TWI431599B - Image processing circuit and light illumination module - Google Patents

Description

Image processing circuit and light emitting module

The present invention relates to an image processing circuit and a light emitting module, and more particularly to an image processing circuit for controlling a backlight of a liquid crystal display and a light emitting module for providing a backlight of the liquid crystal display.

The use of Light Emitting Diodes (LEDs) as illumination sources is becoming more and more popular, such as liquid crystal displays, mobile phones, portable computers and personal digital assistants. The backlight module is a key component of the driving light source in the display, which not only determines the reliability and stability of the display, but also directly affects the display quality of the display.

In general, in order to allow the user to adjust the brightness of the light source according to the preference or to save more power under the permission of the ambient brightness, it is necessary to have a good dimming function. In view of the physical properties of the light-emitting diode, the current through the light-emitting diode is exponentially related to the forward bias of the light-emitting diode, and the light-emitting diode is proportional to the current passing through itself. In other words, the greater the current passing, the higher the brightness of the light-emitting diode. Common dimming methods include analog dimming and digital dimming. The analog dimming method achieves a change in brightness by adjusting the magnitude of the forward current flowing through the light emitting diode. The digital dimming method controls the light-emitting diodes, and uses the phenomenon of persistence of the human eye to control the average brightness by changing the duty cycle of the light-emitting diodes. With the analog dimming method, although the implementation is simple, it is necessary to increase the external circuit and increase the cost of the system. Therefore, the current development trend is mainly based on digital dimming.

Please refer to FIG. 1 , which is a schematic diagram of a conventional light emitting module 100 . The light emitting module 100 can be used to provide a backlight of a liquid crystal display, which has a scaler 112 and a driving circuit 122. The scaler 112 and the drive circuit 122 are formed in different integrated circuit chips, respectively, and are disposed on the scaler circuit board 110 and the drive circuit board 120, respectively. The scaler 112 receives the image signal S _IMG to convert the resolution of the image signal S _IMG from the first resolution to the second resolution to generate and output the control signal DIM[1:4] to the driving circuit 122. The control signal DIM[1:4] is a four-bit digital signal, each of which is used to control a corresponding LED string 160. Each of the light emitting diode strings 160 has a plurality of light emitting diodes 162.

Please refer to FIG. 1 and FIG. 2. FIG. 2 is a timing diagram of the elements of the control signal DIM[1:4] and the driving voltage V _OUT of FIG. Each of the bits DIM[1] to DIM[3] of the control signal DIM[1:4] is used to control the opening and closing of the corresponding LED string 160. Further, when the value of any of the bit elements DIM[1] to DIM[3] is "1" (high potential), the corresponding LED string 160 is turned on; When the value of any of the bits DIM[1] to DIM[3] is "0" (low potential), the corresponding LED string 160 is turned off.

However, since the driving circuit 122 controls the driving voltage V _OUT according to the terminal voltage of the second terminal B of the sampled LED string 160, the terminal voltage of the second terminal B is different for each of the LEDs. The on/off state of the body string 160 is different, so that the terminal voltage of the second terminal B sampled by the driving circuit 122 is not the same, and the voltage value of the driving voltage V _OUT is often changed. However, the voltage value of the driving voltage V _OUT changes frequently result, the driving voltage V _OUT becomes a noise source itself. In this case, the noise of the light-emitting module 100 is increased, and the intensity of the light provided by the light-emitting module 100 is not stable.

The invention provides an image processing circuit and a light-emitting module, which perform a sampling action of the terminal voltage when all the LED strings are turned on, so as to reduce the noise of the light-emitting module and stabilize the luminous intensity of the light-emitting module. .

The invention provides a lighting module comprising a plurality of parallel LED strings and an integrated circuit. Each of the light emitting diode strings includes a plurality of light emitting diodes connected in series. The integrated circuit includes a drive circuit. The driving circuit is coupled to the plurality of LED strings for supplying a driving voltage to the first ends of the plurality of LED strings to drive the plurality of LED strings. The driving circuit is configured to maintain the voltage value when the driving voltage is turned on when the LED strings are all turned on until the plurality of LED strings are turned on again.

The invention provides an image processing circuit adapted to drive a plurality of light emitting diode strings. The image processing circuit includes a drive circuit. The driving circuit is coupled to the plurality of LED strings for supplying a driving voltage to the first ends of the plurality of LED strings to drive the plurality of LED strings. The driving circuit is configured to maintain the voltage value when the driving voltage is turned on when the LED strings are all turned on until the plurality of LED strings are turned on again.

In an embodiment of the invention, the integrated circuit further includes a scaler. The scaler is coupled to the driving circuit for processing the image signal to generate and output the control signal to the driving circuit, and the driving circuit controls the operation of the plurality of LED strings according to the control signal.

In an embodiment of the invention, the scaler is further configured to convert the resolution of the image signal from the first resolution to the second resolution.

In an embodiment of the invention, the scaler comprises a register for storing data. When the driving circuit detects that the above-mentioned LED string is abnormal, the abnormal information of the LED string is stored in the register.

In an embodiment of the invention, when the driving circuit detects that the LED string is abnormal, the driving circuit turns off the LED string, and the scaler continues to operate.

In an embodiment of the invention, the scaler includes a reference voltage circuit for providing a reference voltage to the drive circuit to cause the drive circuit to generate a drive voltage according to the reference voltage.

In an embodiment of the invention, the driving circuit controls a duty cycle of each of the LED strings according to the control signal.

In an embodiment of the invention, the integrated circuit is a single wafer.

In an embodiment of the invention, the driving circuit includes a sampling circuit and a pulse width modulation circuit. The sampling circuit is configured to sample the voltage of the second end of the LED string when all of the LED strings are turned on, and generate a control voltage according to the sampled voltage. The pulse width modulation circuit is configured to control the voltage value of the driving voltage according to the control voltage.

In an embodiment of the invention, the light emitting module is used to provide a backlight of the liquid crystal display.

Based on the above, the driving circuit of the light-emitting module of the present invention performs the sampling operation of the terminal voltage when all the LED strings are turned on, so that the change of the driving voltage of the driving circuit does not become a noise source, thereby reducing The noise of the light-emitting module and the luminous intensity of the light-emitting module are stabilized. In addition, the scaler and the driver circuit can be integrated into a single chip, which can greatly improve the application flexibility of the light-emitting diode, and can achieve better immediacy and application flexibility for the support of the screen.

The above described features and advantages of the present invention will be more apparent from the following description.

Please refer to FIG. 3. FIG. 3 is a schematic diagram of a light emitting module 300 according to an embodiment of the present invention. The light emitting module 300 can be used to provide a backlight of a liquid crystal display, which has a scaler 330 and a driving circuit 340. In the present embodiment, the scaler 330 and the drive circuit 340 are formed in the same integrated circuit 320, and the integrated circuit 320 can be a single wafer and disposed on the circuit board 310. However, the invention is not limited thereto. For example, in other embodiments of the invention, the scaler 330 can be separated from the integrated circuit 320 and operated independently of the drive circuit 340. For another example, in other embodiments of the present invention, the light emitting module may not include the scaler 330.

The light emitting module 300 further includes a plurality of light emitting diode strings 360, and each of the light emitting diode strings 360 has a plurality of light emitting diodes 362. In this embodiment, the light-emitting module 300 has four LED strings 360, but the invention is not limited thereto, and those skilled in the art should understand the illumination module of the light-emitting module of the present invention. The number of polar body strings can be other numbers greater than one.

In this embodiment, the scaler 330 is coupled to the driving circuit 340 for processing the image signal S _IMG to generate and output the control signals DIM[1:4] to the driving circuit 340, so that the driving circuit 340 is based on the control signal DIM. [1:4] Controls the operation of the plurality of light-emitting diode strings 360 described above. In addition, the scaler 330 can also be used to convert the resolution of the image signal S _IMG from the first resolution to the second resolution. In this embodiment, the control signals DIM[1:4] are four-bit digital signals, each of which is used to control the operation of a corresponding LED string 360. Each of the light emitting diode strings 360 has a plurality of light emitting diodes 362. It should be understood that in the present embodiment, the number of bits of the control signal DIM[1:4] generated by the scaler 330 is equal to the number of the LED strings 360. In the embodiment of the other lighting module of the present invention, the number of bits of the control signal received by the driver for controlling the operation of the LED string is equal to the number of the LED strings.

The driving circuit 340 is coupled to the plurality of LED strings 360 for supplying the driving voltage V _OUT to the first end A of the LED string 360 to drive the LED string 360. Please refer to FIG. 3 and FIG. 4. FIG. 4 is a timing diagram of the elements of the control signals DIM[1:4] and the driving voltage V _OUT of FIG. Each of the bits DIM[1]~DIM[4] of the control signal DIM[1:4] is used to control the opening and closing of the corresponding LED string 360. Further, when the value of any of the bits DIM[1]~DIM[4] is "1" (high potential), the corresponding LED string 360 is turned on; When the value of any of the bits DIM[1]~DIM[4] is "0" (low potential), the corresponding LED string 360 is turned off. Therefore, the driving circuit 340 can control the duty cycle of each of the LED strings 360 according to the control signals DIM[1:4].

The driver circuit 340 maintains the voltage value of the driving voltage V _OUT when all of the LED strings 360 are turned on until all of the LED strings 360 are turned on again. 4 as an example, the drive circuit 340 will drive to maintain voltage V _OUT of the voltage value during the time the cells D1, D2 and D3, the voltage value of the driving voltage V _OUT in the time frame between D1, D2 and D3 is equal to the maintained and the driving voltage V _OUT of the entire light-emitting diode string 360 _1, T ₂ and T ₃ may all be turned on at the time point T at time point T _1, T ₂ and T ₃ of the voltage value.

In this way, the driving voltage V _OUT supplied to the LED string 360 by the driving circuit 340 can be maintained for a long time, so that a noise source is not formed to interfere with other circuits, and the LED string 360 is not caused. The current changes rapidly.

Referring to FIG. 3 again, in another embodiment of the present invention, the scaler 330 can include a register 332 for storing data. When the driving circuit 340 detects that the LED string 360 is abnormal, the abnormal information of the LED string 360 is stored in the register 332. In addition, in an embodiment of the invention, when the driving circuit 340 detects that the LED string 360 is operating abnormally At this time, the driving circuit 340 turns off the LED string 360, and the scaler 330 at this time continues to operate. In this way, when the LED string 360 is abnormal, the LED string 360 can be turned off in time, and the abnormal information stored in the register 332 can be read out as a subsequent debug or The basis for maintenance.

In an embodiment of the invention, the scaler 330 can include a reference voltage circuit 334. The reference voltage circuit 334 is configured to provide the reference voltage V _REF to the driving circuit 340 to cause the driving circuit 340 to generate the driving voltage V _OUT according to the reference voltage V _REF . In this embodiment, the voltage value of the reference voltage V _REF provided by the reference voltage circuit 334 can be adjusted to meet different needs. For example, in response to a different number of LED strings 360, the reference voltage circuit 334 can provide a reference voltage V _{REF having} a suitable voltage value to the driver circuit 340 to align the illumination intensity of the LED string 360.

Please refer to FIG. 5. FIG. 5 is a schematic diagram of a light emitting module 500 according to an embodiment of the present invention. Similar to the above-mentioned light-emitting module 300, the light-emitting module 500 can also be used to provide a backlight of a liquid crystal display, which has a scaler 530 and a driving circuit 540. In the present embodiment, the scaler 530 and the drive circuit 540 are formed in the same integrated circuit 540, and the integrated circuit 540 can be a single wafer. However, the invention is not limited thereto. For example, in other embodiments of the invention, the scaler 530 can be separated from the integrated circuit 520 and operated independently of the drive circuit 540. For another example, in other embodiments of the present invention, the light emitting module may not include the scaler 530.

The light emitting module 500 further includes a plurality of light emitting diode strings 560, and each of the light emitting diode strings 560 has a plurality of light emitting diodes 562. In this reality In the embodiment, the light-emitting module 500 has four light-emitting diode strings 560, but the invention is not limited thereto, and those skilled in the art should understand the light-emitting diodes of the light-emitting module of the present invention. The number of strings can be other numbers greater than or equal to two.

In this embodiment, the scaler 530 is coupled to the driving circuit 540 for processing the image signal S _IMG to generate and output the control signal DIM[1:4] to the driving circuit 540, so that the driving circuit 540 is based on the control signal DIM. [1:4] Controls the operation of the plurality of light emitting diode strings 560 described above. In addition, the scaler 530 can also be used to convert the resolution of the image signal S _IMG from the first resolution to the second resolution. In this embodiment, the control signals DIM[1:4] are four-bit digital signals, each of which is used to control a corresponding LED string 560. Each of the light emitting diode strings 560 has a plurality of light emitting diodes 562. In the present embodiment, the number of bits of the control signal DIM[1:4] generated by the scaler 530 is equal to the number of the LED strings 560.

The driving circuit 540 is coupled to the plurality of LED strings 560 for supplying the driving voltage V _OUT to the first end A of the LED string 560 to drive the LED string 560. Please refer to FIG. 5 and FIG. 6. FIG. 6 is a timing diagram of the elements of the control signal DIM[1:4] and the driving voltage V _OUT of FIG. Each of the bits DIM[1]~DIM[4] of the control signal DIM[1:4] is used to control the opening and closing of the corresponding LED string 560. Further, when the value of any of the bits DIM[1]~DIM[4] is "1" (high potential), the corresponding LED string 560 is turned on; When the value of any of the bits DIM[1]~DIM[4] is "0" (low potential), the corresponding LED string 560 is turned off. Therefore, the driving circuit 560 can control the duty cycle of each of the LED strings 560 according to the control signals DIM[1:4].

The driver circuit 540 maintains the voltage value of the driving voltage V _OUT when all of the LED strings 560 are turned on until all of the LED strings 560 are turned on again. 6 as an example, the drive circuit 540 will drive voltage value is maintained within the grid voltage V _OUT D1, D2 and D3 between the time and the drive voltage V _OUT during the time grid D1, D2 and D3 of the voltage value within maintained equal to and the driving voltage V _OUT of the entire light-emitting diode string 560 _1, T ₂ and T ₃ may all be turned on at the time point T at time point T _1, T ₂ and T ₃ of the voltage value.

In this way, the driving voltage V _OUT supplied to the LED string 560 by the driving circuit 540 can be maintained for a long time, so that a noise source is not formed to interfere with other circuits, and the LED string 560 is not caused. The current changes rapidly.

In an embodiment of the invention, the driving circuit 540 can include a sampling circuit 541 and a Pulse Width Modulation (PWM) circuit 550. The sampling circuit 541 is configured to sample the voltage of the second terminal B when the LED string 560 is fully turned on, and generate a control voltage V _C according to the sampled voltage. The pulse width modulation circuit 550 is configured to control the voltage value of the driving voltage V _OUT according to the control voltage V _C .

In an embodiment of the invention, the driving circuit 540 further includes a first transistor Q1, a second transistor Q2, a third transistor Q3, and a fourth transistor Q4, the gates of which are respectively controlled by the control signal DIM[ One bit of 1:4], and its drain is connected to the second end B of the corresponding LED string 560 through pins VFB1, VFB2, VFB3 and VFB4, respectively. The sampling circuit 541 further includes a multiplexer 542, a first error amplifier 544, a sample and hold circuit 546, and a second error amplifier 548. The multiplexer 542 selects and outputs the minimum voltage among the voltages of the second terminals B of the respective LED strings 560. The first error amplifier 544 outputs a corresponding voltage according to the reference voltage V _REF and the voltage output from the multiplexer 542. The sample and hold circuit 546 is controlled by the adjustment signal S _D . When the adjustment signal S _{D is} at a high potential, the sample hold circuit 546 samples the first divided voltage V _S ; and when the adjustment signal S _{D is} at a low potential, the sample hold circuit 546 maintains the sampled first divided voltage V _S . A second error amplifier 548 circuit 546 will be sampled first and then divided voltage V _S of the first divided voltage V _S based on the output voltage corresponding to the sample and hold. The sampling circuit 541 may further include a first switch SW1 and second switch SW2, wherein the first switch SW1 is coupled to the output terminal of the first error amplifier 544 and controlled by the adjustment signal S _D, and the second switch SW2 is coupled to the first The output of the second error amplifier 548 is controlled by the signal Signal To adjust the complementary signal of signal S _D . With the above structure, the sampling circuit 541 outputs the control voltage V _C to the pulse width modulation circuit 550, and causes the pulse width modulation circuit 550 to control the voltage value of the driving voltage V _OUT according to the control voltage V _C .

In an embodiment of the invention, the light emitting module 500 may further include a first resistor R ₁ and a second resistor R ₂ connected in series for dividing the input voltage V _IN to generate and output a second divided voltage V _L to The pin UVLO of the drive circuit 540. Wherein, the input voltage V _IN is a DC voltage. In addition, the light emitting module 500 can further include an inductor L _EXT and a diode D _EXT . The inductor L _{EXT is} used for DC conversion of the input voltage V _IN , and the diode D _EXT is used for rectification. The light emitting module 500 further includes a fifth transistor Q5 and a shifter 552. The shifter 552 is coupled to the pulse width modulation circuit 550 via the pin LX for shifting the level of the voltage output by the pulse width modulation circuit 550. The fifth transistor Q5 is turned on or off according to the output voltage level of the shifter 552, so that the voltage of the drain of the fifth transistor Q5 can be changed by the output voltage of the pulse width modulation circuit 550. Adjustment. The light-emitting module 500 can further include a resistor R _CS , one end of which is coupled to the source of the fifth transistor Q5 and the pin OCP of the driving circuit 540 , and the other end of which is coupled to the pin PGND of the driving circuit 540 . The driving circuit 540 can determine the magnitude of the current flowing through the fifth transistor Q5 according to the potential of the pins OCP, PGND and the resistance value of the resistor R _CS . The light emitting module 500 further includes a third resistor R ₃ and a fourth resistor R ₄ connected in series for dividing the driving voltage V _OUT to generate and output the first divided voltage V _S to the pin OVS of the driving circuit 540. Thereby, the driving circuit 540 can determine the voltage values of the input voltage V _IN and the driving voltage V _OUT according to the first divided voltage V _S and the second divided voltage V _L .

In other embodiments of the present invention, an image processing circuit adapted to drive the plurality of LED strings 360 or 560 is also provided. The image processing circuit described above may be the integrated circuit 320 of FIG. 3 or the integrated circuit 520 of FIG. 5, and the sampling operation of the terminal voltage may be performed when all of the LED strings 360 or 560 are turned on to reduce The noise of the light-emitting module and the luminous intensity of the light-emitting module are stabilized. For a detailed description of the image processing circuit, reference may be made to the above description of the integrated circuits 320 and 520, which will not be described herein.

In summary, the driving circuit of the light-emitting module of the present invention performs the sampling operation of the terminal voltage when all the LED strings are turned on, so that the change of the driving voltage of the driving circuit does not become a noise source, so The noise of the light-emitting module can be reduced, and the luminous intensity of the light-emitting module can be stabilized. In addition, the scaler and the driver circuit can be integrated into a single chip, which can greatly improve the application flexibility of the light-emitting diode, and can achieve better immediacy and application flexibility for the support of the screen.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

100, 300, 500. . . Light module

110. . . Scaler board

120. . . Drive board

310. . . Circuit board

320, 520. . . Integrated circuit

112, 330, 530. . . Scaler

332. . . Register

334. . . Reference voltage circuit

122, 340, 540. . . Drive circuit

160, 360, 560. . . Light-emitting diode string

162, 362, 562. . . Light-emitting diode

541. . . Sampling circuit

542. . . Multiplexer

544. . . First error amplifier

546. . . Sample and hold circuit

548. . . Second error amplifier

550. . . Pulse width modulation circuit

552. . . Displacer

A. . . First end

B. . . Second end

DIM[1:4]. . . Control signal

DIM[1]~DIM[4]. . . Bit

D _EXT . . . Dipole

D1, D2, D3. . . Time interval

T ₁ , T ₂ , T ₃ . . . Time point

S _IMG . . . Image signal

S _D . . . Adjustment signal

. . . Adjust the complementary signal of signal S _D

SW1. . . First switch

SW2. . . Second switch

V _IN . . . Input voltage

V _REF . . . Reference voltage

V _OUT . . . Driving voltage

V _C . . . Control voltage

V _S . . . First partial pressure

V _L . . . Second partial pressure

L _EXT . . . inductance

R ₁ . . . First electric group

R ₂ . . . Second group

R ₃ . . . Third group

R ₄ . . . Fourth electric group

R _CS . . . Power group

Q1. . . First transistor

Q2. . . Second transistor

Q3. . . Third transistor

Q4. . . Fourth transistor

Q5. . . Fifth transistor

UVLO, LX, OCP, PGND, OVS, VFB1, VFB2, VFB3, VFB4. . . Foot position

FIG. 1 is a schematic diagram of a conventional light emitting module.

2 is a timing chart of the elements and driving voltages of the control signals of FIG. 1.

FIG. 3 is a schematic diagram of a light emitting module according to an embodiment of the invention.

4 is a timing chart of the elements and driving voltages of the control signals of FIG. 3.

FIG. 5 is a schematic diagram of a light emitting module according to an embodiment of the invention.

Fig. 6 is a timing chart of the elements and driving voltages of the control signals of Fig. 5.

300. . . Light module

310. . . Circuit board

320. . . Integrated circuit

330. . . Scaler

332. . . Register

334. . . Reference voltage circuit

340. . . Drive circuit

360. . . Light-emitting diode string

362. . . Light-emitting diode

A. . . First end

B. . . Second end

DIM[1:4]. . . Control signal

S _IMG . . . Image signal

V _REF . . . Reference voltage

V _OUT . . . Driving voltage

Claims (15)

A lighting module includes: a plurality of parallel LED strings, each LED string includes a plurality of series LEDs; and an integrated circuit comprising: a driving circuit coupled to the The light emitting diode strings are configured to supply a driving voltage to the first ends of the light emitting diode strings to drive the light emitting diode strings, and the driving circuit is configured to maintain the driving voltage on the light emitting diodes The voltage value when all the polar body strings are turned on until the light emitting diode strings are all turned on again. The illuminating module of claim 1, wherein the integrated circuit further comprises: a scalar coupled to the driving circuit for processing an image signal to generate and output a control signal to The driving circuit causes the driving circuit to control the operation of the LED strings according to the control signal. The illuminating module of claim 2, wherein the calibrator is further configured to convert the resolution of the image signal from a first resolution to a second resolution. The illuminating module of claim 2, wherein the calibrator comprises: a temporary register for storing data; wherein when the driving circuit detects that the LED strings are abnormally operated, The abnormal information of the LED strings will be stored in the register. The illuminating module of claim 2, wherein when the driving circuit detects that the LED strings are abnormal, the driving circuit turns off the LED strings, and the calibration The device continues to operate. The illuminating module of claim 2, wherein the calibrator comprises: a reference voltage circuit for providing a reference voltage to the driving circuit, so that the driving circuit generates the driving voltage according to the reference voltage . The lighting module of claim 2, wherein the driving circuit controls a duty cycle of each of the LED strings according to the control signal. The lighting module of claim 2, wherein the integrated circuit is a single wafer. The illuminating module of claim 1, wherein the driving circuit comprises: a sampling circuit for sampling a voltage of the second end of the LED strings when all of the LED strings are turned on; And generating a control voltage according to the sampled voltage; and a pulse width modulation circuit for controlling the voltage value of the driving voltage according to the control voltage. The illuminating module of claim 1, wherein the illuminating module is used to provide a backlight of a liquid crystal display. An image processing circuit is configured to drive a plurality of LED strings. The image processing circuit includes: a driving circuit coupled to the LED strings for supplying a driving voltage to the LEDs The first end of the string is used to drive the LED strings, and the driving circuit is configured to maintain the voltage value of the driving voltage when the LED strings are all turned on until the LED strings are re-energized All are turned on. The image processing circuit of claim 11, wherein the image processing circuit further comprises: a scaler coupled to the drive circuit for processing an image signal to generate and output a control signal to The driving circuit causes the driving circuit to control the operation of the LED strings according to the control signal. The image processing circuit of claim 12, wherein the scaler is further configured to convert the resolution of the image signal from a first resolution to a second resolution. The image processing circuit of claim 12, wherein the scaler comprises: a temporary register for storing data; wherein when the driving circuit detects that the light emitting diode strings are abnormally operated, The abnormal information of the LED strings will be stored in the register. The image processing circuit of claim 11, wherein the driving circuit comprises: a sampling circuit for sampling a voltage of the second end of the LED strings when all of the LED strings are turned on; And generating a control voltage according to the sampled voltage; and a pulse width modulation circuit for controlling the voltage value of the driving voltage according to the control voltage.