TWI390299B - Backlight module and display including dimming control circuit - Google Patents

Description

Backlight module and display including dimming control circuit

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

Due to the rapid development of optoelectronic technology, more and more opportunities in life are exposed to a variety of communication or electronic products, such as: personal digital assistant (PDA), mobile phones, notebook computers, desktop displays, Car monitors and more. Among them, the display device is a device that should be commonly used in these communication or electronic products, so the advantages and disadvantages of the display device are related to the advantages and disadvantages of these communication or electronic products. Therefore, the display device can have the advantages of high image quality, small size, light weight, low driving voltage, and low power consumption.

In general, current displays are equipped with a backlight module to provide backlighting, 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 functional block diagram of a conventional 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 detecting device 18, and a dimming control circuit 20, wherein the current detecting device 18 is configured to detect The operating current of the light source 12 is measured. In the backlight module 10, the brightness of the light source 12 is controlled by the inverter 14, the greater the current supplied by the inverter 14, the stronger the brightness of the light source 12, and conversely, the smaller the current supplied by the inverter 14. The brightness of the light source 12 is smaller. The dimming control circuit 20 is 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 detecting signal S _f sent back by the current detecting device 18 to control the brightness control signal S _c . The current output by the streamer 14. The pulse width modulation module 16 is electrically connected between the dimming control circuit 20 and the inverter 14 for converting 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 diagram showing the circuit structure of the 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 for receiving an 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 detecting device 18 to receive the current detecting signal S _f , and the resistor 28 is used to couple the difference between the current detecting signal S _f and the output of the comparator 22 into the brightness control signal S _c .

As can be seen from the above description, the dimming control circuit 20 can linearly change the value of the brightness control signal S _{c according to} the value of the external signal S _r input by the user to change the brightness of the light source 12 . In general, the user can only select one of three external signal S _r values, namely 0 volts, 1.6 volts and 3.3 volts, of which 1.6 volts corresponds to standard brightness and 0 volts corresponds to lower brightness, and 3.3 volts corresponds to a higher brightness. Although, the dimming control circuit 20 may control the value of the luminance signal S _c as the value of the external signal S _r varies linearly, but the value of the external signal S _r changes limited circumstances, the luminance value of the control signal S _c It is also limited. In other words, the resolution of the brightness that the light source 12 can exhibit is relatively small, and cannot meet the needs of the user.

Therefore, there is a need for a dimming control circuit that can adjust 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 the user.

Accordingly, an aspect of the present invention provides a dimming control circuit that adjusts a current value corresponding to an external signal according to a user's needs.

Another aspect of the present invention provides a backlight module that can adjust a current value corresponding to an external signal according to a user's needs.

Still another aspect of the present invention provides a display that adjusts a current value corresponding to an external signal according to a user's needs.

According to an embodiment of the invention, the dimming control circuit comprises a current switching switch, at least one resistor, a voltage switching switch, a level determining circuit and a comparator. The current switching relationship is used to select a current. The resistor is electrically connected to the current switch to generate a corresponding voltage value according to the current. The voltage switching on relationship is for receiving the corresponding voltage value and outputting a reference voltage. The level determining circuit controls the current switching switch and the voltage switching switch according to the magnitude of the external input voltage. The comparator is configured to receive a feedback voltage and the reference voltage, and output a brightness control signal.

According to an embodiment of the present invention, the backlight module includes the dimming control circuit, the light source and the inverter, wherein the inverter is electrically connected between the light source and the dimming control circuit to control the signal according to the brightness. Controls the amount of current output to the light source.

According to an embodiment of the present invention, the display includes the backlight module and a display panel, wherein the display panel is disposed on the backlight module to receive the light provided by the backlight module to display the image.

Please refer to FIG. 3, which is a schematic diagram showing the circuit structure of the dimming control circuit 100 according to an embodiment of the invention. The dimming control circuit 100 includes a current source 110, a current source 120, a current switching switch 130, a resistor R1, a voltage switching switch 150, a level determining circuit 160, and a comparator 170. The current switch 130 is electrically connected to the current source 110 and the current source 120 to output a first current I ₁ or a second current I ₂ , wherein the current source 100 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 switch 130 to receive the first current or the second current output by the current switch 130, wherein the end point R1a of the resistor R1 is electrically connected to the reference voltage V _g , and the end point R1b It is electrically connected to the current switch 130. The voltage 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 _Vr to output the voltage of the reference voltage _Vr or the terminal R1b from the voltage output terminal 150c. The negative terminal of comparator 170 is electrically connected to the line voltage switching voltage output terminal 150 of the switch 150c, and the positive input terminal of a feedback signal were S _f, S _f This feedback signal may be, for example, a light source of a current feedback signal. The level determining circuit 160 is configured to determine the magnitude of the external signal S _r input by the user to determine the switching state of the current switching switch 130 and the voltage switching switch 150. In the following description, how the dimming control circuit 100 adjusts its output luminance control signal S _c will be explained.

From the above circuit connection relationship, when the constant current is switched to _1, the terminal of the resistor R1 of the output switch 130 appear R1b first current I voltage level V _min, when the switch 130 switches the output current of the second current I _2, the The voltage level V _max occurs at the end point R1b, where V _min = I _{1 *} R1 + V _g and the 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 may be less than the value of the voltage level V _max . Then, 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 determining circuit 160 can control the current switching switch 130 and the voltage switching switch 150 according to the external signal S _r . switching state, the changeover switch 150 so that the output voltage of the reference voltage level 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 S _f , and outputs the brightness control signal S _c according to the difference.

As can be seen from the above description, when the value of the external signal S _r is appropriately mapped to the voltage levels V _min , V _max and the reference voltage V _r , for example, 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 The change changes, and the change is not a linear change. Further, the user may easily change voltage level value V _min and V _max values by replacing the resistor R1, such that the value of the brightness control signal S _c is more flexible.

In addition, as a result of the value, since the implementation of the current source is relatively easy in the integrated circuit, the current source 110, the current source 120, the current switching switch 130, the voltage switching switch 150, and the level determining circuit can be used. The 160 and the comparator 170 are integrated into one wafer, and the resistor R1 is externally connected to the wafer, so that the volume of the dimming control circuit 100 can be greatly reduced, and The value of the resistor R1 can be changed at any time by the user's needs.

Please refer to FIG. 4, which is a schematic diagram showing the circuit structure of the dimming control circuit 200 according to an embodiment of the invention. The dimming control circuit 200 is similar to the dimming control circuit 100, but the dimming control circuit 200 further includes a resistor R2, wherein one end of the resistor R2 is electrically connected to the end point R1b of the resistor R1, and the other end is Electrically connected to the 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) V _min and V _max can be easily obtained from equations (1) and (2) value. In the present embodiment, since the influence of the resistor R2, so that the voltage level V _max and V _min correlated with each other decreases, thereby increasing the elasticity of the voltage level V _min and V _max design.

Please refer to FIG. 5 , which is a functional block diagram of a backlight module 300 according to an embodiment of the invention. The backlight module 300 includes a light source 310, an inverter 320, a pulse width modulation module (PWM module) 330, a current detecting device 340, and a dimming control circuit 350. The dimming control circuit 350 can be, for example, the dimming described above. 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 illuminate the light source 310. The pulse modulation module 330 is electrically connected between the dimming control circuit 350 and the inverter 320 for converting the brightness control signal S _c into a pulse signal and inputting it to the inverter 320. The current detecting device 340 is configured to detect the operating current of the light source 310 and output the feedback signal S _f to the dimming control circuit 350.

In this embodiment, since the 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 desired by the user.

Please refer to FIG. 6 , which is a functional block diagram of a display 400 according to an embodiment of the invention. The display 400 includes a backlight module 300, a display panel 410, and a front frame 420. The backlight module 300 is configured to provide light to the display panel 410, and the display panel 410 is disposed on the backlight module 300 to display the image by using the light. The front frame 420 is disposed on the display panel 410 and is 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 desired by the user.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and the present invention can be modified and retouched without departing from the spirit and scope of the present invention. The scope is subject to the definition of the scope of the patent application attached.

10‧‧‧Backlight module

12‧‧‧Light source

14‧‧‧Inverter

16‧‧‧ pulse width modulation module

18‧‧‧ Current detecting device

20‧‧‧ dimming control circuit

22‧‧‧ Comparator

24‧‧‧resistance

26‧‧‧resistance

28‧‧‧resistance

30‧‧‧resistance

100‧‧‧ dimming control circuit

110‧‧‧current source

120‧‧‧current source

130‧‧‧current switch

150‧‧‧Voltage switch

150a‧‧‧voltage input

150b‧‧‧voltage input

150c‧‧‧voltage output

160‧‧‧Level judgment circuit

170‧‧‧ comparator

300‧‧‧Backlight module

310‧‧‧Light source

320‧‧‧Inverter

330‧‧‧ pulse width modulation module

340‧‧‧ Current detecting device

350‧‧‧ dimming control circuit

400‧‧‧ display

410‧‧‧ display panel

420‧‧‧ front box

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‧‧‧ resistance

R1a‧‧‧ endpoint

R1b‧‧‧ endpoint

R2‧‧‧ resistance

The above and other objects, features and advantages of the present invention will become more <RTIgt; Functional block diagram of the backlight module.

FIG. 2 is a schematic diagram showing the circuit structure of a conventional dimming control circuit.

3 is a diagram showing a dimming control circuit according to an embodiment of the present invention. Schematic diagram of the circuit structure.

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

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

FIG. 6 is a functional block diagram of a display 400 in accordance with an embodiment of the present invention.

100‧‧‧ dimming control circuit

110‧‧‧current source

120‧‧‧current source

130‧‧‧current switch

150‧‧‧Voltage switch

150a‧‧‧voltage input

150b‧‧‧voltage input

150c‧‧‧voltage output

160‧‧‧Level judgment circuit

170‧‧‧ comparator

R1‧‧‧ resistance

R1a‧‧‧ endpoint

R1b‧‧‧ endpoint

R2‧‧‧ resistance

V _A ‧‧‧reference voltage

V _g ‧‧‧reference voltage

V _r ‧‧‧reference voltage

S _r ‧‧‧External signal

S _c ‧‧‧Brightness control signal

S _f ‧‧‧detection signal

I ₁ ‧‧‧ Current

I ₂ ‧‧‧current

Claims (14)

A dimming control circuit receives an external input voltage and includes: a current switching switch for selecting a current; at least one resistor electrically connected to the current switching switch and generating a corresponding voltage value according to the current; The voltage switching switch receives the corresponding voltage value and a first reference voltage, and outputs a second reference voltage; a level determining circuit controls the current switching switch and the voltage switching switch according to the magnitude of the external input voltage, The second reference voltage is used to equal the corresponding voltage value or the first reference voltage; and a comparator receives a feedback voltage and the reference voltage, and outputs a brightness control signal. The dimming control circuit of claim 1, further comprising: a first current source electrically connected to the current switching switch for providing a first current; and a second current source, electrically Connected to the current switch to provide a second current; wherein the current is the first current or the second current. The dimming control circuit of claim 1, wherein the current switching switch, the voltage switching switch, the level determining circuit and the comparator are integrated into an integrated circuit chip. A backlight module comprising: a light source; an inverter for supplying electric energy to the light source; and a dimming control circuit for outputting a brightness control signal according to an input voltage, so that the converter is based on a brightness control signal Controlling the brightness of the light source, wherein the dimming control circuit comprises: a current switching switch for selecting a current; at least one resistor electrically connected to the current switching switch and generating a corresponding voltage value according to the current; The switch is configured to receive the corresponding voltage value and a first reference voltage, and output a second reference voltage; a level determining circuit controls the current switch and the voltage switch according to an external input voltage, The second reference voltage is equal to the corresponding voltage value or the first reference voltage; and a comparator receives a feedback voltage and the reference voltage, and outputs a brightness control signal. The backlight module of claim 4, wherein the dimming control circuit further comprises: a first current source electrically connected to the current switch to provide a first current; and a second And a current source electrically connected to the current switch to provide a second current; wherein the current is the first current or the second current. The backlight module of claim 4, further comprising a current detecting device for detecting an operating current of the light source to output the feedback voltage. The backlight module of claim 4, further comprising a modulation module for modulating the brightness control signal according to a preset modulation condition to output a driving signal to control the converter . The backlight module of claim 4, wherein the current switching switch, the voltage switching switch, the level determining circuit and the comparator are integrated into an integrated circuit chip. A display comprising: a backlight module comprising: a light source; an inverter for supplying electrical energy to the light source; and a dimming control circuit for outputting a brightness control signal according to an input voltage The dimmer controls the brightness of the light source according to a brightness control signal, wherein the dimming control circuit comprises: a current switching switch for selecting a current; and at least one resistor electrically connected to the current switching switch And generating a corresponding voltage value according to the current; a voltage switching switch receives the corresponding voltage value and a first reference voltage, and outputs a second reference voltage; a level determining circuit, according to an external input voltage Controlling the current switch and the voltage switch to make the second reference voltage equal to the corresponding voltage value or the first reference voltage; and a comparator receiving a feedback voltage and the reference voltage, and outputting a a brightness control signal; and a display panel disposed on the backlight module for receiving light of the light source to display an image. The display device of claim 9, wherein the dimming control circuit further comprises: a first current source electrically connected to the current switch to provide a first current; and a second current source And electrically connected to the current switch to provide a second current; wherein the current is the first current or the second current. The display of claim 9, further comprising a current detecting device for detecting an operating current of the light source to output the feedback voltage. The display device of claim 9, further comprising a modulation module for modulating the brightness control signal according to a preset modulation condition to output a driving signal to control the converter. The display device of claim 9, further comprising a front frame disposed on the display panel and engaged with the outer edge of the backlight module. The display of claim 9, wherein the current switch, the voltage switch, the level determining circuit and the comparator are integrated into an integrated circuit chip.