CN108231014B - Regional dimming constant current control circuit, driving power supply and television - Google Patents
Regional dimming constant current control circuit, driving power supply and television Download PDFInfo
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- CN108231014B CN108231014B CN201810126819.0A CN201810126819A CN108231014B CN 108231014 B CN108231014 B CN 108231014B CN 201810126819 A CN201810126819 A CN 201810126819A CN 108231014 B CN108231014 B CN 108231014B
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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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Abstract
The invention discloses a local dimming constant current control circuit, a driving power supply and a television, wherein the local dimming constant current control circuit is connected with an AC-DC conversion circuit, a main board and a backlight lamp bar and comprises a dimming control module and a constant current driving module internally provided with a boost control circuit and a multi-channel dimming switch tube; the dimming control module receives a driving signal and a dimming signal output by the main board and transmits the driving signal and the dimming signal to the constant current driving module, the constant current driving module boosts a first voltage output by the AC-DC conversion circuit to a preset voltage according to the driving signal and outputs the preset voltage to the backlight lamp bar, and the grid duty ratio of the dimming switching tube of the corresponding channel is adjusted according to the dimming signal, so that the current of the corresponding channel is adjusted. By adopting the constant current driving module with the built-in boost control circuit and the dimming switch tube, the framework of the regional dimming light source is effectively optimized, the problem of unstable current caused by the crosstalk of the ground wire loop is reduced, the area of a PCB is effectively reduced, and the purpose of reducing the cost is achieved.
Description
Technical Field
The invention relates to the technical field of power supplies of electric appliances, in particular to a control circuit, a driving power supply and a television for reducing output voltage ripples.
Background
With the change of science and technology, the development of televisions is also rapid, the requirements of consumers on the image quality of the televisions are more and more strict, and television manufacturers are also continuous to make technological breakthroughs to meet the requirements of the consumers.
At present, most of regional dimming chips used in the market comprise IW7025, IW7027, IW7038 and the like of IWATT manufacturers, as shown in figure 1, alternating current is converted by an AC-DC module circuit and then outputs 24V or 48V to Boost a DC-DC module circuit, the boosted voltage is used for supplying power to a backlight lamp bar, an MCU controls a constant current control chip IW7027 through an SPI bus, and IW7027 outputs a signal to control switches MOSFETQ 1-Q16 at the negative end of a backlight L ED lamp, so that the backlight lamp bar is turned on or off, and meanwhile, a FB pin controls the DC-DC boosting circuit to enable the power supply voltage for the backlight lamp bar to meet the requirements.
As further shown in fig. 2, the IW7027 and IW7038 are similar in overall structure, the IW7038 integrates the switching MOSFET tube at the negative terminal of the backlight lamp bar into the chip, the work flow is the same as IW7027, both of the two structures use relatively independent DC-to-DC boost circuits, and in practical application, due to high power, crosstalk occurs between the ground line loop of the DC-DC boost circuit and the ground line loop of the IW7027/7038, which causes unstable lamp current of the backlight L ED, resulting in problems of screen flash or water ripple interference on the screen.
Thus, the prior art has yet to be improved and enhanced.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide the local dimming constant current control circuit, the driving power supply and the television, and by adopting the constant current driving module with the built-in boost control circuit and the built-in dimming switching tube, the framework of the local dimming light source is effectively optimized, the problem of unstable current caused by ground wire loop crosstalk is reduced, meanwhile, the area of a PCB (printed circuit board) is effectively reduced, and the purpose of reducing the cost is achieved.
In order to achieve the purpose, the invention adopts the following technical scheme:
a local dimming constant current control circuit is connected with an AC-DC conversion circuit, a main board and a backlight lamp bar and comprises a dimming control module and a constant current driving module internally provided with a boost control circuit and a multi-channel dimming switch tube; the dimming control module receives a driving signal and a dimming signal output by the main board and transmits the driving signal and the dimming signal to the constant current driving module, the constant current driving module boosts a first voltage output by the AC-DC conversion circuit to a preset voltage according to the driving signal and outputs the preset voltage to the backlight lamp bar, and the grid duty ratio of the dimming switching tube of the corresponding channel is adjusted according to the dimming signal, so that the current of the corresponding channel is adjusted.
In the local dimming constant current control circuit, the constant current driving module comprises a boosting unit, a constant current control unit internally provided with a boosting control circuit and a multi-channel dimming switching tube; the constant current control unit outputs a driving pulse to the boosting unit according to the driving signal to drive the boosting unit to start working; the boosting unit boosts a first voltage output by the AC-DC conversion circuit to a preset voltage and then outputs the preset voltage to the backlight lamp bar; the constant current control unit also adjusts the duty ratio of the grid electrode of the dimming switch tube of the corresponding channel according to the dimming signal, and then adjusts the current of the corresponding channel.
In the local dimming constant current control circuit, the constant current control unit further generates a detection voltage according to the actual working voltage of the backlight lamp bar, judges whether the actual working voltage of the backlight lamp bar is a preset voltage or not according to the detection voltage, and adjusts the duty ratio of the driving pulse according to the judgment result.
In the local dimming constant current control circuit, the dimming control module comprises a dimming control unit and a data transmission unit, the dimming control unit receives a driving signal and a dimming signal output by the main board, and the driving signal and the dimming signal are output to the constant current driving module through the data transmission unit.
In the local dimming constant current control circuit, the constant current control unit comprises a constant current control chip, the No. 1 pin of the constant current control chip is connected with the boosting unit, the No. 5 pin, the No. 6 pin and the No. 7 pin of the constant current control chip are connected with the dimming control module, and the No. 14 pin to the No. 20 pin of the constant current control chip are connected with the backlight lamp strip.
In the local dimming constant current control circuit, the boosting unit comprises an inductor, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first diode, a second diode, a first voltage stabilizing diode, a second voltage stabilizing diode and an MOS (metal oxide semiconductor) tube;
one end of the inductor is connected with a first voltage output end of the AC-DC conversion circuit, and the other end of the inductor is connected with the anode of the second diode, the drain electrode of the MOS tube and one end of the eighth resistor; the cathode of the second diode is connected with one end of a second capacitor, the anode of a third capacitor, the anode of a fourth capacitor and the backlight lamp bar; the negative electrode of the third capacitor and the negative electrode of the fourth capacitor are both grounded; the other end of the second capacitor is connected with the other end of the eighth resistor and one end of the ninth resistor; the other end of the ninth resistor is connected with one end of the eighth resistor and one end of the first capacitor; the other end of the first capacitor is connected with the cathode of the second voltage stabilizing diode, one end of the fifth resistor, one end of the sixth resistor, one end of the seventh resistor and the source electrode of the MOS tube; the anode of the second voltage stabilizing diode, the other end of the fifth resistor, the other end of the sixth resistor and the other end of the seventh resistor are all grounded; the grid electrode of the MOS tube is connected with the cathode of the first voltage stabilizing diode, the anode of the first diode, one end of the second resistor and one end of the third resistor; the anode of the first voltage stabilizing diode is connected with one end of a fifth resistor, the other end of the third resistor and one end of a fourth resistor; the negative electrode of the first diode is connected with one end of a first resistor; the other end of the first resistor is connected with the other end of the second resistor and one end of the tenth resistor; the other end of the fourth resistor is connected with a 22 nd pin of the constant current control chip; the other end of the tenth resistor is connected with a 1 st pin of the constant current control chip.
In the local dimming constant current control circuit, the dimming control unit comprises a microcontroller, a 7 th pin, a 12 th pin and a 15 th pin of the microcontroller are connected with a mainboard, and a 2 nd pin, a 3 rd pin and a 19 th pin of the microcontroller are connected with the constant current driving module.
In the local dimming constant current control circuit, the data transmission unit comprises an eleventh resistor and a twelfth resistor; one end of the eleventh resistor is connected with a pin 2 of the microcontroller, and the other end of the eleventh resistor is connected with the constant current driving module; one end of the twelfth resistor is connected with a pin 3 of the microcontroller, and the other end of the twelfth resistor is connected with the constant current driving module.
A driving power supply comprises a shell, wherein a PCB is arranged in the shell, and the PCB is provided with a local dimming constant current control circuit.
A television set comprising a drive power supply as described above.
Compared with the prior art, in the local dimming constant current control circuit, the driving power supply and the television, the local dimming constant current control circuit is connected with the AC-DC conversion circuit, the main board and the backlight lamp strip and comprises a dimming control module and a constant current driving module internally provided with a boost control circuit and a multi-channel dimming switch tube; the dimming control module receives a driving signal and a dimming signal output by the main board and transmits the driving signal and the dimming signal to the constant current driving module, the constant current driving module boosts a first voltage output by the AC-DC conversion circuit to a preset voltage according to the driving signal and outputs the preset voltage to the backlight lamp bar, and the grid duty ratio of the dimming switching tube of the corresponding channel is adjusted according to the dimming signal, so that the current of the corresponding channel is adjusted. By adopting the constant current driving module with the built-in boost control circuit and the dimming switch tube, the framework of the regional dimming light source is effectively optimized, the problem of unstable current caused by the crosstalk of the ground wire loop is reduced, the area of a PCB is effectively reduced, and the purpose of reducing the cost is achieved.
Drawings
FIG. 1 is a block diagram of a prior art power architecture for an IW7027 chip;
FIG. 2 is a block diagram of a prior art power architecture for an IW7028 chip;
fig. 3 is a block diagram of a local dimming constant current control circuit according to the present invention;
fig. 4 is a circuit diagram of the local dimming constant current control circuit provided by the present invention.
Detailed Description
The invention provides a local dimming constant current control circuit, a driving power supply and a television, wherein the framework of a local dimming light source is effectively optimized by adopting a constant current driving module with a built-in boost control circuit and a dimming switching tube, the problem of unstable current caused by ground wire loop crosstalk is reduced, the area of a PCB (printed circuit board) is effectively reduced, and the purpose of reducing the cost is achieved.
In order to make the objects, technical solutions and effects of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 3, the local dimming constant current control circuit 10 provided by the present invention is connected to the AC-DC conversion circuit 20, the main board 30 and the backlight light bar 40, the input AC is converted into DC by the AC-DC conversion circuit 20, and then the first voltage and the second voltage are respectively output to the local dimming constant current control circuit 10 and the main board 30 to supply power to the two, the main board 30 outputs a control signal to the local dimming constant current control circuit 10 after working, the local dimming constant current control circuit 10 provides a corresponding working voltage to the backlight light bar 40, and adjusts the current of the corresponding channel light bar according to the control signal, so as to implement local dimming. Specifically, the local dimming constant current control circuit 10 includes a dimming control module 11 and a constant current driving module 12 with a built-in boost control circuit and a multi-channel dimming switch tube, the dimming control module 11 receives a driving signal and a dimming signal output by the main board 30 and transmits the driving signal and the dimming signal to the constant current driving module 12, the constant current driving module 12 boosts a first voltage output by the AC-DC conversion circuit 20 to a preset voltage according to the driving signal and outputs the preset voltage to the backlight light bar 40, and adjusts a gate duty ratio of the dimming switch tube of the corresponding channel according to the dimming signal, so as to adjust a current magnitude of the corresponding channel. The AC-DC conversion circuit 20 is a conventional circuit, and the connection relationship thereof will not be described in detail here.
In the invention, because the constant current driving module 12 with the built-in boost control circuit and the multi-channel dimming switch tube is adopted, the local dimming constant current control circuit 10 is only composed of two circuit modules, namely the constant current driving module 12 and the dimming control module 11, the built-in boost control circuit enables a ground wire loop to be simpler, the problems of screen flash or water ripple interference and the like of a screen caused by ground wire crosstalk can be effectively reduced, the framework of a local dimming light source is effectively optimized, the area can be effectively reduced when a PCB (printed circuit board) is wired, and the production cost and the design and debugging difficulty of a local dimming power supply are reduced.
Specifically, referring to fig. 4, the dimming control module 11 includes a dimming control unit 111 and a data transmission unit 112, the dimming control unit 111 is connected to the main board 30 and the data transmission unit 112, and the data transmission unit 112 is connected to the constant current driving module 12; in this embodiment, the dimming control unit 111 receives the driving signal and the dimming signal output by the main board 30, and the data transmission unit 112 realizes I2C data transmission with the constant current driving module 12, and outputs the driving signal and the dimming signal to the constant current driving module 12, so as to ensure stable transmission of the digital control signal and provide reliability of constant current control.
Further, the constant current driving module 12 includes a voltage boosting unit 121 and a constant current control unit 122 with a built-in voltage boosting control circuit and a multi-channel dimming switching tube, the voltage boosting unit 121 is connected to the constant current control unit 122 and the backlight light bar 40, and the constant current control unit 122 is further connected to the dimming control module 11; when the backlight lamp bar 40 is driven to work, the constant current control unit 122 outputs a driving pulse to the boosting unit 121 according to the driving signal, and drives the boosting unit 121 to start working; the boosting unit 121 boosts the first voltage output by the AC-DC conversion circuit 20 to a preset voltage and outputs the preset voltage to the backlight light bar 40; the constant current control unit 122 further adjusts the gate duty ratio of the dimming switching tube of the corresponding channel according to the dimming signal, so as to adjust the current magnitude of the corresponding channel. In the local dimming constant current control circuit 10 provided by the invention, the Boost control circuit and the multi-channel dimming switching tube are arranged in the constant current control unit 122, Boost is realized by matching with the Boost unit 121, the first voltage output by the AC-DC conversion circuit 20 is reduced by the preset voltage and then is output to the backlight lamp strip 40, and normal operation of the backlight lamp strip 40 is realized.
Preferably, to ensure stable operation of the backlight light bar 40, the constant current control unit 122 further generates a detection voltage according to an actual working voltage of the backlight light bar 40, determines whether the actual working voltage of the backlight light bar 40 is a preset voltage according to the detection voltage, and adjusts the duty ratio of the driving pulse according to a determination result. That is, the constant current control unit 122 can determine whether the current working voltage meets the specification of the backlight lamp strip 40 according to the working voltage fed back by the backlight lamp strip, and self-adjusts the voltage outputted to the backlight light bar 40, specifically, when the voltage outputted to the backlight light bar 40 from the voltage boosting unit 121 is too high, that is, when the actual working voltage of the backlight lamp bar 40 is higher than the preset voltage, the duty ratio of the driving pulse is decreased, the output voltage of the boost voltage is reduced until the preset voltage is output to the backlight lamp bar 40, and when the voltage output from the boost unit 121 to the backlight lamp bar 40 is too low, that is, when the actual working voltage of the backlight lamp bar 40 is lower than the preset voltage, the duty ratio of the driving pulse is increased, the output voltage of the boost voltage is increased until the preset voltage is output, the backlight lamp strip 40 is ensured to work stably and safely, and the stability and reliability of the driving power supply are improved.
Specifically, please refer to fig. 4, the constant current control unit 122 includes a constant current control chip U1, the 1 st pin of the constant current control chip U1 is connected to the voltage boost unit 121 for controlling the operating state of the voltage boost unit 121, the 5 th pin, the 6 th pin and the 7 th pin of the constant current control chip U1 are all connected to the dimming control module 11 for implementing data communication connection with the dimming control module 11, the 14 th pin to the 20 th pin of the constant current control chip U1 are all connected to the backlight lamp strip 40, which is the negative end input end of the backlight lamp strip 40, in this embodiment, the constant current control chip U1 adopts a constant current driving chip of an OZ556 model, and a DC-DC voltage boost control end circuit and a multi-channel dimming switch tube are integrated therein, so that a power supply architecture can be simplified and ground line crosstalk can be reduced while implementing constant current control, of course, in other embodiments, other constant current control chips U1 with the same function may be used, and the invention is not limited in this respect.
Further, the voltage boosting unit 121 includes a fuse F1, an inductor L1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a first diode D1, a second diode D2, a first zener diode ZD1, a second zener diode ZD2, and a MOS transistor Q18.
One end of the inductor 1 is connected with a first voltage output end of an AC-DC conversion circuit 20 through a fuse F, the other end of the inductor 1 is connected with an anode of a second diode D, a drain electrode of an MOS (metal oxide semiconductor) tube Q and one end of an eighth resistor R, a cathode of the second diode D is connected with one end of a second capacitor C, an anode of a third capacitor C, an anode of a fourth capacitor C and a backlight lamp bar 40, a cathode of the third capacitor C and a cathode of the fourth capacitor C are grounded, the other end of the second capacitor C is connected with the other end of the eighth resistor R and one end of a ninth resistor R, the other end of the ninth resistor R is connected with one end of the eighth resistor R and one end of the first capacitor C, the other end of the first capacitor C is connected with a cathode of a second voltage stabilizing diode ZD, one end of the fifth resistor R, one end of the sixth resistor R, one end of the seventh resistor R and a source of the MOS lamp bar Q, an anode of the second voltage stabilizing diode ZD, a cathode of the fifth resistor R, a cathode of the sixth resistor R, a cathode of the seventh resistor R and a cathode of the MOS resistor R are connected with a gate of a first diode R, a constant voltage output resistor R, a first diode R and a constant voltage output resistor R, a constant voltage output voltage control unit of the LED lamp bar 20, the first diode R is connected with a first diode R, the output voltage control unit 20, the first diode D, the constant voltage control unit 20, the first diode R and the constant voltage control unit 20, the first diode R, the constant voltage control unit is connected with the first diode R, the constant voltage control unit, the first diode R, the constant voltage control unit.
Further, the dimming control unit 111 includes a microcontroller U2, the 7 th pin, the 12 th pin, and the 15 th pin of the microcontroller U2 are connected to the main board 30, and are configured to receive control signals output by the main board 30, such as ON/OFF, ENA, SCK, and CSB, and the 2 nd pin, the 3 rd pin, and the 19 th pin of the microcontroller U2 are all connected to the constant current driving module 12, and are configured to implement I2C data transmission with the constant current driving module 12, and ensure stability of signal transmission. In this embodiment, the microcontroller U2 is an MCU with a model of MSP430G2433IPW20R, but in other embodiments, other microcontrollers U2 with the same function may be used, which is not limited in the present invention.
Further, the data transmission unit 112 includes an eleventh resistor R11 and a twelfth resistor R12; one end of the eleventh resistor R11 is connected to the 2 nd pin of the microcontroller U2, and the other end of the eleventh resistor R11 is connected to the constant current driving module 12, specifically to the 6 th pin of the constant current control chip U1; one end of the twelfth resistor R12 is connected to the 3 rd pin of the microcontroller U2, and the other end of the twelfth resistor R12 is connected to the constant current driving module 12, specifically to the 7 th pin of the constant current control chip U1; the eleventh resistor R11 and the twelfth resistor R12 form an I2C data transmission circuit, and achieve SPI bus communication with the constant current control chip U1.
Preferably, in order to further optimize the performance of the local dimming constant current control circuit 10, the constant current driving module 12 further includes a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a twenty-first resistor R21, a twenty-second resistor R22, a twenty-third resistor R23, a twenty-fourth resistor R24, a twenty-fifth resistor R25, a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a ninth capacitor C9, a tenth capacitor C10, and an eleventh capacitor C11.
One end of the thirteenth resistor R13 is connected with the cathode of the second diode D2, the other end of the thirteenth resistor R13 is connected with one end of the fourteenth resistor R14, the 20 th pin of the constant current control chip U1 and one end of the fifth capacitor C5, and the other end of the fourteenth resistor R14 is grounded through the fifteenth resistor R15; the other end of the fifth capacitor C5 is grounded; one end of the sixteenth resistor R16 is connected with an ENA signal end, and the other end of the sixteenth resistor R16 is connected with one end of a seventeenth resistor R17, one end of a sixth capacitor C6 and the 3 rd pin of a constant current control chip U1; the other end of the seventeenth resistor R17 and the other end of the sixth capacitor C6 are both grounded; one end of the seventh capacitor C7 is connected with the 12V power supply end, one end of the eighth capacitor C8 and the 4 th pin of the constant current control chip U1, and the other end of the seventh capacitor C7 and the other end of the eighth capacitor C8 are both grounded; one end of the eighteenth resistor R18 is connected with the 5 th pin of the constant current control chip U1, and the other end of the eighteenth resistor R18 is connected with the 19 th pin of the microcontroller U2; one end of the 19 th resistor is connected with one end of the 20 th resistor and the 8 th pin of the constant current control chip U1, and the other end of the nineteenth resistor R19 is connected with the 13 th pin of the microcontroller U2; the other end of the twentieth resistor R20 is connected with a 3.3V power supply end and a 9 th pin of a constant current control chip U1; one end of the twenty-first resistor R21 is connected with the 10 th pin of the constant current control chip U1; one end of the twenty-second resistor R22 is connected with the 11 th pin of the constant current control chip U1; one end of the twenty-third resistor R23 is connected with the 12 th pin of the constant current control chip U1, and the other end of the twenty-third resistor R23 is grounded through a ninth capacitor C9; one end of the twenty-fourth resistor R24 and one end of the twenty-fifth resistor R25 are both connected with the 13 th pin of the constant current control chip U1; one end of the tenth capacitor C10 is connected with the 22 nd pin of the constant current control chip U1; one end of the eleventh capacitor C11 is connected with the 2 nd pin of the constant current control chip U1, and the other end of the twenty-first resistor R21, the other end of the twenty-second resistor R22, the other end of the twenty-fourth resistor R24, the other end of the twenty-fifth resistor R25, the other end of the tenth capacitor C10 and the other end of the eleventh capacitor C11 are all grounded; .
The thirteenth resistor R13, the fourteenth resistor R14, the fifteenth resistor R15 and the fifth capacitor C5 are overvoltage protection circuits, so that overvoltage protection is provided for the backlight lamp bar 40, and the working safety of the circuits is improved; the sixteenth resistor R16, the seventeenth resistor R17 and the sixth capacitor C6 are backlight switch circuits and receive ENA enabling signals to drive the chip to start working, so that the backlight lamp bar 40 is turned on and off; the seventh capacitor C7 and the eighth capacitor C8 are power supply filter circuits, and filter the first voltage output by the AC-DC conversion circuit 20 to supply power to the chip, so as to filter out noise waves and ensure the stability of power supply to the chip; the eighteenth resistor R18 is mainly used for inputting a synchronous signal; the nineteenth resistor R19 and the twentieth resistor R20 are mainly used for judging identification input; the twenty-first resistor R21 and the twenty-second resistor R22 are mainly used for setting the working frequency of the chip; the twenty-third resistor R23 and the ninth capacitor C9 are mainly used for loop compensation to realize voltage regulation and feedback protection; the twenty-fourth resistor R24 and the twenty-fifth resistor R25 are mainly used for setting the lamp strip current so as to realize the dimming function; the eleventh capacitor C11 is used for providing reference voltage for the constant current control chip U1, and the tenth capacitor C10 is mainly used for overcurrent detection, so that driving current is guaranteed to be within a safety range, and circuit safety is improved.
Furthermore, the dimming control module 11 further includes a twenty-sixth resistor R26, a twenty-seventh resistor R27, a twenty-eighth resistor R28, a twenty-ninth resistor R29, a thirty-fourth resistor R30, a twelfth capacitor C12, a thirteenth capacitor C13, a fourteenth capacitor C14, a fifteenth capacitor C15, a light emitting diode L ED1 and a programming socket CN2, one end of the twenty-sixth resistor R26 is connected with a 3.3V power supply terminal, the other end of the twenty-sixth resistor R26 is connected with one end of the twelfth capacitor C12, one end of the thirteenth capacitor C13, one end of the fourteenth capacitor C14 and the 1 st pin of the microcontroller U2, the other end of the twelfth capacitor C2, the other end of the thirteenth capacitor C2 and the other end of the fourteenth capacitor C2 are all grounded, one end of the twenty-seventh resistor R2 is connected with the 4 th pin CN2 of the programming socket CN2, the other end of the twenty-seventh resistor R2 is connected with the anode of the programming resistor R2, the twenty-eighth resistor CN2 and the other end of the programming resistor CN2 are connected with the grounding terminal CN2, the thirty-fifth pin CN2, the cathode of the programming resistor CN2, the programming resistor CN2 is connected with the anode of the thirty-eighth resistor CN2, the lighting resistor CN2, the thirty-eighth pin 2, the other end of the programming socket CN2 is connected with the thirty-ninth pin 2, the lighting resistor CN2 is connected with the anode of the thirty-ninth pin 2, and the lighting resistor CN 2.
The twenty-sixth resistor R26, the twelfth capacitor C12, the thirteenth capacitor C13 and the fourteenth capacitor C14 are power supply circuits of the microcontroller U2 and provide stable working voltage for the microcontroller U2, the light emitting diode L ED1 is a working indicator lamp of the microcontroller U2, and working state information of the microcontroller U2 is output through the light emitting diode L ED1, so that a user can quickly judge the use condition of the microcontroller U2, for example, the use condition is normally on, the use condition is normally off, the use condition is stopped, the working condition is abnormal through flickering, and the like, the twenty-seventh resistor R27, the twenty-eighth resistor R28, the twenty-ninth resistor R29, the thirty-third resistor R30, the fifteenth capacitor C15 and the programming socket CN2 are programming software circuits, erasing operation of a software program is achieved, and flexibility of application of the microcontroller U2 is improved.
It should be noted that the remaining components not labeled in the figure, such as the resistor, the capacitor and the zener diode, are conventional components of the peripheral working circuit of the microcontroller U2 and the constant current control chip U1, which are prior art, and the connection relationship thereof is not described herein again.
Based on the local dimming constant current control circuit 10, the invention also provides a driving power supply correspondingly, which comprises a shell, wherein a PCB is arranged in the shell, the local dimming constant current control circuit 10 is arranged on the PCB, and the local dimming constant current control circuit 10 is described in detail above and is not described in detail here.
The invention also provides a television set comprising the driving power supply, which is not described in detail since the driving power supply is described in detail above.
In order to better understand the control process of the local dimming constant current control circuit 10 provided by the present invention, the following description is made with reference to fig. 3 and 4 to illustrate the working process of the local dimming constant current control circuit 10 by way of an application example:
after the backlight dimming circuit is started, an alternating current input voltage passes through an AD-DC conversion circuit and provides 48V and 12V voltages, wherein 12V supplies power to a main board 30 and a constant current control chip U1, 12V obtains 3.3V through a three-terminal regulator and supplies power to a microcontroller U2, after the main board 30 works, control signals such as ON/OFF, ENA, SCK, CSB and the like are provided, the microcontroller U2 starts working, the constant current control chip U1 is supplied through an SC L, SDA and VSYNC data line, the constant current control chip U1 outputs a driving pulse DRV to a MOS tube Q18 in a boosting unit 121, the constant current control chip U121 starts working, an energy storage inductor L starts charging and discharging, energy is rectified and filtered by a second diode D2 and a fourth capacitor C4 to output a constant direct current voltage to supply power to a backlight light bar 40, then the constant current control chip U1 returns to the constant current control chip U596 through a negative terminal, the control chip U582 detects an internal voltage according to detect the internal voltage, generates a detection voltage, the detection result that the detection voltage meets the requirement of the microcontroller U632, the detection result that the constant current output voltage meets the duty ratio control chip detects that the duty ratio of the constant current output voltage that the constant current output voltage control chip V output by a constant current control chip U358 when the constant current control chip V control chip 121, and the constant current control chip 2 meets the constant current control chip after the constant current control chip 121, the constant current control chip 121 meets the constant current control chip after the duty ratio control chip 121 meets the duty ratio control chip 121, the constant current control chip 121 meets the duty ratio control chip.
In summary, in the local dimming constant current control circuit, the driving power supply and the television provided by the invention, the local dimming constant current control circuit is connected with the AC-DC conversion circuit, the main board and the backlight lamp strip, and comprises a dimming control module and a constant current driving module with a built-in boost control circuit and a multi-channel dimming switch tube; the dimming control module receives a driving signal and a dimming signal output by the main board and transmits the driving signal and the dimming signal to the constant current driving module, the constant current driving module boosts a first voltage output by the AC-DC conversion circuit to a preset voltage according to the driving signal and outputs the preset voltage to the backlight lamp bar, and the grid duty ratio of the dimming switching tube of the corresponding channel is adjusted according to the dimming signal, so that the current of the corresponding channel is adjusted. By adopting the constant current driving module with the built-in boost control circuit and the dimming switch tube, the framework of the regional dimming light source is effectively optimized, the problem of unstable current caused by the crosstalk of the ground wire loop is reduced, the area of a PCB is effectively reduced, and the purpose of reducing the cost is achieved.
It should be understood that equivalents and modifications of the technical solution and inventive concept thereof may occur to those skilled in the art, and all such modifications and alterations should fall within the scope of the appended claims.
Claims (7)
1. A local dimming constant current control circuit is connected with an AC-DC conversion circuit, a main board and a backlight lamp bar and is characterized by comprising a dimming control module and a constant current driving module internally provided with a boost control circuit and a multi-channel dimming switch tube; the dimming control module receives a driving signal and a dimming signal output by the main board and transmits the driving signal and the dimming signal to the constant current driving module, the constant current driving module boosts a first voltage output by the AC-DC conversion circuit to a preset voltage according to the driving signal and outputs the preset voltage to the backlight lamp bar, and the grid duty ratio of the dimming switching tube of the corresponding channel is adjusted according to the dimming signal, so that the current of the corresponding channel is adjusted;
the constant current driving module comprises a boosting unit and a constant current control unit internally provided with a boosting control circuit and a multi-channel dimming switching tube; the constant current control unit outputs a driving pulse to the boosting unit according to the driving signal to drive the boosting unit to start working; the boosting unit boosts a first voltage output by the AC-DC conversion circuit to a preset voltage and then outputs the preset voltage to the backlight lamp bar; the constant current control unit also adjusts the grid duty ratio of the dimming switching tube of the corresponding channel according to the dimming signal so as to adjust the current of the corresponding channel;
the constant current control unit comprises a constant current control chip, the No. 1 pin of the constant current control chip is connected with the boosting unit, the No. 5 pin, the No. 6 pin and the No. 7 pin of the constant current control chip are connected with the dimming control module, and the No. 14 pin to the No. 20 pin of the constant current control chip are connected with the backlight lamp strip;
the boosting unit comprises an inductor, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first diode, a second diode, a first voltage stabilizing diode, a second voltage stabilizing diode and an MOS (metal oxide semiconductor) tube;
one end of the inductor is connected with a first voltage output end of the AC-DC conversion circuit, and the other end of the inductor is connected with the anode of the second diode, the drain electrode of the MOS tube and one end of the eighth resistor; the cathode of the second diode is connected with one end of a second capacitor, the anode of a third capacitor, the anode of a fourth capacitor and the backlight lamp bar; the negative electrode of the third capacitor and the negative electrode of the fourth capacitor are both grounded; the other end of the second capacitor is connected with the other end of the eighth resistor and one end of the ninth resistor; the other end of the ninth resistor is connected with one end of the eighth resistor and one end of the first capacitor; the other end of the first capacitor is connected with the cathode of the second voltage stabilizing diode, one end of the fifth resistor, one end of the sixth resistor, one end of the seventh resistor and the source electrode of the MOS tube; the anode of the second voltage stabilizing diode, the other end of the fifth resistor, the other end of the sixth resistor and the other end of the seventh resistor are all grounded; the grid electrode of the MOS tube is connected with the cathode of the first voltage stabilizing diode, the anode of the first diode, one end of the second resistor and one end of the third resistor; the anode of the first voltage stabilizing diode is connected with one end of a fifth resistor, the other end of the third resistor and one end of a fourth resistor; the negative electrode of the first diode is connected with one end of a first resistor; the other end of the first resistor is connected with the other end of the second resistor and one end of the tenth resistor; the other end of the fourth resistor is connected with a 22 nd pin of the constant current control chip; the other end of the tenth resistor is connected with a 1 st pin of the constant current control chip.
2. The local dimming constant current control circuit according to claim 1, wherein the constant current control unit further generates a detection voltage according to an actual working voltage of the backlight light bar, determines whether the actual working voltage of the backlight light bar is a preset voltage according to the detection voltage, and adjusts a duty ratio of the driving pulse according to a determination result.
3. The local dimming constant current control circuit according to claim 1, wherein the dimming control module comprises a dimming control unit and a data transmission unit, the dimming control unit receives the driving signal and the dimming signal output by the main board, and outputs the driving signal and the dimming signal to the constant current driving module through the data transmission unit.
4. The local dimming constant current control circuit according to claim 3, wherein the dimming control unit comprises a microcontroller, the 7 th pin, the 12 th pin and the 15 th pin of the microcontroller are connected with a main board, and the 2 nd pin, the 3 rd pin and the 19 th pin of the microcontroller are connected with the constant current driving module.
5. The local dimming constant current control circuit according to claim 4, wherein the data transmission unit comprises an eleventh resistor and a twelfth resistor; one end of the eleventh resistor is connected with a pin 2 of the microcontroller, and the other end of the eleventh resistor is connected with the constant current driving module; one end of the twelfth resistor is connected with a pin 3 of the microcontroller, and the other end of the twelfth resistor is connected with the constant current driving module.
6. A driving power supply comprises a shell, wherein a PCB is arranged in the shell, and the PCB is provided with a local dimming constant current control circuit according to any one of claims 1 to 5.
7. A television set comprising the drive power supply according to claim 6.
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| CN201810126819.0A CN108231014B (en) | 2018-02-08 | 2018-02-08 | Regional dimming constant current control circuit, driving power supply and television |
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| CN201810126819.0A CN108231014B (en) | 2018-02-08 | 2018-02-08 | Regional dimming constant current control circuit, driving power supply and television |
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| CN108231014B true CN108231014B (en) | 2020-08-04 |
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| CN109309993B (en) * | 2018-11-16 | 2024-02-27 | 苏州中储普华电力科技有限公司 | Loop dimming circuit for intelligent illumination |
| CN109949753B (en) * | 2019-04-24 | 2021-06-11 | 深圳创维－Rgb电子有限公司 | Power supply device of backlight source |
| CN112216245A (en) * | 2020-10-09 | 2021-01-12 | 深圳创维－Rgb电子有限公司 | Adjusting circuit and method for module backlight lamp bar of television |
| CN112333889A (en) * | 2020-11-25 | 2021-02-05 | 深圳创维－Rgb电子有限公司 | Double-direct-drive LED power circuit and television |
| CN112584573A (en) * | 2020-12-11 | 2021-03-30 | 浙江金缘光电有限公司 | Seven-primary-color LED mixed light source and drive control circuit thereof |
| CN114023273B (en) * | 2021-11-22 | 2023-03-21 | 深圳创维－Rgb电子有限公司 | Local dimming driving circuit, method and system and electronic equipment |
| CN114420054B (en) * | 2021-12-23 | 2023-08-01 | 深圳创维－Rgb电子有限公司 | Backlight constant current driving circuit, switching power supply and display device |
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| KR20080001050A (en) * | 2006-06-29 | 2008-01-03 | 삼성전기주식회사 | System for driving lcd backlight comprising leds |
| JP2013021117A (en) * | 2011-07-11 | 2013-01-31 | Rohm Co Ltd | Led drive device, luminaire, and liquid crystal display device |
| TWI461108B (en) * | 2012-03-21 | 2014-11-11 | Tpv Electronics Fujian Co Ltd | Light-emitting diode lamp driving device |
| CN102740571B (en) * | 2012-07-18 | 2014-10-15 | 矽力杰半导体技术(杭州)有限公司 | Dimmable LED (Light-Emitting Diode) driving circuit and driving method |
| CN103107697A (en) * | 2013-01-22 | 2013-05-15 | 深圳市华星光电技术有限公司 | Current regulating device and regulating method thereof |
| CN103440848B (en) * | 2013-09-02 | 2016-01-20 | 深圳市华星光电技术有限公司 | Backlight drive circuit |
| CN103747193B (en) * | 2013-12-31 | 2017-01-11 | 深圳创维－Rgb电子有限公司 | Television set |
| CN205751480U (en) * | 2016-05-19 | 2016-11-30 | 合肥惠科金扬科技有限公司 | A kind of display device and power driving circuit thereof |
| CN106101594B (en) * | 2016-08-04 | 2019-03-12 | 深圳创维－Rgb电子有限公司 | HDR television set and local dimming method |
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