LED backlight driving circuit, driving method of LED backlight driving circuit and liquid crystal display device

Abstract

The invention discloses an LED backlight driving circuit, a driving method of the LED backlight driving circuit and a liquid crystal display device. The LED backlight driving circuit comprises an LED light bar and a power module driving the LED light bar. The output ends of the LED light bar are coupled to a short circuit protection module and a divider resistor respectively. The short circuit protection module comprises a comparison unit and a driving unit coupled to the comparison unit. The voltages at the two ends of the divider resistor are used as feedback voltages coupled to the comparison unit. The comparison unit is also coupled to a preset first reference voltage. When the value, by which the feedback voltages exceed the first reference voltage, is greater than a preset deviation value, the driving unit controls the power module to be switched off; when the first reference voltage is greater than or equal to the maximum brightness of the LED light bar in a normal state, the voltages at the two ends of the divider resistor are divided. The LED backlight driving circuit, the driving method of the LED backlight driving circuit and the liquid crystal display device have a short circuit protection function when an LED lamp bead is in a short circuit.

Description

technical field

[0001] The invention relates to the field of liquid crystal display, and more specifically, relates to an LED backlight driving circuit, a driving method thereof, and a liquid crystal display device. Background technique

[0002] The liquid crystal display device includes a liquid crystal panel and a backlight module. The backlight module includes multiple strings of LED light strips and their drive circuits. In the current design, due to the different voltages of the LED light strips, there will be some voltage differences. This voltage difference is loaded to a constant voltage. On the current drive chip or other devices, it will cause the temperature of the constant current drive chip or other devices to rise, so there is a solution to this problem: by changing the current size and duty cycle of each string, keep each string The same average current and the same voltage across. For example, if the voltage of a string of LED light strips is too small, you ...

Examples

Embodiment 1

[0058] Such as figure 1 , 2 As shown, the comparison unit in this embodiment includes a subtractor U1, a first input terminal of the subtractor U1 is coupled to the feedback voltage V1; a second input terminal thereof is coupled to the first reference voltage VF1. The difference between the feedback voltage and the first reference voltage VF1 can be directly output through the subtractor U1, so that the subsequent drive unit only needs to judge whether the difference exceeds a preset deviation value, and if it exceeds, the drive power supply module is turned off.

[0059] The driving unit includes a comparator U2, the first input terminal of the comparator U2 is coupled to the output terminal of the subtractor U1; the second input terminal of the comparator U2 is coupled with a second reference voltage VF2;

[0060] The second reference voltage VF2 is equal to the preset deviation value, and when the output voltage of the subtractor U1 is greater than the second reference vol...

Embodiment 2

[0064] Such as figure 1 , 3 As shown, the comparison unit in this embodiment includes a first controllable switch Q1, a first resistor R1, a second resistor R2 and a third resistor R3; the source of the first controllable switch Q1 is coupled to A reference high-level signal VCC, the drain of which is coupled to the ground terminal of the LED backlight drive circuit through the second resistor R2; the feedback voltage V1 is coupled to the gate of the first controllable switch Q1 through the third resistor R3; the second A reference voltage VF1 is coupled to the drain of the first controllable switch Q1; the source of the first controllable switch Q1 is also coupled to an inverter 43, and the output terminal of the inverter 43 is coupled to the drive unit ;

[0065] The inverter 43 includes a second controllable switch Q2, a third controllable switch Q3, a fourth resistor R4, and a fifth resistor R5;

[0066] The source of the second controllable switch Q2 is coupled to the ...

Embodiment 3

[0077] Such as Figure 4 Shown, a kind of driving method of LED backlight driving circuit, described LED backlight driving circuit comprises LED light bar, drives the power supply module of LED light bar, and described driving method comprises steps:

[0078] A: Connect the voltage dividing resistor R0 in series at the output end of the LED light bar; preset the first reference voltage VF1 and the deviation value;

[0079] The first reference voltage VF1 is greater than or equal to the maximum voltage at both ends of the divider resistor R0 when the normal LED light bar is at maximum brightness;

[0080] B: The voltage at both ends of the voltage dividing resistor R0 is compared with the first reference voltage VF1 as the feedback voltage, and if the difference between the feedback voltage and the first reference voltage VF1 exceeds a preset deviation value, the power supply module is controlled to be turned off.

technical field

[0001] The invention relates to the field of liquid crystal display, and more specifically, relates to an LED backlight driving circuit, a driving method thereof, and a liquid crystal display device. Background technique

[0002] The liquid crystal display device includes a liquid crystal panel and a backlight module. The backlight module includes multiple strings of LED light strips and their drive circuits. In the current design, due to the different voltages of the LED light strips, there will be some voltage differences. This voltage difference is loaded to a constant voltage. On the current drive chip or other devices, it will cause the temperature of the constant current drive chip or other devices to rise, so there is a solution to this problem: by changing the current size and duty cycle of each string, keep each string The same average current and the same voltage across. For example, if the voltage of a string of LED light strips is too small, you ...

Examples

Embodiment 1

[0058] Such as figure 1 , 2 As shown, the comparison unit in this embodiment includes a subtractor U1, a first input terminal of the subtractor U1 is coupled to the feedback voltage V1; a second input terminal thereof is coupled to the first reference voltage VF1. The difference between the feedback voltage and the first reference voltage VF1 can be directly output through the subtractor U1, so that the subsequent drive unit only needs to judge whether the difference exceeds a preset deviation value, and if it exceeds, the drive power supply module is turned off.

[0059] The driving unit includes a comparator U2, the first input terminal of the comparator U2 is coupled to the output terminal of the subtractor U1; the second input terminal of the comparator U2 is coupled with a second reference voltage VF2;

[0060] The second reference voltage VF2 is equal to the preset deviation value, and when the output voltage of the subtractor U1 is greater than the second reference vol...

Embodiment 2

[0064] Such as figure 1 , 3 As shown, the comparison unit in this embodiment includes a first controllable switch Q1, a first resistor R1, a second resistor R2 and a third resistor R3; the source of the first controllable switch Q1 is coupled to A reference high-level signal VCC, the drain of which is coupled to the ground terminal of the LED backlight drive circuit through the second resistor R2; the feedback voltage V1 is coupled to the gate of the first controllable switch Q1 through the third resistor R3; the second A reference voltage VF1 is coupled to the drain of the first controllable switch Q1; the source of the first controllable switch Q1 is also coupled to an inverter 43, and the output terminal of the inverter 43 is coupled to the drive unit ;

[0065] The inverter 43 includes a second controllable switch Q2, a third controllable switch Q3, a fourth resistor R4, and a fifth resistor R5;

[0066] The source of the second controllable switch Q2 is coupled to the ...

Embodiment 3

[0077] Such as Figure 4 Shown, a kind of driving method of LED backlight driving circuit, described LED backlight driving circuit comprises LED light bar, drives the power supply module of LED light bar, and described driving method comprises steps:

[0078] A: Connect the voltage dividing resistor R0 in series at the output end of the LED light bar; preset the first reference voltage VF1 and the deviation value;

[0079] The first reference voltage VF1 is greater than or equal to the maximum voltage at both ends of the divider resistor R0 when the normal LED light bar is at maximum brightness;

[0080] B: The voltage at both ends of the voltage dividing resistor R0 is compared with the first reference voltage VF1 as the feedback voltage, and if the difference between the feedback voltage and the first reference voltage VF1 exceeds a preset deviation value, the power supply module is controlled to be turned off.

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