CN111883068A - LCD screen constant current drive circuit that is shaded - Google Patents
LCD screen constant current drive circuit that is shaded Download PDFInfo
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- CN111883068A CN111883068A CN202010558437.2A CN202010558437A CN111883068A CN 111883068 A CN111883068 A CN 111883068A CN 202010558437 A CN202010558437 A CN 202010558437A CN 111883068 A CN111883068 A CN 111883068A
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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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- 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
- G09G3/3413—Details of control of colour illumination sources
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Abstract
The invention relates to a backlight constant current driving circuit of an LCD (liquid crystal display) screen, which comprises a backlight module, a driving module, a second power supply terminal VCC2 connected with the backlight module, a first power supply terminal VCC1 connected with the driving module, and a backlight control terminal connected with the driving module, wherein the backlight control terminal is connected with a control chip. The backlight module comprises a plurality of strings of LED lamps and a capacitor C1, wherein the anode of each string of LED lamps is connected with a second power supply terminal VCC 2. The driving module comprises a plurality of backlight driving circuits, a backlight stabilizing circuit and a backlight control circuit, one end of the backlight stabilizing circuit is connected with the first power supply terminal VCC1, the other end of the backlight stabilizing circuit is connected with the input ends of the backlight driving circuits, one end of the backlight control circuit is connected with the control chip, the other end of the backlight control circuit is connected with the control ends of the backlight driving circuits, and the output end of each backlight driving circuit is connected with the cathode of each string of LED lamps. The invention adopts the design of discrete components, and has simple circuit, lower cost and better EMC performance.
Description
Technical Field
The invention relates to the technical field of backlight driving, in particular to a constant current driving circuit for backlight of an LCD screen.
Background
Currently, most of backlight driving schemes for LCD panels use an LED driver chip integrated with a DC-DC converter to drive the LCD backlight, and the scheme is to drive the LED with a constant voltage.
The existing constant voltage driving LED has the following defects:
(1) the circuit design is complex, and the PCB layout design is complex;
(2) the design of driving software is more complex;
(3) the cost is high;
(4) EMC (i.e., electromagnetic compatibility) performance is poor.
In order to solve the problems, the invention provides an LCD screen backlight constant current driving circuit.
Disclosure of Invention
The invention aims to solve the problems of complex circuit design, complex PCB layout design, complex driving software design, high cost and poor EMC performance of the conventional constant-voltage driving LED. The concrete solution is as follows:
a constant current drive circuit in a poor light of LCD screen, including backlight module, the drive module who is connected with backlight module, the second power supply VCC2 who is connected with backlight module, the first power supply VCC1 who is connected with drive module, the control end in a poor light that is connected with drive module, the control end in a poor light is connected with control chip.
The backlight module comprises a plurality of strings of LED lamps and a capacitor C1, one end of the capacitor C1 is connected with a second power supply end VCC2, the other end of the capacitor C1 is grounded, the anode of each string of LED lamps is connected with the second power supply end VCC2, and the cathode of each string of LED lamps is connected with a plurality of output ends of the driving module respectively.
The driving module comprises a plurality of backlight driving circuits, a backlight stabilizing circuit and a backlight control circuit, one end of the backlight stabilizing circuit is connected with the first power supply end VCC1, the other end of the backlight stabilizing circuit is connected with the input ends of the backlight driving circuits, one end of the backlight control circuit is connected with the control chip, the other end of the backlight control circuit is connected with the control ends of the backlight driving circuits, and the output end of each backlight driving circuit is connected with the cathode of each string of LED lamps.
Furthermore, each string of the LED lamps is connected in series with more than two LED lamp beads, and the anode of each LED lamp bead is connected with the cathode of the other LED lamp bead.
Further, the backlight stabilizing circuit comprises a capacitor C2 with one end connected with the first power supply terminal VCC1 and the other end grounded, a resistor R1 with one end connected with the first power supply terminal VCC1 and the other end connected with the C pole of the stabilizing triode Q1, a resistor R2 with one end connected with the e pole of the stabilizing triode Q1 and the other end grounded, and a b pole of the stabilizing triode Q1 is connected with the C pole.
Further, the backlight control circuit comprises a resistor R7 with one end connected with the control chip and the other end connected with the b pole of the control triode Qt, a capacitor C3 with one end connected with the b pole of the control triode Qt and the other end grounded, a resistor R8 with one end connected with the b pole of the control triode Qt and the other end grounded, and an e pole of the control triode Qt grounded.
Further, the backlight driving circuit comprises a plurality of driving triodes Qn, wherein one end of each driving triode Qn is connected with the e pole of each driving triode Qn, the other end of each driving triode Qn is connected with a plurality of resistors Rn of the c pole of the control triode Qt, n is any natural number, the b pole of each driving triode Qn is simultaneously connected with the b pole of the stabilizing triode Q1, and the c pole of each driving triode Qn is respectively connected with the cathode of each string of the LED lamps.
Further, the stabilizing transistor Q1 has the function of automatically adjusting the c-pole current of each driving transistor Qn to be stable and constant when the ambient temperature increases or decreases.
Further, the driving transistor Qn operates in a constant current driving mode, and when the second power supply terminal VCC2 changes, the brightness of each string of LED lamps is maintained.
Further, the control triode Qt turns on each string of LED lamps when the control chip outputs a high level, turns off each string of LED lamps when the control chip outputs a low level, and controls the brightness of each string of LED lamps to increase or decrease when the control chip outputs PWM pulse width modulation signals of different duty ratios.
Furthermore, the resistor R7 and the resistor R8 form a voltage dividing circuit, and the capacitor C3 is a high-frequency filter capacitor.
Further, the capacitor C1 and the capacitor C2 are power filter capacitors of the first power supply terminal VCC1 and the second power supply terminal VCC2, respectively, and the resistor R1 is a current-limiting resistor.
In summary, the technical scheme of the invention has the following beneficial effects:
the invention solves the problems of more complex circuit design, more complex PCB layout design, more complex driving software design, higher cost and poorer EMC performance of the conventional constant-voltage driving LED. The invention adopts a constant current driving mode, adopts a discrete component design, and has the advantages of simple circuit, lower cost, better EMC performance, higher innovation and stronger practicability. The invention is not only suitable for LCD backlight drive, but also suitable for alarm lamp drive and atmosphere lamp drive. The stabilizing triode Q1 has the function of automatically adjusting the c pole current of each driving triode Qn to be stable and unchangeable when the ambient temperature rises or falls, drives the triode Qn to work in a constant current driving mode, and maintains the brightness of each string of LED lamps unchanged when the second power supply end VCC2 changes. In embodiment 1 of the present invention, the backlight module only shows 4 strings of LED lamps, and actually, the number of LED lamp strings can be increased or decreased according to the LCD backlight requirement, and the number of LED lamps in each string can be increased or decreased, thereby expanding the application range thereof.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
FIG. 1 is a circuit diagram of a backlight constant current driving circuit of an LCD panel according to the present invention;
fig. 2 is a circuit diagram of embodiment 1 of the present invention.
Description of reference numerals:
the backlight driving circuit comprises a backlight module 1, a backlight module 2, a backlight driving circuit 21, a backlight stabilizing circuit 22, a backlight control circuit 23, a VCC1, a first power supply end, a VCC2, a second power supply end, an EN backlight control end, a Q1 backlight stabilizing triode, a Qt backlight control triode and a Qn backlight driving triode.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, the LCD backlight constant current driving circuit includes a backlight module 1, a driving module 2 connected to the backlight module 1, a second power supply terminal VCC2 connected to the backlight module 1, a first power supply terminal VCC1 connected to the driving module 2, and a backlight control terminal EN connected to the driving module 2, where the backlight control terminal EN is connected to a control chip (not shown in the figure).
The backlight module 1 includes a plurality of strings of LED lamps (for example, n strings), a capacitor C1, one end of the capacitor C1 is connected to the second power supply terminal VCC2, the other end of the capacitor C1 is grounded, the anode of each string of LED lamps is connected to the second power supply terminal VCC2, and the cathode of each string of LED lamps is connected to a plurality of output terminals of the driving module 2 (i.e., the collector C of the backlight driving transistor Qn).
The driving module 2 includes a plurality of backlight driving circuits 21, a backlight stabilizing circuit 22, and a backlight control circuit 23, wherein one end of the backlight stabilizing circuit 22 is connected to the first power supply VCC1, the other end of the backlight stabilizing circuit 22 is simultaneously connected to the input terminals of the plurality of backlight driving circuits 21 (i.e., the base terminal b of the backlight driving transistor Qn), one end of the backlight control circuit 23 is connected to the control chip, and the other end of the backlight control circuit 23 is simultaneously connected to the control terminals of the plurality of backlight driving circuits 21 (i.e., the other end of the resistor Rn connected to the emitter e of the backlight driving transistor Qn), and the output terminal of each backlight driving circuit (i.e., the collector terminal c of the backlight driving transistor Qn) is respectively connected to the cathodes of each string of LED lamps.
Furthermore, each string of LED lamps has more than two LED lamp beads (one LED lamp bead is an LED light emitting diode) connected in series, and the anode of each LED lamp bead is connected to the cathode of another LED lamp bead.
Further, the backlight stabilizing circuit 22 includes a capacitor C2 having one end connected to the first power supply terminal VCC1 and the other end grounded, a resistor R1 having one end connected to the first power supply terminal VCC1 and the other end connected to the C pole of the stabilizing transistor Q1, a resistor R2 having one end connected to the e pole of the stabilizing transistor Q1 and the other end grounded, and the b pole of the stabilizing transistor Q1 is connected to the C pole.
Further, the backlight control circuit 23 includes a resistor R7 having one end connected to the control chip and the other end connected to the b-pole of the control transistor Qt, a capacitor C3 having one end connected to the b-pole of the control transistor Qt and the other end grounded, a resistor R8 having one end connected to the b-pole of the control transistor Qt and the other end grounded, and an e-pole of the control transistor Qt grounded.
Further, the backlight driving circuit 21 includes a plurality of driving transistors Qn, one end of each driving transistor Qn is connected to the e-pole of each driving transistor Qn, the other end of each driving transistor Qn is connected to the c-pole of the control transistor Qt, where n is any natural number, the b-pole of each driving transistor Qn is simultaneously connected to the b-pole of the stabilizing transistor Q1, and the c-pole of each driving transistor Qn is respectively connected to the cathode of each string of LED lamps.
Further, the stabilizing transistor Q1 has the function of automatically adjusting the c-pole current of each driving transistor Qn to be stable and constant when the ambient temperature increases or decreases. (auspicious see the detailed description in example 1)
Further, the driving transistor Qn operates in a constant current driving mode, and when the second power supply terminal VCC2 changes, the brightness of each string of LED lamps is maintained. (auspicious see the detailed description in example 1)
Further, the triode Qt is controlled to turn on each string of LED lamps when the control chip outputs a high level, turn off each string of LED lamps when the control chip outputs a low level, and control the brightness of each string of LED lamps to increase or decrease when the control chip outputs PWM pulse width modulation signals of different duty ratios. (auspicious see the detailed description in example 1)
Further, the resistor R7 and the resistor R8 form a voltage dividing circuit, and the capacitor C3 is a high-frequency filter capacitor.
Further, the capacitor C1 and the capacitor C2 are power filter capacitors of the first power supply terminal VCC1 and the second power supply terminal VCC2, respectively, and the resistor R1 is a current-limiting resistor.
Example 1:
as shown in fig. 2, the embodiment is described as follows:
1. description of circuit composition modules: the circuit is composed of a backlight module 1 and a driving module 2, wherein the backlight module 1 is used for providing backlight for the LCD screen, and the driving module 2 is used for providing constant current driving for the backlight LED.
2. Description of circuit elements: c1, C2 and C3 are capacitors, D1, D2, D3, D4, D5, D6, D7 and D8 are light emitting diodes (LED beads), R1, R2, R3, R4, R5, R6, R7 and R8 are resistors, Q1, Q2, Q3, Q4, Q5 and Qt are NPN-type triodes of the same type, VCC1 is a power supply (i.e., a first power supply terminal) of the driving module 2, VCC2 is a power supply (i.e., a second power supply terminal) of the backlight module 1, and EN is an LCD backlight enable signal (i.e., a backlight control terminal), which is controlled (i.e., a control chip) by an MCU (microprocessor, not shown in the figure). Q1 is a backlight stabilizing transistor, Q2, Q3, Q4, Q5 are backlight driving transistors (i.e., Qn), and Qt is a backlight control transistor.
3. Description of circuit signal connection:
(1) the backlight module 1 is connected with signals: one end of the capacitor C1 is connected to a power supply VCC2, and the other end is grounded; the anode of LED D1 is connected to the power supply VCC2, and the cathode thereof is connected to the anode of LED D2; the cathode of the LED D2 is connected to the collector c of the transistor Q2 in the driving module 2; the anode of LED D3 is connected to the power supply VCC2, and the cathode thereof is connected to the anode of LED D4; the cathode of the LED D4 is connected to the collector c of the transistor Q3 in the driving module 2; the anode of LED D5 is connected to a power supply VCC2, and its cathode is connected to the anode of LED 6; the cathode of the LED D6 is connected to the collector c of the transistor Q4 in the driving module 2; the anode of LED D7 is connected to the power supply VCC2, and the cathode thereof is connected to the anode of LED D8; the cathode of the LED D8 is connected to the collector c of the transistor Q5 in the driving module 2;
(2) the driving module 2 is connected with signals: one end of the capacitor C2 is connected to a power supply VCC1, and the other end is grounded; one end of the resistor R1 is connected to a power supply VCC1, and the other end is connected to the collector c of the triode Q1; the base b of the transistor Q1 is connected to the collector c of the transistor Q1; one end of the resistor R2 is connected to the emitter e of the triode Q1, and the other end is grounded; the base b of the transistor Q2 is connected to the collector c of the transistor Q1; one end of the resistor R3 is connected to the emitter e of the transistor Q2, and the other end thereof is connected to the collector c of the transistor Qt; the base b of the transistor Q3 is connected to the collector c of the transistor Q1; one end of the resistor R4 is connected to the emitter e of the transistor Q3, and the other end thereof is connected to the collector c of the transistor Qt; the base b of the transistor Q4 is connected to the collector c of the transistor Q1; one end of the resistor R5 is connected to the emitter e of the transistor Q4, and the other end thereof is connected to the collector c of the transistor Qt; the base b of the transistor Q5 is connected to the collector c of the transistor Q1; one end of the resistor R6 is connected to the emitter e of the transistor Q5, and the other end thereof is connected to the collector c of the transistor Qt; one end of the resistor R7 is connected to the LCD backlight enable signal EN (i.e., the backlight control end), and the other end thereof is connected to the base b of the transistor Qt; one end of the capacitor C3 is connected to the base b of the triode Qt, and the other end is grounded; one end of the resistor R8 is connected to the base b of the triode Qt, and the other end is grounded; the emitter e of the transistor Qt is grounded.
4. Description of the working principle of the circuit:
(1) the working principle of turning on the backlight of the LCD screen is as follows: when the system is powered on, if the MCU receives a command of turning on the backlight of the LCD screen, the MCU enables the EN signal to output a high level, the high level is transmitted to a base electrode b of the triode Qt after being subjected to R7 and R8 voltage division and C3 filtering, so that the triode Qt is in saturated conduction, and at the moment, the ends of the resistors R3, R4, R5 and R6, which are connected with a collector electrode C of the triode Qt, are equivalent to the ground; meanwhile, after a power supply VCC1 is electrified, the power supply VCC1 is filtered by a capacitor C2, then is limited by a resistor R1 and is respectively transmitted to a collector C and a base b of a triode Q1, a base b of a triode Q2, a base b of a triode Q3, a base b of a triode Q4 and a base b of a triode Q5, so that triodes Q1, Q2, Q3, Q4 and Q5 are all conducted, and then light emitting diodes D1, D2, D3, D4, D5, D6, D7 and D8 are all conducted at the same time, and then the LCD screen backlight is turned on; if the voltage of the base b of the transistor Q1 is Vb and the emitter junction voltage of the transistors Q1, Q2, Q3, Q4 and Q5 is Vbe, the emitter e current Ie2 of the transistor Q2 is (Vb-Vbe)/R3, because the voltage of Vb is determined by the power supply VCC1, the resistor R1, the emitter junction voltage Vbe of the transistor Q1 and the resistor R2, and the values of the power supply VCC1, the resistor R1, the emitter junction voltage Vbe of the transistor Q1 and the resistor R2 are fixed, Vb will not change, and because the values of the emitter junction voltage Vbe and R3 do not change, Ie2 will not change, and the current flowing through the light emitting diodes D1 and D2 is approximately equal to Ie2, so that the current flowing through the light emitting diodes D1 and D2 will not change when the power supply VCC2 changes, and is always about Ie2 (Vb-R3)/R29; similarly, when the power supply VCC2 changes, the current flowing through the leds D3 and D4 is always about Ie3 ═ Vb-Vbe/R4, the current flowing through the leds D5 and D6 is always about Ie4 ═ Vb-Vbe/R5, and the current flowing through the leds D7 and D8 is always about Ie5 ═ Vb/R6; the LCD backlight driving circuit is a constant current driving circuit, and when the backlight power supply VCC2 of the LCD panel changes, the brightness of the LCD panel will not change. If the brightness of the LCD screen needs to be adjusted, the EN signal can be enabled to output a PWM (Pulse Width Modulation) signal with a certain duty ratio through the MCU (Pulse Width Modulation is an abbreviation of Pulse Width Modulation, and Chinese means Pulse Width Modulation for short).
(2) The working principle of turning off the backlight of the LCD screen is as follows: when the system is powered on, if the MCU receives a command to turn off the backlight of the LCD panel, the MCU enables the EN signal to output a low level, and the low level is divided by R7 and R8 and filtered by C3 and then transmitted to the base b of the transistor Qt, so that the transistor Qt is not turned on, and at this time, the transistors Q2, Q3, Q4 and Q5 cannot be turned on, so the leds D1, D2, D3, D4, D5, D6, D7 and D8 cannot be turned on, and the backlight of the LCD panel is turned off at this time.
(3) The working principle that the brightness of the LCD screen keeps unchanged when the ambient temperature changes is as follows: let the collector current flowing through the transistor Q1 be Ic1, the base current of the transistor Q1 be Ib1, the base b voltage of the transistor Q1 be Vb, the current flowing through the leds D1 and D2 be Ic2 (i.e., the collector c current of Q2), the base current of the transistor Q2 be Ib2, β be the dc amplification factor of the transistors Q1 to Q5, when the backlight of the LCD screen is lighted, Ic1 ═ beta ═ Ib1, Ic2 ═ beta ═ Ib2, Ic3 ═ beta ═ Ib3 … …, when the ambient temperature increases, the value of beta becomes larger, which results in that the value of Ic1 beta Ib1 becomes larger, and similarly Ic2 becomes larger, since Ic1 becomes larger, the voltage VR 1-Ic 1-R1 on resistor R1 also becomes larger, and then the value Vb-VCC 1-VR1 becomes smaller, and the value Vb becomes smaller, so that the value Ib2 becomes smaller, and the value of Ic2(β -Ib 2) becomes smaller, therefore, when the ambient temperature rises, the value of Ic2 will automatically adjust to achieve stability, i.e. the current Ic2 of the leds D1 and D2 is not changed; similarly, the current Ic3 of the leds D3 and D4 is unchanged, … …, when the ambient temperature decreases, the change process of the relevant current and voltage is opposite to the change process when the temperature increases, so that the current Ic2 of the leds D1 and D2 is also unchanged. Similarly, the current Ic3 of the leds D3 and D4 is unchanged, … …, and therefore, when the ambient temperature increases or decreases, the current flowing through the leds D3 to D8 is also unchanged. Therefore, when the ambient temperature changes, the current of all the light emitting diodes will remain unchanged, i.e. the brightness of the LCD screen remains unchanged.
In summary, the technical scheme of the invention has the following beneficial effects:
the invention solves the problems of more complex circuit design, more complex PCB layout design, more complex driving software design, higher cost and poorer EMC performance of the conventional constant-voltage driving LED. The invention adopts a constant current driving mode, adopts a discrete component design, and has the advantages of simple circuit, lower cost, better EMC performance, higher innovation and stronger practicability. The invention is not only suitable for LCD backlight drive, but also suitable for alarm lamp drive and atmosphere lamp drive. The stabilizing triode Q1 has the function of automatically adjusting the c pole current of each driving triode Qn to be stable and unchangeable when the ambient temperature rises or falls, drives the triode Qn to work in a constant current driving mode, and maintains the brightness of each string of LED lamps unchanged when the second power supply end VCC2 changes. In embodiment 1 of the present invention, the backlight module only shows 4 strings of LED lamps, and actually, the number of LED lamp strings can be increased or decreased according to the LCD backlight requirement, and the number of LED lamps in each string can be increased or decreased, thereby expanding the application range thereof.
The above-described embodiments do not limit the scope of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the above-described embodiments should be included in the protection scope of the technical solution.
Claims (10)
1. A LCD screen backlight constant current drive circuit is characterized in that: the backlight control circuit comprises a backlight module, a driving module connected with the backlight module, a second power supply terminal VCC2 connected with the backlight module, a first power supply terminal VCC1 connected with the driving module, and a backlight control terminal connected with the driving module, wherein the backlight control terminal is connected with a control chip;
the backlight module comprises a plurality of strings of LED lamps and a capacitor C1, one end of the capacitor C1 is connected with a second power supply terminal VCC2, the other end of the capacitor C1 is grounded, the anode of each string of LED lamps is connected with the second power supply terminal VCC2, and the cathode of each string of LED lamps is respectively connected with a plurality of output ends of the driving module;
the driving module comprises a plurality of backlight driving circuits, a backlight stabilizing circuit and a backlight control circuit, one end of the backlight stabilizing circuit is connected with the first power supply end VCC1, the other end of the backlight stabilizing circuit is connected with the input ends of the backlight driving circuits, one end of the backlight control circuit is connected with the control chip, the other end of the backlight control circuit is connected with the control ends of the backlight driving circuits, and the output end of each backlight driving circuit is connected with the cathode of each string of LED lamps.
2. The LCD screen backlight constant current driving circuit according to claim 1, wherein: each string of the LED lamps is connected with more than two LED lamp beads in series, and the anode of each LED lamp bead is connected with the cathode of the other LED lamp bead.
3. The LCD screen backlight constant current driving circuit according to claim 2, wherein: the stabilizing circuit is shaded, including the electric capacity C2 that first supply terminal VCC1, other end ground connection are connected to one end, first supply terminal VCC1 is connected to one end, the resistance R1 of the C utmost point of the triode Q1 is connected to the other end, the e utmost point of triode Q1 is connected to one end, the resistance R2 of other end ground connection, the b utmost point of the triode Q1 of stabilizing is connected with the C utmost point.
4. The LCD screen backlight constant current drive circuit according to claim 3, characterized in that: the backlight control circuit comprises a resistor R7, one end of which is connected with the control chip and the other end of which is connected with the b pole of the control triode Qt, a capacitor C3, one end of which is connected with the b pole of the control triode Qt and the other end of which is grounded, a resistor R8, one end of which is connected with the b pole of the control triode Qt and the other end of which is grounded, and the e pole of the control triode Qt is grounded.
5. The LCD screen backlight constant current drive circuit according to claim 4, characterized in that: the backlight driving circuit comprises a plurality of driving triodes Qn, a plurality of resistors Rn, wherein one end of each driving triode Qn is connected with the e pole of each driving triode Qn, the other end of each driving triode Qn is connected with the c pole of the control triode Qt, n is any natural number, the b pole of each driving triode Qn is simultaneously connected with the b pole of the stabilizing triode Q1, and the c pole of each driving triode Qn is respectively connected with the cathode of each string of LED lamps.
6. The LCD screen backlight constant current drive circuit according to claim 5, characterized in that: the stabilizing transistor Q1 has the function of automatically adjusting the c-pole current of each driving transistor Qn to be stable and unchanged when the ambient temperature rises or falls.
7. The LCD screen backlight constant current drive circuit according to claim 6, characterized in that: the driving triode Qn works in a constant current driving mode, and when the second power supply terminal VCC2 changes, the brightness of each string of LED lamps is maintained.
8. The LCD screen backlight constant current drive circuit according to claim 7, characterized in that: and the control triode Qt is used for turning on each string of LED lamps when the control chip outputs a high level, turning off each string of LED lamps when the control chip outputs a low level, and controlling the brightness of each string of LED lamps to be increased or reduced when the control chip outputs PWM (pulse width modulation) signals with different duty ratios.
9. The LCD panel backlight constant current driving circuit according to claim 8, wherein: the resistor R7 and the resistor R8 form a voltage division circuit, and the capacitor C3 is a high-frequency filter capacitor.
10. The LCD panel backlight constant current driving circuit according to claim 9, wherein: the capacitor C1 and the capacitor C2 are power filter capacitors of a first power supply end VCC1 and a second power supply end VCC2 respectively, and the resistor R1 is a current-limiting resistor.
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| CN202010558437.2A CN111883068A (en) | 2020-06-18 | 2020-06-18 | LCD screen constant current drive circuit that is shaded |
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| CN202010558437.2A CN111883068A (en) | 2020-06-18 | 2020-06-18 | LCD screen constant current drive circuit that is shaded |
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| CN (1) | CN111883068A (en) |
Citations (12)
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Application publication date: 20201103 |