CN104075135A - Driving system and method for light emitting diodes - Google Patents
Driving system and method for light emitting diodes Download PDFInfo
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- CN104075135A CN104075135A CN201310095829.XA CN201310095829A CN104075135A CN 104075135 A CN104075135 A CN 104075135A CN 201310095829 A CN201310095829 A CN 201310095829A CN 104075135 A CN104075135 A CN 104075135A
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Abstract
The invention discloses a driving system for light emitting diodes. The driving system comprises a direct current/direct current converter, a current adjusting unit, a control unit and a pulse width modulating controller. The direct current/direct current converter is used for converting input voltage of an external power supply to driving voltage. The control unit is used for generating and outputting control signals to the pulse width modulating controller and outputting a plurality of current adjusting signals. The current adjusting unit is used for adjusting current flowing through all light emitting diode strings according to current adjusting signals of all the light emitting diode strings. The pulse width modulating controller is used for outputting pulse width modulating signals according to the control signals. The invention further provides a driving method for the light emitting diodes. The driving system and method for the light emitting diodes perform the quick adjustment on the driving voltage of light emitting diode arrays according to the present current of the light emitting diode arrays in real time, modify the heat stress problem of an electronic switch caused by the power loss, and improve the use efficiency of a power supply.
Description
Technical field
The present invention relates to a kind of backlight drive system, relate in particular to a kind of LED drive system and method for display device.
Background technology
Light emitting diode (light emitting diode, LED) is because of power and energy saving, and is more and more applied in the backlight of display device.For ensureing the display effect of display device, need uniform light source as the LED of backlight, therefore need in LED drive system, add the electronic switch of balanced balanced current, be connected in each LED string.Conventionally, traditional LED drive system must meet the highest LED string of pressure drop enough forward voltage, to reach the electric current of setting.But, because the different characteristic of LED causes under identical direct voltage drive, the pressure drop difference of every a string LED, and for 3 D stereo LED TV, because the electric current of two-dimensional model is different with the electric current of three dimensional pattern, electronic switch can produce larger power attenuation like this, and causes thermal stress issues, and can reduce power supply service efficiency.
Summary of the invention
In view of this, need provide a kind of LED drive system, can improve thermal stress issues, improve power supply service efficiency.
In addition, also need to provide a kind of LED driving method, can improve thermal stress issues, improve power supply service efficiency.
The LED driving method providing in present embodiment, for LED drive system, be used for driving light emitting diode matrix, described light emitting diode matrix comprises the light-emitting diodes pipe string of multiple parallel connections, described LED drive system comprises control module, Pwm controller, and described control module comprises constant current unit, the first comparing unit, judging unit, signal generation unit.Described LED driving method comprises: the flow through electric current of described multiple light-emitting diodes pipe strings according to the current regulating signal of the described multiple light-emitting diodes pipe strings of the corresponding output of the electric current of described multiple light-emitting diodes pipe strings of described constant current unit detecting; The current regulating signal of the described multiple light-emitting diodes pipe strings of described the first comparing unit detecting is also therefrom found out maximum; Described judging unit judges whether the maximum of described current regulating signal is also exported and judged signal between the first setting value and the second setting value; Described signal generation unit produces and exports control signal according to described judgement signal; Described Pwm controller is according to described control signal output pulse width modulation signal, to drive described light emitting diode matrix.
Preferably, described signal generation unit comprises according to the described step that judges that signal produces and export control signal: judge if described signal be the maximum of described current regulating signal between the first setting value and the second setting value, described signal generation unit produces and the constant control signal of output duty cycle; Judge that if described signal is that the maximum of described current regulating signal is greater than described the second setting value, the control signal that described signal generation unit produces and output duty cycle increases; Judge that if described signal is that the maximum of described current regulating signal is less than described the first setting value, the control signal that described signal generation unit produces and output duty cycle reduces.
Preferably, described Pwm controller is according to described control signal output pulse width modulation signal, comprise taking the step that drives described light emitting diode matrix: if the control signal that described control signal increases as dutycycle, described Pwm controller judges whether output duty cycle is greater than threshold value; If described Pwm controller output duty cycle is greater than threshold value, the pulse width modulating signal that output duty cycle reduces; If described Pwm controller output duty cycle is not more than threshold value, the pulse width modulating signal that output duty cycle increases.
Preferably, described control module also comprises dynamic reference level adjustment unit, the second comparing unit, the 3rd comparing unit, the flow through electric current of described multiple light-emitting diodes pipe strings comprising according to the step of the current regulating signal of the described multiple light-emitting diodes pipe strings of the corresponding output of the electric current of described multiple light-emitting diodes pipe strings of described constant current unit detecting: the dividing potential drop of the described multiple light-emitting diodes pipe string negative electrodes of described the second comparing unit detecting is also therefrom found out minimum of a value.
Preferably, described signal generation unit comprises according to the described step that judges that signal produces and export control signal: described the 3rd comparing unit judges whether the minimum of a value of the negative electrode dividing potential drop of described multiple light-emitting diodes pipe strings is greater than the reference level voltage of described dynamic reference level adjustment unit output; If the minimum of a value of the negative electrode dividing potential drop of described multiple light-emitting diodes pipe strings is greater than described with reference to level voltage, described judging unit output is with reference to the constant extremely described dynamic reference level adjustment unit of adjustment signal of level voltage, and described signal generation unit produces and the constant control signal of output duty cycle; If the minimum of a value of the negative electrode dividing potential drop of described multiple light-emitting diodes pipe strings be not more than described with reference to level voltage and described judge signal be described current regulating signal maximum the first setting value and second setting value between, described judging unit output is with reference to the constant extremely described dynamic reference level adjustment unit of adjustment signal of level voltage, and described signal generation unit produces and the constant control signal of output duty cycle; If the minimum of a value of the negative electrode dividing potential drop of described multiple light-emitting diodes pipe strings is not more than described with reference to level voltage and describedly judge that signal is that the maximum of described current regulating signal is greater than described the second setting value, the adjustment signal that described judging unit output increases with reference to level voltage is to described dynamic reference level adjustment unit, and described signal generation unit produces the control signal that also output duty cycle increases;
If the minimum of a value of the negative electrode dividing potential drop of described multiple light-emitting diodes pipe strings is not more than described with reference to level voltage and describedly judge that signal is that the maximum of described current regulating signal is less than described the first setting value, described judging unit is exported the adjustment signal reducing with reference to level voltage to described dynamic reference level adjustment unit, the control signal that described signal generation unit produces and output duty cycle reduces.
The LED drive system providing in present embodiment, for outer power voltage being converted to the voltage that is applicable to driving light emitting diode matrix work, described light emitting diode matrix comprises the light-emitting diodes pipe string of multiple parallel connections, and described LED drive system comprises DC-DC converter, control module and Pwm controller.Described DC-DC converter is used for being electrically connected described external power source and described light emitting diode matrix, for the input voltage of described external power source is converted to driving voltage, to drive described light emitting diode matrix luminous.Described control module is used for being electrically connected described light emitting diode matrix, comprises constant current unit, the first comparing unit, judging unit and signal generation unit.Described constant current unit is for detecting the electric current of described each the light-emitting diodes pipe string of flowing through, to obtain the current regulating signal of each light-emitting diode pipe string.Whether described judging unit is used for the maximum of the current regulating signal that judges described multiple light-emitting diodes pipe strings and between the first setting value and the second setting value, also exports and judge signal.Described signal generation unit is for producing and export control signal according to described judgement signal.Described Pwm controller is used for being electrically connected described control module and described DC-DC converter, for according to described control signal output pulse width modulation signal, to regulate the driving voltage of output of described DC-DC converter.
Preferably, described LED drive system also comprises current regulation unit, for being electrically connected between the negative electrode and described control module of described light emitting diode matrix, described constant current unit is also for detect the electric current of described each the light-emitting diodes pipe string of flowing through by described current regulation unit, to obtain the current regulating signal of each light-emitting diode pipe string.
Preferably, described current regulation unit is also for regulating the electric current of described each the light-emitting diodes pipe string of flowing through according to the current regulating signal of described each light-emitting diode pipe string.
Preferably, described signal generation unit is also for the maximum of the current regulating signal at described multiple light-emitting diodes pipe strings between described the first setting value sets value with described second time, produce and the constant control signal of output duty cycle, in the time that the maximum of the current regulating signal of described multiple light-emitting diodes pipe strings is less than described the first setting value, produce the control signal that also output duty cycle reduces, and in the time that the maximum of the current regulating signal of described multiple light-emitting diodes pipe strings is greater than described the second setting value, produce the described Pwm controller that controls signal to of also output duty cycle increase, to adjust the dutycycle of described pulse width modulating signal.
Preferably, described Pwm controller is also for judging whether described output pulse width modulation signal is greater than threshold value, in the time being not more than threshold value, and the pulse width modulating signal that output duty cycle increases, and in the time being greater than threshold value, the pulse width modulating signal that output duty cycle reduces.
Preferably, described control module also comprises dynamic reference level adjustment unit, the second comparing unit, the 3rd comparing unit.Described dynamic reference level adjustment unit is for adjusting with reference to level voltage according to the judgement signal of described judging unit output.Described the second comparing unit is for the negative electrode dividing potential drop of more described multiple light-emitting diodes pipe strings, to obtain the minimum of a value of negative electrode dividing potential drop of described multiple light-emitting diodes pipe strings.Described the 3rd comparing unit, for the minimum of a value of the negative electrode dividing potential drop of more described multiple light-emitting diodes pipe strings and described with reference to level voltage, produces and exports control signal to control described signal generation unit.
Preferably, described judging unit is greater than described during with reference to level voltage in the minimum of a value of the negative electrode dividing potential drop of described multiple light-emitting diodes pipe strings, produce and export the judgement signal extremely described dynamic reference level adjustment unit constant with reference to level voltage, what described signal generation unit generation output duty cycle were constant controls signal to described Pwm controller, and described judging unit is not more than described during with reference to level voltage in the minimum of a value of the negative electrode dividing potential drop of described multiple light-emitting diodes pipe strings, and the maximum of the current regulating signal of described multiple light-emitting diodes pipe strings is in the time that described first sets value between described the second setting value, produce and export the judgement signal extremely described dynamic reference level adjustment unit constant with reference to level voltage, what described signal generation unit generation output duty cycle were constant controls signal to described Pwm controller.
Preferably, described judging unit is not more than described during with reference to level voltage in the minimum of a value of the negative electrode dividing potential drop of described multiple light-emitting diodes pipe strings, and when the maximum of the current regulating signal of described multiple light-emitting diodes pipe strings is less than described the first setting value, produce and export the judgement signal reducing with reference to level voltage to described dynamic reference level adjustment unit, described with reference to level voltage to adjust, what described signal generation unit produced and output duty cycle reduces controls signal to described Pwm controller, to adjust the dutycycle of described pulse width modulating signal.
Preferably, described judging unit is not more than described during with reference to level voltage in the minimum of a value of the negative electrode dividing potential drop of described multiple light-emitting diodes pipe strings, and when the maximum of the current regulating signal of described multiple light-emitting diodes pipe strings is greater than described the second setting value, produce and export the judgement signal increasing with reference to level voltage to described dynamic reference level adjustment unit, described with reference to level voltage to adjust, described signal generation unit produces the described Pwm controller that controls signal to of also output duty cycle increase, to adjust the dutycycle of described pulse width modulating signal.
Preferably, described current regulation unit comprises electronic switch, the sampling resistor with the corresponding connection of each light-emitting diodes pipe string, described electronic switch comprises controls the utmost point, the first electrode, the second electrode, described the first electrode is connected with described light-emitting diodes pipe string cathodic electricity, the described control utmost point and described constant current unit are electrically connected, described the second electrode and described sampling resistor one end are electrically connected, described sampling resistor other end ground connection.
Preferably, the electric current of described current regulating signal and the described light-emitting diodes pipe string functional relation that is inversely proportional to.
Preferably, described LED drive system also comprises feedback unit, be used for being electrically connected at described DC-DC converter and described Pwm controller, for producing according to the driving voltage of described DC-DC converter output and extremely described Pwm controller of output feedback signal, to adjust the dutycycle of described pulse width modulating signal.
Preferably, described feedback unit comprises the first divider resistance, the second divider resistance.The output of described first divider resistance one end and described DC-DC converter is electrically connected, and the other end and Pwm controller are electrically connected.Described the second divider resistance, the other end of one end and the first divider resistance is electrically connected, other end ground connection.
Above-mentioned LED drive system and method are carried out light emitting diode matrix driving voltage rapid adjustment according to the electric current of current light-emitting diodes array in real time, improve the thermal stress issues that electronic switch causes because of power attenuation, improved power supply service efficiency simultaneously.
Brief description of the drawings
Fig. 1 is the module map of LED drive system in an embodiment of the present invention.
Fig. 2 is the circuit diagram of LED drive system in an embodiment of the present invention.
Fig. 3 is the circuit diagram of LED drive system in another embodiment of the present invention.
Fig. 4 is the circuit diagram of LED drive system in the another embodiment of the present invention.
Fig. 5 is the flow chart of LED driving method in an embodiment of the present invention.
Fig. 6 is the flow chart of LED driving method in another embodiment of the present invention.
Main element symbol description
External power source 10
LED drive system 20,20a, 20b, 20c
Light emitting diode matrix 30
Light-emitting diodes pipe string 30a, 30b, 30c
DC-DC converter 202
Current regulation unit 204
Electronic switch Qa, Qb, Qc
Sampling resistor Ra, Rb, Rc
Control module 206,260a, 206b
Constant current unit 2061
The first comparing unit 2062
Judging unit 2063
Signal generation unit 2064
Memory cell 2065
Dynamic reference level adjustment unit 2066
The second comparing unit 2067
The 3rd comparing unit 2068
Pwm controller 208
Feedback unit 210
The first to second divider resistance R1, R2
Following detailed description of the invention further illustrates the present invention in connection with above-mentioned accompanying drawing.
Detailed description of the invention
Fig. 1 is the module map of light emitting diode in an embodiment of the present invention (Light Emitting Diode, LED) drive system 20.LED drive system 20 is for driving light emitting diode matrix 30 luminous.In the present embodiment, light-emitting diodes pipe string 30a, 30b, 30c(that light emitting diode matrix 30 comprises multiple parallel connections are in the present embodiment, only taking three as example, but be not limited with three, can comprise be less than or more than three light-emitting diodes pipe strings), each light-emitting diodes pipe string 30a, 30b, 30c are forward composed in series by multiple light emitting diodes.In the present embodiment, the forward voltage drop of each light-emitting diodes pipe string 30a, 30b, 30c is directly proportional to electric current, the anode of each light-emitting diodes pipe string 30a, 30b, 30c refers to the anode of this light-emitting diodes pipe string according to first light emitting diode of the sense of current, and the negative electrode of light-emitting diodes pipe string 30a, 30b, 30c refers to the negative electrode of last light emitting diode of this light-emitting diodes pipe string.In like manner, the negative electrode of light emitting diode matrix 30 refers to the common end of light-emitting diodes pipe string 30a, 30b, 30c negative electrode, and the anode of light emitting diode matrix 30 refers to the common end of light-emitting diodes pipe string 30a, 30b, 30c anode.
LED drive system 20 comprises DC-DC converter 202, current regulation unit 204, control module 206 and Pwm controller 208.DC-DC converter 202 is electrically connected at external power source 10 and light emitting diode matrix 30, and the input voltage of external power source 10 is converted to driving voltage, to drive light emitting diode matrix 30 luminous.Control module 206 is electrically connected at light emitting diode matrix 30, comprises constant current unit 2061, the first comparing unit 2062, judging unit 2063 and signal generation unit 2064.Constant current unit 2061 is detected the electric current of flow through each light-emitting diodes pipe string 30a, 30b, 30c, to obtain the current regulating signal of each light-emitting diode pipe string 30a, 30b, 30c.The current regulating signal of the more multiple light emitting diode string of the first comparing unit 2062 30a, 30b, 30c, to obtain the maximum of current regulating signal of multiple light-emitting diodes pipe string 30a, 30b, 30c.Judging unit 2063 judges whether the maximum of the current regulating signal of multiple light-emitting diodes pipe string 30a, 30b, 30c is also exported and judged signal between the first setting value and the second setting value.Signal generation unit 2064 is according to judging that signal produces and export control signal.Pwm controller 208 is electrically connected at control module 206 and DC-DC converter 202, according to control signal output pulse width modulation signal, with the driving voltage that regulates DC-DC converter 202 to export.
As further improving of an embodiment of the present invention, LED drive system 20 also comprises current regulation unit 204, be electrically connected between the negative electrode and control module 206 of light emitting diode matrix 30, constant current unit 2061 is also for detect the electric current of flow through each light-emitting diodes pipe string 30a, 30b, 30c by current regulation unit 204, to obtain the current regulating signal of each light-emitting diode pipe string 30a, 30b, 30c.In other words, constant current unit 2061 can be by each light-emitting diodes pipe string 30a of direct detecting, 30b, 30c obtain the flowing through electric current of each light-emitting diodes pipe string 30a, 30b, 30c, also can be by the flow through electric current of each light-emitting diodes pipe string 30a, 30b, 30c of current regulation unit 204 detectings.
As further improving of an embodiment of the present invention, LED drive system 20 also comprises feedback unit 210, be electrically connected at DC-DC converter 202 and Pwm controller 208, the driving voltage generation of exporting according to DC-DC converter 202 output feedback signal are to Pwm controller 208, to adjust the dutycycle of pulse width modulating signal.
Fig. 2 circuit diagram of LED drive system 20a in an embodiment of the present invention of having explained in detail.In the present embodiment, current regulation unit 204 is electrically connected at the negative electrode of each light-emitting diodes pipe string 30a, 30b, 30c in light emitting diode matrix 30, for regulating the electric current of flow through each light-emitting diodes pipe string 30a, 30b, 30c.Current regulation unit 204 comprises multiple electronic switch Qa, Qb and Qc, one by one the negative electrode of light-emitting diodes pipe string 30a, 30b and 30c in corresponding electric connection light emitting diode matrix 30.Current regulation unit 204 also comprises multiple sampling resistor Ra, Rb and Rc, one by one corresponding multiple electronic switch Qa, Qb and the Qc of being electrically connected.In other words, the quantity of included multiple electronic switch Qa, the Qb of current regulation unit 204 and Qc and multiple sampling resistor Ra, Rb and Rc is identical with the quantity of multiple light-emitting diodes pipe string 30a, 30b, 30c in light emitting diode matrix 30.In the present embodiment, electronic switch Qa, Qb and Qc can be the electronic switch of transistor, FET or other type.Below will be described in detail taking electronic switch Qa, Qb and Qc as transistor.
Refer to Fig. 3, in another embodiment of the present invention, electronic switch Qa, Qb and Qc are transistor, the control of electronic switch Qa, Qb and Qc is the base stage of transistor very, the colelctor electrode that the first electrode of electronic switch Qa, Qb and Qc is transistor, the emitter stage that the second electrode of electronic switch Qa, Qb and Qc is transistor.The base stage of electronic switch Qa, Qb and Qc is electrically connected at constant current unit 2061, the emitter stage of electronic switch Qa, Qb and Qc is corresponding one end that is electrically connected at sampling resistor Ra, Rb and Rc one by one, and the colelctor electrode of electronic switch Qa, Qb and Qc is the corresponding negative electrode that is electrically connected at light-emitting diodes pipe string 30a, 30b and 30c one by one.The other end ground connection of sampling resistor Ra, Rb and Rc.
In the present embodiment, control module 206a and current regulation unit 204, Pwm controller 208 is electrically connected, control module 206a is according to each light-emitting diodes pipe string 30a that flows through in light emitting diode matrix 30, 30b, the electric current of 30c, produce and output control signals to Pwm controller 208, export the dutycycle of the pulse width modulating signal of DC-DC converter 202 to control impuls width modulation controller 208, and produce and export multiple current regulating signals to current regulation unit 204, to control electronic switch Qa, whether conducting or On current size of Qb and Qc, thereby regulate the electric current of respective leds string.As by the base current that increases electronic switch Qa, Qb and Qc, thereby increase flow through electronic switch Qa, Qb and Qc colelctor electrode to the electric current of emitter stage, thereby increase the electric current of respective leds string.In the present embodiment, control module 206a comprises constant current unit 2061, the first comparing unit 2062, judging unit 2063, signal generation unit 2064 and memory cell 2065.
Constant current unit 2061 is detected the electric current of flow through each light-emitting diodes pipe string 30a, 30b, 30c, thus the corresponding current regulating signal that obtains each light-emitting diode pipe string 30a, 30b, 30c.Meanwhile, the current regulating signal of multiple light-emitting diodes pipe string 30a, 30b, 30c is sent to current regulation unit 204 and the first comparing unit 2062 by constant current unit 2061.Current regulating signal and the electric current of light-emitting diodes pipe string 30a, 30b, 30c of the flowing through functional relation that is inversely proportional in the present embodiment.In other words, the electric current of flow through light-emitting diodes pipe string 30a, 30b, 30c is larger, and the current regulating signal obtaining is less.
The current regulating signal of the more multiple light emitting diode string of the first comparing unit 2062 30a, 30b, 30c, with obtain multiple light-emitting diodes pipe string 30a, 30b, 30c current regulating signal maximum and the maximum of the current regulating signal of the multiple light-emitting diodes pipe string 30a that obtain, 30b, 30c is sent to judging unit 2063.
Judging unit 2063 judges whether the maximum of the current regulating signal of multiple light-emitting diodes pipe string 30a, 30b, 30c is also exported and judged signal between the first setting value and the second setting value.In the present embodiment, the first setting value has defined with second the empirical value that LED drive system 20b is stable, can be by user according to experimental data or specifically need to set, and first set value and be less than the second setting value.In the time that the maximum of the current regulating signal of multiple light-emitting diodes pipe string 30a, 30b, 30c is between the first setting value and the second setting value, be the maximum of the current regulating signal of multiple light-emitting diodes pipe string 30a, 30b, 30c when being more than or equal to the first setting value and being less than or equal to the second setting value, produce first and judge signal.In the time that the maximum of the current regulating signal of multiple light-emitting diodes pipe string 30a, 30b, 30c is less than the first setting value, produces second and judge signal.In the time that the maximum of the current regulating signal of multiple light-emitting diodes pipe string 30a, 30b, 30c is greater than the second setting value, produces the 3rd and judge signal.
The judgement signal that signal generation unit 2064 is exported according to judging unit 2063 produces and outputs control signals to Pwm controller 208, to regulate the output of DC-DC converter 202.When signal generation unit 2064 receive judge that signal is the first judgement signal time, produce and output duty cycle is constant controls signal to Pwm controller 208.When signal generation unit 2064 receive judge that signal is the second judgement signal time, what generation output duty cycle reduced controls signal to Pwm controller 208, to adjust the dutycycle of pulse width modulating signal, thereby control DC-DC converter 202 and export the driving voltage reducing, to drive light emitting diode matrix 30, the electric current of light emitting diode matrix 30 is reduced.And the signal that judges receiving when signal generation unit 2064 is the 3rd while judging signal, what generation output duty cycle increased controls signal to Pwm controller 208, to adjust the dutycycle of pulse width modulating signal, thereby control the driving voltage that DC-DC converter 202 outputs increase, to drive light emitting diode matrix 30, the electric current of light emitting diode matrix 30 is increased.
As the further improvement of an embodiment of the present invention, what signal generation unit 2064 received judge, and signal is the 3rd while judging signal, produces and output duty cycle increases controls signal to Pwm controller 208.Pwm controller 208 judges whether output pulse width modulation signal is greater than threshold value, if be not more than threshold value, the pulse width modulating signal that Pwm controller 208 output duty cycles increase, thereby control the driving voltage that DC-DC converter 202 outputs increase, to drive light emitting diode matrix 30, the electric current of light emitting diode matrix 30 is increased.If be greater than threshold value, the pulse width modulating signal that Pwm controller 208 output duty cycles reduce, to adjust the dutycycle of pulse width modulating signal, thereby control DC-DC converter 202 and export the driving voltage reducing, to drive light emitting diode matrix 30, the electric current of light emitting diode matrix 30 is reduced.
In the present embodiment, constant current unit 2061 is exported the current regulating signal of each light-emitting diodes pipe string 30a, 30b, 30c in real time according to the electric current adjustment of each light-emitting diodes pipe string 30a, 30b, 30c, the first comparing unit 2062 relatively and obtain the maximum of the current regulating signal of multiple light-emitting diodes pipe string 30a, 30b, 30c, then be sent to judging unit 2063, judging unit 2063 judges whether the maximum of the current regulating signal of multiple light-emitting diodes pipe string 30a, 30b, 30c is also exported and judged signal between the first setting value and the second setting value.By repeating N(N=1,2,3 ...) inferior above-mentioned adjustment until the maximum of the current regulating signal of multiple light-emitting diodes pipe string 30a, 30b, 30c the first setting value and second setting value between reach balance.What now, 2064 generations of signal generation unit output duty cycle were constant controls signal to Pwm controller 208.
Memory cell 2065 is for storing the first setting value and the second setting value.
In the present embodiment, feedback unit 210 is electrically connected with output and the Pwm controller 208 of DC-DC converter 202, the driving voltage of exporting to receive DC-DC converter 202, and the driving voltage of exporting according to DC-DC converter 202 produce and output feedback signal to Pwm controller 208, to adjust the dutycycle of pulse width modulating signal.In the present embodiment, the control signal of the feedback signal that feedback unit 210 is exported and control module 206a output is adjusted the dutycycle of pulse width modulating signal jointly, thereby adjustment DC-DC converter 202 exports the DC voltage of light emitting diode matrix 30 to, thereby regulate the size of current of the light emitting diode matrix 30 of flowing through, wherein, the feedback signal that feedback unit 210 is exported plays a leading role, and the control signal of control module 206a output plays fine setting effect.Simultaneously, current regulating signal regulation electronic switch Qa, the Qb that current regulation unit 204 can be exported by reception control unit 206a and the base current of Qc, thereby regulate the colelctor electrode of flow through electronic switch Qa, Qb and Qc to the electric current of emitter stage, thereby regulate the electric current of light emitting diode matrix 30.The control signal of the feedback signal that in other words, feedback unit 210 is exported and control module 206a output and current regulating signal are adjusted the electric current of light emitting diode matrix 30 jointly.
In the present embodiment, feedback unit 210 comprises the first divider resistance R1, the second divider resistance R2.The output of first divider resistance R1 one end and DC-DC converter 202 is electrically connected, and the other end and Pwm controller 208 are electrically connected.The other end of second divider resistance R2 one end and the first divider resistance R1 is electrically connected, other end ground connection.In another embodiment of the present invention, feedback unit 210 also can be inductance coil, with the driving voltage exported according to DC-DC converter 202 produce and output feedback signal to Pwm controller 208, to adjust the dutycycle of pulse width modulating signal.
In the present embodiment, light-emitting diodes pipe string 30a, 30b, 30c electric current maximum, represent respective leds string current regulating signal minimum, and light-emitting diodes pipe string 30a, 30b, 30c electric current minimum represent respective leds string current regulating signal maximum.Therefore, the electric current minimum of light-emitting diodes pipe string corresponding to current regulating signal maximum, regulate light-emitting diodes pipe string 30a by current regulating signal, 30b, the electric current of 30c, reduce the dutycycle of the pulse width modulating signal regulating according to the pressure drop of the light-emitting diodes pipe string of pressure drop maximum, thereby reduce the driving voltage that DC-DC converter 202 is exported, and then reduce in other string and divided the corresponding electronic switch Qa to current regulation unit 204, Qb, multivoltage excessively on Qc, improve electronic switch Qa, Qb, Qc is because producing the thermal stress issues causing compared with large power attenuation.
The explained in detail circuit diagram of LED drive system 20c in the another embodiment of the present invention of Fig. 4.In present embodiment, shown in LED drive system 20c and Fig. 3, the circuit of LED drive system 20b is basic identical, and difference is that control module 206b also comprises dynamic reference level adjustment unit 2066, the second comparing unit 2067, the 3rd comparing unit 2068.The judgement signal that dynamic reference level adjustment unit 2066 is exported according to judging unit 2063 is adjusted with reference to level voltage.The second comparing unit 2067 is for the negative electrode dividing potential drop of more multiple light emitting diode string 30a, 30b, 30c, to obtain the minimum of a value of negative electrode dividing potential drop of multiple light-emitting diodes pipe string 30a, 30b, 30c.The 3rd comparing unit is for the minimum of a value of the negative electrode dividing potential drop of more multiple light emitting diode string 30a, 30b, 30c and the reference level voltage that dynamic reference level adjustment unit 2066 is exported, produce and export control signal with control signal generation unit 2064, the control signal that Pwm controller 208 is exported according to signal generation unit 2064 is adjusted the driving voltage that DC-DC converter 202 is exported.
The circuit working principle of present embodiment and the operation principle of the first embodiment are basic identical, difference is, judging unit 2063 is in the time that the minimum of a value of the negative electrode dividing potential drop of multiple light-emitting diodes pipe string 30a, 30b, 30c is greater than the reference level voltage that dynamic reference level adjustment unit 2066 exports, produce and export with reference to the constant judgement signal of level voltage to dynamic reference level adjustment unit 2066, signal generation unit 2064 produces and output duty cycle is constant controls signal to Pwm controller 208.Judging unit 2063 is in the time that the minimum of a value of the negative electrode dividing potential drop of multiple light-emitting diodes pipe string 30a, 30b, 30c is not more than the reference level voltage that dynamic reference level adjustment unit 2066 exports, and the maximum of the current regulating signal of multiple light-emitting diodes pipe string 30a, 30b, 30c the first setting value and second setting value between time, produce and export with reference to the constant judgement signal of level voltage to dynamic reference level adjustment unit 2066, signal generation unit 2064 produces and output duty cycle is constant controls signal to Pwm controller 208.Judging unit 2063 is at multiple light-emitting diodes pipe string 30a, 30b, when the minimum of a value of the negative electrode dividing potential drop of 30c is not more than the reference level voltage that dynamic reference level adjustment unit 2066 exports, and multiple light-emitting diodes pipe string 30a, 30b, when the maximum of the current regulating signal of 30c is less than the first setting value, produce and export the judgement signal reducing with reference to level voltage to dynamic reference level adjustment unit 2066, thereby reduce the reference level voltage that dynamic reference level adjustment unit 2066 is exported, what 2064 generations of signal generation unit output duty cycle reduced controls signal to Pwm controller 208, to adjust the dutycycle of pulse width modulating signal.Judging unit 2063 is at multiple light-emitting diodes pipe string 30a, 30b, when the minimum of a value of the negative electrode dividing potential drop of 30c is not more than the reference level voltage that dynamic reference level adjustment unit 2066 exports, and multiple light-emitting diodes pipe string 30a, 30b, when the maximum of the current regulating signal of 30c is greater than the second setting value, produce and export the judgement signal increasing with reference to level voltage to dynamic reference level adjustment unit 2066, thereby increase the reference level voltage that dynamic reference level adjustment unit 2066 is exported, what 2064 generations of signal generation unit output duty cycle increased controls signal to Pwm controller 208, to adjust the dutycycle of pulse width modulating signal.So locate no longer to describe in detail.
Fig. 5 is the flow chart of LED driving method in an embodiment of the present invention.First, in step S5000, constant current unit 2061 is detected the electric current of flow through multiple light-emitting diodes pipe string 30a, 30b, 30c, and according to the current regulating signal of the multiple light-emitting diodes pipe string 30a of the corresponding output of the electric current of multiple light-emitting diodes pipe string 30a, 30b, 30c, 30b, 30c.In step S5001, the first comparing unit 2062 is detected the current regulating signal of multiple light-emitting diodes pipe string 30a, 30b, 30c and is therefrom found out maximum.In step S5002, judging unit 2063 judges that the maximum of current regulating signal is whether between the first setting value and the second setting value.If the maximum of current regulating signal is between the first setting value and the second setting value, in step S5003, what 2064 generations of signal generation unit output duty cycle were constant controls signal to Pwm controller 208, the constant pulse width modulating signal of Pwm controller 208 output duty cycles is to DC-DC converter 202, and the driving voltage that now DC-DC converter 202 is exported remains unchanged.If the maximum of current regulating signal is not between the first setting value and the second setting value,, in step S5004, judging unit 2063 judges whether the maximum of current regulating signal is greater than the second setting value.If the maximum of current regulating signal is greater than the second setting value,, in step S5006, Pwm controller 208 judges whether output duty cycle is greater than threshold value.If Pwm controller 208 output duty cycles are greater than threshold value, in step S5007, the pulse width modulating signal that Pwm controller 208 output duty cycles reduce is to DC-DC converter 202, and the driving voltage that now DC-DC converter 202 is exported reduces.If Pwm controller 208 output duty cycles are not more than threshold value, in step S5008, the pulse width modulating signal that Pwm controller 208 output duty cycles increase is to DC-DC converter 202, and the driving voltage that now DC-DC converter 202 is exported increases.If the maximum of current regulating signal is less than the second setting value, in step S5005, what 2064 generations of signal generation unit output duty cycle reduced controls signal to Pwm controller 208, the pulse width modulating signal that Pwm controller 208 output duty cycles reduce is to DC-DC converter 202, and the driving voltage that now DC-DC converter 202 is exported reduces.
Fig. 6 is the flow chart of LED driving method in another embodiment of the present invention.Step S6000, S6001, S6005, S6007 in flow chart are in the present embodiment corresponding similar one by one with step S5000, S5001, S5002, the S5004 of the flow chart in Fig. 5, thereby no longer describe in detail.Wherein, in step S6002, the second comparing unit 2067 is detected the dividing potential drop of multiple light-emitting diodes pipe string 30a, 30b, 30c negative electrode and is therefrom found out minimum of a value.In step S6003, the 3rd comparing unit 2068 judges whether the minimum of a value of the negative electrode dividing potential drop of multiple light-emitting diodes pipe string 30a, 30b, 30c is greater than the reference level voltage of dynamic reference level adjustment unit output.If the minimum of a value of the negative electrode dividing potential drop of multiple light-emitting diodes pipe string 30a, 30b, 30c is greater than the reference level voltage of dynamic reference level adjustment unit output, in step S6004, judging unit 2063 is exported with reference to the constant adjustment signal of level voltage to dynamic reference level adjustment unit 2066, signal generation unit 2064 produces and output duty cycle is constant controls signal to Pwm controller 208, and the constant pulse width modulating signal of Pwm controller 208 output duty cycles is to DC-DC converter 202.If the minimum of a value of the negative electrode dividing potential drop of multiple light-emitting diodes pipe string 30a, 30b, 30c is not more than the reference level voltage of dynamic reference level adjustment unit output, enter step S6005.If the maximum of current regulating signal is between the first setting value and the second setting value, in step S6006, judging unit 2063 is exported with reference to the constant adjustment signal of level voltage to dynamic reference level adjustment unit 2066, signal generation unit 2064 produces and output duty cycle is constant controls signal to Pwm controller 208, and the constant pulse width modulating signal of Pwm controller 208 output duty cycles is to DC-DC converter 202.If the maximum of current regulating signal, between the first setting value and the second setting value, does not enter step S6007.If the maximum of current regulating signal is greater than the second setting value, in step S6008, judging unit 2063 is exported the adjustment signal increasing with reference to level voltage to dynamic reference level adjustment unit 2066, what 2064 generations of signal generation unit output duty cycle increased controls signal to Pwm controller 208, and the pulse width modulating signal that Pwm controller 208 output duty cycles increase is to DC-DC converter 202.If the maximum of current regulating signal is less than the second setting value, in step S6009, judging unit 2063 is exported the adjustment signal reducing with reference to level voltage to dynamic reference level adjustment unit 2066, what 2064 generations of signal generation unit output duty cycle reduced controls signal to Pwm controller 208, and the pulse width modulating signal that Pwm controller 208 output duty cycles reduce is to DC-DC converter 202.
Above-mentioned LED drive system and method are carried out light emitting diode matrix driving voltage rapid adjustment according to the electric current of current light-emitting diodes array in real time, improve the thermal stress issues that electronic switch causes because of power attenuation, improved power supply service efficiency simultaneously.
Claims (18)
1. a LED driving method, for LED drive system, be used for driving light emitting diode matrix, described light emitting diode matrix comprises the light-emitting diodes pipe string of multiple parallel connections, described LED drive system comprises control module, Pwm controller, described control module comprises constant current unit, the first comparing unit, judging unit, signal generation unit, it is characterized in that, described LED driving method comprises:
The flow through electric current of described multiple light-emitting diodes pipe strings according to the current regulating signal of the described multiple light-emitting diodes pipe strings of the corresponding output of the electric current of described multiple light-emitting diodes pipe strings of described constant current unit detecting;
The current regulating signal of the described multiple light-emitting diodes pipe strings of described the first comparing unit detecting is also therefrom found out maximum;
Described judging unit judges whether the maximum of described current regulating signal is also exported and judged signal between the first setting value and the second setting value;
Described signal generation unit produces and exports control signal according to described judgement signal;
Described Pwm controller is according to described control signal output pulse width modulation signal, to drive described light emitting diode matrix.
2. LED driving method as claimed in claim 1, is characterized in that, the step that described signal generation unit produced and exported control signal according to described judgement signal comprises:
Judge if described signal be the maximum of described current regulating signal between the first setting value and the second setting value, described signal generation unit produces and the constant control signal of output duty cycle;
Judge that if described signal is that the maximum of described current regulating signal is greater than described the second setting value, the control signal that described signal generation unit produces and output duty cycle increases; And
Judge that if described signal is that the maximum of described current regulating signal is less than described the first setting value, the control signal that described signal generation unit produces and output duty cycle reduces.
3. LED driving method as claimed in claim 2, is characterized in that, described Pwm controller, according to described control signal output pulse width modulation signal, comprises with the step that drives described light emitting diode matrix:
If described control signal is the control signal that dutycycle increases, described Pwm controller judges whether output duty cycle is greater than threshold value;
If described Pwm controller output duty cycle is greater than threshold value, the pulse width modulating signal that output duty cycle reduces; And
If described Pwm controller output duty cycle is not more than threshold value, the pulse width modulating signal that output duty cycle increases.
4. LED driving method as claimed in claim 1, it is characterized in that, described control module also comprises dynamic reference level adjustment unit, the second comparing unit, the 3rd comparing unit, the flow through electric current of described multiple light-emitting diodes pipe strings comprising according to the step of the current regulating signal of the described multiple light-emitting diodes pipe strings of the corresponding output of the electric current of described multiple light-emitting diodes pipe strings of described constant current unit detecting: the dividing potential drop of the described multiple light-emitting diodes pipe string negative electrodes of described the second comparing unit detecting is also therefrom found out minimum of a value.
5. LED driving method as claimed in claim 4, is characterized in that, the step that described signal generation unit produced and exported control signal according to described judgement signal comprises:
Described the 3rd comparing unit judges whether the minimum of a value of the negative electrode dividing potential drop of described multiple light-emitting diodes pipe strings is greater than the reference level voltage of described dynamic reference level adjustment unit output;
If the minimum of a value of the negative electrode dividing potential drop of described multiple light-emitting diodes pipe strings is greater than described with reference to level voltage, described judging unit output is with reference to the constant extremely described dynamic reference level adjustment unit of adjustment signal of level voltage, and described signal generation unit produces and the constant control signal of output duty cycle;
If the minimum of a value of the negative electrode dividing potential drop of described multiple light-emitting diodes pipe strings be not more than described with reference to level voltage and described judge signal be described current regulating signal maximum the first setting value and second setting value between, described judging unit output is with reference to the constant extremely described dynamic reference level adjustment unit of adjustment signal of level voltage, and described signal generation unit produces and the constant control signal of output duty cycle;
If the minimum of a value of the negative electrode dividing potential drop of described multiple light-emitting diodes pipe strings is not more than described with reference to level voltage and describedly judge that signal is that the maximum of described current regulating signal is greater than described the second setting value, the adjustment signal that described judging unit output increases with reference to level voltage is to described dynamic reference level adjustment unit, and described signal generation unit produces the control signal that also output duty cycle increases; And
If the minimum of a value of the negative electrode dividing potential drop of described multiple light-emitting diodes pipe strings is not more than described with reference to level voltage and describedly judge that signal is that the maximum of described current regulating signal is less than described the first setting value, described judging unit is exported the adjustment signal reducing with reference to level voltage to described dynamic reference level adjustment unit, the control signal that described signal generation unit produces and output duty cycle reduces.
6. a LED drive system, for outer power voltage being converted to the voltage that is applicable to driving light emitting diode matrix work, described light emitting diode matrix comprises the light-emitting diodes pipe string of multiple parallel connections, it is characterized in that, described LED drive system comprises:
DC-DC converter, for being electrically connected at described external power source and described light emitting diode matrix, for the input voltage of described external power source is converted to driving voltage, to drive described light emitting diode matrix luminous;
Control module, for being electrically connected at described light emitting diode matrix, comprising:
Constant current unit, for detecting the electric current of described each the light-emitting diodes pipe string of flowing through, to obtain the current regulating signal of each light-emitting diode pipe string;
The first comparing unit, for the current regulating signal of more described multiple light-emitting diodes pipe strings, to obtain the maximum of current regulating signal of described multiple light-emitting diodes pipe strings;
Judging unit, for judge described multiple light-emitting diodes pipe strings current regulating signal maximum whether between the first setting value and the second setting value and output judge signal; And
Signal generation unit, for producing and export control signal according to described judgement signal; And
Pwm controller, for being electrically connected at described control module and described DC-DC converter, for according to described control signal output pulse width modulation signal, to regulate the driving voltage of described DC-DC converter output.
7. LED drive system as claimed in claim 6, it is characterized in that, also comprise current regulation unit, for being electrically connected between the negative electrode and described control module of described light emitting diode matrix, described constant current unit is also for detect the electric current of described each the light-emitting diodes pipe string of flowing through by described current regulation unit, to obtain the current regulating signal of each light-emitting diode pipe string.
8. LED drive system as claimed in claim 7, is characterized in that, described current regulation unit is also for regulating the electric current of described each the light-emitting diodes pipe string of flowing through according to the current regulating signal of described each light-emitting diode pipe string.
9. LED drive system as claimed in claim 6, it is characterized in that, described signal generation unit is also for the maximum of the current regulating signal at described multiple light-emitting diodes pipe strings between described the first setting value sets value with described second time, produce and the constant control signal of output duty cycle, in the time that the maximum of the current regulating signal of described multiple light-emitting diodes pipe strings is less than described the first setting value, produce the control signal that also output duty cycle reduces, and in the time that the maximum of the current regulating signal of described multiple light-emitting diodes pipe strings is greater than described the second setting value, produce the described Pwm controller that controls signal to of also output duty cycle increase, to adjust the dutycycle of described pulse width modulating signal.
10. LED drive system as claimed in claim 9, it is characterized in that, described Pwm controller is also for judging whether described output pulse width modulation signal is greater than threshold value, in the time being not more than threshold value, the pulse width modulating signal that output duty cycle increases, and in the time being greater than threshold value, the pulse width modulating signal that output duty cycle reduces.
11. LED drive systems as claimed in claim 6, is characterized in that, described control module also comprises:
Dynamic reference level adjustment unit, for adjusting with reference to level voltage according to the judgement signal of described judging unit output;
The second comparing unit, for the negative electrode dividing potential drop of more described multiple light-emitting diodes pipe strings, to obtain the minimum of a value of negative electrode dividing potential drop of described multiple light-emitting diodes pipe strings; And
The 3rd comparing unit, for the minimum of a value of the negative electrode dividing potential drop of more described multiple light-emitting diodes pipe strings and described with reference to level voltage, produces and exports control signal to control described signal generation unit.
12. LED drive systems as claimed in claim 11, it is characterized in that, described judging unit is greater than described during with reference to level voltage in the minimum of a value of the negative electrode dividing potential drop of described multiple light-emitting diodes pipe strings, produce and export the judgement signal extremely described dynamic reference level adjustment unit constant with reference to level voltage, what described signal generation unit generation output duty cycle were constant controls signal to described Pwm controller, and described judging unit is not more than described during with reference to level voltage in the minimum of a value of the negative electrode dividing potential drop of described multiple light-emitting diodes pipe strings, and the maximum of the current regulating signal of described multiple light-emitting diodes pipe strings is in the time that described first sets value between described the second setting value, produce and export the judgement signal extremely described dynamic reference level adjustment unit constant with reference to level voltage, what described signal generation unit generation output duty cycle were constant controls signal to described Pwm controller.
13. LED drive systems as claimed in claim 11, it is characterized in that, described judging unit is not more than described during with reference to level voltage in the minimum of a value of the negative electrode dividing potential drop of described multiple light-emitting diodes pipe strings, and when the maximum of the current regulating signal of described multiple light-emitting diodes pipe strings is less than described the first setting value, produce and export the judgement signal reducing with reference to level voltage to described dynamic reference level adjustment unit, described with reference to level voltage to adjust, what described signal generation unit produced and output duty cycle reduces controls signal to described Pwm controller, to adjust the dutycycle of described pulse width modulating signal.
14. LED drive systems as claimed in claim 11, it is characterized in that, described judging unit is not more than described during with reference to level voltage in the minimum of a value of the negative electrode dividing potential drop of described multiple light-emitting diodes pipe strings, and when the maximum of the current regulating signal of described multiple light-emitting diodes pipe strings is greater than described the second setting value, produce and export the judgement signal increasing with reference to level voltage to described dynamic reference level adjustment unit, described with reference to level voltage to adjust, described signal generation unit produces the described Pwm controller that controls signal to of also output duty cycle increase, to adjust the dutycycle of described pulse width modulating signal.
15. LED drive systems as claimed in claim 7, is characterized in that, described current regulation unit comprises:
Electronic switch, sampling resistor with the corresponding electric connection of each light-emitting diodes pipe string, described electronic switch comprises controls the utmost point, the first electrode, the second electrode, described the first electrode is connected with described light-emitting diodes pipe string cathodic electricity, the described control utmost point and described constant current unit are electrically connected, described the second electrode and described sampling resistor one end are electrically connected, described sampling resistor other end ground connection.
16. LED drive systems as claimed in claim 6, is characterized in that, the electric current of described current regulating signal and the described light-emitting diodes pipe string functional relation that is inversely proportional to.
17. LED drive systems as claimed in claim 6, is characterized in that, also comprise:
Feedback unit, be used for being electrically connected at described DC-DC converter and described Pwm controller, for producing according to the driving voltage of described DC-DC converter output and extremely described Pwm controller of output feedback signal, to adjust the dutycycle of described pulse width modulating signal.
18. LED drive systems as claimed in claim 17, is characterized in that, described feedback unit comprises:
The first divider resistance, the output of one end and described DC-DC converter is electrically connected, and the other end and Pwm controller are electrically connected; And
The second divider resistance, the other end of one end and the first divider resistance is electrically connected, other end ground connection.
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|---|---|---|---|
| CN201310095829.XA CN104075135A (en) | 2013-03-25 | 2013-03-25 | Driving system and method for light emitting diodes |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106710531A (en) * | 2017-01-19 | 2017-05-24 | 深圳市华星光电技术有限公司 | Backlight control circuit and electronic device |
| CN112259042A (en) * | 2019-07-22 | 2021-01-22 | 凹凸电子（武汉）有限公司 | Controller for controlling light source module |
| CN113808546A (en) * | 2021-09-14 | 2021-12-17 | Tcl华星光电技术有限公司 | Light source driving circuit and light source driving method of display panel |
-
2013
- 2013-03-25 CN CN201310095829.XA patent/CN104075135A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106710531A (en) * | 2017-01-19 | 2017-05-24 | 深圳市华星光电技术有限公司 | Backlight control circuit and electronic device |
| CN106710531B (en) * | 2017-01-19 | 2019-11-05 | 深圳市华星光电技术有限公司 | Backlight control circuit and electronic device |
| CN112259042A (en) * | 2019-07-22 | 2021-01-22 | 凹凸电子（武汉）有限公司 | Controller for controlling light source module |
| CN113808546A (en) * | 2021-09-14 | 2021-12-17 | Tcl华星光电技术有限公司 | Light source driving circuit and light source driving method of display panel |
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Application publication date: 20141001 |