CN101754556B - Backlight modules and displays that include dimming control circuitry - Google Patents

Abstract

The backlight module comprises a dimming control circuit and a display. The dimming control circuit comprises a current switch, at least one resistor, a voltage switch, a level judgment circuit and a comparator. The current switch is used for selecting a current. The resistor is electrically connected to the current switch to generate a corresponding voltage value according to the current. The voltage switch is used for receiving the corresponding voltage value and outputting a reference voltage. The level judging circuit controls the current switch and the voltage switch according to the external input voltage. The comparator is used for receiving a feedback voltage and the reference voltage and outputting a brightness control signal. The invention also provides a backlight module and a display. The backlight module comprises the dimming control circuit, a light source and an inverter. The display comprises the backlight module and a display panel.

Description

Backlight modules and displays that include dimming control circuitry

technical field

The invention relates to a dimming control circuit, in particular to a dimming control circuit applied to a backlight module.

Background technique

Due to the vigorous development of optoelectronic technology, more and more opportunities to come into contact with various communication or electronic products in life, such as: personal digital assistant (personal digital assistant; PDA), mobile phone, notebook computer, desktop monitor, Car monitors and more. Among them, the display device is a common device for these communication or electronic products, so the quality of the display device is closely related to the quality of these communication or electronic products. Therefore, it is an urgent goal for the display device to have the advantages of high image quality, small size, light weight, low driving voltage, and low power consumption.

Generally speaking, current displays are equipped with a backlight module to provide backlight, and the backlight module is equipped with a dimming control circuit to control the brightness of the backlight.

Please refer to FIG. 1 , which is a schematic functional block diagram of a known backlight module 10 . The backlight module 10 includes a light source 12 , an inverter 14 , a pulse width modulation module (PWM module) 16 , a current detection device 18 and a dimming control circuit 20 , wherein the current detection device 18 is used to detect the working current of the light source 12 . In the backlight module 10, the brightness of the light source 12 is controlled by the inverter 14, the larger the current provided by the inverter 14, the stronger the brightness of the light source 12, on the contrary, if the current provided by the inverter 14 is smaller, the light source 12 is less bright. The dimming control circuit 20 is used for controlling the magnitude of the current output by the inverter 14 . The dimming control circuit 20 outputs the brightness control signal S _c according to the external signal S _r input by the user and the current detection signal S _f fed back by the current detection device 18, so as to use the brightness control signal S _c to control the inverter 14 output current. The pulse width modulation module 16 is electrically connected between the dimming control circuit 20 and the inverter 14 for modulating the brightness control signal S _c into a pulse signal and inputting it to the inverter 14 .

Please refer to FIG. 2 , which is a schematic circuit diagram illustrating a conventional dimming control circuit 20 . The dimming control circuit 20 includes a comparator 22 , resistors 24 , 26 , 28 and 30 . The positive terminal of the comparator 22 is used for receiving the external signal S _r input by the user. After the external signal S _r is input to the comparator 22 , the comparator 22 calculates the difference between the external signal S _r and the reference voltage V _r and outputs the difference to the resistor 28 . The resistor 30 is electrically connected to the current detection device 18 to receive the current detection signal S _f , and uses the resistor 28 to couple the difference between the current detection signal S _f and the output of the comparator 22 into a brightness control signal S _c .

It can be seen from the above description that the dimming control circuit 20 can make the value of the brightness control signal S _c change linearly with the value of the external signal S _r input by the user, so as to change the brightness of the light source 12 . Generally speaking, the user can only choose one of the three external signal S _r values to output, namely 0 volts, 1.6 volts and 3.3 volts, of which 1.6 volts corresponds to the standard brightness, 0 volts corresponds to the lower brightness, and 3.3 volts Volts correspond to higher brightness. Although the dimming control circuit 20 can make the value of the brightness control signal S _c change linearly with the value of the external signal S _r , when the value of the external signal S _r changes to a limited extent, the value of the brightness control signal S _c It is also limited, in other words, the resolution of the brightness that the light source 12 can display is relatively small, which cannot meet the needs of users.

Therefore, there is a need for a dimming control circuit capable of adjusting the current value corresponding to the external signal S _r to ensure that the resolution of the brightness of the light source can meet the needs of users.

Contents of the invention

Therefore, one aspect of the present invention is to provide a dimming control circuit, which can adjust the current value corresponding to the external signal according to the needs of users.

Another aspect of the present invention is to provide a backlight module, which can adjust the current value corresponding to the external signal according to the needs of users.

Another aspect of the present invention is to provide a display, which can adjust the current value corresponding to the external signal according to the needs of users.

According to an embodiment of the present invention, the dimming control circuit includes a current switching switch, at least one resistor, a voltage switching switch, a level judging circuit and a comparator. The current switching switch is used for selecting a current. The resistor is electrically connected to the current switching switch to generate a corresponding voltage value according to the current. The voltage switching switch is used for receiving the corresponding voltage value and outputting a reference voltage. The level judging circuit controls the current switching switch and the voltage switching switch according to the magnitude of the external input voltage. The comparator is used for receiving a feedback voltage and the reference voltage, and outputting a brightness control signal.

According to an embodiment of the present invention, the backlight module includes the above-mentioned dimming control circuit, a light source and an inverter, wherein the inverter is electrically connected between the light source and the dimming control circuit to control the output according to the brightness control signal. The magnitude of the current to the light source.

According to an embodiment of the present invention, the display includes the above-mentioned backlight module and a display panel, wherein the display panel is disposed on the backlight module for receiving light provided by the backlight module to display images.

Description of drawings

In order to make the above and other purposes, features, and advantages of the present invention more obvious and understandable, a preferred embodiment is specifically cited above, together with the accompanying drawings, as follows:

FIG. 1 is a schematic diagram illustrating a functional block of a known backlight module.

FIG. 2 is a schematic diagram illustrating a circuit structure of a known dimming control circuit.

FIG. 3 is a schematic diagram illustrating a circuit structure of a dimming control circuit according to an embodiment of the present invention.

FIG. 4 is a schematic diagram illustrating a circuit structure of a dimming control circuit according to an embodiment of the present invention.

FIG. 5 is a schematic functional block diagram of a backlight module according to an embodiment of the invention.

FIG. 6 is a schematic functional block diagram of a display 400 according to an embodiment of the present invention.

[Description of main component symbols]

10: Backlight module 12: Light source

14: Inverter 16: Pulse Width Modulation Module

18: Current detection device 20: Dimming control circuit

22: Comparator 24: Resistor

26: Resistance 28: Resistance

30: Resistor 100: Dimming control circuit

110: Current source 120: Current source

130: Current switch 150: Voltage switch

150a: Voltage input terminal 150b: Voltage input terminal

150c: Voltage output terminal 160: Level judging circuit

170: Comparator 300: Backlight module

310: Light source 320: Inverter

330: Pulse width modulation module 340: Current detection device

350: Dimming control circuit 400: Display

410: Display panel 420: Front frame

S _c : brightness control signal S _r : external signal

S _f : Detection signal V _A : Reference voltage

V _r : Reference voltage V _g : Reference voltage

I ₁ : Current I ₂ : Current

R1: Resistor R1a: Terminal

R1b: Terminal R2: Resistor

Detailed ways

Please refer to FIG. 3 , which is a schematic diagram illustrating a circuit structure of a dimming control circuit 100 according to an embodiment of the present invention. The dimming control circuit 100 includes a current source 110 , a current source 120 , a current switch 130 , a resistor R1 , a voltage switch 150 , a level judgment circuit 160 and a comparator 170 . The current switching switch 130 is electrically connected to the current source 110 and the current source 120 to output the first current I ₁ or the second current I ₂ , wherein the current source 110 is used to output the first current I ₁ , and the current source 120 is used to output the second current I ₂ . The resistor R1 is electrically connected to the current switching switch 130 to receive the first current or the second current output by the current switching switch 130, wherein the terminal R1a of the resistor R1 is electrically connected to the reference voltage V _g , and the terminal R1b is electrically connected to the Current changeover switch 130 . The voltage selector switch 150 has voltage input terminals 150a, 150b and a voltage output terminal 150c. The voltage input terminal 150a is electrically connected to the terminal R1b of the resistor R1, and the voltage input terminal 150b is electrically connected to the reference voltage V _r to output the reference voltage V _r or the voltage of the terminal R1b from the voltage output terminal 150c. The negative terminal of the comparator 170 is electrically connected to the voltage output terminal 150c _{of the voltage switching switch 150 , and the positive terminal is input with a feedback signal S f ,} such as a current feedback signal of the light source. The level judging circuit 160 is used to judge the magnitude of the external signal S _r input by the user, so as to determine the switching states of the current switching switch 130 and the voltage switching switch 150 . In the following description, how the dimming control circuit 100 adjusts the output brightness control signal S _c will be described.

From the above circuit connection relationship, it can be seen that when the constant current switching switch 130 outputs the first current _I1 , the terminal R1b of the resistor R1 will have a voltage level V _min , and when the current switching switch 130 outputs the second current _I2 , the terminal R1b R1b will have a voltage level V _max , where V _min =I ₁ *R1+V _g , and a voltage level V _max =I ₂ *R1+V _g . If the value of the first current I ₁ is set to be smaller than the value of the first current I ₂ , the value of the voltage level V _min will be smaller than the value of the voltage level V _max . Next, the value of the reference voltage V _r is designed to be between the voltage level V _max and the voltage level V _min , so that the level judging circuit 160 can control the current switching switch 130 and the voltage switching switch 150 according to the external signal S _r switching state, so that the voltage switching switch 150 outputs the reference voltage levels V _min , V _max and the reference voltage V _r . Then, the comparator 170 calculates the difference between the signal output by the voltage switching switch 150 and the feedback signal _Sf , and outputs the brightness control signal _Sc according to the difference.

From the above description, it can be seen that the value of the external signal S _r is properly corresponded to the voltage levels V _min , V _max and the reference voltage V _r , for example: when S _r =3.3 volts, the voltage switching switch 150 outputs the voltage level V _max ; When S _r =1.6 volts, the voltage switching switch 150 outputs the reference voltage V _r ; when S _r =0 volts, the voltage switching switch 150 outputs the voltage level V _min , so that the brightness control signal S _c can follow the external signal S _r changes, and this change is not a linear change. Furthermore, the user can easily change the values of the voltage levels V _min and V _max by changing the value of the resistor R1 , so that the value of the brightness control signal _Sc is more flexible.

In addition, it is worth mentioning that since the realization of the current source in the integrated circuit is quite easy, the current source 110, the current source 120, the current switching switch 130, the voltage switching switch 150, and the level judging circuit 160 can be It is integrated with the comparator 170 into one chip, and the resistor R1 is externally connected to the chip, so that not only the size of the dimming control circuit 100 can be greatly reduced, but also the value of the resistor R1 can be changed at any time according to the needs of users.

Please refer to FIG. 4 , which is a schematic diagram illustrating a circuit structure of a dimming control circuit 200 according to an embodiment of the present invention. The dimming control circuit 200 is similar to the dimming control circuit 100, but the difference is that the dimming control circuit 200 further includes a resistor R2, wherein one end of the resistor R2 is electrically connected to the terminal R1b of the resistor R1, and the other end is electrically connected to the terminal R1b of the resistor R1. Reference voltage V _A . In the dimming control circuit 200, since the resistor R2 is added, it can be obtained by Kirchhoff's law:

I ₂ +(V _A -V _min )/R1-(V _min -V _g )/R2＝0...........(1)

I ₁ +(V _A -V _max )/R1-(V _max -V _g )/R2＝0..........(2)

The values of V _min and V _max can be easily obtained from equations (1) and (2). In this embodiment, due to the influence of the resistor R2, the correlation between the voltage levels V _min and V _max decreases, thereby increasing the design flexibility of the voltage levels V _min and V _max .

Please refer to FIG. 5 , which is a schematic functional block diagram of a backlight module 300 according to an embodiment of the present invention. The backlight module 300 includes a light source 310, an inverter 320, a pulse width modulation module (PWMmodule) 330, a current detection device 340, and a dimming control circuit 350, wherein the dimming control circuit 350 can be, for example, the aforementioned dimming control circuit 100 or 200 . In the backlight module 300 , the inverter 320 is electrically connected to the light source 310 to provide current to the light source 310 to light the light source 310 . The pulse modulation module 330 is electrically connected between the dimming control circuit 350 and the inverter 320 for modulating the brightness control signal S _c into a pulse signal and inputting it to the inverter 320 . The current detection device 340 is used to detect the working current of the light source 310 and output the feedback signal S _f to the dimming control circuit 350 .

In this embodiment, since the aforementioned dimming control circuit 350 has the advantages of the dimming control circuit 100 or 200, the brightness of the backlight module 300 can be easily adjusted to the brightness required by the user.

Please refer to FIG. 6 , which is a schematic functional block diagram of a display 400 according to an embodiment of the present invention. The display 400 includes a backlight module 300 , a display panel 410 , and a front frame 420 . The backlight module 300 is used to provide light to the display panel 410 , and the display panel 410 is disposed on the backlight module 300 to use the light to display images. The front frame 420 is disposed on the display panel 410 and engaged with the outer edge of the backlight module 300 . Since the display 400 utilizes the backlight module 300 to provide a backlight, the brightness of the display 400 can be easily adjusted to the brightness required by the user.

Although the present invention has been disclosed above with the embodiments, it is not intended to limit the present invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection shall prevail as defined by the appended claims.

Claims (11)

1. an adjusting control circuit, receives an external input voltage and comprises:

One current changeover switch, in order to choose an electric current;

At least one resistance, is electrically connected to this current changeover switch and produces a corresponding magnitude of voltage according to this electric current;

One voltage changeover switch, receives this corresponding voltage value and one first reference voltage, and exports one second reference voltage;

One level judging circuit, controls this current changeover switch and this voltage changeover switch according to the size of this external input voltage, with so that this second reference voltage equals this corresponding voltage value or this first reference voltage; And

One comparator, the relatively difference between a feedback voltage and the second reference voltage, and export a brightness control signal according to the difference between this feedback voltage and this second reference voltage;

One first current source, is electrically connected to this current changeover switch, in order to one first electric current to be provided: and

One second current source, is electrically connected to this current changeover switch, in order to one second electric current to be provided;

Wherein this electric current is this first electric current or this second electric current.

2. adjusting control circuit as claimed in claim 1, wherein this current changeover switch, this voltage changeover switch, this level judging circuit and this comparator are integrated in an integrated circuit (IC) chip.

3. a backlight module, comprises:

One light source;

One converter, in order to provide electric energy to this light source; And

One adjusting control circuit, in order to export a brightness control signal according to the size of an input voltage, so that this converter is controlled the brightness of this light source according to a brightness control signal, wherein this adjusting control circuit comprises:

One current changeover switch, in order to choose an electric current;

At least one resistance, is electrically connected to this current changeover switch and produces a corresponding magnitude of voltage according to this electric current;

One voltage changeover switch, receives this corresponding voltage value and one first reference voltage, and exports one second reference voltage;

One level judging circuit, controls this current changeover switch and this voltage changeover switch according to the size of an external input voltage, with so that this second reference voltage equals this corresponding voltage value or this first reference voltage; And

One comparator, the relatively difference between a feedback voltage and the second reference voltage, and export a brightness control signal according to the difference between this feedback voltage and this second reference voltage;

One first current source, is electrically connected to this current changeover switch, in order to one first electric current to be provided; And

One second current source, is electrically connected to this current changeover switch, in order to one second electric current to be provided;

Wherein this electric current is this first electric current or this second electric current.

4. backlight module as claimed in claim 3, also comprises a current sensing means, exports this feedback voltage in order to detect the operating current of this light source.

5. backlight module as claimed in claim 3, also comprises a modulation module, in order to modulate this brightness control signal according to a default modulation condition, controls this converter to export a driving signal.

6. backlight module as claimed in claim 3, wherein this current changeover switch, this voltage changeover switch, this level judging circuit and this comparator are integrated in an integrated circuit (IC) chip.

7. a display, comprises:

One backlight module, comprises:

One light source;

One converter, in order to provide electric energy to this light source; And

One adjusting control circuit, in order to export a brightness control signal according to the size of an input voltage, so that this converter is controlled the brightness of this light source according to a brightness control signal, wherein this adjusting control circuit comprises:

One current changeover switch, in order to choose an electric current;

At least one resistance, is electrically connected to this current changeover switch and produces a corresponding magnitude of voltage according to this electric current;

One voltage changeover switch, receives this corresponding voltage value and one first reference voltage, and exports one second reference voltage;

One level judging circuit, controls this current changeover switch and this voltage changeover switch according to the size of an external input voltage, with so that this second reference voltage equals this corresponding voltage value or this first reference voltage; And

One comparator, the relatively difference between a feedback voltage and this second reference voltage, and export a brightness control signal according to the difference between this feedback voltage and this second reference voltage; And

One first current source, is electrically connected to this current changeover switch, in order to one first electric current to be provided: and

One second current source, is electrically connected to this current changeover switch, in order to one second electric current to be provided;

Wherein this electric current is this first electric current or this second electric current;

One display floater, is arranged on this backlight module, shows image in order to the light that receives this light source.

8. display as claimed in claim 7, also comprises a current sensing means, exports this feedback voltage in order to detect the operating current of this light source.

9. display as claimed in claim 7, also comprises a modulation module, in order to modulate this brightness control signal according to a default modulation condition, controls this converter to export a driving signal.

10. display as claimed in claim 7, also comprises a front frame, is arranged on this display floater, and is sticked in the outer rim of this backlight module.

11. displays as claimed in claim 7, wherein this current changeover switch, this voltage changeover switch, this level judging circuit and this comparator are integrated in an integrated circuit (IC) chip.