CN112162586A - Circuit for driving TFT - Google Patents
Circuit for driving TFT Download PDFInfo
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- CN112162586A CN112162586A CN202011175546.2A CN202011175546A CN112162586A CN 112162586 A CN112162586 A CN 112162586A CN 202011175546 A CN202011175546 A CN 202011175546A CN 112162586 A CN112162586 A CN 112162586A
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/10—Regulating voltage or current
- G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
- G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
- G05F1/565—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor
- G05F1/569—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor for protection
Abstract
The present invention relates to a circuit for driving a TFT, comprising: the voltage reduction and current limitation circuit is used for reducing the voltage of the input voltage and limiting the current of the input voltage and then outputting a first set voltage and a first set current; the first set current is less than a set threshold current; the voltage stabilizing and shunting circuit is used for taking the first set voltage and the first set current as input, and outputting a second set voltage and a second set current by adjusting the resistance value of a potentiometer access circuit; the second setting voltage is less than the first setting voltage, and the second setting current is less than the first setting current. The ripple of the input voltage is reduced through the voltage reduction current-limiting circuit, the total current upper limit of the rear-end circuit is limited, and the voltage output by the voltage reduction current-limiting circuit is further reduced to the threshold voltage of the TFT grid electrode through the voltage stabilization shunt circuit and simultaneously provides a small current.
Description
Technical Field
The present invention relates to the field of transistor technology, and more particularly, to a circuit for driving a TFT.
Background
A TFT (thin film transistor) has a switching performance of a transistor and characteristics of a thin film, and thus is widely used in the field of flat panel display, and in addition, the application of the TFT has been extended to high-tech devices such as an artificial synapse, a sensor, and the like.
Fig. 2 shows a diode-connected TFT load common source amplifier circuit, T1 and T2 are two TFTs, and the width-to-length ratio of T1 is smaller than T2. The grid electrode and the drain electrode of the T1 are in short circuit, voltage is provided by an input1 port, and the T1 always works in a saturation region to play a role of a small-signal resistor; the drain of the T2 is connected in series with the gate of the T1, the gate voltage is provided by the input2 port, the source is grounded, and when the gate voltage of the T2 is greater than the threshold voltage and less than the voltage at the input1 port, the whole amplifying circuit is turned on, and the amplified signal is output through the output port.
When a TFT is used as a switching device, it is found that a minute current flows through a gate when the TFT is turned on in an actual test using a probe station, and the minute current flowing through the gate varies from several nanoamperes to several microamperes depending on a manufacturing process and a production lot, and the threshold voltage also varies from several tenths of volts to several volts. The conventional driving circuit cannot simultaneously guarantee that a minute current is supplied when a gate voltage for turning on T2 is supplied, resulting in a sharp drop in TFT performance and even breakdown. Most of the existing circuits capable of providing the tiny current are constant current sources, and the voltage and the tiny current required by the grid electrode when the TFT is started cannot be adjusted according to the process and the production batch of the TFT.
Disclosure of Invention
Based on this, it is an object of the present invention to provide a circuit for driving a TFT, which provides a turn-on voltage for the TFT while ensuring a minute current supply.
In order to achieve the purpose, the invention provides the following scheme:
a circuit for driving a TFT, comprising:
the voltage reduction and current limitation circuit is used for reducing the voltage of the input voltage and limiting the current of the input voltage and then outputting a first set voltage and a first set current; the first set current is less than a set threshold current;
the voltage stabilizing and shunting circuit is used for taking the first set voltage and the first set current as input, and outputting a second set voltage and a second set current by adjusting the resistance value of a potentiometer access circuit; the second setting voltage is less than the first setting voltage, and the second setting current is less than the first setting current.
Optionally, the step-down current limiting circuit includes: the low dropout linear regulator comprises a low dropout linear regulator, a resistor R1, a resistor R2, a capacitor C1, a capacitor C2 and a capacitor C3;
the input voltage is respectively connected with one end of the capacitor C1 and an input pin of the low dropout linear regulator, one end of the resistor R1 is connected with a current-limiting programming pin of the low dropout linear regulator, one end of the capacitor C2 and one end of the resistor R2 are both connected with a voltage-reducing programming pin of the low dropout linear regulator, an output pin of the low dropout linear regulator is connected with a first end of the capacitor C3, a second end of the capacitor C3, the other end of the capacitor C1, the other end of the resistor R1, the other end of the capacitor C2 and the other end of the resistor R2 are grounded.
Optionally, the voltage stabilizing shunt circuit includes: the voltage reference chip, the resistor R3, the resistor R4, the potentiometer R5, the capacitor C4 and the capacitor C5 are connected in parallel;
one end of the capacitor C4 is connected with one end of the resistor R3 and the first end of the capacitor C3, the other end of the resistor R3 is connected with one end of the resistor R4, one end of the capacitor C5 and the pin No. 2 of the parallel voltage reference chip, the other end of the resistor R4 is connected with the pin No. 1 of the parallel voltage reference chip and the pin No. 2 of the potentiometer R5, the other end of the capacitor C4 is grounded, the other end of the capacitor C5, the pin No. 3 of the parallel voltage reference chip and the pin No. 3 of the potentiometer R5 are grounded, and the pin No. 1 of the potentiometer R5 is left empty.
Optionally, the low dropout linear regulator is an LT3045 chip.
Optionally, the internal reference voltage of the parallel voltage reference chip is 1.24V.
Optionally, the parallel voltage reference chip is a chip LM 4051.
Optionally, a first configuration pin of the feedback regulation of the low dropout regulator is empty, and a second configuration pin of the feedback regulation of the low dropout regulator is connected to the input voltage.
Optionally, the input voltage is a 12V dc voltage.
Optionally, the first setting voltage is a 9V dc voltage, and the setting threshold current is a 5mA current.
Optionally, the output voltage of pin No. 2 of the parallel voltage reference chip is
Wherein, VoutRepresents the output voltage, VrefRepresents the reference voltage of the parallel voltage reference chip, R5 represents the potentiometer R5, R4 represents the resistor R4.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention discloses a circuit for driving a TFT, comprising: the voltage reduction and current limitation circuit is used for reducing the voltage of the input voltage and limiting the current of the input voltage and then outputting a first set voltage and a first set current; the first set current is less than a set threshold current; the voltage stabilizing and shunting circuit is used for taking the first set voltage and the first set current as input, and outputting a second set voltage and a second set current by adjusting the resistance value of a potentiometer access circuit; the second setting voltage is less than the first setting voltage, and the second setting current is less than the first setting current. The ripple of the input voltage is reduced through the voltage reduction current-limiting circuit, the total current upper limit of the rear-end circuit is limited, and the voltage output by the voltage reduction current-limiting circuit is further reduced to the threshold voltage of the TFT grid electrode through the voltage stabilization shunt circuit and simultaneously provides a small current.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a schematic diagram of a circuit structure for driving a TFT according to the present invention;
fig. 2 is a TFT load common source amplifier circuit.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It is an object of the present invention to provide a circuit for driving a TFT which provides a turn-on voltage for the TFT while ensuring a minute current supply.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Fig. 1 is a schematic circuit diagram of a driving TFT according to the present invention, and as shown in fig. 1, a driving TFT circuit includes:
the voltage reduction and current limitation circuit is used for reducing the voltage of the input voltage and limiting the current of the input voltage and then outputting a first set voltage and a first set current; the first set current is less than a set threshold current;
the voltage stabilizing and shunting circuit is used for taking the first set voltage and the first set current as input, and outputting a second set voltage and a second set current by adjusting the resistance value of a potentiometer access circuit; the second setting voltage is less than the first setting voltage, and the second setting current is less than the first setting current.
The step-down current-limiting circuit includes: the low dropout linear regulator comprises a low dropout linear regulator, a resistor R1, a resistor R2, a capacitor C1, a capacitor C2 and a capacitor C3;
the input voltage is respectively connected with one end of the capacitor C1 and an input pin of the low dropout linear regulator, one end of the resistor R1 is connected with a current-limiting programming pin of the low dropout linear regulator, one end of the capacitor C2 and one end of the resistor R2 are both connected with a voltage-reducing programming pin of the low dropout linear regulator, an output pin of the low dropout linear regulator is connected with a first end of the capacitor C3, a second end of the capacitor C3, the other end of the capacitor C1, the other end of the resistor R1, the other end of the capacitor C2 and the other end of the resistor R2 are grounded. A first configuration pin of feedback regulation of the low dropout linear regulator is empty, and a second configuration pin of feedback regulation of the low dropout linear regulator is connected with input voltage.
The voltage stabilizing shunt circuit comprises: the voltage reference chip, the resistor R3, the resistor R4, the potentiometer R5, the capacitor C4 and the capacitor C5 are connected in parallel;
one end of the capacitor C4 is connected with one end of the resistor R3 and the first end of the capacitor C3, the other end of the resistor R3 is connected with one end of the resistor R4, one end of the capacitor C5 and the pin No. 2 of the parallel voltage reference chip, the other end of the resistor R4 is connected with the pin No. 1 of the parallel voltage reference chip and the pin No. 2 of the potentiometer R5, the other end of the capacitor C4 is grounded, the other end of the capacitor C5, the pin No. 3 of the parallel voltage reference chip and the pin No. 3 of the potentiometer R5 are grounded, and the pin No. 1 of the potentiometer R5 is left empty.
The low dropout linear regulator is an LT3045 chip.
The internal reference voltage of the parallel voltage reference chip is 1.24V. The parallel voltage reference chip is a chip LM 4051.
The input voltage is 12V direct current voltage.
The first set voltage is 9V direct current voltage, and the set threshold current is 5mA current.
The circuit structure for driving a TFT according to the present invention will be further described below.
The input voltage of the voltage reduction current-limiting circuit is +12V direct-current voltage, the +12V direct-current voltage outputs first set voltage and first set current after voltage reduction and current limitation, the first set voltage is +9V voltage, the first set current is current not higher than 5mA, the first set voltage and the first set current are directly input into the voltage stabilization shunt circuit, the voltage stabilization shunt circuit can adjust the output voltage by adjusting the resistance value of the potentiometer access circuit, the final output voltage range of the voltage stabilization shunt circuit is 1.24V-3.02V, the output current can reach microampere or even nanoampere level according to the requirement of driving a TFT, and therefore the grid electrode of the TFT is prevented from being broken down by overlarge current.
(1) Voltage-reducing current-limiting circuit
The purpose of the step-down current-limiting circuit is to reduce the ripple of the input voltage and to limit the total current upper limit of the back-end circuit (the voltage-stabilizing shunt circuit).
The buck current-limiting circuit comprises an LDO (Low Dropout Regulator) chip LT3045, a resistor R1, a resistor R2, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C1, a capacitor C2, and a capacitor C3 which are decoupling capacitors, and a resistor R1 and a resistor R2 which are configuration resistors.
The output voltage ripple level of the LT3045 chip is in a microvolt level, so that the input voltage fluctuation of the rear-end voltage stabilization shunt circuit is small, the surge voltage and the surge current are inhibited, and the efficiency of the whole circuit is improved. The LT3045 chip is packaged by DFN, has 10 pins in total, has small bonding pad area, and can reduce the size of the circuit board.
No. 1 and No. 2 pins of the LT3045 chip are input pins, are in short circuit with the No. 3 pin and are connected with the input +12V direct-current voltage. The decoupling capacitor C1 has one end connected to an input signal and the other end connected to ground. The input signal is filtered by a decoupling capacitor C1 and then input into the LT3045 chip, and the decoupling capacitor C1 filters alternating current interference superposed on the input signal and reduces input voltage ripples. No. 4 pin and No. 6 pin are configuration pins of chip output feedback regulation, when the feedback regulation is selected, the reaction time of chip output is obviously shortened, but the reaction time is irrelevant to the requirement of a driving TFT circuit, and in order to reduce the chip power and reduce the chip heating, the invention selects not to use the feedback regulation, so that the No. 4 pin is empty, and the No. 6 pin is directly connected with +12V direct current voltage. Pin 5 is a current limiting programming pin, and the resistance connected between pin 5 and ground can be according to the formula
To limit the highest current output by the chip, wherein I is the highest current output by the LT3045 chip, i.e. a set threshold current, and the unit is mA; r1 is a resistor R1 with unit of k omega, and one end of the resistor R1 is connected with a No. 5 leadThe pin and the other end are grounded. Pin No. 7 is a step-down programming pin, and a resistor R2 connected between pin No. 7 and ground can determine the voltage output by the chip step-down current-limiting circuit according to the formula U ═ 0.1mA · R2, where U represents the output voltage of the step-down current-limiting circuit, i.e., a first set voltage, and has a unit of V; r2 represents a resistor R2 with the unit of k omega, one end of the resistor R2 is connected with the No. 7 pin, and the other end is grounded. The capacitor C2 is connected in parallel to two ends of the resistor R2, so that noise can be reduced, and the ripple of the output voltage can be reduced. Pin No. 8 is a ground pin, directly grounded. Pin No. 9 and pin No. 10 are output pins of the LT3045 chip, the output voltage value U is a value obtained by substituting the resistance value of the configuration resistor R2 connected in series with pin No. 7 into a formula, and the maximum output current value I is a value obtained by substituting the resistance value of the configuration resistor R1 connected in series with pin No. 5 into a formula. The decoupling capacitor C3 has one end connected to the output signal and the other end connected to ground. The output signal is filtered by a decoupling capacitor C3 and then input into a post-stage circuit, so that noise waves can be filtered out, and output voltage ripples can be further reduced.
(2) Voltage-stabilizing shunt circuit
The purpose of the voltage stabilizing shunt circuit is to further reduce the output voltage (first set voltage) of the step-down current limiting circuit to the TFT gate threshold voltage, providing output current in microampere or even nanoamp level.
The voltage stabilizing and shunting circuit comprises a parallel voltage reference chip LM4051, a resistor R3, a resistor R4, a potentiometer R5, a capacitor C4 and a capacitor C5. The resistor R3 is a current-limiting resistor, the resistor R4 is a fixed-resistance resistor, the potentiometer R5, the capacitor C4 and the capacitor C5 are decoupling capacitors, and the parallel voltage reference chip is a chip LM 4051.
Chip LM4051 has an internal reference voltage Vref，VrefIs typically 1.24V, which may vary by no more than 20% at different operating temperatures in the range-40 c to 125 c. The ripple level of the output voltage of the chip LM4051 is also in the microvolt level, so that the voltage fluctuation supplied to the grid electrode of the TFT is small, the damage rate of the TFT can be reduced, and the service life of the TFT can be prolonged.
The voltage stabilizing and current dividing circuit is connected in series behind the voltage reducing and current limiting circuit, one end of the capacitor C4 is connected with the output end of the voltage reducing and current limiting circuit, and the other end is grounded. Filtered by a capacitor C4, the voltage reduction and current limiting circuit inputs signals of +9V direct-current voltage and maximum 5mA current which are subjected to voltage reduction and current limiting to the voltage stabilizing and shunting circuit.
The input signal flows through resistor R3 into the regulated shunt circuit. By the formula
And calculating the voltage output by the chip LM 4051. Wherein, VoutIs the output voltage, V, of the voltage-stabilizing shunt circuitoutA second set voltage for supplying a gate voltage of the TFT; r4 is a resistor R4, one end of which is connected with a current-limiting resistor R3 and the No. 2 pin of the chip LM4051, and the other end of which is connected with the No. 1 pin of the chip LM 4051; r5 is potentiometer R5, pin No. 1 of potentiometer R5 is empty, pin No. 2 of potentiometer R5 is connected with pin No. 1 of chip LM4051 at one end, and pin No. 3 of potentiometer R5 is connected with pin No. 3 of chip LM 4051. By the formula
Therefore, the output voltage of the voltage stabilizing shunt circuit can be adjusted within a certain range by adjusting the resistance value between the pins 2 and 3 of the potentiometer R5. Pin No. 3 of the chip LM4051 is grounded, and pin No. 2 is an output pin for connecting the gate of the TFT to be driven. A capacitor C5 is connected between the output pin and ground to reduce noise in the output signal.
The resistor R3 determines the input current I of the voltage-stabilizing shunt circuit1，I1The current is a first set current which cannot be larger than the maximum output current I of the buck current-limiting circuit. I is1Can be represented by formula
Calculation of, wherein1The input current of the voltage stabilizing shunt circuit is in mA unit; u is the output voltage of the voltage reduction current limiting circuit, and the unit is V; r3 is a resistor R3 with the unit of k omega, one end of R3 is connected with the output pin of the chip LM3045, and the other end is connected with pin No. 2 of the chip LM4051 and the resistor R4.
When the chip LM4051 works, the current on the No. 1 pin is only a few nanoamperes, and the branch currents of the resistor R4 and the potentiometer R5 areHundreds of microamperes, so after neglecting the current on pin No. 1 of chip LM4051, the input current I of the voltage-stabilizing shunt circuit1The flow direction includes: the current I flows through a resistor R4 and a resistor branch of a potentiometer R52Chip LM4051 working reverse current I3And an output current Iout。I2The calculation formula of (2) is as follows:
wherein, I2The unit is mA; the unit of the resistor R4 and the resistor R5 is k omega; voutThe unit is V. By the formula
It can be seen that after resistor R4 is selected, current I2Can be considered approximately a constant value.
Due to the input current I of the voltage-stabilizing shunt circuit1And the resistance branch current I2Are all fixed values which can be calculated, therefore, the chip LM4051 works with the reverse current I3And an output current IoutThe sum is also constant. When driving the TFT, IoutThe tiny current flowing through the TFT gate when supplying the TFT gate voltage is determined by the conduction condition of the TFT to be driven; i is3Is the current shunted by the voltage-stabilizing shunt circuit, I3Is calculated by the formula I3＝I1-I2-Iout。
The minimum reverse current for the LM4051 chip to work is 60uA, and the maximum reverse current is 12 mA. For LM4051 to work normally and to output a voltage and a small current that can drive the TFT gate, I3Preferably in the range of 60uA to 1 mA. Therefore, the input current flowing through the voltage-stabilizing shunt circuit can be reduced to be below 1mA by selecting the resistor R3 with large resistance value, and then I can be calculated by selecting the resistor R4 with fixed resistance value with proper resistance value2After the value of (A), I can be estimated3The size of (2). The voltage-stabilizing shunt circuit can be used for stabilizing microampere and milliampere current I3The current I is divided by the chip LM4051outThe order of magnitude of the gate electrode of the driving TFT varies from several nanoamperes to several microamperes depending on the TFT manufacturing process and production lot.
The invention can realize the aim of the invention without using the LDO, and the aim of the invention can be realized by replacing the LDO with other parallel voltage reference (such as LM4041) with 1.24V reference voltage.
When the output voltage is larger than or close to the TFT threshold voltage, the invention can change the maximum output current (set threshold current) of the voltage reduction current limiting circuit by replacing the resistor R1, change the output voltage (first set voltage) of the voltage reduction current limiting circuit by replacing the resistor R2, change the total current (first set current) of the voltage stabilization shunt circuit by replacing the resistor R3, and change the current I of the resistor branch circuit in the voltage stabilization shunt circuit by replacing the resistor R42The maximum output voltage of the voltage stabilizing shunt circuit can be changed by replacing the maximum resistance value of the potentiometer R5.
The technical effects of the circuit for driving the TFT of the invention are as follows:
1. the drivable TFT has wide grid range and strong adaptability.
Output voltage can be adjusted within a certain range by adjusting the resistance value of a potentiometer connecting circuit in the voltage stabilizing shunt circuit, so that the TFT grid electrode breakover voltage produced by different processes and production batches is adapted.
In the voltage stabilizing and shunting circuit, the parallel voltage reference can not only provide adjustable output voltage with small ripple, but also shunt microampere and milliamp-level current. Compared with a constant current source, the invention can adapt to the current requirements of TFT conduction produced by different processes and production batches, and has stronger flexibility.
2. The driven TFT has stable work and long service life.
The invention uses the LDO with microampere low ripple and the parallel voltage reference, and simultaneously, the decoupling resistors are connected in parallel at the input end and the output end of each level of signal, so as to filter and reduce noise of the input signal and the output signal of each level to the maximum extent, thereby stabilizing the voltage ripple finally output by the circuit to dozens of microvolts, ensuring that the TFT works under stable voltage and prolonging the service life of the TFT.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (10)
1. A circuit for driving a TFT, the circuit comprising:
the voltage reduction and current limitation circuit is used for reducing the voltage of the input voltage and limiting the current of the input voltage and then outputting a first set voltage and a first set current; the first set current is less than a set threshold current;
the voltage stabilizing and shunting circuit is used for taking the first set voltage and the first set current as input, and outputting a second set voltage and a second set current by adjusting the resistance value of a potentiometer access circuit; the second setting voltage is less than the first setting voltage, and the second setting current is less than the first setting current.
2. The circuit according to claim 1, wherein the step-down current limiting circuit comprises: the low dropout linear regulator comprises a low dropout linear regulator, a resistor R1, a resistor R2, a capacitor C1, a capacitor C2 and a capacitor C3;
the input voltage is respectively connected with one end of the capacitor C1 and an input pin of the low dropout linear regulator, one end of the resistor R1 is connected with a current-limiting programming pin of the low dropout linear regulator, one end of the capacitor C2 and one end of the resistor R2 are both connected with a voltage-reducing programming pin of the low dropout linear regulator, an output pin of the low dropout linear regulator is connected with a first end of the capacitor C3, a second end of the capacitor C3, the other end of the capacitor C1, the other end of the resistor R1, the other end of the capacitor C2 and the other end of the resistor R2 are grounded.
3. The circuit according to claim 1, wherein the voltage stabilizing shunt circuit comprises: the voltage reference chip, the resistor R3, the resistor R4, the potentiometer R5, the capacitor C4 and the capacitor C5 are connected in parallel;
one end of the capacitor C4 is connected with one end of the resistor R3 and the first end of the capacitor C3, the other end of the resistor R3 is connected with one end of the resistor R4, one end of the capacitor C5 and the pin No. 2 of the parallel voltage reference chip, the other end of the resistor R4 is connected with the pin No. 1 of the parallel voltage reference chip and the pin No. 2 of the potentiometer R5, the other end of the capacitor C4 is grounded, the other end of the capacitor C5, the pin No. 3 of the parallel voltage reference chip and the pin No. 3 of the potentiometer R5 are grounded, and the pin No. 1 of the potentiometer R5 is left empty.
4. The circuit for driving a TFT according to claim 2, wherein the low dropout linear regulator is an LT3045 chip.
5. The circuit for driving a TFT according to claim 3, wherein the internal reference voltage of the parallel voltage reference chip is 1.24V.
6. The circuit for driving a TFT according to claim 3, wherein the parallel voltage reference chip is a chip LM 4051.
7. The circuit according to claim 2, wherein a first configuration pin of the feedback regulator of the LDO is empty, and a second configuration pin of the feedback regulator of the LDO is connected to the input voltage.
8. The circuit according to claim 1, wherein the input voltage is a 12V DC voltage.
9. The circuit according to claim 1, wherein the first set voltage is a 9V DC voltage, and the set threshold current is a 5mA current.
10. The circuit for driving TFT according to claim 3, wherein the output voltage of pin 2 of the parallel voltage reference chip is
Wherein, VoutRepresents the output voltage, VrefRepresents the reference voltage of the parallel voltage reference chip, R5 represents the potentiometer R5, R4 represents the resistor R4.
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