Backlight source control circuit

Abstract

The utility model relates to the technical field of backlight power supplies, aims to solve the technical problems of large misoperation and poor stability of a backlight circuit, and discloses a backlight control circuit, which comprises a voltage reduction module U12 for reducing the voltage of a power supply VCC1 into a power supply VCC2, a backlight controller U10 and an enable circuit, and the enable circuit comprises a triode Q14 and a triode Q12. The output end of the voltage reduction module U12 is connected with the enabling end of the backlight controller U10 through a resistor R68, the overvoltage protection circuit comprises an NMOS tube Q11, the source electrode of the NMOS tube Q11 is grounded, the drain electrode of the NMOS tube Q11 is connected with the enabling end of the backlight controller U10, the grid electrode of the NMOS tube Q11 is connected with a first series voltage division circuit, the triode Q12 indirectly controls power supply of the voltage reduction module U12 by controlling the on-off state of the triode Q14, and the voltage reduction module U12 indirectly controls the power supply of the backlight controller U10. An NMOS tube Q11 and a first series voltage division circuit in the overvoltage protection circuit are used for monitoring the voltage of a power supply VCC1 in real time. When the voltage is too high, the NMOS tube Q11 is switched on, the enabling end voltage is directly lowered, and work is stopped, so that overvoltage protection is achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of backlight power supply, in particular to a backlight source control circuit. Background Art

[0002] In the prior art, especially in the backlight circuit, the overvoltage protection performance often has shortcomings. In many traditional circuit designs, the overvoltage protection circuit usually adopts a simple overvoltage detection and shutdown mechanism. However, this design method has some defects. First, when the power supply voltage fluctuates frequently, the overvoltage protection circuit may be triggered frequently, causing the system to switch repeatedly, affecting normal operation. Secondly, the design of the overvoltage protection circuit is usually relatively simple, lacking multi-level and multi-link protection measures, and unable to provide comprehensive protection. This design is particularly insufficient. In addition, the accuracy and reliability of traditional overvoltage protection circuits under high voltage conditions are poor, and it is easy to have problems of misoperation or protection failure, which further reduces the stability and safety of the system. Therefore, the overvoltage protection performance in the prior art is insufficient, and a more flexible, efficient and reliable overvoltage protection circuit is urgently needed to improve the overall protection capability and operational stability of the system. Utility Model Content

[0003] The utility model aims to provide a backlight source control circuit to solve the technical problems of large malfunction and poor stability of the backlight source circuit.

[0004] To achieve the above purpose, a specific technical solution of a backlight source control circuit of the utility model is as follows:

[0005] A backlight source control circuit comprises a step-down module U12 for stepping down a power source VCC1 into a power source VCC2, a backlight controller U10 and an enable circuit connected to the backlight controller U10, wherein the enable circuit comprises a transistor Q14 and a transistor Q12 for controlling the switch of the transistor Q14, wherein the transistor Q14 is used to control the power source VCC1 to supply power to an input end of the step-down module U12, wherein an output end of the step-down module U12 is connected to an enable end of the backlight controller U10 via a resistor R68, and an overvoltage protection circuit is also provided, wherein the overvoltage protection circuit comprises an NMOS transistor Q11, wherein a source of the NMOS transistor Q11 is grounded, a drain of the NMOS transistor Q11 is connected to the enable end of the backlight controller U10, and a gate of the NMOS transistor Q11 is connected to a first series voltage divider circuit, wherein the first series voltage divider circuit is used to detect the voltage of the power source VCC1.

[0006] The transistors Q12 and Q14 in the enabling circuit form a flexible switch control circuit. Q12 indirectly controls the power supply of the buck module U12 by controlling the switch state of Q14, so that the system can turn on or off the backlight controller U10 as needed, providing flexible power management.

[0007] The NMOS tube Q11 in the overvoltage protection circuit and the first series voltage divider circuit connected thereto are used to monitor the voltage of the power supply VCC1 in real time. When the voltage is too high, the NMOS tube Q11 is turned on, directly pulling down the voltage of the enable terminal of the backlight controller U10, preventing the excessive input voltage from damaging the backlight controller U10 and other circuits, thereby achieving overvoltage protection and improving the safety and reliability of the system.

[0008] This circuit can not only protect the backlight controller U10 from overvoltage damage, but also improve the overall stability and life of the system through reasonable power management and the use of step-down modules.

[0009] The multi-level protection circuit design ensures that the system can operate safely and stably under various working conditions, reducing the probability of failure caused by power fluctuations and overvoltage.

[0010] Furthermore, the transistor Q14 is a PNP transistor, the transistor Q12 is an NPN transistor, the base of the transistor Q12 is used to input a turn-on voltage through a resistor R65, the collector of the transistor Q12 is connected to the power supply VCC1 through resistors R72, R75 and R76 in sequence, and the emitter of the transistor Q12 is grounded through a resistor R67; the base of the transistor Q14 is connected to the collector of the transistor Q12 through resistors R75 and R72, the emitter of the transistor Q14 is connected to the power supply VCC1, and the collector of the transistor Q14 is connected to the input end of the step-down module U12.

[0011] By using a combination of PNP transistor Q14 and NPN transistor Q12, the enabling circuit can achieve efficient power control. Transistor Q12 inputs a turn-on voltage through the base, and through resistor R65, Q14 is turned on or off under appropriate conditions, thereby controlling the power supply of the buck module U12. This design ensures that the system can respond quickly when needed and provide a stable power supply.

[0012] The collector of transistor Q12 is connected to the power supply VCC1 through resistors R72, R75 and R76, and the emitter is grounded through resistor R67. This design can ensure that the transistor Q12 can maintain a stable working state when it is turned on and off, thereby providing a reliable control signal to the transistor Q14, and then controlling the working state of the buck module U12.

[0013] Due to the tight coupling between transistors Q12 and Q14, connected through resistors R75 and R72, transistor Q14 can quickly respond to the state change of transistor Q12. This fast response capability is important for improving the efficiency and performance of the control circuit, especially in applications that require fast switching and precise control.

[0014] Through the precise design of the resistor network (R65, R72, R75, R76, R67), the circuit parameters can be adjusted according to different application requirements, thus achieving more flexible power management and control. This flexibility is very beneficial for adapting to different circuit and equipment requirements.

[0015] Furthermore, the first series voltage divider circuit includes a resistor R73 and a resistor R74, the second end of the resistor R74 is grounded, the first end of the resistor R74 is connected to the second end of the resistor R73, the first end of the resistor R73 is connected to the power supply VCC1 through the resistor R75 and the resistor R76 in sequence, and the common node of the resistor R74 and the resistor R74 is connected to the gate of the NMOS tube Q11.

[0016] The first series voltage divider circuit is composed of a resistor R73 and a resistor R74, which reduces the voltage of the power supply VCC1 to a suitable voltage range by means of resistor voltage division, so that the gate of the NMOS tube Q11 can accurately detect the change of the power supply voltage. When the voltage of the power supply VCC1 is too high, the voltage after voltage division is sufficient to turn on the NMOS tube Q11, thereby realizing protection against overvoltage conditions and ensuring the safe operation of the backlight controller U10.

[0017] The precise voltage division design of resistors R73 and R74 can ensure that the voltage remains stable under any circumstances, avoiding the influence of voltage fluctuation on NMOS tube Q11, and improving the reliability and stability of the circuit. Through the further connection of resistors R75 and R76, the voltage after voltage division can be better controlled, making the operation of the entire circuit more reliable.

[0018] Since the common node of resistor R74 and resistor R73 is directly connected to the gate of NMOS tube Q11, when the voltage of power supply VCC1 changes, the voltage divider circuit can respond quickly and quickly trigger NMOS tube Q11 to turn on or off. This fast response capability is very important in the protection circuit, and it can quickly take protective measures to prevent damage when the voltage is too high.

[0019] Furthermore, capacitor C49 is connected in parallel at both ends of resistor R75 and resistor R76. The addition of capacitor C49 reduces the voltage drop fluctuation of resistor R75 and resistor R76, thereby reducing the probability of circuit malfunction and improving the reliability and stability of the system. The parallel connection of capacitor C49 can effectively filter out high-frequency noise and spike interference on the power supply VCC1, reduce interference to other parts of the circuit, and ensure stable operation of the circuit. Through the bypass effect of the capacitor, capacitor C49 can smooth voltage fluctuations, provide a more stable voltage signal, and prevent the influence of voltage mutation on the circuit.

[0020] The backlight control circuit provided by the utility model has the following advantages:

[0021] The transistors Q12 and Q14 in the enable circuit form a flexible switch control circuit. Q12 indirectly controls the power supply of the buck module U12 by controlling the switch state of Q14, so that the system can turn on or off the backlight controller U10 as needed, providing flexible power management. The NMOS tube Q11 in the overvoltage protection circuit and the first series voltage divider circuit connected to it are used to monitor the voltage of the power supply VCC1 in real time. When the voltage is too high, the NMOS tube Q11 is turned on to directly lower the enable terminal voltage of the backlight controller U10 to prevent the excessive input voltage from damaging the backlight controller U10 and other circuits, thereby achieving overvoltage protection and improving the safety and reliability of the system. This circuit can not only protect the backlight controller U10 from overvoltage damage, but also improve the overall stability and life of the system through reasonable power management and the use of buck modules. The multi-level protection circuit design ensures that the system can operate safely and stably under various working conditions, reducing the probability of failure caused by power supply fluctuations and overvoltage. In addition, a capacitor C49 is connected in parallel across the resistors R75 and R76 to reduce the probability of circuit malfunction. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The backlight controller and its peripheral circuit structure diagram provided by the utility model;

[0023] Figure 2 A structural diagram of a dimming circuit provided for the utility model;

[0024] Figure 3 A circuit diagram of a resistance-capacitance grounding network provided by the utility model;

[0025] Figure 4 This is a structural diagram of the enabling circuit and overvoltage protection circuit provided by the utility model. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.

[0027] See also Figures 1 to 4 The utility model provides a backlight control circuit, which is composed of an internal and external circuit of a power controller U10. It starts working under the control of a main circuit board, outputs four-way driving pulse signals to the excitation circuit, and has overvoltage and overcurrent protection functions.

[0028] The first terminal of the backlight controller U10 is a trigger time setting terminal, which is grounded through a capacitor C36;

[0029] The second terminal of the backlight controller U10 is an overvoltage protection detection terminal, which is connected to an overvoltage protection circuit;

[0030] The third terminal of the backlight controller U10 is an enable terminal, which is connected to an enable circuit;

[0031] See also Figure 4 The enabling circuit includes a step-down module U12, a PNP transistor Q14 and an NPN transistor Q12. The base of the transistor Q12 is input with a start-up voltage through a resistor R65. The collector of the transistor Q12 is connected to the power supply VCC1 through resistors R72, R75 and R76. The emitter of the transistor Q12 is grounded through a resistor R67. The base of the transistor Q14 is connected to the collector of the transistor Q12 through resistors R75 and R72. The emitter of the transistor Q14 is connected to the power supply VCC1. The collector of the transistor Q14 is connected to the input end of the step-down module U12. The output end of the step-down module U12 is connected to the enabling end of the backlight controller U10. The ground end of the step-down module U12 is grounded.

[0032] When the base of transistor Q12 is at a low level, transistor Q12 is turned off. The base of transistor Q14 is connected to power supply VCC1 through resistor R76, and the base of transistor Q14 is at a high level, so transistor Q14 is turned on to supply power to step-down module U12, and step-down module U12 outputs power supply VCC2, and power supply VCC2 is supplied to the enable terminal voltage through resistor R68.

[0033] When the base of transistor Q12 is at a high level, transistor Q12 is turned on, pulling down the base voltage of transistor Q14, and the base of transistor Q14 is at a low level, so transistor Q14 is cut off, and the buck module U12 cannot obtain power through the collector of transistor Q14. The buck module U12 stops outputting the power supply VCC2, and there is no corresponding power supply VCC2 to provide the enable terminal voltage through the resistor R68, and the backlight controller U10 cannot be enabled.

[0034] The overvoltage protection circuit includes an NMOS tube Q11, the gate of the NMOS tube Q11 is connected to a first series voltage divider circuit, the first series voltage divider circuit includes a resistor R73 and a resistor R74, the second end of the resistor R74 is grounded, the first end of the resistor R74 is connected to the second end of the resistor R73, the first end of the resistor R73 is connected to the power supply VCC1 through the resistor R75 and the resistor R76 in sequence, the common node of the resistor R74 and the resistor R74 is connected to the gate of the NMOS tube Q11, the source of the NMOS tube Q11 is grounded, and the drain of the NMOS tube Q11 is connected to the enable end of the backlight controller U10.

[0035] When the power supply VCC1 voltage is too high, the first series voltage divider circuit divides a sufficiently high voltage to the gate of the NMOS transistor Q11, causing the NMOS transistor Q11 to be turned on, directly lowering the enable terminal voltage of the backlight controller U10, thereby playing an overvoltage protection role.

[0036] The 4th terminal of the backlight controller U10 is a soft start setting terminal, which is grounded through a capacitor C54;

[0037] The 5th terminal of the backlight controller U10 is a power input terminal, and the grounding resistor R36 is connected to the power supply VCC2 and grounded through the capacitor C53;

[0038] The 6th terminal of the backlight controller U10 is the signal ground terminal, which is grounded;

[0039] The 7th terminal of the backlight controller U10 is a reference voltage output terminal, which is grounded through a capacitor C52 and connected to the 3rd terminal through a diode D21. The anode of the diode D21 is connected to the 3rd terminal, and the cathode of the diode D21 is connected to the 7th terminal.

[0040] The 8th terminal of the backlight controller U10 is the trigger frequency setting terminal and is vacant;

[0041] The 9th terminal of the backlight controller U10 is a current feedback input terminal, which is connected to a feedback circuit;

[0042] The 10th terminal of the backlight controller U10 is a voltage control system compensation terminal, which is grounded through a resistor R50;

[0043] The 11th terminal of the backlight controller U10 is a first driving signal output terminal.

[0044] The 12th terminal of the backlight controller U10 is a second driving signal output terminal.

[0045] The 13th terminal of the backlight controller U10 is a low-frequency pulse width control signal dimming terminal, which is connected to a dimming circuit;

[0046] See also Figure 1 and Figure 2 The dimming circuit includes two integrally formed diodes D50 connected in series. The anode of the diode D50 is connected to the low-frequency pulse width control signal dimming terminal of the backlight controller U10 through a resistor R32 for inputting the signal SG2. The middle common node of the diode D50 is used for inputting the signal SG1. The cathode of the diode D50 is connected to the voltage control system compensation terminal of the backlight controller U10 through a resistor R34.

[0047] It also includes NMOS tube Q5, NMOS tube Q6, NMOS tube Q9 and NMOS tube Q9. The gate of NMOS tube Q5 is used as the input end of the first dimming mode through resistor R50, the source of NMOS tube Q5 is grounded, and the drain of NMOS tube Q5 is connected to the power supply VCC2 through resistor R41. The gate of NMOS tube Q10 is connected to the drain of NMOS tube Q5, the source of NMOS tube Q10 is grounded, and the drain of NMOS tube Q10 is used to output signal SG2. The source of NMOS tube Q6 is grounded, and NMOS tube Q6 is used as the input end of signal E-PWM through resistor R52 for inputting external dimming pulses. The drain of NMOS tube Q6 is connected to the power supply VCC2 through resistor R54. The source of the NMOS tube Q9 is grounded, the gate of the NMOS tube Q9 serves as the input end of the second dimming mode, the drain of the NMOS tube Q9 is used to output the signal SG1 through the diode D11, the anode of the diode D11 is connected to the drain of the NMOS tube Q9, the cathode of the diode D11 is connected to the middle common node of the diode D50, and is also connected to the current feedback input end of the backlight controller U10 through the resistor R55.

[0048] Working principle of dimming circuit:

[0049] The gate of the NMOS tube Q5 is used as the input terminal of the first dimming mode through the resistor R50. When the input signal is at a high level, Q5 is turned on, and its drain voltage drops, driving the NMOS tube Q10 to be turned on, thereby outputting the signal SG2.

[0050] The source of the NMOS tube Q6 is grounded, and the gate thereof serves as the input end of the signal E-PWM through the resistor R52. When the input signal is at a high level, Q6 is turned on and the drain voltage thereof decreases.

[0051] The gate of the NMOS tube Q9 serves as the input terminal of the second dimming mode. When the input signal is at a high level, Q9 is turned on, and its drain outputs a signal SG1 through a diode D11. The cathode of the diode D11 is connected to the middle common node of the diode D50, and is connected to the current feedback input terminal of the backlight controller U10 through a resistor R55.

[0052] When the E-PWM signal is input, the working state of the dimming circuit is directly controlled through Q6.

[0053] The dimming circuit uses multiple NMOS tubes and diodes in cascade, and realizes multiple dimming modes through different input signals, which can efficiently control the brightness of the LED backlight. By using multiple input signals, the circuit can flexibly adjust the backlight brightness according to different needs to meet a variety of application scenarios. The use of low-frequency pulse width dimming signal control makes the dimming process smoother and more accurate, avoiding visual discomfort caused by stroboscopic light.

[0054] The backlight controller U10 adjusts the LED backlight source through the dimming circuit according to different input signals, thereby achieving different dimming effects.

[0055] The 14th terminal of the backlight controller U10 is a low-frequency pulse width control signal dimming duty DC voltage input terminal, which is connected to the I-PWM port through a resistor R38;

[0056] The 15th terminal of the backlight controller U10 is a low-frequency pulse width control signal dimming frequency setting terminal, which is grounded through capacitors C21, C22 and C23 respectively;

[0057] The 16th terminal of the backlight controller U10 is the ground terminal of the internal power tube, which is grounded;

[0058] The 17th terminal of the backlight controller U10 is a trigger and working frequency time setting resistor terminal, which is grounded through a resistor-capacitor grounding network. The grounding network includes a capacitor C27 and a resistor R28 connected in series, a capacitor C24 and a resistor R29 connected in series, a capacitor C25 and a resistor R30 connected in series, and a capacitor C26 and a resistor R31 connected in series. The above capacitors are connected in parallel and in parallel with the resistor R27. One end of the resistor R27 is connected to the 17th terminal, and the other end of the resistor R27 is grounded.

[0059] The purpose of the RC network design is to set the trigger and operating frequency time of the backlight controller. The RC network adjusts the operating frequency of the controller by changing the value of the capacitor and resistor. Each series capacitor and resistor combination can produce a different time constant (τ = RC), which will affect the charge and discharge time of the circuit, thereby changing the operating frequency of the controller.

[0060] Multiple parallel RC combinations can provide more stable and accurate frequency settings. The time constant of each combination is slightly different, which can reduce the error and fluctuation caused by a single RC component and improve the stability and reliability of the overall system.

[0061] The parallel resistor R27 acts as a damper to further stabilize the voltage and current and reduce the impact of noise and fluctuations on the controller triggering and frequency setting.

[0062] The above-mentioned resistor-capacitor grounding network improves stability and accuracy. By using multiple resistor-capacitor combinations in parallel, the stability and accuracy of frequency setting can be improved, the error caused by the tolerance of a single component can be reduced, and the reliability of the system can be improved.

[0063] The parallel resistor R27 and the plurality of resistors and capacitors combined together can effectively reduce the influence of noise and voltage fluctuations in the circuit on the triggering and operating frequency, thereby improving the performance of the backlight controller.

[0064] By adjusting the values ​​of each resistor and capacitor, the required trigger and operating frequency time can be flexibly set to meet different application requirements.

[0065] It can be seen that the RC grounding network design makes the operating frequency and triggering time of the backlight controller U10 more stable and accurate, while improving the anti-interference ability and the reliability of the overall system.

[0066] Terminal 18 of the backlight controller U10 is a trigger and operating frequency time setting capacitor terminal, which is grounded through capacitor C34;

[0067] The 19th terminal of the backlight controller U10 is a third driving signal output terminal;

[0068] The terminal 20 of the backlight controller U10 is a fourth driving signal output terminal.

[0069] In summary, the utility model provides a backlight source control circuit, in which the transistors Q12 and Q14 in the enabling circuit form a flexible switch control circuit. Q12 indirectly controls the power supply of the buck module U12 by controlling the switch state of Q14, so that the system can turn on or off the backlight controller U10 as needed, providing flexible power management. The NMOS tube Q11 in the overvoltage protection circuit and the first series voltage divider circuit connected thereto are used to monitor the voltage of the power supply VCC1 in real time. When the voltage is too high, the NMOS tube Q11 is turned on, directly pulling down the enabling terminal voltage of the backlight controller U10, preventing the excessive input voltage from damaging the backlight controller U10 and other circuits, thereby achieving overvoltage protection and improving the safety and reliability of the system. The circuit can not only protect the backlight controller U10 from overvoltage damage, but also improve the overall stability and life of the system through reasonable power management and the use of buck modules. The multi-level protection circuit design ensures that the system can operate safely and stably under various working conditions, reducing the probability of failures caused by power supply fluctuations and overvoltage. In addition, a capacitor C49 is connected in parallel across the resistors R75 and R76 to reduce the probability of circuit malfunction.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A backlight source control circuit, comprising a step-down module U12 for stepping down a power source VCC1 into a power source VCC2, a backlight controller U10, and an enabling circuit connected to the backlight controller U10, characterized in that: The enabling circuit includes a transistor Q14 and a transistor Q12 for controlling the switch of the transistor Q14. The transistor Q14 is used to control the power supply VCC1 to supply power to the input end of the step-down module U12. The output end of the step-down module U12 is connected to the enabling end of the backlight controller U10 through a resistor R68. An overvoltage protection circuit is also provided. The overvoltage protection circuit includes an NMOS tube Q11. The source of the NMOS tube Q11 is grounded. The drain of the NMOS tube Q11 is connected to the enabling end of the backlight controller U10. The gate of the NMOS tube Q11 is connected to a first series voltage divider circuit. The first series voltage divider circuit is used to detect the voltage of the power supply VCC1.

2. A backlight source control circuit according to claim 1, characterized in that: The transistor Q14 is a PNP transistor, and the transistor Q12 is an NPN transistor. The base of the transistor Q12 is used to input a turn-on voltage through a resistor R65. The collector of the transistor Q12 is connected to the power supply VCC1 through resistors R72, R75 and R76 in sequence, and the emitter of the transistor Q12 is grounded through a resistor R67; the base of the transistor Q14 is connected to the collector of the transistor Q12 through resistors R75 and R72, the emitter of the transistor Q14 is connected to the power supply VCC1, and the collector of the transistor Q14 is connected to the input end of the step-down module U12.

3. A backlight source control circuit according to claim 2, characterized in that: The first series voltage divider circuit includes a resistor R73 and a resistor R74, the second end of the resistor R74 is grounded, the first end of the resistor R74 is connected to the second end of the resistor R73, the first end of the resistor R73 is connected to the power supply VCC1 through the resistor R75 and the resistor R76 in sequence, and the common node of the resistor R74 and the resistor R74 is connected to the gate of the NMOS tube Q11.

4. A backlight source control circuit according to claim 2, characterized in that: A capacitor C49 is connected in parallel between both ends of the resistor R75 and the resistor R76.

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