Backlight driving circuit, switching power supply, backlight module, and display apparatus

Abstract

The present invention provides a backlight driving circuit, a switching power supply, a backlight module, and a display apparatus. The backlight driving circuit comprises: a control sub-circuit, comprising a first pin and providing a control signal by means of the first pin; a driving sub-circuit, separately connected to the first pin, a first node, a second node and a third node, the first node being connected to a power supply, a positive electrode of a first light-emitting assembly and a positive electrode of a second light-emitting assembly, the second node being connected to a negative electrode of the first light-emitting assembly, the third node being connected to a negative electrode of the second light-emitting assembly, and the driving sub-circuit, under the control of the control signal, providing to the first node a driving current for driving the first light-emitting assembly and the second light-emitting assembly. The present invention can reduce the number of backlight driving circuits, saving costs, and ensure uniformity of brightness of the two light-emitting assemblies, improving the reliability of the switching power supply.

Description

Backlight driving circuit, switching power supply, backlight module and display device Technical Field

[0001] The embodiments of the present invention relate to the field of backlight driving technology, and in particular to a backlight driving circuit, a switching power supply, a backlight module and a display device. Background Art

[0002] LCD TVs typically use switching power supplies as their power supply module. Switching power supplies are characterized by high efficiency, compact size, and stable voltage output, making them widely used in electronic product power supply systems. With the widespread use of switching power supplies, the demand for cost control is also increasing. Currently, a backlight driver circuit (consisting of a backlight IC (integrated circuit) and its peripheral circuits) in a switching power supply can only drive one backlight strip (LED). To drive two backlight strips, as shown in Figure 1, two backlight driver circuits are required (Figure 1 only shows the backlight IC), which is costly. Furthermore, due to differences in the components within the backlight driver circuits, the drive currents generated by the two backlight driver circuits may be inconsistent, making it difficult to ensure uniform brightness across the two backlight strips.

[0003] Summary of the Invention

[0004] The embodiments of the present invention provide a backlight driving circuit, a switching power supply, a backlight module and a display device, which are used to solve the problem that two sets of backlight driving circuits are used to drive two backlight strips, which is costly and difficult to ensure brightness uniformity of the two backlight strips.

[0005] In order to solve the above-mentioned technical problems, the present invention is achieved as follows:

[0006] In a first aspect, an embodiment of the present invention provides a backlight driving circuit, comprising:

[0007] A control subcircuit includes a first pin, and a control signal is provided through the first pin;

[0008] A driving subcircuit is connected to the first pin, the first node, the second node and the third node respectively, the first node is connected to the power supply, the positive electrode of the first light-emitting component and the positive electrode of the second light-emitting component, the second node is connected to the negative electrode of the first light-emitting component, and the third node is connected to the negative electrode of the second light-emitting component. Under the control of the control signal, the driving subcircuit provides a driving current to the first node to drive the first light-emitting component and the second light-emitting component.

[0009] Optionally, the driving sub-circuit includes:

[0010] a switch device, wherein a control terminal of the switch device is connected to the first pin, a first terminal is connected to the first node, and a second terminal is grounded, and the switch device is turned on or off under the control of the control signal;

[0011] A common-mode inductor includes a magnetic core and a first winding and a second winding wound on the magnetic core, wherein the first end of the first winding is connected to the second node, the second end of the first winding is connected to the first node, the first end of the second winding is connected to the first node, and the second end of the second winding is connected to the third node.

[0012] Optionally, the first winding and the second winding have the same number of turns.

[0013] Optionally, the switching device is a MOS tube.

[0014] Optionally, the driving sub-circuit further includes:

[0015] a first freewheeling diode, wherein a cathode of the first freewheeling diode is connected to the first node, and an anode of the first freewheeling diode is connected to the fourth node;

[0016] a second freewheeling diode, wherein a cathode of the second freewheeling diode is connected to the fourth node, and an anode of the second freewheeling diode is connected to the second end of the first winding;

[0017] a third freewheeling diode, wherein a cathode of the third freewheeling diode is connected to the fourth node, and an anode of the third freewheeling diode is connected to the first end of the second winding;

[0018] wherein the first electrode of the switching device is connected to the first node via the first freewheeling diode;

[0019] The second end of the first winding is connected to the first node through the second freewheeling diode and the first freewheeling diode;

[0020] The first end of the second winding is connected to the first node through the third freewheeling diode and the first freewheeling diode.

[0021] Optionally, the driving sub-circuit further includes:

[0022] a first capacitor, wherein a first electrode of the first capacitor is connected to the first node, and a second electrode of the first capacitor is connected to the second node;

[0023] A second capacitor, wherein a first electrode of the second capacitor is connected to the first node, and a second electrode of the second capacitor is connected to the third node.

[0024] Optionally, the driving sub-circuit is a buck circuit or a boost circuit.

[0025] Optionally, the control subcircuit further includes: a second pin, through which current detection is performed on the drive subcircuit, and the second pin is connected to the fifth node;

[0026] The driving sub-circuit further includes:

[0027] a third resistor, one end of the third resistor being connected to the fifth node, and the other end of the third resistor being connected to the sixth node;

[0028] a fifth resistor, one end of the fifth resistor being connected to the sixth node and the other end being grounded;

[0029] a sixth resistor, one end of the sixth resistor being connected to the sixth node and the other end being grounded;

[0030] Wherein, the second electrode of the switching device is grounded through the sixth resistor.

[0031] In a second aspect, an embodiment of the present invention provides a switching power supply, comprising the backlight driving circuit described in the first aspect.

[0032] In a third aspect, an embodiment of the present invention provides a backlight module including the above-mentioned switching power supply.

[0033] In a fourth aspect, an embodiment of the present invention provides a display device comprising the above-mentioned backlight module.

[0034] In the embodiments of the present invention, a single backlight driver circuit can drive two light-emitting components. This reduces the number of backlight driver circuits, optimizes circuit design, and saves costs. The reduction in components also improves the reliability of the backlight driver circuit. Furthermore, because a single backlight driver circuit is used, the drive current input to the two light-emitting components is consistent, ensuring uniform brightness across the two components, further improving reliability and effectively reducing product size. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0036] FIG1 is a schematic structural diagram of an existing backlight driving circuit;

[0037] FIG2 is a block diagram of a backlight driving circuit according to an embodiment of the present invention;

[0038] 3 is a schematic structural diagram of a backlight driving circuit according to an embodiment of the present invention;

[0039] FIG4 is a schematic structural diagram of a control subcircuit according to an embodiment of the present invention;

[0040] 5 is a schematic diagram of current flow in a backlight driving circuit when a switching device is turned on according to an embodiment of the present invention;

[0041] FIG6 is a schematic diagram of current flow in the backlight driving circuit when the switch device is turned off according to an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0043] Referring to FIG. 2 , an embodiment of the present invention provides a backlight driving circuit, including:

[0044] A control subcircuit includes a first pin, and a control signal is provided through the first pin;

[0045] A driving subcircuit is connected to the first pin, the first node, the second node and the third node respectively, the first node is connected to the power supply (Vin), the positive electrode of the first light-emitting component and the positive electrode of the second light-emitting component, the second node is connected to the negative electrode of the first light-emitting component, and the third node is connected to the negative electrode of the second light-emitting component. Under the control of the control signal, the driving subcircuit provides a driving current to the first node to drive the first light-emitting component and the second light-emitting component.

[0046] In the embodiment of the present invention, the control sub-circuit may also be referred to as a backlight IC or a backlight control chip, and the driving sub-circuit may also be referred to as a peripheral circuit of the backlight IC.

[0047] In the embodiment of the present invention, the first light-emitting component and the second light-emitting component may be LED light bars, which may also be called backlight light bars.

[0048] In the embodiments of the present invention, a single backlight driver circuit can drive two light-emitting components. This reduces the number of backlight driver circuits, optimizes circuit design, and saves costs. The reduction in components also improves the reliability of the backlight driver circuit. Furthermore, because a single backlight driver circuit is used, the drive current input to the two light-emitting components is consistent, ensuring uniform brightness across the two components, further improving reliability and effectively reducing product size.

[0049] In an embodiment of the present invention, optionally, the driving sub-circuit is a buck circuit or a boost circuit. In the following embodiments, a buck circuit is used as an example for illustration. The basic feature of a buck circuit is a DC-DC (voltage converter) conversion circuit, and the output voltage is lower than the input voltage. The input current is pulsating, and the output current is continuous. The Buck circuit uses a switching device to "chop" the input DC power supply to form a square wave. A square wave is used to control the switching device, allowing the switching device to switch on and off according to the control signal, adjusting the duty cycle of the square wave, and controlling the energy passing through. The square wave passing through the switching device is then low-pass filtered to output a DC voltage.

[0050] Referring to FIG3 , in an embodiment of the present invention, optionally, the driving sub-circuit includes:

[0051] A switching device PQ1, wherein the control end of the switching device PQ1 (the first end of PQ1 in the figure) is connected to the first pin GATE of the control sub-circuit PU1 (pin 8 of PU1 in the figure), the first pole (the third end of PQ1 in the figure) is connected to the first node, and the second pole (the second end of PQ1 in the figure) is grounded. The switching device PQ1 is turned on or off under the control of the control signal; in an embodiment of the present invention, optionally, the switching device is a MOS tube (metal (Metal)-oxide (Oxide)-semiconductor (Semiconductor) field-effect transistor).

[0052] A common-mode inductor PL1 includes a magnetic core and a first winding and a second winding wound on the magnetic core, wherein the first end of the first winding (the third end of PL1 in the figure) is connected to the second node, the second end of the first winding (the fourth end of PL1 in the figure) is connected to the first node, the first end of the second winding (the second end of PL1 in the figure) is connected to the first node, and the second end of the second winding (the first end of PL1 in the figure) is connected to the third node.

[0053] In an embodiment of the present invention, electromagnetic induction in a common-mode inductor can be used to induce a current, thereby simultaneously providing drive current to both the first light-emitting component LED1 and the second light-emitting component LED2. Electromagnetic induction refers to the electromotive force generated by a conductor placed in a changing magnetic flux. If this conductor is closed into a loop, this electromotive force drives electrons to flow, forming an induced current. Referring to Figure 3, according to the right-hand rule of electromagnetic induction in a common-mode inductor, the currents at like ends (terminals 3 and 2 of PL1 in the figure) on a closed magnetic core are equal in magnitude and opposite in direction.

[0054] In the embodiment of the present invention, in order to ensure that the driving currents input to the two light-emitting components are consistent, the first winding and the second winding have the same number of turns.

[0055] In the embodiment of the present invention, the driving subcircuit uses a common mode inductor to induce a current, thereby providing driving current to two light-emitting components at the same time. In other embodiments of the present invention, other methods are also used to provide two driving currents simultaneously.

[0056] In the embodiment shown in FIG3 , the driving sub-circuit may further include:

[0057] The fourth resistor PR4 is arranged between the control end of the switching device PQ1 and the first pin GATE of the control sub-circuit PU1, one end of which is connected to the first pin GATE of the control sub-circuit PU1 (pin 8 of PU1 in the figure), and the other end of which is connected to the control end of the switching device PQ1 (pin 1 of PQ1 in the figure).

[0058] Referring to FIG3 , in an embodiment of the present invention, optionally, the driving sub-circuit further includes:

[0059] a first freewheeling diode PD1, wherein a cathode of the first freewheeling diode PD1 (the second end of PD1 in the figure) is connected to the first node, and an anode of the first freewheeling diode PD1 (the first end of PD1 in the figure) is connected to the fourth node;

[0060] a second freewheeling diode PD2, wherein the cathode of the second freewheeling diode PD2 (the second end of PD2 in the figure) is connected to the fourth node, and the anode of the second freewheeling diode PD2 (the first end of PD2 in the figure) is connected to the second end of the first winding (the fourth end of PL1 in the figure);

[0061] a third freewheeling diode PD3, wherein the cathode of the third freewheeling diode PD3 (the second end of PD3 in the figure) is connected to the fourth node, and the anode of the third freewheeling diode PD3 (the first end of PD3 in the figure) is connected to the first end of the second winding (the second end of PL1 in the figure);

[0062] Wherein, the first electrode of the switching device PQ1 (the third terminal of PQ1 in the figure) is connected to the first node through the first freewheeling diode PD1;

[0063] The second end of the first winding (the fourth end of PL1 in the figure) is connected to the first node through the second freewheeling diode PD2 and the first freewheeling diode PD1;

[0064] The first end of the second winding (the second end of PL1 in the figure) is connected to the first node through the third freewheeling diode PD3 and the first freewheeling diode PD1.

[0065] A flyback diode, sometimes also called a freewheeling diode or snubber diode, is used with inductive loads. When the current in an inductive load suddenly changes or decreases, a sudden voltage surge will occur across the inductor, potentially damaging other components. Using a freewheeling diode allows the current to change more smoothly, preventing voltage surges.

[0066] Referring to FIG3 , in an embodiment of the present invention, optionally, the driving sub-circuit further includes:

[0067] a first capacitor PCE1, wherein a first electrode of the first capacitor PCE1 (the first end of PCE1 in the figure) is connected to the first node, and a second electrode of the first capacitor PCE1 (the second end of PCE1 in the figure) is connected to the second node;

[0068] The second capacitor PCE2, the first electrode of the second capacitor PCE2 (the first end of PCE2 in the figure) is connected to the first node, and the second electrode ((the second end of PCE2 in the figure)) is connected to the third node.

[0069] Please refer to Figure 3. In an embodiment of the present invention, optionally, the control sub-circuit PU1 further includes: a second pin CS, through which the current of the driving sub-circuit is detected, and the second pin CS is connected to the fifth node; the second pin CS can also be called a current detection pin; the control sub-circuit PU1 is used to control the size and accuracy of the backlight current provided by the driving sub-circuit according to the current detected by the second pin CS.

[0070] The driving sub-circuit further includes:

[0071] a third resistor PR3, one end of the third resistor PR3 being connected to the fifth node, and the other end of the third resistor PR3 being connected to the sixth node;

[0072] a fifth resistor PR5, one end of the fifth resistor PR5 being connected to the sixth node, and the other end of the fifth resistor PR5 being grounded;

[0073] a sixth resistor PR6, one end of the sixth resistor PR6 being connected to the sixth node, and the other end of the sixth resistor PR6 being grounded;

[0074] The second electrode of the switch device PQ1 (the second end of PQ1 in the figure) is grounded through the sixth resistor PR6.

[0075] In the embodiment of the present invention, optionally, the control sub-circuit PU1 may further include: a third pin ZVS, also known as a zero voltage switching pin;

[0076] Correspondingly, the driving sub-circuit further includes:

[0077] a capacitor PC1, wherein a first electrode of the capacitor PC1 is connected to the third pin ZVS, and a second electrode of the capacitor PC1 is grounded;

[0078] a capacitor PC2, wherein a first electrode of the capacitor PC2 is connected to the fifth node, and a second electrode of the capacitor PC2 is grounded;

[0079] a first resistor PR1, wherein one end of the first resistor PR1 is connected to the third pin ZVS, and the other end of the first resistor PR1 is grounded;

[0080] a second resistor PR2, one end of the second resistor PR2 being connected to the third pin ZVS, and the other end of the second resistor PR2 being connected to one end of the capacitor PC3;

[0081] Capacitor PC3 , one end of the capacitor PC3 is connected to the other end of the second resistor PR2 , and the other end of the capacitor PC3 is connected to the second end of the first winding (the fourth end of PL1 in the figure).

[0082] With the above structure, when the driving sub-circuit is working, the voltage across the switching device when it is turned on and off is 0, so that the switching loss of the switching device can be reduced to a minimum.

[0083] In the embodiment of the present invention, referring to FIG3 and FIG4 , the control sub-circuit PU1 may further include:

[0084] The fourth pin GND, also known as the ground pin, is used for grounding;

[0085] The fifth pin, VIN, can also be called the power pin, which is used to connect to the power supply (such as the 12V power supply in the figure);

[0086] The sixth pin LPWM is used to connect to the LPWM signal;

[0087] The seventh pin HPWM is used to connect to the HPWM signal;

[0088] The eighth pin FAULT, also called a fault feedback pin, is used to detect faults.

[0089] The working principle of the backlight driving circuit according to the embodiment of the present invention is described below.

[0090] For illustration, the embodiment shown in Figure 3 is used. When switch PQ1 is on, the current flows in the direction shown in Figure 5, where the dashed arrow represents the second backlight current generated by electromagnetic induction, its magnitude remaining the same as in the original circuit. When switch PQ1 is on, Vin supplies power to LEDs 1 and 2, common-mode inductor PL1 stores energy, and the current rises linearly, simultaneously charging capacitors PCE1 and PCE2.

[0091] When switch PQ1 is off, the current flows in the direction shown in Figure 6, where the dotted arrows represent the second backlight current induced by electromagnetic induction. At this point, common-mode inductor PL1 transfers its stored energy to LED1 and LED2 via freewheeling diodes PD2 and PD3, respectively. Meanwhile, capacitors PCE1 and PCE2 also power LED1 and LED2, respectively.

[0092] The embodiment of the present invention further provides a switching power supply, comprising the backlight driving circuit described in any of the above embodiments. The switching power supply in the embodiment of the present invention is suitable for complete machine projects with a total output power of less than 200W.

[0093] An embodiment of the present invention further provides a backlight module, comprising the above-mentioned switching power supply.

[0094] An embodiment of the present invention further provides a display device including the above-mentioned backlight module.

[0095] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are protected by the present invention.

Claims

1. A backlight driving circuit, characterized in that: include: A control subcircuit includes a first pin, and a control signal is provided through the first pin; A driving subcircuit is connected to the first pin, the first node, the second node and the third node respectively, the first node is connected to the power supply, the positive electrode of the first light-emitting component and the positive electrode of the second light-emitting component, the second node is connected to the negative electrode of the first light-emitting component, and the third node is connected to the negative electrode of the second light-emitting component. Under the control of the control signal, the driving subcircuit provides a driving current to the first node to drive the first light-emitting component and the second light-emitting component.

2. The backlight driving circuit according to claim 1, wherein: The driving sub-circuit comprises: a switch device, wherein a control terminal of the switch device is connected to the first pin, a first terminal is connected to the first node, and a second terminal is grounded, and the switch device is turned on or off under the control of the control signal; A common-mode inductor includes a magnetic core and a first winding and a second winding wound on the magnetic core, wherein the first end of the first winding is connected to the second node, the second end of the first winding is connected to the first node, the first end of the second winding is connected to the first node, and the second end of the second winding is connected to the third node.

3. The backlight driving circuit according to claim 2, wherein: The first winding and the second winding have the same number of turns.

4. The backlight driving circuit according to claim 2, wherein: The switch device is a MOS tube.

5. The backlight driving circuit according to claim 2, wherein: The driving sub-circuit further includes: a first freewheeling diode, wherein a cathode of the first freewheeling diode is connected to the first node, and an anode of the first freewheeling diode is connected to the fourth node; a second freewheeling diode, wherein a cathode of the second freewheeling diode is connected to the fourth node, and an anode of the second freewheeling diode is connected to the second end of the first winding; a third freewheeling diode, wherein a cathode of the third freewheeling diode is connected to the fourth node, and an anode of the third freewheeling diode is connected to the first end of the second winding; wherein the first electrode of the switching device is connected to the first node via the first freewheeling diode; The second end of the first winding is connected to the first node through the second freewheeling diode and the first freewheeling diode; The first end of the second winding is connected to the first node through the third freewheeling diode and the first freewheeling diode.

6. The backlight driving circuit according to claim 2 or 5, characterized in that: The driving sub-circuit further includes: a first capacitor, wherein a first electrode of the first capacitor is connected to the first node, and a second electrode of the first capacitor is connected to the second node; A second capacitor, wherein a first electrode of the second capacitor is connected to the first node, and a second electrode of the second capacitor is connected to the third node.

7. The backlight driving circuit according to claim 1, wherein: The driving sub-circuit is a step-down circuit or a step-up circuit.

8. The backlight driving circuit according to claim 2, wherein: The control subcircuit further includes: a second pin, through which current detection of the driving subcircuit is performed, the second pin being connected to the fifth node; The driving sub-circuit further includes: a third resistor, one end of the third resistor being connected to the fifth node, and the other end of the third resistor being connected to the sixth node; a fifth resistor, one end of the fifth resistor being connected to the sixth node and the other end being grounded; a sixth resistor, one end of the sixth resistor being connected to the sixth node and the other end being grounded; Wherein, the second electrode of the switching device is grounded through the sixth resistor.

9. A switching power supply, characterized in that: The backlight driving circuit comprises the backlight driving circuit according to any one of claims 1 to 8.

10. A backlight module, characterized in that: Comprising the switching power supply as claimed in claim 9.

11. A display device, characterized in that: It comprises the backlight module as claimed in claim 10.

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