TWI515708B - Gamma voltage driving system and current control method thereof - Google Patents

Description

Gamma voltage drive system and its current control method

The present invention relates to a gamma voltage driving system and a current control method thereof, and more particularly to a gamma voltage driving system and a current control method thereof that can prevent a large current from being generated when a display device is turned on.

The gray-scale changes in the color of the human eye are not distributed in a linear manner. For example, the human eye is more sensitive to the grayscale change of the low grayscale picture than the grayscale change of the high grayscale picture. Therefore, today's display devices typically provide a gamma voltage and a reference voltage through a gamma voltage drive system to perform gamma curve correction on the input picture data. In this way, the human eye can change to a linear relationship with respect to the color gray scale change of the display device.

Conventional gamma voltage drive systems typically use operational amplifiers to provide gamma voltages, and the outputs of these operational amplifiers are often electrically connected to large capacitors. However, when the display device is turned on, the operational amplifier will output a large current to charge these large capacitors, so that the large current output by the operational amplifier may burn the circuit or activate the power protection mechanism of the power control circuit.

Therefore, there is a need for a gamma voltage drive system and its current control method to solve the above problems.

One aspect of the present invention is to provide a gamma voltage drive system and a current control method therefor. This gamma voltage drive system and its current control method slowly increase the output voltage stepwise to avoid large currents.

According to an embodiment of the present invention, in the current control method, an operational amplifier circuit is first provided, wherein the operational amplifier circuit includes an operational amplifier and a digital to analog converter, and the digital to analog converter outputs the original voltage according to the reference code to The operational amplifier is such that the operational amplifier provides the output voltage accordingly. Then, the initial code value of the reference code and the target code value are provided. Next, a reference code having an initial code value is provided to the digital to analog converter to cause the operational amplifier to output current and voltage. Then, a code value accumulation operation is performed. In this code value accumulation operation, the code value increasing step is first performed to increase the code value of the reference code. Then, the reference code whose code value is increased is supplied to the digital to analog converter to change the value of the output voltage. Next, it is determined whether the code value of the reference code is equal to the target code value to provide a first determination result. When the first judgment result is NO, the code value accumulation operation is performed again until the first judgment result is YES.

According to another embodiment of the invention, the gamma voltage drive system includes an operational amplifier circuit and a control unit. The operational amplifier circuit includes a digital to analog converter and an operational amplifier. A digital to analog converter is used to output the original voltage based on the reference code. The operational amplifier is electrically coupled to a digital to analog converter to provide an output voltage based on the original voltage. The control unit is used to provide a reference code to a digital to analog converter. This control sheet The element includes a judgment module and a counter module. The determining module is configured to determine whether the code value of the reference code is equal to the target code value to provide a first determination result. The counter module is configured to increase the code value of the reference code when the first determination result is no.

It can be seen from the above description that the gamma voltage driving system and the current control method thereof in the embodiment of the present invention periodically increase the code value of the reference code to slowly increase the output voltage of the operational amplifier, thereby preventing the operational amplifier circuit from outputting a large current.

100‧‧‧Gamma Voltage Drive System

110‧‧‧Gamma voltage drive circuit

111‧‧‧Resistance series

111A‧‧‧Resistance tandem endpoint

111B‧‧‧Resistance tandem endpoint

112‧‧‧Digital to analog converter

113‧‧‧Operational Amplifier

113a‧‧‧Output endpoint

114‧‧‧Resistance series

114A‧‧‧Resistance tandem endpoint

114B‧‧‧Resistance tandem endpoint

115‧‧‧Digital to Analog Converter Group

115a-115c‧‧‧Digital to Analog Converter

116‧‧‧Operational Amplifier Group

116a-116c‧‧‧Operational Amplifier

120‧‧‧Power circuit

130‧‧‧Control circuit

132‧‧‧Control unit

132a‧‧‧ counter module

132b‧‧‧Judgement module

134‧‧‧ memory module

200‧‧‧ Current control method

210‧‧‧ code value providing steps

220‧‧‧Starting steps

230‧‧‧ Code value accumulation operation

232‧‧‧Code value increase step

234‧‧‧Adjustment steps

236‧‧‧ Judgment steps

300‧‧‧Gamma Voltage Drive System

310‧‧‧Power Monitoring Module

400‧‧‧ Current control method

410‧‧‧Reset steps

420‧‧‧ Judgment steps

GC‧‧ gamma voltage code

Iout‧‧‧Output current

NA, NB‧‧‧ nodes

R1, R2‧‧‧ resistance

RC‧‧‧ reference code

V _IN ‧‧‧ input voltage

V _REF ‧‧‧reference voltage

Vout, Vo‧‧‧ output voltage

The above and other objects, features, and advantages of the present invention will become more apparent and understood. A schematic diagram of a circuit structure of a gamma voltage driving system according to an embodiment of the present invention.

2 is a flow chart showing a current control method according to an embodiment of the present invention.

FIG. 3 is a schematic diagram showing the circuit structure of a gamma voltage driving system according to an embodiment of the present invention.

4 is a flow chart showing a current control method according to an embodiment of the present invention.

FIG. 5 is a schematic diagram showing the timing relationship between a power supply voltage, a reference code value, an output voltage, and an output current according to an embodiment of the present invention.

Please refer to FIG. 1 , which is a schematic diagram showing the circuit structure of a gamma voltage driving system 100 according to an embodiment of the present invention. The gamma voltage driving system 100 is applied to a display device to provide a display device. Gamma voltage. The gamma voltage driving system 100 includes a gamma voltage driving circuit 110, a power supply circuit 120, and a control circuit 130, wherein the power supply circuit 120 is configured to provide an input voltage V _IN to the gamma voltage driving circuit 110, and the gamma voltage driving circuit 110 is used. To provide a gamma voltage to a back-end circuit (eg, a source driver), the control circuit 130 is configured to control the gamma voltage generated by the gamma voltage drive circuit 110. In the present embodiment, the operational amplifier used by the gamma voltage driving circuit 110 is a rail-to-rail amplifier, but the embodiment of the present invention is not limited thereto.

The gamma voltage driving circuit 110 includes a resistor string 111, a digital to analog converter 112, an operational amplifier 113, a resistor string 114, a digital to analog converter group 115, and an operational amplifier group 116. The end point 111A of the resistor string 111 is electrically connected to the power supply circuit 120, and the other end point 111B is coupled to the reference voltage terminal to receive the reference voltage V _REF . The resistor string 111 includes a plurality of resistors R1 connected in series. In the resistor string 111, there is a node NA between every two adjacent resistors R1, and the voltage value is between the input voltage V _IN and the reference voltage V _REF . Therefore, the resistor string 111 can be used to provide a plurality of partial voltages.

The digital to analog converter 112 is electrically connected to the resistor string 111 and the control circuit 130 to select a voltage from the plurality of divided voltages provided by the resistor string 111 according to the reference code RC provided by the control circuit 130. And output it to the operational amplifier 113. The operational amplifier 113 is used to adjust The digits are (eg, amplified or buffered) to the voltage provided by the analog converter 112 and the adjusted voltage Vo is supplied from the output terminal 113a to the resistor string 114.

The architecture of resistor string 114 is similar to resistor string 111. The end point 114A of the resistor string 114 is electrically connected to the output terminal 113a of the operational amplifier 113, and the other end 114B is electrically connected to the reference voltage terminal to receive the voltage Vo and the reference voltage V _REF . The resistor string 114 includes a plurality of resistors R2 connected in series. In the resistor string 114, there is a node NB between every two adjacent resistors R2, and the voltage value is between the voltage Vo and the reference voltage V _REF . Thus, the resistor string 114 can be used to provide multiple partial voltages.

The digital to analog converter bank 115 includes a plurality of digits to analog converters 115a-115c. Each digit to analog converter 115a-115c is electrically coupled to the resistor string 114 and the control circuit 130 to provide a plurality of divided voltages from the resistor string 114 in accordance with the gamma voltage code GC provided by the control circuit 130. A voltage is selected and output to the operational amplifier bank 116.

The operational amplifier bank 116 includes a plurality of operational amplifiers 116a-116c. The operational amplifiers 116a-116c are electrically coupled in a one-to-one manner to the digital to analog converters 115a-115c to condition (e.g., amplify or buffer) the digits to the voltages provided by the analog converters 115a-115c and output The adjusted voltage Vout.

The number of converters and the number of operational amplifiers included in the digital to analog converter bank 115 and operational amplifier bank 116 of the present embodiment are not intended to limit the invention. In other embodiments of the invention, the digital to analog converter bank 115 and the operational amplifier bank 116 may include more than one converter and Amplifier.

The control circuit 130 is electrically coupled to the digital to analog converter 112 and the digital to analog converter bank 115 to provide a reference code RC and a gamma voltage code GC. The control circuit 130 includes a control unit 132 and a memory module 134. In this embodiment, the control unit 132 includes a counter module 132a and a determination module 132b. Thus, the control unit 132 can periodically control the output voltage of the operational amplifier 113 when the display device is powered on, thereby preventing the operational amplifier group 116 from outputting. High Current. In the following description, how to use the control unit 132 to prevent large current generation will be described.

Please refer to FIG. 2, which is a flow chart of a current control method 200 according to an embodiment of the present invention. The current control method 200 of the present embodiment utilizes the control unit 132 to prevent large current generation. In the current control method 200, a code value providing step 210 is first performed to provide an initial code value of the reference code and a target code value. The target code value is determined based on the target voltage to be output by the operational amplifier 113. Next, a startup step 220 is performed to control the memory module 134 by the control unit 132 to provide a reference code having an initial code value to the digital to analog converter 112, and to cause the operational amplifier 113 and the operational amplifier group 116 to start outputting. Voltage and current.

Then, a code value accumulation operation 230 is performed to accumulate the code value of the reference code by the control unit 132, so that the output voltage of the operational amplifier 113 is stepwise increased. In the code value accumulation operation 230, a code value addition step 232 is first performed to increase the code value of the reference code. In the present embodiment, the code value addition step 232 adds 1 to the code value of the reference code (i.e., plus 1 to the initial code value), but the embodiment of the present invention is not limited thereto. Other embodiments of the invention The increase in the code value can be determined according to the actual needs of the user.

Next, an adjustment step 234 is performed to supply the reference code with the increased code value to the operational amplifier 113 to adjust the output voltage of the operational amplifier 113. As such, the output voltage of the operational amplifier 113 is slightly increased. Then, a determining step 236 is performed to determine whether the code value of the reference code is equal to the target code value by using the determining module 132b. If the result of the determination is no, the code value addition step 232 is returned to perform the code value accumulation operation 230 again. At this time, the counting module 132a adds 1 to the code value of the reference code and records the number of times the code value is increased. If the result of the determination is YES, the output voltage of the operational amplifier 113 has reached the preset target voltage, so that the code value accumulation operation 230 is not required.

As can be seen from the above description, the current control method 200 of the embodiment of the present invention periodically increases the code value of the reference code to gradually increase the output voltage of the operational amplifier 113. As such, the output voltage of the operational amplifier bank 116 also rises slowly, avoiding the generation of large currents.

Please refer to FIG. 3, which is a schematic diagram showing the circuit structure of the gamma voltage driving system 300 according to an embodiment of the present invention. The gamma voltage drive system 300 is similar to the gamma voltage drive system 100, but differs in that the gamma voltage drive system 300 further includes a power supply monitoring module 310. The power monitoring module 310 is configured to monitor the power voltage provided by the display device to determine whether the display device is in the power-on state, and provide a determination result to the control unit 132, so that the control unit 132 controls the operational amplifier 113 when the display device is powered on. The output voltage is used to avoid large currents.

Please refer to FIG. 4, which illustrates a current according to an embodiment of the present invention. A flow chart of control method 400. The current control method 400 is applicable to the gamma voltage drive system 300 described above. In the current control method 400, a reset step 410 is first performed to reset the display device and begin to enter the power-on state. Next, a determining step 420 is performed to determine whether the power supply voltage of the display device is greater than a preset voltage threshold. If the result of the determination is no, the resetting step 410 is performed again to reset the display device again. If the determination result is yes, the power monitoring module 310 transmits a power-on signal to the control unit 132 to sequentially perform the steps in the current control method 200 to avoid large current generation. As shown in FIG. 5, when the power monitoring module 310 determines that the power supply voltage exceeds the preset threshold, the high-level power-on signal is sent to the control unit 132. Then, the control unit 132 performs a reference code accumulation operation to cause the output voltage of the operational amplifier 113 to rise stepwise, thereby causing the gamma voltage drive circuit 110 to provide a stable output current Iout.

In this embodiment, the determining step 420 determines whether the analog power supply voltage supplied by the display device (ie, VDDA, the highest value is, for example, 18V) is greater than a first voltage threshold, and determines the digital power supply voltage supplied by the display device (ie, VDDD, the highest value is, for example, 3.3V) is greater than a second voltage threshold. If the result of the determination is yes, the current control method 200 is performed, but the embodiment of the present invention is not limited thereto.

While the invention has been described above in terms of several embodiments, it is not intended to limit the scope of the invention, and the invention may be practiced in various embodiments without departing from the spirit and scope of the invention. The scope of protection of the present invention is defined by the scope of the appended claims.

210‧‧‧ code value providing steps

220‧‧‧Starting steps

230‧‧‧ Code value accumulation operation

232‧‧‧Code value increase step

234‧‧‧Adjustment steps

236‧‧‧ Judgment steps

400‧‧‧ Current control method

410‧‧‧Reset steps

420‧‧‧ Judgment steps

Claims (10)

A current control method includes: providing an operational amplifier circuit, wherein the operational amplifier circuit includes an operational amplifier and a digital to analog converter, and the digital to analog converter outputs a raw voltage to the operational amplifier according to a reference code, So that the operational amplifier provides an output voltage correspondingly; providing an initial code value of the reference code and an object code value; providing the reference code having the initial code value to a digital to analog converter, so that the operational amplifier Providing the output voltage; performing a code value accumulation operation, comprising: performing a code value increasing step to increase a code value of the reference code; and providing the reference code added with the code value to the digital bit to an analog converter to change the a value of the output voltage; and determining whether the code value of the reference code is equal to the target code value to provide a first determination result; and when the first determination result is no, performing the code value accumulation operation again until the first The result of the judgment is yes. The current control method of claim 1, wherein the operational amplifier is a rail-to-rail amplifier. The current control method of claim 1, wherein the code value increasing step is to increase the code value of the reference code by one. The current control method as described in claim 1 further includes: Determining whether the first power supply voltage of the operational amplifier circuit is greater than a first predetermined voltage threshold to provide a second determination result; determining whether the second power supply voltage of the operational amplifier circuit is greater than a second predetermined voltage valve a value to provide a third determination result; and when the second determination result and the third determination result are both yes, the code value accumulation operation is performed. The current control method of claim 4, wherein when the second determination result is no, a reset operation is performed to reset the operational amplifier circuit. The current control method of claim 5, wherein the first power supply voltage is an analog power supply voltage and the second power supply voltage is a digital power supply voltage. A gamma voltage driving system comprising: an operational amplifier circuit comprising: a digital to analog converter for outputting a raw voltage according to a reference code; and an operational amplifier electrically coupled to the digital to analog converter Providing an output voltage according to the original voltage; and a control unit for providing the reference code to the digital to analog converter, wherein the control unit comprises: a determining module for determining the code value of the reference code Whether it is equal to an object code value to provide a first judgment result; and a counter module for increasing the first judgment result Add the code value of the reference code. The gamma voltage driving system of claim 7, further comprising a power monitoring module, wherein the power monitoring module is configured to determine whether a first power voltage is greater than a first predetermined voltage threshold, Providing a second determination result, and determining whether the second power supply voltage of the one of the operational amplifier circuits is greater than a second predetermined voltage threshold to provide a third determination result, when the second determination result and the third determination result When yes, the control unit controls the determining module to determine the code value of the reference code. The gamma voltage driving system of claim 8, wherein the first power supply voltage is an analog power supply voltage and the second power supply voltage is a digital power supply voltage. The gamma voltage driving system of claim 7, wherein the counter module is configured to increase the code value of the reference code by one when the first determination result is no.