Switch control circuit and backlight driver board

Abstract

The present application discloses a switch control circuit and a backlight driving board. The switch control circuit includes a voltage divider circuit, a first transistor and a second transistor. The voltage divider circuit has an input terminal and an output terminal, and the input terminal is connected to a control signal. The control electrode of the first transistor is connected to the output terminal, and the input electrode of the first transistor is connected to a power supply voltage. The control electrode of the second transistor is connected to the output electrode of the first transistor, the input electrode of the second transistor is connected to an input voltage, and the output electrode of the second transistor is connected to the voltage output terminal. The present application can realize that the voltage specification of the control signal in the switch control circuit is adjustable, and avoid circuit logic confusion caused by fluctuations in the control signal.

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular to a switch control circuit and a backlight driving board. Background Art

[0002] In current commercial display modules, the backlight module lamps are driven and lit by the backlight driver board. Since the backlight driver board is a passive module, the opening, closing and brightness of the backlight module lamps all require external signal control. Usually, after the input voltage is input to the backlight driver board, a switch control circuit and a control signal are required to control the opening and closing of the backlight module lamps.

[0003] The switch control circuit is controlled by a control signal to output the input voltage to the backlight driver board. However, since the control signal is interfered by other circuits and ripples in the circuit, the voltage value of the control signal is actually unstable. For example, when the switch control circuit is in the off state, the voltage value of the control signal should be less than 0.7V, but the actual voltage value of the control signal may fluctuate between 0 and 1V, thereby causing the logic of the switch control circuit to be disordered. Summary of the invention

[0004] The present application provides a switch control circuit and a backlight circuit board to solve the technical problem that the voltage value of a control signal in the existing switch control circuit fluctuates, resulting in circuit logic disorder.

[0005] The present application provides a switch control circuit, which includes:

[0006] A voltage divider circuit, the voltage divider circuit having an input end and an output end, the input end receiving a control signal;

[0007] a first transistor, wherein a control electrode of the first transistor is connected to the output terminal, and an input electrode of the first transistor is connected to the power supply voltage; and

[0008] A second transistor, wherein a control electrode of the second transistor is connected to an output electrode of the first transistor, an input electrode of the second transistor is connected to an input voltage, and an output electrode of the second transistor is connected to a voltage output terminal.

[0009] Optionally, in some embodiments of the present application, the voltage-dividing circuit includes a first voltage-dividing resistor and a second voltage-dividing resistor;

[0010] One end of the first voltage-dividing resistor is connected to the control signal, the other end of the first voltage-dividing resistor and one end of the second voltage-dividing resistor are both connected to the output end, and the other end of the second voltage-dividing resistor is connected to the power supply voltage.

[0011] Optionally, in some embodiments of the present application, at least one of the first voltage-dividing resistor and the second voltage-dividing resistor is a variable resistor.

[0012] Optionally, in some embodiments of the present application, the voltage divider circuit includes at least one diode, the anode of the diode is connected to the control signal, and the cathode of the diode is connected to the output end.

[0013] Optionally, in some embodiments of the present application, the voltage divider circuit includes a short-circuit resistor, one end of the short-circuit resistor is connected to the control signal, the other end of the short-circuit resistor is connected to the output end, and the resistance of the short-circuit resistor is zero.

[0014] Optionally, in some embodiments of the present application, the switch control circuit further includes a capacitor, one plate of the capacitor is connected to the output end, and the other plate of the capacitor is connected to the power supply voltage.

[0015] Optionally, in some embodiments of the present application, the switch control circuit also includes a first voltage-stabilizing resistor and a second voltage-stabilizing resistor, one end of the first voltage-stabilizing resistor is connected to the input voltage, the other end of the first voltage-stabilizing resistor and one end of the second voltage-stabilizing resistor are both connected to the control electrode of the second transistor, and the other end of the second voltage-stabilizing resistor is connected to the output electrode of the first transistor.

[0016] Optionally, in some embodiments of the present application, the switch control circuit further includes a current limiting resistor;

[0017] One end of the current limiting resistor is connected to the output electrode of the second transistor, and the other end of the current limiting resistor is connected to the voltage output end.

[0018] Optionally, in some embodiments of the present application, the first transistor is an NPN transistor, the second transistor is a PNP transistor, and the power supply voltage is a ground voltage.

[0019] Correspondingly, the present application also provides a backlight driving board, which includes the switch control circuit described in any one of the above items, and the backlight driving board also includes a power pin, a ground pin and a control pin, the power pin is connected to the input voltage, the ground pin is connected to the power supply voltage, and the control pin is connected to the control signal.

[0020] The present application discloses a switch control circuit and a backlight driving board, wherein the switch control circuit includes a voltage divider circuit, a first transistor and a second transistor. The voltage divider circuit has an input terminal and an output terminal, and the input terminal is connected to a control signal. The control electrode of the first transistor is connected to the output terminal, and the input electrode of the first transistor is connected to the power supply voltage. The control electrode of the second transistor is connected to the output electrode of the first transistor, and the input electrode of the second transistor is connected to an input voltage, and the output electrode of the second transistor is connected to the voltage output terminal. By adding a voltage divider circuit to the switch control circuit, the present application can realize that the voltage specification of the control signal in the switch control circuit is adjustable to meet different specification requirements, thereby avoiding the circuit logic disorder caused by the voltage value fluctuation of the control signal. Furthermore, when the switch control circuit is applied to the backlight driving board, the backlight driving board can effectively control the driving backlight module to be turned off, avoiding the problem of flickering of the backlight module. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 is a structural schematic diagram of a switch control circuit provided by the present application;

[0023] Figure 2 is a first circuit structure schematic diagram of a switch control circuit provided in the present application;

[0024] Figure 3 is a second circuit structure schematic diagram of the switch control circuit provided by the present application;

[0025] Figure 4 is a third circuit structure schematic diagram of the switch control circuit provided in the present application;

[0026] Figure 5 is a fourth circuit structure schematic diagram of the switch control circuit provided by the present application;

[0027] Figure 6 It is a structural schematic diagram of the backlight driving board provided in this application. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0029] In the description of the present application, it should be understood that the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first" and "second" etc. may explicitly or implicitly include one or more of the said features, and therefore cannot be understood as limitations on the present application. In addition, it should be noted that, unless otherwise clearly specified and defined, the terms "connected" and "connected" should be understood in a broad sense, for example, it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] The present application provides a switch control circuit and a backlight driving board, which are described in detail below. It should be noted that the description order of the following embodiments is not intended to limit the preferred order of the embodiments of the present application.

[0031] See also Figure 1 , Figure 1 1 is a schematic diagram of the structure of the switch control circuit provided by the present application. In the embodiment of the present application, the switch control circuit 100 includes a voltage divider circuit 10, a first transistor T1 and a second transistor T2.

[0032] The voltage divider circuit 10 has an input terminal A and an output terminal B. The input terminal A is connected to a control signal BL_ON. The control electrode of the first transistor T1 is connected to the output terminal B. The input electrode of the first transistor T1 is connected to a power supply voltage. The control electrode of the second transistor T2 is connected to the output electrode of the first transistor T1. The input electrode of the second transistor T2 is connected to an input voltage V0. The output electrode of the second transistor T2 is connected to the voltage output terminal C.

[0033] The voltage output terminal C is used to output a working voltage VCC to a load connected to the switch control circuit 100 to drive the load to work, which will not be described in detail herein.

[0034] It is understandable that in a switch control circuit without a voltage divider circuit 10, the control signal BL_ON directly controls the opening or closing of the first transistor T1, and further controls the opening or closing of the second transistor T2. When the voltage value of the control signal BL_ON fluctuates due to interference from other circuits and ripples, it is easy to cause confusion in the opening and closing of the first transistor T1, thereby causing logic confusion in the switch control circuit 100, affecting the normal output of the working voltage VCC.

[0035] In the embodiment of the present application, a voltage divider circuit 10 is added to the switch control circuit 100. Since the on-voltage and off-voltage of the control electrode of the first transistor T1 are constant, the voltage value of the control signal BL_ON required when the first transistor T1 is turned off can be adjusted through the voltage dividing principle of the voltage divider circuit 10. Thus, the voltage specification of the control signal BL_ON in the switch control circuit can be adjusted to meet different specification requirements, thereby avoiding circuit logic confusion caused by fluctuations in the voltage value of the control signal BL_ON. When the switch control circuit 100 is applied to the backlight driver board, the backlight driver board can effectively control the drive backlight module to turn off, avoiding the problem of flickering of the backlight module.

[0036] In the embodiment of the present application, each transistor in the switch control circuit 100 may be one or more of a low-temperature polysilicon thin film transistor, an oxide semiconductor thin film transistor or an amorphous silicon thin film transistor.

[0037] The transistors used in the embodiments of the present application may include P-type transistors and / or N-type transistors, wherein the P-type transistor is turned on when the gate is at a low level and is turned off when the gate is at a high level, and the N-type transistor is turned on when the gate is at a high level and is turned off when the gate is at a low level.

[0038] In the embodiment of the present application, the power supply voltage can be a high level voltage or a ground voltage GND. The first transistor T1 can be an N-type transistor or a P-type transistor, and the second transistor T2 can be an N-type transistor or a P-type transistor, which can be specifically set according to the power supply voltage and the voltage value of the input voltage V0.

[0039] It should be noted that the following embodiments of the present application are all described by taking the power supply voltage as the ground voltage GND, the first transistor T1 as an NPN-type transistor, and the second transistor T2 as a PNP-type transistor as an example, but this cannot be understood as a limitation of the present application. When the first transistor T1 is an NPN-type transistor and the second transistor T2 is a PNP-type transistor, the control electrodes of the transistors appearing in the embodiments of the present application are all the base electrodes of the transistors, the input electrodes of the transistors are all the emitters of the transistors, and the output electrodes of the transistors are all the collectors of the transistors.

[0040] When the control signal BL_ON is at a high level, the first transistor T1 is turned on through the voltage dividing effect of the voltage dividing circuit 10, the emitter and collector of the first transistor T1 are turned on, the ground voltage GND is transmitted to the base of the second transistor T2, the base of the second transistor T2 is pulled to a low level, the emitter and collector of the second transistor T2 are turned on, so that the working voltage VCC is output. Normally, the voltage value of the input voltage V0 is equal to the voltage value of the working voltage VCC.

[0041] On the contrary, when the control signal BL_ON is at a low level, the first transistor T1 and the second transistor T2 are both in the cut-off state, and the input voltage V0 cannot be output through the second transistor T2. That is, the switch control circuit 100 cannot output the working voltage VCC to the load.

[0042] See also Figure 2 , Figure 2 1 is a schematic diagram of a first circuit structure of a switch control circuit provided in the present application. In the embodiment of the present application, the voltage divider circuit 10 includes a first voltage divider resistor R1 and a second voltage divider resistor R2.

[0043] One end of the first voltage-dividing resistor R1 is connected to the control signal BL_ON. The other end of the first voltage-dividing resistor R1 and one end of the second voltage-dividing resistor R2 are both connected to the output terminal B. The other end of the second voltage-dividing resistor R2 is connected to the power supply voltage, that is, the ground voltage GND.

[0044] In the embodiment of the present application, a resistor voltage division design is adopted, and the first voltage division resistor R1 and the second voltage division resistor R2 are used for voltage division sampling, then V BL_ON / (R1+R2)=V B / R2, where V BL_ON is the voltage value of the control signal BL_ON, the output terminal B is also the base of the first transistor T1, V B That is, the base voltage of the first transistor T1. If the turn-on voltage of the first transistor T1 is 0.7V, then V B =0.7V, V BL_ON =(1+R1 / R2)*0.7V. Therefore, the voltage specification of the control signal BL_ON can be adjusted by adjusting the resistance values ​​of the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2.

[0045] For example, when the first voltage-dividing resistor R1 is 10 kΩ and the second voltage-dividing resistor R2 is 20 kΩ, V BL_ON =1.05V, that is, the voltage value of the control signal BL_ON needs to reach 1.05V to turn on the first transistor T1. Even if the actual voltage value of the control signal BL_ON fluctuates between 0 and 1V due to interference from other circuits and ripples, the first transistor T1 cannot be turned on, and there will be no circuit logic disorder.

[0046] In some embodiments of the present application, at least one of the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2 is a variable resistor.

[0047] It is understandable that when the type of the first transistor T1 is different, the turn-on voltage of the first transistor T1 may be different. And when the switch control circuit 100 is applied to different chips or circuit boards, the interference to the control signal BL_ON may also be different. Therefore, by adjusting the resistance value of at least one of the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2, the required voltage value of the control signal BL_ON can be adjusted to avoid circuit logic disorder.

[0048] Specifically, the voltage divider circuit 10 can be designed to reserve positions and routings for welding the first voltage divider resistor R1 and the second voltage divider resistor R2, so as to weld resistors of corresponding specifications as required. In addition, the resistors can be replaced according to the application scenario of the switch control circuit 100 to adjust the resistance value of each resistor, which is very convenient and simple to operate.

[0049] Of course, in other embodiments of the present application, at least one of the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2 may be set as a sliding variable resistor to change the resistance value of the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2, which will not be repeated here.

[0050] Optionally, in some embodiments of the present application, the switch control circuit 100 further includes a capacitor C, and one plate of the capacitor C is connected to the output terminal B. The other plate of the capacitor C is connected to the power supply voltage, that is, connected to the ground voltage GND.

[0051] In some embodiments of the present application, the switch control circuit 100 further includes a first voltage-stabilizing resistor R0 and a second voltage-stabilizing resistor R3. One end of the first voltage-stabilizing resistor R0 is connected to the input voltage V0. The other end of the first voltage-stabilizing resistor R0 and one end of the second voltage-stabilizing resistor R3 are both connected to the control electrode of the second transistor T2. The other end of the second voltage-stabilizing resistor R3 is connected to the output electrode of the first transistor T1.

[0052] Among them, when the first transistor T1 is turned off, the input voltage V0 connected to the input electrode of the second transistor T2 may already be at a high potential. Then the second transistor T2 may be mistakenly turned on. Therefore, by setting the first voltage-stabilizing resistor R0, the embodiment of the present application can make the emitter and base of the second transistor T2 at a certain potential, that is, the same high and low. When the first transistor T1 is turned off, the second transistor T2 can be prevented from being mistakenly turned on due to the voltage difference between the emitter and the base of the second transistor T2.

[0053] In addition, when the first transistor T1 is turned on, a loop is formed between the input voltage V0, the first voltage-stabilizing resistor R0, the second voltage-stabilizing resistor R3, the first transistor T1, and the ground voltage GND. By controlling the resistance values ​​of the first voltage-stabilizing resistor R0 and the second voltage-stabilizing resistor R3, the voltage difference between the emitter and the base of the second transistor T2 can be controlled, thereby controlling the second transistor T2 to turn on, and realizing the normal output of the working voltage VCC.

[0054] In some embodiments of the present application, the switch control circuit 100 may further include a current limiting resistor R4, wherein one end of the current limiting resistor R4 is connected to the output electrode of the second transistor T2, and the other end of the current limiting resistor R4 is connected to the voltage output terminal C.

[0055] In the embodiment of the present application, the current limiting resistor R4 plays a role of current limiting in the switch control circuit 100 to prevent the output current of the switch control circuit 100 from being too large and burning the load connected to the voltage output terminal C. Among them, the current limiting resistor R4 does not play a role of voltage division, that is, in an ideal case, the voltage value of the input voltage V0 is equal to the voltage value of the working voltage VCC. The resistance value of the current limiting resistor R4 can be designed according to actual needs, and this application does not make specific restrictions on this.

[0056] See also Figure 3 , Figure 3 is a second circuit structure diagram of the switch control circuit provided by the present application. Figure 2 The difference of the switch control circuit 100 shown is that in the embodiment of the present application, the voltage divider circuit 10 includes at least one diode D. The anode of the diode D is connected to the control signal BL_ON. The cathode of the diode D is connected to the output terminal B.

[0057] It is understandable that the diode D has a turn-on voltage. Therefore, the diode D is provided in the voltage divider circuit 10, that is, the diode D is connected in series between the control signal BL_ON and the control electrode of the first transistor T1 to play a voltage divider role. Also, taking the turn-on voltage of the first transistor T1 as 0.7 as an example, V BL_ON =V B +0.7=1.4V. That is, the voltage value of the control signal BL_ON needs to reach 1.4V to turn on the first transistor T1. Even if the actual voltage value of the control signal BL_ON fluctuates between 0 and 1V due to interference from other circuits and ripples, the first transistor T1 cannot be turned on, and there will be no circuit logic disorder.

[0058] When the voltage divider circuit 10 includes two or more diodes D, the two or more diodes D are connected in series, so that the voltage input specification of the control signal BL_ON can be further adjusted.

[0059] For further information, see Figure 4 , Figure 4 is a third circuit structure diagram of the switch control circuit provided in the present application. Figure 3 The difference of the switch control circuit 100 shown is that, in some embodiments of the present application, the voltage divider circuit 10 further includes a short-circuit resistor R6. One end of the short-circuit resistor R6 is connected to the control signal BL_ON. The other end of the short-circuit resistor R6 is connected to the output terminal B, and the resistance of the short-circuit resistor R6 is zero.

[0060] It is understandable that a resistor welding site can be reserved in the voltage divider circuit 10. When the actual voltage value of the control signal BL_ON is within a small fluctuation range, a short-circuit resistor R6 can be welded in the voltage divider circuit 10. At this time, the short-circuit resistor R6 short-circuits the diode D, and the diode D no longer plays a role in voltage division. Similarly, taking the turn-on voltage of the first transistor T1 as 0.7 as an example, V BL_ON =0.7V, the specification of the control signal BL_ON can be adjusted to be less than 0.7V.

[0061] Of course, in some embodiments of the present application, only the short-circuit resistor R6 may be installed in the switch control circuit 100 without the diode D. For details, please refer to Figure 5 , Figure 5 is a fourth circuit structure diagram of the switch control circuit provided in the present application. Figure 4 The switch control circuit 100 shown is different in that the voltage divider circuit 10 only includes a short-circuit resistor R6.

[0062] It is understandable that if, according to demand, when the first transistor T1 is turned off, the voltage specification of the control signal BL_ON only requires 0-0.6V, then only the short-circuit resistor R6 may be installed without the diode D, thereby reducing production costs.

[0063] Accordingly, see Figure 6 , Figure 6 1 is a schematic diagram of the structure of the backlight driving board provided by the present application. In the embodiment of the present application, the backlight driving board 1000 includes the switch control circuit 100 described in any of the above embodiments. Figure 1-Figure 5 The above embodiments will not be described in detail here.

[0064] The backlight driving board 1000 further includes a power pin P1, a ground pin P2 and a control pin P3. The power pin P1 is connected to the input voltage V0. The ground pin P2 is connected to the ground voltage GND. The control pin P3 is connected to the control signal BL_ON.

[0065] The input end of the voltage divider circuit 10 is connected to the control pin P3. The input electrode of the first transistor T1 is connected to the ground pin P2. The input electrode of the second transistor T2 is connected to the power pin p1. The backlight driving board 1000 controls the opening or closing of the backlight module lamp tube under the control of the external input voltage V0, the ground voltage GND, the control signal BL_ON and the switch control circuit 100.

[0066] In addition, other pins of the backlight driver board 1000 can also be connected to the light control signal P_DIM signal to control the light duration of the backlight module lamp tube, which is a technology well known to those skilled in the art and will not be described in detail here. The backlight driver board 1000 also has some pins that are not connected to signals, such as the pin NC, which will not be described in detail here.

[0067] The backlight driving board 1000 provided in the embodiment of the present application includes a switch control circuit 100, in which a voltage divider circuit 10 is added. Since the on-voltage or off-voltage of the control electrode of the first transistor T1 is constant, the voltage value of the control signal BL_ON required when the first transistor T1 is turned off can be adjusted through the voltage dividing principle of the voltage divider circuit 10. Thus, the voltage input specification of the control signal BL_ON in the switch control circuit can be adjusted to meet different specification requirements, avoid circuit logic confusion caused by fluctuations in the control signal BL_ON, so that the backlight driving board 1000 can effectively control the driving backlight module to turn off, and avoid the problem of flickering of the backlight module.

[0068] The above is a detailed introduction to the light-emitting control circuit and the backlight circuit board provided in the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A switch control circuit, characterized in that: include: A voltage divider circuit, the voltage divider circuit having an input end and an output end, the input end receiving a control signal; a first transistor, wherein a control electrode of the first transistor is connected to the output terminal, and an input electrode of the first transistor is connected to a power supply voltage; as well as a second transistor, wherein a control electrode of the second transistor is connected to an output electrode of the first transistor, an input electrode of the second transistor is connected to an input voltage, and an output electrode of the second transistor is connected to a voltage output terminal; Wherein, the voltage divider circuit also includes at least one diode, a reserved resistor welding site and a short-circuit resistor. The turn-on voltage of the first transistor is 0.7V. When the voltage specification of the control signal is less than 0.7V, that is, when there is no voltage greater than or equal to 0.7V in the actual voltage value of the control signal, one end of the short-circuit resistor is connected to the reserved resistor welding site to access the control signal, and the other end of the short-circuit resistor is connected to the output end. The resistance of the short-circuit resistor is zero. When the voltage specification of the control signal is not less than 0.7V, the positive electrode of the diode is connected to the control signal, the negative electrode of the diode is connected to the output end, and the short-circuit resistor is not connected to the reserved resistor welding site.

2. The switch control circuit according to claim 1, characterized in that: The switch control circuit further comprises a capacitor, one plate of the capacitor is connected to the output end, and the other plate of the capacitor is connected to the power supply voltage.

3. The switch control circuit according to claim 1, characterized in that: The switch control circuit also includes a first stabilizing resistor and a second stabilizing resistor, one end of the first stabilizing resistor is connected to the input voltage, the other end of the first stabilizing resistor and one end of the second stabilizing resistor are both connected to the control electrode of the second transistor, and the other end of the second stabilizing resistor is connected to the output electrode of the first transistor.

4. The switch control circuit according to claim 1, characterized in that: The switch control circuit also includes a current limiting resistor; One end of the current limiting resistor is connected to the output electrode of the second transistor, and the other end of the current limiting resistor is connected to the voltage output end.

5. The switch control circuit according to claim 1, characterized in that: The first transistor is an NPN transistor, the second transistor is a PNP transistor, and the power supply voltage is a ground voltage.

6. A backlight driving board, characterized in that: Comprising the switch control circuit as described in any one of claims 1-5, the backlight driving board also includes a power pin, a ground pin and a control pin, the power pin is connected to the input voltage, the ground pin is connected to the power supply voltage, and the control pin is connected to the control signal.

Images