Start control circuit, chip and display device of LED backlight driving

Abstract

The application is suitable for the technical field of LED backlight driving, and provides a starting control circuit, a chip and a display device for LED backlight driving. The starting control circuit for LED backlight driving comprises a detection selection module, an error amplification module, a first switching switch module, a control module, a second switching switch module, a logic drive module, a feedback module and a first switch module. When each first voltage is within a preset range, the first switching switch module is used for turning on the first input end of the error amplification module and the output end of the error amplification module. The second switching switch module is used for transmitting an overcurrent protection signal to the logic drive module. When the detection voltage is greater than the first reference voltage, the first switching switch module is used for turning on the first input end of the error amplifier and the detection selection module. The second switching switch module is used for turning on the control module and the logic drive module. Thus, the Boost has more response time to respond to the rapid change of the LED.

Description

Technical Field

[0001] The present application belongs to the field of LED backlight driving technology, and in particular relates to a startup control circuit, chip and display device for LED backlight driving. Background Art

[0002] LEDs (Light-Emitting Diodes), with their high brightness, low power consumption, and long life, have become a core component in LCD (Liquid Crystal Display) backlight systems. The startup control performance of their driver circuits directly impacts system safety and stability. Traditional LED backlight driver startup schemes typically feed the minimum LED headroom voltage (i.e., channels CH1-CH6) into the input of a boost circuit's error amplifier, which then regulates the boost's output voltage. However, this design results in a slow build-up of the boost's output voltage, preventing it from responding quickly to rapid changes in the LED string's current. Summary of the Invention

[0003] The embodiments of the present application provide a startup control circuit, chip and display device for an LED backlight driver, which can solve the problem that the traditional LED backlight driver startup solution cannot respond in time when the current of the LED light string changes rapidly.

[0004] In a first aspect, an embodiment of the present application provides a startup control circuit for an LED backlight driver, comprising a detection and selection module, an error amplification module, a first switching switch module, a control module, a second switching switch module, a logic drive module, a first switch module, and a feedback module, wherein the first switching switch module is electrically connected to the detection and selection module and the error amplification module, respectively; the control module is electrically connected to the error amplification module, the second switching switch module, and the first switch module, respectively; and the logic drive module is electrically connected to the second switching switch module, the first switch module, and the feedback module, respectively;

[0005] The detection selection module is configured to output a detection voltage to the first switching module based on a plurality of first voltages, wherein the first voltage is the voltage at the output end of the LED light string, and the detection voltage is the minimum voltage among the plurality of first voltages; when each of the first voltages is within a preset range, the first switching module is configured to conduct the first input end and the output end of the error amplification module based on a first switching control signal; the error amplification module is configured to output a reference voltage based on a first reference voltage received at a second input end of the error amplification module; and the second switching module is configured to transmit an overcurrent protection signal to the logic driver module based on a second switching control signal;

[0006] When the detection voltage is greater than the first reference voltage, the first switching switch module is used to connect the first input end of the error amplification module and the detection selection module according to a third switching control signal; the error amplification module is used to output a reference voltage according to the detection voltage and the first reference voltage; the second switching switch module is used to connect the control module and the logic drive module according to a fourth switching control signal.

[0007] In a possible implementation of the first aspect, the startup control circuit of the LED backlight driver further includes a current detection module and a third switch module, wherein the current detection module is electrically connected to the feedback module, the detection selection module, and the third switch module, respectively, and the third switch module is electrically connected to the second input end of the error amplification module;

[0008] The current detection module is used to obtain the current flowing through the LED light string based on the output voltage and the first voltage, and when the current flowing through the LED light string reaches the target current, the current detection module is used to output a detection signal to the third switching switch module; the third switching switch module is used to transmit the steady-state reference voltage to the second input end of the error amplification module according to the detection signal.

[0009] In a possible implementation manner of the first aspect, the first reference voltage is greater than the steady-state reference voltage.

[0010] In a possible implementation of the first aspect, the error amplification module includes an error amplifier, a first input end of the error amplifier is electrically connected to the first switching switch module, a second input end of the error amplifier is used to receive the first reference voltage, and an output end of the error amplifier is electrically connected to the control module and the first switching switch module, respectively.

[0011] In a possible implementation of the first aspect, the first switching module includes a first transmission gate, a first end of the first transmission gate is electrically connected to the first input end of the error amplification module, a second end of the first transmission gate is electrically connected to the detection selection module, a third end of the first transmission gate is electrically connected to the output end of the error amplification module, and a control end of the first transmission gate is used to receive the first switching control signal and the third switching control signal;

[0012] The second switching switch module includes a second transmission gate, a first end of the second transmission gate is electrically connected to the control module, a second end of the second transmission gate is used to receive the overcurrent protection signal, a third end of the second transmission gate is electrically connected to the logic drive module, and a control end of the second transmission gate is used to receive the second switching control signal and the fourth switching control signal.

[0013] In a possible implementation of the first aspect, the logic drive module includes an OR gate and a first trigger, the first input end of the OR gate is electrically connected to the second switching switch module, the second input end of the OR gate is electrically connected to the feedback module, the output end of the OR gate is electrically connected to the first input end of the first trigger, the second input end of the first trigger is used to receive an oscillation signal, and the output end of the first trigger is electrically connected to the first switch module.

[0014] In a possible implementation of the first aspect, the startup control circuit of the LED backlight driver further includes a comparison module, and the comparison module is electrically connected to the error amplification module and the first switch module respectively;

[0015] The comparison module is used to output a comparison signal to the error amplification module when the detection voltage is less than a second reference voltage; the comparison signal is used to instruct to increase the output current of the error amplification module.

[0016] In a possible implementation of the first aspect, the comparison module includes a comparator, a first input end of the comparator is electrically connected to the error amplification module and the first switching switch module respectively, a second input end of the comparator is used to receive the second reference voltage, and an output end of the comparator is electrically connected to the error amplification module.

[0017] In a second aspect, an embodiment of the present application provides a chip comprising a startup control circuit for an LED backlight driver according to any one of the first aspects.

[0018] In a third aspect, an embodiment of the present application provides a display device comprising a plurality of LED light strings and the chip described in the second aspect, wherein all of the LED light strings are electrically connected to the chip.

[0019] Compared with the prior art, the embodiments of the present application have the following beneficial effects:

[0020] The starting control circuit of the LED backlight drive provided by the embodiment of the present application comprises a detection selection module, an error amplification module, a first switching switch module, a control module, a second switching switch module, a logic drive module, a first switch module and a feedback module. The detection selection module can detect a plurality of first voltages and output a detection voltage to the first switching switch module. Whether the value of the first voltage is within a preset range can be determined to confirm the connection state of each LED lamp string. If each first voltage is within the preset range, it indicates that all the LED lamp strings are normally connected. At this time, the first switching switch module turns on the first input end and the output end of the error amplification module according to the first switching control signal, that is, the error amplification module is configured in the form of a unit gain buffer, and the first reference voltage can be used to charge the compensation capacitor, so as to quickly increase the voltage (COMP voltage) at the output end of the error amplification module. The second switching switch module transmits an overcurrent protection signal to the logic drive module according to the second switching control signal, and the logic drive module outputs a first drive signal to the first switch module according to the oscillation signal, the feedback signal and the overcurrent protection signal, so as to turn off the first switch module, and then increase the output voltage of the Boost, thereby gradually increasing the first voltage.

[0021] With the gradual increase of the first voltage, when the minimum voltage (i.e. the detection voltage) in the plurality of first voltages is greater than the first reference voltage, it indicates that the output voltage of the Boost is sufficient to start the current ramp of the LED lamp string. At this time, the first switching switch module turns on the first input end of the error amplifier and the detection selection module according to the third switching control signal, that is, the error amplification module is connected to the loop, so that it starts to work in the form of a closed loop. At the same time, the second switching switch module turns on the control module and the logic drive module according to the fourth switching control signal, that is, the control module outputs a control signal to the logic drive module according to the reference voltage, the oscillation signal and the current flowing through the first switch module, and the logic drive module outputs a second drive signal to the first switch module according to the oscillation signal, the control signal and the feedback signal, so as to turn on or turn off the first switch module. Since the voltage (COMP voltage) at the output end of the error amplification module has been raised to a high level by the unit gain buffer mode in the previous stage, after the error amplification module is connected to the loop, it is not necessary to start from zero to raise the COMP voltage, and the duty cycle of the first switch module can be directly adjusted quickly by the high COMP voltage, so that the output voltage of the Boost changes quickly to match the demand of the current ramp of the LED lamp string.

[0022] As can be seen, the startup control circuit for the LED backlight driver provided in the embodiment of the present application pre-charges the compensation capacitor to increase the COMP voltage during the Boost startup phase by configuring the operating mode of the error amplification module in stages and switching the signal transmitted to the logic driver module. This allows the Boost to respond more quickly when the LED light string enters the current ramp phase, ultimately ensuring that the LED current ramp is output according to a preset pattern. This solves the problem of conventional LED backlight driver startup schemes where the Boost cannot respond in a timely manner when the LED light string current changes rapidly. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0024] Figure 1 This is a schematic diagram of the application circuit of the existing LED backlight driver startup control solution;

[0025] Figure 2 This is a chip circuit diagram of an existing LED backlight driver startup control solution;

[0026] Figure 3 This is a principle block diagram of a startup control circuit for an LED backlight driver provided in one embodiment of the present application;

[0027] Figure 4 This is a circuit connection diagram of a startup control circuit for an LED backlight driver provided in one embodiment of the present application;

[0028] Figure 5 This is a circuit connection diagram of a startup control circuit for an LED backlight driver provided in another embodiment of the present application;

[0029] Figure 6 This is a principle block diagram of a startup control circuit for an LED backlight driver provided in another embodiment of the present application;

[0030] Figure 7 This is a circuit connection diagram of a startup control circuit for an LED backlight driver provided in another embodiment of the present application;

[0031] Figure 8 This is a circuit connection diagram of a startup control circuit for an LED backlight driver provided in another embodiment of the present application;

[0032] Figure 9 This is a flowchart of the startup control of the LED backlight driver provided in one embodiment of the present application.

[0033] In the figure: 10, LED backlight drive startup control circuit; 101, detection selection module; 102, error amplification module; 103, first switching switch module; 104, control module; 105, second switching switch module; 106, logic drive module; 107, first switch module; 108, feedback module; 109, current detection module; 110, third switching switch module; 111, comparison module. DETAILED DESCRIPTION

[0034] In the following description, specific details such as specific system structures and techniques are provided for purposes of illustration rather than limitation to facilitate a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid obscuring the description of the present application with unnecessary detail.

[0035] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or collections thereof.

[0036] It will also be understood that the term "and / or" used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0037] As used in this specification and the appended claims, the term "if" can be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0038] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0039] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more but not all embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof all mean "including but not limited to," unless otherwise specifically emphasized.

[0040] like Figure 1 As shown in the figure, the common application circuit is to drive LED light strings after boosting the input voltage through Boost. The number of light strings ranges from 1 to 6 depending on the application, and each string contains 6 to 10 LED lights. Figure 2 As shown, traditional LED backlight driver startup schemes typically feed the minimum LED headroom voltage (i.e., CH1-CH6) into the boost circuit's error amplifier input, which then regulates the boost's output voltage. Boost circuits typically employ asynchronous rectification, using an external Schottky diode and an internal N-type pull-down diode. However, this design results in a slow build-up of the boost's output voltage, making it unable to respond quickly to rapid changes in the LED string's current.

[0041] To address the above-mentioned issues, an embodiment of the present application provides a startup control circuit for an LED backlight driver, comprising a detection and selection module, an error amplification module, a first switching module, a control module, a second switching module, a logic driver module, a first switching module, and a feedback module. The detection and selection module can detect multiple first voltages and output the detection voltages to the first switching module. The connection status of each LED string can be confirmed by determining whether the first voltage value is within a preset range. If each first voltage is within the preset range, it indicates that all LED strings are properly connected. At this point, the first switching module connects the first input and output terminals of the error amplification module in response to a first switching control signal, configuring the error amplification module as a unity-gain buffer. The compensation capacitor can be charged using a first reference voltage, thereby rapidly increasing the voltage at the output of the error amplification module (i.e., the COMP voltage). The second switching module transmits an overcurrent protection signal to the logic driver module in response to the second switching control signal. The logic driver module outputs a first drive signal to the first switching module based on the oscillation signal, the feedback signal, and the overcurrent protection signal, thereby shutting down the first switching module, thereby increasing the Boost output voltage and gradually increasing the first voltage.

[0042] As the first voltage gradually increases, when the minimum voltage among the multiple first voltages (i.e., the detection voltage) exceeds the first reference voltage, it indicates that the boost output voltage is sufficient to initiate the current ramp of the LED string. At this point, the first switch module, in response to a third switching control signal, connects the first input of the error amplifier and the detection selection module, effectively connecting the error amplifier module to the loop and enabling closed-loop operation. Simultaneously, the second switch module, in response to a fourth switching control signal, connects the control module and the logic driver module. This transmits a control signal, output by the control module based on the reference voltage, the oscillation signal, and the current flowing through the first switch module, to the logic driver module. The logic driver module then outputs a second drive signal to the first switch module based on the oscillation signal, the control signal, and the feedback signal, to turn the first switch module on or off. Because the voltage at the output of the error amplifier module (COMP voltage) has been boosted to a high level using the unity-gain buffer mode in the previous stage, the error amplifier module, now connected to the loop, does not need to increase the COMP voltage from zero. Instead, it can quickly adjust the duty cycle of the first switch module using the higher COMP voltage, resulting in rapid changes in the boost output voltage to match the current ramp requirements of the LED string.

[0043] As can be seen, the startup control circuit for the LED backlight driver provided in the embodiment of the present application pre-charges the compensation capacitor to increase the COMP voltage during the Boost startup phase by configuring the operating mode of the error amplification module in stages and switching the signal transmitted to the logic driver module. This allows the Boost to respond more quickly when the LED light string enters the current ramp phase, ultimately ensuring that the LED current ramp is output according to a preset pattern. This solves the problem of conventional LED backlight driver startup schemes where the Boost cannot respond in a timely manner when the LED light string current changes rapidly.

[0044] In order to illustrate the technical solution described in this application, specific embodiments are provided below.

[0045] Figure 3 FIG1 shows a principle block diagram of a startup control circuit 10 for driving an LED backlight according to an embodiment of the present application. Figure 3As shown, the startup control circuit 10 for LED backlight driving includes a detection and selection module 101, an error amplification module 102, a first switch module 103, a control module 104, a second switch module 105, a logic drive module 106, a first switch module 107, and a feedback module 108. The first switch module 103 is electrically connected to the detection and selection module 101 and the error amplification module 102, respectively; the control module 104 is electrically connected to the error amplification module 102, the second switch module 105, and the first switch module 107, respectively; and the logic drive module 106 is electrically connected to the second switch module 105, the first switch module 107, and the feedback module 108, respectively.

[0046] Specifically, the detection and selection module 101 can detect multiple first voltages and output the detected voltages to the first switching module 103. The connection status of each LED string can be confirmed by determining whether the first voltage value is within a preset range. If each first voltage is within the preset range, it indicates that all LED strings are properly connected. At this point, the first switching module 103, in response to a first switching control signal, turns on the first input and output terminals of the error amplification module 102. This configuration configures the error amplification module 102 as a unity-gain buffer. The compensation capacitor can be charged using the first reference voltage Vref1, thereby rapidly increasing the voltage at the output terminal of the error amplification module 102 (i.e., the COMP voltage). The second switching module 105 transmits the overcurrent protection signal OCP to the logic driver module 106 in response to a second switching control signal. The logic driver module 106 outputs a first drive signal to the first switching module 107 based on the oscillation signal OSC, the feedback signal, and the overcurrent protection signal OCP, turning off the first switching module 107. This increases the Boost output voltage VOUT, thereby gradually increasing the first voltage.

[0047] As the first voltage gradually increases, when the minimum voltage among the multiple first voltages (i.e., the detection voltage) exceeds the first reference voltage Vref1, it indicates that the Boost output voltage VOUT is sufficient to initiate the current ramp of the LED string. At this point, the first switch module 103, in response to the third switching control signal, connects the first input terminal of the error amplifier EA and the detection selection module 101, thereby connecting the error amplifier module 102 to the loop and enabling closed-loop operation. Simultaneously, the second switch module 105, in response to the fourth switching control signal, connects the control module 104 and the logic driver module 106. This transmits the control signal output by the control module 104 based on the reference voltage, the oscillation signal OSC, and the current flowing through the first switch module 107 to the logic driver module 106. The logic driver module 106 then outputs a second drive signal to the first switch module 107 based on the oscillation signal OSC, the control signal, and the feedback signal, thereby turning the first switch module 107 on or off. Since the voltage at the output of the error amplifier module 102 (COMP voltage) has been boosted to a higher level in the previous stage through the unity-gain buffer mode, after the error amplifier module 102 is connected to the loop, there is no need to boost the COMP voltage from zero. Instead, the duty cycle of the first switch module 107 can be quickly adjusted directly using the higher COMP voltage, thereby causing the Boost output voltage VOUT to change rapidly to match the current ramp requirements of the LED light string.

[0048] As can be seen, the LED backlight driver startup control circuit 10 provided in the embodiment of the present application pre-charges the compensation capacitor during the Boost startup phase to increase the COMP voltage by configuring the operating mode of the error amplification module 102 in stages and switching the signal transmitted to the logic driver module 106. This speeds up the Boost response when the LED light string enters the current ramp phase, ultimately ensuring that the LED current ramp is output according to a preset pattern. This solves the problem of conventional LED backlight driver startup solutions where the Boost cannot respond promptly to rapid changes in the LED light string current.

[0049] It should be noted that due to the large size of the compensation capacitor, the design must ensure that the COMP charging completion time is less than the rise time of the output voltage VOUT. This can be achieved by increasing the charging current capability of the error amplifier module 102 or by waiting for a period of time after the Boost output voltage VOUT increases to ensure that the COMP voltage rises to the target value. Specifically, after ensuring that the Boost output voltage VOUT is sufficient to initiate the LED string current ramp (increasing the LED string current from zero to the target value), the voltage may have just reached the threshold and not yet fully stabilized. Therefore, it is necessary to wait for a predetermined period of time (e.g., 1-2 milliseconds) to ensure that the Boost output voltage VOUT further stabilizes under closed-loop control and the charge distribution on the compensation capacitor reaches equilibrium. At this point, the current ramp can be initiated again. This allows the Boost to more stably support the LED current demand and prevent current output deviations from a predetermined characteristic (e.g., linear or exponential) due to voltage fluctuations.

[0050] It should be noted that due to the characteristics of LED string loads, when the boost output voltage VOUT has not yet reached the voltage required for LED turn-on, the voltages at CH1-CH6 (the output terminals of each LED string) are essentially close to ground. If the boost loop is not properly controlled at this point, it will continue to operate at its maximum duty cycle, resulting in excessive inductor current, causing audible noise and even device burnout.

[0051] To address this issue, traditional control methods mainly include the following: one is to limit the switching current of the power tube during startup until the LED light string is turned on, and then switch to normal current limit; the other is to gradually release the current limit using a method similar to soft start. As the output voltage VOUT increases, the current limit value increases synchronously; in addition, because the boost circuit is usually designed with a narrow bandwidth to ensure stability, a large-capacity compensation capacitor (either internal or external) is used internally. By controlling the charging current of the capacitor, the capacitor voltage rises slowly, which can also achieve a gradual increase in the duty cycle.

[0052] The present application adopts a solution of controlling current limiting and built-in compensation capacitor (the built-in design can save one pin), and configures the working mode of the error amplifier module 102 in stages, so that the Boost output voltage VOUT is established faster and the LED current ramp can be output according to the preset rule.

[0053] It should be noted that the threshold of the over-current protection signal OCP can be selected according to the size of the load capacitance and the required settling time.

[0054] In one embodiment of the present application, Figure 4 and Figure 5As shown, the detection and selection module 101 includes LED open circuit detection and minimum LED selection. The LED open circuit detection is used to monitor the connection status of each LED string in real time. Specifically, by detecting abnormal changes in the first voltage (such as a sudden increase in the voltage of a certain line to near the boost output voltage VOUT), it determines whether the corresponding LED string has an open circuit or short circuit fault. This provides a basis for subsequent fault protection and avoids circuit abnormalities caused by open or short circuits. The minimum LED selection is used to select the minimum value from the first voltages of multiple LED strings and transmit it to the error amplification module 102. This is because the minimum first voltage directly reflects the status of the string that most needs a boost output voltage VOUT. If this minimum value is greater than the first reference voltage Vref1, it means that the voltages of all LED strings are greater than the first reference voltage Vref1.

[0055] In one embodiment of the present application, the error amplification module 102 includes an error amplifier EA, a first input end of the error amplifier EA is electrically connected to the first switching switch module 103, a second input end of the error amplifier EA is used to receive a first reference voltage Vref1, and an output end of the error amplifier EA is electrically connected to the control module 104 and the first switching switch module 103, respectively.

[0056] Specifically, the inverting input terminal of the error amplifier EA serves as the first input terminal, and the non-inverting input terminal of the error amplifier EA serves as the second input terminal, for receiving the first reference voltage Vref1. Figure 4 As shown, during the Boost on phase (when the LED string is not yet turned on or the voltage has not reached the threshold), the first switching module 103 directly connects the inverting input of the error amplifier EA to its output (COMP), configuring the error amplifier EA as a unity-gain buffer. At this point, the first reference voltage Vref1 received at the non-inverting input directly drives the compensation capacitor to charge through the buffer, rapidly raising the COMP voltage to a higher level. This design allows for a voltage regulation margin in the subsequent current ramp phase, preventing Boost response delays due to insufficient initial voltage. Figure 5 As shown, during the current ramp phase, the first switching module 103 disconnects the inverting input from the COMP terminal and instead connects it to the output of the detection selection module 101. At this point, the error amplifier EA is connected to the closed-loop control loop. Its non-inverting input still receives the first reference voltage Vref1, while its inverting input receives the detection voltage. The error amplifier EA compares the difference between the two and adjusts the COMP voltage, controlling the Boost output voltage VOUT to match the changes in the LED string current in real time. Because the COMP voltage has already been boosted in buffer mode, the closed-loop Boost can quickly respond to the LED string current ramp requirements, ensuring that the current output follows the preset pattern.

[0057] In one embodiment of the present application, the first switching switch module 103 includes a first transmission gate, a first end of the first transmission gate is electrically connected to the first input end of the error amplification module 102, a second end of the first transmission gate is electrically connected to the detection selection module 101, a third end of the first transmission gate is electrically connected to the output end of the error amplification module 102, and a control end of the first transmission gate is used to receive the first switching control signal and the third switching control signal.

[0058] Specifically, the first transmission gate can switch between two states by receiving a first switching control signal and a third switching control signal. Specifically, during the boost startup phase, the first transmission gate receives the first switching control signal and connects the output terminal and the inverting input terminal of the error amplifier EA, forming a unity-gain buffer, allowing the error amplifier EA to rapidly increase the COMP voltage in open-loop mode. During the current ramp phase, the first transmission gate receives the third switching control signal and connects the detection selection module 101 to the inverting input terminal of the error amplifier EA, causing the error amplifier EA to enter a closed-loop control state and adjust the COMP voltage based on the detection voltage and the first reference voltage Vref1.

[0059] In one embodiment of the present application, Figure 4 and Figure 5 As shown, the control module 104 includes a first operational amplifier, a PWM controller, an accumulator, and a slope compensation circuit. The negative input of the first operational amplifier is electrically connected to the output of the accumulator, the positive input of the first operational amplifier is electrically connected to the output of the error amplifier EA, and is configured to receive a reference voltage. The output of the first operational amplifier is electrically connected to the PWM controller. The first input of the accumulator is electrically connected to the first switching module 107, and the second input of the accumulator is electrically connected to the slope compensation circuit. The slope compensation circuit is configured to receive the oscillation signal OSC output by the oscillator.

[0060] Specifically, the accumulator is configured to accumulate the compensation signal output by the slope compensation and the current signal flowing through the first switch module 107, and output the accumulated signal to the negative input terminal of the first op amp. The first op amp outputs a first op amp signal to the PWM controller based on the accumulated signal and a reference signal. The PWM controller outputs a PWM signal based on the first op amp signal.

[0061] It should be noted that since the design of the control module 104 is a conventional design architecture of a switching power supply, this type of design is relatively mature in the field of switching power supplies, and the relevant principles are in line with conventional design logic in the industry, so it will not be elaborated on here.

[0062] In one embodiment of the present application, the second switching switch module 105 includes a second transmission gate, a first end of the second transmission gate is electrically connected to the control module 104, a second end of the second transmission gate is used to receive the overcurrent protection signal OCP, a third end of the second transmission gate is electrically connected to the logic drive module 106, and a control end of the second transmission gate is used to receive the second switching control signal and the fourth switching control signal.

[0063] Specifically, by receiving the second switching control signal and the fourth switching control signal, the second transmission gate can switch between two states. Specifically, during the Boost startup phase, the second transmission gate receives the second switching control signal and transmits the overcurrent protection signal OCP to the logic driver module 106 to shut down the first switch module 107. During the current ramp phase, the second transmission gate receives the fourth switching control signal and connects the control module 104 to the logic driver module 106, transmitting the control signal to the logic driver module 106 to control the switching timing of the first switch module 107. This allows the Boost output voltage VOUT to be dynamically adjusted according to the LED light string current ramp requirements, achieving precise control of the LED light string current. Through this switching, the system not only implements overcurrent protection during the startup phase but also restores the normal control loop during the current ramp phase, ensuring the safety and stability of the Boost circuit under different operating conditions.

[0064] In one embodiment of the present application, Figure 4 and Figure 5 As shown, the logic driving module 106 includes an OR gate and a first trigger, the first input end of the OR gate is electrically connected to the second switching switch module 105, the second input end of the OR gate is electrically connected to the feedback module 108, the output end of the OR gate is electrically connected to the first input end of the first trigger, the second input end of the first trigger is used to receive the oscillation signal OSC, and the output end of the first trigger is electrically connected to the first switch module 107.

[0065] Specifically, such as Figure 4 As shown, during the Boost startup phase, the first input terminal of the OR gate is used to receive the overcurrent protection signal OCP, and the second input terminal is used to receive the feedback signal. The OR gate outputs a first logic signal to the first input terminal of the first trigger according to the overcurrent protection signal OCP and the feedback signal. The first trigger outputs a first drive signal according to the first logic signal and the oscillation signal OSC to turn off the first switch module 107. Figure 5 As shown, during the current ramp phase, the first input of the OR gate is used to receive the PWM signal. The OR gate outputs a second logic signal to the first input of the first trigger based on the PWM signal and the feedback signal. The first trigger outputs a second drive signal based on the second logic signal and the oscillation signal OSC to turn the first switch module 107 on or off.

[0066] It should be noted that a driver is further provided between the first trigger and the first switch module 107 to improve the driving capability of the first switch module 107 .

[0067] Exemplarily, the first trigger may select an RS trigger.

[0068] In one embodiment of the present application, Figure 4 and Figure 5 As shown, the first switch module 107 includes a first switch tube Q1, the gate of the first switch tube Q1 is electrically connected to the logic drive module 106, the drain of the first switch tube Q1 is used to be electrically connected to the inductor and the anode of the diode in the Boost, respectively, and the source of the first switch tube Q1 is grounded through a resistor.

[0069] Specifically, the first switch Q1 functions as a switching device, turning on or off based on a drive signal received by the gate. During the Boost startup phase, the first switch Q1 turns off based on the first drive signal, increasing the Boost output voltage VOUT. During the current ramp phase, the first switch Q1 turns on or off based on the second drive signal, adjusting the Boost output voltage VOUT to match the current ramp requirements of the LED light string.

[0070] For example, designers can select the type of the first switch Q1 according to actual conditions, that is, a fully controlled power device such as a metal oxide field effect transistor or an insulated gate bipolar transistor can be used. For example, the first switch Q1 can be selected as an NMOS transistor.

[0071] In one embodiment of the present application, Figure 4 and Figure 5 As shown, the feedback module 108 includes two voltage-dividing resistors and a feedback comparator CMP. The positive input of the feedback comparator CMP is connected to the common end of the two voltage-dividing resistors, the negative input of the feedback comparator CMP is used to receive a reference value (1.2V), and the output of the feedback comparator CMP is used to output a feedback signal.

[0072] Specifically, the two voltage-dividing resistors are used to divide the output voltage VOUT and transmit the divided voltage to the feedback comparator CMP. The feedback comparator CMP compares the divided voltage with the 1.2V voltage and outputs a feedback signal.

[0073] In one embodiment of the present application, Figure 6As shown, the startup control circuit 10 of the LED backlight driver also includes a current detection module 109 and a third switching switch module 110. The current detection module 109 is electrically connected to the feedback module 108, the detection selection module 101 and the third switching switch module 110 respectively, and the third switching switch module 110 is electrically connected to the second input end of the error amplification module 102.

[0074] Specifically, the current detection module 109 calculates the actual current flowing through the LED string by collecting the Boost output voltage VOUT and the first voltage. It also compares this actual current with a preset target current. When the actual current reaches the target current, it outputs a corresponding detection signal to the third switch module 110 (to trigger subsequent switching operations). Upon receiving the detection signal from the current detection module 109, the third switch module 110 automatically switches the voltage signal connected to the second input terminal of the error amplification module 102 from the first reference voltage Vref1 used during the Boost startup and current ramp phases to the steady-state reference voltage Vref used during steady-state operation.

[0075] It should be noted that the first reference voltage Vref1 is greater than the steady-state reference voltage Vref. During the startup and current ramp stages, the first reference voltage Vref1 is relatively high, and the error amplification module 102 will control the Boost circuit to output a higher voltage margin based on the high reference voltage (that is, the headroom voltage of the LED light string is larger). This margin can ensure that even if the LED current rises rapidly (such as a fast ramp speed), the Boost output voltage VOUT can quickly respond to the current demand, avoiding abnormal current output due to insufficient voltage (such as deviation from the linear or exponential law), thereby ensuring the stability of the current ramp process. When the current flowing through the LED light string reaches the target value (enters steady-state operation), the third switching switch module 110 switches the reference voltage to a lower steady-state reference voltage Vref, such as Figure 7 At this time, the Boost output voltage VOUT will decrease accordingly as the reference voltage decreases, and the headroom voltage of the LED string will decrease. This means that while ensuring the stability of the LED string current, unnecessary voltage loss is reduced, the overall power consumption of the circuit is reduced, and the energy efficiency during steady-state operation is improved.

[0076] It should be noted that during the startup phase, using a first reference voltage Vref1 that is higher than the steady-state reference voltage Vref ensures that the COMP voltage can be established from a higher voltage when the loop starts working. The higher the COMP voltage, the larger the corresponding Boost duty cycle, and when the LED light string needs a high current, it can be met more quickly. Even if the LED does not have a high current load, the COMP voltage can be gradually reduced to adapt to the loop requirements. During the current ramp phase, the reference voltage of the error amplifier EA still maintains the higher first reference voltage Vref1, which can provide the LED light string with a higher headroom voltage and ensure the current of the LED light string. If the Boost output voltage VOUT cannot maintain the LED current and begins to decrease, the error amplifier EA can also respond more quickly, thereby improving the response speed.

[0077] When the load is too large, that is, multiple LED light strings are started at the same time or there are a large number of LED light strings, the required initial drive current is large. There may be a problem that the Boost output voltage VOUT rises slowly, and the Boost circuit cannot output a higher voltage to meet the load requirements, making it difficult to quickly reach the threshold for turning on the LED light strings.

[0078] In order to solve the above problems, in one embodiment of the present application, Figure 8 As shown, the startup control circuit 10 for LED backlight driving further includes a comparison module 111 , which is electrically connected to the error amplification module 102 and the first switch module 103 , respectively.

[0079] Specifically, the comparison module 111 can receive a detection voltage and a second reference voltage Vref2. When the detection voltage is less than the second reference voltage Vref2, the comparison module 111 outputs a comparison signal to the error amplifier EA. The comparison signal can increase the output current of the error amplifier EA, accelerate the charging of the compensation capacitor, and cause the COMP voltage to rise faster, thereby increasing the duty cycle of the first switch Q1 and shortening the output voltage VOUT settling time.

[0080] In one embodiment of the present application, Figure 8 As shown, the comparison module 111 includes a comparator CMP, a first input end of the comparator CMP is electrically connected to the error amplification module 102 and the first switching module 103 respectively, a second input end of the comparator CMP is used to receive the second reference voltage Vref2, and an output end of the comparator CMP is electrically connected to the error amplification module 102.

[0081] Specifically, the negative input terminal of comparator CMP serves as the first input terminal of comparator CMP, and the positive input terminal of comparator CMP serves as the second input terminal of comparator CMP. When the detection voltage is less than the second reference voltage Vref2, comparator CMP outputs a high-level comparison signal. The comparison signal passes through the current mirror or auxiliary circuit within the error amplifier EA, increasing the output stage bias current of the error amplifier EA. This improves the drive capability of the error amplifier EA, accelerates the charging of the compensation capacitor, and causes the COMP voltage to rise faster.

[0082] The following combination Figures 3 to 9 The startup principle and startup process of the LED backlight driver provided in the embodiment of the present application are described in detail.

[0083] Phase 1: Pre-start detection and protection (Boost not started, state ready)

[0084] After the LED backlight is powered on, it first loads the Efuse or MTP value. After loading is complete (i.e., LOAD_OK), it enters the IDLE state. Next, the detection and selection module 101 first checks the first voltage of each LED string (CH1-CH6) to determine whether the string has an open circuit or short circuit fault (i.e., LED_INIT_CHECK). If any first voltage exceeds a preset range, the system triggers fault protection (such as recording the fault status in a register and shutting down the corresponding branch). If all first voltages are within the preset range (i.e., the light string connection is normal), the startup process proceeds to the next stage.

[0085] Phase 2: Boost startup and COMP voltage precharge (voltage establishment, preparation for ramp)

[0086] After confirming that the LED string is properly connected, the system enters the Boost startup phase (i.e., EN_BST = 1). The logic driver module 106 controls the first switch Q1 to shut down based on the overcurrent protection signal OCP. The Boost starts to boost the output voltage VOUT, driving the first voltages of CH1-CH6 to rise synchronously. In response to the first switching control signal, the first switching module 103 connects the inverting input of the error amplifier module 102 to its output via a first transmission gate, configuring the error amplifier EA as a unity-gain buffer. At this point, the non-inverting input of the error amplifier EA receives the first reference voltage Vref1 (higher than the steady-state reference voltage Vref). This high reference voltage rapidly charges the compensation capacitor, significantly increasing the COMP voltage (reserving regulation margin for subsequent rapid response). Simultaneously, in response to the second switching control signal, the second switching module 105 transmits the overcurrent protection signal OCP to the logic driver module 106 via a second transmission gate. At this stage, the Boost has not yet output the voltage VOUT. If it is started directly, the inductor current may be out of control due to the load not being turned on. The overcurrent protection signal OCP will limit the maximum duty cycle of the power tube in advance to avoid the risk of overcurrent in the early stage of startup (such as excessive inductor current causing howling or device damage).

[0087] During this process, the detection selection module 101 continuously monitors each first voltage. When the minimum voltage among the multiple first voltages is lower than the first reference voltage Vref1, it indicates that the Boost output voltage VOUT is not yet sufficient to turn on the LED light string. The system maintains the current state and continues to increase the output voltage VOUT and the COMP voltage.

[0088] Phase 3: Current ramp start and loop switching (LED string turns on, current ramps)

[0089] As the Boost output voltage VOUT and the first voltage increase, when the detection selection module 101 detects that the minimum first voltage is greater than the first reference voltage Vref1, it indicates that the LED lamp string has met the conduction conditions and the system enters the current ramp phase (ie, LED_RAMP).

[0090] The first switching module 103 receives the third switching control signal, and its first transmission gate disconnects the inverting input of the error amplifier EA from its output, connecting it instead to the output of the detection selection module 101. This switches the error amplifier EA from unity-gain buffer mode to closed-loop control mode, dynamically adjusting the COMP voltage based on the detection voltage. The second switching module 105 receives the fourth switching control signal, and its second transmission gate disconnects the overcurrent protection signal OCP from the logic driver module 106, connecting the PWM signal output by the control module 104 to the logic driver module 106. At this point, the switching of the first switch Q1 is controlled by the control module 104, which adjusts the duty cycle in real time based on the COMP voltage to match the LED current increase demand. The LED string begins to enter a current ramp according to a preset pattern (linear or exponential). The current detection module 109 monitors the current flowing through the LEDs in real time and feeds the detection results back to the detection selection module 101. Because the COMP voltage is precharged during the startup phase, the boost module can quickly respond to the voltage requirements of the current ramp, ensuring that the LED string current increases according to the preset pattern and avoiding output abnormalities caused by response delays.

[0091] Phase 4: Steady-state switching and normal operation (current meets standards, stable output)

[0092] When the current detection module 109 detects that the LED string current has reached the target current, it outputs a detection signal to the third switch module 110. The third switch module 110 switches the reference voltage at the non-inverting input of the error amplifier module 102 from the first reference voltage Vref1 to the steady-state reference voltage Vref, reducing the redundancy of the boost output voltage VOUT and lowering power consumption (i.e., the ACTIVE state). The error amplifier module 102 maintains closed-loop control based on the steady-state reference voltage Vref and the detection voltage, stabilizing the boost output voltage VOUT at a level that meets the target LED current. The control module 104 maintains the stability of the PWM signal through conventional mechanisms, ensuring long-term stable LED current output, completing the startup control process.

[0093] Since the adjustment of the reference voltage will cause the output voltage VOUT to drop, the output voltage VOUT of the Boost is not a concern at this time, because the headroom voltage can always ensure the output current of the LED string during this process.

[0094] In addition, both the third and fourth stages require real-time detection of the LED light string connection status to ensure the safety and reliability of the system.

[0095] The entire startup process solves the adaptation problem of slow Boost response and fast LED current ramp in traditional solutions through timing coordination and mode switching of each module, and improves startup safety and steady-state efficiency through dynamic adjustment.

[0096] The application also discloses a chip, which adopts the starting control circuit 10 of the LED backlight drive and can significantly shorten the starting time of the Boost circuit and meet the fast dimming requirement of a high dynamic range display device. Meanwhile, the integration and hardware economy of the chip are improved.

[0097] The application also discloses a display device, which comprises a plurality of LED lamp strings and the chip and is electrically connected with the chip. The display device can quickly establish the Boost output voltage in the starting stage and ensure the consistency of the current rise when the plurality of LED lamp strings are simultaneously lighted. When an open circuit or short circuit fault occurs in a certain LED lamp string, the system immediately triggers protection and accurately locates the fault point, thereby improving the system reliability. Meanwhile, the voltage redundancy when the plurality of lamp strings are connected in parallel can be reduced, and the overall power consumption of the system is reduced. Therefore, the display device can meet the high dynamic dimming requirement of a large-size liquid crystal display screen and can also be adapted to the scene sensitive to the starting speed, such as a vehicle-mounted screen and a VR device. The display device deeply integrates the intelligent control chip and the plurality of LED lamp strings, optimizes the starting time and the dynamic response through cooperation, and provides a complete solution for the display application with high image quality and high energy efficiency.

[0098] Since the processes and functions realized by the display device and the chip in the embodiment are basically corresponding to the processes and functions realized by the LED backlight drive starting control circuit, the description of the embodiment is not described in detail, and the related description in the foregoing embodiments can be referred to, and will not be described here.

[0099] The above-described embodiments are only used to illustrate the technical solutions of the application, rather than limit them; although the application is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the application, and should be included in the protection scope of the application.

Claims

1. A startup control circuit for LED backlight driving, characterized in that: It includes a detection and selection module, an error amplification module, a first switching switch module, a control module, a second switching switch module, a logic drive module, a first switch module and a feedback module, wherein the first switching switch module is electrically connected to the detection and selection module and the error amplification module respectively, the control module is electrically connected to the error amplification module, the second switching switch module and the first switch module respectively, and the logic drive module is electrically connected to the second switching switch module, the first switch module and the feedback module respectively; The detection selection module is configured to output a detection voltage to the first switching module based on a plurality of first voltages, wherein the first voltage is the voltage at the output end of the LED light string, and the detection voltage is the minimum voltage among the plurality of first voltages; when each of the first voltages is within a preset range, the first switching module is configured to conduct the first input end and the output end of the error amplification module based on a first switching control signal; the error amplification module is configured to output a reference voltage based on a first reference voltage received at a second input end of the error amplification module; and the second switching module is configured to transmit an overcurrent protection signal to the logic driver module based on a second switching control signal; When the detection voltage is greater than the first reference voltage, the first switching switch module is used to connect the first input end of the error amplification module and the detection selection module according to a third switching control signal; the error amplification module is used to output a reference voltage according to the detection voltage and the first reference voltage; the second switching switch module is used to connect the control module and the logic drive module according to a fourth switching control signal.

2. The startup control circuit for LED backlight driving according to claim 1, characterized in that: The startup control circuit of the LED backlight driver further includes a current detection module and a third switch module, wherein the current detection module is electrically connected to the feedback module, the detection selection module and the third switch module respectively, and the third switch module is electrically connected to the second input end of the error amplification module; The current detection module is used to obtain the current flowing through the LED light string based on the output voltage and the first voltage, and when the current flowing through the LED light string reaches the target current, the current detection module is used to output a detection signal to the third switching switch module; the third switching switch module is used to transmit the steady-state reference voltage to the second input end of the error amplification module according to the detection signal.

3. The startup control circuit for LED backlight driving according to claim 2, characterized in that: The first reference voltage is greater than the steady-state reference voltage.

4. The startup control circuit for LED backlight driving according to claim 1, characterized in that: The error amplification module includes an error amplifier, a first input end of the error amplifier is electrically connected to the first switching switch module, a second input end of the error amplifier is used to receive the first reference voltage, and an output end of the error amplifier is electrically connected to the control module and the first switching switch module respectively.

5. The startup control circuit for LED backlight driving according to claim 1, characterized in that: The first switching switch module includes a first transmission gate, a first end of the first transmission gate is electrically connected to the first input end of the error amplification module, a second end of the first transmission gate is electrically connected to the detection selection module, a third end of the first transmission gate is electrically connected to the output end of the error amplification module, and a control end of the first transmission gate is used to receive the first switching control signal and the third switching control signal; The second switching switch module includes a second transmission gate, a first end of the second transmission gate is electrically connected to the control module, a second end of the second transmission gate is used to receive the overcurrent protection signal, a third end of the second transmission gate is electrically connected to the logic drive module, and a control end of the second transmission gate is used to receive the second switching control signal and the fourth switching control signal.

6. The startup control circuit for LED backlight driving according to claim 1, characterized in that: The logic drive module includes an OR gate and a first trigger, the first input end of the OR gate is electrically connected to the second switching switch module, the second input end of the OR gate is electrically connected to the feedback module, the output end of the OR gate is electrically connected to the first input end of the first trigger, the second input end of the first trigger is used to receive an oscillation signal, and the output end of the first trigger is electrically connected to the first switch module.

7. The startup control circuit for LED backlight driving according to any one of claims 1 to 6, characterized in that: The startup control circuit of the LED backlight driver further includes a comparison module, which is electrically connected to the error amplification module and the first switch module respectively; The comparison module is used to output a comparison signal to the error amplification module when the detection voltage is less than a second reference voltage; the comparison signal is used to instruct to increase the output current of the error amplification module.

8. The startup control circuit for LED backlight driving according to claim 7, characterized in that: The comparison module includes a comparator, a first input end of the comparator is electrically connected to the error amplification module and the first switching module respectively, a second input end of the comparator is used to receive the second reference voltage, and an output end of the comparator is electrically connected to the error amplification module.

9. A chip, characterized in that: A startup control circuit for driving an LED backlight comprising the circuit described in any one of claims 1 to 8.

10. A display device, characterized in that: The device comprises a plurality of LED light strings and the chip according to claim 9, wherein all the LED light strings are electrically connected to the chip.

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