TW201535346A - Gamma reference voltage generator and gamma voltage generator of display device - Google Patents

Abstract

A gamma voltage generating circuit of a display device includes resistor strings of positive and negative polarities. The resistor string of the positive polarity includes a plenty of first type resistors electrically connected in series and a second type resistor. A first end of the second type resistor is electrically connected to one of the first type resistors. A voltage on the first end of the second type resistor is less than half of a gamma reference voltage. The resistor string of the negative polarity includes a third type resistor having one end receiving the gamma reference voltage and a plenty of fourth type resistors electrically connected in series. A first end of the first fourth type resistor is connected to a second end of the third type resistor. The voltage on the second end of the third type resistor is greater than half of the gamma reference voltage.

Description

Gamma reference voltage and gamma voltage generating circuit of display device

The present invention relates to a display device, and more particularly to a gamma voltage generating circuit for a display device.

With the popularity of portable electronic products, display screens are becoming more and more important. Among various display technologies, a liquid crystal display (LCD) has the advantages of low power consumption and high display quality, and is particularly suitable as a display screen of a portable electronic product. Gamma Correction is usually performed on the image brightness before the image is displayed. For example, the gamma correction circuit built in the liquid crystal display gamma correction of the image signal, so that the brightness of the image can be consistent with the human brain vision.

The gamma correction circuit generally includes a resistor string formed by a plurality of resistor strings. The series resistors divide the reference voltage and add the voltage output of each resistor to gamma. Gamma voltage. In general, the polarity of the voltage applied to the liquid crystal is reversed at a predetermined interval to effectively drive the liquid crystal molecules to change the arrangement, thereby changing the transmittance and brightness.

In the traditional liquid crystal display data driver (Source Driver), the full voltage range is usually covered, and the voltage will change from the minimum voltage value to the maximum voltage value (0 to VREF). Such a large voltage variation results in a digital analogy. The area of the converter (DAC) is greatly increased, and the area of the resistor string required to generate the gamma voltage is also greatly increased; in addition, two sets of registers are usually required in the conventional liquid crystal display data driving circuit to store gamma voltage related information. The register occupies a considerable area, which not only increases the manufacturing cost, but also makes it difficult to further reduce the thickness and thickness of the liquid crystal display.

Accordingly, an aspect of the present invention provides a gamma voltage generating circuit for a display device capable of reducing the number of resistors required to generate a gamma voltage and thereby reducing the area of a driving circuit of the display device.

According to an embodiment of the invention, the gamma voltage generating circuit of the display device includes a positive resistor string and a negative resistor string. The positive resistor string receives a gamma reference voltage to provide a plurality of positive polarity gamma voltages required for at least one positive channel, the positive resistor string comprising a plurality of first type resistors and At least one second type of resistor, the first type of resistors are electrically connected in series, and the first end of the second type of resistor is electrically connected in series with one of the first type of resistors, wherein the first type of resistor is on the first end The voltage is less than half of the gamma reference voltage. The negative resistance string receives the gamma reference voltage to provide a plurality of negative polarity gamma voltages required for at least one negative channel, the negative resistance string includes at least one third type resistor and a plurality of fourth type resistors , The first end of the third type of resistor receives the gamma reference voltage; the fourth type of resistor is electrically connected in series, and the first end of the first type 4 resistor is connected in series with the second end of the third type of resistor, And the voltage on the second terminal of the third type of resistor is greater than half of the gamma reference voltage.

Another aspect of the present invention provides a gamma reference voltage generating circuit for a display device capable of reducing a register area required for generating a gamma reference voltage while further omitting an external pin (PIN) to thereby reduce display The overall area of the device drive circuit.

According to another embodiment of the present invention, a gamma reference voltage generating circuit of a display device includes a non-volatile memory (Non-Volatile Memory), a register, and a controller. The non-volatile memory includes a first memory bank and a second memory bank to store a first set of gamma reference voltage values and a second set of gamma reference voltage values respectively; the register is electrically connected Non-volatile memory; the controller is electrically connected to the non-volatile memory and the temporary memory, and the controller determines whether to use the first memory bank or the second memory bank according to the memory switching message transmitted by a bus interface interface. The stored digital gamma voltage value is copied to the scratchpad.

In the above embodiment, the gamma voltage generating circuit and the gamma reference voltage generating circuit divide the resistor string into positive and negative polarities according to the polarity of the channel, and do not need to divide the full-scale reference voltage, and the range of voltage division is only required. More than half of the original reference voltage, the number of resistors can be greatly reduced, thus reducing the circuit area.

On the other hand, the bus interface is used instead of the external pin to transfer the memory switching message, and only one set of registers is needed to store the gamma voltage. The value further reduces the overall circuit area.

200‧‧‧ gamma voltage generating circuit

201‧‧‧reference voltage generation circuit

203‧‧Amplifier

204‧‧‧voltage resistor string

207‧‧‧Digital Analog Converter

209‧‧Amplifier

211‧‧‧Negative resistance string

211a‧‧‧The third type of resistance

211b‧‧‧Fourth type of resistance

213‧‧‧Positive resistor string

213a‧‧‧First class resistance

213b‧‧‧Second type resistor

215‧‧‧Digital Analog Converter

217‧‧‧Positive channel

217a‧‧‧Operational Amplifier

219‧‧‧negative channel

219a‧‧‧Operational Amplifier

301‧‧‧ bus interface

303‧‧‧ Non-volatile memory

305‧‧‧First Memory

307‧‧‧Second memory

309‧‧‧ register

311‧‧‧Memory copy area

313‧‧‧ Controller

315‧‧‧Digital Analog Converter

317‧‧‧Operational Amplifier

319‧‧‧Gamma reference voltage generation circuit

FIG. 1 is a schematic diagram showing voltage division of positive and negative polarity channels according to an embodiment of the present invention.

2 is a schematic diagram showing a gamma voltage generating circuit of a display device according to an embodiment of the present invention.

3 is a schematic diagram showing a gamma reference voltage generating circuit of a display device according to an embodiment of the present invention.

Herein, the terms first, second, third, etc. are used to describe various elements, components, and the like. However, these components and components should not be limited by these terms. Thus, a first element, component or the like hereinafter may also be referred to as a second element, component or the like without departing from the spirit of the invention. When an element is referred to as being "electrically connected" to another element, it can be directly connected to the other element or an additional element can be present. In contrast, when an element is referred to as a "direct electrical connection" to another element, no additional element is present.

Unless otherwise defined, all terms (including technical and scientific terms) used herein are intended to mean the meaning Furthermore, the definition of the above vocabulary in a commonly used dictionary should be interpreted as the present invention in the content of the present specification. A consistent meaning in the relevant field. Unless specifically defined, these terms are not to be interpreted as idealized or overly formal. Repeated use of one or more synonyms does not preclude the use of other synonyms.

In the gamma voltage generating circuit of the following embodiment, the resistor string is divided according to the polarity of the channel, and corresponding to the resistor string of the positive polarity channel, the number of resistors originally used to generate the negative polarity gamma voltage can be greatly reduced, corresponding to In the resistance string of the negative polarity channel, the number of resistors originally used to generate the positive polarity gamma voltage can be greatly reduced, thereby reducing the circuit area.

On the other hand, the bus interface is used instead of the external pin to transfer the memory switching information, and only one set of registers is needed to store the gamma voltage value, further reducing the circuit area and the chip package volume.

FIG. 1 is a schematic diagram showing voltage division of positive and negative polarity channels according to an embodiment of the present invention. In a conventional gamma voltage generating circuit, for each 10-bit channel, the gamma voltage needs to cover the complete reference voltage range, that is, the gamma string needs. The voltage division from the gamma reference voltage VREF to the ground voltage GND is provided, which requires a large number of resistors for voltage division, resulting in a large increase in the area of the resistor string and the digital to analog converter (DAC).

In fact, the ground voltage GND is not used in the positive channel, and further, the voltage from 0V to 1/2VREF is not used, and the gamma voltage in these ranges can be omitted. If some applications on the system are considered, the positive channel only needs to cover the voltage range from the gamma reference voltage VREF to point A (less than half of the gamma reference voltage VREF), and the point A to the power-on voltage GND is not required. Considering, therefore, the number of resistors is reduced from 2 ¹⁰ to 2 ⁹ , and the 10-bit digital analog converter (DAC) can also be simplified to 9 bits, greatly reducing the circuit area of the resistor string and the digital analog converter.

Similarly, in the negative polarity channel, the gamma reference voltage VREF is not used, and even the gamma voltage to VREF to 1/2 VREF is not used, and the gamma voltage in these ranges can be omitted. If taking into consideration the portion of the application on the system, the channel has to cover only negative point B (more than half of the gamma reference voltage VREF) to the range to the ground voltage GND, so only need to use resistors ²⁹ and 10-bit The digital analog converter can also be simplified to 9 bits, which greatly saves the circuit area of the resistor string and the digital analog converter.

2 is a schematic diagram showing a gamma voltage generating circuit of a display device according to an embodiment of the present invention. The gamma voltage generating circuit 200 of the display device mainly includes a positive polarity resistor string 213 and a negative polarity resistor string 211, and the positive polarity resistor string 213 and the negative polarity resistor string 211 divide the gamma reference voltage VREF to generate a plurality of gamma voltages. . The positive resistance string 213 divides the gamma reference voltage VREF to provide a plurality of positive polarity gamma voltages V _r1P ... V _rn-1P , V _rnP required for the positive polarity channel 217; the negative resistance string 211 is also divided The gamma reference voltage VREF is applied to provide a plurality of negative polarity gamma voltages V _r1N , V _r2N ... V _rnN required for the negative polarity channel 219, and the positive and negative polarity gamma voltages are transmitted to the _{plurality of} digital analog converters 215 And then respectively sent to the positive polarity channel 217 and the negative polarity channel 219, wherein one digital analog converter 215 corresponds to one operational amplifier 217a or one operational amplifier 219a, and the positive polarity channel 217 and the negative polarity channel 219 each contain multiple An operational amplifier (OP) 217a or an operational amplifier 219a.

The positive resistor string 213 includes a plurality of first type resistors 213a. The first type resistors 213a are electrically connected in series, and the positive polarity gamma voltages V _r1P ... V _{rn-1P at the} terminals of the first type resistor 213a V _rnP is transmitted to the digital analog converter 215. The first end U of the second type resistor 213b is electrically connected to one of the first type resistors 213a, wherein the voltage on the first end U of the second type resistor 213b is less than half of the gamma reference voltage VREF. It is less than 1/2VREF. The ratio of the voltage drop of the first type resistor 213a and the second type resistor 213b may be adjusted as needed, as long as the sum of the voltage drops of the first type resistor 213a is greater than the voltage drop of the second type resistor 213b, for example, the first type resistor 213a and the first type The ratio of the voltage drop of the second type resistor 213b may be 3:2, and the number of the first type resistors 213a and the number of bits of the digital analog converter 215 exhibit a power relationship of two, and when the digital analog converter 215 is 9 bits, The number of the first type of resistors 213a is 2 ⁹ = 512.

The negative resistance string 211 includes a third type resistor 211a and a plurality of fourth type resistors 211b. The first terminal V of the third type resistor 211a receives the gamma reference voltage VREF, and the fourth type resistor 211b is electrically connected in series. The first terminal W of the first fourth type resistor 211b is connected in series with the third type resistor 211a. The second terminal W, and the voltage on the second terminal W of the third type of resistor 211a, is greater than half of the gamma reference voltage VREF, that is, greater than 1/2 VREF. The voltage drop ratio of the third type resistor 211a and the fourth type resistor 211b may be adjusted as needed, as long as the voltage drop of the third type resistor 211a is smaller than the sum of the voltage drops of the fourth type resistor 211b, for example, the third type resistor 211a and all The voltage drop ratio of the fourth type of resistor 211b can be 2:3. The number of the fourth type of resistors 211b and the number of bits of the digital analog converter 215 exhibit a power relationship of two, wherein when the digital analog converter 215 is 9 bits, the number of the fourth type resistors 211b is 2 ⁹ = 512. .

In the positive resistance string 213 and the negative resistor string 211, the second end of the second type resistor 213b and the second end of the last fourth type resistor 211b are both grounded to GND. In this embodiment, each first type The resistor 213a has the same resistance value as each of the fourth type resistors 211b, the second type resistor 213b has the same resistance value as the third type resistor 211a, and the resistance value of the second type resistor 213b is greater than the resistance value of each of the first type resistors 213a. The resistance value of the third type resistor 211a is greater than the resistance value of each of the fourth type resistors 211b, but other types of resistance value matching manners are not excluded.

In this embodiment, the resistor string is divided according to the positive and negative polarities of the channel, so the number of resistors in a single polarity can be greatly reduced, from the original 2 ¹⁰ = 1024 to 2 ⁹ = 512. The corresponding digital analog converter 215 is also simplified from the original 10-bit circuit to a 9-bit circuit, so that the circuit area can be greatly reduced.

The gamma voltage generating circuit 200 further includes a bandgap reference generator 201, an amplifier 203, a voltage dividing resistor string 204, a digital analog converter 207, and an amplifier 209 for generating a voltage signal and amplifying, The voltage signal is divided to generate a suitable gamma reference voltage VREF.

3 is a schematic diagram showing a gamma reference voltage generating circuit of a display device according to an embodiment of the present invention. The gamma reference voltage of the display device generates electricity The path 319 mainly includes a non-volatile memory 303, a register 309, and a controller 313. The non-volatile memory 303 includes a first bank 305 and a second bank 307 for storing a first set of gamma reference voltages and a second set of gamma reference voltages, respectively. The reference voltage value is a digital type of data. The register 309 is electrically connected to the non-volatile memory 303, and the register 309 includes a memory copy area 311. The controller 313 is electrically connected to the non-volatile memory 303 and the register 309. The controller 313 determines the first memory bank 305 or the second according to the memory switching message transmitted by the bus interface 301. The digital gamma voltage value stored in the memory 307 is copied to the memory copy area 311 of the register 309, wherein the bus interface 301 can be a universal serial bus (USB) interface or an internal integrated circuit (I2C) interface. .

The controller 313 can determine which one to switch during the system mode switching, for example, during the switching of the gamma curve, the switching between the two-dimensional state and the three-dimensional state, by the memory switching message transmitted by the bus interface 301. The digital gamma voltage value stored in the memory is copied to the memory copy area 311 of the register 309 for subsequent use, so that two sets of registers are no longer needed to store the digital gamma voltage value, only one set is needed. The scratchpad, the original external switching signal pin (Pin) can also be omitted, and the memory bank can be switched by using the existing bus interface interface, thereby greatly reducing the circuit area.

The gamma reference voltage generating circuit 319 further includes a plurality of digital analog converters 315 and a plurality of operational amplifiers 317 (only one digital analog converter 315 and one operational amplifier 317 are illustrated in FIG. 3 as an example). A digital analog converter 315 corresponds to an operational amplifier 317. The digital analog converter 315 can directly electrically connect to the register 309, and omits the originally existing multiplexer circuit, further simplifying the circuit complexity. The digital analog converter 315 converts the digital type gamma reference voltage value into The analog type gamma reference voltage is then amplified by an operational amplifier 317 to pass the analog type gamma reference voltage.

In the above embodiment, the gamma voltage and the gamma reference voltage generating circuit divide the resistor string into two groups according to the polarity of the channel, and the resistors that are rarely used can be discarded according to the polarity of the channel, and the number of resistors can be greatly reduced. The circuit area can be reduced. On the other hand, the bus interface is used to replace the original external pin to transfer the memory switching message, reduce the package volume, and only need a set of registers to save the gamma voltage value, further reducing the circuit area. .

The illustrations discussed in this specification are for illustrative purposes only and are not intended to limit the scope and meaning of the invention or its examples. As such, the invention is not limited to the various embodiments set forth in the specification.

200‧‧‧ gamma voltage generating circuit

201‧‧‧reference voltage generation circuit

203‧‧Amplifier

204‧‧‧voltage resistor string

207‧‧‧Digital Analog Converter

209‧‧Amplifier

211‧‧‧Negative resistance string

211a‧‧‧The third type of resistance

211b‧‧‧Fourth type of resistance

213‧‧‧Positive resistor string

213a‧‧‧First class resistance

213b‧‧‧Second type resistor

215‧‧‧Digital Analog Converter

217‧‧‧Positive channel

217a‧‧‧Operational Amplifier

219‧‧‧negative channel

219a‧‧‧Operational Amplifier

Claims (10)

A gamma voltage generating circuit for a display device, comprising: a positive resistor string, a voltage-dividing gamma reference voltage to provide a plurality of positive polarity gamma voltages required for at least one positive channel, the positive resistor string comprising: a plurality of first type resistors, wherein the first type resistors are electrically connected in series; and at least one second type resistor has a first end electrically connected to one of the first type resistors, wherein The voltage on the first end of the second type of resistor is less than half of the gamma reference voltage; a negative resistor string is divided into a plurality of negative polarity gamma required to provide at least one negative polarity channel a voltage of the negative resistor comprising: at least one resistor of the third type, a first end receiving the gamma reference voltage; and a plurality of fourth type resistors, the fourth type of resistors being electrically connected together A first end of the first type of resistor is connected in series with a second end of the third type of resistor, and a voltage on the second end of the third type of resistor is greater than half of the gamma reference voltage. The gamma voltage generating circuit of claim 1, wherein a ratio of voltage drop of the first type of resistor to the second type of resistor is 3:2, and the third type of resistor and the fourth type of resistor The voltage drop ratio is 2:3. The gamma voltage generating circuit of claim 1, wherein the positive polarity gamma voltage and the negative polarity gamma voltage are respectively transmitted to a plurality of digital analog converters, and the digital analog converter corresponds to An operational amplifier, the first type of resistors or the number of the fourth type of resistors, and the number of bits of the digital analog converter exhibit a power relationship of two. The gamma voltage generating circuit of claim 3, wherein the digital analog converter is 9 bits, and the number of the first type resistors or the fourth type resistors is 2 ⁹⁼ 512. The gamma voltage generating circuit of claim 1, wherein the second end of one of the second type of resistors is grounded to the second end of one of the last type of resistors. The gamma voltage generating circuit of claim 1, wherein each of the first type of resistors has the same resistance value as each of the fourth type of resistors, and the second type of resistor has the same resistance value as the third type of resistors. . The gamma voltage generating circuit of claim 6, wherein the resistance of the second type of resistor is greater than the resistance of each of the first type of resistors, and the resistance of the third type of resistor is greater than that of each of the fourth type of resistors. resistance. A gamma reference voltage generating circuit for a display device, comprising: A non-volatile memory (Non-Volatile Memory) includes a first memory bank and a second memory bank for storing a first group of gamma reference voltage values and a second group of gamma reference voltages, respectively a temporary storage device electrically connected to the non-volatile memory; and a controller electrically connecting the non-volatile memory and the temporary storage device, wherein the controller switches according to a memory bank transfer The message determines to copy the digital gamma voltage value stored in the first memory bank or the second memory to the register. The gamma reference voltage generating circuit of claim 8, further comprising: a digital analog converter directly connected to the register, the digital analog converter adopting the gamma reference of the digital type The voltage value is converted to at least one gamma reference voltage of the analog type. The gamma reference voltage generating circuit of claim 8, further comprising at least one operational amplifier electrically connected to the digital analog converter, and the digital analog converter corresponding to the operational amplifier for amplifying and transmitting The gamma reference voltage of the analog type.