CN101276074A - Liquid crystal display, backlight module and light source driving control device thereof - Google Patents

Abstract

A light source driving control device drives a plurality of light emitting units and comprises a power supply unit and a feedback control unit. The power supply unit is electrically connected with the light-emitting unit and outputs a driving signal to drive the light-emitting unit. The feedback control unit is electrically connected between the power supply unit and any two light-emitting units, and captures a feedback signal of the light-emitting units to generate a pulse width modulation signal so as to control the light-emitting units.

Description

Liquid crystal display, backlight module and light source driving control device

technical field

The invention relates to a liquid crystal display, a backlight module and a light source driving control device thereof.

Background technique

Light Emitting Diode (LED) is widely used in daily life and electronic products due to its advantages of low power consumption, long life and good color saturation. It is gradually applied in the backlight module of the liquid crystal display as the source of the illumination source.

Please refer to FIG. 1 , which is a schematic circuit diagram of a conventional light source driving control device 1 , which includes a current supplier 11 , a LED string 12 , a comparator OP ₁ , a controller 13 and a switch 14 . The current supplier 11 outputs a current driving signal S ₁₁ to the LED string 12 . The comparator OP ₁ compares a current reference signal S ₁₃₁ with a current signal S ₁₂ extracted from the LED string 12, and outputs a comparison signal S ₁₃₂ to the controller 13 accordingly; the controller 13 receives the comparison The signal S ₁₃₂ is converted into a control signal S ₁₃ (for example: pulse width modulation signal) and output; the switch 14 is turned on (turn on) or cut off (turn off) according to the control signal S ₁₃ to control the The brightness of the LED string 12.

As mentioned above, the above method controls the brightness of the LED string 12 by comparing the current signal S ₁₂ obtained from the LED string 12 with the current reference signal S ₁₃₁ . However, using the current as the basis for controlling the light emission of the LED string 12 is easily affected by the instability of the current driving signal S11, resulting in a shift in the current level, so it is not easy to control the brightness of the LED string 12, and when the LED string 12 When the number of parallel connections increases, the power consumed by the resistor R connected in series with the light emitting diode string 12 in the light source driving control device 1 also increases accordingly, thus causing unnecessary power consumption.

Therefore, how to provide a liquid crystal display, a backlight module and a light source driving control device that can accurately control the brightness of the LED string and reduce power consumption is one of the important issues at present.

Contents of the invention

In view of the above problems, the object of the present invention is to provide a liquid crystal display, a backlight module and a light source driving control device thereof capable of accurately controlling the brightness of the LED string and reducing power consumption.

The reason is that, in order to achieve the above purpose, according to a light source drive control device of the present invention, which drives a plurality of light emitting units, the drive control device includes a power supply unit and a feedback control unit. The power supply unit is electrically connected to the light emitting unit, and outputs a driving signal to drive the light emitting unit. The feedback control unit is electrically connected between the power supply unit and any two light emitting units, and captures a feedback signal to generate a pulse width modulation signal to control the light emitting unit.

In addition, to achieve the above purpose, a backlight module according to the present invention includes a backplane and a light source driving control device. The backboard has an accommodating space, and the light source driving control device is arranged in the accommodating space, and drives a plurality of light emitting units. The light source drive control device includes a power supply unit and a feedback control unit. The power supply unit is electrically connected to the light emitting unit, and outputs a driving signal to drive the light emitting unit. The feedback control unit is electrically connected between the power supply unit and any two light emitting units, and captures a feedback signal to generate a pulse width modulation signal to control the light emitting unit.

Furthermore, to achieve the above purpose, a liquid crystal display according to the present invention includes a liquid crystal display panel and a backlight module having a light source driving control device, wherein the liquid crystal display panel is arranged on one side of the backlight module. The light source driving control device drives a plurality of light emitting units, and has a power supply unit and a feedback control unit. The power supply unit is electrically connected to the light emitting unit, and outputs a driving signal to drive the light emitting unit. The feedback control unit is electrically connected between the power supply unit and any two light emitting units, and captures a feedback signal to generate a pulse width modulation signal to control the light emitting unit.

Based on the above, the liquid crystal display, the backlight module and the light source driving control device of the present invention use the feedback control unit to be electrically connected between any two light emitting units to capture the feedback signal. Compared with the existing ones, the present invention can obtain the required feedback signal through the simple design of the feedback control unit, so as to accurately control the brightness of the light emitting unit and reduce unnecessary power consumption caused by current feedback control.

Description of drawings

FIG. 1 is a schematic circuit diagram of an existing light source drive control device;

2 is a schematic block diagram of a light source drive control device according to a preferred embodiment of the present invention;

3 is a schematic circuit diagram of a light source drive control device according to a preferred embodiment of the present invention; and

FIG. 4 is a schematic structural diagram of a liquid crystal display device according to a preferred embodiment of the present invention.

Explanation of reference symbols:

1 Light source driving control device 11 Current supplier

12 LED String 13 Controller

14 Switch 2 2 Light source drive control device

21 Power Supply Unit 22 Feedback Control Unit

221 Voltage divider circuit 222 Comparison circuit

223 Pulse Width Modulation Circuit 224 Filter Circuit

23 Switch Unit 24 Temperature Sensing Control Unit

3 Liquid Crystal Display 31 Liquid Crystal Display Panel

311 incident surface 32 backlight module

321 Backplane 322 Light source drive control device

323 Diffusion Plate C Capacitance

J ₁ Oscillator L ₁ , L ₂ Lighting unit

OP ₁ , U ₁ , U ₂ Comparator R, R ₁ -R ₃ , RT Resistor

Q ₁ -Q ₃ switch assembly

S ₁₁ Current drive signal S ₁₂ Current signal

S ₁₃ Control signal S ₁₃₁ Current reference signal

S ₁₃₂ comparison signal S ₂₁ drive signal

S ₂₂ Feedback signal S ₂₂₁ Reference voltage signal

S ₂₂₂ comparison signal S ₂₂₃ oscillation signal

S ₂₃ Pulse Width Modulation Signal S ₂₄ Sensing Control Signal

SP ₁ storage space

Detailed ways

The liquid crystal display, the backlight module and the light source driving control device thereof according to the preferred embodiments of the present invention will be described below with reference to related drawings.

Please refer to FIG. 2 and FIG. 3 , wherein FIG. 2 is a schematic block diagram of a light source driving control device 2 of the present invention, and FIG. 3 is a circuit schematic diagram of the light source driving control device 2 in FIG. 2 .

The light source driving control device 2 drives a plurality of light emitting units L ₁ , and the light source driving control device 2 includes a power supply unit 21 , a feedback control unit 22 , a switch unit 23 and a temperature sensing control unit 24 . In this embodiment, the light emitting unit _L1 can be implemented as a light emitting diode.

The power supply unit 21 outputs a driving signal S ₂₁ to the light emitting unit L ₁ and the feedback control unit 22 . The feedback control unit 22 is electrically connected between any two light emitting units L ₁ to capture a feedback signal S ₂₂ and output a pulse width modulation signal S ₂₃ accordingly. The temperature sensing unit 24 senses an ambient temperature to Generate a sensing control signal S ₂₄ . The switch unit 23 controls the current flowing through the light emitting unit _L1 according to the pulse width modulation signal _S23 and the sensing control signal _S24 , so as to regulate the brightness of the light emitting unit _L1 . In this embodiment, the driving signal S ₂₁ , the feedback signal S ₂₂ , the pulse width modulation signal S ₂₃ and the sensing control signal S ₂₄ are each a voltage signal.

Please refer to FIG. 3 again, the feedback control unit 22 has a voltage divider circuit 221 , a comparison circuit 222 and a pulse width modulation circuit 223 .

The voltage dividing circuit 221 has a first resistor R ₁ and a second resistor R ₂ , and the first resistor R ₁ and the second resistor R ₂ are connected in series between the power supply unit 21 and a ground between the ends. The voltage dividing circuit 221 divides the driving signal S ₂₁ output by the power supply unit 21 to generate a reference voltage signal S ₂₂₁ .

The comparison circuit 222 has a first comparator U ₁ , and the first comparator U ₁ compares the feedback signal S ₂₂ and the reference voltage signal S ₂₂₁ to output a comparison signal S ₂₂₂ . In this embodiment, the first comparator _U1 is an operational amplifier or any component or circuit with a comparison function, and the reference voltage signal _S221 and the comparison signal _S222 are respectively a voltage signal.

The pulse width modulation circuit 223 has an oscillator J ₁ and a second comparator U ₂ . The oscillator J ₁ outputs an oscillating signal S ₂₂₃ to the second comparator U ₂ , and the second comparator U ₂ compares the oscillating signal S ₂₂₃ and the comparison signal S ₂₂₂ , and outputs the pulse width modulation signal accordingly _S23 . Wherein, the oscillating signal _S223 can be a triangle wave or a sawtooth wave. In addition, the second comparator _U2 is an operational amplifier or any component or circuit with a comparison function.

It should be noted that it is a mature technology to use electronic components to achieve the function of the pulse width modulation circuit 223. Here, the pulse width modulation circuit 223 composed of the comparator U2 and the oscillator J1 is taken as an example, but it does not Not limited thereto, the control chip can also be used to achieve the above functions that the pulse width modulation circuit 223 can achieve.

The switch unit 23 has a first switch component Q ₁ , a second switch component Q ₂ and a third switch component Q ₃ . Wherein the first switch component _Q1 is electrically connected to the light emitting unit _L1 and the second switch component _Q2 respectively, and the second switch component _Q2 is electrically connected to the first switch component _Q1 and the third switch component respectively Q ₃ , the third switch component Q ₃ is electrically connected to the second switch component Q ₂ , the feedback control circuit 22 and the temperature sensing control unit 24 respectively. In this embodiment, the above-mentioned switching components Q ₁ -Q ₃ can be respectively a BJT, a MOSFET or any component or circuit with a switching function.

Referring to FIG. 3 again, the power supply unit 21 outputs the driving signal S ₂₁ , and the voltage dividing circuit 221 in the feedback control unit 22 receives the driving signal S ₂₁ and outputs the reference voltage signal S ₂₂₁ . The first comparator U ₁ in the comparison circuit 222 compares the reference voltage signal S ₂₂₁ and the feedback signal S ₂₂ obtained between any two light-emitting units L ₁ to output the comparison signal S ₂₂₂ to the pulse width The second comparator U ₂ of the modulation circuit 223 . The second comparator U ₂ compares the oscillation signal S ₂₂₃ output by the oscillator J ₁ with the comparison signal S ₂₂₂ output by the first comparator U ₁ to output the pulse width modulation signal S ₂₃ . The pulse width modulation signal S ₂₃ is transmitted to the first switch component Q 1 via the third switch component Q ₃ and the second switch component Q ₂ , and accordingly controls the first switch component Q ₁ to be turned on or off _. . The current value flowing through the light-emitting unit _L1 is regulated by turning on or off the first switch unit _Q1 , so as to control the brightness of the light-emitting unit _L1 .

Wherein, the second switch unit _Q2 connected in series with the third switch unit _Q3 has the function of an AND circuit, which can be used to detect whether the light-emitting unit _L1 is operating normally. When the switch units Q ₂ and Q ₃ are turned on at the same time, the pulse width modulation signal S ₂₃ can be transmitted to the first switch component Q ₁ ; if one of the switch units Q ₂ and Q ₃ is turned off, then The PWM signal S ₂₃ cannot be transmitted to the first switch element Q ₁ . In addition, when the light-emitting unit _L1 is abnormal due to factors such as disconnection or overheating, the second switch unit _Q2 will also be cut off, causing the feedback control unit 22 and the switch unit 23 to be disconnected, so that The PWM signal _S23 cannot be transmitted to achieve the function of circuit protection.

In this embodiment, in order to prevent the feedback signal S ₂₂ from carrying noise and causing the feedback control unit 22 to malfunction, the feedback control circuit 22 may further include a filter circuit 224 . The filter circuit 224 receives and filters the feedback signal _S22 between any two light emitting units _L1 . In this embodiment, the filter circuit 224 is a low-pass filter circuit composed of a third resistor _R3 and a capacitor C. However, there are many implementations of the low-pass filter circuit, which are just examples here, and are not limited to only RC low-pass filter circuits.

The temperature sensing and control unit 24 may have a thermistor RT (as shown in the figure), a thermocouple (Thermocopuler) or any component that can generate the sensing control signal S ₂₄ according to the change of the ambient temperature. Wherein, the thermistor RT can be a positive temperature coefficient thermistor or a negative temperature coefficient thermistor.

In this embodiment, in order to protect the light source drive control device 2, when the thermistor RT of the temperature sensing control unit 24 senses that the temperature of the external environment is too high, the temperature sensing control unit 24 will output the The sensing control signal S ₂₄ is sent to the third switch component Q ₃ , and the third switch component Q ₃ is turned off, causing the feedback control unit 22 and the switch unit 23 to be disconnected, thereby automatically cutting off the circuit of the light source driving control device 2 , to achieve the functions of temperature sensing and circuit protection.

Next, please refer to FIG. 4 to illustrate the backlight module and the liquid crystal display of the preferred embodiment of the present invention.

4 is a schematic structural diagram of a liquid crystal display 3 of the present invention, the liquid crystal display 3 includes a liquid crystal display panel 31 and a backlight module 32, wherein the liquid crystal display panel 31 and the backlight module 32 are arranged opposite to each other. In this embodiment, the backlight module 32 is an example of a direct type backlight module.

The backlight module 32 has a backplane 321 , a light source driving control device 322 and a diffusion plate 323 . Wherein, the back plate 321 has an accommodating space SP ₁ , and the light source driving control device 322 is disposed in the accommodating space SP ₁ and drives a plurality of light emitting units L ₂ . The light emitting units L ₂ respectively emit a light diffused by the diffusion plate 323 and enter the light incident surface 311 of the liquid crystal display panel 31 to provide the light source required by the liquid crystal display panel 31 .

In this embodiment, the light source driving control device 322 of the backlight module 32 can be the light source driving control device 2 described in the previous embodiment, and the light emitting unit _L2 can have the same structure as the light emitting unit _L1 of the above embodiment. function, structure and setting relationship, so no more details here.

It is worth mentioning that, in this embodiment, the backlight module 32 is not limited to be a direct-lit backlight module, and of course it can also be a side-lit backlight module. In addition, the structural configuration of the light source driving control device 322 is only exemplary, and is not limited to the structural configuration shown in FIG. Just connect the relationship.

To sum up, the liquid crystal display, the backlight module and the light source driving control device of the present invention use the feedback control unit to be electrically connected between any two light emitting units to capture the feedback signal. Compared with the prior art, the present invention can obtain the required feedback signal through the simple design of the feedback control unit, so as to accurately control the brightness of the light emitting unit and reduce unnecessary power consumption caused by current feedback control .

The above descriptions are illustrative only, not restrictive. Any equivalent modification or change made without departing from the spirit and scope of the present invention shall be included in the patent application scope of the present invention.

Claims (22)

1. A light source driving control device, which drives a plurality of light emitting units, the light source driving control device comprising: a power supply unit electrically connected to the light emitting unit, and outputs a driving signal to drive the light emitting unit; and A feedback control unit is electrically connected between the power supply unit and any two light emitting units, and captures a feedback signal to generate a pulse width modulation signal to control the light emitting unit. 2. The light source driving control device as claimed in claim 1, wherein the feedback signal, the driving signal or the pulse width modulation signal is a voltage signal. 3. The light source driving control device as claimed in claim 1, wherein the feedback control unit has a voltage divider circuit electrically connected to the power supply unit to generate a reference voltage signal. 4. The light source driving control device as claimed in claim 3, wherein the voltage divider circuit has a first resistor and a second resistor connected in series. 5. The light source drive control device as claimed in claim 3, wherein the feedback control unit further has a comparison circuit, which is electrically connected to the voltage dividing circuit and the light emitting unit, and compares the reference voltage signal and the feedback signal to generate a comparison signal or a voltage signal. 6. The light source driving control device as claimed in claim 5, wherein the comparison circuit comprises an operational amplifier. 7. The light source drive control device as claimed in claim 1, wherein the feedback control circuit further has a filter circuit or a low-pass filter, which is electrically connected to the light emitting unit and filters the feedback signal . 8. The light source driving control device as claimed in claim 7, wherein the filter circuit has a third resistor and a capacitor. 9. The light source drive control device as claimed in claim 5, wherein the feedback control unit further has a pulse width modulation circuit or a control chip, which is electrically connected to the comparison circuit and the light emitting unit, and compares the The signal is converted to this pulse width modulated signal. 10. The light source driving control device as claimed in claim 9, wherein the pulse width modulation circuit has an operational amplifier and an oscillator, wherein the oscillator generates an oscillation signal, and the operational amplifier compares the oscillation signal with the The signals are compared to generate the pulse width modulated signal. 11. The light source driving control device as claimed in claim 1, further comprising a switch unit electrically connected to the light emitting unit and the feedback control unit respectively. 12. The light source driving control device as claimed in claim 11 , further comprising a temperature sensing unit electrically connected to the switch unit, the temperature sensing unit sensing an ambient temperature to generate a sensing signal or a The voltage signal is used to control the light emitting unit through the switch unit. 13. The light source driving control device as claimed in claim 12, wherein the temperature sensing unit comprises a thermistor or a thermocouple. 14. The light source driving control device according to claim 12, wherein the switch unit has a first switch assembly, a second switch assembly and a third switch assembly, and the first switch assembly is electrically connected to the The light emitting unit and the second switch assembly, the second switch assembly is electrically connected to the first switch assembly and the third switch assembly, the third switch assembly is electrically connected to the second switch assembly, the feedback control circuit and the temperature sensing control unit. 15. The light source driving control device according to claim 14, wherein the second switch unit is connected in series with the third switch unit to form an AND gate circuit. 16. The light source driving control device according to claim 14 , wherein the switching components are respectively a transistor, a bipolar junction transistor or a metal oxide semiconductor field effect transistor. 17. The light source drive control device according to claim 1, wherein the light emitting unit is a light emitting diode. 18. A backlight module, comprising: a backboard with an accommodating space; and A light source driving control device is arranged in the accommodating space and drives a plurality of light emitting units. The light source driving control device has a power supply unit and a feedback control unit, wherein the power supply unit is electrically connected to the light emitting unit, and output a drive signal to drive the light emitting unit, the feedback control unit is electrically connected between the power supply unit and any two light emitting units, and captures a feedback signal to generate a pulse width modulation signal to control the Lighting unit. 19. The backlight module as claimed in claim 18, further comprising a diffuser plate. 20. A liquid crystal display comprising: a liquid crystal display panel; and A backlight module is arranged on one side of the liquid crystal display panel, wherein the backlight module has a light source drive control device, the light source drive control device drives a plurality of light emitting units, and has a power supply unit and a feedback control unit, wherein , the power supply unit is electrically connected to the light emitting unit, and outputs a driving signal to drive the light emitting unit, the feedback control unit is electrically connected between the power supply unit and any two light emitting units, and captures a feedback signal to generate a pulse width modulation signal to control the light emitting unit. 21. The liquid crystal display as claimed in claim 20, wherein the backlight module further comprises a back plate having an accommodating space for the light source driving device to be disposed. 22. The liquid crystal display as claimed in claim 20 , wherein the backlight module further comprises a diffusion plate, and each of the light emitting units respectively emits a light diffused through the diffusion plate and enters a light incident surface of the liquid crystal display panel.

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