CN104376816A - LED backlight drive circuit, LED backlight device and display device - Google Patents

Abstract

The invention provides an LED backlight driving circuit, an LED backlight device and a display device. The LED backlight drive circuit is used to drive the LED backlight circuit, the LED backlight circuit includes at least one LED backlight unit, the first end of the LED backlight unit is connected to the LED drive voltage, and the LED backlight drive circuit includes The second end of the at least one LED backlight unit provides a reference voltage supply unit for a predetermined reference voltage, and the LED backlight drive circuit further includes at least one temperature compensation resistor unit; the temperature compensation resistor unit is connected to the LED backlight unit Between the second end of the second end and a level output end; the resistance value of the temperature compensation resistance unit increases with the increase of temperature, and the resistance value of the temperature compensation resistance unit decreases with the decrease of temperature. The invention can ensure that the current flowing through the LED is maintained within a certain range, improves the reliability of the LED, and solves the problems of high power consumption and short service life of the LED in the prior art.

Description

LED backlight driving circuit, LED backlight device and display device

technical field

The present invention relates to the field of display technology, in particular to an LED (Light-Emitting Diode, light-emitting diode) backlight drive circuit, an LED backlight device and a display device.

Background technique

Because the LED backlight circuit has the advantages of thinness, low power consumption, high luminous efficiency, and strong color expression, the current LED backlight circuit has become a new trend in the development of backlight technology. The backlight circuit of LCD (Liquid Crystal Display, Liquid Crystal Display) display products LED backlight circuits have also been increasingly selected.

However, LED is limited by its own production process and the influence of ambient temperature when working, so that when the current passing through the LED becomes larger, or even the current flowing through the LED exceeds the rated current value for a long time, the life of the LED will be shortened. At the same time, more power consumption will be added.

Contents of the invention

The main purpose of the present invention is to provide a LED backlight drive circuit, LED backlight device and display device, to ensure that the current flowing through the LED is maintained within a certain range, improve the reliability of the LED, and solve the problems of high power consumption and LED in the prior art. The problem of short service life.

In order to achieve the above object, the present invention provides an LED backlight drive circuit for driving the LED backlight circuit, the LED backlight circuit includes at least one LED backlight unit, the first end of the LED backlight unit is connected to the LED drive voltage, The LED backlight drive circuit includes a reference voltage supply unit for providing a predetermined reference voltage to the second end of the at least one LED backlight unit, and the LED backlight drive circuit also includes at least one temperature compensation resistor unit;

The temperature compensation resistor unit is connected between the second terminal of the LED backlight unit and a level output terminal;

The resistance value of the temperature compensation resistance unit increases as the temperature increases, and the resistance value of the temperature compensation resistance unit decreases as the temperature decreases.

In practice, the temperature compensation resistance unit includes an adjusting resistor and a thermistor connected in parallel; the thermistor has a positive temperature coefficient.

In practice, the temperature compensation resistance unit includes a thermistor with a positive temperature coefficient.

During implementation, the reference voltage supply unit includes a PWM control unit and at least one operational amplifier;

In the operational amplifier, the positive input terminal is connected to a predetermined reference voltage, the negative input terminal is connected to the second terminal of the LED backlight unit, the control terminal is connected to a pulse width modulation duty cycle signal, and the output terminal is connected to the PWM control unit connection;

The PWM control unit is used to generate LED driving voltage according to the output signal of the at least one operational amplifier.

The present invention also provides an LED backlight device, including an LED backlight circuit, the LED backlight circuit includes at least one LED backlight unit; the first end of the LED backlight unit is connected to the LED driving voltage, and the LED backlight device also includes The above-mentioned LED backlight driving circuit, the LED backlight driving circuit is used to drive the LED backlight circuit;

The second end of the at least one backlight unit is connected to the reference voltage supply unit included in the LED backlight drive circuit;

The second end of the LED backlight unit is also connected to the temperature compensation resistor unit included in the LED backlight driving circuit.

During implementation, the LED backlight circuit includes a red LED backlight unit, a green LED backlight unit and a blue LED backlight unit;

The red LED backlight unit includes a plurality of red LEDs connected in series in the same direction;

The green LED backlight unit includes a plurality of green LEDs connected in series in the same direction;

The blue LED backlight unit includes a plurality of blue LEDs connected in series in the same direction.

During implementation, the LED backlight circuit includes a single-color LED backlight unit;

The monochromatic LED backlight unit includes a plurality of monochromatic LEDs connected in series in the same direction, and the emitted colors of the plurality of monochromatic LEDs connected in series in the same direction are the same.

During implementation, the single-color LED is a red LED, a green LED, a blue LED or a white LED.

During implementation, the LED backlight unit includes a plurality of LED backlight modules connected in series;

Each LED backlight module includes at least two single-color LEDs connected in parallel in the same direction;

All the single-color LEDs in the LED backlight unit emit the same color.

The present invention also provides a display device, comprising the above-mentioned LED backlight device.

Compared with the prior art, the LED backlight driving circuit, LED backlight device and display device described in the present invention can ensure that the current flowing through the LED backlight unit is maintained within a certain range, thereby improving the reliability of the LED, reducing power consumption, and extending LED lifetime.

Description of drawings

1 is a structural diagram of an LED backlight drive circuit according to an embodiment of the present invention;

Fig. 2 is a circuit diagram of the LED backlight driving circuit described in a specific embodiment of the present invention;

3 is a structural diagram of a reference voltage supply unit included in the LED backlight driving circuit of the present invention;

4 is a circuit diagram of an LED backlight device according to an embodiment of the present invention;

FIG. 5 is a circuit diagram of an LED backlight device according to another embodiment of the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The LED backlight drive circuit described in the embodiment of the present invention is used to drive the LED backlight circuit, the LED backlight circuit includes at least one LED backlight unit, the first end of the LED backlight unit is connected to the LED drive voltage, and the LED backlight The drive circuit includes a reference voltage supply unit for providing a predetermined reference voltage to the second end of the at least one LED backlight unit, and the LED backlight drive circuit also includes at least one temperature compensation resistor unit;

The temperature compensation resistor unit is connected between the second terminal of the LED backlight unit and a level output terminal;

The resistance value of the temperature compensation resistance unit increases as the temperature increases, and the resistance value of the temperature compensation resistance unit decreases as the temperature decreases.

The LED backlight drive circuit, the LED backlight device and the display device of the present invention provide a temperature compensation unit whose resistance value increases as the temperature rises, and the voltage at both ends of the temperature compensation unit is fixed and flows through the temperature compensation unit The current is the driving current of the LED backlight unit. Therefore, when the temperature rises, the current flowing through the LED backlight unit decreases, thereby ensuring that the current flowing through the LED backlight unit is maintained within a certain range, thereby improving the reliability of the LED. Reduce power consumption and prolong the life of LED.

According to a specific implementation manner, as shown in FIG. 1, the LED backlight driving circuit described in the embodiment of the present invention is used to drive the LED backlight circuit;

The LED backlight circuit includes a red LED backlight unit R-LED, a green LED backlight unit G-LED and a blue LED backlight unit B-LED;

The red LED backlight unit R-LED includes a plurality of red LEDs connected in series in the same direction;

The green LED backlight unit G-LED includes a plurality of green LEDs connected in series in the same direction;

The blue LED backlight unit B-LED includes a plurality of blue LEDs connected in series in the same direction;

The anode end of the red LED backlight unit R-LED, the anode end of the green LED backlight unit G-LED and the anode end of the blue LED backlight unit B-LED are all connected to the LED anode drive voltage V _LED+ ;

The cathode terminal of the red LED backlight unit R-LED is connected to the red LED cathode driving voltage V _RLED- ;

The cathode terminal of the green LED backlight unit G-LED is connected to the cathode driving voltage V _GLED- of the green LED;

The cathode end of the blue LED backlight unit B-LED is connected to the blue LED cathode driving voltage V _BLED- ;

The red LED cathode driving voltage V _RLED- , the green LED cathode driving voltage V _GLED- and the blue LED cathode driving voltage V _BLED- are all provided by the reference voltage supply unit included in the LED backlight driving circuit (in FIG. 1 The reference voltage supply unit is not shown);

The LED backlight drive circuit also includes a first temperature compensation resistor unit 11, a second temperature compensation resistor unit 12 and a third temperature compensation resistor unit 13;

The first temperature compensation resistor unit 11 is connected between the cathode terminal of the red LED backlight unit R-LED and the ground terminal GND;

The second temperature compensation resistor unit 12 is connected between the cathode terminal of the green LED backlight unit G-LED and the ground terminal GND;

The third temperature compensation resistor unit 13 is connected between the cathode terminal of the blue LED backlight unit B-LED and the ground terminal GND;

The resistance value of the first temperature compensation resistance unit 11 increases as the temperature increases, and the resistance value of the first temperature compensation resistance unit 11 decreases as the temperature decreases;

The resistance value of the second temperature compensation resistance unit 12 increases as the temperature increases, and the resistance value of the second temperature compensation resistance unit 12 decreases as the temperature decreases;

The resistance value of the third temperature compensation resistance unit 13 increases as the temperature increases, and the resistance value of the third temperature compensation resistance unit 13 decreases as the temperature decreases;

In the embodiment shown in FIG. 1 , the LED backlight circuit is a light-mixing LED backlight circuit composed of a red LED backlight unit, a green LED backlight unit and a blue LED backlight unit.

In practice, the temperature compensation resistance unit includes an adjusting resistor and a thermistor connected in parallel; the thermistor has a positive temperature coefficient.

Specifically, as shown in FIG. 2, based on the embodiment of the LED backlight drive circuit shown in FIG. 1,

The first temperature compensation unit 11 includes a first resistor R1 and a first thermistor Rx1 connected in parallel;

The second temperature compensation unit 12 includes a second resistor R2 and a second thermistor Rx2 connected in parallel;

The third temperature compensation unit 13 includes a third resistor R3 and a third thermistor Rx3 connected in parallel;

Among them, the first thermistor Rx1, the second thermistor Rx2 and the third thermistor Rx3 are all thermistors with a positive temperature coefficient, and the characteristic is that the resistance value increases with the temperature rising, and the resistance value increases with the temperature reduce and decrease;

The equivalent resistance after the first thermistor Rx1 and the first resistance R1 are connected in parallel is represented by the first equivalent resistance R1';

The equivalent resistance after the second thermistor Rx2 and the second resistance R2 are connected in parallel is represented by the second equivalent resistance R2';

The equivalent resistance after the third thermistor Rx and the third resistance R3 are connected in parallel is represented by the third equivalent resistance R3';

R1'=R1//Rx1=R1×Rx1/(R1+Rx1);

R2'=R2//Rx2=R2×Rx2/(R2+Rx2);

R3'=R3//Rx3=R3×Rx3/(R3+Rx3);

It can be seen from the above formula that when the temperature rises, Rx1, Rx2, and Rx3 become larger, and R1', R2', and R3' also increase accordingly. The purpose of connecting ordinary resistors and thermistors in parallel here is to accurately Control the resistance value of the equivalent resistance;

Next, the adjustment process of the current flowing through the red LED backlight unit R-LED, the green LED backlight unit G-LED and the blue LED backlight unit B-LED is introduced:

First, a predetermined reference voltage V _REF is given as the red LED cathode driving voltage V _RLED- , the green LED cathode driving voltage V _GLED- and the blue LED cathode driving voltage V _BLED- ;

The other end of the first temperature compensation unit 11, the other end of the second temperature compensation unit 12 and the other end of the third temperature compensation unit 13 are all connected to the ground terminal GND;

Therefore, the current I _RLED flowing through the red LED backlight unit R-LED =V _REF /R1';

The current I _GLED flowing through the green LED backlight unit G-LED =V _REF /R2';

The current I _BLED flowing through the blue LED backlight unit B-LED =V _REF /R3';

When the temperature rises, Rx1, Rx2, and Rx3 become larger, and R1', R2', and R3' also increase accordingly. When the predetermined reference voltage V _REF is fixed, the red LED backlight unit R-LED The current I _RLED , the current I _GLED flowing through the green LED backlight unit G-LED, and the current I _BLED flowing through the blue LED backlight unit B-LED will all decrease accordingly, so that the current flowing through the LED backlight circuit will decrease accordingly. The purpose of decreasing as the temperature increases can effectively prolong the life of the LED and reduce power consumption.

In a specific implementation, the temperature compensation resistance unit may also only include a thermistor with a positive temperature coefficient.

During implementation, the reference voltage supply unit includes a PWM control unit and at least one operational amplifier;

In the operational amplifier, the positive input terminal is connected to a predetermined reference voltage, the negative input terminal is connected to the second terminal of the LED backlight unit, the control terminal is connected to a pulse width modulation duty ratio signal, and the output terminal is connected to the PWM control unit connection;

The PWM control unit is used to generate LED driving voltage according to the output signal of the at least one operational amplifier.

Specifically, as shown in FIG. 3 , it is used to provide a predetermined reference voltage V _REF for providing the red LED cathode driving voltage VRLED-, the green LED cathode driving voltage VGLED- and the blue LED cathode driving voltage V _BLED- The reference voltage supply unit consists of:

The first operational amplifier 21, the positive input terminal is connected to a predetermined reference voltage V _REF , the negative input terminal is connected to the cathode terminal of the red LED backlight unit (the red LED backlight unit is not shown in FIG. 3 ), and the control terminal is connected to PWM Duty (pulse width modulation duty ratio signal);

The second operational amplifier 22, the positive input terminal is connected to the predetermined reference voltage VREF, the negative input terminal is connected to the cathode terminal of the green LED backlight unit (the green LED backlight unit is not shown in Figure 3), and the control terminal is connected to the PWM. Duty (pulse width modulation duty ratio signal);

The positive input terminal of the third operational amplifier 23 is connected to a predetermined reference voltage VREF, the negative input terminal is connected to the cathode terminal of the blue LED backlight unit (the blue LED backlight unit is not shown in FIG. 3 ), and the control terminal is connected to PWM Duty (pulse width modulation duty cycle signal);

The pulse width modulation duty ratio signal is provided by the PWM control unit 24;

And, the PWM (Pulse Width Modulation, pulse width modulation) control unit 24, according to the output signal of the first operational amplifier 21, the output signal of the second operational amplifier 22 and the output signal of the third operational amplifier 23, Generate LED anode drive voltage V _LED+ .

The present invention also provides an LED backlight device, including an LED backlight circuit, the LED backlight circuit includes at least one LED backlight unit; the first end of the LED backlight unit is connected to the LED driving voltage, and the LED backlight device also includes The above-mentioned LED backlight driving circuit, the LED backlight driving circuit is used to drive the LED backlight circuit;

The second end of the at least one backlight unit is connected to the reference voltage supply unit included in the LED backlight drive circuit;

The second end of the LED backlight unit is also connected to the temperature compensation resistor unit included in the LED backlight driving circuit.

During implementation, the LED backlight circuit may include a red LED backlight unit, a green LED backlight unit, and a blue LED backlight unit. At this time, the LED backlight circuit is a light-mixing backlight circuit

The red LED backlight unit includes a plurality of red LEDs connected in series in the same direction;

The green LED backlight unit includes a plurality of green LEDs connected in series in the same direction;

The blue LED backlight unit includes a plurality of blue LEDs connected in series in the same direction.

During implementation, the LED backlight circuit may only include one single-color LED backlight unit;

The monochromatic LED backlight unit includes a plurality of monochromatic LEDs connected in series in the same direction, and the emitted colors of the plurality of monochromatic LEDs connected in series in the same direction are the same.

In practice, the single-color LED may be a red LED, a green LED, a blue LED or a white LED.

Specifically, as shown in FIG. 4, in the LED backlight device according to the embodiment of the present invention, the LED backlight circuit only includes one single-color LED backlight unit L1;

The monochromatic LED backlight unit L1 includes a plurality of monochromatic LEDs connected in series in the same direction, and the emitted colors of the plurality of monochromatic LEDs connected in series in the same direction are the same;

The LED backlight driving circuit includes a reference voltage supply unit (not shown in FIG. 4 ) and a temperature compensation resistance unit;

The anode end of the single-color LED backlight unit L1 is connected to the LEF anode drive voltage V _LED +;

The reference voltage providing unit provides an LED cathode driving voltage V _LED − for the cathode terminal of the single-color LED backlight unit L1;

The temperature compensation resistance unit includes a first resistor R1 connected in parallel with each other and a first thermistor Rx1 with a positive temperature coefficient;

One end of the temperature compensation resistance unit is connected to the cathode end of the single-color LED backlight unit L1, and the other end of the temperature compensation resistance unit is connected to the ground terminal GND;

In the embodiment of the LED backlight device shown in FIG. 4 , the single-color LED can be a red LED, a green LED, a blue LED or a white LED.

During implementation, the LED backlight unit may also include a plurality of LED backlight modules connected in series;

Each LED backlight module includes at least two single-color LEDs connected in parallel in the same direction;

All the single-color LEDs in the LED backlight unit emit the same color.

Specifically, as shown in FIG. 5, in the LED backlight device according to the embodiment of the present invention, the LED backlight circuit only includes one single-color LED backlight unit L2;

The single-color LED backlight unit L2 includes a plurality of LED backlight modules connected in series;

Each of the LED backlight modules includes two single-color LEDs connected in parallel in the same direction;

All monochromatic LEDs included in the monochromatic LED backlight unit have the same luminous color;

The LED backlight driving circuit includes a reference voltage supply unit (not shown in FIG. 4 ) and a temperature compensation resistance unit;

The anode terminal of the single-color LED backlight unit L2 is connected to the LEF anode drive voltage V _LED +;

The reference voltage providing unit provides an LED cathode driving voltage V _LED − for the cathode terminal of the single-color LED backlight unit L2;

The temperature compensation resistance unit includes a first resistor R1 connected in parallel with each other and a first thermistor Rx1 with a positive temperature coefficient;

One end of the temperature compensation resistance unit is connected to the cathode end of the single-color LED backlight unit L2, and the other end of the temperature compensation resistance unit is connected to the ground terminal GND.

The present invention also provides a display device, comprising the above-mentioned LED backlight device.

Specifically, the display device may include a liquid crystal display device, such as a liquid crystal panel, a liquid crystal TV, a mobile phone, and a liquid crystal display. In addition to the liquid crystal display device, the display device may also include other types of display devices, such as electronic readers and the like.

The above description is a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. A LED backlight drive circuit, used to drive the LED backlight circuit, the LED backlight circuit includes at least one LED backlight unit, the first end of the LED backlight unit is connected to the LED drive voltage, and the LED backlight drive circuit includes A reference voltage supply unit for providing a predetermined reference voltage to the second end of the at least one LED backlight unit, wherein the LED backlight drive circuit further includes at least one temperature compensation resistor unit; The temperature compensation resistor unit is connected between the second terminal of the LED backlight unit and a level output terminal; The resistance value of the temperature compensation resistance unit increases as the temperature increases, and the resistance value of the temperature compensation resistance unit decreases as the temperature decreases. 2. The LED backlight drive circuit according to claim 1, wherein the temperature compensation resistor unit comprises an adjusting resistor and a thermistor connected in parallel; The thermistor has a positive temperature coefficient. 3. The LED backlight driving circuit according to claim 1, wherein the temperature compensation resistor unit comprises a thermistor with a positive temperature coefficient. 4. The LED backlight drive circuit according to any one of claims 1 to 3, wherein the reference voltage supply unit comprises a PWM control unit and at least one operational amplifier; In the operational amplifier, the positive input terminal is connected to a predetermined reference voltage, the negative input terminal is connected to the second terminal of the LED backlight unit, the control terminal is connected to a pulse width modulation duty cycle signal, and the output terminal is connected to the PWM control unit connection; The PWM control unit is used to generate LED driving voltage according to the output signal of the at least one operational amplifier. 5. An LED backlight device, comprising an LED backlight circuit, the LED backlight circuit comprising at least one LED backlight unit; the first end of the LED backlight unit is connected to the LED driving voltage, and it is characterized in that the LED backlight device also Comprising the LED backlight driving circuit according to any one of claims 1 to 4, the LED backlight driving circuit is used to drive the LED backlight circuit; The second end of the at least one backlight unit is connected to the reference voltage supply unit included in the LED backlight drive circuit; The second end of the LED backlight unit is also connected to the temperature compensation resistor unit included in the LED backlight driving circuit. 6. The LED backlight device according to claim 5, wherein the LED backlight circuit comprises a red LED backlight unit, a green LED backlight unit and a blue LED backlight unit; The red LED backlight unit includes a plurality of red LEDs connected in series in the same direction; The green LED backlight unit includes a plurality of green LEDs connected in series in the same direction; The blue LED backlight unit includes a plurality of blue LEDs connected in series in the same direction. 7. The LED backlight device according to claim 5, wherein the LED backlight circuit comprises a single-color LED backlight unit; The monochromatic LED backlight unit includes a plurality of monochromatic LEDs connected in series in the same direction, and the emitted colors of the plurality of monochromatic LEDs connected in series in the same direction are the same. 8. The LED backlight device according to claim 7, wherein the single-color LED is a red LED, a green LED, a blue LED or a white LED. 9. The LED backlight device according to claim 5, wherein the LED backlight unit comprises a plurality of LED backlight modules connected in series in sequence; Each LED backlight module includes at least two single-color LEDs connected in parallel in the same direction; All the single-color LEDs in the LED backlight unit emit the same color. 10. A display device, characterized by comprising the LED backlight device according to any one of claims 5-9.