimming signal with the first preset voltage and the second preset voltage and outputting a corresponding level signal to the control unit according to a comparison result; and the control unit controls the voltage output unit to output the corresponding power supply voltage to the constant current source module according to the level signal.
In the LED control circuit, the comparison unit comprises a first comparator and a second comparator; the positive phase input end of the first comparator is connected with the dimming signal input end, the negative phase input end of the first comparator is connected with the first preset comparison voltage input end, and the output end of the first comparator is connected with the control unit; the positive phase input end of the second comparator is connected with the dimming signal input end, the negative phase input end of the second comparator is connected with the second preset comparison voltage input end, and the output end of the second comparator is connected with the control unit.
In the LED control circuit, the control unit comprises a first switch, a second resistor and a third resistor; one end of the first switch is connected with the voltage output unit and one end of the first resistor, the other end of the first switch and the other end of the first resistor are connected with one end of the second switch and one end of the second resistor, and the other end of the second resistor and the other end of the second switch are connected with the voltage output unit; and the control end of the first switch and the control end of the second switch are both connected with the comparison unit.
In the LED control circuit, the voltage output unit comprises a first operational amplifier, a first MOS (metal oxide semiconductor) tube, a third resistor and a fourth resistor; the positive phase input end of the first operational amplifier is connected with a reference voltage input end, the negative phase input end of the first operational amplifier is connected with the control unit and one end of the fourth resistor, the output end of the first operational amplifier is connected with the grid electrode of the first MOS tube, the source electrode of the first MOS tube is connected with the other end of the fourth resistor and the constant current source module, and the drain electrode of the first MOS tube is connected with a line voltage input end; one end of the third resistor is connected with the control unit, and the other end of the third resistor is grounded.
In the LED control circuit, the control module further includes a filtering unit, and the filtering unit is configured to filter the dimming signal and output the filtered dimming signal to the comparing unit.
In the LED control circuit, the filtering unit comprises a capacitor and a fifth resistor; one end of the capacitor is connected with one end of the fifth resistor and the comparison unit, and the other end of the capacitor is grounded; the other end of the fifth resistor is connected with a dimming signal input end.
A control method based on the LED control circuit comprises the following steps:
the control module outputs dimming voltage to the constant current source module according to an externally input dimming signal;
the constant current source module adjusts the working current of the LED lamp string according to the dimming voltage;
the control module is further used for comparing the voltage value of the dimming signal with at least one preset comparison voltage, outputting a corresponding power supply voltage to the constant current source module according to a comparison result, and controlling the difference value between the power supply voltage and the output voltage of the constant current source module.
The LED control device comprises a shell, wherein a PCB is arranged in the shell, and the LED control device is characterized in that the PCB is provided with the LED control circuit.
Compared with the prior art, the LED control device, the LED control circuit and the LED control method provided by the invention have the advantages that the LED control circuit comprises a control module, at least one LED lamp string and constant current source modules with the quantity corresponding to that of the LED lamp strings; the control module is used for outputting dimming voltage to the constant current source module according to an externally input dimming signal; the constant current source module is used for adjusting the working current of the LED lamp string according to the dimming voltage; the control module is further used for comparing the voltage value of the dimming signal with at least one preset comparison voltage, selecting a corresponding power supply voltage according to a comparison result, outputting the power supply voltage to the constant current source module, and controlling the difference value between the power supply voltage and the output voltage of the constant current source module, so that the light emitting flicker of the LED lamp string when the brightness is reduced and the conduction radiation caused by sudden change of the working current are avoided.
Drawings
FIG. 1 is a circuit schematic of a prior art LED control circuit;
FIG. 2 is a block diagram of an LED control circuit according to the present invention;
FIG. 3 is a schematic circuit diagram of a first embodiment of an LED control circuit according to the present invention;
FIG. 4 is a schematic circuit diagram of a second embodiment of an LED control circuit according to the present invention;
fig. 5 and fig. 6 are schematic circuit diagrams of a constant current source module and an LED light string in an LED control circuit according to the present invention;
fig. 7 is a flowchart illustrating steps of a method for controlling an LED control circuit according to the present invention.
Detailed Description
The LED control device, the circuit and the control method thereof can effectively avoid the light-emitting flicker of the LED lamp string when the brightness is reduced and the conduction radiation caused by the sudden change of the working current.
In order to make the objects, technical solutions and effects of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 2, the LED control circuit according to the present invention includes a rectifying module 100, a control module 200, at least one LED string 300, and constant current source modules 400 corresponding to the number of the LED string 300; the number of the LED light strings 300 is one or more, when there are a plurality of LED light strings 300, the LED light strings 300 are connected in series, the positive electrode of the LED light string 300 obtained after the series connection is connected to the rectifier module 100, and the negative electrode is connected to the constant current source module 400; when the LED light string 300 is one, similarly, the positive electrode of the LED light string 300 is connected to the rectifying module 100, and the negative electrode of the LED light string 300 is connected to the constant current source module 400; the rectifying module 100 is further connected to an ac input terminal and the control module 200, and the control module 200 is further connected to the constant current source module 400.
The rectifier module 100 converts an input alternating current into a line voltage, outputs the line voltage to the LED light string 300 and the control module 200, and provides electric energy for the control module 200 and the LED light string 300; the control module 200 is configured to output a dimming voltage to the constant current source module 400 according to an externally input dimming signal; the constant current source module 400 is configured to adjust the working current of the LED light string 300 according to the dimming voltage; the control module 200 is further configured to compare the voltage value of the dimming signal with at least one preset comparison voltage, select a corresponding supply voltage VDD according to a comparison result, and output the corresponding supply voltage VDD to the constant current source module 400, and control a difference between the supply voltage VDD and an output voltage of the constant current source module 400, specifically, control to reduce the difference between the supply voltage VDD and the output voltage of the constant current source module 400; according to the invention, the control module 200 controls the supply voltage VDD to change along with the voltage value of the dimming signal, so that the difference between the supply voltage VDD and the output voltage of the constant current source module 400 is reduced, the sudden change of the working current of the LED lamp string 300 is reduced, the light emitting flicker of the LED lamp string 300 during brightness reduction is improved, the power factor is improved, and the harmonic value is reduced.
Further, the working process of the LED control circuit is specifically described by setting two comparison preset voltages, and the number of the comparison voltages may be set according to requirements in other embodiments, which is not limited in the present invention.
The control module 200 is specifically configured to compare the voltage value of the dimming signal with a first preset comparison voltage Vref1 and a second preset comparison voltage Vref2, where the first preset comparison voltage Vref1 is smaller than the second preset comparison voltage Vref2, and when the voltage value of the dimming signal is smaller than the first preset comparison voltage Vref1, output a first power supply voltage to the constant current source module 400; when the voltage value of the dimming signal is greater than the first preset comparison voltage Vref1 and less than the second preset voltage, outputting a second power supply voltage to the constant current source module 400; when the voltage value of the dimming signal is greater than the second preset voltage, outputting a third supply voltage to the constant current source module 400, dividing the voltage value of the dimming signal into three parts by setting two comparison voltages, that is, outputting a corresponding supply voltage VDD according to the voltage value of the dimming signal, so that the supply voltage VDD changes according to the change of the dimming signal, thereby reducing the difference between the supply voltage VDD and the output voltage of the constant current source module 400, so as to reduce the sudden change of the operating current of the LED lamp string 300; when more comparison voltages are set, it is indicated that the voltage values of the dimming signals are divided more finely, and the difference between the corresponding supply voltage VDD and the output voltage is smaller, so that the power factor is further improved, and the harmonic is reduced.
In specific implementation, referring to fig. 3, in the first embodiment of the present invention, the control module 200 includes a comparing unit 210, a control unit 220 and a voltage output unit 230, the comparing unit 210 is connected to a dimming signal input end and the control unit 220, the control unit 220 is further connected to the voltage output unit 230, and the voltage output unit 230 is further connected to the constant current source module 400 and the rectifying module 100.
The voltage output unit 230 is configured to output the supply voltage VDD to the constant current source module 400 according to a reference voltage; the comparing unit 210 is configured to compare the voltage value of the dimming signal with the first preset voltage and the second preset voltage, and output a corresponding level signal to the control unit 220 according to a comparison result; the control unit 220 controls the voltage output unit 230 to output the corresponding power supply voltage VDD to the constant current source module 400 according to the level signal; the comparing unit 210 compares that when the voltage value of the dimming signal is smaller than the first preset comparison voltage Vref1, two low level signals are output to the control unit 220, and the control unit 220 controls the voltage output unit 230 to output a first power supply voltage to the constant current source module 400; when the voltage value of the dimming signal is greater than the first preset comparison voltage Vref1 and less than the second preset voltage, outputting a low level signal and a high level signal to the control unit 220, and the corresponding voltage output unit 230 outputs a second supply voltage to the constant current source module 400; when the voltage value of the dimming signal is greater than the second preset voltage, two high level signals are output to the control unit 220, and the corresponding voltage output unit 230 outputs a third supply voltage to the constant current source module 400, so as to output different supply voltages VDD according to the voltage value of the dimming signal.
Further, the comparing unit 210 includes a first comparator COMP1 and a second comparator COMP 2; a non-inverting input end of the first comparator COMP1 is connected to a dimming signal input end, an inverting input end of the first comparator COMP1 is connected to a first preset comparison voltage Vref1 input end, and an output end of the first comparator COMP1 is connected to the control unit 220; a non-inverting input terminal of the second comparator COMP2 is connected to an input terminal of a dimming signal, an inverting input terminal of the second comparator COMP2 is connected to an input terminal of a second preset comparison voltage Vref2, an output terminal of the second comparator COMP2 is connected to the control unit 220, in this embodiment, an analog voltage dimming signal is used as the dimming signal, the first comparator COMP1 directly compares the input dimming signal with a first preset comparison voltage Vref1, the second comparator COMP2 compares the dimming signal with the second preset comparison voltage Vref2, when a voltage value of the dimming signal is less than the first preset comparison voltage Vref1, both the first comparator COMP1 and the second comparator COMP2 output a low level, and when the voltage value of the dimming signal is greater than the first preset comparison voltage 1 and less than the second preset voltage Vref, the first comparator COMP1 outputs a high level signal, the second comparator COMP2 outputs a low level signal, and when the voltage value of the dimming signal is greater than the second preset voltage, the first comparator COMP1 and the second comparator COMP2 both output a high level signal, thereby implementing effective control on the control unit 220.
Further, with continued reference to fig. 3, the control unit 220 includes a first switch K1, a second switch K2, a second resistor R2 and a third resistor R3; one end of the first switch K1 is connected to the voltage output unit 230 and one end of the first resistor R1, the other end of the first switch K1 and the other end of the first resistor R1 are connected to one end of the second switch K2 and one end of the second resistor R2, the other end of the second resistor R2 and the other end of the second switch K2 are connected to the voltage output unit 230, and the first switch K1 and the second switch K2 can be realized by a relay, a triode, a MOSFET, a transmission gate, and the like; a control end of the first switch K1 is connected to an output end of the second comparator COMP2, a control end of the second switch K2 is connected to an output end of the first comparator COMP1, the first comparator COMP1 controls on/off of the second switch K2, and the second comparator COMP2 controls on/off of the first switch K1, so as to control access states of the first resistor R1 and the second resistor R2 to change a divided voltage of the reference voltage, thereby changing a magnitude of the supply voltage output by the voltage output unit 230.
Further, the voltage output unit 230 includes a first operational amplifier OP1, a first MOS transistor Q1, a third resistor R3, and a fourth resistor R4; a non-inverting input terminal of the first operational amplifier OP1 is connected to a reference voltage input terminal, an inverting input terminal of the first operational amplifier OP1 is connected to the control unit 220 and one end of the fourth resistor R4, an output terminal of the first operational amplifier OP1 is connected to a gate of the first MOS transistor Q1, a source of the first MOS transistor Q1 is connected to the other end of the fourth resistor R4 and the constant current source module 400, and a drain of the first MOS transistor Q1 is connected to a line voltage input terminal; one end of the third resistor R3 is connected to the control unit 220, and the other end of the third resistor R3 is grounded, so as to provide the supply voltage VDD for the constant current source module 400 according to the reference voltage through the voltage output unit 230.
When the first comparator COMP1 and the second comparator COMP2 both output low level signals, the first switch K1 and the second switch K2 are both controlled to be turned off, at this time, the first resistor R1 and the second resistor R2 are both not short-circuited and are connected to a circuit, and the supply voltage VDD ═ Vref3 (R4+ R1+ R2+ R3)/(R1+ R2+ R3) is the first supply voltage; when the first comparator COMP1 outputs a high level signal, the second comparator COMP2 outputs a low level signal, and the second switch K2 is controlled to be turned on, and the first switch K1 is turned off, then the second resistor R2 is short-circuited, and the supply voltage VDD ═ Vref3 (R4+ R1+ R3)/(R1+ R3) is a second supply voltage; when the first comparator COMP1 and the second comparator COMP2 both output a high level and control the first switch K1 and the second switch K2 to be turned off, the first resistor R1 and the second resistor R2 are both short-circuited, and the supply voltage VDD is Vref3 (R4+ R3)/R3 is the third supply voltage.
Therefore, by dividing the voltage value of the dimming signal into three parts (smaller than the first preset comparison voltage Vref1, larger than the first preset comparison voltage Vref1, smaller than the second preset comparison voltage Vref2, and larger than the second preset comparison voltage Vref2), three different supply voltages VDD are correspondingly generated, and the supply voltage VDD has a low voltage value when the dimming signal voltage is low and a high voltage value when the dimming signal voltage is high, and the difference between the supply voltage VDD and the output voltage Vs of the constant current source module 400 is smaller compared with a mode of using only one VDD voltage, accordingly, when a current flows through the LED light string 300, the time from the output supply voltage VDD to the stable output voltage Vs of the constant current source module 400 is shortened, the current variation range of the LED light string 300 is smaller, and further, the light emitting flicker of the LED light string 300 during brightness dimming is improved, the power factor is increased, and the power factor is increased, Reduce harmonic values and improve the conduction radiation caused by sudden changes of the current of the LED string 300.
Further, referring to fig. 4, in a second embodiment of the present invention, the control module 200 further includes a filtering unit 240, where the filtering unit 240 is configured to filter the dimming signal and output the dimming signal to the comparing unit 210, in this embodiment, a PWM dimming signal is used as the dimming signal, the dimming signal is filtered and converted into an analog voltage signal by the filtering unit 240, and then the analog voltage signal is output to the first comparator COMP1 and the second comparator COMP2 for comparison, so as to complete control of the first switch K1 and the second switch K2, and since working principles of the first comparator COMP1 and the second comparator COMP2 are the same as those of the first embodiment, details are not repeated herein.
Further, the filtering unit 240 includes a capacitor C1 and a fifth resistor R5; one end of the capacitor C1 is connected to one end of the fifth resistor R5 and the comparison unit 210, and the other end of the capacitor C1 is grounded; the other end of the fifth resistor R5 is connected to a dimming signal input end, and the filtering processing of the dimming signal is realized through the fifth resistor R5 and the capacitor C1.
Further, the number of the LED light strings 300 in the first embodiment and the second embodiment may be one or more, and when there is one LED light string 300, as shown in fig. 5, that is, the LED control circuit is a single-segment LED light string structure, and there is one corresponding constant current source module 400 to control the working current; in the single-segment LED string structure, when the line voltage output by the rectifier module 100 is increased and is greater than the voltage of the LED string 300, the LED string 300 emits light according to the current set by the dimming voltage; when the line voltage output by the rectifying module 100 is reduced to be less than the voltage of the LED light string 300, no current flows through the LED light string 300, and the LED light string 300 does not emit light.
When there are a plurality of LED light strings 300, as shown in fig. 6, the LED control circuit is a multi-segment LED light string series structure, in this embodiment, three segments of LED light strings 300 (an LED1 light string, an LED2 light string, and an LED3 light string) are connected in series for explanation, and certainly, two, four or more segments may be used, which is not limited in the present invention, and three constant current source modules 400 are correspondingly provided to control the working current of each LED light string 300; when the line voltage rises to be greater than the string voltage of the LED1 and less than the string voltage of the LED1+ LED2, the LED1 string lights emit light according to the current set after the voltage division of the dimming voltage; when the line voltage rises to be greater than the voltage of the LED1+ LED2 string and less than the voltage of the LED1+ LED2+ LED3 string, the LED1 string and the LED2 string emit light according to the current set after the dimming voltage is divided, and the current is greater than the current when the LED1 string emits light independently; when the line voltage is continuously increased to be larger than the string voltage of the LED1+ the LED2+ the LED3, the LED1 string, the LED2 string and the LED3 string emit light according to the current set after the dimming voltage is divided, and the current is larger than the current generated when the LED1+ the LED2 emit light together. Similarly, when the line voltage decreases, the current is turned off in the order of LED3-LED2-LED 1. Compared with the single-section LED lamp string 300 structure, the three-section cascade structure has the advantages that in a line voltage period, the current of the LED lamp string 300 is gradually increased along with the increase of the line voltage, the current of the LED lamp string 300 is gradually reduced along with the reduction of the line voltage, the LED lamp string 300 is lightened for a longer light-emitting time, the power factor is higher, the harmonic wave is lower, and the light effect is higher.
Further, please refer to fig. 2, each of the constant current source modules 400 includes a second operational amplifier OP2 and a second MOS transistor Q2, a power input terminal of a second operational amplifier OP2 of each of the constant current source modules 400 is connected to the control module 200, a non-inverting input terminal of the second operational amplifier OP2 is connected to the control module 200, an inverting input terminal of the second operational amplifier OP2 is connected to one end of the sampling resistor and the source of the second MOS transistor Q2, an output terminal of the second operational amplifier OP2 is connected to the gate of the second MOS transistor Q2, and a drain of the second MOS transistor Q2 is connected to the rectifying module 100.
The power supply voltage outputted by the control module 200 in the first embodiment and the second embodiment is inputted to the power input terminal of the second operational amplifier, such as the power input terminal of the second operational amplifier OP22 in fig. 5, or the power input terminals of the second operational amplifiers OP22, OP23 and OP24 in fig. 6, the power input terminals of the second operational amplifiers OP22, OP23 and OP24 share the power supply voltage outputted by the control module 200, the output voltage of the constant current source module 400 is the output voltage of the output terminal of the second operational amplifier, three different power supply voltages VDD are generated by dividing the voltage of the dimming signal into three parts (less than the first preset comparison voltage Vref1, more than the first preset comparison voltage Vref1, less than the second preset comparison voltage Vref2, and more than the second preset comparison voltage Vref2), and the voltage value of the power supply voltage VDD is low when the dimming signal is low, when the dimming signal voltage is high, the voltage value is also high, and compared with a mode of only using one VDD voltage, the difference value between the supply voltage VDD and the output voltage Vs of the second operational amplifier is smaller, accordingly, when the current flows through the LED light string 300, the time from the output supply voltage VDD to the stable output voltage Vs of the second operational amplifier is shortened, the current mutation range of the LED light string 300 is smaller, and further the problems of light emitting flicker of the LED light string 300 during brightness dimming, power factor improvement, harmonic value reduction, conductive radiation caused by the current mutation of the LED light string 300 and the like are solved.
Based on the above LED lamp adaptive driving circuit, please refer to fig. 7, the present invention further provides a driving method of the LED lamp adaptive driving circuit, which specifically includes the following steps:
s100, the control module outputs dimming voltage to the constant current source module according to an externally input dimming signal;
s200, the constant current source module adjusts the working current of the LED lamp string according to the dimming voltage;
and S300, after comparing the voltage value of the dimming signal with at least one preset comparison voltage, the control module outputs a corresponding power supply voltage to the constant current source module according to a comparison result, and controls the difference value between the power supply voltage and the output voltage of the constant current source module.
Based on the LED control circuit, the invention also provides a corresponding LED control device, which includes a housing, wherein a PCB is disposed in the housing, the PCB is disposed with the LED control circuit, and the LED control circuit is described in detail above, so that the details are not repeated herein.
In summary, the LED control device, the LED control circuit and the LED control method provided by the present invention comprise a control module, at least one LED string and constant current source modules corresponding to the number of the LED strings; the control module is used for outputting dimming voltage to the constant current source module according to an externally input dimming signal; the constant current source module is used for adjusting the working current of the LED lamp string according to the dimming voltage; the control module is further used for comparing the voltage value of the dimming signal with at least one preset comparison voltage, selecting a corresponding power supply voltage according to a comparison result, outputting the power supply voltage to the constant current source module, and controlling the difference value between the power supply voltage and the output voltage of the constant current source module, so that the light emitting flicker of the LED lamp string when the brightness is reduced and the conduction radiation caused by sudden change of the working current are avoided.
It should be understood that equivalents and modifications of the technical solution and inventive concept thereof may occur to those skilled in the art, and all such modifications and alterations should fall within the scope of the appended claims.
Claims (10)
1. An LED control circuit is characterized by comprising a control module, at least one LED lamp string and constant current source modules, wherein the number of the constant current source modules corresponds to that of the LED lamp strings; the control module is used for outputting dimming voltage to the constant current source module according to an externally input dimming signal; the constant current source module is used for adjusting the working current of the LED lamp string according to the dimming voltage; the control module is further configured to compare the voltage value of the dimming signal with at least one preset comparison voltage, select a corresponding supply voltage according to a comparison result, output the corresponding supply voltage to the constant current source module, and control a difference between the supply voltage and an output voltage of the constant current source module.
2. The LED control circuit according to claim 1, wherein the control module is specifically configured to compare the voltage value of the dimming signal with a first preset comparison voltage and a second preset comparison voltage, and output a first supply voltage to the constant current source module when the voltage value of the dimming signal is smaller than the first preset comparison voltage; when the voltage value of the dimming signal is greater than the first preset comparison voltage and less than the second preset voltage, outputting a second power supply voltage to the constant current source module; when the voltage value of the dimming signal is greater than the second preset voltage, outputting a third power supply voltage to the constant current source module; the first preset comparison voltage is smaller than the second preset comparison voltage.
3. The LED control circuit of claim 2, wherein the control module comprises a comparison unit, a control unit and a voltage output unit; the voltage output unit is used for outputting the power supply voltage to the constant current source module according to a reference voltage; the comparison unit is used for comparing the voltage value of the dimming signal with the first preset voltage and the second preset voltage and outputting a corresponding level signal to the control unit according to a comparison result; and the control unit controls the voltage output unit to output the corresponding power supply voltage to the constant current source module according to the level signal.
4. The LED control circuit of claim 3, wherein the comparison unit comprises a first comparator and a second comparator; the positive phase input end of the first comparator is connected with the dimming signal input end, the negative phase input end of the first comparator is connected with the first preset comparison voltage input end, and the output end of the first comparator is connected with the control unit; the positive phase input end of the second comparator is connected with the dimming signal input end, the negative phase input end of the second comparator is connected with the second preset comparison voltage input end, and the output end of the second comparator is connected with the control unit.
5. The LED control circuit of claim 3, wherein the control unit comprises a first switch, a second resistor, and a third resistor; one end of the first switch is connected with the voltage output unit and one end of the first resistor, the other end of the first switch and the other end of the first resistor are connected with one end of the second switch and one end of the second resistor, and the other end of the second resistor and the other end of the second switch are connected with the voltage output unit; and the control end of the first switch and the control end of the second switch are both connected with the comparison unit.
6. The LED control circuit of claim 3, wherein the voltage output unit comprises a first operational amplifier, a first MOS transistor, a third resistor and a fourth resistor; the positive phase input end of the first operational amplifier is connected with a reference voltage input end, the negative phase input end of the first operational amplifier is connected with the control unit and one end of the fourth resistor, the output end of the first operational amplifier is connected with the grid electrode of the first MOS tube, the source electrode of the first MOS tube is connected with the other end of the fourth resistor and the constant current source module, and the drain electrode of the first MOS tube is connected with a line voltage input end; one end of the third resistor is connected with the control unit, and the other end of the third resistor is grounded.
7. The LED control circuit of claim 3, wherein the control module further comprises a filtering unit, and the filtering unit is configured to filter the dimming signal and output the filtered dimming signal to the comparing unit.
8. The LED control circuit of claim 7, wherein the filtering unit comprises a capacitor and a fifth resistor; one end of the capacitor is connected with one end of the fifth resistor and the comparison unit, and the other end of the capacitor is grounded; the other end of the fifth resistor is connected with a dimming signal input end.
9. A control method based on the LED control circuit according to any one of claims 1 to 8, comprising the steps of:
the control module outputs dimming voltage to the constant current source module according to an externally input dimming signal;
the constant current source module adjusts the working current of the LED lamp string according to the dimming voltage;
the control module is further used for comparing the voltage value of the dimming signal with at least one preset comparison voltage, outputting a corresponding power supply voltage to the constant current source module according to a comparison result, and controlling the difference value between the power supply voltage and the output voltage of the constant current source module.
10. An LED control device, comprising a housing, wherein a PCB is arranged in the housing, characterized in that the PCB is provided with an LED control circuit as claimed in any one of claims 1 to 8.
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| CN114158158A (en) * | 2021-11-02 | 2022-03-08 | 深圳市晟碟半导体有限公司 | Self-adaptive constant current control method and self-adaptive constant current circuit |
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| JP4938601B2 (en) * | 2007-09-11 | 2012-05-23 | セイコーＮｐｃ株式会社 | LED drive circuit |
| KR20110049519A (en) * | 2009-11-05 | 2011-05-12 | 삼성엘이디 주식회사 | Circuit for driving led and power supply for led comprising the same |
| CN202632722U (en) * | 2012-05-04 | 2012-12-26 | 福建捷联电子有限公司 | LED drive circuit |
| CN103024992A (en) * | 2012-11-13 | 2013-04-03 | 深圳麦格米特电气股份有限公司 | Dimming method of LED (Light Emitting Diode) streetlamp |
| CN204425733U (en) * | 2015-02-13 | 2015-06-24 | 浙江生辉照明有限公司 | For the supply power voltage regulating system of LED linear constant current circuit |
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| CN206164914U (en) * | 2016-10-13 | 2017-05-10 | 伊戈尔电气股份有限公司 | Linear constant current drive's LED light source prevent dark light circuit |
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| CN107846745A (en) * | 2017-10-11 | 2018-03-27 | 杭州士兰微电子股份有限公司 | LED drive circuit and its control method |
| CN108495419B (en) * | 2018-04-28 | 2024-05-14 | 深圳市晟碟半导体有限公司 | LED dimming circuit, dimming device and dimming method for reducing harmonic distortion |
| CN110831279A (en) * | 2019-10-25 | 2020-02-21 | 深圳市晟碟半导体有限公司 | LED driving device, driving circuit and driving method thereof |
| CN211509379U (en) * | 2020-02-28 | 2020-09-15 | 深圳市晟碟半导体有限公司 | LED control device and circuit |
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| CN114158158A (en) * | 2021-11-02 | 2022-03-08 | 深圳市晟碟半导体有限公司 | Self-adaptive constant current control method and self-adaptive constant current circuit |
| CN114158158B (en) * | 2021-11-02 | 2023-11-21 | 深圳市晟碟半导体有限公司 | Self-adaptive constant current control method and self-adaptive constant current circuit |
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