CN114495786A - Gamma voltage generating circuit - Google Patents

Gamma voltage generating circuit Download PDF

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Publication number
CN114495786A
CN114495786A CN202011526060.9A CN202011526060A CN114495786A CN 114495786 A CN114495786 A CN 114495786A CN 202011526060 A CN202011526060 A CN 202011526060A CN 114495786 A CN114495786 A CN 114495786A
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voltage
operational amplifier
circuit
coupled
internal operational
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CN202011526060.9A
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CN114495786B (en
Inventor
庄凯岚
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Raydium Semiconductor Corp
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Raydium Semiconductor Corp
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/20—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess voltage
    • H02H3/207—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess voltage also responsive to under-voltage
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2310/00—Command of the display device
    • G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
    • G09G2310/0264—Details of driving circuits
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Liquid Crystal Display Device Control (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Picture Signal Circuits (AREA)

Abstract

A gamma voltage generating circuit is applied to a source electrode driving circuit for a vehicle and comprises a first external operational amplifier, a second external operational amplifier, a first ladder resistor string, a second ladder resistor string, a selector circuit, an internal operational amplifier circuit and a first protection circuit and a second protection circuit. The first and second external operational amplifiers receive the first and second input voltages respectively and have output terminals coupled to two ends of the first ladder resistor string. The selector circuit is coupled to the first ladder resistor string and provides a plurality of divided voltages to the internal operational amplifier circuit. The second ladder resistor string is coupled with the internal operational amplifier circuit and outputs a plurality of gamma voltages. The first protection circuit is coupled to the output ends of the first and second external operational amplifiers and provides protection when the first and second input voltages are abnormal. The second protection circuit is coupled to the internal operational amplifier circuit and provides protection when the voltage division is abnormal.

Description

Gamma voltage generating circuit
Technical Field
The present invention relates to a source driving circuit, and more particularly, to a Gamma (Gamma) voltage generating circuit applied to a source driving circuit for a vehicle.
Background
With the importance of vehicle safety becoming more and more important and the popularization of ISO26262 specifications, the vehicle systems in the market all need to have the functional safety specified by ISO 26262.
Referring to fig. 1, fig. 1 is a schematic diagram of a source driver integrated circuit SIC for a vehicle applied to a display panel PL for a vehicle. Generally speaking, the ASIL class of the vehicle source driver integrated circuit SIC inherits its system, and is usually ASIL B class. In order to meet the functional safety specified by ISO26262 and achieve a hardware quantization index (SPFM/LFM/PMHF) above ASIL B level, each module (e.g., a gamma voltage generation circuit) included in the source driver integrated circuit SIC for a vehicle needs to have a redundant design or a safety mechanism.
However, since the conventional gamma voltage generating circuit in the source driver ic SIC for a vehicle usually has no safety mechanism, once any error occurs in the gamma voltage generating circuit, the gamma voltage provided by the gamma voltage generating circuit is abnormal, and further the abnormal phenomena such as screen flashing or line flashing occur on the image displayed on the display panel for the vehicle, which seriously violates the functional safety specified in ISO26262, and further improvement is needed.
Disclosure of Invention
Accordingly, the present invention is directed to a gamma voltage generating circuit applied to a source driving circuit for a vehicle to effectively solve the above-mentioned problems encountered in the prior art.
One embodiment according to the present invention is a gamma voltage generating circuit. In this embodiment, the gamma voltage generating circuit is applied to a source driving circuit for a vehicle. The gamma voltage generating circuit comprises a first external operational amplifier, a second external operational amplifier, a first ladder resistor string, a selector circuit, an internal operational amplifier circuit, a second ladder resistor string, a first protection circuit and a second protection circuit. One input terminal of the first external operational amplifier is coupled to the first input voltage and the other input terminal and the output terminal thereof are coupled to each other. One input terminal of the second external operational amplifier is coupled to the second input voltage and the other input terminal and the output terminal thereof are coupled to each other. The first ladder resistor string comprises a plurality of resistors which are connected in series between the output end of the first external operational amplifier and the output end of the second external operational amplifier. The selector circuit includes a plurality of selectors. Each selector in the selectors is correspondingly coupled to one end of each resistor in the resistors so as to selectively provide a plurality of voltage division. The internal operational amplification circuit includes a plurality of internal operational amplifiers. One input end of each of the internal operational amplifiers receives one of the divided voltages respectively, and the other input end and the output end of each of the internal operational amplifiers are coupled with each other. The second ladder resistor string includes a plurality of resistors connected in series between an output terminal of one of the internal operational amplifiers and an output terminal of another internal operational amplifier to output a plurality of gamma voltages, respectively. The first protection circuit is coupled to the output terminal of the first external operational amplifier and the output terminal of the second external operational amplifier, respectively, for determining whether the first input voltage and the second input voltage are abnormal, and determining whether to provide protection according to the determination result. The second protection circuit is coupled to the output ends of the internal operational amplifiers respectively, and is used for judging whether the voltages output by the internal operational amplifiers are abnormal or not so as to determine whether to provide protection or not according to the judgment result.
In one embodiment, the source driving circuit is coupled to the display panel and drives the display panel to display images.
In one embodiment, when any error occurs in the gamma voltage generating circuit in the source driving circuit for the vehicle, the gamma voltage generating circuit starts its safety mechanism, so that the image displayed by the display panel for the vehicle does not have a screen flash or a flash line to meet a specific specification.
In one embodiment, the specific specification is the ISO26262 specification.
In one embodiment, when the first input voltage is higher than the preset maximum voltage value, the first protection circuit determines that the first input voltage is an overvoltage abnormality and provides overvoltage protection; when the first input voltage is lower than the preset minimum voltage value, the first protection circuit judges that the first input voltage is abnormal under voltage and provides under voltage protection, and the preset maximum voltage value is higher than the preset minimum voltage value.
In one embodiment, when the second input voltage is higher than the preset maximum voltage value, the first protection circuit determines that the second input voltage is an overvoltage abnormality and provides overvoltage protection; when the second input voltage is lower than the preset minimum voltage value, the first protection circuit judges that the second input voltage is abnormal under voltage and provides under voltage protection, and the preset maximum voltage value is higher than the preset minimum voltage value.
In one embodiment, when at least one of the voltages output by the internal operational amplifiers is higher than a preset maximum voltage value, the second protection circuit determines that the at least one voltage is an overvoltage anomaly and provides overvoltage protection; when the at least one voltage is lower than a preset minimum voltage value, the second protection circuit judges that the at least one voltage is abnormal under voltage and provides under voltage protection; wherein, the preset highest voltage value is higher than the preset lowest voltage value.
In one embodiment, the second input voltage is lower than the first input voltage.
In one embodiment, the gamma voltage generating circuit further includes a Register circuit coupled to the selectors of the selector circuit respectively for controlling the operation of the selectors respectively.
Another embodiment according to the present invention is a gamma voltage generating circuit. In this embodiment, the gamma voltage generating circuit is applied to a source driving circuit for a vehicle. The gamma voltage generating circuit comprises a first external operational amplifier, a second external operational amplifier, a first ladder resistor string, a selector circuit, an internal operational amplifier circuit, a second ladder resistor string, a first comparison circuit and a second comparison circuit. One input terminal of the first external operational amplifier is coupled to the first input voltage and the other input terminal and the output terminal thereof are coupled to each other. One input terminal of the second external operational amplifier is coupled to the second input voltage and the other input terminal and the output terminal thereof are coupled to each other. The first ladder resistor string comprises a plurality of resistors which are connected in series between the output end of the first external operational amplifier and the output end of the second external operational amplifier. The selector circuit includes a plurality of selectors. Each selector in the selectors is correspondingly coupled to one end of each resistor in the resistors so as to selectively provide a plurality of voltage division. The internal operational amplification circuit includes a plurality of internal operational amplifiers. One input end of each of the internal operational amplifiers receives one of the divided voltages respectively, and the other input end and the output end of each of the internal operational amplifiers are coupled with each other. The second ladder resistor string includes a plurality of resistors connected in series between an output terminal of one of the internal operational amplifiers and an output terminal of another internal operational amplifier to output a plurality of gamma voltages, respectively. The first comparison circuit is coupled to the output terminal of the first external operational amplifier and the output terminal of the second external operational amplifier respectively, and is used for comparing the first input voltage with the second input voltage and judging whether the voltage is abnormal or not according to the comparison result. The second comparison circuit comprises a plurality of comparison units which are sequentially coupled with the output ends of two adjacent internal operational amplifiers in the internal operational amplifiers and used for judging whether the voltages output by the internal operational amplifiers are sequentially and monotonically increased or monotonically decreased.
In one embodiment, the vehicle source driving circuit is coupled to a vehicle display panel and drives the vehicle display panel to display a picture.
In one embodiment, when any error occurs in the gamma voltage generating circuit in the source driver circuit for the vehicle, the gamma voltage generating circuit activates its safety mechanism, so that the image displayed by the display panel for the vehicle does not have a screen flash or a flash line, thereby meeting a specific specification.
In one embodiment, the specific specification is the ISO26262 specification.
In one embodiment, the first comparator circuit is a 1-bit comparator.
In one embodiment, the comparison units in the second comparison circuit are all bit comparators.
In one embodiment, the internal operational amplifiers sequentially include a first internal operational amplifier, a second internal operational amplifier and a third internal operational amplifier, and output ends of the first internal operational amplifier, the second internal operational amplifier and the third internal operational amplifier respectively output a first voltage, a second voltage and a third voltage; the comparison units sequentially comprise a first comparison unit and a second comparison unit; the first comparing unit is coupled with the output end of the first internal operational amplifier and the output end of the second internal operational amplifier and is used for comparing the first voltage with the second voltage to generate a first comparing result; the second comparing unit is coupled to the output terminal of the second internal operational amplifier and the output terminal of the third internal operational amplifier for comparing the second voltage with the third voltage to generate a second comparison result.
In one embodiment, the first comparison result and the second comparison result are used to determine whether the first voltage, the second voltage, and the third voltage monotonically increase or monotonically decrease in sequence.
In one embodiment, if the first comparison result is that the first voltage is higher than the second voltage and the second comparison result is that the second voltage is higher than the third voltage, the first voltage, the second voltage and the third voltage are determined to be monotonically decreasing in sequence to confirm that the first internal operational amplifier, the second internal operational amplifier and the third internal operational amplifier are not abnormal.
In one embodiment, if the first comparison result is that the first voltage is lower than the second voltage and the second comparison result is that the second voltage is lower than the third voltage, the first voltage, the second voltage and the third voltage are determined to be monotonically increasing in sequence to confirm that the first internal operational amplifier, the second internal operational amplifier and the third internal operational amplifier are not abnormal.
In one embodiment, if the first comparison result is that the first voltage is lower than the second voltage but the second voltage is higher than the third voltage, or the first comparison result is that the first voltage is higher than the second voltage but the second comparison result is that the second voltage is lower than the third voltage, and the first voltage, the second voltage, and the third voltage are determined not to be monotonically increased or monotonically decreased in sequence, at least one of the first internal operational amplifier, the second internal operational amplifier, and the third internal operational amplifier is abnormal.
Compared with the prior art, the invention provides a corresponding Safety mechanism for the gamma voltage generating circuit applied to the vehicle source electrode driving circuit, and the invention can meet the requirement of ISO26262 specification on functional Safety by detecting the error in the gamma voltage generating circuit and informing the front-end system to enter a Safety State (Safety State) through a physical pin so as to achieve the hardware quantization index of the specification above the ASIL B grade.
The advantages and spirit of the present invention can be further understood by the following detailed description of the invention and the accompanying drawings.
Drawings
Fig. 1 is a schematic diagram of a source driver integrated circuit SIC for a vehicle applied to a display panel PL for a vehicle.
FIG. 2 is a schematic diagram of a gamma voltage generating circuit applied to a source driver circuit for a vehicle according to a preferred embodiment of the invention.
FIG. 3 is a schematic diagram of a gamma voltage generating circuit applied to a source driver circuit for a vehicle according to another preferred embodiment of the invention.
FIG. 4 shows an embodiment in which the comparison unit is a one-bit comparator.
Description of the main element symbols:
PL.. display panel for vehicle
DA.
Vehicle source driving integrated circuit
Gate drive integrated circuit for vehicle
Gamma voltage generation circuit
A first external operational amplifier
301
A first ladder resistor string
A selector circuit
Internal operational amplifier circuit
A second ladder resistor string
35
A second protection circuit
A register circuit
A first input voltage
A second input voltage
A + a
320-32X
330-33X
RE 0-REX
Resistance RI 0-RI (X-1)
Partial pressure from VINP0 to VINPXNX
REG 0-REGX
Register signals REGM, REGH, regl
V0-V255
Output signal of VGMPHO, VGMPLO
Input signal VGMPHI, vgmpli
OVPEH, OVPEL, OVPI 0-OVPIX
Predetermined minimum voltage value (undervoltage protection) of UVPEH, UVPEL, UVPI 0-UVPIX
Number of signals
2Y.. signal number
Gamma voltage generation circuit
A first external operational amplifier
A second external operational amplifier
A first ladder resistor string
A selector circuit
420-42X
43. internal operational amplifier circuit
430-43X
A second ladder resistor string
45.. first comparison circuit
A second comparator circuit
461-46 (X-1).. comparison unit
REG 0/1-REG (X-1)/X
A bit comparator
M1-M6.
Cs
Ground terminal
Output terminal
Voltage of V (M-1)
VM.. voltage
Detailed Description
Reference will now be made in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. The same or similar numbered elements/components used in the drawings and the embodiments are used to represent the same or similar parts.
One embodiment according to the present invention is a gamma voltage generating circuit. In this embodiment, the gamma voltage generating circuit is applied to a source driving circuit for a vehicle. The source driving circuit for the vehicle is coupled with the display panel for the vehicle and drives the display panel for the vehicle to display pictures. When any error occurs in the gamma voltage generating circuit in the source electrode driving circuit for the vehicle, the gamma voltage generating circuit can start the safety mechanism, so that the picture displayed by the display panel for the vehicle can not have a flash screen or a flash line, and the standard of ISO26262 is met.
Fig. 2 is a schematic diagram of a gamma voltage generating circuit applied to a source driver circuit for a vehicle in this embodiment.
As shown in fig. 2, the gamma voltage generating circuit 3 is applied to the source driving circuit SIC for a vehicle. The gamma voltage generation circuit 3 includes a first external operational amplifier 300, a second external operational amplifier 301, a first ladder resistor string 31, a selector circuit 32, an internal operational amplifier circuit 33, a second ladder resistor string 34, a first protection circuit 35, a second protection circuit 36, and a register circuit 37.
The first external operational amplifier 300 has one input terminal + coupled to the first input voltage VINPH and the other input terminal-and the output terminal coupled to each other. The second external operational amplifier 301 has an input terminal + coupled to the second input voltage VINPL and another input terminal-and an output terminal coupled to each other. In this embodiment, the second input voltage VINPL is lower than the first input voltage VINPH.
The first ladder resistor string 31 includes a plurality of resistors RE 0-REX. The resistors RE 0-REX are connected in series between the output of the first external operational amplifier 300 and the output of the second external operational amplifier 301.
The selector circuit 32 includes a plurality of selectors 320 to 32X. Each of the selectors 320-32X is correspondingly coupled to one end of each of the resistors RE 0-REX to selectively provide a plurality of divided voltages VINP 0-VINPXP. The register circuit 37 is coupled to the selectors 320-32X of the selector circuit 32 respectively for controlling the operation of the selectors 320-32X respectively.
The internal operational amplifier circuit 33 includes a plurality of internal operational amplifiers 330-33X. One input terminal of each of the internal operational amplifiers 330-33X receives one of the divided voltages VINP 0-VINPX, and the other input terminal and the output terminal of each of the internal operational amplifiers are coupled to each other.
The second ladder resistor string 34 includes a plurality of resistors RI 1-RI (X-1) connected in series between an output terminal of one internal operational amplifier 331 and an output terminal of another internal operational amplifier 33(X-1) of the internal operational amplifiers 330-33X to respectively output a plurality of gamma voltages.
The first protection circuit 35 is coupled to the output terminal of the first external operational amplifier 300 and the output terminal of the second external operational amplifier 301, respectively, for comparing the first input voltage VINPH with the second input voltage VINPL and accordingly determining whether there is a voltage abnormality, thereby determining whether to provide protection.
In practical applications, the first protection circuit 35 can compare the first input voltage VINPH with the preset maximum voltage value OVPEH and the preset minimum voltage value UVPEH to determine whether the first input voltage VINPH is abnormal, and then determine whether to provide protection according to the determination result. Wherein, the predetermined maximum voltage value OVPEH is higher than the predetermined minimum voltage value UVPEH.
For example, when the first input voltage VINPH is higher than the preset maximum voltage value OVPEH, the first protection circuit 35 determines that the first input voltage VINPH is an overvoltage abnormality and provides overvoltage protection (OVP); when the first input voltage VINPH is lower than the predetermined minimum voltage value UVPEH, the first protection circuit 35 determines that the first input voltage VINPH is an under-voltage abnormality and provides under-voltage protection (UVP).
Similarly, the first protection circuit 35 can compare the second input voltage VINPL with the preset maximum voltage value OVPEL and the preset minimum voltage value UVPEL to determine whether the second input voltage VINPL is abnormal, and then determine whether to provide protection according to the determination result. Wherein, the predetermined maximum voltage value OVPEL is higher than the predetermined minimum voltage value UVPEL.
When the second input voltage VINPL is higher than the preset maximum voltage value OVPEL, the first protection circuit 35 determines that the second input voltage VINPL is an overvoltage anomaly and provides overvoltage protection; when the second input voltage VINPL is lower than the predetermined minimum voltage value UVPEL, the first protection circuit 35 determines that the second input voltage VINPL is an under-voltage anomaly and provides under-voltage protection.
The second protection circuit 36 is coupled to the output terminals of the internal operational amplifiers 330-33X, respectively, for determining whether the voltages V255-V0 output by the internal operational amplifiers 330-33X are abnormal, and determining whether to provide protection according to the determination result.
In practical applications, the second protection circuit 36 can compare the voltages V255 to V0 output by the internal operational amplifiers 330 to 33X with the preset maximum voltage values OVPI0 to OVPIX and the preset minimum voltage values UVPI0 to UVPIX, respectively, to determine whether the voltages V255 to V0 output by the internal operational amplifiers 330 to 33X are abnormal, and then determine whether to provide protection according to the determination result. Wherein, the preset maximum voltage values OVPI 0-OVPIX are higher than the corresponding preset minimum voltage values UVPI 0-UVPIX.
For example, when the voltage V255 output by the internal operational amplifier 330 is higher than the preset maximum voltage value OVPI0, the second protection circuit 36 determines that the voltage V255 output by the internal operational amplifier 330 is an overvoltage anomaly and provides overvoltage protection; when the voltage V255 output by the internal operational amplifier 330 is lower than the predetermined minimum voltage value UVPI0, the second protection circuit 36 determines that the voltage V255 output by the internal operational amplifier 330 is under-voltage abnormal and provides under-voltage protection. The rest can be analogized, so that the description is omitted.
Another embodiment according to the present invention is a gamma voltage generating circuit. In this embodiment, the gamma voltage generating circuit is applied to a source driving circuit for a vehicle. The source driving circuit for the vehicle is coupled with the display panel for the vehicle and drives the display panel for the vehicle to display pictures. When any error occurs in the gamma voltage generating circuit in the source driving circuit for the vehicle, the gamma voltage generating circuit will activate its safety mechanism, so that the image displayed by the display panel for the vehicle will not have a flashing screen or a flashing line, so as to meet a specific specification, such as ISO26262 specification, but not limited thereto.
Referring to fig. 3, fig. 3 is a schematic diagram of a gamma voltage generating circuit applied to the source driving circuit for a vehicle in this embodiment.
As shown in fig. 3, the gamma voltage generating circuit 4 includes a first external operational amplifier 400, a second external operational amplifier 401, a first ladder resistor string 41, a selector circuit 42, an internal operational amplifier circuit 43, a second ladder resistor string 44, a first comparison circuit 45, and a second comparison circuit 46.
The first external operational amplifier 400 has one input terminal + coupled to the first input voltage VINPH and the other input terminal-and the output terminal coupled to each other. The second external operational amplifier 401 has an input terminal + coupled to the second input voltage VINPL and another input terminal-and an output terminal coupled to each other.
The first ladder resistor string 41 includes a plurality of resistors RE 0-REX connected in series with each other between the output terminal of the first external operational amplifier 400 and the output terminal of the second external operational amplifier 401.
The selector circuit 42 includes a plurality of selectors 420 to 42X. Each of the selectors 420-42X is correspondingly coupled to one end of each of the resistors RE 0-REX in the first ladder resistor string 41 to selectively provide a plurality of divided voltages VINP 0-VINPXPXNX.
The internal operational amplifier circuit 43 includes a plurality of internal operational amplifiers 430 to 43X. One input terminal of each of the internal operational amplifiers 430-43X receives one of the divided voltages VINP 0-VINPX, and the other input terminal and the output terminal of each of the internal operational amplifiers are coupled to each other.
The second ladder resistor string 44 includes a plurality of resistors RI 1-RI (X-1) connected in series between an output terminal of one internal operational amplifier 431 and an output terminal of another internal operational amplifier 43(X-1) of the internal operational amplifiers 430-43X to respectively output a plurality of gamma voltages.
The first comparison circuit 45 is coupled to the output terminal of the first external operational amplifier 400 and the output terminal of the second external operational amplifier 401, respectively, for comparing the first input voltage VINPH with the second input voltage VINPL and accordingly determining whether there is a voltage abnormality, thereby determining whether to provide protection.
In practical applications, the first comparing circuit 45 may compare the first input voltage VINPH with a predetermined maximum voltage value and a predetermined minimum voltage value to determine whether the first input voltage VINPH is abnormal. The preset maximum voltage value is higher than the preset minimum voltage value.
The second comparison circuit 46 includes a plurality of comparison units 461 to 46(X-1) sequentially coupled to the output terminals of two sequentially adjacent internal operational amplifiers of the internal operational amplifiers 430 to 43X for determining whether the voltages V255 to V0 output by the internal operational amplifiers 430 to 43X are sequentially monotonically increased or monotonically decreased, and determining whether to provide protection according to the determination result.
For example, the internal operational amplifiers 430-43X sequentially include internal operational amplifiers 430, 431, and 432, and the output terminals of the internal operational amplifiers 430, 431, and 432 output voltages V255, V254, and V253, respectively; the comparison units 461 to 46(X-1) sequentially include comparison units 461 and 462; the comparing unit 461 is coupled to the output terminal of the internal operational amplifier 430 and the output terminal of the internal operational amplifier 431, for comparing the voltages V255 and V254 output by the internal operational amplifier 430 and the internal operational amplifier 431, respectively, to generate a first comparison result and output a register signal REG 0/1; the comparing unit 462 is coupled to the output terminal of the internal operational amplifier 431 and the output terminal of the internal operational amplifier 432, and is used for comparing the voltages V254 and V253 output by the internal operational amplifier 431 and the internal operational amplifier 432, respectively, to generate a second comparison result and output the register signal REG 1/2.
It should be noted that the first comparison result provided by the register signal REG0/1 outputted by the comparison unit 461 and the second comparison result provided by the register signal REG1/2 outputted by the comparison unit 462 can be used to determine whether the voltages V255-V253 outputted by the internal operational amplifiers 430-432 are monotonically increasing or monotonically decreasing in sequence, which can be described in the following three cases.
If the voltage V255 is higher than the voltage V254 as the first comparison result of the comparison unit 461 and the voltage V254 is higher than the divided voltage V253 as the second comparison result of the comparison unit 462, the voltages V255-V253 output by the internal operational amplifiers 430-432 are determined to be monotonically decreased in sequence, so as to confirm that there is no abnormality in the internal operational amplifiers 430-432, and therefore, a protection mechanism is not required to be started.
If the first comparison result of the comparison unit 461 is that the voltage V255 is lower than the voltage V254 and the second comparison result of the comparison unit 462 is that the voltage V254 is lower than the divided voltage V253, the voltages V255-V253 output by the internal operational amplifiers 430-432 are determined to be monotonically increasing in sequence, so as to confirm that there is no abnormality in the internal operational amplifiers 430-432, and therefore, a protection mechanism is not required to be started.
If the first comparison result of the comparison unit 461 is that the voltage V255 is lower than the voltage V254, but the second comparison result of the comparison unit 462 is that the voltage V254 is higher than the divided voltage V253, or if the first comparison result of the comparison unit 461 is that the voltage V255 is higher than the voltage V254, but the second comparison result of the comparison unit 462 is that the voltage V254 is lower than the divided voltage V253, the voltages V255-V253 output by the internal operational amplifiers 430-432 are determined to be monotonically increasing or monotonically decreasing in a non-sequential manner (i.e., a gamma voltage inversion phenomenon occurs), which means that at least one of the internal operational amplifiers 430-432 is abnormal, and therefore the protection mechanism needs to be activated.
In practical applications, the comparing units 461 to 46(X-1) of the first comparing circuit 45 and the second comparing circuit 46 can be comparator circuits such as a 1-bit comparator, but not limited thereto.
For example, as shown in FIG. 4, a bit comparator 5 may include transistor switches M1-M6 and a current source CS. The current source CS is coupled to the transistor switches M1 and M2, respectively. The gate of transistor switch M1 is coupled to voltage V (M-1) and the gate of transistor switch M2 is coupled to voltage VM. The transistor switch M3 is coupled between the transistor switch M1 and the ground GND. The transistor switch M4 is coupled between the transistor switch M2 and the ground GND, and the gates of the transistor switches M3 and M5 are coupled to each other. The transistor switch M5 is coupled between the transistor switch M1 and the ground GND. The transistor switch M6 is coupled between the transistor switch M2 and the ground GND, and the gates of the transistor switches M5 and M6 are coupled to each other. The output OUT of a bit comparator 5 is located between the transistor switches M2 and M6.
It should be noted that the one-bit comparator 5 shown in fig. 4 is only one embodiment, and the comparison units 461 to 46(X-1) in the first comparison circuit 45 and the second comparison circuit 46 shown in fig. 3 can also be other types of comparison circuits, which is not limited thereto.
Compared with the prior art, the invention provides a corresponding Safety mechanism for the gamma voltage generating circuit applied to the vehicle source electrode driving circuit, and the invention can meet the requirement of ISO26262 specification on functional Safety by detecting the error in the gamma voltage generating circuit and informing the front-end system to enter a Safety State (Safety State) through a physical pin so as to achieve the hardware quantization index of the specification above the ASIL B grade.

Claims (20)

1. A gamma voltage generating circuit applied to a source driving circuit for a vehicle includes:
a first external operational amplifier, one input terminal of which is coupled to a first input voltage and the other input terminal of which is coupled to the output terminal of the first external operational amplifier;
a second external operational amplifier, one input terminal of which is coupled to a second input voltage and the other input terminal of which is coupled to the output terminal of the second external operational amplifier;
a first ladder resistor string including a plurality of resistors connected in series between the output terminal of the first external operational amplifier and the output terminal of the second external operational amplifier;
a selector circuit, including a plurality of selectors, each of the selectors being correspondingly coupled to one end of each of the resistors to selectively provide a plurality of divided voltages;
an internal operational amplifier circuit including a plurality of internal operational amplifiers, an input terminal of each of the internal operational amplifiers receiving one of the divided voltages respectively and another input terminal and an output terminal of each of the internal operational amplifiers being coupled to each other;
a second ladder resistor string including a plurality of resistors connected in series between an output terminal of one of the internal operational amplifiers and an output terminal of another internal operational amplifier to output a plurality of gamma voltages, respectively;
a first protection circuit, coupled to the output terminal of the first external operational amplifier and the output terminal of the second external operational amplifier, respectively, for determining whether the first input voltage and the second input voltage are abnormal, and determining whether to provide protection according to the determination result; and
and a second protection circuit coupled to the output ends of the internal operational amplifiers respectively for determining whether the divided voltages are abnormal or not so as to determine whether to provide protection or not according to the determination result.
2. The gamma voltage generating circuit of claim 1, wherein the source driver circuit is coupled to a display panel and drives the display panel to display a picture.
3. The gamma voltage generating circuit of claim 2, wherein when any error occurs in the gamma voltage generating circuit of the source driver circuit for a vehicle, the gamma voltage generating circuit will activate its safety mechanism so that the image displayed by the display panel for a vehicle will not flash or flash to meet a specific specification.
4. The gamma voltage generation circuit of claim 3, wherein the specific specification is the ISO26262 specification.
5. The gamma voltage generating circuit of claim 1, wherein the first protection circuit determines the first input voltage as an over-voltage abnormality and provides over-voltage protection when the first input voltage is higher than a predetermined maximum voltage value; when the first input voltage is lower than a preset minimum voltage value, the first protection circuit judges that the first input voltage is abnormal under voltage and provides under voltage protection, and the preset maximum voltage value is higher than the preset minimum voltage value.
6. The gamma voltage generating circuit of claim 1, wherein the first protection circuit determines the second input voltage as an over-voltage abnormality and provides over-voltage protection when the second input voltage is higher than a predetermined maximum voltage value; when the second input voltage is lower than a preset minimum voltage value, the first protection circuit judges that the second input voltage is abnormal under voltage and provides under voltage protection, and the preset maximum voltage value is higher than the preset minimum voltage value.
7. The gamma voltage generating circuit of claim 1, wherein when at least one of the divided voltages is higher than a predetermined maximum voltage value, the second protection circuit determines the at least one divided voltage as an over-voltage abnormality and provides over-voltage protection; when the at least one partial voltage is lower than a preset minimum voltage value, the second protection circuit judges that the at least one partial voltage is abnormal under voltage and provides under voltage protection; wherein, the preset highest voltage value is higher than the preset lowest voltage value.
8. The gamma voltage generating circuit of claim 1, wherein the second input voltage is lower than the first input voltage.
9. The gamma voltage generation circuit according to claim 1, further comprising:
and the register circuit is respectively coupled to the selectors in the selector circuit and is used for respectively controlling the operation of the selectors.
10. A gamma voltage generation circuit applied to a source electrode driving circuit for a vehicle is characterized by comprising:
a first external operational amplifier, one input terminal of which is coupled to a first input voltage and the other input terminal of which is coupled to the output terminal of the first external operational amplifier;
a second external operational amplifier, one input terminal of which is coupled to a second input voltage and the other input terminal of which is coupled to the output terminal of the second external operational amplifier;
a first ladder resistor string including a plurality of resistors connected in series between the output terminal of the first external operational amplifier and the output terminal of the second external operational amplifier;
a selector circuit, including a plurality of selectors, each of the selectors being correspondingly coupled to one end of each of the resistors to selectively provide a plurality of divided voltages;
an internal operational amplifier circuit including a plurality of internal operational amplifiers, one input terminal of each of the internal operational amplifiers receiving one of the divided voltages respectively and the other input terminal and the output terminal of each of the internal operational amplifiers being coupled to each other;
a second ladder resistor string including a plurality of resistors connected in series between an output terminal of one of the internal operational amplifiers and an output terminal of another internal operational amplifier to output a plurality of gamma voltages, respectively;
a first comparison circuit coupled to the output terminal of the first external operational amplifier and the output terminal of the second external operational amplifier respectively for comparing the first input voltage with the second input voltage and determining whether there is voltage abnormality; and
and the second comparison circuit comprises a plurality of comparison units which are sequentially coupled with the output ends of two adjacent internal operational amplifiers in the internal operational amplifiers and used for judging whether the voltages output by the internal operational amplifiers are sequentially and monotonically increased or monotonically decreased.
11. The gamma voltage generating circuit of claim 10, wherein the source driver circuit is coupled to a display panel for driving the display panel to display a picture.
12. The gamma voltage generating circuit of claim 11, wherein when any error occurs in the gamma voltage generating circuit of the source driver circuit for a vehicle, the gamma voltage generating circuit activates its safety mechanism so that the display screen displayed by the display panel for a vehicle does not have a flash or a wire flash to meet a specific specification.
13. The gamma voltage generation circuit of claim 12, wherein the specific specification is the ISO26262 specification.
14. The gamma voltage generating circuit of claim 10, wherein the first comparator circuit is a one-bit comparator.
15. The gamma voltage generating circuit of claim 10, wherein the comparing units of the second comparing circuit are all a bit comparator.
16. The gamma voltage generating circuit of claim 10, wherein the internal operational amplifiers sequentially comprise a first internal operational amplifier, a second internal operational amplifier and a third internal operational amplifier, and the output terminals of the first internal operational amplifier, the second internal operational amplifier and the third internal operational amplifier respectively output a first voltage, a second voltage and a third voltage; the comparison units sequentially comprise a first comparison unit and a second comparison unit; the first comparing unit is coupled with the output end of the first internal operational amplifier and the output end of the second internal operational amplifier and is used for comparing the first voltage with the second voltage to generate a first comparing result; the second comparing unit is coupled to the output terminal of the second internal operational amplifier and the output terminal of the third internal operational amplifier for comparing the second voltage with the third voltage to generate a second comparison result.
17. The gamma voltage generating circuit of claim 16, wherein the first comparison result and the second comparison result are used to determine whether the first voltage, the second voltage and the third voltage are monotonically increasing or monotonically decreasing in sequence.
18. The gamma voltage generating circuit of claim 17, wherein if the first comparison result is that the first voltage is higher than the second voltage and the second comparison result is that the second voltage is higher than the third voltage, the first voltage, the second voltage and the third voltage are determined to monotonically decrease in sequence to confirm the absence of anomalies in the first internal operational amplifier, the second internal operational amplifier and the third internal operational amplifier.
19. The gamma voltage generating circuit of claim 17, wherein if the first comparison result is that the first voltage is lower than the second voltage and the second comparison result is that the second voltage is lower than the third voltage, the first voltage, the second voltage and the third voltage are determined to be monotonically increasing in sequence to confirm that the first internal operational amplifier, the second internal operational amplifier and the third internal operational amplifier are not abnormal.
20. The gamma voltage generating circuit of claim 17, wherein if the first comparison result is that the first voltage is lower than the second voltage but the second voltage is higher than the third voltage, or the first comparison result is that the first voltage is higher than the second voltage but the second voltage is lower than the third voltage, the first voltage, the second voltage and the third voltage are determined not to be monotonically increasing or monotonically decreasing in sequence, then at least one of the first internal operational amplifier, the second internal operational amplifier and the third internal operational amplifier is abnormal.
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