CN108231014A - A kind of local dimming constant-current control circuit, driving power and television set - Google Patents

Abstract

The invention discloses a regional dimming constant current control circuit, a driving power supply and a TV set, wherein the regional dimming constant current control circuit is connected with an AC-DC conversion circuit, a main board and a backlight strip, and includes a dimming control module and a constant current drive module with built-in boost control circuit and multi-channel dimming switch tube; the dimming control module receives the drive signal and dimming signal output by the main board and transmits them to the constant current drive module The drive signal boosts the first voltage output by the AC-DC conversion circuit to a preset voltage and then outputs it to the backlight light bar, and adjusts the grid duty ratio of the dimming switch tube of the corresponding channel according to the dimming signal, and then Adjust the current size of the corresponding channel. By adopting the built-in boost control circuit and the constant current drive module of the dimming switch tube, the structure of the regional dimming light source is effectively optimized, the problem of current instability caused by the crosstalk of the ground loop is reduced, and the PCB board area is effectively reduced to achieve The purpose of reducing costs.

Description

A local dimming constant current control circuit, driving power supply and TV

technical field

The invention relates to the technical field of electrical power supplies, in particular to a control circuit for reducing output voltage ripple, a driving power supply and a television.

Background technique

With the rapid development of science and technology, the development of TV is also advancing by leaps and bounds, and consumers' requirements for TV picture quality are becoming more and more stringent. In order to meet the needs of consumers, TV manufacturers are also constantly making technological breakthroughs. At present, TVs with HDR functions can bring a strong visual shock in terms of color gamut, contrast, and depth of field, and consumers are full of praise. For LED TVs, to realize the perfect HDR function, the backlight partition of the module (that is, the Localdimming function) is indispensable, and the design of the backlight partition of the module can play the role of icing on the cake.

At present, the most widely used regional dimming chips in the market include IW7025, IW7027, and IW7038 from IWATT manufacturers. As shown in Figure 1, the AC power is converted by the AC-DC module circuit to output 24V or 48V, which is boosted for the DC-DC module circuit, and the boosted voltage is used to supply power to the backlight strip. The MCU controls the constant current control chip IW7027 through the SPI bus, and the output signal of the IW7027 controls the switch MOSFETQ1~Q16 at the negative end of the backlight LED lamp to turn it on or off, and at the same time controls the DC-DC boost circuit through the FB pin to make the backlight strip The power supply voltage meets the requirements.

As further shown in Figure 2, the overall structure of IW7027 and IW7038 is similar. IW7038 integrates the switch MOSFET tube at the negative end of the backlight bar into the chip, and the working process is the same as that of IW7027. Both structures use a relatively independent DC to DC converter. Voltage circuit, in practical applications, due to the large power, there is crosstalk between the ground loop of the DC-DC boost circuit and the IW7027/7038 ground loop, causing the backlight LED lamp current to be unstable, resulting in screen flicker or water ripple interference And other issues.

Thereby prior art still needs to improve and improve.

Contents of the invention

In view of the shortcomings of the above-mentioned prior art, the object of the present invention is to provide a local dimming constant current control circuit, a driving power supply and a TV set, by adopting a constant current drive module with a built-in boost control circuit and a dimming switch tube Effectively optimize the structure of the local dimming light source, reduce the problem of current instability caused by ground loop crosstalk, and effectively reduce the PCB board area to achieve the purpose of reducing costs.

In order to achieve the above object, the present invention has taken the following technical solutions:

A regional dimming constant current control circuit, which is connected with an AC-DC conversion circuit, a main board and a backlight light bar, and includes a dimming control module and a constant current drive module with a built-in boost control circuit and a multi-channel dimming switch tube; The dimming control module receives the driving signal and the dimming signal output by the main board and transmits them to the constant current driving module, and the constant current driving module boosts the first voltage output by the AC-DC conversion circuit to a preset value according to the driving signal The voltage is then output to the backlight strip, and the grid duty ratio of the dimming switch tube of the corresponding channel is adjusted according to the dimming signal, thereby adjusting the current of the corresponding channel.

In the regional dimming constant current control circuit, the constant current drive module includes a boost unit and a constant current control unit with a built-in boost control circuit and a multi-channel dimming switch tube; The driving signal outputs a driving pulse to the boost unit to drive the boost unit to start working; the boost unit boosts the first voltage output by the AC-DC conversion circuit to a preset voltage and then outputs it to the backlight strip; The constant current control unit also adjusts the gate duty ratio 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 also generates a detection voltage according to the actual working voltage of the backlight light bar, and judges whether the current actual working voltage of the backlight light bar is a preset voltage according to the detection voltage , and adjust the duty cycle of the driving pulse according to the judgment result.

In the local dimming constant current control circuit, the dimming control module includes a dimming control unit and a data transmission unit, and the dimming control unit receives the driving signal and the dimming signal output by the main board, and transmits the The data transmission unit outputs the driving signal and the dimming signal to the constant current driving module.

In the local dimming constant current control circuit, the constant current control unit includes a constant current control chip, the first pin of the constant current control chip is connected to the boost unit, and the fifth pin of the constant current control chip The 14th to 20th pins of the constant current control chip are all connected to the backlight strip.

In the local dimming constant current control circuit, the boost unit includes 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 resistor, ninth resistor, tenth resistor, first capacitor, second capacitor, third capacitor, fourth capacitor, first diode, second diode, first Zener diode, second Zener diode and MOS tube;

One end of the inductance is connected to the first voltage output end of the AC-DC conversion circuit, and the other end of the inductance is connected to the anode of the second diode, the drain of the MOS transistor and one end of the eighth resistor; the second two The negative pole of the pole tube is connected to one end of the second capacitor, the positive pole of the third capacitor, the positive pole of the fourth capacitor and the backlight strip; the negative pole of the third capacitor and the negative pole of the fourth capacitor are both grounded; the other end of the second capacitor One end is connected to the other end of the eighth resistor and one end of the ninth resistor; the other end of the ninth resistor is connected to one end of the eighth resistor and one end of the first capacitor; the other end of the first capacitor is connected to the second stable The cathode of the voltage diode, one end of the fifth resistor, one end of the sixth resistor, one end of the seventh resistor and the source of the MOS tube; the anode of the second Zener diode, the other end of the fifth resistor, and the source of the sixth resistor The other end and the other end of the seventh resistor are grounded; the gate of the MOS transistor is connected to the cathode of the first Zener 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 Zener diode is connected to one end of the fifth resistor, the other end of the third resistor and one end of the fourth resistor; the negative electrode of the first diode is connected to one end of the first resistor; The other end is connected to the other end of the second resistor and one end of the tenth resistor; the other end of the fourth resistor is connected to the 22nd pin of the constant current control chip; the other end of the tenth resistor is connected to the constant current control chip pin 1 of the chip.

In the local dimming constant current control circuit, the dimming control unit includes a microcontroller, the 7th pin, the 12th pin and the 15th pin of the microcontroller are connected to the main board, and the microcontroller's The 2nd pin, the 3rd pin and the 19th pin are all connected to the constant current drive module.

In the local dimming constant current control circuit, the data transmission unit includes an eleventh resistor and a twelfth resistor; one end of the eleventh resistor is connected to the second pin of the microcontroller, and the eleventh resistor is connected to the second pin of the microcontroller. The other end of the resistor is connected to the constant current drive module; one end of the twelfth resistor is connected to pin 3 of the microcontroller, and the other end of the twelfth resistor is connected to the constant current drive module.

A driving power supply includes a casing, and a PCB board is arranged inside the casing, and the above-mentioned regional dimming constant current control circuit is arranged on the PCB board.

A TV set includes the above driving power supply.

Compared with the prior art, in the regional dimming constant current control circuit, the driving power supply and the TV set provided by the present invention, the regional dimming constant current control circuit is connected with the AC-DC conversion circuit, the main board and the backlight strip, and its A constant current drive module including a dimming control module, a built-in boost control circuit and a multi-channel dimming switch tube; the dimming control module receives the driving signal and dimming signal output by the main The current drive module boosts the first voltage output by the AC-DC conversion circuit to a preset voltage according to the drive signal, and then outputs it to the backlight strip, and adjusts the gate occupation of the dimming switch tube of the corresponding channel according to the dimming signal. Duty ratio, and then adjust the current size of the corresponding channel. By adopting the built-in boost control circuit and the constant current drive module of the dimming switch tube, the structure of the regional dimming light source is effectively optimized, the problem of current instability caused by the crosstalk of the ground loop is reduced, and the PCB board area is effectively reduced to achieve The purpose of reducing costs.

Description of drawings

Fig. 1 is a block diagram of the power architecture of the IW7027 chip in the prior art;

Fig. 2 is the block diagram of the power structure of IW7028 chip in the prior art;

Fig. 3 is a structural block diagram of the regional dimming constant current control circuit provided by the present invention;

Fig. 4 is a circuit diagram of the regional dimming constant current control circuit provided by the present invention.

Detailed ways

The invention provides a regional dimming constant current control circuit, a driving power supply and a TV set. By adopting a constant current drive module with a built-in boost control circuit and a dimming switch tube, the structure of the regional dimming light source is effectively optimized, and the ground wire is reduced. Loop crosstalk causes the problem of current instability, and at the same time effectively reduces the area of the PCB board to achieve the purpose of reducing costs.

In order to make the object, technical solution and effect of the present invention more clear and definite, the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Please refer to Fig. 3, the regional dimming constant current control circuit 10 provided by the present invention is connected with the AC-DC conversion circuit 20, the main board 30 and the backlight light bar 40, and the input alternating current is converted into direct current by the AC-DC conversion circuit 20 and then respectively output the first The first voltage and the second voltage are sent to the regional dimming constant current control circuit 10 and the main board 30 to supply power to both. After the main board 30 works, the control signal is output to the regional dimming constant current control circuit 10. The current control circuit 10 provides the corresponding working voltage for the backlight light bar 40, and adjusts the current of the corresponding channel light bar according to the control signal, so as to realize regional dimming. Specifically, the local dimming constant current control circuit 10 includes a dimming control module 11 and a constant current drive module 12 with a built-in boost control circuit and a multi-channel dimming switch tube, and the dimming control module 11 receives the main board 30 The output drive signal and dimming signal are transmitted to the constant current drive module 12, and the constant current drive module 12 boosts the first voltage output by the AC-DC conversion circuit 20 to a preset voltage according to the drive signal and then outputs it to the The backlight light strip 40, and adjust the grid duty cycle of the dimming switch tube of the corresponding channel according to the dimming signal, and then adjust the current of the corresponding channel. When it needs to be explained, the AC-DC conversion circuit 20 is a prior art, and its connection relationship will not be described in detail here.

In the present invention, since the constant current drive module 12 with a built-in boost control circuit and a multi-channel dimming switch tube is used, the area dimming constant current control circuit 10 is only composed of two circuit modules, that is, the constant current drive module 12 and dimming control module 11, the built-in boost control circuit makes the ground wire loop more concise, which can effectively reduce screen flicker or water ripple interference caused by ground wire crosstalk, and effectively optimize the structure of the regional dimming light source , and can also effectively reduce the area during PCB board wiring, reducing the production cost and the difficulty of designing and debugging the local dimming power supply.

Specifically, please refer to FIG. 4 together. 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. The data transmission unit 112 is connected to the constant current drive module 12; in this embodiment, the dimming control unit 111 receives the drive signal and the dimming signal output by the mainboard 30, and realizes communication with the constant current drive module 12 through the data transmission unit 112. I2C data transmission between them, output the drive signal and dimming signal to the constant current drive module 12, to ensure the stable transmission of digital control signals and provide the reliability of constant current control.

Further, the constant current drive module 12 includes a boost unit 121 and a constant current control unit 122 with a built-in boost control circuit and a multi-channel dimming switch tube, and the boost unit 121 is connected to the constant current control unit 122 and The backlight light bar 40, the constant current control unit 122 is also connected to the dimming control module 11; when driving the backlight light bar 40 to work, the constant current control unit 122 outputs a driving pulse to the boost unit according to the driving signal 121, driving the boost unit 121 to start working; the boost unit 121 boosts the first voltage output by the AC-DC conversion circuit 20 to a preset voltage and then outputs it to the backlight strip 40; the constant current control unit 122 also adjusts the gate duty cycle of the dimming switch tube of the corresponding channel according to the dimming signal, and then adjusts the current of the corresponding channel. That is, in the regional dimming constant current control circuit 10 provided by the present invention, the boost control circuit and the multi-channel dimming switch tube are built into the constant current control unit 122, and the Boost unit 121 is used to realize the boost voltage, and the AC-DC The first voltage output by the conversion circuit 20 is output to the backlight strip 40 after suppressing the preset voltage, so as to realize the normal operation of the backlight strip 40 .

Preferably, in order to ensure the stable operation of the backlight strip 40, the constant current control unit 122 also generates a detection voltage according to the actual working voltage of the backlight strip 40, and judges whether the current actual working voltage of the backlight strip 40 is is a preset voltage, and the duty cycle of the driving pulse is adjusted according to the judgment result. That is, the constant current control unit 122 can judge whether the current working voltage meets the specifications of the light bar according to the working voltage fed back by the backlight light bar 40, and adjust the voltage output to the backlight light bar 40 by itself. Specifically, when the boost unit 121 outputs When the voltage to the backlight strip 40 is too high, that is, when the actual working voltage of the front backlight strip 40 is greater than the preset voltage, the duty cycle of the driving pulse is reduced, so that the output voltage of the boost voltage is reduced until the preset voltage is output. voltage to the backlight strip 40, and when the voltage output from the booster unit 121 to the backlight strip 40 is too low, that is, when the actual working voltage of the current backlight strip 40 is less than the preset voltage, the duty cycle of the driving pulse is increased , so that the output voltage of the boosted voltage increases until the preset voltage is output to the backlight light bar 40 , so as to ensure the stable and safe operation of the backlight light bar 40 and improve the stability and reliability of the driving power supply.

Specifically, please continue to refer to FIG. 4 , the constant current control unit 122 includes a constant current control chip U1, and the first pin of the constant current control chip U1 is connected to the boost unit 121 for controlling the boost voltage. In the working state of the unit 121, the 5th, 6th and 7th pins of the constant current control chip U1 are all connected to the dimming control module 11 for data communication connection with the dimming control module 11 , the 14th to 20th pins of the constant current control chip U1 are all connected to the backlight light bar 40, which is the negative input end of the backlight light bar 40. In this embodiment, the constant current control chip U1 adopts the The constant current drive chip model is OZ556, which integrates DC-DC boost control terminal circuit and multi-channel dimming switch tube, which can simplify the power structure and reduce the ground loop crosstalk while realizing constant current control. In other embodiments, other constant current control chips U1 with the same function may also be used, which is not limited in the present invention.

Further, the boost 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, and a seventh resistor R7 , the eighth resistor R8, the ninth resistor R9, the tenth resistor R10, the first capacitor C1, the second capacitor C2, the third capacitor C3, the fourth capacitor C4, the first diode D1, the second diode D2, The first Zener diode ZD1, the second Zener diode ZD2 and the MOS transistor Q18.

One end of the inductance L1 is connected to the first voltage output end of the AC-DC conversion circuit 20 through the fuse F1, and the other end of the inductance L1 is connected to the anode of the second diode D2, the drain of the MOS transistor Q18 and the eighth resistor One end of R8; the negative pole of the second diode D2 is connected to one end of the second capacitor C2, the positive pole of the third capacitor C3, the positive pole of the fourth capacitor C4 and the backlight strip 40; the negative pole of the third capacitor C3 and The negative electrodes of the fourth capacitor C4 are both grounded; the other end of the second capacitor C2 is connected to the other end of the eighth resistor R8 and one end of the ninth resistor R9; the other end of the ninth resistor R9 is connected to the eighth resistor R8 One end of the first capacitor C1 and one end of the first capacitor C1; the other end of the first capacitor C1 is connected to the cathode of the second Zener diode ZD2, one end of the fifth resistor R5, one end of the sixth resistor R6, one end of the seventh resistor R7 and The source of the MOS transistor Q18; the anode of the second Zener diode ZD2, the other end of the fifth resistor R5, the other end of the sixth resistor R6 and the other end of the seventh resistor R7 are all grounded; the other end of the MOS transistor Q18 The gate is connected to the cathode of the first zener diode ZD1, the anode of the first diode D1, one end of the second resistor R2 and one end of the third resistor R3; the anode of the first zener diode ZD1 is connected to the fifth resistor R5 One end of the first resistor R3, the other end of the third resistor R3 and one end of the fourth resistor R4; the cathode of the first diode D1 is connected to one end of the first resistor R1; the other end of the first resistor R1 is connected to the second resistor The other end of R2 and one end of the tenth resistor R10; the other end of the fourth resistor R4 is connected to the 22nd pin of the constant current control chip U1; the other end of the tenth resistor R10 is connected to the constant current control chip Pin 1 of U1. After the main board 30 works, the constant current control chip U1 outputs the drive pulse DRV to the MOS transistor Q18 of the boost unit 121 according to the received drive signal, the boost unit 121 starts to work, the inductor L1 starts to charge and discharge, and the energy passes through the second diode After rectification and filtering by D2 and the fourth capacitor C4, the first voltage (48V in this embodiment) output by the AC-DC conversion voltage is boosted to the preset voltage (80V in this embodiment), and the backlight is fed through the light bar socket CN1 The light bar 40 supplies power, and then returns to the inside of the constant current control chip U1 through the negative terminal of the light bar.

Further, the dimming control unit 111 includes a microcontroller U2, the 7th pin, the 12th pin and the 15th pin of the microcontroller U2 are connected to the main board 30 for receiving ON/OFF, ENA, SCK, CSB and other control signals, the second pin, the third pin and the nineteenth pin of the microcontroller U2 are all connected to the constant current drive module 12 for realizing the I2C between the constant current drive module 12 Data transmission ensures the stability of signal transmission. In this embodiment, the microcontroller U2 is an MCU with a model of MSP430G2433IPW20R. Of course, in other embodiments, other microcontrollers U2 with the same function can also be used, which is not limited in the present invention.

Furthermore, 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 second pin of the microcontroller U2, and the eleventh resistor R11 The other end is connected to the constant current drive module 12, specifically the sixth pin of the constant current control chip U1; one end of the twelfth resistor R12 is connected to the third pin of the microcontroller U2, and the twelfth resistor The other end of R12 is connected to the constant current drive module 12, specifically connected to the 7th pin of the constant current control chip U1; the eleventh resistor R11 and the twelfth resistor R12 form an I2C data transmission circuit, which realizes the connection with the constant current. SPI bus communication of flow control chip U1.

Preferably, in order to further optimize the performance of the local dimming constant current control circuit 10, the constant current drive module 12 further includes a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, Seventeenth resistor R17, eighteenth resistor R18, nineteenth resistor R19, twentieth resistor R20, twenty-first resistor R21, twenty-second resistor R22, twenty-third resistor R23, twenty-fourth resistor R24, twenty-fifth resistor R25, fifth capacitor C5, sixth capacitor C6, seventh capacitor C7, eighth capacitor C8, ninth capacitor C9, tenth capacitor C10 and eleventh capacitor C11.

One end of the thirteenth resistor R13 is connected to the cathode of the second diode D2, and the other end of the thirteenth resistor R13 is connected to one end of the fourteenth resistor R14 and the 20th pin and the fifth pin of the constant current control chip U1. One end of the capacitor C5, 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 to the ENA signal end, the The other end of the sixteenth resistor R16 is connected to one end of the seventeenth resistor R17, one end of the sixth capacitor C6 and the third pin of the constant current control chip U1; the other end of the seventeenth resistor R17 is connected to the sixth capacitor C6 The other ends are both grounded; one end of the seventh capacitor C7 is connected to the 12V power supply end, one end of the eighth capacitor C8 and the fourth pin of the constant current control chip U1, the other end of the seventh capacitor C7 is connected to the eighth capacitor C8 The other ends are both grounded; one end of the eighteenth resistor R18 is connected to the fifth pin of the constant current control chip U1, and the other end of the eighteenth resistor R18 is connected to the nineteenth pin of the microcontroller U2; the nineteenth resistor One end of the 20th resistor is connected to the 8th pin of the constant current control chip U1, the other end of the nineteenth resistor R19 is connected to the 13th pin of the microcontroller U2; the other end of the twentieth resistor R20 is connected to 3.3V power supply terminal and the ninth pin of the constant current control chip U1; one end of the twenty-first resistor R21 is connected to the tenth pin of the constant current control chip U1; one end of the twenty-second resistor R22 is connected to the constant current control The 11th pin of the chip U1; one end of the twenty-third resistor R23 is connected to the twelfth pin of the constant current control chip U1, and the other end of the twenty-third resistor R23 is grounded through the ninth capacitor C9; the second One end of the fourteenth resistor R24 and one end of the twenty-fifth resistor R25 are connected to the 13th pin of the constant current control chip U1; one end of the tenth capacitor C10 is connected to the 22nd pin of the constant current control chip U1; the tenth capacitor C10 is connected to the 22nd pin of the constant current control chip U1; One end of a capacitor C11 is connected to the second pin of the constant current control chip U1, 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 second The other end of the fifteenth resistor R25, the other end of the tenth capacitor C10 and the other end of the eleventh capacitor C11 are all grounded;

Among them, the thirteenth resistor R13, the fourteenth resistor R14, the fifteenth resistor R15, and the fifth capacitor C5 are overvoltage protection circuits, which provide overvoltage protection for the backlight strip 40 and improve the safety of the circuit; the sixteenth resistor R16 1. The seventeenth resistor R17 and the sixth capacitor C6 are the backlight switch circuit, which receives the ENA enable signal to drive the chip to start working, so as to realize the turning on and off of the backlight light strip 40; the seventh capacitor C7 and the eighth capacitor C8 are the power supply filter circuit After filtering the first voltage output by the AC-DC conversion circuit 20, the chip is powered to filter out clutter and ensure the stability of the chip power supply; the eighteenth resistor R18 is mainly used for synchronous signal input; the first The nineteenth resistor R19 and the twentieth resistor R20 are mainly used to judge the identification input; the twenty-first resistor R21 and the twenty-second resistor R22 are mainly used to set the operating frequency of the chip; the twenty-third resistor R23 and The ninth capacitor C9 is mainly used for loop compensation to achieve voltage regulation and feedback protection; the twenty-fourth resistor R24 and the twenty-fifth resistor R25 are mainly used to set the current of the light bar to achieve dimming; The eleventh capacitor C11 is used to provide a reference voltage for the constant current control chip U1, and the tenth capacitor C10 is mainly used for overcurrent detection to ensure that the driving current is within a safe range and improve circuit safety.

Further, the dimming control module 11 also includes a twenty-sixth resistor R26, a twenty-seventh resistor R27, a twenty-eighth resistor R28, a twenty-ninth resistor R29, a thirtieth resistor R30, a twelfth capacitor C12, the thirteenth capacitor C13, the fourteenth capacitor C14, the fifteenth capacitor C15, the light-emitting diode LED1 and the programming socket CN2; one end of the twenty-sixth resistor R26 is connected to the 3.3V power supply end, and the twenty-sixth resistor R26 is connected to the 3.3V power supply terminal. The other end of the six resistors R26 is connected to one end of the twelfth capacitor C12, one end of the thirteenth capacitor C13, one end of the fourteenth capacitor C14 and the first pin of the microcontroller U2; the other end of the twelfth capacitor C12 1. The other end of the thirteenth capacitor C13 and the other end of the fourteenth capacitor C14 are both grounded; one end of the twenty-seventh resistor R27 is connected to the 4th pin of the programming socket CN2, and the second end of the twenty-seventh resistor R27 The other end is connected to one end of the twenty-eighth resistor R28 and the 3.3V power supply end; the other end of the twenty-eighth resistor R28 is connected to the second pin of the programming socket CN2 and one end of the twenty-ninth resistor R29; The other end of the twenty-ninth resistor R29 is connected to the 16th pin of the microcontroller U2 and one end of the fifteenth capacitor C15; one end of the thirtieth resistor R30 is connected to the third pin of the programming socket CN2, and the thirtieth The other end of the resistor R30 is connected to the 17th pin of the microcontroller U2; the 1st pin of the programming socket CN2 is grounded; the anode of the light-emitting diode LED1 is connected to the 10th pin of the microcontroller U2, and the light-emitting diode LED1 Negative ground.

Wherein, the twenty-sixth resistor R26, the twelfth capacitor C12, the thirteenth capacitor C13 and the fourteenth capacitor C14 are the power supply circuit of the microcontroller U2, and provide a stable working voltage for the microcontroller U2; The light-emitting diode LED1 is the working indicator light of the microcontroller U2, through which the light-emitting diode LED1 outputs the working status information of the current microcontroller U2, so that the user can quickly judge the usage of the current microcontroller U2, for example, it is always on to indicate that it is normal Working, always off means it stops working, flashing means its working abnormally, etc.; the 27th resistor R27, the 28th resistor R28, the 29th resistor R29, the 30th resistor R30, the fifteenth capacitor C15 and the programming socket CN2 are programming software circuits, which realize programming, erasing and writing operations of software programs, and improve the application flexibility of the microcontroller U2.

It should be noted that the remaining components not labeled in the figure, such as resistors, capacitors and Zener diodes, are conventional components of the microcontroller U2 and the peripheral working circuit of the constant current control chip U1, which are prior art. The connection relationship is not described here.

Based on the above-mentioned regional dimming constant current control circuit 10, the present invention also provides a driving power supply correspondingly, including a housing, and a PCB board is arranged inside the housing, and the above-mentioned regional dimming constant current control circuit is arranged on the PCB board. As for the circuit 10, since the local dimming constant current control circuit 10 has been described in detail above, it will not be described in detail here.

The present invention also correspondingly provides a television set, including the above-mentioned driving power supply, since the above-mentioned driving power supply has been described in detail, it will not be described in detail here.

In order to better understand the control process of the regional dimming constant current control circuit 10 provided by the present invention, the working process of the regional dimming constant current control circuit 10 will be described below in conjunction with FIG. 3 and FIG. 4 citing an application example:

After starting up, the AC input voltage passes through the AD-DC conversion circuit to provide 48V and 12V voltages, of which 12V supplies power to the mainboard 30 and the constant current control chip U1, and 12V obtains 3.3V through the three-terminal voltage regulator to supply power to the microcontroller U2. After the main board 30 works, it provides control signals such as ON/OFF, ENA, SCK, CSB, etc., and the microcontroller U2 starts to work, and sends the constant current control chip U1 to the constant current control chip U1 through the SCL, SDA, and VSYNC data lines, and the constant current control chip U1 outputs driving pulses DRV is given to the MOS transistor Q18 in the boost unit 121, the boost unit 121 starts to work, the energy storage inductor L1 starts to charge and discharge, and the energy is rectified and filtered by the second diode D2 and the fourth capacitor C4 to output a constant DC voltage to the backlight The light bar 40 supplies power, and then returns to the constant current control chip U1 through the negative terminal of the light bar. The constant current control chip U1 detects the internal voltage according to the received control signal, that is, generates a detection voltage, and judges the current boost unit according to the detection voltage Whether the voltage output by 121 meets the specification of the light bar. If the voltage output by the boost unit 121 is too low, the constant current control chip U1 increases the duty cycle of the driving pulse to increase the output voltage. If the output voltage of the boost unit 121 If the voltage is too high, the constant current control chip U1 will reduce the duty cycle of the large driving pulse to reduce the output voltage to meet the specification of the backlight strip 40. When local dimming is required, the main board 30 will pass VSYNC The dimming command is sent to the microcontroller U2, and the microcontroller U2 is converted and output to the constant current control chip U1 through the SCL, SDA, VSYNC data lines, and the constant current control chip U1 controls the corresponding channel to adjust the constant current control chip U1. Corresponding to the gate duty cycle of the channel dimming switch tube, the current of the channel is changed to meet the requirements of regional dimming.

To sum up, in the regional dimming constant current control circuit, the driving power supply and the TV set provided by the present invention, the regional dimming constant current control circuit is connected with the AC-DC conversion circuit, the main board and the backlight strip, which includes a dimming A light control module and a constant current drive module with a built-in boost control circuit and a multi-channel dimming switch; The module boosts the first voltage output by the AC-DC conversion circuit to a preset voltage according to the driving signal and then outputs it to the backlight strip, and adjusts the gate duty cycle of the dimming switch tube of the corresponding channel according to the dimming signal , and then adjust the current size of the corresponding channel. By adopting the built-in boost control circuit and the constant current drive module of the dimming switch tube, the structure of the regional dimming light source is effectively optimized, the problem of current instability caused by the crosstalk of the ground loop is reduced, and the PCB board area is effectively reduced to achieve The purpose of reducing costs.

It can be understood that those skilled in the art can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention, and all these changes or replacements should belong to the protection scope of the appended claims of the present invention.

Claims (10)

1. a kind of local dimming constant-current control circuit, connect, feature exists with AC-DC conversion circuits, mainboard and backlight lamp bar In the constant-current driven module including dimming controlling module and built-in boost control circuit and multichannel dimmer switch pipe；By adjusting The drive signal and dim signal of the reception mainboard output of photocontrol module are simultaneously transmitted to constant-current driven module, and the constant current drives mould Root tuber is exported after the first voltage that AC-DC conversion circuits export is boosted to predeterminated voltage according to the drive signal to backlight Item, and according to the grid duty ratio of dim signal adjusting corresponding channel dimmer switch pipe, and then adjust the electricity of corresponding channel Flow size.

2. local dimming constant-current control circuit according to claim 1, which is characterized in that the constant-current driven module includes The constant-current control unit of boosting unit and built-in boost control circuit and multichannel dimmer switch pipe；By the constant-current control unit According to the drive signal output driving pulse to boosting unit, the boosting unit is driven to start to work；The boosting unit It is exported after the first voltage that AC-DC conversion circuits export is boosted to predeterminated voltage to backlight lamp bar；The constant-current control unit The grid duty ratio of corresponding channel dimmer switch pipe is adjusted also according to the dim signal, and then the electric current for adjusting corresponding channel is big It is small.

3. local dimming constant-current control circuit according to claim 2, which is characterized in that the constant-current control unit also root According to the real work voltage generation detection voltage of backlight lamp bar, the practical work of current backlight lamp bar is judged according to the detection voltage Make whether voltage is predeterminated voltage, and the duty ratio of the driving pulse is adjusted according to judging result.

4. local dimming constant-current control circuit according to claim 1, which is characterized in that the dimming controlling module includes Dimming control unit and data transmission unit receive the drive signal of mainboard output by the dimming control unit and light modulation are believed Number, and pass through the data transmission unit and export the drive signal and dim signal to constant-current driven module.

5. local dimming constant-current control circuit according to claim 2, which is characterized in that the constant-current control unit includes Current constant control chip, the 1st foot connection boosting unit of the current constant control chip, the 5th foot of the current constant control chip, 6th foot and the 7th foot are all connected with the dimming controlling module, and the 14th foot to the 20th foot of the current constant control chip is all connected with backlight Lamp bar.

6. local dimming constant-current control circuit according to claim 5, which is characterized in that the boosting unit includes electricity Sense, first resistor, second resistance, 3rd resistor, the 4th resistance, the 5th resistance, the 6th resistance, the 7th resistance, the 8th resistance, Nine resistance, the tenth resistance, the first capacitance, the second capacitance, third capacitance, the 4th capacitance, the first diode, the second diode, One zener diode, the second zener diode and metal-oxide-semiconductor；

The first voltage output terminal of one end connection AC-DC conversion circuits of the inductance, the other end connection second of the inductance The drain electrode of the anode, metal-oxide-semiconductor of diode and one end of the 8th resistance；The cathode of second diode connects the one of the second capacitance End, the anode and backlight lamp bar of the anode of third capacitance, the 4th capacitance；The cathode of the third capacitance and the cathode of the 4th capacitance It is grounded；The other end of second capacitance connects the other end of the 8th resistance and one end of the 9th resistance；Described 9th The other end of resistance connects one end of the 8th resistance and one end of the first capacitance；The other end connection second of first capacitance is steady Press one end, one end of the 7th resistance and the source electrode of metal-oxide-semiconductor of the cathode of diode, one end of the 5th resistance, the 6th resistance；It is described The anode of second zener diode, the other end of the 5th resistance, the other end of the 6th resistance and the other end of the 7th resistance connect Ground；The metal-oxide-semiconductor grid connection the cathode of the first zener diode, the anode of the first diode, second resistance one end and One end of 3rd resistor；One end of anode the 5th resistance of connection of first zener diode, the volume other end of 3rd resistor With one end of the 4th resistance；One end of the cathode connection first resistor of first diode；The other end of the first resistor Connect the other end of second resistance and one end of the tenth resistance；The other end of 4th resistance connects the current constant control chip The 22nd foot；The other end of tenth resistance connects the 1st foot of the current constant control chip.

7. local dimming constant-current control circuit according to claim 4, which is characterized in that the dimming control unit includes Microcontroller, the 7th foot, the 12nd foot and the 15th foot of the microcontroller are connect with mainboard, the 2nd foot of the microcontroller, the 3rd Foot and the 19th foot are all connected with the constant-current driven module.

8. local dimming constant-current control circuit according to claim 7, which is characterized in that the data transmission unit includes 11st resistance and the 12nd resistance；2nd foot of one end connection microcontroller of the 11st resistance, the 11st resistance The other end connect the constant-current driven module；3rd foot of one end connection microcontroller of the 12nd resistance, the described tenth The other end of two resistance connects the constant-current driven module.

9. a kind of driving power including shell, pcb board is provided in the shell, which is characterized in that set on the pcb board Just like the local dimming constant-current control circuit described in claim 1-8 any one.

10. a kind of television set, which is characterized in that including driving power as claimed in claim 9.