CN217690457U

CN217690457U - Closed-loop high-dynamic dimming Mini LED backlight driving circuit

Info

Publication number: CN217690457U
Application number: CN202220950145.8U
Authority: CN
Inventors: 毛鹏; 褚俊杰; 段世太
Original assignee: Suzhou Northen Microelectronics Technology Co ltd
Current assignee: Suzhou Northen Microelectronics Technology Co ltd
Priority date: 2022-04-21
Filing date: 2022-04-21
Publication date: 2022-10-28
Anticipated expiration: 2032-04-21

Abstract

The application discloses a Mini LED backlight driving circuit of closed loop high dynamic dimming. The Mini LED backlight driving circuit comprises an EMI filtering and Boost PFC power factor correction circuit, an auxiliary power circuit, a half-bridge LLC resonant converter and an LED backlight board driving control circuit. The utility model provides a Mini LED drive circuit is shaded that closed loop high dynamic was adjusted luminance has following beneficial effect: 1) The Mini LED backlight driving circuit has the functions of EMI filtering and power factor correction, improves the power consumption quality, reduces the circuit loss and has higher anti-interference capability. 2) The backlight driving circuit adopts a closed-loop control mode, improves the state change speed of the LED and the dynamic regulation speed of the power supply current, and has a high dynamic regulation function.

Description

Closed-loop high-dynamic dimming Mini LED backlight driving circuit

Technical Field

The utility model relates to a Mini LED technical field that is shaded especially relates to a Mini LED drive circuit that is shaded of high dynamic of closed loop.

Background

In recent years, mini LEDs have attracted much attention because of the advantages of many light sources, fine display effect, long lifetime, high contrast, high brightness, and the like, which appear in the public field of view many times; the Mini LED backlight scheme is particularly suitable for the market demands of light and thin portable equipment, commercial displays and the like, and has the advantages in the fields of commercial display, intelligent electronic product decorative lamps, detection device display screens and the like. The Mini LED has the same voltage type driving and current type driving as the traditional LED driving mode, and the current type driving is mostly adopted in the current driving mode of the LED because the constant current driving is more suitable for the volt-ampere characteristic of the diode. At present, there are two scanning modes in the backlight scheme of the Mini LED display screen, namely static scanning and dynamic scanning, and the static scanning of the display screen: the main control chip is stored through the latch after outputting the display instruction every time, so that the display is kept unchanged, and the MCU updates the content latched in the digital display of the display screen only when the display content needs to be changed. Dynamic scanning of the LED display screen: the MCU is required to scan each section of LED lamp strip regularly, each section of LED lamp strip works in turn in a time-sharing mode, and only one section of LED lamp strip can be displayed each time. In any scanning mode, due to the low visual resolution of human eyes, all the LED lamp strips are still felt to be displayed at the same time. Although the change of the on/off of the LED lamp strip cannot be seen clearly by human eyes, equipment such as machine vision, industrial detection and the like is not available, and due to the fact that the corresponding speed of a sensor of the equipment is high, the change of the on/off of the LED lamp strip can be captured easily, and therefore a shot picture is not clear. Two main factors causing the problem are provided, one is the scanning problem mentioned above, and the end is the problem that the dynamic adjustment speed of the LED lamp strip is too slow; the other is caused by unstable output current, the brightness of the LED lamp strip is directly determined by the size of the output current, and if the output current is unstable, the problem of backlight flicker can occur.

SUMMERY OF THE UTILITY MODEL

To the problem mentioned above, the utility model provides a Mini LED drive circuit is shaded to high developments of closed loop. The circuit can improve the adjusting speed of the supply current of the backlight plate and the reaction speed of the LED lamp beads, and also improves the problem of low resolution of the Mini LED display screen by improving the dynamic adjusting speed of the LED.

In order to achieve the above object, an embodiment of the present invention provides a closed-loop high dynamic dimming Mini LED backlight driving circuit, which includes an EMI filter and Boost PFC power factor correction circuit, an auxiliary power circuit, a half-bridge LLC resonant converter, and an LED backlight driving control circuit; the input end of the EMI filtering and Boost PFC power factor correction circuit is connected to a mains supply, the output end of the EMI filtering and Boost PFC power factor correction circuit is connected to the auxiliary power circuit and the half-bridge LLC resonant converter, the auxiliary power circuit is located between the EMI filtering and Boost PFC power factor correction circuit and the half-bridge LLC resonant converter, and the LED backlight board drive control circuit is connected to the output end of the half-bridge LLC resonant converter; the LED backlight board driving control circuit comprises a second closed-loop control loop, the second closed-loop control loop is connected to the half-bridge LLC resonant converter, and the LED backlight board driving control circuit is connected to the second closed-loop control loop; the second closed-loop control loop acquires an output current sample Is and an output voltage sample Vo of the half-bridge LLC resonant converter; the output current Io and the output current sampling Is of the half-bridge LLC resonant converter are input into the LED backlight board drive control circuit, and the LED backlight board drive control circuit outputs an error output signal Ie to the second closed-loop control loop so as to adjust the output current Io of the half-bridge LLC resonant converter; the LED backlight board driving control circuit comprises an in-phase proportional amplification circuit, a PI controller, a main control chip MCU, a switch tube Q5 and an LED lamp board; the LED lamp panel is provided with an LED lamp bead, a branch formed by connecting the LED lamp bead with a resistor R8 and a capacitor C8 in parallel is connected with an inductor L3 in series to form a steady-flow light-emitting circuit, the output current Io of the half-bridge LLC resonant converter is input into the input end of the steady-flow light-emitting circuit, the steady-flow light-emitting circuit is connected with an RCD absorption unit in parallel and then is connected to the drain electrode of a switch tube Q5 through a resistor R13, the source electrode of the switch tube Q5 is grounded through a resistor R14, the main control chip MCU acquires the driving current Id at the position of the source electrode of the switch tube Q5, and the main control chip MCU outputs a dimming signal PWM to the grid electrode of the switch tube Q5; the PI controller comprises an operational amplifier U1B, and a capacitor C13 and a resistor R19 are connected in series between an inverting input end and an output end of the operational amplifier U1B; the main control chip MCU outputs a reference current Iref to a non-inverting input end of the operational amplifier U1B after processing the driving current Id and the duty ratio of the output PWM dimming signal; the output current sampling Is amplified by the in-phase proportional amplifying circuit and then Is connected to the inverting input end of the operational amplifier U1B through a resistor R18; and the difference value of the output current amplified by the in-phase proportional amplifying circuit and the reference current Iref is calculated by the PI controller to output an error output signal Ie, and the error output signal Ie is sent into the second closed-loop control loop to realize closed-loop control on the output current Io.

Further, the in-phase proportional amplifying circuit comprises an operational amplifier U1A, the output current sample Is connected to the non-inverting input end of the operational amplifier U1A through a resistor R17, the inverting input end of the operational amplifier U1A Is grounded through a resistor R16, and a branch formed by connecting a resistor R15 and a capacitor C10 in parallel Is further arranged between the output end and the inverting input end of the operational amplifier U1A; the output end of the operational amplifier U1A is connected to the inverting input end of the operational amplifier U1B through a resistor R18.

Further, the model of the main control chip MCU is EP2C8T144C8; the input voltage of the main control chip MCU is 3.3V.

Furthermore, the EMI filtering and Boost PFC power factor correction circuit comprises an EMI filtering unit and a power factor correction unit; the EMI filtering unit comprises a common-mode inductor Lcm1, a common-mode inductor Lcm2, a capacitor CX1, a capacitor CX2, a capacitor CX3, a capacitor CY1, a capacitor CY2, a capacitor CY3 and a capacitor CY4; the power factor correction unit comprises a rectifier bridge BD1, a Boost circuit and a first control loop; the rectifier bridge BD1 is provided with a rectification anode output end, a rectification cathode output end, a first alternating current input end and a second alternating current input end; the common-mode inductor Lcm1 and the common-mode inductor Lcm2 are both provided with two input ends and two output ends, the common-mode inductor Lcm1 and the common-mode inductor Lcm2 are connected in series, two input ends of the common-mode inductor Lcm1 are connected with an alternating current mains supply, the capacitor CX1 is connected between the two input ends of the common-mode inductor Lcm1 and is connected with a branch formed by connecting the capacitor CY1 and the capacitor CY2 in series, a node between the capacitor CY1 and the capacitor CY2 is grounded, the capacitor CX2 is connected between the two output ends of the common-mode inductor Lcm1 and is connected with a branch formed by connecting the capacitor CY3 and the capacitor CY4 in series, a node between the capacitor CY3 and the capacitor CY4 is grounded, the capacitor CX3 is connected between the two output ends of the common-mode inductor Lcm2 and is respectively connected to the first alternating current input end and the second alternating current input end, and the Boost circuit is connected between the rectification positive output end and the rectification negative output end; the mains supply is rectified by the rectifier bridge BD1 to obtain direct current, the direct current is subjected to closed-loop control by the Boost circuit to obtain stable output voltage VDC, and the output voltage VDC is output from the output end of the power factor correction unit; the Boost circuit comprises an inductor L1, a resistor R1, a diode D1, a capacitor C1, a switching tube Q1, a resistor R2 and a resistor R3; an inductor L1, a resistor R1, a diode D1, a resistor R2 and a resistor R3 are sequentially connected in series between the rectification anode output end and the rectification cathode output end of the rectifier bridge BD1, and the capacitor C1 is connected in parallel with a branch formed by connecting the resistor R2 and the resistor R3 in series; a switching tube Q1 is further arranged between the connecting node of the resistor R1 and the diode D1 and the output end of the rectification negative electrode, and the output voltage VDC is output from two ends of the capacitor C1; the first control loop comprises a main control chip NCP1654, the output voltage VDC is divided by a resistor R2 and a resistor R3 to form an output voltage sample and is input to the main control chip NCP1654, the input voltage sample is output to the main control chip NCP1654 at the rectifying positive electrode output end, and the input current sample is output to the main control chip NCP1654 at the connection node of the inductor L1 and the resistor R1; the main control chip NCP1654 is connected to the grid electrode of the switch tube Q1.

Furthermore, the half-bridge LLC resonant converter is provided with a VDC + input end and a VDC-input end; the VDC + input end and the VDC-input end are respectively connected to the output end of the power factor correction unit; the half-bridge LLC resonant converter comprises a transistor Q2, a transistor Q3, a capacitor C2, an inductor L2, a first transformer T1, a diode D2, a diode D3, a capacitor C3, a resistor R4, a resistor R5 and a second control loop; the first transformer T1 is provided with an input coil N1, an output coil N2 and an output coil N3, and the output coil N2 and the output coil N3 are arranged in series; the second control loop comprises a main control chip L6599A; the VDC-input end is grounded, a transistor Q2 and a transistor Q3 are arranged between the VDC + input end and the VDC-input end in series, the gates of the transistor Q2 and the transistor Q3 are connected to the output end of the second control loop, a capacitor C2, an inductor L2 and an input coil N1 are connected between the transistor Q2 and the transistor Q3 in series, one end of the output coil N2 is connected to one end of the capacitor C3 through a diode D2 and outputs a voltage Vo, the other end of the output coil N2 is connected to the other end of the capacitor C3 and grounded, the capacitor C3 and a branch formed by connecting the resistor R4 and the resistor R5 in series are arranged in parallel, one end of the output coil N3 is connected to the output coil N2, and the other end of the output coil N3 is connected to the negative electrode of the diode D2 through a diode D3; an output current sample Is between the resistor R4 and the resistor R5 Is input to the second control loop, and the output voltage sample Vo Is input to the second control loop.

Further, the auxiliary source circuit comprises a second transformer T2, and the second transformer T2 is provided with an input coil W1 and an output coil W2; the two ends of a branch formed by serially connecting the input coil W1 with a switching tube Q4 are connected to the output end of the EMI filtering and Boost PFC power factor correction circuit; one end of the output coil W2 is connected to the anode of a diode D4, a capacitor C5 is connected between the cathode of the diode D4 and the other end of the output coil W2, the other end of the output coil W2 is grounded, the diode D4 is connected in parallel with a branch circuit formed by serially connecting the capacitor C4 and a resistor R6, and the cathode of the diode D4 outputs a first auxiliary voltage.

Further, in the auxiliary source circuit, the second transformer T2 is further provided with an output coil W3; one end of the output coil W3 is connected with the output coil W2 in series; the other end of the output coil W3 is connected to the anode of a diode D5, the cathode of the diode D5 is connected with one side of a capacitor C6, the other side of the capacitor C6 is grounded, the diode D5 is connected with a branch circuit formed by serially connecting a capacitor C7 and a resistor R9 in parallel, and the cathode of the diode D5 outputs a second auxiliary voltage.

Further, the first auxiliary voltage is 15V; the second auxiliary voltage is 5V.

Further, the first auxiliary voltage is input to the second closed loop control circuit and the first closed loop control circuit; and the second auxiliary voltage is regulated by a chip XC6201 and then is input to the main control chip MCU.

Further, the chip XC6201 is provided with a first pin, a second pin, and a third pin, the first pin inputs the second auxiliary voltage, the second pin is grounded, the second pin is connected to the first pin through a capacitor C11, the second pin is connected to the third pin through a capacitor C12, and the third pin is connected to the main control chip MCU.

The utility model provides a Mini LED drive circuit that is shaded that closed loop high dynamic was adjusted luminance has following beneficial effect: 1) The Mini LED backlight driving circuit has the functions of EMI filtering and power factor correction, improves the power consumption quality, reduces the circuit loss and has higher anti-interference capability. 2) The backlight driving circuit adopts a closed-loop control mode, improves the state change speed of the LED and the dynamic regulation speed of the power supply current, and has a high dynamic regulation function.

Drawings

The technical solution and other advantages of the present application will be presented in the following detailed description of specific embodiments of the present application with reference to the accompanying drawings.

Fig. 1 is a schematic circuit structure diagram of a closed-loop high dynamic dimming Mini LED backlight driving circuit according to an embodiment of the present application.

Fig. 2 is a schematic circuit structure diagram of an EMI filter and Boost PFC power factor correction circuit according to an embodiment of the present disclosure.

Fig. 3 is a schematic circuit structure diagram of a half-bridge LLC resonant converter provided in the embodiment of the present application.

Fig. 4 is a schematic circuit structure diagram of an auxiliary source circuit according to an embodiment of the present disclosure.

Fig. 5 is a schematic circuit structure diagram of a driving control circuit of an LED backlight panel according to an embodiment of the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; may be mechanically connected, may be electrically connected or may be in communication with each other; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as the case may be.

The following disclosure provides many different embodiments or examples for implementing different features of the application. In order to simplify the disclosure of the present application, specific example components and arrangements are described below. Of course, they are merely examples and are not intended to limit the present application. Moreover, the present application may repeat reference numerals and/or letters in the various examples, such repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. In addition, examples of various specific processes and materials are provided herein, but one of ordinary skill in the art may recognize applications of other processes and/or use of other materials.

In order to realize the above-mentioned planning function, a path of light strip in the Mini LED backlight board is taken as an example for description.

The method comprises the steps of firstly carrying out EMI noise reduction treatment on an alternating current input end of a Mini LED backlight board driving circuit, and then carrying out voltage conversion by adopting a two-stage architecture, wherein a Boost PFC power factor correction circuit is adopted at the front stage, and a half-bridge resonance LLC isolation type circuit is adopted at the rear stage. In order to ensure the normal operation of the circuit system, some necessary hardware circuits are added on the basis of the architecture, and the specific circuits comprise the following parts:

EMI filters and Boost PFC power factor correction circuit: a power supply of the Mini LED backlight plate needs to take power from a power grid, EMI filtering and power factor correction need to be carried out to avoid interference, 220V alternating current voltage is adjusted by a Boost PFC and a closed-loop control circuit 1 thereof after being subjected to EMI filtering, direct current bus voltage VDC with the output of 400V is obtained, and a power supply chip adopted by the closed-loop control circuit 1 is NPC1654;

2.Mini LED backlight half-bridge resonance LLC supply circuit: the method comprises the following steps that an input mains supply is subjected to EMI filtering and power factor correction unit to obtain a direct current bus voltage VDC serving as a post-stage input voltage, and an output current Io for supplying power to an LED backlight plate can be obtained after the direct current bus voltage VDC is adjusted by an LLC resonant converter and a closed-loop control circuit 2 of the LLC resonant converter, wherein the closed-loop control circuit 2 adopts a power chip L6599A special for the LLC converter;

3.Mini LED board auxiliary power supply circuit that backlights: in order to enable the whole drive control circuit to work stably and effectively, two auxiliary voltages are generated through an auxiliary power supply circuit, and stable 5V and 15V power supply voltages are provided for chips such as NCP1654, L6599A and the like and other circuits in the whole drive circuit, so that each circuit can work normally;

4.Mini LED backlight drive control circuit: the circuit is mainly used for realizing the high dynamic dimming function of the Mini LED. In order to solve the problems of low resolution and slow extinguishing speed of the traditional LED, an additional RCD absorption unit is added to the backlight plate and used for absorbing energy stored in a circuit capacitor and an inductor at the moment of turning off the LED and accelerating the extinguishing speed of the LED. In addition, the MCU samples the driving current Id flowing through the LED, outputs the reference current Iref after processing the Id and the duty ratio of the output PWM dimming signal, then performs PI regulation on the Iref and an error signal of the sampled and amplified output current value, and finally sends the output of the PI regulation into the closed-loop control loop 2, thereby realizing the closed-loop dynamic control of the output current. The model of the MCU adopted as the main control chip is EP2C8T144C8.

Specifically, referring to fig. 1 to 5, in one embodiment of the present invention, a closed-loop high dynamic dimming Mini LED backlight driving circuit is provided, which includes an EMI filter and Boost PFC power factor correction circuit, an auxiliary power circuit, a half-bridge LLC resonant converter, and an LED backlight driving control circuit; the input end of the EMI filtering and Boost PFC power factor correction circuit is connected to a mains supply, the output end of the EMI filtering and Boost PFC power factor correction circuit is connected to the auxiliary power circuit and the half-bridge LLC resonant converter, the auxiliary power circuit is located between the EMI filtering and Boost PFC power factor correction circuit and the half-bridge LLC resonant converter, and the LED backlight board drive control circuit is connected to the output end of the half-bridge LLC resonant converter; the LED backlight board driving control circuit comprises a second closed-loop control loop, the second closed-loop control loop is connected to the half-bridge LLC resonant converter, and the LED backlight board driving control circuit is connected to the second closed-loop control loop; the second closed-loop control loop acquires an output current sample Is and an output voltage sample Vo of the half-bridge LLC resonant converter; the output current Io and the output current sampling Is of the half-bridge LLC resonant converter are input into the LED backlight board drive control circuit, and the LED backlight board drive control circuit outputs an error output signal Ie to the second closed-loop control loop so as to adjust the output current Io of the half-bridge LLC resonant converter; the LED backlight board driving control circuit comprises an in-phase proportional amplification circuit, a PI controller, a main control chip MCU, a switch tube Q5 and an LED lamp board; the LED lamp panel is provided with an LED lamp bead, a branch formed by connecting the LED lamp bead in parallel with a resistor R8 and a capacitor C8 is connected in series with an inductor L3 to form a steady-flow light-emitting circuit, the output current Io of the half-bridge LLC resonant converter is input to the input end of the steady-flow light-emitting circuit, the steady-flow light-emitting circuit is connected in parallel with the RCD absorption unit and then is connected to the drain electrode of the switching tube Q5 through a resistor R13, the source electrode of the switching tube Q5 is grounded through a resistor R14, the main control chip MCU acquires the driving current Id at the position of the source electrode of the switching tube Q5, and the main control chip MCU outputs a dimming signal PWM to the grid electrode of the switching tube Q5; the PI controller comprises an operational amplifier U1B, and a capacitor C13 and a resistor R19 are connected in series between an inverting input end and an output end of the operational amplifier U1B; the main control chip MCU outputs reference current Iref to the non-inverting input end of the operational amplifier U1B after processing the driving current Id and the duty ratio of the output PWM dimming signal; the output current sampling Is amplified by the in-phase proportional amplifying circuit and then Is connected to the inverting input end of the operational amplifier U1B through a resistor R18; and the difference value of the output current amplified by the in-phase proportional amplifying circuit and the reference current Iref is calculated by the PI controller to output an error output signal Ie, and the error output signal Ie is sent into the second closed-loop control loop to realize closed-loop control on the output current Io.

Wherein the LEDs in the above-mentioned LED backlight panel driving control circuit, LED lamp panel, LED lamp bead, etc. are all referred to as Mini LEDs.

Referring to fig. 5, further, the in-phase proportional amplifying circuit includes an operational amplifier U1A, the output current sampling Is connected to the in-phase input end of the operational amplifier U1A through a resistor R17, the inverting input end of the operational amplifier U1A Is grounded through a resistor R16, and a branch formed by connecting a resistor R15 and a capacitor C10 in parallel Is further disposed between the output end and the inverting input end of the operational amplifier U1A; the output end of the operational amplifier U1A is connected to the inverting input end of the operational amplifier U1B through a resistor R18.

Referring to fig. 2, further, the EMI filter and Boost PFC power factor correction circuit includes an EMI filter unit and a power factor correction unit; the EMI filtering unit comprises a common-mode inductor Lcm1, a common-mode inductor Lcm2, a capacitor CX1, a capacitor CX2, a capacitor CX3, a capacitor CY1, a capacitor CY2, a capacitor CY3 and a capacitor CY4; the power factor correction unit comprises a rectifier bridge BD1, a Boost circuit and a first control loop; the rectifier bridge BD1 is provided with a rectification positive electrode output end, a rectification negative electrode output end, a first alternating current input end and a second alternating current input end; the common-mode inductor Lcm1 and the common-mode inductor Lcm2 are both provided with two input ends and two output ends, the common-mode inductor Lcm1 and the common-mode inductor Lcm2 are connected in series, two input ends of the common-mode inductor Lcm1 are connected with an alternating current mains supply, the capacitor CX1 is connected between the two input ends of the common-mode inductor Lcm1 and is connected with a branch formed by connecting the capacitor CY1 and the capacitor CY2 in series, a node between the capacitor CY1 and the capacitor CY2 is grounded, the capacitor CX2 is connected between the two output ends of the common-mode inductor Lcm1 and is connected with a branch formed by connecting the capacitor CY3 and the capacitor CY4 in series, a node between the capacitor CY3 and the capacitor CY4 is grounded, the capacitor CX3 is connected between the two output ends of the common-mode inductor Lcm2 and is respectively connected to the first alternating current input end and the second alternating current input end, and the Boost circuit is connected between the rectification positive output end and the rectification negative output end; the mains supply is rectified by the rectifier bridge BD1 to obtain direct current, the direct current is subjected to closed-loop control by the Boost circuit to obtain stable output voltage VDC, and the output voltage VDC is output from the output end of the power factor correction unit; the Boost circuit comprises an inductor L1, a resistor R1, a diode D1, a capacitor C1, a switching tube Q1, a resistor R2 and a resistor R3; an inductor L1, a resistor R1, a diode D1, a resistor R2 and a resistor R3 are sequentially connected in series between the rectification anode output end and the rectification cathode output end of the rectifier bridge BD1, and the capacitor C1 is connected in parallel with a branch formed by connecting the resistor R2 and the resistor R3 in series; a switching tube Q1 is further arranged between the connecting node of the resistor R1 and the diode D1 and the output end of the rectification negative electrode, and the output voltage VDC is output from two ends of the capacitor C1; the first control loop comprises a main control chip NCP1654, the output voltage VDC is divided by a resistor R2 and a resistor R3 to form an output voltage sample and is input to the main control chip NCP1654, the input voltage sample is output to the main control chip NCP1654 at the rectifying positive electrode output end, and the input current sample is output to the main control chip NCP1654 at the connection node of the inductor L1 and the resistor R1; the main control chip NCP1654 is connected to the grid electrode of the switch tube Q1.

Referring to fig. 3, further, the half-bridge LLC resonant converter is provided with a VDC + input terminal and a VDC-input terminal; the VDC + input end and the VDC-input end are respectively connected to the output end of the power factor correction unit; the half-bridge LLC resonant converter comprises a transistor Q2, a transistor Q3, a capacitor C2, an inductor L2, a first transformer T1, a diode D2, a diode D3, a capacitor C3, a resistor R4, a resistor R5 and a second control loop; the first transformer T1 is provided with an input coil N1, an output coil N2 and an output coil N3, and the output coil N2 and the output coil N3 are arranged in series; the second control loop comprises a main control chip L6599A; the VDC-input end is grounded, a transistor Q2 and a transistor Q3 are arranged between the VDC + input end and the VDC-input end in series, the gates of the transistor Q2 and the transistor Q3 are connected to the output end of the second control loop, a capacitor C2, an inductor L2 and an input coil N1 are connected between the transistor Q2 and the transistor Q3 in series, one end of the output coil N2 is connected to one end of the capacitor C3 through a diode D2 and outputs a voltage Vo, the other end of the output coil N2 is connected to the other end of the capacitor C3 and grounded, the capacitor C3 and a branch formed by connecting the resistor R4 and the resistor R5 in series are arranged in parallel, one end of the output coil N3 is connected to the output coil N2, and the other end of the output coil N3 is connected to the negative electrode of the diode D2 through a diode D3; an output current sample Is between the resistor R4 and the resistor R5 Is input to the second control loop, and the output voltage sample Vo Is input to the second control loop.

Referring to fig. 4, further, the auxiliary source circuit includes a second transformer T2, and the second transformer T2 is provided with an input coil W1 and an output coil W2; the two ends of a branch formed by serially connecting the input coil W1 with a switching tube Q4 are connected to the output end of the EMI filtering and Boost PFC power factor correction circuit; one end of the output coil W2 is connected to the anode of a diode D4, a capacitor C5 is connected between the cathode of the diode D4 and the other end of the output coil W2, the other end of the output coil W2 is grounded, the diode D4 is connected in parallel with a branch circuit formed by serially connecting the capacitor C4 and a resistor R6, and the cathode of the diode D4 outputs a first auxiliary voltage.

Referring to fig. 4, further, in the auxiliary source circuit, the second transformer T2 is further provided with an output coil W3; one end of the output coil W3 is connected with the output coil W2 in series; the other end of the output coil W3 is connected to the anode of a diode D5, the cathode of the diode D5 is connected with one side of a capacitor C6, the other side of the capacitor C6 is grounded, the diode D5 is connected with a branch circuit formed by serially connecting a capacitor C7 and a resistor R9 in parallel, and the cathode of the diode D5 outputs a second auxiliary voltage.

Referring to fig. 5, further, the first auxiliary voltage is input to the second closed-loop control loop and the first closed-loop control loop; and the second auxiliary voltage is regulated by a chip XC6201 and then is input to the main control chip MCU.

Referring to fig. 5, further, the chip XC6201 is provided with a first pin, a second pin, and a third pin, the first pin inputs the second auxiliary voltage, the second pin is grounded, the second pin is connected to the first pin through a capacitor C11, the second pin is connected to the third pin through a capacitor C12, and the third pin is connected to the main control chip MCU.

According to a given hardware architecture diagram, the circuit works roughly as follows: in order to avoid interference of a Mini LED driving circuit, the 220V mains supply is subjected to noise reduction processing by using EMI filtering, then power factor correction is carried out by a Boost PFC circuit, and the mains supply can obtain a bus voltage VDC with the size of 400V after the EMI filtering and the power factor correction. One path of bus voltage is input to the LLC resonant circuit and used for obtaining a power supply current Io required by the Mini LED backlight plate; the other path of the bus voltage is input into the Mini LED backlight plate auxiliary power supply circuit to generate two paths of auxiliary voltages, so that stable 5V and 15V power supply voltages are provided for chips such as NCP1654, L6599A and the like and other circuits in the whole driving circuit, and the circuits can work normally. The output current generated by the LLC resonant circuit is used for supplying power to LED lamp beads in a Mini LED backlight board drive control circuit; the Mini LED backlight board driving control circuit accelerates the extinguishing speed of LED lamp beads through the series-parallel connection of a diode, a resistor and a capacitor, the power supply current of the Mini LED backlight board is quickly adjusted through a reference current signal Iref output by the MCU, and the circuit realizes the high dynamic dimming of LEDs through the two aspects.

Mini LED backlight board drive control circuit: in order to enable the dimming of the LED to be smoother, protect the LED from being burnt out due to abnormal current output by the resonant LLC and inhibit an input current peak in the switching process of the switching tube Q5, the Mini LED lamp bead is connected with the resistors R8 and C8 in parallel and is connected with the inductor L3 in series. In the moment when the display screen main control chip MCU outputs the PWM dimming signal to turn off the switch tube Q5, parasitic inductance and parasitic capacitance in the circuit can generate peak voltage to the drain electrode of the switch tube Q5 to reduce the service life of the switch tube Q5, and in order to solve the problem and accelerate the extinguishing speed of the LED lamp bead, RCD absorption units are connected in parallel on the LED lamp panel and used for absorbing redundant energy in the circuit. When switch tube Q5 disconnection, the energy of storing in inductance and the electric capacity can carry out the afterflow through diode D6, can consume with the mode of generating heat when energy passes through resistance R9, R10, R11 and R12 to accelerate the speed of extinguishing of LED lamp pearl, also can further improve the frequency of the PWM dimming signal of MCU output from this. The MCU of the central control chip collects the driving current Id flowing through the LED in the closing process of the switch tube Q5, and then the reference current Iref is set through the Id and the duty ratio of the PWM dimming signal. The output current sample Is connected to the non-inverting input terminal of the operational amplifier U1A through a resistor R17, and Is connected to the inverting input terminal of the operational amplifier U1B through a resistor R18 after being amplified by an amplifying circuit formed by resistors R15 and R16 at the inverting input terminal of the operational amplifier U1A. And then the difference value of the amplified output current and the reference current Iref is calculated by a PI controller formed by U1B, and finally an error output signal Ie calculated by the PI controller is sent to a closed-loop control loop 2, so that the closed-loop control of the output current Io is realized. This working process can be realized as follows: when the switching tube Q5 is closed, the resonant LLC circuit realizes constant current output under the control of the closed-loop control circuit 2 so as to light the LED; when the switch tube Q5 is switched off, the output of the approximate zero current is realized under the control of the closed-loop control loop 2 of the resonant LLC circuit, so that the circuit loss is reduced. The Mini LED backlight board driving control circuit realizes the function of closed-loop high dynamic adjustment of the Mini LED backlight board by the working mode.

The utility model provides a Mini LED drive circuit is shaded that closed loop high dynamic was adjusted luminance has following beneficial effect: 1) The Mini LED backlight driving circuit has the functions of EMI filtering and power factor correction, improves the power consumption quality, reduces the circuit loss and has higher anti-interference capability. 2) The backlight driving circuit adopts a closed-loop control mode, improves the state change speed of the LED and the dynamic regulation speed of the power supply current, and has a high dynamic regulation function.

The above embodiments of the present application are described in detail, and specific examples are applied in the present application to explain the principles and implementations of the present application, and the description of the above embodiments is only used to help understand the technical solutions and core ideas of the present application; those of ordinary skill in the art will understand that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications or substitutions do not depart from the spirit and scope of the present disclosure as defined by the appended claims.

Claims

1. A closed-loop high-dynamic dimming Mini LED backlight driving circuit is characterized by comprising an EMI filtering and Boost PFC power factor correction circuit, an auxiliary power circuit, a half-bridge LLC resonant converter and an LED backlight board driving control circuit; the input end of the EMI filtering and Boost PFC power factor correction circuit is connected to a mains supply, the output end of the EMI filtering and Boost PFC power factor correction circuit is connected to the auxiliary power circuit and the half-bridge LLC resonant converter, the auxiliary power circuit is located between the EMI filtering and Boost PFC power factor correction circuit and the half-bridge LLC resonant converter, and the LED backlight board drive control circuit is connected to the output end of the half-bridge LLC resonant converter; the LED backlight board driving control circuit comprises a second closed-loop control loop, the second closed-loop control loop is connected to the half-bridge LLC resonant converter, and the LED backlight board driving control circuit is connected to the second closed-loop control loop;

the second closed-loop control loop acquires an output current sample Is and an output voltage sample Vo of the half-bridge LLC resonant converter; an output current Io and an output current sampling Is of the half-bridge LLC resonant converter are input into the LED backlight board drive control circuit, and the LED backlight board drive control circuit outputs an error output signal Ie to the second closed-loop control loop to adjust the output current Io of the half-bridge LLC resonant converter;

the LED backlight board driving control circuit comprises an in-phase proportional amplification circuit, a PI controller, a main control chip MCU, a switch tube Q5 and an LED lamp board; the LED lamp panel is provided with an LED lamp bead, a branch formed by connecting the LED lamp bead with a resistor R8 and a capacitor C8 in parallel is connected with an inductor L3 in series to form a steady-flow light-emitting circuit, the output current Io of the half-bridge LLC resonant converter is input into the input end of the steady-flow light-emitting circuit, the steady-flow light-emitting circuit is connected with an RCD absorption unit in parallel and then is connected to the drain electrode of a switch tube Q5 through a resistor R13, the source electrode of the switch tube Q5 is grounded through a resistor R14, the main control chip MCU acquires the driving current Id at the position of the source electrode of the switch tube Q5, and the main control chip MCU outputs a dimming signal PWM to the grid electrode of the switch tube Q5; the PI controller comprises an operational amplifier U1B, and a capacitor C13 and a resistor R19 are connected in series between an inverting input end and an output end of the operational amplifier U1B; the main control chip MCU outputs a reference current Iref to a non-inverting input end of the operational amplifier U1B after processing the driving current Id and the duty ratio of the output PWM dimming signal; the output current sampling Is amplified by the in-phase proportional amplifying circuit and then Is connected to the inverting input end of the operational amplifier U1B through a resistor R18; and the difference value of the output current amplified by the in-phase proportional amplifying circuit and the reference current Iref is calculated by the PI controller to output an error output signal Ie, and the error output signal Ie is sent into the second closed-loop control loop to realize closed-loop control on the output current Io.

2. The closed-loop high dynamic dimming Mini LED backlight driving circuit according to claim 1, wherein the in-phase proportional amplifying circuit comprises an operational amplifier U1A, the output current sample Is connected to the non-inverting input terminal of the operational amplifier U1A through a resistor R17, the inverting input terminal of the operational amplifier U1A Is grounded through a resistor R16, and a branch formed by connecting a resistor R15 and a capacitor C10 in parallel Is further arranged between the output terminal and the inverting input terminal of the operational amplifier U1A; the output end of the operational amplifier U1A is connected to the inverting input end of the operational amplifier U1B through a resistor R18.

3. The closed-loop high dynamic dimming Mini LED backlight driving circuit according to claim 1, wherein the type of the MCU is EP2C8T144C8; the input voltage of the main control chip MCU is 3.3V.

4. The closed-loop high dynamic dimming Mini LED backlight driving circuit according to claim 1, wherein the EMI filtering and Boost PFC power factor correction circuit comprises an EMI filtering unit and a power factor correction unit;

the EMI filtering unit comprises a common-mode inductor Lcm1, a common-mode inductor Lcm2, a capacitor CX1, a capacitor CX2, a capacitor CX3, a capacitor CY1, a capacitor CY2, a capacitor CY3 and a capacitor CY4;

the power factor correction unit comprises a rectifier bridge BD1, a Boost circuit and a first control loop;

the rectifier bridge BD1 is provided with a rectification anode output end, a rectification cathode output end, a first alternating current input end and a second alternating current input end; the common-mode inductor Lcm1 and the common-mode inductor Lcm2 are both provided with two input ends and two output ends, the common-mode inductor Lcm1 and the common-mode inductor Lcm2 are connected in series, two input ends of the common-mode inductor Lcm1 are connected with an alternating current mains supply, the capacitor CX1 is connected between the two input ends of the common-mode inductor Lcm1 and is connected with a branch formed by connecting the capacitor CY1 and the capacitor CY2 in series, a node between the capacitor CY1 and the capacitor CY2 is grounded, the capacitor CX2 is connected between the two output ends of the common-mode inductor Lcm1 and is connected with a branch formed by connecting the capacitor CY3 and the capacitor CY4 in series, a node between the capacitor CY3 and the capacitor CY4 is grounded, the capacitor CX3 is connected between the two output ends of the common-mode inductor Lcm2 and is respectively connected to the first alternating current input end and the second alternating current input end, and the Boost circuit is connected between the rectification positive output end and the rectification negative output end;

the mains supply is rectified by the rectifier bridge BD1 to obtain direct current, the direct current is subjected to closed-loop control by the Boost circuit to obtain stable output voltage VDC, and the output voltage VDC is output from the output end of the power factor correction unit;

the Boost circuit comprises an inductor L1, a resistor R1, a diode D1, a capacitor C1, a switching tube Q1, a resistor R2 and a resistor R3; an inductor L1, a resistor R1, a diode D1, a resistor R2 and a resistor R3 are sequentially connected in series between the rectification anode output end and the rectification cathode output end of the rectifier bridge BD1, and the capacitor C1 is connected in parallel with a branch formed by connecting the resistor R2 and the resistor R3 in series; a switching tube Q1 is further arranged between the connecting node of the resistor R1 and the diode D1 and the output end of the rectification negative electrode, and the output voltage VDC is output from two ends of the capacitor C1;

the first control loop comprises a main control chip NCP1654, the output voltage VDC is divided by a resistor R2 and a resistor R3 to form an output voltage sample and is input to the main control chip NCP1654, the input voltage sample is output to the main control chip NCP1654 at the rectifying positive electrode output end, and the input current sample is output to the main control chip NCP1654 at the connection node of the inductor L1 and the resistor R1; the main control chip NCP1654 is connected to the grid electrode of the switch tube Q1.

5. The closed-loop high dynamic dimming Mini LED backlight driving circuit of claim 1,

the half-bridge LLC resonant converter is provided with a VDC + input end and a VDC-input end; the VDC + input end and the VDC-input end are respectively connected to the output end of the power factor correction unit;

the half-bridge LLC resonant converter comprises a transistor Q2, a transistor Q3, a capacitor C2, an inductor L2, a first transformer T1, a diode D2, a diode D3, a capacitor C3, a resistor R4, a resistor R5 and a second control loop; the first transformer T1 is provided with an input coil N1, an output coil N2 and an output coil N3, and the output coil N2 and the output coil N3 are arranged in series; the second control loop comprises a main control chip L6599A;

the VDC-input end is grounded, a transistor Q2 and a transistor Q3 are arranged between the VDC + input end and the VDC-input end in series, the gates of the transistor Q2 and the transistor Q3 are connected to the output end of the second control loop, a capacitor C2, an inductor L2 and an input coil N1 are connected between the transistor Q2 and the transistor Q3 in series, one end of the output coil N2 is connected to one end of the capacitor C3 through a diode D2 and outputs a voltage Vo, the other end of the output coil N2 is connected to the other end of the capacitor C3 and grounded, the capacitor C3 and a branch formed by connecting the resistor R4 and the resistor R5 in series are arranged in parallel, one end of the output coil N3 is connected to the output coil N2, and the other end of the output coil N3 is connected to the negative electrode of the diode D2 through a diode D3; an output current sample Is between the resistor R4 and the resistor R5 Is input to the second control loop, and the output voltage sample Vo Is input to the second control loop.

6. The closed-loop high dynamic dimming Mini LED backlight driver circuit of claim 1, wherein the closed-loop high dynamic dimming Mini LED backlight driver circuit further comprises an auxiliary source circuit; the auxiliary source circuit comprises a second transformer T2, and the second transformer T2 is provided with an input coil W1 and an output coil W2;

the two ends of a branch formed by serially connecting the input coil W1 with a switching tube Q4 are connected to the output end of the EMI filtering and Boost PFC power factor correction circuit;

one end of the output coil W2 is connected to the anode of a diode D4, a capacitor C5 is connected between the cathode of the diode D4 and the other end of the output coil W2, the other end of the output coil W2 is grounded, the diode D4 is connected in parallel with a branch circuit formed by serially connecting the capacitor C4 and a resistor R6, and the cathode of the diode D4 outputs a first auxiliary voltage.

7. The closed-loop high dynamic dimming Mini LED backlight driving circuit as claimed in claim 6, wherein in the auxiliary source circuit, the second transformer T2 is further provided with an output coil W3;

one end of the output coil W3 is connected with the output coil W2 in series;

the other end of the output coil W3 is connected to the anode of a diode D5, the cathode of the diode D5 is connected with one side of a capacitor C6, the other side of the capacitor C6 is grounded, the diode D5 is connected with a branch circuit formed by serially connecting a capacitor C7 and a resistor R9 in parallel, and the cathode of the diode D5 outputs a second auxiliary voltage.

8. The closed-loop high dynamic dimming Mini LED backlight driver circuit of claim 7,

the first auxiliary voltage is 15V; the second auxiliary voltage is 5V.

9. The closed-loop high dynamic dimming Mini LED backlight driver circuit of claim 8, wherein the first auxiliary voltage is input to the second and first closed-loop control loops; and the second auxiliary voltage is regulated by a chip XC6201 and then is input to the main control chip MCU.

10. The closed-loop high dynamic dimming Mini LED backlight driving circuit of claim 9, wherein the chip XC6201 has a first pin, a second pin and a third pin, the first pin inputs the second auxiliary voltage, the second pin is grounded, the second pin is connected to the first pin through a capacitor C11, the second pin is connected to the third pin through a capacitor C12, and the third pin is connected to the main control chip MCU.