CN219085632U - Backlight driving circuit with adjustable dimming mode - Google Patents
Backlight driving circuit with adjustable dimming mode Download PDFInfo
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- CN219085632U CN219085632U CN202222805246.9U CN202222805246U CN219085632U CN 219085632 U CN219085632 U CN 219085632U CN 202222805246 U CN202222805246 U CN 202222805246U CN 219085632 U CN219085632 U CN 219085632U
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Abstract
The utility model discloses a backlight driving circuit with an adjustable dimming mode, which comprises a rectifying circuit, a DC/DC converter, a dimming conversion circuit, a dimming circuit and a control loop, wherein the rectifying circuit is connected with the DC/DC converter; the rectification circuit is connected with the DC/DC converter; the output end of the DC/DC converter is connected with a backlight plate load; the sampling end of the dimming conversion circuit is connected with the output end of the DC/DC converter; the control input end of the dimming circuit is connected with the control output end of the dimming conversion circuit; the dimming circuit comprises a PWM dimming circuit and a voltage dimming circuit; the input end of the control loop is connected with the output end of the DC/DC converter and the output end of the dimming circuit, and the output end of the control loop is connected with the control end of the DC/DC converter. The backlight module not only can adjust the backlight plate when the load brightness requirements of the backlight plate are different, but also can adjust the dimming mode, so that the dimming precision of the circuit is higher and the universality is wider.
Description
Technical Field
The utility model relates to a backlight driving circuit with an adjustable dimming mode.
Background
At present, a traditional liquid crystal screen is provided with an LED backlight, but the common liquid crystal screen backlight only supports unified adjustment, and cannot adjust the brightness of a certain area independently. Even a small portion of the lcd screen supports backlight partition adjustment, the number of backlight partitions is very limited. Unlike conventional LCD screen backlights, the Mini LED technology can make the LED backlight beads very small, so that more backlight beads can be integrated on the same screen, and finer backlight partitions can be divided, which is also an important difference between the Mini LED technology and the conventional LCD screen. With the help of Mini LEDs, the screen is provided with a plurality of backlight partitions, the brightness of a small area of the screen can be independently controlled, the bright place is enough bright, the dark place is enough dark, and the limitation of the picture expressive force is less. When a certain part of the picture needs to be displayed in black, the small backlight partition of the part can be dimmed or even turned off to obtain purer black, which is not realized by a common liquid crystal screen. The screen adopting Mini LED technology has the advantages of long service life, difficult screen burning and the like. After the measurement, the cost is lower than that of an organic light-emitting diode screen.
In the field of medium and high power illumination, the application scenes of the light emitting diode are continuously abundant, and the dimming function of the light emitting diode can not only meet the energy saving requirement in the common illumination scene, but also ensure the realization of specific brightness in the special illumination scene. The common dimming modes include output chopper dimming, voltage dimming and PWM dimming. The output chopper dimming utilizes a high-frequency signal to enable the LED to rapidly conduct on-off actions within a certain time, at the moment, the LED always works between the maximum current output by the driving power supply and 0, and dimming can be achieved by changing the on-off time of the LED; the voltage dimming is to change the feedback value of the driving power supply through a voltage signal, so as to change the output current of the driving power supply; PWM dimming is the same as the dimming signal used for output chopper dimming, and the dimming process is similar to the operation of voltage dimming. However, most of the dimming schemes in the existing driving power supply are single, which results in low dimming accuracy and poor universality, for example, chinese patent publication No. CN217562236U discloses an ac input dimmable LED backlight board, in which the ac input dimmable LED backlight board includes a wall manual switch S4, an EMI rectifying and filtering circuit, a transformer T1, a voltage regulating circuit, an LED backlight board, a single-stage PFC converter circuit, an isolation control circuit and a segmented dimming trigger control circuit, so that the dimming circuit has a three-segment segmented cyclic dimming function, and the segmented dimming design can meet the brightness cyclic adjustment requirement of 100%,50% and 20%, but cannot independently control the brightness of a small screen area, and the universality is not wide enough.
Disclosure of Invention
The utility model aims to overcome the defects of the prior art and provide the backlight driving circuit with the adjustable dimming mode, which not only can adjust the load brightness requirement of the backlight when the load brightness requirement is different, but also can adjust the dimming mode, so that the dimming precision of the circuit is higher and the universality is wider.
In order to solve the technical problems, the technical scheme of the utility model is as follows: a backlight driving circuit with an adjustable dimming mode comprises a rectifying circuit, a DC/DC converter, a dimming conversion circuit, a dimming circuit and a control loop; wherein, the liquid crystal display device comprises a liquid crystal display device,
the rectification circuit is connected with the DC/DC converter;
the output end of the DC/DC converter is connected with the backlight plate load;
the sampling end of the dimming conversion circuit is connected with the output end of the DC/DC converter;
the control input end of the dimming circuit is connected with the control output end of the dimming conversion circuit;
the dimming circuit comprises a PWM dimming circuit and a voltage dimming circuit;
the input end of the control loop is connected with the output end of the DC/DC converter and the output end of the dimming circuit, and the output end of the control loop is connected with the control end of the DC/DC converter;
the dimming conversion circuit is suitable for sampling a current signal and a voltage signal output by the DC/DC converter and outputting a dimming signal according to the sampled current signal and voltage signal;
the PWM dimming circuit or the voltage dimming circuit in the dimming circuit is suitable for selecting action according to the received dimming signal;
the control loop is suitable for controlling the action of the DC/DC converter according to the voltage signal output by the dimming circuit and the current signal output by the rectifying circuit.
Further, the rectification circuit is a front-stage uncontrolled rectification circuit.
Further, the DC/DC converter is a post-stage DC/DC asymmetric half-bridge circuit.
Further, in order to prevent the output voltage from exceeding a set voltage value and damaging a circuit, an output overvoltage protection circuit is further connected between the output end of the DC/DC converter and the backlight load.
Further, in order to provide the required power supply voltage for the control chip of the control loop, the control chip of the dimming circuit, the dimming circuit and other auxiliary circuits, so that the circuit can stably run, the backlight driving circuit further comprises an auxiliary power circuit, the auxiliary power circuit is connected with the output end of the rectifying circuit, and the power supply output end of the auxiliary power circuit is respectively connected with the power supply input ends of the control loop and/or the dimming circuit and/or the dimming conversion circuit.
Further, the auxiliary power supply circuit is adapted to output an auxiliary power supply voltage of a first voltage value and an auxiliary power supply voltage of a second voltage value.
Further, the first voltage value is 15V, and the second voltage value is 5V.
Further, the control loop includes a control chip L6591.
After the technical scheme is adopted, in the utility model, alternating current is changed into direct current through the rectifying circuit, the direct current supplies power to the backlight plate load through the DC/DC converter, the DC/DC converter is controlled through detection of the output current of the DC/DC converter and the voltage signal of the dimming circuit by the control loop, the brightness of the backlight plate load is regulated through the dimming conversion circuit and the dimming circuit in the middle, and the dimming conversion circuit determines that the dimming circuit adopts the PWM dimming circuit or the voltage dimming circuit according to the sampled output voltage signal; wherein the dimming circuit is divided into a PWM dimming circuit and a voltage dimming circuit, the PWM dimming circuit changing brightness by changing a pulse width of a load flowing through the backlight panel; the voltage dimming circuit changes the current flowing through the backlight plate load by adjusting the power supply voltage of the backlight plate load, and finally achieves the purpose of changing the brightness of the backlight plate load.
The utility model has the following beneficial effects:
1. the backlight plate driving circuit has PWM dimming and voltage dimming conversion functions, so that the dimming accuracy of the circuit is higher and the universality is wider.
2. The backlight driving circuit comprises a rear-stage DC/DC asymmetric half-bridge circuit, so that the whole circuit structure and control are simpler, and soft switching is easier to realize.
3. The circuit design scheme has an output overvoltage protection circuit and has higher safety.
Drawings
FIG. 1 is a circuit diagram of a backlight driving circuit with adjustable dimming mode according to the present utility model;
FIG. 2 is a circuit diagram of an auxiliary power circuit of the present utility model;
FIG. 3 is a circuit diagram of a rectifying circuit according to the present utility model;
fig. 4 is a circuit diagram of the DC/DC converter of the present utility model;
FIG. 5 is a circuit diagram of a PWM dimming circuit of the present utility model;
FIG. 6 is a circuit diagram of a voltage dimming circuit of the present utility model;
FIG. 7 is a circuit diagram of a dimming conversion circuit according to the present utility model;
fig. 8 is a circuit diagram of an output overvoltage protection circuit of the present utility model.
Detailed Description
In order that the utility model may be more readily understood, a more particular description of the utility model will be rendered by reference to specific embodiments that are illustrated in the appended drawings.
As shown in fig. 1 to 8, a backlight driving circuit with an adjustable dimming mode includes a rectifying circuit 1, a DC/DC converter 2, a dimming conversion circuit 3, a dimming circuit 4 and a control loop 5; wherein, the liquid crystal display device comprises a liquid crystal display device,
the rectifying circuit 1 is connected with the DC/DC converter 2;
the output end of the DC/DC converter 2 is connected with a backlight plate load 6;
the sampling end of the dimming conversion circuit 3 is connected with the output end of the DC/DC converter 2;
the control input end of the dimming circuit 4 is connected with the control output end of the dimming conversion circuit 3;
the dimming circuit 4 includes a PWM dimming circuit 41 and a voltage dimming circuit 42;
the input end of the control loop 5 is connected with the output end of the DC/DC converter 2 and the output end of the dimming circuit 4, and the output end of the control loop 5 is connected with the control end of the DC/DC converter 2;
the dimming conversion circuit 3 is adapted to sample the current signal and the voltage signal output from the DC/DC converter 2, and output a dimming signal according to the sampled current signal and voltage signal;
the PWM dimming circuit 41 or the voltage dimming circuit 42 in the dimming circuit 4 is adapted to select an action according to the received dimming signal;
the control loop 5 is adapted to control the operation of the DC/DC converter 2 based on the voltage signal output by the dimmer circuit 4 and the current signal output by the DC/DC converter 2.
When the circuit works, alternating current is changed into direct current through the rectifying circuit 1, the direct current is used for supplying power to the backlight board load 6 through the DC/DC converter 2, the DC/DC converter 2 is controlled through detection of the output current of the DC/DC converter 2 and the voltage signal of the dimming circuit 4 by the control loop 5, the middle part of the direct current is used for adjusting the brightness of the backlight board load 6 through the dimming conversion circuit 3 and the dimming circuit 4, and the dimming conversion circuit 3 determines that the dimming circuit 4 adopts the PWM dimming circuit 41 or the voltage dimming circuit 42 according to the sampled output voltage signal; wherein the dimming circuit 4 is divided into a PWM dimming circuit 41 and a voltage dimming circuit 42, the PWM dimming circuit 41 changing brightness by changing a pulse width of a pulse flowing through the backlight load 6; the voltage dimming circuit 42 changes the current flowing through the backlight load 6 by adjusting the supply voltage of the backlight load 6, and finally achieves the purpose of changing the brightness thereof.
Specifically, in this embodiment, in the dimming conversion circuit 3, as shown in fig. 7, the dimming signal may be controlled by the HT66F019 control chip, the HT66F019 control chip may also sample the output current signal, and then the program of burning controls the output of the dimming signal, and the program of burning is the prior art, which will not be described again. Because the higher the brightness of Mini LED lamp beads of the backlight plate is, the higher the voltage born by the Mini LED lamp beads is, so the dimming conversion circuit 3 decides whether the dimming circuit 4 adopts PWM dimming or voltage dimming according to sampled output voltage signals, the specific voltage reference can be changed according to the number and the size of the Mini LED lamp beads, in the embodiment, the diodes D11 and D12 can limit the input signals through a serial connection method, the voltage reference can be set by the voltage division of a resistor R16 and a resistor R17 according to the number and the size of the Mini LED lamp beads which are specifically controlled, the dimming conversion circuit 3 samples the output voltage, compares the output voltage with the set voltage reference, the same phase end of the comparator U2A is the sampled output voltage, the opposite phase end of the comparator U2B is the voltage reference, when the output voltage is larger than the voltage reference, the comparator U2A outputs a high level, the comparator U2B outputs a low level at the moment, the MOS transistor Q5 is turned off, the MOS transistor Q6 is turned off, the normally open switch RY1 is turned off, and the normally open switch U2 is not turned on, and the dimming circuit 41 is turned on; when the output voltage is smaller than the voltage reference, the MOS transistor Q6 is turned on, the MOS transistor Q5 is turned off, the normally open switch RY2 is turned off, the normally open switch RY1 is not turned on, and the dimming circuit 4 is the voltage dimming circuit 42.
Specifically, as shown in fig. 5 to 6, the dimming circuit 4 includes two parts, one part is a PWM dimming circuit 41, and since each LED is a diode, fast switching can be achieved, and thus the brightness of the LED can be changed by changing the pulse width of the LED; the other part is a voltage dimming circuit 42, which is characterized in that the power supply voltage of an LED lamp is regulated, the voltage of the LED is changed, so that the current flowing through the LED lamp is changed, the brightness of the LED lamp is finally changed, a dimming signal of a PWM dimming circuit 41 is sent out by an HT66F019 control chip, firstly, the dimming signal is sent to a MOS tube Q4 through a normally open relay switch controlled by a dimming conversion circuit 3, the voltage regulating signal controls the switch of the MOS tube Q4, namely, a signal source with the same frequency as the dimming signal is generated at two ends of a resistor R5, a square wave signal is input into a U1A from the upper end point of the resistor R5, the signal transmission of the dimming circuit is more accurate, then the square wave signal is sent to a control loop 5 of a DC/DC converter 2 after being isolated by a voltage follower U1B; the dimming signal of the voltage dimming circuit 42 is also sent by the HT66F019 control chip, and is sent to the control loop 5 of the DC/DC converter 2 after passing through the normally open relay switch controlled by the dimming conversion circuit 3 to the voltage follower U1C and then comparing with the output voltage sample.
Specifically, the rectifying circuit 1 may be a front-stage uncontrolled rectifying circuit, as shown in fig. 3, where the front-stage uncontrolled rectifying circuit may be a rectifying circuit composed of a rectifying diode D2, a rectifying diode D3, a rectifying diode D4, and a rectifying diode D5 without control function, and after the alternating current passes through the rectifying circuit 1, a direct current is output, and when the input alternating current voltage is fixed, the obtained direct current voltage cannot be adjusted.
Specifically, as shown in fig. 4, the control loop 5 may include a control chip L6591.
Specifically, as shown in fig. 4, the DC/DC converter 2 may be a post-stage DC/DC asymmetric half-bridge circuit, the primary side of the transformer of the post-stage DC/DC asymmetric half-bridge circuit may be composed of a controllable switch network and a resonant network, and may specifically include two MOS transistors, namely, MOS transistor Q2 and MOS transistor Q3, an isolation capacitor C10, an inductor L2, and an inductor L3, the duty ratios of the MOS transistor Q2 and the MOS transistor Q3 are complementary, the secondary side may be a basic full-bridge circuit composed of four diodes, diode D6, diode D7, diode D8, and diode D9, and the whole circuit may be a circuit controlled by detecting a current signal output by the DC/DC converter 2 and a voltage signal of the dimming circuit 4 by the control chip L6591.
Specifically, as shown in fig. 8, in order to prevent the output voltage from exceeding the set voltage value and damaging the circuit, an output overvoltage protection circuit 7 may be connected between the output end of the DC/DC converter 2 and the backlight load 6, and when the output voltage exceeds the set voltage value of the voltage stabilizing tube D15, that is, the overvoltage protection is triggered, the MOS tube Q7 is turned off, so that the whole circuit is disconnected, and the circuit no longer supplies power to the backlight load 6.
Specifically, as shown in fig. 5 to 7, in order to provide a required supply voltage for a control chip of the control loop 5, a control chip of the dimming circuit 4, and other auxiliary circuits such as the dimming circuit 4, so as to facilitate stable operation of the circuit, the auxiliary power supply circuit 8 may also be included, the auxiliary power supply circuit 8 may be connected to an output end of the rectifying circuit 1, and a power supply output end of the auxiliary power supply circuit 8 may be connected to power supply input ends of the control loop 5, the dimming circuit 4, and the dimming conversion circuit 3, respectively.
Specifically, the auxiliary power supply circuit 8 may be adapted to output an auxiliary power supply voltage of a first voltage value and an auxiliary power supply voltage of a second voltage value.
Specifically, the first voltage value may be 15V, and the second voltage value may be 5V, as shown in fig. 2, where coupling between the secondary winding W2 of the auxiliary power circuit 8 and the primary winding W1 of the transformer generates an auxiliary power voltage of 15V; the 15V voltage outputs an auxiliary power supply voltage of 5V through the 78M05 chip.
The technical problems, technical solutions and advantageous effects solved by the present utility model have been further described in detail in the above-described embodiments, and it should be understood that the above-described embodiments are only illustrative of the present utility model and are not intended to limit the present utility model, and any modifications, equivalent substitutions, improvements, etc. within the spirit and principle of the present utility model should be included in the scope of protection of the present utility model.
Claims (8)
1. The backlight driving circuit with the adjustable dimming mode is characterized by comprising a rectifying circuit (1), a DC/DC converter (2), a dimming conversion circuit (3), a dimming circuit (4) and a control loop (5); wherein, the liquid crystal display device comprises a liquid crystal display device,
the rectification circuit (1) is connected with the DC/DC converter (2);
the output end of the DC/DC converter (2) is connected with a backlight plate load (6);
the sampling end of the dimming conversion circuit (3) is connected with the output end of the DC/DC converter (2);
the control input end of the dimming circuit (4) is connected with the control output end of the dimming conversion circuit (3);
the dimming circuit (4) comprises a PWM dimming circuit (41) and a voltage dimming circuit (42);
the input end of the control loop (5) is connected with the output end of the DC/DC converter (2) and the output end of the dimming circuit (4), and the output end of the control loop (5) is connected with the control end of the DC/DC converter (2);
the dimming conversion circuit (3) is suitable for sampling a current signal and a voltage signal output by the DC/DC converter (2) and outputting a dimming signal according to the sampled current signal and voltage signal;
-the PWM dimming circuit (41) or the voltage dimming circuit (42) of the dimming circuit (4) is adapted to select an action according to a received dimming signal;
the control loop (5) is adapted to control the operation of the DC/DC converter (2) in dependence of the voltage signal output by the dimmer circuit (4) and the current signal output by the DC/DC converter (2).
2. The backlight driving circuit with adjustable dimming mode as claimed in claim 1, wherein,
the rectification circuit (1) is a front-stage uncontrolled rectification circuit.
3. The backlight driving circuit with adjustable dimming mode as claimed in claim 1, wherein,
the DC/DC converter (2) is a post-stage DC/DC asymmetric half-bridge circuit.
4. The backlight driving circuit with adjustable dimming mode as claimed in claim 1, wherein,
an output overvoltage protection circuit (7) is further connected between the output end of the DC/DC converter (2) and the backlight plate load (6).
5. The backlight driving circuit with adjustable dimming mode as claimed in claim 1, wherein,
the power supply circuit further comprises an auxiliary power supply circuit (8), the auxiliary power supply circuit (8) is connected with the output end of the rectifying circuit (1), and the power supply output end of the auxiliary power supply circuit (8) is respectively connected with the control loop (5) and/or the dimming circuit (4) and/or the power supply input end of the dimming conversion circuit (3).
6. The backlight driving circuit with adjustable dimming mode as claimed in claim 5, wherein,
the auxiliary power supply circuit (8) is adapted to output an auxiliary power supply voltage of a first voltage value and an auxiliary power supply voltage of a second voltage value.
7. The backlight driving circuit with adjustable dimming mode as claimed in claim 6, wherein,
the first voltage value is 15V, and the second voltage value is 5V.
8. The backlight driving circuit with adjustable dimming mode as claimed in claim 1, wherein,
the control loop (5) comprises a control chip L6591.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202222805246.9U CN219085632U (en) | 2022-10-25 | 2022-10-25 | Backlight driving circuit with adjustable dimming mode |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202222805246.9U CN219085632U (en) | 2022-10-25 | 2022-10-25 | Backlight driving circuit with adjustable dimming mode |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN219085632U true CN219085632U (en) | 2023-05-26 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202222805246.9U Active CN219085632U (en) | 2022-10-25 | 2022-10-25 | Backlight driving circuit with adjustable dimming mode |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN219085632U (en) |
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2022
- 2022-10-25 CN CN202222805246.9U patent/CN219085632U/en active Active
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