CN107221293B - Duty ratio regulating circuit and LED backlight brightness regulating circuit - Google Patents
Duty ratio regulating circuit and LED backlight brightness regulating circuit Download PDFInfo
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- CN107221293B CN107221293B CN201710368290.9A CN201710368290A CN107221293B CN 107221293 B CN107221293 B CN 107221293B CN 201710368290 A CN201710368290 A CN 201710368290A CN 107221293 B CN107221293 B CN 107221293B
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Classifications
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
- G09G3/3406—Control of illumination source
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/10—Controlling the intensity of the light
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/06—Adjustment of display parameters
- G09G2320/0626—Adjustment of display parameters for control of overall brightness
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
- Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
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- General Physics & Mathematics (AREA)
- Theoretical Computer Science (AREA)
- Circuit Arrangement For Electric Light Sources In General (AREA)
- Circuit Arrangements For Discharge Lamps (AREA)
Abstract
The invention discloses a duty ratio regulating circuit, which comprises a pulse output module, a duty ratio judging module and a duty ratio regulating module; the pulse output module is used for receiving the first pulse signal, performing level conversion on the first pulse signal and outputting a second pulse signal; the duty ratio judging module is used for receiving the second pulse signal and sending a duty ratio adjusting signal to the duty ratio adjusting module when the duty ratio of the second pulse signal is lower than the set duty ratio; the duty ratio adjusting module is used for receiving the first pulse signal and the duty ratio adjusting signal and outputting a third pulse signal according to the duty ratio adjusting signal. Correspondingly, the invention also discloses an LED backlight brightness adjusting circuit. When the duty ratio of the received pulse signal is lower than the set duty ratio, the duty ratio of the pulse signal is adjusted, and the duty ratio of the pulse signal is ensured to be always within the range of the normal working requirement of the circuit, so that the stability and the reliability of the circuit are improved.
Description
Technical field
The present invention relates to electronic technology field more particularly to duty ratio adjusting circuit and LED backlight brightness regulating circuits.
Background technique
The adjusting of the LED backlight brightness of liquid crystal TV set generally uses PWM dimming mode, that is, keeps the electricity by LED light
It flows constant, changes the duty ratio of PWM drive signal, make the LED light on and off time of backlight lamp group with PWM drive signal
The change of duty ratio and change, it is dark when bright when making LED light using the human eye characteristic not sensitive enough to brightness flicker, if bright dark
Frequency be more than certain value, seen by person is exactly average brightness, rather than the flashing of LED light, by adjusting the bright of LED light with
Dark time scale achievees the purpose that adjust LED light brightness.
The control chip for providing PWM drive signal often provides a minimum value to the duty ratio of the PWM drive signal of output,
So that output PWM drive signal duty ratio be greater than a certain setting value, generally 1%.However in practical applications, LED is carried on the back
The duty ratio that brightness adjusts the PWM drive signal allowed when circuit works normally cannot be below 5%.Therefore control chip output
PWM drive signal duty ratio be possible to fall in LED backlight brightness regulating circuit work normally demand duty cycle range it
Outside, the work of LED backlight brightness regulating circuit is caused to occur abnormal.
Summary of the invention
Technical problem to be solved by the present invention lies in provide a kind of duty ratio adjusting circuit and LED backlight brightness regulation
Circuit can set a minimum value to the duty ratio of the pulse signal received, guarantee the duty ratio of pulse signal position always
It is worked normally within range of needs in circuit, to improve the stability and reliability of circuit.
In order to solve the above-mentioned technical problems, the present invention provides a kind of duty ratio adjusting circuit, including pulse output module,
Duty ratio judgment module and duty ratio adjust module；
The pulse output module is used to receive the first pulse signal of pulse input end input, believes first pulse
Number level conversion is carried out, and exports the second pulse signal to pulse output end；
The duty ratio judgment module is for receiving second pulse signal, in the duty ratio of second pulse signal
Lower than setting duty ratio when, Xiang Suoshu duty ratio adjust module send duty ratio adjustment signal；
Duty ratio adjustment module for receiving first pulse signal and the duty ratio adjustment signal, and according to
The duty ratio adjustment signal exports third pulse signal to the pulse output end, wherein the height of the third pulse signal
The level value of level is identical as the level value of high level of second pulse signal.
Further, the pulse output module includes first voltage comparing unit and first diode；
The first voltage comparing unit receives first pulse signal, carries out level to first pulse signal and turns
It changes, exports the second pulse signal；
The first diode is connect with the first voltage comparing unit, when second pulse signal is high level
Conducting ends when second pulse signal is low level.
Further, the duty ratio judgment module includes first resistor, first capacitor and switching tube；
The first resistor receives second pulse signal, and exports second pulse signal；
The first capacitor is connect with the first resistor, stores electric energy when second pulse signal is high level；
The switching tube is connect with the first capacitor, when the electric energy reaches conducting voltage, switchs to be connected by cut-off.
Further, duty ratio adjustment module include the second diode, the second capacitor, second voltage comparing unit and
Third diode；
Second diode receives first pulse signal, is connected when first pulse signal is high level；
Second capacitor is connect with second diode, and electric energy is stored in second diode current flow, described
Second capacitor receives the duty ratio adjustment signal, discharges electric energy according to the duty ratio adjustment signal；
The second voltage comparing unit and second capacitance connection, when the electric energy reaches predeterminated voltage, output
High level signal；
The third diode is connect with the second voltage comparing unit, when the third pulse signal is high level
Conducting ends when the third pulse signal is low level.
Further, the pulse output module includes first voltage comparing unit and first diode；
For the non-inverting input terminal of the first voltage comparing unit for connecting pulse input end, the first voltage is more single
The inverting input terminal of member is for connecting reference voltage, output end and the first diode of the first voltage comparing unit
Anode connection, the cathode of the first diode are connect with the duty ratio judgment module, and the cathode of the first diode is also
For connecting pulse output end.
Further, the duty ratio judgment module includes first resistor, first capacitor and switching tube；
The first end of the switching tube is connect with duty ratio adjustment module, the second end ground connection of the switching tube, institute
The control terminal for stating switching tube is separately connected the second end of the first resistor and the first end of the first capacitor, first electricity
The second end of appearance is grounded, and the first end of the first resistor is connect with the pulse output module.
Further, the duty ratio judgment module further includes the 4th diode；
4th diode anode connect with the second end of the first resistor, the cathode of the 4th diode and
The first end of the first resistor connects.
Preferably, the switching tube is NPN type triode, the extremely described switching tube of the current collection of the NPN type triode
First end, the second end of the extremely described switching tube of transmitting of the NPN type triode, the base stage of the NPN type triode is institute
State the control terminal of switching tube.
Further, the duty ratio judgment module further includes second resistance；
The switching tube is N-channel MOS pipe, and the drain electrode of the N-channel MOS pipe is the first end of the switching tube, the N
The source electrode of channel MOS tube is the second end of the switching tube, and the grid of the N-channel MOS pipe is the control terminal of the switching tube；
The first end of the second resistance is connect with the grid of the N-channel MOS pipe, the second termination of the second resistance
Ground.
Further, duty ratio adjustment module include the second diode, the second capacitor, second voltage comparing unit and
Third diode；
For the anode of second diode for connecting pulse input end, the cathode of second diode is separately connected institute
State the non-inverting input terminal of second voltage comparing unit and the first end of second capacitor, the second voltage comparing unit it is anti-
Phase input terminal connects for connecting reference voltage, the output end of the second voltage comparing unit and the positive of the third diode
It connects, the cathode of the third diode connects the pulse output module, and the first end of second capacitor connects the duty
Than judgment module, the second end of second capacitor is grounded.
Further, the duty ratio adjustment module further includes 3rd resistor, and the anode of second diode is for connecting
Pulse input end is connect, specifically: second diode connects pulse input end by the 3rd resistor.
Duty ratio adjusting circuit provided by the invention, pulse output module carry out level to the first pulse signal received
The second pulse signal is exported after conversion, duty ratio judgment module receives the second pulse signal, and judges accounting for for the second pulse signal
Whether sky when the duty ratio of the second pulse signal is lower than the duty ratio of setting to duty ratio than adjusting lower than the duty ratio set
Module sends duty ratio adjustment signal and exports the level of high level after duty ratio adjustment module receives duty ratio adjustment signal
Be worth identical with the level value of the high level of the second pulse signal third pulse signal, to the duty ratio of the second pulse signal into
Row adjustment, makes it higher than the duty ratio of setting, guarantees that the duty ratio of the second pulse signal works normally demand always situated in circuit
Within the scope of, to improve the stability and reliability of circuit.
Correspondingly, the present invention also provides a kind of LED backlight brightness regulating circuits, including control processing module, duty ratio
Adjust circuit and LED drive module；
The control processing module generates first for receiving duty ratio setting signal, according to the duty ratio setting signal
Pulse signal；
The duty ratio adjusting circuit is foregoing duty ratio adjusting circuit；
The LED drive module is used to receive second pulse signal, and according to the second output of pulse signal LED
Driving signal.
LED backlight brightness regulating circuit provided by the invention, control processing module is according to the duty ratio setting letter received
Number the first pulse signal is generated, pulse output module exports the second arteries and veins after carrying out level conversion to the first pulse signal for receiving
Signal is rushed, duty ratio judgment module receives the second pulse signal, and judges whether the duty ratio of the second pulse signal is lower than setting
Duty ratio, the second pulse signal duty ratio lower than setting duty ratio when to duty ratio adjustment module send duty ratio tune
Entire signal exports the level value and the second pulse signal of high level after duty ratio adjustment module receives duty ratio adjustment signal
The identical third pulse signal of level value of high level made it higher than to be adjusted to the duty ratio of the second pulse signal
The duty ratio of setting guarantees that the duty ratio of the second pulse signal works normally within range of needs always situated in circuit, to mention
The stability and reliability of high circuit.
Detailed description of the invention
Fig. 1 is the structural schematic diagram of duty ratio adjusting circuit provided by the invention；
Fig. 2 is the circuit diagram of one embodiment of duty ratio adjusting circuit provided by the invention；
Fig. 3 is the circuit diagram of second embodiment of duty ratio adjusting circuit provided by the invention；
Fig. 4 is the circuit diagram of the third embodiment of duty ratio adjusting circuit provided by the invention；
Fig. 5 is the circuit diagram of the 4th embodiment of duty ratio adjusting circuit provided by the invention；
Fig. 6 is the structural schematic diagram of LED backlight brightness regulating circuit provided by the invention.
Specific embodiment
Following will be combined with the drawings in the embodiments of the present invention, and technical solution in the embodiment of the present invention carries out clear, complete
Site preparation description, it is clear that described embodiments are only a part of the embodiments of the present invention, instead of all the embodiments.It is based on
Embodiment in the present invention, it is obtained by those of ordinary skill in the art without making creative efforts every other
Embodiment shall fall within the protection scope of the present invention.
It is the structural schematic diagram of duty ratio adjusting circuit provided by the invention referring to Fig. 1.
The present invention provides a kind of duty ratio adjusting circuit, including pulse output module 1, duty ratio judgment module 2 and duty
Than adjusting module 3；
The pulse output module 1 is used to receive the first pulse signal of pulse input end input, to the first pulse signal
Level conversion is carried out, and exports the second pulse signal to pulse output end；
The duty ratio judgment module 2 is lower than in the duty ratio of the second pulse signal and sets for receiving the second pulse signal
When fixed duty ratio, duty ratio adjustment signal is sent to duty ratio adjustment module 3；
The duty ratio adjustment module 3 is used to receive the first pulse signal and duty ratio adjustment signal, and according to duty ratio
Adjustment signal export third pulse signal arrive pulse output end, wherein the level value of the high level of the third pulse signal and
The level value of the high level of second pulse signal is identical.
In the specific implementation, pulse output module 1 export after level conversion the to the first pulse signal for receiving
Two pulse signals, duty ratio judgment module 2 receives the second pulse signal, and judges whether the duty ratio of the second pulse signal is lower than
The duty ratio of setting, the second pulse signal duty ratio lower than setting duty ratio when, duty ratio judgment module 2 is to duty ratio
It adjusts module 3 and sends duty ratio adjustment signal, after duty ratio adjustment module 3 receives duty ratio adjustment signal, output high level
Level value third pulse signal identical with the level value of the high level of the second pulse signal, to be accounted for the second pulse signal
Empty ratio is adjusted, and makes it higher than the duty ratio of setting；When the duty ratio of the second pulse signal is higher than the duty ratio of setting, account for
Sky stops adjusting the transmission duty ratio adjustment signal of module 3 to duty ratio than judgment module 2, so that the second pulse signal keeps original to account for
Sky guarantees that the duty ratio of the second pulse signal works normally within range of needs always situated in circuit, to mention than normal output
The stability and reliability of high circuit.
Further, the pulse output module 1 includes first voltage comparing unit U1 and first diode D1；
The first voltage comparing unit U1 receives the first pulse signal, carries out level conversion to the first pulse signal, defeated
Second pulse signal out；
The first diode D1 is connect with the first voltage comparing unit U1, when the second pulse signal is high level
Conducting ends when the second pulse signal is low level.
Further, the duty ratio judgment module 2 includes first resistor R1, first capacitor C1 and switching tube Q；Described
One resistance R1 receives the second pulse signal, and exports the second pulse signal；The first capacitor C1 is connect with first resistor R1,
Second pulse signal stores electric energy when being high level；The switching tube Q is connect with first capacitor C1, reaches conducting in the electric energy
When voltage, switch to be connected by cut-off.
Wherein, when the second pulse signal is changed into low level from high level, the electric energy of first capacitor C1 storage does not still have
There is the conducting voltage for reaching switching tube Q, determines that duty ratio of the duty ratio lower than setting of the second pulse signal, duty ratio are sentenced at this time
Disconnected module 2 sends duty ratio adjustment signal to duty ratio adjustment module 3.
Further, the duty ratio adjustment module 3 compares including the second diode D2, the second capacitor C2, second voltage
Unit U2 and third diode D3；
The second diode D2 receives the first pulse signal, is connected when the first pulse signal is high level；
The second capacitor C2 is connect with the second diode D2, stores electric energy in the second diode D2 conducting, and described the
Two capacitor C2 receive duty ratio adjustment signal, discharge electric energy according to duty ratio adjustment signal；
The second voltage comparing unit U2 is connect with the second capacitor C2, when electric energy reaches predeterminated voltage, exports high electricity
Ordinary mail number；
The third diode D3 is connect with second voltage comparing unit U2, is led when third pulse signal is high level
It is logical, end when third pulse signal is low level.
Referring to fig. 2, be duty ratio adjusting circuit provided by the invention one embodiment circuit diagram.Such as Fig. 2
Shown, the pulse output module 1 includes first voltage comparing unit U1 and first diode D1；
Non-inverting input terminal+the VI1 of the first voltage comparing unit U1 is described for connecting pulse input end PWM-IN
Inverting input terminal-the VI1 of first voltage comparing unit U1 is for connecting reference voltage Vref, the first voltage comparing unit
The anode of the output end Out1 and first diode D1 of U1 are connect, the cathode and duty ratio judgment module of the first diode D1
2 connections, the cathode of the first diode D1 are also used to connect pulse output end PWM-OUT.
It should be noted that non-inverting input terminal+VI1 the first pulse signal of reception of first voltage comparing unit U1, first
Inverting input terminal-the VI1 of voltage comparison unit U1 receives reference voltage Vref, when the first pulse signal PWM-IN is greater than reference
When voltage Vref, first voltage comparing unit U1 exports high level signal by output end Out1, and first diode D1 is led at this time
It is logical；When the first pulse signal PWM-IN is less than reference voltage Vref, first voltage comparing unit U1 is defeated by output end Out1
Low level signal out, first diode D1 ends at this time.
It is the circuit diagram of second embodiment of duty ratio adjusting circuit provided by the invention referring to Fig. 3.Such as Fig. 3
Shown, the duty ratio judgment module 2 includes first resistor R1, first capacitor C1 and switching tube Q；
The first end of the switching tube Q is connect with duty ratio adjustment module 3, the second end ground connection of the switching tube Q, described
The control terminal of switching tube Q is separately connected the second end of first resistor R1 and the first end of first capacitor C1, the first capacitor C1
Second end ground connection, the first end of the first resistor R1 connect with pulse output module 1.
It should be noted that first resistor R1 receives the second pulse signal, when the second pulse signal is high level, pass through
First resistor R1 is first capacitor C1 charging, when the second pulse signal is changed into low level from high level, first capacitor C1 two
When the voltage at end is still not up to the conducting voltage of switching tube Q, switching tube Q cut-off determines the duty of the second pulse signal at this time
Than the duty ratio lower than setting, duty ratio judgment module 2 sends duty ratio adjustment signal to duty ratio adjustment module 3；When second
When pulse signal is still in high level, the voltage at the both ends first capacitor C1 reaches the conducting voltage of switching tube Q, and switching tube is connected,
Determine that the duty ratio of the second pulse signal is higher than the duty ratio of setting at this time, duty ratio judgment module 2 stops adjusting to duty ratio
Module 3 sends duty ratio adjustment signal.Wherein, start to charge to first capacitor C1 until first capacitor C1 by first resistor R1
Both end voltage reach the conducting voltage of switching tube Q time be setting duty ratio high level duration, can pass through
The capacitance of the resistance value and first capacitor C1 that change first resistor R1 sets the minimum duty cycle of permission.
Further, the duty ratio judgment module 2 further includes the 4th diode D4；
The anode of the 4th diode D4 is connect with the second end of the first resistor R1, the 4th diode D4's
Cathode is connect with the first end of the first resistor R1.
It should be noted that the electric energy on first capacitor C1 can pass through the 4th when the second pulse signal is low level
Diode D4 is quickly released, so that the electric energy on first capacitor C1 can be discharged into zero before the arrival of next high level,
To avoid when the duty ratio of next second pulse signal being caused to be less than the duty ratio of setting, the second pulse signal cannot be accounted for
Sky is adjusted than accurately, minimum duty cycle distortion phenomenon occurs.
Preferably, the switching tube Q is NPN type triode, the of the current collection of the NPN type triode extremely switching tube Q
One end, the transmitting extremely second end of switching tube Q of the NPN type triode, the base stage of the NPN type triode is switching tube Q
Control terminal.
Referring to fig. 4, be duty ratio adjusting circuit provided by the invention third embodiment circuit diagram.Such as Fig. 4
Shown, the duty ratio judgment module 2 further includes second resistance R2；
The switching tube Q is N-channel MOS pipe, and the drain electrode of the N-channel MOS pipe is the first end of switching tube Q, the N ditch
The source electrode of road metal-oxide-semiconductor is the second end of switching tube Q, and the grid of the N-channel MOS pipe is the control terminal of switching tube Q；
The first end of the second resistance R2 is connect with the grid of N-channel MOS pipe, the second termination of the second resistance R2
Ground.
It is the circuit diagram of the 4th embodiment of duty ratio adjusting circuit provided by the invention referring to Fig. 5.Such as Fig. 5
Shown, the duty ratio adjustment module 3 includes the second diode D2, the second capacitor C2, second voltage comparing unit U2 and third
Diode D3；
For the anode of the second diode D2 for connecting pulse input end PWM-IN, the second diode D2's is negative
Pole is separately connected the first end of the non-inverting input terminal+VI2 and the second capacitor C2 of second voltage comparing unit U2, the second voltage
Inverting input terminal-the VI2 of comparing unit U2 is for connecting reference voltage Vref, the output of the second voltage comparing unit U2
The anode of end Out2 and third diode D3 are connect, the cathode connection pulse output module 1 of the third diode D3, and described the
The first end of two capacitor C2 connects duty ratio judgment module 2, the second end ground connection of the second capacitor C2.
It should be noted that the second diode D2 receives the first pulse signal, when the first pulse signal is high level, the
Two diode D2 conducting is that the second capacitor C2 charges, when the voltage at the second both ends capacitor C2 is higher than second voltage comparing unit U2's
When the received reference voltage Vref of inverting input terminal-VI2, second voltage comparing unit U2 exports high level signal.When the first arteries and veins
Rush signal be low level when, the second diode D2 cut-off, if the second capacitor C2 receives duty ratio adjustment signal at this time, to
Non-inverting input terminal+the VI2 of second voltage comparing unit U2 discharges electric energy, so that second voltage comparing unit U2 continues to output high electricity
Ordinary mail number adjusts the duty ratio of the second pulse signal；If the second capacitor C2 is not received by duty ratio adjustment signal at this time,
Second capacitor C2 does not discharge electric energy to the non-inverting input terminal+VI2 of second voltage comparing unit U2, then second voltage comparing unit U2
Low level, third transistor D3 cut-off are exported, the second pulse signal keeps former duty ratio normally to export.
Further, the duty ratio adjustment module 3 further includes 3rd resistor R3, and the anode of the second diode D2 is used
In connection pulse input end PWM-IN, specifically: the second diode D2 pass through 3rd resistor R3 connection pulse input end
PWM-IN.Wherein, 3rd resistor R3 is current-limiting resistance.
It is the structural schematic diagram of LED backlight brightness regulating circuit provided by the invention referring to Fig. 6.
The present invention provides a kind of LED backlight brightness regulating circuit, including control processing module 4, duty ratio adjusting circuit and
LED drive module 5；
The control processing module 4 generates for receiving duty ratio setting signal, according to the duty ratio setting signal
One pulse signal；
The duty ratio adjusting circuit is foregoing duty ratio adjusting circuit；
The LED drive module 5 is used to receive second pulse signal, and according to second output of pulse signal
LED drive signal.
When it is implemented, control processing module 3 receives duty ratio setting signal, the is generated according to the duty ratio setting signal
One pulse signal, pulse output module 1 export the second pulse signal after carrying out level conversion to the first pulse signal received,
Duty ratio judgment module 2 receives the second pulse signal, and judges whether the duty ratio of the second pulse signal is lower than the duty of setting
Than when the duty ratio of the second pulse signal is lower than the duty ratio set, duty ratio judgment module 2 adjusts module 3 to duty ratio
Send duty ratio adjustment signal, after duty ratio adjustment module 3 receives duty ratio adjustment signal, export the level value of high level with
The identical third pulse signal of the level value of the high level of second pulse signal, to be adjusted to the duty ratio of the second pulse signal
It is whole, make it higher than the duty ratio of setting；When the duty ratio of the second pulse signal is higher than the duty ratio of setting, duty ratio judges mould
Block 2 stops adjusting the transmission duty ratio adjustment signal of module 3 to duty ratio, so that the second pulse signal keeps former duty ratio normally defeated
Out, LED drive module 5 receives second pulse signal, and is driven according to the second output of pulse signal LED drive signal
LED light group ensure that the duty ratio of the second pulse signal works normally range of needs always situated in LED backlight brightness regulating circuit
Within, to improve the stability and reliability of circuit.
It should be noted that switching tube Q both can be NPN type three in duty ratio judgment module 3 provided by the above embodiment
Pole pipe, or N-channel MOS pipe is two kinds of embodiments therein, and in other embodiments, switching tube Q can also be replaced
It is changed to P-channel metal-oxide-semiconductor or other three ports for control switching devices or it derives from device, in different applications, depending on practical electricity
The power consumption on road, cost, driving power and reasonable selection and setting are required with the drive control component parameter matching of switching tube etc.,
It selects and setting switching tube is the conventional design process of the prior art, herein without repeating.
Duty ratio adjusting circuit provided by the invention and LED backlight brightness regulating circuit, pulse output module is to receiving
The first pulse signal carry out level conversion after export the second pulse signal, duty ratio judgment module receives the second pulse signal,
And judge whether the duty ratio of the second pulse signal is lower than the duty ratio of setting, it is lower than setting in the duty ratio of the second pulse signal
Duty ratio when to duty ratio adjustment module send duty ratio adjustment signal, duty ratio adjustment module receive duty ratio adjustment letter
After number, the level value third pulse signal identical with the level value of the high level of the second pulse signal of high level is exported, next pair
The duty ratio of second pulse signal is adjusted, and makes it higher than the duty ratio of setting, guarantees the duty ratio one of the second pulse signal
Directly it is located at circuit to work normally within range of needs, to improve the stability and reliability of circuit.
The above is a preferred embodiment of the present invention, it is noted that for those skilled in the art
For, various improvements and modifications may be made without departing from the principle of the present invention, these improvements and modifications are also considered as
Protection scope of the present invention.
Claims (11)
1. a kind of duty ratio adjusting circuit, which is characterized in that including pulse output module, duty ratio judgment module and duty ratio tune
Mould preparation block；
The pulse output module be used for receive pulse input end input the first pulse signal, to first pulse signal into
Line level conversion, and the second pulse signal is exported to pulse output end；The pulse output module includes that first voltage is more single
Member and first diode；The first voltage comparing unit receives first pulse signal, to first pulse signal into
Line level conversion, exports the second pulse signal；The first diode is connect with the first voltage comparing unit, described
Two pulse signals are connected when being high level, end when second pulse signal is low level；
The duty ratio judgment module is lower than for receiving second pulse signal in the duty ratio of second pulse signal
When the duty ratio of setting, Xiang Suoshu duty ratio adjusts module and sends duty ratio adjustment signal；
The duty ratio adjustment module is used to receive first pulse signal and the duty ratio adjustment signal, and according to described
Duty ratio adjustment signal exports third pulse signal to the pulse output end, wherein the high level of the third pulse signal
Level value it is identical as the level value of high level of second pulse signal.
2. duty ratio adjusting circuit as described in claim 1, which is characterized in that the duty ratio judgment module includes the first electricity
Resistance, first capacitor and switching tube；
The first resistor receives second pulse signal, and exports second pulse signal；
The first capacitor is connect with the first resistor, stores electric energy when second pulse signal is high level；
The switching tube is connect with the first capacitor, when the electric energy reaches conducting voltage, switchs to be connected by cut-off.
3. duty ratio adjusting circuit as described in claim 1, which is characterized in that the duty ratio adjustment module includes the two or two
Pole pipe, the second capacitor, second voltage comparing unit and third diode；
Second diode receives first pulse signal, is connected when first pulse signal is high level；
Second capacitor is connect with second diode, stores electric energy in second diode current flow, and described second
Capacitor receives the duty ratio adjustment signal, discharges electric energy according to the duty ratio adjustment signal；
The second voltage comparing unit and second capacitance connection export high electricity when the electric energy reaches predeterminated voltage
Ordinary mail number；
The third diode is connect with the second voltage comparing unit, is led when the third pulse signal is high level
It is logical, end when the third pulse signal is low level.
4. duty ratio adjusting circuit as described in claim 1, which is characterized in that the first voltage comparing unit it is same mutually defeated
Enter end for connecting pulse input end, the inverting input terminal of the first voltage comparing unit is described for connecting reference voltage
The anode of the output end of first voltage comparing unit and the first diode is connect, the cathode of the first diode with it is described
The connection of duty ratio judgment module, the cathode of the first diode are also used to connect pulse output end.
5. duty ratio adjusting circuit as claimed in claim 2, which is characterized in that the duty ratio judgment module includes the first electricity
Resistance, first capacitor and switching tube；
The first end of the switching tube is connect with duty ratio adjustment module, the second end ground connection of the switching tube, described to open
The control terminal for closing pipe is separately connected the second end of the first resistor and the first end of the first capacitor, the first capacitor
Second end ground connection, the first end of the first resistor are connect with the pulse output module.
6. duty ratio adjusting circuit as claimed in claim 5, which is characterized in that the duty ratio judgment module further includes the 4th
Diode；
4th diode anode connect with the second end of the first resistor, the cathode of the 4th diode with it is described
The first end of first resistor connects.
7. such as duty ratio adjusting circuit described in claim 5 or 6, which is characterized in that the switching tube is NPN type triode,
The first end of the extremely described switching tube of the current collection of the NPN type triode, the extremely described switch of the transmitting of the NPN type triode
The second end of pipe, the base stage of the NPN type triode are the control terminal of the switching tube.
8. such as duty ratio adjusting circuit described in claim 5 or 6, which is characterized in that the duty ratio judgment module further includes
Second resistance；
The switching tube is N-channel MOS pipe, and the drain electrode of the N-channel MOS pipe is the first end of the switching tube, the N-channel
The source electrode of metal-oxide-semiconductor is the second end of the switching tube, and the grid of the N-channel MOS pipe is the control terminal of the switching tube；
The first end of the second resistance is connect with the grid of the N-channel MOS pipe, the second end ground connection of the second resistance.
9. duty ratio adjusting circuit as claimed in claim 3, which is characterized in that the duty ratio adjustment module includes the two or two
Pole pipe, the second capacitor, second voltage comparing unit and third diode；
For the anode of second diode for connecting pulse input end, the cathode of second diode is separately connected described the
The reverse phase of the first end of the non-inverting input terminal of two voltage comparison units and second capacitor, the second voltage comparing unit is defeated
Enter end and connect for connecting reference voltage, the output end of the second voltage comparing unit with the anode of the third diode,
The cathode of the third diode connects the pulse output module, and the first end of second capacitor connects the duty ratio and sentences
Disconnected module, the second end ground connection of second capacitor.
10. duty ratio adjusting circuit as claimed in claim 9, which is characterized in that duty ratio adjustment module further includes the
Three resistance, the anode of second diode for connecting pulse input end, specifically: second diode passes through described the
Three resistance connect pulse input end.
11. a kind of LED backlight brightness regulating circuit, which is characterized in that including control processing module, duty ratio adjusting circuit and
LED drive module；
The control processing module generates the first pulse for receiving duty ratio setting signal, according to the duty ratio setting signal
Signal；
The duty ratio adjusting circuit is duty ratio adjusting circuit as described in any one of claim 1 to 10；
The LED drive module drives for receiving second pulse signal, and according to the second output of pulse signal LED
Signal.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201710368290.9A CN107221293B (en) | 2017-05-23 | 2017-05-23 | Duty ratio regulating circuit and LED backlight brightness regulating circuit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201710368290.9A CN107221293B (en) | 2017-05-23 | 2017-05-23 | Duty ratio regulating circuit and LED backlight brightness regulating circuit |
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| CN107221293A CN107221293A (en) | 2017-09-29 |
| CN107221293B true CN107221293B (en) | 2019-09-03 |
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| CN109119014B (en) * | 2018-09-07 | 2021-11-12 | 京东方科技集团股份有限公司 | Voltage output circuit, temperature compensation circuit and display device |
| US11032886B2 (en) * | 2019-07-31 | 2021-06-08 | Novatek Microelectronics Corp. | Light emitting diode driver and driving method thereof |
| CN112382241B (en) * | 2020-11-10 | 2022-03-25 | 昆山龙腾光电股份有限公司 | Backlight driving circuit, backlight driving control method and display device |
| CN113179096B (en) * | 2021-04-25 | 2023-07-14 | 珠海格力电器股份有限公司 | Delay circuit, motor device and motor system |
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| CN102708804A (en) * | 2011-10-21 | 2012-10-03 | 京东方科技集团股份有限公司 | Backlight dimming method and backlight driving circuit |
| CN103582226A (en) * | 2012-08-08 | 2014-02-12 | 群康科技(深圳)有限公司 | Dimming circuit and dimming method thereof |
| CN105096843A (en) * | 2015-08-19 | 2015-11-25 | 京东方科技集团股份有限公司 | Backlight source, adjustment method and adjustment device thereof and display device |
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| US8581828B2 (en) * | 2010-04-30 | 2013-11-12 | Atmel Corporation | Load-aware compensation in light-emitting-diode backlight illumination systems |
| TWI475553B (en) * | 2013-04-29 | 2015-03-01 | Wistron Corp | Backlight control module and backlight control method |
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| CN102708804A (en) * | 2011-10-21 | 2012-10-03 | 京东方科技集团股份有限公司 | Backlight dimming method and backlight driving circuit |
| CN103582226A (en) * | 2012-08-08 | 2014-02-12 | 群康科技(深圳)有限公司 | Dimming circuit and dimming method thereof |
| CN105096843A (en) * | 2015-08-19 | 2015-11-25 | 京东方科技集团股份有限公司 | Backlight source, adjustment method and adjustment device thereof and display device |
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