CN211906916U - Backlight driving circuit and display device - Google Patents
Backlight driving circuit and display device Download PDFInfo
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- CN211906916U CN211906916U CN202020752508.8U CN202020752508U CN211906916U CN 211906916 U CN211906916 U CN 211906916U CN 202020752508 U CN202020752508 U CN 202020752508U CN 211906916 U CN211906916 U CN 211906916U
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Abstract
The utility model discloses a drive circuit and display device are shaded, drive circuit is shaded includes voltage conversion circuit and feedback circuit, voltage conversion circuit is used for exporting the voltage conversion back of input from first output and second output, the DC voltage of first output and second output different grade, feedback circuit is used for sending feedback signal to voltage conversion circuit when the output voltage of the first output of voltage conversion circuit is greater than the settlement voltage, with the output voltage of the first output of improvement voltage conversion circuit and voltage conversion circuit's second output, and then, when changing or increasing the backlight and leading to needs increase backlight voltage, need not to change the transformer, can adapt to the operating voltage demand of various backlights automatically, the compatibility of drive circuit is shaded has been improved, be favorable to standardized promotion.
Description
Technical Field
The utility model relates to a drive technical field in a poor light especially relates to a drive circuit and display device are shaded.
Background
With the continuous popularization of smart televisions (e.g., liquid crystal flat panel televisions), the size of the liquid crystal flat panel television is larger and larger, e.g., the size of a common liquid crystal flat panel television is 32 inches, 43 inches, 49 inches, and the like, so that the power of a television mainboard is larger and larger, and meanwhile, with the increasing functions of intelligent application software, the power supply part of the liquid crystal flat panel television has higher requirements.
In the existing backlight driving technology, different output ends of a multi-output transformer in a power circuit respectively increase the voltage of a television main board and the backlight voltage of a backlight LED. However, if the parameters of the backlight module need to be changed in the development process, for example, the backlight voltage needs to be increased in order to adapt to a new backlight LED lamp, the transformer may need to be replaced at this time. Therefore, the existing backlight driving technology has low compatibility, different backlight parameters need to be replaced by different transformers, the product types are increased, and the standardization is not facilitated.
SUMMERY OF THE UTILITY MODEL
The embodiment of the utility model provides a drive circuit is shaded from sun can adapt to the operating voltage demand of various backlights automatically, has improved drive circuit's compatibility is shaded from sun.
In a first aspect, an embodiment of the present invention provides a backlight driving circuit, including: a voltage conversion circuit and a feedback circuit;
the voltage conversion circuit comprises a feedback control end, an input end, a first output end and a second output end, the voltage conversion circuit is used for converting the voltage of the input end and then outputting the converted voltage from the first output end and the second output end, and the first output end and the second output end output direct-current voltages of different grades;
the first input end of the feedback circuit is connected with the first output end of the voltage conversion circuit, the second input end of the feedback circuit is connected with the second output end of the voltage conversion circuit, and the output end of the feedback circuit is connected with the feedback control end of the voltage conversion circuit;
the feedback circuit is used for sending a feedback signal to the voltage conversion circuit when the output voltage of the first output end of the voltage conversion circuit is greater than a set voltage so as to improve the output voltage of the first output end of the voltage conversion circuit and the second output end of the voltage conversion circuit.
Optionally, the feedback circuit includes a comparison unit and a feedback output unit;
the input end of the comparison unit is connected with the first output end of the voltage conversion circuit, and the output end of the comparison unit is connected with the control end of the feedback output unit;
the input end of the feedback output unit is connected with the second output end of the voltage conversion circuit, and the output end of the feedback output unit is connected with the feedback control end of the voltage conversion circuit;
the comparison unit is used for comparing the output voltage of the first output end of the voltage conversion circuit with a set voltage, and sending a control signal to the feedback output unit when the output voltage of the first output end of the voltage conversion circuit is determined to be greater than the set voltage, so that the feedback output unit sends a feedback signal to the voltage conversion circuit.
Optionally, the comparison unit includes a zener diode and a first resistor;
the first end of the first resistor is connected with the first output end of the voltage conversion circuit, and the second end of the first resistor is connected with the anode of the voltage stabilizing diode;
and the cathode of the voltage stabilizing diode is connected with the control end of the feedback output unit.
Optionally, the comparison unit includes a voltage comparator, a second resistor, and a first switching tube;
the input end of the voltage comparator is connected with the first output end of the voltage conversion circuit, the reference end of the voltage comparator is used for inputting reference voltage, and the output end of the voltage comparator is connected with the control end of the first switching tube;
the first end of the first switch tube is connected with the first end of the second resistor, and the second end of the first switch tube is grounded;
and the second end of the second resistor is connected with the control end of the feedback output unit.
Optionally, the feedback output unit includes an optocoupler, a reference voltage chip, a third resistor, and a fourth resistor;
the first end of the primary side of the optical coupler is connected with the second output end of the voltage conversion circuit, the second end of the primary side of the optical coupler is connected with the cathode of the reference voltage chip, and the anode of the reference voltage chip is grounded;
the first end of the secondary side of the optical coupler is connected with the feedback control end of the voltage conversion circuit, and the second end of the secondary side of the optical coupler is grounded;
the first end of the third resistor is connected with the second output end of the voltage conversion circuit, the second end of the third resistor is connected with the first end of the fourth resistor, and the second end of the fourth resistor is grounded;
the reference pole of the reference voltage chip is connected with the first end of the fourth resistor, and the first end of the fourth resistor is also connected with the output end of the comparison unit.
Optionally, the voltage conversion circuit includes a power control chip, a second switching tube, a third switching tube, a transformer, a first rectifying and filtering unit, and a second rectifying and filtering unit;
the transformer comprises a primary winding, a first secondary winding and a second secondary winding;
the primary winding is used for inputting power voltage, and the second switching tube is connected in series in a loop where the primary winding is located;
the control end of the second switching tube is connected with a control signal output pin of the power control chip;
a feedback signal input pin of the power supply control chip is connected with the output end of the feedback circuit;
the first rectifying and filtering unit is connected between the first secondary winding and the first output end of the voltage conversion circuit, the second rectifying and filtering unit is connected between the second secondary winding and the second output end of the voltage conversion circuit, and the third switching tube is connected in a loop of the first rectifying and filtering unit.
Optionally, the first rectifying and filtering unit includes an output control chip, a first diode and a first capacitor;
the anode of the first diode is connected with the first end of the first secondary winding, and the cathode of the first diode is connected with the first end of the third switching tube;
the second end of the third switching tube is grounded;
a control signal output pin of the output control chip is connected with a control end of the third switching tube;
the first end of the first capacitor is grounded, the second end of the first capacitor is connected with the second end of the first secondary winding, and the second end of the first capacitor is used for outputting a first direct-current voltage.
Optionally, the first rectifying and filtering unit further includes a fifth resistor and a sixth resistor;
the first end of the fifth resistor is connected with the second end of the third switching tube, and the second end of the fifth resistor is grounded;
and the first end of the sixth resistor is connected with the first end of the fifth resistor, and the second end of the sixth resistor is connected with a feedback signal input pin of the output control chip.
Optionally, the second rectifying and filtering unit includes a second diode and a second capacitor;
the anode of the second diode is connected with the first end of the second secondary winding, and the cathode of the second diode is used for outputting a second direct-current voltage;
the first end of the second capacitor is connected with the cathode of the second diode, the second end of the second capacitor is connected with the second end of the second secondary winding, and the second end of the second secondary winding is grounded.
In a second aspect, an embodiment of the present invention provides a display device, including a backlight driving circuit, a backlight, and a main board;
the backlight driving circuit includes: a voltage conversion circuit and a feedback circuit;
the voltage conversion circuit comprises a feedback control end, an input end, a first output end and a second output end, and is used for converting the voltage of the input end and then outputting the converted voltage from the first output end and the second output end;
the first output end is connected with the backlight lamp and used for supplying power to the backlight lamp, and the second output end is connected with the mainboard and used for supplying power to the mainboard;
the first input end of the feedback circuit is connected with the first output end of the voltage conversion circuit, the second input end of the feedback circuit is connected with the second output end of the voltage conversion circuit, and the output end of the feedback circuit is connected with the feedback control end of the voltage conversion circuit;
the feedback circuit is used for sending a feedback signal to the voltage conversion circuit when the output voltage of the first output end of the voltage conversion circuit is greater than a set voltage so as to improve the output voltage of the first output end of the voltage conversion circuit and the second output end of the voltage conversion circuit.
The embodiment of the utility model provides a backlight driving circuit, including voltage conversion circuit and feedback circuit, voltage conversion circuit is used for exporting the voltage conversion back of input from first output and second output, the DC voltage of different grades is exported to first output and second output, feedback circuit is used for sending feedback signal to voltage conversion circuit when the output voltage of the first output of voltage conversion circuit is greater than the settlement voltage, with the output voltage of the first output of improving voltage conversion circuit and voltage conversion circuit's second output, and then, when changing or increasing the backlight and leading to needs increase backlight voltage, need not to change the transformer, can adapt to the operating voltage demand of various backlights automatically, backlight driving circuit's compatibility has been improved, be favorable to standardized promotion.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Fig. 1 is a schematic structural diagram of a backlight driving circuit according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of another backlight driving circuit according to an embodiment of the present invention;
fig. 3 is a circuit diagram of a feedback circuit according to an embodiment of the present invention;
fig. 4 is a circuit diagram of another feedback circuit according to an embodiment of the present invention;
fig. 5 is a circuit diagram of a voltage conversion circuit according to an embodiment of the present invention.
Detailed Description
In order to make the technical problems, technical solutions and technical effects achieved by the present invention more clear, the embodiments of the present invention will be described in further detail with reference to the accompanying drawings, and obviously, the described embodiments are only some embodiments, not all embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present invention.
In the description of the present invention, unless expressly stated or limited otherwise, the terms "connected," "connected," and "fixed" are to be construed broadly, e.g., as meaning permanently connected, detachably connected, or integral to one another; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art.
In the present disclosure, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may comprise direct contact between the first and second features, or may comprise contact between the first and second features not directly. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature. Furthermore, the terms "first" and "second" are used merely for descriptive purposes and are not intended to have any special meaning.
An embodiment of the utility model provides a drive circuit is shaded, this embodiment can be adapted to the narrower condition of drive circuit's output voltage's adaptation scope in a poor light, and this drive circuit in a poor light can set up in display device for display device's backlight power supply, wherein, display device can be liquid crystal display devices such as intelligent TV set.
Fig. 1 is a block diagram of a backlight driving circuit according to an embodiment of the present invention, and as shown in fig. 1, the backlight driving circuit includes a voltage converting circuit 100 and a feedback circuit 200.
The voltage conversion circuit 100 includes a feedback control terminal K1, an input terminal K2, a first output terminal K3, and a second output terminal K4. The voltage conversion circuit 100 is configured to convert the voltage of the input terminal K2 and output the converted voltage from the first output terminal K3 and the second output terminal K4, and the first output terminal K3 and the second output terminal K4 output dc voltages of different levels. Exemplarily, in the embodiment of the present invention, the input terminal K2 is used for inputting a high voltage direct current Vbridge, and the high voltage direct current Vbridge is converted from the mains by the rectifier filter circuit. The first output terminal K3 and the second output terminal K4 are respectively used for supplying power to a backlight and a main board of the display device, and the voltage conversion circuit 100 converts the high-voltage direct current Vbridge into a first direct current voltage V1 and a second direct current voltage V2 which are respectively output from the first output terminal K3 and the second output terminal K4 to supply power to the backlight and the main board. Illustratively, the backlight may be an LED or OLED light strip.
The first input terminal of the feedback circuit 200 is connected to the first output terminal K3 of the voltage converting circuit 100, the second input terminal of the feedback circuit 200 is connected to the second output terminal K4 of the voltage converting circuit 100, and the output terminal of the feedback circuit 200 is connected to the feedback control terminal K1 of the voltage converting circuit 100. Illustratively, the feedback circuit 200 draws power from the second output terminal K4 of the voltage converting circuit 100 through the second input terminal to provide the feedback circuit 200 with the voltage required for operation. The feedback circuit 200 collects the output voltage of the first output terminal K3 of the voltage conversion circuit 100 through a first input terminal.
Specifically, the feedback circuit 200 processes the collected output voltage of the first output terminal K3 of the voltage conversion circuit 100, and the processing may be comparing the output voltage of the first output terminal K3 of the voltage conversion circuit 100 with a set voltage, sending a feedback signal to the voltage conversion circuit 100 when the output voltage of the first output terminal K3 of the voltage conversion circuit 100 is greater than the set voltage, and based on the feedback signal, the voltage conversion circuit 100 increases the output voltages of the first output terminal K3 of the voltage conversion circuit 100 and the second output terminal K4 of the voltage conversion circuit 100. Therefore, when the backlight voltage needs to be increased due to replacement or addition of the backlight, the transformer does not need to be replaced, the working voltage requirement of a new backlight can be automatically adapted, the compatibility of a backlight driving circuit is improved, and the standardization is facilitated.
The embodiment of the utility model provides a backlight driving circuit, including voltage conversion circuit and feedback circuit, voltage conversion circuit is used for exporting the voltage conversion back of input from first output and second output, the DC voltage of different grades is exported to first output and second output, feedback circuit is used for sending feedback signal to voltage conversion circuit when the output voltage of the first output of voltage conversion circuit is greater than the settlement voltage, with the output voltage of the first output of improving voltage conversion circuit and voltage conversion circuit's second output, and then, when changing or increasing the backlight and leading to needs increase backlight voltage, need not to change the transformer, can adapt to the operating voltage demand of various backlights automatically, backlight driving circuit's compatibility has been improved, be favorable to standardized promotion.
For better understanding of the embodiments of the present invention, the following description is provided to illustrate the backlight driving circuit according to the present invention with reference to the following embodiments:
fig. 2 is a schematic structural diagram of another backlight driving circuit according to an embodiment of the present invention, and the embodiment further embodies the feedback circuit 200 on the basis of the above embodiment.
Illustratively, as shown in fig. 2, the feedback circuit 200 includes a comparison unit 210 and a feedback output unit 220. The input terminal of the comparing unit 210 is connected to the first output terminal K3 of the voltage converting circuit 100, and the output terminal of the comparing unit 210 is connected to the control terminal of the feedback output unit 220. The input terminal of the feedback output unit 220 is connected to the second output terminal K4 of the voltage converting circuit 100, and the output terminal of the feedback output unit 220 is connected to the feedback control terminal K1 of the voltage converting circuit 100.
Specifically, the comparison unit 210 is configured to collect an output voltage of the first output terminal K3 of the voltage conversion circuit 100, compare the output voltage of the first output terminal K3 of the voltage conversion circuit 100 with a set voltage, and send a control signal to the feedback output unit 220 when it is determined that the output voltage of the first output terminal K3 of the voltage conversion circuit 100 is greater than the set voltage, so that the feedback output unit 220 sends a feedback signal to the voltage conversion circuit 100 to increase the output voltages of the first output terminal K3 of the voltage conversion circuit 100 and the second output terminal K4 of the voltage conversion circuit 100.
Fig. 3 is a circuit diagram of a feedback circuit according to an embodiment of the present invention, which provides an implementation manner of the feedback circuit 200 on the basis of the above embodiment, and describes a specific circuit principle of the feedback circuit 200 in detail.
As shown in fig. 3, the feedback circuit 200 includes a comparison unit 210 and a feedback output unit 220. Specifically, the comparing unit 210 includes a zener diode Z1 and a first resistor R1. A first terminal of the first resistor R1 is connected to the first output terminal K3 of the voltage converting circuit 100, and a second terminal of the first resistor R1 is connected to the anode of the zener diode Z1. The cathode of the zener diode Z1 is connected to the control terminal of the feedback output unit 220.
The feedback output unit 220 includes an optical coupler, a reference voltage chip UB1, a third resistor R13, and a fourth resistor R12. The first end of the primary side PIA of the optical coupler is connected with the second output end K4 of the voltage conversion circuit 100, the second end of the primary side PIA of the optical coupler is connected with the cathode K of the reference voltage chip UB1, and the anode A of the reference voltage chip UB1 is grounded.
The first end of the secondary side PIB of the optical coupler is connected with a feedback control end K1 of the voltage conversion circuit 100, and the second end of the secondary side PIB of the optical coupler is grounded.
A first end of the third resistor R13 is connected to the second output terminal K4 of the voltage converting circuit 100, a second end of the third resistor R13 is connected to a first end of the fourth resistor R12, and a second end of the fourth resistor R12 is grounded.
The reference electrode R of the reference voltage chip UB1 is connected to the first end of the fourth resistor R12, and the first end of the fourth resistor R12 is further connected to the output terminal of the comparison unit 210 (i.e., the cathode of the zener diode Z1). Illustratively, the reference voltage chip UB1 may be an LR431 chip with an internal reference voltage of 2.5V.
For example, as shown in fig. 3, the feedback output unit 220 may further include a resistor R11, a first terminal of the resistor R11 is connected to the second output terminal K4 of the voltage converting circuit 100, and a second terminal of the resistor R11 is connected to the first terminal of the primary side PIA of the optical coupler. The resistor R11 is used as a current-limiting resistor and is used for protecting the primary side PIA of the optocoupler and avoiding damage caused by overlarge current of the primary side PIA of the optocoupler.
Specifically, in the present embodiment, the first output terminal K3 of the voltage conversion circuit 100 is connected to the negative terminal of the backlight, i.e. the ground terminal is used as a reference, and the higher the output voltage (i.e. the backlight voltage) of the first output terminal K3 of the voltage conversion circuit 100 is, the lower the potential (negative potential) of the first output terminal K3 is.
When the backlight voltage is lower than the set voltage, the voltage difference between the two ends of the zener diode Z1 is lower than the reverse breakdown voltage thereof, the zener diode Z1 is in the cut-off state, the feedback signal output by the feedback output circuit 220 is unchanged, and the first output terminal K3 of the voltage conversion circuit 100 is stably output with the current output voltage.
When the backlight voltage is greater than the set voltage, the zener diode Z1 is broken down in the reverse direction, the zener diode Z1 is turned on, since the first output terminal K3 of the voltage conversion circuit 100 is at a negative potential, therefore, at this time, current flows from the third resistor R13, the zener diode Z1 and the first resistor R1 to the first output terminal K3 of the voltage conversion circuit 100 in sequence, which increases the voltage drop of the third resistor R13, and decreases the voltage drop of the fourth resistor R12, namely, the potential of the first end of the fourth resistor R12, namely the reference pole R of the reference voltage chip UB1, is reduced, so that the potential is lower than the reference voltage, the impedance between the anode a and the cathode K of the reference voltage chip UB1 is increased, the current flowing through the primary side PIA of the optical coupler is reduced, the luminance of the primary side PIA of the optical coupler is reduced, the impedance of the secondary side PIB of the optical coupler is increased, the current of the secondary side PIB of the optical coupler is reduced, and the current signal of the secondary side PIB of the optical coupler is the feedback signal. The voltage converting circuit 100 detects the decrease of the current signal, and then increases the output voltages of the first output terminal K3 of the voltage converting circuit 100 and the second output terminal K4 of the voltage converting circuit 100.
Fig. 4 is a circuit diagram of another feedback circuit provided in an embodiment of the present invention, which provides another implementation manner of the feedback circuit 200, and describes a specific circuit principle of the feedback circuit 200 in detail.
As shown in fig. 4, the feedback circuit 200 includes a comparison unit 210 and a feedback output unit 220. Specifically, the comparing unit 210 includes a voltage comparator U2A, a second resistor R2, and a first switch Q1.
An input end 3 of the voltage comparator U2A is connected to the first output end K3 of the voltage conversion circuit 100, a reference end 2 of the voltage comparator U2A is used for inputting a reference voltage Vf (-5V), and an output end 1 of the voltage comparator U2A is connected to a control end of the first switching tube Q1. The power supply voltage input terminal 8 of the voltage comparator U2A is used for inputting 5V dc power, and the ground terminal 4 of the voltage comparator U2A is used for grounding.
A first terminal of the first switch Q1 is connected to a first terminal of the second resistor R2, and a second terminal of the first switch Q1 is grounded. A second terminal of the second resistor R2 is connected to the control terminal of the feedback output unit 220.
For example, as shown in fig. 4, the comparing unit 210 may further include a resistor R3, a resistor R4, a resistor R5, and a capacitor C1. The resistor R3 is used as a protection resistor and is connected in series between the output end of the voltage comparator U2A and the first switching tube Q1. One end of the resistor R4 is connected to the first output terminal K3 of the voltage conversion circuit 100, and the other end is connected to the input terminal 3 of the voltage comparator U2A. One end of the resistor R5 is connected to the input terminal 3 of the voltage comparator U2A, and the other end is grounded. One end of the capacitor C1 is connected with the reference end 2 of the voltage comparator U2A, the other end of the capacitor C1 is grounded, and the capacitor C1 is used for filtering alternating current signals in the reference voltage Vf and improving the stability of the reference voltage Vf.
The specific structure and connection relationship of the feedback output unit 220 are the same as those of the embodiment shown in fig. 3, and the same reference numerals as those of the embodiment described in fig. 3 are used in this embodiment for the convenience of understanding. As shown in fig. 4, the feedback output unit 220 includes an optocoupler, a reference voltage chip UB1, a third resistor R13, and a fourth resistor R12. The first end of the primary side PIA of the optical coupler is connected with the second output end K4 of the voltage conversion circuit 100, the second end of the primary side PIA of the optical coupler is connected with the cathode K of the reference voltage chip UB1, and the anode A of the reference voltage chip UB1 is grounded.
The first end of the secondary side PIB of the optical coupler is connected with a feedback control end K1 of the voltage conversion circuit 100 through a resistor R11, and the second end of the secondary side PIB of the optical coupler is grounded.
A first end of the third resistor R13 is connected to the second output terminal K4 of the voltage converting circuit 100, a second end of the third resistor R13 is connected to a first end of the fourth resistor R12, and a second end of the fourth resistor R12 is grounded.
The reference electrode R of the reference voltage chip UB1 is connected to the first terminal of the fourth resistor R12, and the first terminal of the fourth resistor R12 is further connected to the output terminal of the comparison unit 210 (i.e., the second terminal of the second resistor R2). Illustratively, the reference voltage chip UB1 may be an LR431 chip with an internal reference voltage of 2.5V.
Specifically, in the present embodiment, the first output terminal K3 of the voltage conversion circuit 100 is connected to the negative terminal of the backlight, i.e. the ground terminal is used as a reference, and the higher the output voltage (i.e. the backlight voltage) of the first output terminal K3 of the voltage conversion circuit 100 is, the lower the potential (negative potential) of the first output terminal K3 is.
When the backlight voltage is lower than the set voltage, the potential (negative potential) of the input terminal 3 of the voltage comparator U2A is greater than the potential (-5V) of the reference terminal 2, the voltage comparator U2A outputs no output, the first switch tube Q1 is turned off, the feedback signal output by the feedback output circuit 220 does not change, and the first output terminal K3 of the voltage conversion circuit 100 outputs the current output voltage stably.
When the backlight voltage is greater than the set voltage, the potential (negative potential) of the input terminal 3 of the voltage comparator U2A is lower than the potential (-5V) of the reference terminal 2, and the voltage comparator U2A outputs a control signal to control the first switch tube Q1 to be turned on. For example, the first switch Q1 may be a pmos (positive channel Metal Oxide semiconductor) transistor, and is turned on when the control signal at the control terminal is low. After the first switch tube Q1 is switched on, the second resistor R2 is connected in parallel with the fourth resistor R12, the voltage drop at two ends of the fourth resistor R12 is reduced, namely the first end of the fourth resistor R12, namely the reference pole R potential of the reference voltage chip UB1 is reduced, so that the voltage is lower than the reference voltage, the impedance between the anode a and the cathode K of the reference voltage chip UB1 is increased, the current flowing through the primary side PIA of the optical coupler is reduced, the luminous brightness of the primary side PIA of the optical coupler is reduced, the impedance of the secondary side PIB of the optical coupler is increased, the current of the secondary side PIB of the optical coupler is reduced, and the current signal of the secondary side PIB of the optical coupler is a feedback signal. The voltage converting circuit 100 detects the decrease of the current signal, and then increases the output voltages of the first output terminal K3 of the voltage converting circuit 100 and the second output terminal K4 of the voltage converting circuit 100.
Fig. 5 is a circuit diagram of a voltage converting circuit according to an embodiment of the present invention, and as shown in fig. 5, the voltage converting circuit 100 includes a power control chip U1, a second switch tube Q2, a third switch tube Q3, a transformer T1, a first rectifying and filtering unit 110, and a second rectifying and filtering unit 120.
The transformer T1 may be a multi-output transformer, and includes a primary winding RZ1, a first secondary winding RZ2, and a second secondary winding RZ 3. The primary winding RZ1 is used for inputting the power voltage (i.e. high voltage direct current Vbridge), and the second switching tube Q2 is connected in series to the loop of the primary winding RZ 1. Illustratively, one end of the winding of the primary winding RZ1 is used for inputting the high-voltage direct current Vbridge, the other end of the winding is connected to a first end of a second switching tube Q2, and a second end of the second switching tube Q2 is grounded through a resistor R17.
The control end of the second switch tube Q2 is connected to the control signal output pin of the power control chip U1 for receiving a control signal. Illustratively, the control signal may be a Pulse Width Modulation (PWM) signal for controlling the on-off time of the second switching tube Q2, and thus the voltage of the first secondary winding RZ2 and the second secondary winding RZ 3. For example, by adjusting the duty ratio of the PWM1 signal, the on-time of the second switching tube Q2 is increased to increase the voltages of the first secondary winding RZ2 and the second secondary winding RZ 3.
A feedback signal input pin COMP of the power control chip U1 is connected to an output end of the feedback circuit 200 (i.e., a first end of the secondary side PIB of the optocoupler). The first rectifying and smoothing unit 110 is connected between the first secondary winding RZ2 and the first output terminal K3 of the voltage converting circuit 100, the second rectifying and smoothing unit 120 is connected between the second secondary winding RZ3 and the second output terminal K4 of the voltage converting circuit 100, the third switch tube Q3 is connected in the loop of the first rectifying and smoothing unit 110, and the control terminal of the third switch tube Q3 is used for receiving the pulse width modulation signal PWM 2. After the high-voltage direct current Vbridge is converted by the transformer T1, the high-voltage direct current Vbridge is rectified and filtered by the first rectifying and filtering unit 110 and the second rectifying and filtering unit 120, and then the high-voltage direct current Vbridge is output by the first output end K3 and the second output end K4. By adjusting the duty ratio of the PWM2 signal, the on-off time of the third switching tube Q3 is controlled, and the on-off time of the backlight is controlled, thereby adjusting the brightness of the backlight.
Specifically, when the backlight voltage is lower than the set voltage, the feedback signal output by the feedback output circuit 220 has no change, and the first output terminal K3 of the voltage converting circuit 100 is stably output at the current output voltage.
When the backlight voltage is greater than the set voltage, the power control chip U1 detects that the current of the secondary side PIB of the optical coupler is reduced, the duty ratio of the PWM1 signal is adjusted, and the on-time of the second switching tube Q2 is increased to increase the voltages of the first secondary winding RZ2 and the second secondary winding RZ3, thereby increasing the output voltages of the first output terminal K3 of the voltage conversion circuit 100 and the second output terminal K4 of the voltage conversion circuit 100.
Illustratively, as shown in fig. 5, the first rectifying and filtering unit 110 includes an output control chip U2, a first diode D1, and a first capacitor E1.
An anode of the first diode D1 is connected to the first end of the first secondary winding RZ2, a cathode of the first diode D1 is connected to the first end of the third switching tube Q3, and the second end of the third switching tube Q3 is grounded. A control signal output pin of the output control chip U2 is connected to the control terminal of the third switching tube Q3, and is used for outputting a PWM2 signal. The first end of the first capacitor E1 is grounded, the second end of the first capacitor E2 is connected to the second end of the first secondary winding RZ2, and the second end of the first capacitor E1 is used for outputting a first direct current voltage V1 to power the backlight.
For example, the first rectifying and filtering unit 110 may further include a resistor R14 and a capacitor C2, one end of the resistor R14 is connected to the first end of the third switching tube Q3, the other end of the resistor R14 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected to the second end of the third switching tube Q3.
On the basis of the above embodiment, the first rectifying and filtering unit 110 may further include a fifth resistor R15 and a sixth resistor R16. A first end of the fifth resistor R15 is connected to the second end of the third switching tube Q3, and a second end of the fifth resistor R15 is grounded. The first end of the sixth resistor R16 is connected with the first end of the fifth resistor R15, and the second end of the sixth resistor R16 is connected with the feedback signal input pin of the output control chip U2. The output control chip U2 is used for collecting the voltage across the fifth resistor R15, and adjusting the duty ratio of the PWM2 signal according to the voltage across the fifth resistor R15, controlling the on-off time of the backlight, and further adjusting the backlight brightness.
In the above embodiment, the second rectifying and filtering unit 120 may include the second diode D2 and the second capacitor E2.
The anode of the second diode D2 is connected to the first end of the second secondary winding RZ3, and the cathode of the second diode D2 is used for outputting the second dc voltage V2 for supplying power to the main board. A first terminal of the second capacitor E2 is connected to the cathode of the second diode D2, a second terminal of the second capacitor E2 is connected to a second terminal of the second secondary winding RZ3, and the second terminal of the second secondary winding RZ3 is grounded.
The utility model also provides a display device, it is exemplary, this display device can be liquid crystal display devices such as intelligent TV set. The electronic equipment comprises the backlight driving circuit, the backlight lamp and the main board, wherein the backlight lamp can be an LED or an OLED lamp strip.
The backlight driving circuit includes: a voltage conversion circuit and a feedback circuit;
the voltage conversion circuit comprises a feedback control end, an input end, a first output end and a second output end, and is used for converting the voltage of the input end and then outputting the converted voltage from the first output end and the second output end.
The first output end is connected with the backlight lamp and used for supplying power to the backlight lamp, and the second output end is connected with the mainboard and used for supplying power to the mainboard.
The first input end of the feedback circuit is connected with the first output end of the voltage conversion circuit, the second input end of the feedback circuit is connected with the second output end of the voltage conversion circuit, and the output end of the feedback circuit is connected with the feedback control end of the voltage conversion circuit.
The feedback circuit is used for sending a feedback signal to the voltage conversion circuit when the output voltage of the first output end of the voltage conversion circuit is greater than the set voltage so as to improve the output voltage of the first output end of the voltage conversion circuit and the second output end of the voltage conversion circuit.
Specifically, the specific structure and operation principle of the backlight driving circuit have been described in detail in the above embodiments, and are not described herein again.
The embodiment of the utility model provides a display device, drive circuit is shaded from sun includes voltage conversion circuit and feedback circuit, voltage conversion circuit is used for exporting the voltage conversion back of input from first output and second output, the DC voltage of different grades is exported to first output and second output, feedback circuit is used for sending feedback signal to voltage conversion circuit when the output voltage of the first output of voltage conversion circuit is greater than the settlement voltage, with the output voltage of the first output of improvement voltage conversion circuit and voltage conversion circuit's second output, and then, when changing or increasing the backlight and leading to needs increase backlight voltage, need not to change the transformer, can adapt to the operating voltage demand of various backlights automatically, the compatibility of drive circuit is shaded from sun is improved, be favorable to standardized promotion.
In the description herein, it is to be understood that the terms "upper," "lower," "left," "right," and the like are used in a descriptive sense and with reference to the illustrated orientation or positional relationship for purposes of descriptive convenience and simplicity of operation, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be construed as limiting the present invention.
In the description herein, references to the description of "an embodiment," "an example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be appropriately combined to form other embodiments as will be appreciated by those skilled in the art.
The technical principle of the present invention is described above with reference to specific embodiments. The description is made for the purpose of illustrating the principles of the invention and should not be construed in any way as limiting the scope of the invention. Based on the explanations herein, those skilled in the art will be able to conceive of other embodiments of the present invention without any inventive effort, which would fall within the scope of the present invention.
Claims (10)
1. A backlight driving circuit, comprising: a voltage conversion circuit and a feedback circuit;
the voltage conversion circuit comprises a feedback control end, an input end, a first output end and a second output end, the voltage conversion circuit is used for converting the voltage of the input end and then outputting the converted voltage from the first output end and the second output end, and the first output end and the second output end output direct-current voltages of different grades;
the first input end of the feedback circuit is connected with the first output end of the voltage conversion circuit, the second input end of the feedback circuit is connected with the second output end of the voltage conversion circuit, and the output end of the feedback circuit is connected with the feedback control end of the voltage conversion circuit;
the feedback circuit is used for sending a feedback signal to the voltage conversion circuit when the output voltage of the first output end of the voltage conversion circuit is greater than a set voltage so as to improve the output voltage of the first output end of the voltage conversion circuit and the second output end of the voltage conversion circuit.
2. The backlight driving circuit according to claim 1, wherein the feedback circuit comprises a comparing unit and a feedback output unit;
the input end of the comparison unit is connected with the first output end of the voltage conversion circuit, and the output end of the comparison unit is connected with the control end of the feedback output unit;
the input end of the feedback output unit is connected with the second output end of the voltage conversion circuit, and the output end of the feedback output unit is connected with the feedback control end of the voltage conversion circuit;
the comparison unit is used for comparing the output voltage of the first output end of the voltage conversion circuit with a set voltage, and sending a control signal to the feedback output unit when the output voltage of the first output end of the voltage conversion circuit is determined to be greater than the set voltage, so that the feedback output unit sends a feedback signal to the voltage conversion circuit.
3. The backlight driving circuit according to claim 2, wherein the comparing unit comprises a zener diode and a first resistor;
the first end of the first resistor is connected with the first output end of the voltage conversion circuit, and the second end of the first resistor is connected with the anode of the voltage stabilizing diode;
and the cathode of the voltage stabilizing diode is connected with the control end of the feedback output unit.
4. The backlight driving circuit according to claim 2, wherein the comparing unit comprises a voltage comparator, a second resistor and a first switch tube;
the input end of the voltage comparator is connected with the first output end of the voltage conversion circuit, the reference end of the voltage comparator is used for inputting reference voltage, and the output end of the voltage comparator is connected with the control end of the first switching tube;
the first end of the first switch tube is connected with the first end of the second resistor, and the second end of the first switch tube is grounded;
and the second end of the second resistor is connected with the control end of the feedback output unit.
5. The backlight driving circuit according to any one of claims 2-4, wherein the feedback output unit comprises an optical coupler, a reference voltage chip, a third resistor and a fourth resistor;
the first end of the primary side of the optical coupler is connected with the second output end of the voltage conversion circuit, the second end of the primary side of the optical coupler is connected with the cathode of the reference voltage chip, and the anode of the reference voltage chip is grounded;
the first end of the secondary side of the optical coupler is connected with the feedback control end of the voltage conversion circuit, and the second end of the secondary side of the optical coupler is grounded;
the first end of the third resistor is connected with the second output end of the voltage conversion circuit, the second end of the third resistor is connected with the first end of the fourth resistor, and the second end of the fourth resistor is grounded;
the reference pole of the reference voltage chip is connected with the first end of the fourth resistor, and the first end of the fourth resistor is also connected with the output end of the comparison unit.
6. The backlight driving circuit according to claim 5, wherein the voltage converting circuit comprises a power control chip, a second switching tube, a third switching tube, a transformer, a first rectifying and filtering unit and a second rectifying and filtering unit;
the transformer comprises a primary winding, a first secondary winding and a second secondary winding;
the primary winding is used for inputting power voltage, and the second switching tube is connected in series in a loop where the primary winding is located;
the control end of the second switching tube is connected with a control signal output pin of the power control chip;
a feedback signal input pin of the power supply control chip is connected with the output end of the feedback circuit;
the first rectifying and filtering unit is connected between the first secondary winding and the first output end of the voltage conversion circuit, the second rectifying and filtering unit is connected between the second secondary winding and the second output end of the voltage conversion circuit, and the third switching tube is connected in a loop of the first rectifying and filtering unit.
7. The backlight driving circuit according to claim 6, wherein the first rectifying and filtering unit comprises an output control chip, a first diode and a first capacitor;
the anode of the first diode is connected with the first end of the first secondary winding, and the cathode of the first diode is connected with the first end of the third switching tube;
the second end of the third switching tube is grounded;
a control signal output pin of the output control chip is connected with a control end of the third switching tube;
the first end of the first capacitor is grounded, the second end of the first capacitor is connected with the second end of the first secondary winding, and the second end of the first capacitor is used for outputting a first direct-current voltage.
8. The backlight driving circuit according to claim 7, wherein the first rectifying and filtering unit further comprises a fifth resistor and a sixth resistor;
the first end of the fifth resistor is connected with the second end of the third switching tube, and the second end of the fifth resistor is grounded;
and the first end of the sixth resistor is connected with the first end of the fifth resistor, and the second end of the sixth resistor is connected with a feedback signal input pin of the output control chip.
9. The backlight driving circuit according to claim 6, wherein the second rectifying and filtering unit comprises a second diode and a second capacitor;
the anode of the second diode is connected with the first end of the second secondary winding, and the cathode of the second diode is used for outputting a second direct-current voltage;
the first end of the second capacitor is connected with the cathode of the second diode, the second end of the second capacitor is connected with the second end of the second secondary winding, and the second end of the second secondary winding is grounded.
10. A display device is characterized by comprising a backlight driving circuit, a backlight lamp and a main board;
the backlight driving circuit includes: a voltage conversion circuit and a feedback circuit;
the voltage conversion circuit comprises a feedback control end, an input end, a first output end and a second output end, and is used for converting the voltage of the input end and then outputting the converted voltage from the first output end and the second output end;
the first output end is connected with the backlight lamp and used for supplying power to the backlight lamp, and the second output end is connected with the mainboard and used for supplying power to the mainboard;
the first input end of the feedback circuit is connected with the first output end of the voltage conversion circuit, the second input end of the feedback circuit is connected with the second output end of the voltage conversion circuit, and the output end of the feedback circuit is connected with the feedback control end of the voltage conversion circuit;
the feedback circuit is used for sending a feedback signal to the voltage conversion circuit when the output voltage of the first output end of the voltage conversion circuit is greater than a set voltage so as to improve the output voltage of the first output end of the voltage conversion circuit and the second output end of the voltage conversion circuit.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020752508.8U CN211906916U (en) | 2020-05-08 | 2020-05-08 | Backlight driving circuit and display device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020752508.8U CN211906916U (en) | 2020-05-08 | 2020-05-08 | Backlight driving circuit and display device |
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| CN211906916U true CN211906916U (en) | 2020-11-10 |
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| CN202020752508.8U Active CN211906916U (en) | 2020-05-08 | 2020-05-08 | Backlight driving circuit and display device |
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