TWI808050B - LED backlight circuit capable of eliminating ghost images, display device and information processing device - Google Patents

Abstract

An LED backlight circuit capable of eliminating ghost images, which has: a plurality of LED units, each with a string of LED lamp beads, the string of LED lamp beads has a current input end and a current output end, and the current output end of the LED units is coupled to a common contact point; a plurality of first switches, coupled between a positive voltage source and the current input end of the LED units; a current source circuit, coupled between the common contact point and a reference ground; The current input terminal is used to enable a corresponding discharge channel to discharge the parasitic capacitance of a corresponding current input terminal when a first switch is turned off; wherein, the discharge channel has: a second switch coupled between a current input terminal and a current source.

Description

LED backlight circuit capable of eliminating ghost images, display device and information processing device

The invention relates to an LED backlight circuit, in particular to an LED backlight circuit capable of eliminating ghost images.

A general LED backlight circuit has multiple strings of LED units to provide a backlight for a display module. Please refer to FIG. 1 , which shows a circuit diagram of a conventional LED backlight circuit. As shown in FIG. 1 , the LED backlight circuit has two LED units 11 , two first switches 12 , an NMOS transistor 13 and two filter capacitors 14 .

Each of the two LED units 11 has a string of LED beads. The current input end of one string of LED beads is coupled to a node A1, and the current output end is coupled to a node X; the current input end of the other string of LED beads is coupled to a node A2, and the current output end is coupled to a node X.

A channel of one of the two first switches 12 is coupled between a positive voltage source V _DD and the node A1 , and a channel of the other switch is coupled between the positive voltage source V _DD and the node A2 .

The NMOS transistor 13 is coupled between the node X and a reference ground to determine a channel current.

The two filter capacitors 14 are used to filter power noise.

During operation, the two first switches 12 are turned on alternately so that the two LED units 11 emit light alternately.

However, when the first switch 12 connected to the node A1 just changes from being on to being off, the parasitic capacitance of the node A1 still stores charges and has a voltage. When the voltage is higher than the conduction threshold voltage of the corresponding string of LED beads, the string of LED beads will flash for a while, commonly known as ghosting.

In order to solve the above problems, there is an urgent need in the art for a novel LED backlight circuit capable of eliminating ghost images.

The main purpose of the present invention is to disclose an LED backlight circuit capable of eliminating ghost images, which can eliminate the stored charge of the parasitic capacitance of the power supply end of a disconnected LED unit through a discharge circuit, thereby avoiding the occurrence of ghost images.

Another object of the present invention is to disclose a display device, which can improve the quality of its display image by using the above-mentioned LED backlight driving circuit.

Another object of the present invention is to disclose an information processing device, which can improve the display quality of its screen through the above-mentioned LED backlight driving circuit.

In order to achieve the aforementioned purpose, an LED backlight circuit capable of eliminating ghost images is proposed, which has:

A plurality of LED units, each having a string of LED lamp beads, the string of LED lamp beads has a current input terminal and a current outflow terminal, and the current outflow terminals of the LED units are coupled to a common contact;

a plurality of first switches, coupled between a positive voltage source and the current input terminals of the LED units;

a current source circuit coupled between the common junction and a reference ground; and

A discharge circuit has a plurality of discharge channels correspondingly coupled to the current input terminals of the LED units, for enabling a corresponding discharge channel to perform a discharge operation on a parasitic capacitance of a corresponding current input terminal when the first switch is turned off.

In one embodiment, the discharge channel has:

A second switch is coupled between a current input terminal and a low potential, and the low potential is lower than the conduction voltage of the string of LED beads of a corresponding LED unit.

In one embodiment, the low potential is derived from the positive voltage source through a fixed voltage drop.

In one embodiment, the discharge channel has:

A second switch is coupled between a current input terminal and a current source.

In one embodiment, the discharge circuit further has:

A voltage detection circuit is used to detect the residual voltage of the current input terminals of the LED units, and turn off a corresponding second switch when a residual voltage is lower than a predetermined voltage.

To achieve the aforementioned purpose, the present invention further proposes a display device, which has a display panel and a backlight module, wherein the backlight module has an LED backlight circuit, and the LED backlight circuit has:

A plurality of LED units, each having a string of LED lamp beads, the string of LED lamp beads has a current input terminal and a current outflow terminal, and the current outflow terminals of the LED units are coupled to a common contact;

a plurality of first switches, coupled between a positive voltage source and the current input terminals of the LED units;

a current source circuit coupled between the common junction and a reference ground; and

A discharge circuit has a plurality of discharge channels correspondingly coupled to the current input terminals of the LED units, for enabling a corresponding discharge channel to perform a discharge operation on a parasitic capacitance of a corresponding current input terminal when the first switch is turned off.

In one embodiment, the discharge channel has:

A second switch is coupled between a current input terminal and a low potential, and the low potential is lower than the conduction voltage of the string of LED beads of a corresponding LED unit.

In one embodiment, the low potential is derived from the positive voltage source through a fixed voltage drop.

In one embodiment, the discharge channel has:

A second switch is coupled between a current input terminal and a current source.

In one embodiment, the discharge circuit further has:

A voltage detection circuit is used to detect the residual voltage of the current input terminals of the LED units, and turn off a corresponding second switch when a residual voltage is lower than a predetermined voltage.

To achieve the aforementioned purpose, the present invention further proposes an information processing device, which has a central processing unit and the aforementioned display device, wherein the central processing unit is used to communicate with the display device.

In a possible embodiment, the information processing device may be a smart phone, a portable computer, a vehicle computer, a wearable electronic device or an advertising billboard.

In order to enable your review committee members to further understand the structure, features and purpose of the present invention, drawings and detailed descriptions of preferred specific embodiments are hereby attached.

Please refer to FIG. 2 , which is a circuit diagram of an embodiment of an LED backlight circuit capable of eliminating ghost images according to the present invention. As shown in FIG. 2 , an LED backlight circuit 100 capable of eliminating ghost images has two LED units 110 , two first switches 120 , a current source circuit 130 , two filter capacitors 140 and a discharge circuit 150 .

Each of the two LED units 110 has a string of LED beads. The current input end of one string of LED beads is coupled to a node A1, and the current output end is coupled to a node X; the current input end of the other string of LED beads is coupled to a node A2, and the current output end is coupled to node X.

A channel of one of the two first switches 120 is coupled between a positive voltage source V _DD and the node A1 , and a channel of the other switch is coupled between the positive voltage source V _DD and the node A2 .

The current source circuit 130 is coupled between the node X and a reference ground to determine a channel current.

The two filter capacitors 140 are used to filter power noise.

The discharge circuit 150 has a plurality of discharge channels correspondingly coupled to the current input terminals (contacts A1, A2) of the LED units 110, for enabling a corresponding discharge channel to perform a discharge operation on the parasitic capacitance of a corresponding current input terminal (contacts A1 or A2) when a first switch 120 is turned off.

During operation, the two first switches 120 are turned on alternately to make the two LED units 110 emit light alternately. Since the discharge circuit 150 quickly discharges the turned-off LED units 110 , ghost spots can be avoided.

Please refer to FIG. 3 , which shows a circuit diagram of an embodiment of the discharge circuit 150 in the LED backlight circuit of FIG. 2 . As shown in FIG. 3 , the discharge circuit 150 has two second switches 151 and a certain voltage source 152. The two second switches 151 are used to realize the two discharge channels. One second switch 151 is coupled between a current input terminal (contact A1) and a low potential V _L , and the other second switch 151 is coupled between another current input terminal (contact A2) and a low potential V _{L, and the low potential V L is} lower than the conduction voltage of the string of LED lamp beads of any one of the LED units. In addition, the low potential V _L is obtained from the positive voltage source V _DD via a fixed voltage drop V _S of the constant voltage source 152 , that is, V _L = V _DD - V _S .

Please refer to FIG. 4 a , which shows a circuit diagram of another embodiment of the discharge circuit 150 in the LED backlight circuit of FIG. 2 . As shown in Figure 4a, the discharge circuit 150 has two second switches 151 and a certain current source 153, the two second switches 151 are used to realize the two discharge channels, wherein one second switch 151 is coupled between a current input terminal (contact A1) and the constant current source 153, and another second switch 151 is coupled between the other current input terminal (contact A2) and the constant current source 153, and has a current input contact and a current output contact, the current enters the contact The point is coupled to the other end of the channel of the second switch, and the current sink point is coupled to the reference ground.

Please refer to FIG. 4 b , which shows a circuit diagram of another embodiment of the discharge circuit 150 in the LED backlight circuit of FIG. 2 . As shown in Figure 4b, the discharge circuit 150 has two second switches 151, a constant current source 153, a comparator 154, a threshold voltage source 155, and two third switches 156, wherein the functions of the two second switches 151 and the constant current source 153 are the same as those shown in Figure 4a; 1. The residual voltage of A2), and when a residual voltage is lower than a predetermined voltage of the threshold voltage source 155, a corresponding second switch 151 is turned off.

According to the above description, the present invention further provides a display device. Please refer to FIG. 5 , which shows a block diagram of an embodiment of the display device of the present invention. As shown in FIG. 5 , a display device 200 has a display panel 210 and a backlight module 220 , wherein the backlight module 220 has the aforementioned LED backlight circuit 100 .

According to the above description, the present invention further provides an information processing device. Please refer to FIG. 6 , which shows a block diagram of an embodiment of the information processing device of the present invention. As shown in FIG. 6, an information processing device 300 has a central processing unit 310 and a display device 320, wherein the display device 320 is realized by the display device 200 shown in FIG. 5, and the central processing unit 310 is used to communicate with the display device 320. In addition, the information processing device 300 can be a smart phone, a portable computer, a vehicle computer, a wearable electronic device or an advertising billboard.

With the design disclosed above, the present invention has the following advantages:

1. The ghost-eliminating LED backlight circuit of the present invention can use a discharge circuit to clear the stored charge of the parasitic capacitance of the power supply end of a disconnected LED unit, thereby avoiding the ghost phenomenon.

2. The display device of the present invention can improve the quality of its display screen by the above-mentioned LED backlight driving circuit.

3. The information processing device of the present invention can improve the display quality of its screen through the above-mentioned LED backlight driving circuit. What is disclosed in this case is a preferred embodiment. For example, any partial changes or modifications derived from the technical ideas of this case and easily deduced by those who are familiar with the technology are within the scope of the patent right of this case.

To sum up, regardless of the purpose, means and efficacy of this case, it shows that it is very different from the conventional technology, and it is the first invention to be practical, which indeed meets the patent requirements of the invention. I sincerely hope that the review committee will be aware of it and grant a patent as soon as possible to benefit the society. This is my best prayer.

11: LED unit 12: First switch 13: NMOS transistor 14: filter capacitor 100: LED backlight circuit 110: LED unit 120: first switch 130: Current source circuit 140: filter capacitor 150: discharge circuit 151: second switch 152: constant voltage source 153: constant current source 154: Comparator 155: threshold voltage source 156: The third switch 200: display device 210: display panel 220: Backlight module 300: information processing device 310: central processing unit 320: display device

FIG. 1 shows a circuit diagram of a conventional LED backlight circuit. FIG. 2 is a circuit diagram of an embodiment of an LED backlight circuit capable of eliminating ghost images according to the present invention. FIG. 3 shows a circuit diagram of an embodiment of the discharge circuit in the LED backlight circuit of FIG. 2 . FIG. 4a is a circuit diagram of another embodiment of the discharge circuit in the LED backlight circuit of FIG. 2 . FIG. 4 b is a circuit diagram of another embodiment of the discharge circuit in the LED backlight circuit of FIG. 2 . FIG. 5 shows a block diagram of an embodiment of the display device of the present invention. FIG. 6 is a block diagram of an embodiment of an information processing device of the present invention.

100: LED backlight circuit

110: LED unit

120: first switch

130: Current source circuit

140: filter capacitor

150: discharge circuit

Claims (6)

An LED backlight circuit capable of eliminating ghost images, which has: A plurality of LED units, each having a string of LED lamp beads, the string of LED lamp beads has a current input terminal and a current outflow terminal, and the current outflow terminals of the LED units are coupled to a common contact; a plurality of first switches, coupled between a positive voltage source and the current input terminals of the LED units; a current source circuit coupled between the common junction and a reference ground; and A discharge circuit, having a plurality of discharge channels correspondingly coupled to the current input terminals of the LED units, for enabling a corresponding discharge channel to perform a discharge operation on a parasitic capacitance of a corresponding current input terminal when a said first switch is turned off; Wherein, the discharge channel has: A second switch is coupled between a current input terminal and a current source. The LED backlight circuit capable of eliminating ghost images as described in item 1 of the scope of the patent application, wherein the discharge circuit further has: A voltage detection circuit is used to detect the residual voltage of the current input terminals of the LED units, and turn off a corresponding second switch when a residual voltage is lower than a predetermined voltage. A display device has a display panel and a backlight module, wherein the backlight module has an LED backlight circuit, and the LED backlight circuit has: A plurality of LED units, each having a string of LED lamp beads, the string of LED lamp beads has a current input terminal and a current outflow terminal, and the current outflow terminals of the LED units are coupled to a common contact; a plurality of first switches, coupled between a positive voltage source and the current input terminals of the LED units; a current source circuit coupled between the common junction and a reference ground; and A discharge circuit, having a plurality of discharge channels correspondingly coupled to the current input terminals of the LED units, for enabling a corresponding discharge channel to perform a discharge operation on a parasitic capacitance of a corresponding current input terminal when a said first switch is turned off; Wherein, the discharge channel has: A second switch is coupled between a current input terminal and a current source. The display device as described in item 3 of the scope of the patent application, wherein the discharge circuit further has: A voltage detection circuit is used to detect the residual voltage of the current input terminals of the LED units, and turn off a corresponding second switch when a residual voltage is lower than a predetermined voltage. An information processing device has a central processing unit and a display device as described in any one of items 3 to 4 of the scope of the patent application, wherein the central processing unit is used to communicate with the display device. The information processing device described in item 5 of the scope of the patent application is a device selected from the group consisting of a smart phone, a portable computer, a vehicle computer, a wearable electronic device and an advertising billboard.

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