CN110831279A - LED driving device, driving circuit and driving method thereof - Google Patents
LED driving device, driving circuit and driving method thereof Download PDFInfo
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Abstract
The invention discloses an LED driving device, a driving circuit and a driving method thereof, wherein the LED driving circuit comprises a reference voltage output module, a control signal output module, a plurality of driving modules and switch modules corresponding to the driving modules; the control signal output module compares the dimming signal with the preset signal of each switch module respectively, and outputs a corresponding control signal to each switch module according to the comparison result so as to control each driving module to be switched on or switched off; the preset signals of the switch modules are decreased progressively according to the conducting sequence of the drive modules, and the preset signals of the switch modules are larger than the offset voltage signals of the drive modules connected with the switch modules, so that the problem that part of the light strings are lightened and part of the light strings are not lightened when the brightness is reduced is solved.
Description
Technical Field
The invention relates to the technical field of LEDs, in particular to an LED driving device, a driving circuit and a driving method thereof.
Background
Referring to fig. 1, the LED dimming is accomplished by changing the output of the reference voltage generating circuit by changing the dimming signal, and then controlling the output of the operational amplifier to adjust the current flowing through the string. In the multi-segment linear constant current dimming driving scheme, a reference voltage generating circuit generates and outputs a plurality of reference voltages according to a dimming signal, and then controls the output of a corresponding operational amplifier to adjust the current flowing through a corresponding string. In the process of reducing the brightness of the LED, when the dimming signal is reduced to a value which is not enough to turn on the MOS tubes below all the lamp strings, because the offset voltages of the operational amplifiers are inconsistent, partial MOS tubes cannot be turned off according to a preset sequence, and the problems that partial LED lamp beads are on and partial LED lamp beads are off are caused.
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, an object of the present invention is to provide an LED driving apparatus, a driving circuit and a driving method thereof, which solve the problem that during dimming of a string of lights, MOS transistors connected in series with the string of lights cannot be turned off in a predetermined sequence, so that part of the string of lights is lit and part of the string of lights is not lit.
In order to achieve the purpose, the invention adopts the following technical scheme:
an LED driving circuit comprises a reference voltage output module, a control signal output module, a plurality of driving modules and switch modules corresponding to the driving modules; the reference voltage output module outputs corresponding reference voltages to the driving modules through different taps after dividing dimming signals, and each driving module drives the corresponding lamp string to be sequentially turned on or turned off according to the line voltage and the corresponding reference voltage; the control signal output module compares the dimming signal with the preset signal of each switch module respectively and outputs corresponding control signals to each switch module through different taps according to the comparison result; each switch module controls each driving module to be switched on or switched off according to the corresponding control signal; the preset signals of the switch modules are decreased progressively according to the conduction sequence of the drive modules, and the preset signals of the switch modules are greater than the offset voltage signals of the drive modules connected with the switch modules.
In the LED driving circuit, the control signal output module comprises a plurality of comparators, the inverting input end of each comparator is connected with the dimming signal input end, the non-inverting input end of each comparator is connected with the preset signal input end, and the output end of each comparator is connected with each switch module.
In the LED driving circuit, the switch module comprises a switch tube, the first end of the switch tube is connected with the driving module, the second end of the switch tube is grounded, and the control end of the switch tube is connected with the control signal output module.
In the LED driving circuit, the control signal output module comprises an analog-to-digital converter and a plurality of comparators; the input end of the analog-to-digital converter is connected with the dimming signal input end, the output end of the analog-to-digital converter is respectively connected with the reverse phase input end of each comparator, the non-inverting input end of each comparator is respectively connected with the preset signal input end, and the output end of each comparator is respectively connected with each switch module.
The LED driving circuit further comprises a digital-to-analog conversion module, and the digital-to-analog conversion module performs digital-to-analog conversion on the dimming signal and outputs the dimming signal to the reference voltage output module.
In the LED driving circuit, the control signal output module comprises a duty ratio calculation unit and a plurality of comparators; the input end of the duty ratio calculation unit is connected with the dimming signal input end, the output end of the duty ratio calculation unit is respectively connected with the reverse phase input end of each comparator, the in-phase input end of each comparator is respectively connected with the preset signal input end, and the output end of each comparator is respectively connected with each switch module.
In the LED driving circuit, the reference voltage output module comprises a resistor string, the resistor string is formed by connecting a plurality of divider resistors in series, the upper end of the resistor string is connected with a dimming signal input end, the lower end of the resistor string is grounded, and an upper tap of each divider resistor is respectively LED out to be connected with each driving module.
In the LED driving circuit, the driving module comprises an operational amplifier and an MOS (metal oxide semiconductor) tube, the in-phase input end of the operational amplifier is connected with the reference voltage output module, the reverse-phase input end of the operational amplifier is grounded, the output end of the operational amplifier is connected with the grid electrode of the MOS tube and the first end of the switch tube, the drain electrode of the MOS tube is connected with the output end of the lamp string, and the source electrode of the MOS tube is grounded.
A driving method based on the LED driving circuit comprises the following steps:
the reference voltage output module outputs corresponding reference voltages to each driving module through different taps after dividing the dimming signal;
each driving module drives the corresponding lamp string to be sequentially lightened on or extinguished off according to the line voltage and the corresponding reference voltage;
the control signal output module compares the dimming signal with the preset signal of each switch module respectively and outputs corresponding control signals to each switch module through different taps according to the comparison result;
each switch module controls each driving module to be switched on or switched off according to the corresponding control signal; the preset signals of the switch modules are decreased progressively according to the conduction sequence of the drive modules, and the preset signals of the switch modules are greater than the offset voltage signals of the drive modules connected with the switch modules.
An LED driving device comprises the LED driving circuit.
Compared with the prior art, the invention provides an LED driving device, a driving circuit and a driving method thereof, wherein the LED driving circuit comprises a reference voltage output module, a control signal output module, a plurality of driving modules and switch modules corresponding to the driving modules; the control signal output module compares the dimming signal with the preset signal of each switch module respectively, and outputs a corresponding control signal to each switch module according to the comparison result so as to control each driving module to be switched on or switched off; the preset signals of the switch modules are decreased progressively according to the conducting sequence of the drive modules, and the preset signals of the switch modules are larger than the offset voltage signals of the drive modules connected with the switch modules, so that the problem that part of the light strings are lightened and part of the light strings are not lightened when the brightness is reduced is solved.
Drawings
Fig. 1 is a schematic circuit diagram of a conventional LED driving circuit;
FIG. 2 is a block diagram of an LED driving circuit according to the present invention;
FIG. 3 is a schematic circuit diagram of a first embodiment of an LED driving circuit according to the present invention;
FIG. 4 is a diagram showing the relationship between the line voltage, the dimming signal and the string current when three segments of LED driving circuits are lighted;
FIG. 5 is a diagram showing the relationship between the line voltage, the dimming signal and the string current when two segments of LED driving circuits are lighted;
FIG. 6 is a diagram showing the relationship between the line voltage, the dimming signal and the string current when a segment of the LED driving circuit is lit according to the present invention;
FIG. 7 is a schematic circuit diagram of a second embodiment of an LED driver circuit according to the present invention;
FIG. 8 is a schematic circuit diagram of a third embodiment of an LED driver circuit according to the present invention;
fig. 9 is a flowchart of a driving method of the LED driving circuit according to the present invention.
Detailed Description
In view of the defects of the prior art, the present invention aims to provide an LED driving apparatus, a driving circuit and a driving method thereof, which solve the problem that during dimming of a string of lights, MOS transistors connected in series with the string of lights cannot be turned off in a predetermined sequence, so that part of the string of lights is lit and part of the string of lights is not lit.
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 driving circuit provided by the present invention is connected to a plurality of strings including at least one LED lamp, the LED driving circuit includes a rectifying module 100, a reference voltage output module 200, a control signal output module 300, a plurality of driving modules 400, and a switching module 500 corresponding to the driving module 400, an input end of the rectifying module 100 is connected to an AC power supply AC, an output end of the rectifying module 100 is connected to an input end of a first string, the plurality of strings are connected in series, an output end of each string is connected to one driving module 400, and each driving module 400 is further connected to one switching module 500; the input end of the reference voltage output module 200 is connected to the dimming signal input end, the output end of the reference voltage output module 200 is connected to each of the driving modules 400, the input end of the control signal output module 300 is connected to the dimming signal input end, and the output end of the control signal output module 300 is connected to the switching module 500.
In the invention, the rectifier module 100 rectifies the alternating current and outputs a line voltage to the lamp strings to supply power to the lamp strings, the reference voltage output module 200 divides a dimming signal Vref and outputs corresponding reference voltages to the drive modules 400 through different taps, and the drive modules 400 drive the corresponding lamp strings to be sequentially turned on or turned off according to the line voltage and the corresponding reference voltages; the control signal output module 300 compares the dimming signal Vref with the preset signal of each switch module 500, and outputs a corresponding control signal to each switch module 500 through different taps according to the comparison result, specifically, when the dimming signal Vref is smaller than the preset signal, the control signal output module 300 outputs a control signal to control the switch module 500 to be turned on; each switch module 500 controls each driving module 400 to be turned on or off according to a corresponding control signal, in the dimming process of the light string, when the reference voltage is less than the offset voltage of the driving module 400, the driving module 400 is turned off, the corresponding light string is turned off, so that the influence of the offset voltage of each driving module 400 is avoided, and each driving module 400 can be ensured to be turned off according to a preset sequence, the preset signal of each switch module 500 is decreased progressively according to the turn-on sequence of each driving module 400, and the preset signal of the switch module 500 is greater than the offset voltage signal of the driving module 400 connected with the switch module 500, so that the problem that part of the light string is lighted and part of the light string is not lighted in the process of dimming the light string brightness is effectively avoided.
Please refer to fig. 3, the following embodiment explains the operating principle of the LED driving circuit by three-segment linear dimming driving, and the three driving modules and the three switching modules corresponding to the three driving modules are respectively the first driving module 401, the second driving module 402, the third driving module 403, the first switching module 501, the second switching module 502, and the third switching module 503, and can be adjusted as needed in other embodiments. According to the invention, the switch modules are additionally arranged below each driving module and are uniformly managed by the control signal output module 300, so that when the brightness of the light string is reduced, the driving modules can be effectively controlled to stop driving according to a preset sequence, and the problem that part of the light string is lightened but part of the light string is not lightened is avoided.
During specific implementation, reference voltage output module 200 includes the resistor string, the resistor string comprises a plurality of divider resistor series connection, dimming signal input part is connected to the upper end of resistor string, the lower extreme ground connection of resistor string, the upper end tap of every divider resistor draw respectively with each drive module connects, through reference voltage output module 200 is each drive module provides corresponding reference voltage, so that the lamp cluster that the drive module drive corresponds lights.
In this embodiment, the resistor string includes three voltage dividing resistors, namely, a first resistor Ra1, a second resistor Ra2 and a third resistor Ra3, an upper end tap of the first resistor Ra1 is connected to the first driving module 401, an upper end tap of the second resistor Ra2 is connected to the second driving module 402, an upper end tap of the third resistor Ra3 is connected to the third driving module 403, and according to the voltage dividing effects of the first resistor Ra1, the second resistor Ra2 and the third resistor Ra3, a first reference voltage Vref1, a second reference voltage Vref2 and a third reference voltage Vref3 are respectively provided for the first driving module 401, the second driving module 402 and the third driving module 403, so that the first driving module 401, the second driving module 402 and the third driving module 403 drive the corresponding light string to be lit, wherein,
Vref1＝(Ra1*Vref)/(Ra1+Ra2+Ra3)；
Vref2＝((Ra1+Ra2)*Vref)/(Ra1+Ra2+Ra3)；
Vref3＝Vref。
further, please refer to fig. 3, in the first embodiment of the present invention, the preset signal of the switch module is a preset threshold voltage of the switch module, the offset voltage signal of the driving module is an analog voltage value, which is referred to as offset voltage for short, the control signal output module 300 includes a plurality of comparators, an inverting input terminal of each comparator is connected to a dimming signal input terminal, a non-inverting input terminal of each comparator is connected to a preset threshold voltage input terminal, an output terminal of each comparator is connected to each switch module, when the dimming signal Vref compared by each comparator is smaller than the preset threshold voltage of each switch module, the corresponding control signal is output to the switch module to control the corresponding switch module to be turned on, so that the corresponding driving module is turned off, and in order to ensure that each driving module can be turned off according to a preset sequence, the influence of offset voltage of the driving modules is eliminated, the preset threshold voltage of each switch module is decreased progressively according to the conducting sequence of each driving module, and the preset threshold voltage of the switch module is greater than the offset voltage of the driving module connected with the switch module, so that the problem that part of the light strings are lighted but part of the light strings are not lighted when the brightness of the light strings is reduced is avoided.
Specifically, in this embodiment, the control signal output module 300 includes three comparators, which are respectively a first comparator COMP1, a second comparator COMP2 and a third comparator COMP3, where the first comparator COMP1, the second comparator COMP2 and the third comparator COMP3 respectively compare the dimming signal Vref with a preset threshold voltage Vth1 of the first switch module 501, a preset threshold voltage Vth2 of the second switch module 502 and a preset threshold voltage Vth3 of the third switch module 503, and when the dimming signal Vref is smaller than the corresponding preset threshold voltage, the three comparators respectively provide control signals Vctr1, Vctr2 and Vctr3 for the first switch module 501, the second switch module 502 and the third switch module 503, so as to control the conduction of the switch modules.
When the dimming signal Vref changes, the first reference voltage Vref1, the second reference voltage Vref2 and the third reference voltage Vref3 change, the current flowing through the light string correspondingly changes, the brightness of the light string also changes, as the line voltage rises, the first driving module 401, the second driving module 402 and the third driving module 403 are sequentially turned on, the current flows through the corresponding light strings in sequence, and the light strings are sequentially turned on; with the line voltage decreasing, the third driving module 403, the second driving module 402 and the first driving module 401 are sequentially turned off, no current flows through the strings in sequence, and the strings are sequentially turned off, and at this time, the relationship between the dimming signal in the LED driving circuit, the line voltage and the string current is as shown in fig. 4. When the reference voltage of each driving module is smaller than the offset voltage of the driving module, the driving module is disconnected, and no current flows through the lamp string. For the performance consideration of power supply efficiency, harmonic waves, light effect and the like, the optimal scheme is that the first driving module 401 is firstly disconnected along with the reduction of the dimming signal Vref, and at the moment, the light string corresponding to the first driving module is connected in series with the light string corresponding to the second driving module and is controlled by the second driving module; when the dimming signal Vref continues to decrease, the second driving module 402 is disconnected, and at this time, the light strings corresponding to the first driving module and the second driving module are connected in series with the light strings corresponding to the third driving module and controlled by the third driving module; finally, when the dimming signal Vref is lowered to a value that the string current is not enough to normally light the strings, the third driving module 403 is turned off, no current flows through all strings, and the strings are extinguished. To realize this turn-off sequence, it is necessary to satisfy the relationship of (Vref3-Voffset3) > (Vref2-Voffset2) > (Vref1-Voffset1), where Voffset1, Voffset2, and Voffset3 correspond to the offset voltages of the first driving module 401, the second driving module 402, and the third driving module 403, and the offset voltages may be positive values or negative values; when the offset voltages are different and cannot satisfy the relationship (Vref3-Voffset3) > (Vref2-Voffset2) > (Vref1-Voffset1), the turn-off sequence of the first driving module 401, the second driving module 402 and the third driving module 403 will be disordered, and the problems that part of the lamps are on and part of the lamps are off are caused.
When the dimming signal Vref is lowered to only turn on two of the first driving module 401, the second driving module 402 and the third driving module 403, preferably turn on the second driving module 402 and the third driving module 403, turn off the first driving module 401, and at this time, the string is combined from three segments into two segments to be lit, and at this time, the relationship between the dimming signal, the line voltage and the string current in the LED driving circuit is as shown in fig. 5. Considering the difference of the offset voltages of the driving modules, it may cause different results of turning on the second driving module 402 and the first driving module 401, turning off the third driving module 403, or turning on the third driving module 403 and the first driving module 401, and turning off the second driving module 402. The second driving module 402 and the first driving module 401 are turned on, and the third driving module 403 is turned off, so that the light strings connected in series to the third driving module 403 are in a light-out state, and the light strings connected in series to the first driving module 401 and the second driving module 402 are in a lighting state, that is, a problem that part of the light strings are on and part of the light strings are not on occurs.
When the dimming signal Vref is lowered to only one of the first driving module 401, the second driving module 402 and the third driving module 403, the third driving module 403 is preferably turned on, the first driving module 401 and the second driving module 402 are turned off, and at this time, the light string is combined from three segments into a whole segment to be lighted, and at this time, the relationship between the dimming signal, the line voltage and the light string current in the LED driving circuit is as shown in fig. 6. Considering the difference of the offset voltages of the driving modules, different results of turning on the second driving module 402, turning off the first driving module 401 and the third driving module 403, or turning on the first driving module 401, turning off the second driving module 402 and the third driving module 403 may be caused. Turning on the second driving module 402, turning off the first driving module 401 and the third driving module 403, so that the light string connected in series to the third driving module 403 is in a light-off state, and the light string connected in series to the first driving module 401 and the second driving module 402 is in a light-on state; turning on the first driving module 401, and turning off the second driving module 402 and the third driving module 403, causes the light strings connected in series to the second driving module 402 and the third driving module 403 to be in a light-off state, and causes the light strings connected in series to the first driving module 401 to be in a light-on state. In both cases, a problem that some lamps are lit and some lamps are not lit occurs, so in order to eliminate the influence caused by the difference of the offset voltages of the driving modules and satisfy the sequence of the disconnection of the first driving module 401, the second driving module 402 and the third driving module 403, the preset threshold voltages Vth1, Vth2 and Vth3 should satisfy the following conditions:
Vth1>Vth2>Vth3；
Vth3>Voffset3；
Vth2>Voffset2；
Vth1>Voffset1。
further, the switch module includes a switch tube, a first end of the switch tube is connected to the driving module, a second end of the switch tube is grounded, a control end of the switch tube is connected to the control signal output module 300, each driving module and the ground are connected to the switch tube, a threshold voltage of each switch tube is set by evaluating the magnitude of an offset voltage of each driving module, when the offset voltage is not affected, one or more of the switch tubes are turned on in advance to correspondingly turn off one or more of the driving modules, and further, the influence caused by the offset voltage is eliminated; the switching tubes K1, K2 and K3 correspond to the switching tubes of the first switching module 501, the second switching module 502 and the third switching module 503, respectively.
Further, the driving module includes an operational amplifier and an MOS transistor, the non-inverting input terminal of the operational amplifier is connected to the reference voltage output module 200, the inverting input terminal of the operational amplifier is grounded, the output terminal of the operational amplifier is connected to the gate of the MOS transistor and the first end of the switching transistor, the drain of the MOS transistor is connected to the output terminal of the light string, the source of the MOS transistor is grounded, each driving module has the same structure, and includes an operational amplifier and an MOS transistor, the offset voltage corresponding to each driving module is the offset voltage of the operational amplifier, the operational amplifier controls the on/off of the MOS transistor according to the magnitude of the reference voltage and the offset voltage, the switching transistor is connected between the gate of the MOS transistor and the ground in the process of dimming the brightness of the light string to avoid the influence of the offset voltage, and further controls the off of the MOS transistor according to the control signal output module 300 through the switching transistor, so that each MOS tube can be disconnected according to a preset sequence. The MOS transistors Q1, Q2, and Q3 correspond to MOS transistors in the first driving module 401, the second driving module 402, and the third driving module 403, respectively, and the first driving module 401, the second driving module 402, and the third driving module 403 are turned on and off, that is, the MOS transistors Q1, Q2, and Q3 are turned on and off.
Furthermore, the LED driving circuit further includes a constant current resistor Rcs, one end of the constant current resistor Rcs is connected to the source of each MOS transistor, the other end of the constant current resistor Rcs is grounded, and the current flowing through the string of lights is set by the constant current resistor Rcs.
In a second embodiment of the present invention, please refer to fig. 7, the control signal output module 300 includes an analog-to-digital converter ADC and a plurality of comparators; the input end of the analog-to-digital converter ADC is connected to the dimming signal input end, the output end of the analog-to-digital converter ADC is respectively connected to the inverting input ends of the comparators, in this embodiment, the preset signal of the switch module is the preset threshold value of the switch module, the offset voltage signal of the driving module is a data value, furthermore, the non-inverting input end of each comparator is respectively connected with the input end of a preset threshold value, the output end of each comparator is respectively connected with each switch module, the analog-to-digital converter ADC outputs a group of dimming data values to the comparator after sampling the dimming signal Vref, and the comparator compares the group of dimming data with a preset threshold value 1, a preset threshold value 2 and a preset threshold value 3 and outputs control signals Vctr1, Vctr2 and Vctr3 to respectively control the switching-on and switching-off of the switching tubes K1, K2 and K3 so as to control the switching-off and switching-on of the driving modules. In this embodiment, when the dimming data is greater than the preset threshold, the corresponding control signals are output to respectively disconnect the corresponding switch modules, the driving module is switched on, and the corresponding light strings have current flowing through, so that the light strings are lighted; when the dimming data is smaller than the preset threshold value, the corresponding control signals are output to respectively conduct the corresponding switch modules, the driving module is disconnected, no current flows through the corresponding lamp strings, and the lamp strings are extinguished. The preset threshold value 1, the threshold value 2 and the threshold value 3 satisfy the following relations:
threshold 1> threshold 2> threshold 3;
threshold value 1> data value 1.
Wherein, the data value 3 is obtained after the analog-to-digital converter samples the offset voltage Voffset3, the data value 2 is obtained after the analog-to-digital converter samples the offset voltage Voffset2, and the data value 1 is obtained after the analog-to-digital converter samples the offset voltage Voffset 1; the preset threshold values respectively determine when the switch modules are switched off or switched on, so that MOS (metal oxide semiconductor) tubes Q1, Q2 and Q3 below the lamp string are controlled, the influence caused by the offset voltage of the operational amplifier in each driving module is eliminated, the MOS tubes are controlled to be switched off according to the preset sequence, and the problem that part of the lamp string is lightened but part of the lamp string is not lightened when the brightness of the lamp string is reduced is solved.
In a third embodiment of the present invention, referring to fig. 8, the LED driving circuit further includes a digital-to-analog conversion module 600, the digital-to-analog conversion module 600 converts the digital dimming signal into an analog dimming signal and outputs the analog dimming signal to the reference voltage output module 200, and when the digital dimming signal is a PWM dimming signal, a duty ratio of the PWM dimming signal is proportional to a magnitude of a current flowing through the string. One of the PWM dimming signals is input to the digital-to-analog conversion module 600, and the digital-to-analog conversion module 600 converts the digital PWM dimming signal into an analog dimming signal; the other path of the PWM dimming signal is input to the control signal output module 300, and the control signal output module 300 controls the on/off of each MOS transistor according to the PWM dimming signal, so as to realize the orderly off of each MOS transistor; in this embodiment, the digital-to-analog conversion module 600 includes a digital-to-analog converter.
Further, the control signal output module 300 in this embodiment includes a duty ratio calculating unit 310 and several comparators; the input end of the duty ratio calculating unit 310 is connected to the dimming signal input end, the output end of the duty ratio calculating unit 310 is connected to the inverting input end of each comparator, similarly, in this embodiment, the preset signal of the switch module is the preset threshold value of the switch module, the offset voltage signal of the driving module is a data value, the non-inverting input end of each comparator is connected to the preset threshold voltage input end, the output end of each comparator is connected to the control end of each switch tube, the duty ratio calculating unit 310 counts the high level and the low level width of the PWM signal, the duty ratio value of the PWM signal is calculated according to the width values of the high level and the low level of the PWM signal to obtain the dimming data value, the dimming data value is compared with the preset threshold value 1, the threshold value 2 and the threshold value 3 by the comparator, and then the control signal Vctr1 is output, Vctr2 and Vctr3 control the on/off of the switching tubes K1, K2 and K3, and further control the on/off of each driving module. In this embodiment, when the dimming data value is greater than the preset threshold value, the corresponding control signals are output to respectively disconnect the corresponding switch modules, the driving module is switched on, and the corresponding light strings have current flowing through, so that the light strings are lighted; when the dimming data is smaller than the preset threshold value, outputting corresponding control signals to respectively conduct the corresponding switch modules, disconnecting the driving modules, enabling no current to flow through the corresponding lamp strings, and extinguishing the lamp strings; the duty ratio calculating unit in this embodiment may be a counter.
Correspondingly, the preset threshold value 1, the threshold value 2 and the threshold value 3 in this embodiment satisfy the following relationship:
threshold 1> threshold 2> threshold 3;
threshold value 1> data value 4.
Wherein, the data value 6 is the data value corresponding to the duty ratio value of the PWM signal when Voffset3 equals to Vref 3; data value 5 is the data value corresponding to the duty cycle value of the PWM signal when Voffset2 equals Vref 2; data value 4 is the data value corresponding to the duty cycle value of the PWM signal when Voffset1 equals Vref 1; the preset threshold value determines when the corresponding switch module is disconnected and opened, and then the MOS tubes Q1, Q2 and Q3 below the light string are controlled, so that the MOS tubes are controlled to be disconnected according to a preset sequence, and the problem that part of the light string is lightened but part of the light string is not lightened in the process of reducing the brightness of the light string is effectively avoided.
The present invention also provides a driving method of an LED driving circuit, referring to fig. 9, the driving method of the LED driving circuit includes the following steps:
s100, the reference voltage output module divides the voltage of the dimming signal and outputs corresponding reference voltages to the driving modules through different taps;
s200, the reference voltage output module divides the voltage of the dimming signal and outputs corresponding reference voltages to the driving modules through different taps;
s300, the control signal output module compares the dimming signal with the preset signal of each switch module respectively, and outputs the corresponding control signal to each switch module through different taps according to the comparison result;
s400, each switch module controls each driving module to be turned on or turned off according to the corresponding control signal; the preset signals of the switch modules are decreased progressively according to the conduction sequence of the drive modules, and the preset signals of the switch modules are greater than the offset voltage signals of the drive modules connected with the switch modules.
Based on the LED driving circuit, the invention also provides a corresponding LED driving apparatus, which is not described herein again because the LED driving circuit is described above in detail.
In summary, the present invention provides an LED driving apparatus, a driving circuit and a driving method thereof, where the LED driving circuit includes a reference voltage output module, a control signal output module, a plurality of driving modules and a switch module corresponding thereto, the reference voltage output module outputs a corresponding reference voltage to each driving module according to a dimming signal, and each driving module drives a corresponding light string to turn on or off in sequence according to a line voltage and the corresponding reference voltage; the control signal output module compares the dimming signal with the preset signal of each switch module respectively, and outputs a corresponding control signal to each switch module according to the comparison result so as to control each driving module to be switched on or switched off; the preset signals of the switch modules are decreased progressively according to the conducting sequence of the drive modules, and the preset signals of the switch modules are larger than the offset voltage signals of the drive modules connected with the switch modules, so that the problem that part of the light strings are lightened and part of the light strings are not lightened when the brightness is reduced is solved.
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 drive circuit is characterized by comprising a reference voltage output module, a control signal output module, a plurality of drive modules and a switch module corresponding to the drive modules; the reference voltage output module outputs corresponding reference voltages to the driving modules through different taps after dividing dimming signals, and each driving module drives the corresponding lamp string to be sequentially turned on or turned off according to the line voltage and the corresponding reference voltage; the control signal output module compares the dimming signal with the preset signal of each switch module respectively and outputs corresponding control signals to each switch module through different taps according to the comparison result; each switch module controls each driving module to be switched on or switched off according to the corresponding control signal; the preset signals of the switch modules are decreased progressively according to the conduction sequence of the drive modules, and the preset signals of the switch modules are greater than the offset voltage signals of the drive modules connected with the switch modules.
2. The LED driving circuit according to claim 1, wherein the control signal output module comprises a plurality of comparators, an inverting input terminal of each comparator is connected to the dimming signal input terminal, a non-inverting input terminal of each comparator is connected to the preset signal input terminal, and an output terminal of each comparator is connected to each switch module.
3. The LED driving circuit according to claim 1, wherein the switch module comprises a switch tube, a first end of the switch tube is connected to the driving module, a second end of the switch tube is grounded, and a control end of the switch tube is connected to the control signal output module.
4. The LED driving circuit according to claim 1, wherein the control signal output module comprises an analog-to-digital converter and a plurality of comparators; the input end of the analog-to-digital converter is connected with the dimming signal input end, the output end of the analog-to-digital converter is respectively connected with the reverse phase input end of each comparator, the non-inverting input end of each comparator is respectively connected with the preset signal input end, and the output end of each comparator is respectively connected with each switch module.
5. The LED driving circuit according to claim 1, further comprising a digital-to-analog conversion module, wherein the digital-to-analog conversion module converts a digital dimming signal into an analog dimming signal and outputs the analog dimming signal to the reference voltage output module.
6. The LED driving circuit according to claim 5, wherein the control signal output module comprises a duty ratio calculation unit and a plurality of comparators; the input end of the duty ratio calculation unit is connected with the dimming signal input end, the output end of the duty ratio calculation unit is respectively connected with the reverse phase input end of each comparator, the in-phase input end of each comparator is respectively connected with the preset signal input end, and the output end of each comparator is respectively connected with each switch module.
7. The LED driving circuit according to claim 1, wherein the reference voltage output module comprises a resistor string, the resistor string is formed by connecting a plurality of voltage dividing resistors in series, an upper end of the resistor string is connected to the dimming signal input end, a lower end of the resistor string is grounded, and an upper end tap of each voltage dividing resistor is respectively LED out to be connected with each driving module.
8. The LED driving circuit according to claim 3, wherein the driving module comprises an operational amplifier and an MOS transistor, a non-inverting input terminal of the operational amplifier is connected to the reference voltage output module, a non-inverting input terminal of the operational amplifier is grounded, an output terminal of the operational amplifier is connected to a gate of the MOS transistor and the first terminal of the switching transistor, a drain of the MOS transistor is connected to the output terminal of the light string, and a source of the MOS transistor is grounded.
9. A driving method based on the LED driving circuit according to any one of claims 1 to 8, comprising the steps of:
the reference voltage output module outputs corresponding reference voltages to each driving module through different taps after dividing the dimming signal;
each driving module drives the corresponding lamp string to be sequentially lightened on or extinguished off according to the line voltage and the corresponding reference voltage;
the control signal output module compares the dimming signal with the preset signal of each switch module respectively and outputs corresponding control signals to each switch module through different taps according to the comparison result;
each switch module controls each driving module to be switched on or switched off according to the corresponding control signal; the preset signals of the switch modules are decreased progressively according to the conduction sequence of the drive modules, and the preset signals of the switch modules are greater than the offset voltage signals of the drive modules connected with the switch modules.
10. An LED driving apparatus comprising the LED driving circuit according to any one of claims 1 to 8.
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| CN201911022689.7A CN110831279A (en) | 2019-10-25 | 2019-10-25 | LED driving device, driving circuit and driving method thereof |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112669767A (en) * | 2020-12-28 | 2021-04-16 | 深圳创维－Rgb电子有限公司 | Mini LED driving system and driving method thereof |
| CN113160761A (en) * | 2021-04-20 | 2021-07-23 | 惠州市华星光电技术有限公司 | Driving method, driving circuit and display device |
| CN114173445A (en) * | 2021-11-29 | 2022-03-11 | 四维生态科技（杭州）有限公司 | Spectrum adjusting system and method based on voltage modulation |
| CN111200892B (en) * | 2020-02-28 | 2023-08-29 | 深圳市晟碟半导体有限公司 | LED control device, circuit and control method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111200892B (en) * | 2020-02-28 | 2023-08-29 | 深圳市晟碟半导体有限公司 | LED control device, circuit and control method thereof |
| CN112669767A (en) * | 2020-12-28 | 2021-04-16 | 深圳创维－Rgb电子有限公司 | Mini LED driving system and driving method thereof |
| CN113160761A (en) * | 2021-04-20 | 2021-07-23 | 惠州市华星光电技术有限公司 | Driving method, driving circuit and display device |
| US11682356B2 (en) | 2021-04-20 | 2023-06-20 | Huizhou China Star Optoelectronics Display Co., Ltd. | Driving method, driving circuit, and display device |
| CN113160761B (en) * | 2021-04-20 | 2023-10-03 | 惠州市华星光电技术有限公司 | Driving method, driving circuit and display device |
| CN114173445A (en) * | 2021-11-29 | 2022-03-11 | 四维生态科技（杭州）有限公司 | Spectrum adjusting system and method based on voltage modulation |
| CN114173445B (en) * | 2021-11-29 | 2023-12-22 | 四维生态科技（杭州）有限公司 | Spectrum adjusting system and method based on voltage modulation |
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