Backlight power supply and display equipment

Abstract

The embodiment of the invention belongs to the power supply technology, and provides a backlight power supply and a display device, and the backlight power supply comprises an LLC backlight drive circuit, a mirror image circuit and a PFC boost circuit. Wherein the LLC backlight driving circuit is used for supplying power to a backlight source load and comprises an LLC resonance circuit, and the LLC resonance circuit comprises a resonance capacitor; the mirror image circuit is connected with the resonant capacitor in parallel, is also connected with the input end of the PFC booster circuit, and is used for mirroring a current signal flowing through the LLC resonant circuit, converting the current signal into a voltage signal and transmitting the voltage signal to the PFC booster circuit; and the output end of the PFC booster circuit is also connected with the input end of the LLC backlight driving circuit and is used for adjusting the voltage output to the LLC backlight driving circuit according to the voltage signal. According to the LLC backlight driving circuit, the mirror image circuit is introduced, so that the input voltage and the output voltage of the LLC backlight driving circuit synchronously change, and the backlight flicker phenomenon is avoided.

Description

Technical Field

[0001] The present application relates to power supply technology, and more specifically, to a backlight power supply and a display device. Background Art

[0002] Due to the advantages of Liquid Crystal Display (LCD), such as good display effect, small size, and low energy consumption, LCD televisions have been widely used.

[0003] Since LCD cannot emit light actively, LCD TVs usually need backlight power to light up. The power supply of LCD TVs in the prior art usually includes: EMC (Electromagnetic Compatibility) circuit, rectifier filter circuit, PFC (Power Factor Correction) boost circuit, LLC (resonant circuit) backlight drive circuit and other topological structures.

[0004] Based on the basic principle of the LLC backlight driving circuit, when the operating frequency of the LLC backlight driving circuit rises to a value close to the upper limit of the rated output frequency of the backlight driving chip, it is impossible to maintain the dynamic balance of the LLC backlight driving circuit output current through frequency changes, which can easily cause the backlight driving current to fluctuate and produce backlight flickering. Summary of the invention

[0005] The exemplary embodiments of the present application provide a backlight power supply and a display device to solve the problem in the prior art that when the operating frequency of the LLC backlight driving circuit rises to a value close to the upper limit of the rated output frequency of the backlight driving chip, it is easy to cause the backlight driving current to fluctuate and produce backlight flickering.

[0006] In a first aspect, an embodiment of the present application provides a backlight power supply, which is applied to a display device, and includes: an LLC backlight driving circuit, a mirror circuit, and a PFC boost circuit;

[0007] Wherein, the LLC backlight driving circuit is used to supply power to the backlight source load, and comprises an LLC resonant circuit, and the LLC resonant circuit comprises a resonant capacitor;

[0008] The mirror circuit is connected in parallel with the resonant capacitor and is also connected to the input end of the PFC boost circuit, for mirroring the current signal flowing through the LLC resonant circuit, converting the current signal into a voltage signal, and transmitting the voltage signal to the PFC boost circuit;

[0009] The output end of the PFC boost circuit is also connected to the input end of the LLC backlight driving circuit, and is used to adjust the voltage output to the LLC backlight driving circuit according to the voltage signal.

[0010] In a second aspect, an embodiment of the present application provides a display device, comprising a controller, a display screen, and a backlight power supply according to any one of the first aspects.

[0011] The present application provides a backlight power supply and a display device. Since the backlight power supply of the present application collects the current signal of the LLC resonant circuit through a mirror circuit, and converts the current signal of the LLC resonant circuit into a voltage signal, and transmits the voltage signal to the PFC boost circuit, so that the PFC boost circuit adjusts the output voltage of the PFC boost circuit according to the voltage signal, thereby realizing that the input voltage of the LLC backlight driving circuit changes with the voltage output by the LLC backlight driving circuit, and the gain of the LLC backlight driving circuit remains basically unchanged or changes slightly. Therefore, when the output voltage of the LLC backlight driving circuit changes due to brightness adjustment or other methods, the operating frequency of the LLC backlight driving circuit can be kept unchanged or changed to a small extent, so as to avoid the LLC backlight driving circuit running at an upper limit value close to the rated output frequency of the backlight driving chip, which is conducive to reducing the risks of EMC, temperature rise, etc., and improving reliability, it can also better maintain the dynamic balance of the output current of the LLC backlight driving circuit by controlling the change of the operating frequency of the LLC backlight driving circuit, avoid the fluctuation of the backlight driving current, and avoid the occurrence of backlight flickering. At the same time, since the operating frequency of the LLC backlight driving circuit changes little when the present application adjusts the brightness of the display device, the brightness adjustment range of the display device is effectively increased, thereby improving the user experience.

[0012] These and other aspects of the present application will become more apparent from the following description of the embodiment(s). BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the implementation methods in the embodiments of the present application or the related technologies, the following is a brief introduction to the drawings required for use in the embodiments or the related technology descriptions. Obviously, the drawings described below are some embodiments of the present application, and a person skilled in the art can also obtain other drawings based on these drawings.

[0014] Figure 1 An architectural diagram of a display device provided in an embodiment of the present application;

[0015] Figure 2 A configuration block diagram of a control device provided in an embodiment of the present application;

[0016] Figure 3 A schematic diagram of the structure of an LLC backlight driving circuit provided in an embodiment of the present application;

[0017] Figure 4 A schematic diagram of the structure of a backlight power supply provided in an embodiment of the present application Figure 1 ;

[0018] Figure 5 A schematic diagram of the structure of a backlight power supply provided in an embodiment of the present application Figure 2 ;

[0019] Figure 6 A schematic diagram of the structure of an operational amplifier circuit provided in an embodiment of the present application;

[0020] Figure 7 A schematic diagram of the structure of a backlight power supply provided in an embodiment of the present application Figure 3 ;

[0021] Figure 8 A schematic diagram of the structure of a backlight power supply provided in an embodiment of the present application Figure 4 ;

[0022] Fig. 9 A schematic diagram of the structure of a PFC boost circuit provided in an embodiment of the present application;

[0023] Fig.10 A feedback logic diagram of a PFC boost circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0024] In order to make the purpose, implementation mode and advantages of the present application clearer, the exemplary implementation mode of the present application will be clearly and completely described below in conjunction with the drawings in the exemplary embodiments of the present application. Obviously, the described exemplary embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0025] Based on the exemplary embodiments described in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the claims attached to this application. In addition, although the disclosure in this application is introduced according to one or several exemplary examples, it should be understood that each aspect of the disclosure can also constitute a complete implementation method separately.

[0026] It should be noted that the brief description of terms in this application is only for the convenience of understanding the embodiments described below, and is not intended to limit the embodiments of this application. Unless otherwise specified, these terms should be understood according to their common and usual meanings.

[0027] The terms "first", "second", "third", etc. in the specification and claims of this application and the above drawings are used to distinguish similar or similar objects or entities, and do not necessarily mean to limit a specific order or sequence, unless otherwise indicated. It should be understood that the terms used in this way can be interchangeable under appropriate circumstances, for example, they can be implemented according to orders other than those given in the diagrams or descriptions of the embodiments of this application.

[0028] In addition, the terms "include" and "have" and any variations thereof are intended to cover but not exclude inclusion, for example, a product or device comprising a list of components is not necessarily limited to those components expressly listed but may include other components not expressly listed or inherent to such products or devices.

[0029] The term "module" as used in this application refers to any known or later developed hardware, software, firmware, artificial intelligence, fuzzy logic, or combination of hardware and / or software code that is capable of performing the functions associated with that element.

[0030] Figure 1 This is a diagram of the architecture of a display device provided in an embodiment of the present application. Figure 1 The display device 100 includes at least one of a tuner 110, a communicator 120, a detector 130, an external device interface 140, a controller 150, a display 160, an audio output interface 170, a memory, a power supply, and a user interface.

[0031] In some embodiments, the controller includes a processor, a video processor, an audio processor, a graphics processor, a RAM, a ROM, and a first interface to an nth interface for input / output.

[0032] The display 160 includes a display screen component for presenting images, and a driving component for driving image display, a component for receiving image signals output from a controller, and a component for displaying video content, image content, and a menu control interface and a user control UI interface.

[0033] The display 160 may be a liquid crystal display.

[0034] The communicator 120 is a component for communicating with an external device or server according to various communication protocol types. For example, the communicator may include at least one of a Wifi module, a Bluetooth module, a wired Ethernet module, and other network communication protocol chips or near field communication protocol chips, and an infrared receiver. The display device 100 can establish transmission and reception of control signals and data signals with the external control device 200 or the server 400 through the communicator 120.

[0035] The user interface can be used to receive control signals from the control device 200 (such as an infrared remote controller, etc.).

[0036] The detector 130 is used to collect signals from the external environment or the external interaction. For example, the detector 130 includes a light receiver, a sensor for collecting the intensity of ambient light; or, the detector 130 includes an image collector, such as a camera, which can be used to collect external environment scenes, user attributes or user interaction gestures; or, the detector 130 includes a sound collector, such as a microphone, etc., for receiving external sounds.

[0037] The external device interface 140 may include, but is not limited to, any one or more of the following: a high-definition multimedia interface (HDMI), an analog or digital high-definition component input interface (component), a composite video input interface (CVBS), a USB input interface (USB), an RGB port, etc. It may also be a composite input / output interface formed by the above multiple interfaces.

[0038] The tuner-demodulator 110 receives broadcast television signals via wired or wireless reception, and demodulates audio and video signals, such as EPG data signals, from a plurality of wireless or wired broadcast television signals.

[0039] In some embodiments, the controller 150 and the tuner-demodulator 110 may be located in different separate devices, that is, the tuner-demodulator 110 may also be located in an external device of the main device where the controller 150 is located, such as an external set-top box.

[0040] The controller 150 controls the operation of the display device and responds to user operations through various software control programs stored in the memory. The controller 150 controls the overall operation of the display device 100. For example, in response to receiving a user command for selecting a UI object to be displayed on the display 160, the controller 150 can perform operations related to the object selected by the user command.

[0041] In some embodiments, the controller includes at least one of a central processing unit (CPU), a video processor, an audio processor, a graphics processing unit (GPU), a RAM Random Access Memory (RAM), a ROM (Read-Only Memory, ROM), a first interface to an nth interface for input / output, a communication bus (Bus), etc.

[0042] The user may input a user command through a graphical user interface (GUI) displayed on the display 160, and the user input interface receives the user input command through the graphical user interface (GUI). Alternatively, the user may input a user command through a specific sound or gesture, and the user input interface recognizes the sound or gesture through a sensor to receive the user input command.

[0043] "User interface" is the medium interface for interaction and information exchange between applications or operating systems and users. It realizes the conversion between the internal form of information and the form acceptable to users. The commonly used form of user interface is the Graphical User Interface (GUI), which refers to the user interface related to computer operation displayed in a graphical way. It can be an interface element such as an icon, window, control, etc. displayed on the display screen of an electronic device, where the control can include icons, buttons, menus, tabs, text boxes, dialog boxes, status bars, navigation bars, widgets, etc.

[0044] Figure 2 The following is an exemplary block diagram of a control device configuration. Figure 2 As shown, the control device 200 includes a controller 210, a communication interface 220, a user input / output interface 230, a memory 240, and a power supply 250. The control device 200 can receive an input operation instruction from a user, and convert the operation instruction into an instruction that can be recognized and responded to by the display device 100, playing the role of an intermediary when the user interacts with the display device 100.

[0045] The controller 210 includes a processor, RAM (Random Access Memory) and ROM (Read-Only Memory), which are used to control the operation and operation of the control device 200, as well as the communication and collaboration between internal components and external and internal data processing functions.

[0046] The communication interface 200 may include at least one of a WiFi chip, a Bluetooth module, and other on-site communication modules such as NFC. The user input / output interface 230 may include at least one of a microphone, a touch panel, a sensor, and a button.

[0047] The memory 240 is used to store various operating programs, data and applications for driving and controlling the control device 200 under the control of the controller 210, and can also store various control signal instructions input by the user.

[0048] The power supply 250 is used to provide operating power support for various components of the control device 200 under the control of the controller 210, and can be a battery and related control circuits.

[0049] For LCD TVs, since LCD cannot actively emit light, LCD TVs usually require a backlight power supply to light up. The backlight drive circuit can be used as a backlight power supply, and a typical application topology is the LLC direct drive backlight drive method. Figure 3 This is a schematic diagram of the structure of an LLC backlight driving circuit. Figure 3 As shown, Vin is the input voltage, and the MOS tube Q1 and the MOS tube Q2 are alternately turned on to change the current path, forming an alternating current in the capacitor Cr and the inductors Ls and Lp. The resonant capacitor Cr, the inductor Ls and the inductor Lp form an LLC resonant circuit. The LLC backlight drive circuit also includes a transformer T, a diode D1, a diode D2, a capacitor Cout and a backlight load R. Among them, the backlight load R can be an LED (light-emitting diode) lamp.

[0050] During normal operation, the output voltage regulation principle of the LLC backlight driving circuit is as follows: when the input voltage of the LLC backlight driving circuit or the backlight source load R changes, the operating frequency of the LLC backlight driving circuit is changed, so that the voltage division of the resonant capacitor Cr and the inductor Ls changes accordingly, and the voltage across the inductor Lp is maintained unchanged, so that the output voltage of the LLC backlight driving circuit is stable.

[0051] In the prior art, for the backlight cross-current drive scheme using LLC topology, when the TV adjusts the brightness, the output current of the LLC backlight drive circuit will change. Based on the characteristics of LED lamps, the current of the LED lamp or LED light strip increases or decreases, which will cause the voltage at both ends to increase or decrease. Based on the basic principles of LLC, changes in the output voltage of the LLC backlight drive circuit will cause a large range of changes in its operating frequency. Specifically, when the output voltage decreases, the frequency will increase accordingly. When the operating frequency of the LLC backlight drive circuit rises to a value close to the upper limit of the rated output frequency of the backlight driver chip, it is impossible to maintain the dynamic balance of the current through frequency changes, which can easily cause the backlight drive current to fluctuate and cause the backlight to flicker. Among them, the backlight drive current is the output current of the LLC backlight drive circuit.

[0052] On the other hand, when the operating frequency of the LLC backlight driver circuit is close to the upper limit of the rated output frequency of the backlight driver chip, the high switching frequency of the MOS tube will lead to risks such as EMC (Electromagnetic Compatibility) and temperature rise, and the reliability is low. At the same time, its operating frequency no longer changes, and the backlight output current is also adjusted to the lowest limit and cannot be adjusted further, resulting in a smaller dimming range and a poor user experience.

[0053] The embodiment of the present application provides a backlight power supply. When the display device adjusts the brightness, the change of the output voltage of the LLC backlight driving circuit will cause its operating frequency to change. As the operating frequency increases or decreases, the current of the LLC resonant circuit will also change accordingly. Therefore, the current of the LLC resonant circuit can be collected through a mirror circuit, and the current of the LLC resonant circuit is converted into a voltage, and the voltage is superimposed on the PFC boost circuit, so that the output voltage of the PFC boost circuit also changes accordingly, that is, the input voltage of the LLC backlight driving circuit changes accordingly, so that the input voltage of the LLC backlight driving circuit follows the voltage change output by the LLC backlight driving circuit. Therefore, when the output voltage of the LLC backlight driving circuit changes due to brightness adjustment or other methods, the operating frequency of the LLC backlight driving circuit can be kept unchanged or changed to a small extent, so as to avoid the LLC backlight driving circuit running at an upper limit value close to the rated output frequency of the backlight driving chip, which is conducive to reducing the risks of EMC, temperature rise, etc., and improving reliability. At the same time, it can also better maintain the dynamic balance of the output current of the LLC backlight driving circuit by controlling the operating frequency change of the LLC backlight driving circuit, avoid the fluctuation of the backlight driving current, and avoid the generation of the backlight flicker phenomenon.

[0054] At the same time, since the operating frequency of the LLC backlight driving circuit does not change or changes to a small extent, the operating frequency of the LLC backlight driving circuit can remain relatively stable, effectively increasing the brightness adjustment range of the display device and improving the user experience.

[0055] Figure 4 A schematic diagram of the structure of a backlight power supply provided in an embodiment of the present application Figure 1 The backlight power supply is applied to a display device, specifically, an LCD display device. Figure 4 As shown, the backlight power supply may include: an LLC backlight driving circuit 10, a mirror circuit 20 and a PFC boost circuit 30;

[0056] The LLC backlight driving circuit 10 is used to supply power to the backlight source load R, and includes an LLC resonant circuit 101, wherein the LLC resonant circuit 101 includes a resonant capacitor Cr;

[0057] The mirror circuit 20 is connected in parallel with the resonant capacitor Cr and is also connected to the input end of the PFC boost circuit 30, and is used to mirror the current signal flowing through the LLC resonant circuit 101, and convert the current signal into a voltage signal, and transmit the voltage signal to the PFC boost circuit 30;

[0058] The output end of the PFC boost circuit 30 is also connected to the input end of the LLC backlight driving circuit 10 for adjusting the voltage output to the LLC backlight driving circuit 10 according to the voltage signal.

[0059] The structure of LLC backlight driving circuit 10 can be referred to Figure 3 As shown, it can be known from the output voltage regulation principle of the LLC backlight driving circuit 10 that when the operating frequency of the LLC backlight driving circuit 10 changes, the primary current of the LLC backlight driving circuit 10 will also change accordingly. The primary current of the LLC backlight driving circuit 10 is the current of the LLC resonant circuit 101, specifically, the current flowing through the resonant capacitor Cr.

[0060] In one implementation scenario, the RC current mirror technology can be used to collect the current signal flowing through the resonant capacitor Cr. The RC current mirror technology is to connect a mirror capacitor in parallel with the resonant capacitor Cr to mirror the current signal flowing through the resonant capacitor Cr, and convert the mirrored current signal into a voltage signal through a mirror resistor.

[0061] The size of the mirror capacitor and the capacitance value and the resistance value of the mirror resistor can be determined according to actual conditions. The size of the current signal flowing through the mirror capacitor and the current signal flowing through the resonant capacitor Cr is related to the capacitance value of the mirror capacitor and the resonant capacitor Cr.

[0062] The PFC boost circuit 30 can adjust the output voltage of the PFC boost circuit 30 according to the voltage signal. The output voltage of the PFC boost circuit 30 is the input voltage Vin of the LLC backlight driving circuit 10. Figure 4 In the figure, the output voltage of the PFC boost circuit 30 is also represented by Vin to indicate the connection relationship between the output end of the PFC boost circuit 30 and the input end of the LLC backlight driving circuit 10.

[0063] In one implementation scenario, when the brightness of the display device is increased, the controller can control the current flowing through the LED lamp to increase. Based on the characteristics of the LED, the voltage across the LED lamp also increases, that is, the output voltage of the LLC backlight driving circuit 10 increases, and therefore, the current signal flowing through the LLC resonant circuit 101, that is, the resonant capacitor Cr, increases. The current signal is collected by the mirror circuit 20 and converted into a corresponding voltage signal. The PFC boost circuit 30 controls the voltage output of the PFC boost circuit 30 to increase according to the voltage signal, that is, the input voltage of the LLC backlight driving circuit 10 increases, so that the gain of the LLC backlight driving circuit 10 remains basically unchanged or changes slightly, and the controller does not need to adjust or significantly adjust the operating frequency of the LLC backlight driving circuit 10, so that the operating frequency of the LLC backlight driving circuit 10 can be maintained relatively stable. Among them, the controller can be a backlight driving chip.

[0064] In another implementation scenario, if the brightness of the display device is lowered, the controller can control the current flowing through the LED lamp to decrease, so the voltage across the LED lamp is also reduced, that is, the output voltage of the LLC backlight driving circuit 10 is reduced. Correspondingly, the current signal flowing through the resonant capacitor Cr is also reduced. The current signal is collected by the mirror circuit 20 and converted into a corresponding voltage signal. The PFC boost circuit 30 controls the voltage output of the PFC boost circuit 30 to decrease according to the voltage signal, that is, the input voltage of the LLC backlight driving circuit 10 is reduced, so that the input voltage of the LLC backlight driving circuit 10 changes synchronously with the output voltage of the LLC backlight driving circuit 10, and the gain of the LLC backlight driving circuit 10 remains basically unchanged or changes slightly. The controller does not need to adjust or significantly adjust the operating frequency of the LLC backlight driving circuit 10, so the operating frequency of the LLC backlight driving circuit 10 can be maintained relatively stable.

[0065] The embodiment of the present application provides a backlight power supply, which introduces a mirror circuit 20 to mirror a current signal flowing through a resonant capacitor Cr, and converts the current signal into a voltage signal, so that a PFC boost circuit 30 adjusts the output voltage of the PFC boost circuit 30 according to the voltage signal, that is, adjusts the input voltage of the LLC backlight driving circuit 10, thereby realizing that the input voltage of the LLC backlight driving circuit 10 and the output voltage of the LLC backlight driving circuit 10 change synchronously, and the gain of the LLC backlight driving circuit 10 remains basically unchanged or changes slightly. At this time, the controller does not need to adjust or significantly adjust the operating frequency of the LLC backlight driving circuit 10, so that the LLC backlight driving circuit 10 can be prevented from running at an upper limit value close to the rated output power of the backlight driving chip, reducing the risks of EMC, temperature rise, etc., and improving reliability. At the same time, it can also better maintain the dynamic balance of the output current of the LLC backlight driving circuit 10 by controlling the change of the operating frequency of the LLC backlight driving circuit 10, avoiding fluctuations in the backlight driving current and avoiding the occurrence of backlight flickering. Since the operating frequency of the LLC backlight driving circuit 10 changes slightly when the brightness of the display device is adjusted in the present application, the brightness adjustment range of the display device is effectively increased, thereby improving the user experience.

[0066] Figure 5 A schematic diagram of the structure of a backlight power supply provided in an embodiment of the present application Figure 2 In one or more embodiments of the present application, Figure 5 As shown, the mirror circuit 20 includes: a mirror capacitor Csns and a mirror resistor Rsns;

[0067] The mirror capacitor Csns is connected in series with the mirror resistor Rsns, and then connected in parallel with the resonant capacitor Cr;

[0068] The mirror capacitor Csns is used to mirror the current signal flowing through the resonant capacitor Cr, and the mirror resistor Rsns is used to convert the current signal into a voltage signal.

[0069] Since the mirror capacitor Csns and the resonant capacitor Cr are connected in parallel, the current flowing through the mirror capacitor Csns and the current flowing through the resonant capacitor Cr have the same phase. However, due to the difference in capacitance between the mirror capacitor Csns and the resonant capacitor Cr, the current flowing through the mirror capacitor Csns and the current flowing through the resonant capacitor Cr have different amplitudes, that is, different current sizes.

[0070] In an implementation scenario, the capacitance of the mirror capacitor Csns is smaller than the capacitance of the resonant capacitor Cr, and the capacitance of the mirror capacitor Csns is proportional to the capacitance of the resonant capacitor Cr.

[0071] For example, if the capacitance of the resonant capacitor Cr is 22nF and the capacitance of the mirror capacitor Csns is 220pF, the ratio of the resonant capacitor Cr to the mirror capacitor Csns is 100:1, so the current flowing through the mirror capacitor Csns is approximately 1% of the current flowing through the resonant capacitor Cr.

[0072] In another implementation scenario, if the capacitance of the mirror capacitor Csns is large, the current flowing through the line where the mirror capacitor Csns is located is large, that is, the loss of the mirror capacitor Csns and the mirror resistor Rsns will also be relatively large. In this application, the mirror capacitor Csns is used to mirror the current signal flowing through the resonant capacitor Cr, and there is no need to mirror a stronger current signal. Therefore, in order to reduce the loss, a capacitor with a smaller capacitance can be selected as the mirror capacitor Csns.

[0073] In one implementation scenario, the resistance of the mirror resistor Rsns does not need to be large, and a resistor with a smaller resistance can be selected as the mirror resistor Rsns, which can convert the mirrored current signal into a voltage signal.

[0074] In summary, based on the RC current mirror technology, that is, using the mirror capacitor Csns to mirror the current signal flowing through the resonant capacitor Cr, and using the mirror resistor Rsns to convert the current signal into a voltage signal, so as to transmit the voltage signal to the PFC boost circuit 30, fewer devices are used, and a capacitor with a smaller capacitance can be used as the mirror capacitor Csns, and a resistor with a smaller resistance can be used as the mirror resistor Rsns, which is beneficial to reducing power consumption.

[0075] Figure 6 A schematic diagram of the structure of an operational amplifier circuit provided in an embodiment of the present application, referring to Figure 6 As shown, in one or more embodiments of the present application, the backlight power supply further includes: an operational amplifier circuit 40;

[0076] One end of the operational amplifier circuit 40 is connected between the mirror capacitor Csns and the mirror resistor Rsns, and the other end is connected to the PFC boost circuit 30, for amplifying the voltage signal between the mirror capacitor Csns and the mirror resistor Rsns, and transmitting the processed voltage signal to the PFC boost circuit 30.

[0077] In one implementation scenario, when the degree of change of the current signal flowing through the resonant capacitor Cr is small, it can be seen from the above embodiment that since the capacitance of the mirror capacitor Csns is smaller than the capacitance of the resonant capacitor Cr, the degree of change of the current signal flowing through the mirror capacitor Csns and the mirror resistor Rsns is smaller than the degree of change of the current signal flowing through the resonant capacitor Cr, and the degree of change of the voltage signal obtained through the mirror resistor Rsns is also smaller. Therefore, in order to improve the PFC boost circuit 30 to adjust the output voltage more accurately, an operational amplifier circuit 40 can be added between the mirror circuit 20 and the PFC boost circuit 30 to amplify the voltage signal between the mirror capacitor Csns and the mirror resistor Rsns, and the degree of change of the voltage signal will also be amplified accordingly.

[0078] In some embodiments, the operational amplifier circuit 40 may include: a first resistor R1, a second resistor R2, and a proportional amplifier circuit 401;

[0079] One end of the first resistor R1 is connected between the mirror capacitor Csns and the mirror resistor Rsns, and the other end is connected to one end of the second resistor R2. The other end of the second resistor R2 is grounded. The first resistor R1 and the second resistor R2 are used for voltage division.

[0080] One end of the in-phase proportional amplifier circuit 401 is connected between the first resistor R1 and the second resistor R2, and the other end is connected to the input end of the PFC boost circuit 30, for amplifying the voltage signal Vs between the first resistor R1 and the second resistor R2, and transmitting the processed voltage signal to the PFC boost circuit 30.

[0081] In one implementation scenario, the first resistor R1 and the second resistor R2 are used for voltage division to avoid a large voltage signal Vs between the first resistor R1 and the second resistor R2, which increases circuit loss and is also beneficial to improving circuit safety.

[0082] It should be noted that the operational amplifier circuit 40 may further include a plurality of resistors for voltage division, which are connected in series with the first resistor R1 and the second resistor R2 . The present application does not limit the number of the voltage division resistors.

[0083] The in-phase proportional amplifier circuit 401 amplifies the voltage signal Vs between the first resistor R1 and the second resistor R2, and the phase of the voltage signal before and after the amplification remains consistent.

[0084] In some embodiments, the in-phase proportional amplifier circuit 401 includes: a third resistor R3, a fourth resistor R4, a fifth resistor R5 and an operational amplifier U;

[0085] One end of the third resistor R3 is connected between the first resistor R1 and the second resistor R2, and the other end is connected to the positive input terminal of the operational amplifier U to transmit the voltage signal Vs between the first resistor R1 and the second resistor R2 to the positive input terminal of the operational amplifier U;

[0086] The output end of the operational amplifier U is connected to the input end of the PFC boost circuit 30 to output the processed voltage signal to the PFC boost circuit 30;

[0087] One end of the fourth resistor R4 is connected to the output end of the operational amplifier U, and the other end is connected to one end of the fifth resistor R5, and the other end of the fifth resistor R5 is grounded;

[0088] The negative input terminal of the operational amplifier U is connected between the third resistor R3 and the fourth resistor R4 to feed back the processed voltage signal Vfb outputted from the output terminal of the operational amplifier U to the negative input terminal;

[0089] The positive power input terminal of the operational amplifier U is connected to the positive electrode of the external power supply, and the negative power input terminal is connected to the negative electrode of the external power supply.

[0090] In one implementation scenario, the positive power input terminal of the operational amplifier U is connected to the positive electrode of the external power supply, and the negative power input terminal is connected to the negative electrode of the external power supply, so as to receive the voltage Vcc provided by the external power supply.

[0091] In one implementation scenario, the voltage signal Vs between the first resistor R1 and the second resistor R2 is input to the positive input terminal of the operational amplifier U through the third resistor R3. The operational amplifier U amplifies the received voltage signal, and the voltage signal Vfb outputted from the output terminal of the operational amplifier U is the processed voltage signal.

[0092] The voltage signal Vfb outputted from the output terminal of the operational amplifier U can be outputted to the PFC boost circuit 30, and can also be fed back to the negative input terminal of the operational amplifier U through the fourth resistor R4 and the fifth resistor R5. In one implementation scenario, the resistance value of the third resistor R3 can be the ratio of the resistance value of the fourth resistor R4 to the resistance value of the fifth resistor R5.

[0093] In some embodiments, the voltage signal Vs between the first resistor R1 and the second resistor R2 is in a certain ratio to the processed voltage signal Vfb output from the output end of the operational amplifier U, which is the ratio of the resistance value of the fourth resistor R4 to the resistance value of the fifth resistor R5 and 1.

[0094] The processed voltage signal, i.e., the voltage signal Vfb outputted from the output terminal of the operational amplifier U, and the voltage signal Vs between the first resistor R1 and the second resistor R2 may follow the following relationship:

[0095] Vfb=(1+R4 / R5)Vs

[0096] Wherein, R4 is the resistance value of the fourth resistor R4, and R5 is the resistance value of the fifth resistor R5.

[0097] It can be seen from the above formula that the in-phase proportional amplifier circuit 401 can realize in-phase proportional operation, that is, the input voltage and the output voltage of the in-phase proportional amplifier circuit 401 are in a certain ratio and have the same phase.

[0098] In summary, the voltage signal Vs between the first resistor R1 and the second resistor R2 is amplified by the operational amplifier circuit 40, and the variation of the voltage signal is further amplified, so that when the variation of the current signal of the LLC resonant circuit 101 is small, the PFC boost circuit 30 can also accurately control its output voltage, which is beneficial to improving the sensitivity and accuracy of the PFC boost circuit 30 in controlling its output voltage.

[0099] Figure 7 A schematic diagram of the structure of a backlight power supply provided in an embodiment of the present application Figure 3 ,like Figure 7 As shown, in some embodiments, the backlight power supply also includes: an electromagnetic compatibility filter circuit 50 and a rectifier filter circuit 60; one end of the electromagnetic compatibility filter circuit 50 is used to receive AC power, and the other end is connected to one end of the rectifier filter circuit 60, and the other end of the rectifier filter circuit 60 is connected to the PFC circuit.

[0100] The specific working process of the backlight power supply is as follows: the mains power is boosted to a preset voltage value by the PFC boost circuit 30 after passing through the electromagnetic compatibility filter circuit 50 and the rectifier filter circuit 60, and is output to the LLC backlight drive circuit 10 as the energy source of LLC resonance. The LLC backlight drive circuit 10 supplies power to the backlight source load R.

[0101] Figure 8 A schematic diagram of the structure of a backlight power supply provided in an embodiment of the present application Figure 4 ,like Figure 8 As shown, in some embodiments, the PFC boost circuit 30 includes: a PFC circuit 301, an output voltage feedback circuit 302 and a drive control circuit 303;

[0102] The input end of the output voltage feedback circuit 302 is respectively connected to the output end of the PFC circuit 301 and the output end of the operational amplifier U, and the output end is connected to the input end of the drive control circuit 303, and is used to collect the voltage signal output by the PFC circuit 301 and the voltage signal Vfb output by the operational amplifier U, and output the voltage signal output by the PFC circuit 301 and the voltage signal Vfb output by the operational amplifier U to the drive control circuit 303;

[0103] The output end of the drive control circuit 303 is connected to the input end of the PFC circuit 301 to adjust the voltage output by the PFC circuit 301 according to the voltage signal output by the PFC circuit 301 and the voltage signal Vfb output by the operational amplifier U.

[0104] Fig. 9 A schematic diagram of the structure of a PFC boost circuit provided in an embodiment of the present application. Fig. 9 As shown, the PFC circuit 301 includes an inductor L PFC , MOS tube Qp, diode D and capacitor Cbus, together with output voltage feedback circuit 302 and drive control circuit 303 form a PFC boost circuit 30. Fig. 9 Also shown is a rectifying and filtering circuit 60 which may include a diode D1 , a diode D2 , a diode D3 , and a diode D4 .

[0105] In some embodiments, the PFC circuit 301 may be a boost topology, and its output voltage is related to the input voltage and the duty cycle of the MOS tube. The control objectives of the PFC circuit 301 include constant output voltage and power factor correction, that is, achieving voltage and current in phase.

[0106] refer to Fig. 9 As shown, the voltages at the two output terminals of the PFC circuit 301 are VBUS+ and VBUS-, respectively, and the voltage difference between the two is the input voltage Vin of the LLC backlight driving circuit. The output voltage of the PFC circuit 301 relies on the output voltage feedback circuit 302 to collect voltage changes in real time, and feeds the collected signal back to the drive control circuit 303, compares it with the reference voltage signal in the drive control circuit 303, and then controls the PWM generator to adjust the width of the output pulse signal to keep the output voltage of the PFC circuit 301 stable. The output voltage value of the PFC circuit 301 can be set by changing the parameters of the output voltage feedback circuit 302. The feedback logic diagram of the PFC boost circuit can be referred to Fig.10 shown.

[0107] Combination Fig. 9 and Fig.10As shown, the feedback logic of the drive control circuit 303 is as follows: the drive control circuit 303 can collect the input voltage Vi, the output voltage Vout of the PFC circuit 301, and the inductance L in the PFC circuit 301 PEC The drive control circuit 303 filters the output voltage Vout based on the reference voltage signal Vref to obtain a DC voltage Gcv. After the DC voltage Gcv is multiplied by the input voltage Vi, the obtained signal can be represented by kVi, where k is the voltage feedback signal. The obtained signal is converted into a current signal Iref. The inductor L is filtered by a low-pass filter LPF. PEC The current i is processed to obtain the current iLF. The current iLF and the current signal Iref are superimposed to obtain the current signal Gci. Then, the current signal Gci is overlapped with the triangular wave generated by the reference triangular wave generator, and the on-off of the MOS tube Qp is controlled based on the overlapping result, and the output voltage Vout of the PFC boost circuit 30 is further controlled to realize power factor correction while realizing constant voltage control.

[0108] It should be noted that the above output voltage Vout includes not only the voltage output by the PFC circuit 301 , but also the voltage output by the operational amplifier U. The voltage output by the operational amplifier U is the voltage value obtained according to the current of the LLC resonant circuit 101 .

[0109] It should also be noted that the output voltage of the PFC circuit 301 has a certain range requirement, so in this application, the voltage output by the adjusted PFC circuit 301 cannot be too high or too low. Normally, the voltage output by the PFC circuit 301 cannot be lower than the voltage output by the rectifier filter circuit 60 to avoid failure of the PFC boost circuit 30. The voltage output by the PFC circuit 301 cannot be higher than the rated voltage value that the components included in the PFC boost circuit 30 and the LLC backlight drive circuit 10 can withstand to avoid damage to the PFC boost circuit 30 and the LLC backlight drive circuit 10.

[0110] In summary, the drive control circuit 303 can adjust the output voltage of the PFC voltage according to the voltage output by the PFC circuit 301 and the voltage obtained according to the current of the LLC resonant circuit 101. Since the output voltage of the PFC voltage is the input voltage of the LLC backlight driving circuit 10, the input voltage of the LLC backlight driving circuit 10 can be changed along with the output voltage of the LLC backlight driving circuit 10, so that the operating frequency of the LLC backlight driving circuit 10 does not change or changes to a small extent, which is conducive to maintaining the relative stability of the operating frequency of the LLC backlight driving circuit 10 and further avoiding the occurrence of backlight flickering.

[0111] The embodiment of the present application provides a display device, including a controller, a display screen and a backlight power supply provided in the above embodiment. The specific working principle of the backlight power supply can be referred to the above embodiment, and the present application will not repeat it here.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

[0113] For ease of explanation, the above description has been made in conjunction with specific embodiments. However, the above exemplary discussion is not intended to be exhaustive or limit the embodiments to the specific forms disclosed above. Based on the above teachings, various modifications and variations can be obtained. The selection and description of the above embodiments are intended to better explain the principles and practical applications, so that those skilled in the art can better use the embodiments and various different variations of the embodiments suitable for specific use considerations.

Claims

1. A backlight power supply, characterized in that: Applied to display devices, including: LLC backlight drive circuit, mirror circuit and PFC boost circuit; Wherein, the LLC backlight driving circuit is used to supply power to the backlight source load, and comprises an LLC resonant circuit, and the LLC resonant circuit comprises a resonant capacitor; The mirror circuit is connected in parallel with the resonant capacitor and is also connected to the input end of the PFC boost circuit, and is used to mirror the current signal flowing through the LLC resonant circuit, convert the current signal into a voltage signal, and transmit the voltage signal to the PFC boost circuit; The output end of the PFC boost circuit is also connected to the input end of the LLC backlight driving circuit, and is used to adjust the voltage output to the LLC backlight driving circuit according to the voltage signal.

2. The backlight power supply according to claim 1, characterized in that: The mirror circuit comprises: a mirror capacitor and a mirror resistor; The mirror capacitor is connected in series with the mirror resistor, and then connected in parallel with the resonant capacitor. The mirror capacitor is used to mirror the current signal flowing through the resonant capacitor, and the mirror resistor is used to convert the current signal into a voltage signal.

3. The backlight power supply according to claim 2, characterized in that: The capacitance of the mirror capacitor is smaller than the capacitance of the resonant capacitor, and the capacitance of the mirror capacitor is proportional to the capacitance of the resonant capacitor.

4. The backlight power supply according to claim 2 or 3, characterized in that: Also includes: Operational amplifier circuit; One end of the operational amplifier circuit is connected between the mirror capacitor and the mirror resistor, and the other end is connected to the PFC boost circuit, for amplifying the voltage signal between the mirror capacitor and the mirror resistor, and transmitting the processed voltage signal to the PFC boost circuit.

5. The backlight power supply according to claim 4, characterized in that: The operational amplifier circuit comprises: a first resistor, a second resistor and a same-direction proportional amplifier circuit; One end of the first resistor is connected between the mirror capacitor and the mirror resistor, and the other end is connected to one end of the second resistor. The other end of the second resistor is grounded. The first resistor and the second resistor are used for voltage division. One end of the in-phase proportional amplifier circuit is connected between the first resistor and the second resistor, and the other end is connected to the input end of the PFC boost circuit, for amplifying the voltage signal between the first resistor and the second resistor, and transmitting the processed voltage signal to the PFC boost circuit.

6. The backlight power supply according to claim 5, characterized in that: The same direction proportional amplification circuit comprises: a third resistor, a fourth resistor, a fifth resistor and an operational amplifier; One end of the third resistor is connected between the first resistor and the second resistor, and the other end is connected to the positive input terminal of the operational amplifier to transmit the voltage signal between the first resistor and the second resistor to the positive input terminal of the operational amplifier; The output end of the operational amplifier is connected to the input end of the PFC boost circuit to output the processed voltage signal to the PFC boost circuit; One end of the fourth resistor is connected to the output end of the operational amplifier, and the other end is connected to one end of the fifth resistor, and the other end of the fifth resistor is grounded; The negative input terminal of the operational amplifier is connected between the third resistor and the fourth resistor to feed back the processed voltage signal outputted from the output terminal of the operational amplifier to the negative input terminal; The positive power input terminal of the operational amplifier is connected to the positive electrode of the external power supply, and the negative power input terminal is connected to the negative electrode of the external power supply.

7. The backlight power supply according to claim 6, characterized in that: The voltage signal between the first resistor and the second resistor is in a certain proportion to the processed voltage signal output from the output end of the operational amplifier, and the proportion is the sum of the ratio of the resistance value of the fourth resistor to the resistance value of the fifth resistor and 1.

8. The backlight power supply according to claim 6, characterized in that: The PFC boost circuit comprises: a PFC circuit, an output voltage feedback circuit and a drive control circuit; The input end of the output voltage feedback circuit is respectively connected to the output end of the PFC circuit and the output end of the operational amplifier, and the output end is connected to the input end of the drive control circuit, and is used to collect the voltage signal output by the PFC circuit and the voltage signal output by the operational amplifier, and output the voltage signal output by the PFC circuit and the voltage signal output by the operational amplifier to the drive control circuit; The output end of the drive control circuit is connected to the input end of the PFC circuit to adjust the voltage output by the PFC circuit according to the voltage signal output by the PFC circuit and the voltage signal output by the operational amplifier.

9. The backlight power supply according to claim 8, characterized in that: Also includes: Electromagnetic compatibility filter circuit and rectifier filter circuit; One end of the electromagnetic compatibility filter circuit is used to receive the mains power, and the other end is connected to one end of the rectifier and filter circuit, and the other end of the rectifier and filter circuit is connected to the PFC circuit.

10. A display device, characterized in that: The invention comprises a controller, a display screen and a backlight power supply according to any one of claims 1 to 9.

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