Transmitting circuit, control method and infrared touch screen

Abstract

The present invention discloses a transmitting circuit, a control method and an infrared touch screen, which include a control unit, an adjusting unit and a switching unit; the adjusting unit includes at least one first emitter follower and at least one second emitter follower, the input end of the first emitter follower is connected to the control unit for receiving an input voltage; the switching unit includes at least one first analog switch and at least one second analog switch, the first analog switch is respectively connected to the first emitter follower, the second emitter follower and the second analog switch, the second analog switch is connected to the second emitter follower, and the first analog switch and the second analog switch are connected to the control unit. The present invention can expand the voltage range of the input voltage, thereby expanding the range of the output voltage, meeting the requirements of different emitting tubes, ensuring the normal use of the touch screen, and improving the user experience.

Description

Technical Field

[0001] The present invention relates to the technical field of infrared touch screens, and particularly to a transmitting circuit, a control method, and an infrared touch screen. Background Art

[0002] Currently, in the design of the transmitting circuit for driving the transmitting lamp tubes in the infrared touch screen circuit board, the MCU's DAC pin directly outputs an analog voltage value to an operational amplifier, and then the emitter follower is used to adjust the driving current, thereby adjusting the emission current of the transmitting lamp tubes. The power supply voltage of the MCU is 3.3V, and the GND power supply is 0V. Generally, the starting voltage of the driving triode is 1V. At the same time, there is a voltage drop of 0.7V after the DAC passes through the emitter follower. Therefore, the output voltage range of the existing transmitting circuit is 1.7V to 3.3V, resulting in a relatively high minimum value and a relatively low maximum value.

[0003] For the same transmitting lamp tube applied to touch screens of different sizes, or for the same size of touch screen with different transmitting lamp tubes, due to the different angles of the transmitting lamp tubes and the different emission distances of touch screens of different sizes, the driving voltage values (output voltage of the transmitting circuit) required for the same emission current are also different. To ensure the normal operation of different transmitting lamp tubes, the required driving voltage may exceed the maximum value of the output voltage of the existing transmitting circuit or be lower than the minimum value of the existing transmitting circuit, thus affecting the use of the touch screen and reducing the user experience. Summary of the Invention

[0004] The transmitting circuit, control method, and infrared touch screen provided by the present invention can meet the requirements of the transmitting lamp tubes for the driving voltage in various scenarios, ensure the normal use of the touch screen, and improve the user experience.

[0005] In a first aspect, the present invention provides a transmitting circuit, which includes a control unit, an adjusting unit, and a switching unit; the adjusting unit includes at least one first emitter follower and at least one second emitter follower. The input end of the first emitter follower is connected to the control unit for receiving an input voltage. Among them, the first emitter follower is used to increase the upper and lower limits of the input voltage, and the second emitter follower is used to decrease the upper and lower limits of the input voltage; the switching unit includes at least one first analog switch and at least one second analog switch. The first analog switch is respectively connected to the first emitter follower, the second emitter follower, and the second analog switch. The second analog switch is connected to the second emitter follower. The first analog switch and the second analog switch are also connected to the control unit; wherein, the connection states of the first analog switch and the second analog switch can be controlled by the control unit to adjust the upper and lower limits of the input voltage.

[0006] Further, the first analog switch includes a first common terminal, a first normally open terminal, a first normally closed terminal, and a first controlled terminal, and the second analog switch includes a second common terminal, a second normally open terminal, a second normally closed terminal, and a second controlled terminal; the first common terminal is connected to the first emitter follower, the first normally open terminal is connected to the second emitter follower, the first normally closed terminal is connected to the second normally closed terminal, the second normally open terminal is connected to the second emitter follower, the second common terminal is used to output a voltage signal, and both the first controlled terminal and the second controlled terminal are connected to the control unit.

[0007] Further, the first emitter follower includes a first triode; the base of the first triode is connected to the control unit, its emitter is connected to the first common terminal, and its collector is grounded.

[0008] Further, the first emitter follower further includes a first resistor and a second resistor; one end of the first resistor is connected to the control unit, the other end of the first resistor is connected to one end of the second resistor, and the other end of the second resistor is connected to the first common terminal.

[0009] Further, the second emitter follower includes a second triode; the base of the second triode is connected to the first normally open terminal, its emitter is connected to the second normally closed terminal, and its collector is grounded.

[0010] Further, the second emitter follower further includes a third resistor and a fourth resistor; one end of the third resistor is connected to the first normally open terminal, the other end of the third resistor and one end of the fourth resistor are both grounded, and the other end of the fourth resistor is connected to the second normally closed terminal.

[0011] Further, the adjustment unit includes two of the first emitter followers and two of the second emitter followers, and the switch unit includes two of the first analog switches and two of the second analog switches. Among them, the two first emitter followers are a first-level emitter follower and a second-level emitter follower respectively, the two second emitter followers are a third-level emitter follower and a fourth-level emitter follower respectively, the two first analog switches are a first-level analog switch and a second-level analog switch respectively, and the two second analog switches are a third-level analog switch and a fourth-level analog switch respectively.

[0012] Further, the first - stage emitter follower is connected to the first common terminal of the first - stage analog switch. The normally - open terminal of the first - stage analog switch is connected to the second - stage emitter follower. The second - stage emitter follower is connected to the first normally - closed terminal of the second - stage analog switch. The first normally - open terminal of the second - stage analog switch is connected to the third - stage emitter follower. The third - stage emitter follower is connected to the second normally - closed terminal of the third - stage analog switch. The second common terminal of the third - stage analog switch is connected to the fourth - stage emitter follower. The fourth - stage emitter follower is connected to the second normally - open terminal of the fourth - stage analog switch. The common terminal of the fourth - stage analog switch is used to output the voltage signal. The first controlled terminals of the first - stage analog switch and the second - stage analog switch, and the second controlled terminals of the third - stage analog switch and the fourth - stage analog switch are all connected to the control unit. The first normally - closed terminal of the first - stage analog switch, the first common terminal of the second - stage analog switch, the second normally - open terminal of the third - stage analog switch, and the second normally - closed terminal of the fourth - stage analog switch are connected in parallel.

[0013] In a second aspect, the present invention further provides a control method, which includes:

[0014] If an adjustment instruction for adjusting the input voltage is received, confirm the type of the adjustment instruction. Among them, the adjustment instruction includes a first instruction and a second instruction. The first instruction is used to increase the upper and lower limits of the input voltage, and the second instruction is used to decrease the upper and lower limits of the input voltage.

[0015] If the type of the adjustment instruction is the first instruction, control the first analog switch to be connected to the second analog switch.

[0016] If the type of the adjustment instruction is the second instruction, control the first analog switch to be connected to the second emitter follower, and control the second analog switch to be connected to the second emitter follower.

[0017] In a third aspect, the present invention further provides an infrared touch screen, which includes the emission circuit described in any one of the above.

[0018] The emission circuit, control method, and infrared touch screen provided by the present invention can increase the upper and lower limits of the input voltage through the first emitter follower, and decrease the upper and lower limits of the input voltage through the second emitter follower. At the same time, by increasing the number of the first emitter follower and the second emitter follower, the upper and lower limits of the input voltage can be further increased and decreased, so as to meet the requirements of the emission current of the emission lamp tube for the driving voltage in different scenarios, ensure the normal use of the touch screen, and improve the user experience. Description of the Drawings

[0019] To more clearly illustrate the technical solution of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 It is a block diagram of a transmission circuit provided by an embodiment of the present invention;

[0021] Figure 2 It is a block diagram of a transmission circuit provided by another embodiment of the present invention;

[0022] Figure 3 It is a functional logic diagram of a transmission circuit provided by an embodiment of the present invention;

[0023] Figure 4 It is a circuit diagram of a transmission circuit provided by an embodiment of the present invention;

[0024] Figure 5 It is a circuit diagram of a transmission circuit provided by another embodiment of the present invention;

[0025] Figure 6 It is a flow diagram of a control method provided by another embodiment of the present invention. Detailed implementation manners

[0026] The following will clearly and completely describe the technical solutions in the present invention in conjunction with the drawings in the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0027] It should be understood that when used in this specification and the appended claims, the terms "comprises" and "comprising" indicate the presence of the described features, wholes, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or their combinations.

[0028] It should also be understood that the terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in this specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms. It should also be further understood that the term " / and / " used in this specification of the present invention and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0029] See Figures 1 to 5 , Figure 1 which is a schematic block diagram of a transmission circuit provided by an embodiment of the present invention; Figure 2 which is a schematic block diagram of a transmission circuit provided by another embodiment of the present invention; Figure 3 which is a functional logic diagram of a transmission circuit provided by an embodiment of the present invention; Figure 4 which is a circuit diagram of a transmission circuit provided by an embodiment of the present invention;

[0030] Figure 5 which is a circuit diagram of a transmission circuit provided by another embodiment of the present invention. As shown in the figure, the transmission circuit provided by the present invention includes a control unit 10, an adjustment unit 20, and a switch unit 30; the adjustment unit 20 includes at least one first emitter follower 21 and at least one second emitter follower 22. The input end of the first emitter follower 21 is connected to the control unit 10 for receiving an input voltage. Among them, the first emitter follower 21 is used to increase the upper and lower limits of the input voltage, and the second emitter follower 22 is used to decrease the upper and lower limits of the input voltage; the switch unit 30 includes at least one first analog switch 31 and at least one second analog switch 32. The first analog switch 31 is respectively connected to the first emitter follower 21, the second emitter follower 22, and the second analog switch 32. The second analog switch 32 is connected to the second emitter follower 22. The first analog switch 31 and the second analog switch 32 are also connected to the control unit 10; among them, the connection states of the first analog switch 31 and the second analog switch 32 can be controlled by the control unit 10 to adjust the upper and lower limits of the input voltage.

[0031] Specifically, the adjustment unit 20 may include a plurality of first emitter followers 21 and a plurality of second emitter followers 22. Among them, the first emitter follower 21 and the second emitter follower 22 are generally a set of followers, and the numbers of both increase or decrease simultaneously. The first emitter follower 21 is mainly used to increase the upper and lower limits of the input voltage, that is, the first emitter follower 21 can raise the lower limit value and the upper limit value of the input voltage. Generally, the second emitter follower 22 is mainly used to lower the upper and lower limits of the input voltage. The first analog switch 31 is respectively connected to the first emitter follower 21, the second emitter follower 22, and the second analog switch 32. The second analog switch 32 is also connected to the second emitter follower 22. At the same time, both the first analog switch 31 and the second analog switch 32 are connected to the control unit 10. The input voltage is output by the control unit 10 and input to the first emitter follower 21. The control unit 10 can adjust the connection states of the first analog switch 31 and the second analog switch 32 according to the user's instruction or the driving voltage required by the emitting lamp tube to increase or decrease the upper and lower limits of the input voltage. For example, if it is necessary to increase the input voltage, the first analog switch 31 and the second analog switch 32 can be controlled to be connected, so that the input voltage is first input to the first emitter follower 21 for voltage increase and then directly output through the second analog switch 32. It should be noted that generally, the input voltage needs to be amplified. Therefore, the input voltage is default to pass through the first emitter follower 21. If it is necessary to keep the input voltage unchanged, the first analog switch 31 and the second analog switch 32 can be controlled to be connected to the second emitter follower 22, so that the input voltage is first input to the first emitter follower 21 for voltage increase, then input to the second emitter follower 22 for voltage decrease, and finally output through the second analog switch 32, so as to keep the input voltage unchanged. In addition, the absolute value of the voltage increased by the first emitter follower 21 is the same as the absolute value of the voltage increased by the second emitter follower 22.

[0032] Through the above process, the range of the final output voltage can be flexibly adjusted to meet the requirements of different driving voltages for the emission current of the emitting lamp tube. If a higher or lower output voltage is required, the numbers of the first emitter follower 21 and the second emitter follower 22 can be correspondingly increased. Therefore, the numbers of the first emitter follower 21 and the second emitter follower 22 are not limited here and can be determined by the driving voltage required by the emitting lamp tube.

[0033] As a further embodiment, the first analog switch 31 includes a first common terminal COM1, a first normally open terminal NO1, a first normally closed terminal NC1, and a first controlled terminal. The second analog switch 32 includes a second common terminal COM2, a second normally open terminal NO2, a second normally closed terminal NC2, and a second controlled terminal. The first common terminal COM1 is connected to the first emitter follower 21. The first normally open terminal NO1 is connected to the second emitter follower 22. The first normally closed terminal NC1 is connected to the second normally closed terminal NC2. The second normally open terminal NO2 is connected to the second emitter follower 22. The second common terminal COM2 is used to output a voltage signal. Both the first controlled terminal and the second controlled terminal are connected to the control unit 10.

[0034] Among them, as Figure 4 shown, both the first analog switch 31 and the second analog switch 32 can be double-throw switches. By controlling the connection states of the first analog switch 31 and the second analog switch 32 by the control unit 10, the upper and lower limit values of the input voltage are adjusted. For example, when the first common terminal COM1 is connected to the first normally closed terminal NC1 and the second common terminal COM2 is connected to the second normally closed terminal NC2, the input voltage is output through the first emitter follower 21, the first analog switch 31, and the second analog switch 32, and the upper and lower limit values of the input voltage can be increased. When the first common terminal COM1 is connected to the first normally open terminal NO1 and the second common terminal COM2 is connected to the second normally open terminal NO2, the input voltage is output through the first emitter follower 21, the first analog switch 31, the second emitter follower 22, and the second analog switch 32, and the finally output voltage remains unchanged.

[0035] As a further embodiment, the first emitter follower 21 includes a first triode Q1. The base of the first triode Q1 is connected to the control unit 10. Its emitter is connected to the first common terminal COM1. Its collector is grounded.

[0036] Among them, the first triode Q1 can be a PNP type triode. The input voltage flows in from the base of the first triode Q1 and flows out from the emitter. The upper and lower limit values of the input voltage increase by 0.7V.

[0037] As a further embodiment, the first emitter follower 21 further includes a first resistor R1 and a second resistor R2. One end of the first resistor R1 is connected to the control unit 10. The other end of the first resistor R1 is connected to one end of the second resistor R2. The other end of the second resistor R2 is connected to the first common terminal COM1.

[0038] Among them, the first resistor R1 is a pull-up resistor, which is used to provide a stable level for the first triode Q1 to prevent malfunction caused by noise interference in the floating state. The second resistor R2 is used to control the magnitude of the current output by the corresponding emitter follower.

[0039] As a further embodiment, the second emitter follower 22 includes a second triode Q2; the base of the second triode Q2 is connected to the first normally open terminal NO1, its emitter is connected to the second normally closed terminal NC2, and its collector is grounded.

[0040] Among them, the second triode Q2 can be an NPN-type triode. The input voltage is input from the base of the second triode Q2 and output from the emitter, and the upper and lower limit values of the input voltage are reduced by 0.7V.

[0041] As a further embodiment, the second emitter follower 22 further includes a third resistor R3 and a fourth resistor R4; one end of the third resistor R3 is connected to the first normally open terminal NO1, the other ends of the third resistor R3 and the fourth resistor R4 are both grounded, and the other end of the fourth resistor R4 is connected to the second normally closed terminal NC2.

[0042] Among them, the third resistor R3 is a pull-up resistor, which is used to provide a stable level for the second triode Q2 to prevent malfunction caused by noise interference in the floating state. The fourth resistor R4 is used to control the magnitude of the current output by the corresponding emitter follower.

[0043] As a further embodiment, the adjustment unit 20 includes two of the first emitter followers 21 and two of the second emitter followers 22, and the switch unit 30 includes two of the first analog switches 31 and two of the second analog switches 32. Among them, the two first emitter followers 21 are a primary emitter follower and a secondary emitter follower respectively, the two second emitter followers 22 are a tertiary emitter follower and a quaternary emitter follower respectively, the two first analog switches 31 are a primary analog switch and a secondary analog switch respectively, and the two second analog switches 32 are a tertiary analog switch and a quaternary analog switch respectively.

[0044] Among them, as Figure 2 and Figure 3As shown in the figure, when the input voltage passes through a first-stage emitter follower or a second-stage emitter follower, the upper and lower limit values of the input voltage increase. When it passes through a third-stage emitter follower or a fourth-stage emitter follower, the upper and lower limit values of the input voltage decrease. The control unit 10 can control the emitter follower through which the input voltage passes by controlling the first-stage analog switch to the fourth-stage analog switch in the switch unit 30. For example, when the input voltage passes through the first-stage emitter follower, the second-stage emitter follower, the third-stage emitter follower, and the fourth-stage emitter follower in sequence, the upper and lower limit values of the input voltage remain unchanged. When the input voltage passes through the first-stage emitter follower and the second-stage emitter follower in sequence, the upper and lower limit values of the input voltage increase twice by the same amplitude.

[0045] As a further embodiment, the first-stage emitter follower is connected to the first common terminal COM1 of the first-stage analog switch. The normally open terminal of the first-stage analog switch is connected to the second-stage emitter follower. The second-stage emitter follower is connected to the first normally closed terminal NC1 of the second-stage analog switch. The first normally open terminal NO1 of the second-stage analog switch is connected to the third-stage emitter follower. The third-stage emitter follower is connected to the second normally closed terminal NC2 of the third-stage analog switch. The second common terminal COM2 of the third-stage analog switch is connected to the fourth-stage emitter follower. The fourth-stage emitter follower is connected to the second normally open terminal NO2 of the fourth-stage analog switch. The common terminal of the fourth-stage analog switch is used to output the voltage signal. The first controlled terminals of the first-stage analog switch and the second-stage analog switch, and the second controlled terminals of the third-stage analog switch and the fourth-stage analog switch are all connected to the control unit 10. The first normally closed terminal NC1 of the first-stage analog switch, the first common terminal COM1 of the second-stage analog switch, the second normally open terminal NO2 of the third-stage analog switch, and the second normally closed terminal NC2 of the fourth-stage analog switch are connected in parallel.

[0046] Among them, as Figure 5 shown, the circuit structures of the first-stage emitter follower and the second-stage emitter follower are the same as the circuit structure of the first emitter follower 21 mentioned above. The circuit structures of the third-stage emitter follower and the fourth-stage emitter follower are the same as the circuit structure of the second emitter follower 22 mentioned above. The fifth resistor R5 serves as a current-limiting resistor to protect the entire emission circuit. It should be noted that in the default state of all analog switches, the common terminal is connected to the normally closed terminal. That is, in the default state, the input voltage signal passes through the first-stage emitter follower and the fourth-stage analog switch in sequence. When it is necessary to increase the upper and lower limit values of the input voltage twice, the control unit 10 can be used to control the first common terminal COM1 of the first-stage analog switch to be connected to the first normally open terminal NO1 of the first-stage analog switch. Then the input voltage passes through the first-stage emitter follower, the second-stage emitter follower, and the fourth-stage analog switch in sequence.

[0047] See Figure 6, the present invention also discloses a control method, which is applied to the transmitting circuit described in any one of the above embodiments, and the control method includes steps S110 to S130.

[0048] S110, if an adjustment instruction for adjusting the input voltage is received, confirm the type of the adjustment instruction, where the adjustment instruction includes a first instruction and a second instruction, the first instruction is used to increase the upper and lower limits of the input voltage, and the second instruction is used to decrease the upper and lower limits of the input voltage.

[0049] For the input voltage, generally, its upper and lower limits are increased or decreased. Therefore, the adjustment instruction usually includes a first instruction and a second instruction. For the transmitting circuit, since its default state is to increase the upper and lower limits of the input voltage, when it is necessary to keep the input voltage unchanged, it can be achieved by the second instruction, that is, decreasing the upper and lower limits of the input voltage.

[0050] S120, if the type of the adjustment instruction is the first instruction, control the first analog switch to be connected to the second analog switch.

[0051] In the transmitting circuit, the first emitter follower is defaultly connected to the first analog switch. The connection state of the first analog switch can be controlled to determine whether the first analog switch is connected to the second emitter follower or the second analog switch. If there are multiple first emitter followers and multiple second emitter followers, the first instruction can be further divided into increasing the upper and lower limits of the input voltage once, twice, or three times, and so on. Correspondingly, it can be controlled whether the first analog switch is connected to the second first emitter follower or the last second analog switch. For example, if it is necessary to increase the upper and lower limits of the input voltage twice, the first first analog switch, that is, the first-level analog switch, can be controlled to be connected to the second first emitter follower, that is, the second-level emitter follower, and the second first analog switch, that is, the second-level analog switch, can be controlled to be connected to the last analog switch, that is, the fourth-level analog switch. Then the input voltage passes through the first-level emitter follower and the second-level emitter follower in sequence and is output from the fourth-level analog switch.

[0052] S130, if the type of the adjustment instruction is the second instruction, control the first analog switch to be connected to the second emitter follower, and control the second analog switch to be connected to the second emitter follower.

[0053] Among them, if the second instruction is to lower the upper and lower limits of the input voltage, the first analog switch can be controlled to connect to the second emitter follower, and the second analog switch can be controlled to connect to the second emitter follower, so that the input voltage passes through the first emitter follower and the second emitter follower in sequence, and flows out through the second analog switch. If there are multiple first emitter followers and multiple second emitter followers, the connection states of the corresponding analog switches can be controlled according to the circuit structure to achieve the reduction of the upper and lower limits of the input voltage.

[0054] The first emitter follower is used to increase the upper and lower limits of the input voltage, and the second emitter follower is used to lower the upper and lower limits of the input voltage. If there are multiple first emitter followers and multiple second emitter followers in the transmitting circuit, there are correspondingly multiple first analog switches and multiple second analog switches. By controlling the connection states of the first analog switch and the second analog switch, the number of the first emitter follower and the second emitter follower through which the input voltage passes is controlled to adjust the upper and lower limits of the input voltage. For example, if it is necessary to lower the upper and lower limits of the input voltage once, it can pass through the first emitter follower once and the second emitter follower once. If it is necessary to increase the upper limit of the input voltage twice, it can pass through the first emitter follower twice, and so on for other cases, which will not be elaborated here.

[0055] The present invention also discloses an infrared touch screen, which includes the transmitting circuit described in any one of the above embodiments.

[0056] By providing at least one first emitter follower and at least one second emitter follower, the present invention increases the upper and lower limits of the input voltage through the first emitter follower, lowers the upper limit of the input voltage through the second emitter follower, and adjusts the upper and lower limits of the input voltage by controlling the number of the first emitter follower and the second emitter follower through which the input voltage passes by the first analog switch and the second analog switch, so as to meet the requirements of different emission tubes for the driving voltage, ensure the normal use of the touch screen, and improve the user experience.

[0057] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of various equivalent modifications or substitutions within the technical scope disclosed by the present invention, and these modifications or substitutions should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A transmitting circuit, applied to an infrared touch screen, characterized in that It includes a control unit, an adjustment unit, and a switching unit; The adjustment unit includes at least one first emitter follower and at least one second emitter follower. The input end of the first emitter follower is connected to the control unit for receiving an input voltage. Wherein, the first emitter follower is used to increase the upper and lower limits of the input voltage, the second emitter follower is used to decrease the upper and lower limits of the input voltage, and the number of the first emitter followers is the same as that of the second emitter followers; The switching unit includes at least one first analog switch and at least one second analog switch. The first analog switch is respectively connected to the first emitter follower, the second emitter follower, and the second analog switch. The second analog switch is connected to the second emitter follower. The first analog switch and the second analog switch are also connected to the control unit; Wherein, different first emitter followers are connected through the first analog switch, and different second emitter followers are connected through the second analog switch. The connection states of the first analog switch and the second analog switch can be controlled by the control unit to control the number of first emitter followers connected to the first analog switch module and the number of second emitter followers connected to the second analog switch module to adjust the upper and lower limits of the input voltage.

2. The transmitting circuit according to claim 1, wherein, The first analog switch includes a first common terminal, a first normally open terminal, a first normally closed terminal, and a first controlled terminal. The second analog switch includes a second common terminal, a second normally open terminal, a second normally closed terminal, and a second controlled terminal; The first common terminal is connected to the first emitter follower. The first normally open terminal is connected to the second emitter follower. The first normally closed terminal is connected to the second normally closed terminal. The second normally open terminal is connected to the second emitter follower. The second common terminal is used for outputting a voltage signal. The first controlled terminal and the second controlled terminal are both connected to the control unit.

3. The transmitting circuit according to claim 2, wherein The first emitter follower includes a first triode; The base of the first triode is connected to the control unit, its emitter is connected to the first common terminal, and its collector is grounded.

4. The transmitting circuit according to claim 3, wherein The first emitter follower also includes a first resistor and a second resistor. One end of the first resistor is connected to the control unit, the other end of the first resistor is connected to one end of the second resistor, and the other end of the second resistor is connected to the first common terminal.

5. The transmitting circuit according to claim 3, characterized in that, The second emitter follower includes a second triode; The base of the second triode is connected to the first normally open terminal, its emitter is connected to the second normally closed terminal, and its collector is grounded.

6. The transmitting circuit according to claim 5, wherein The second emitter follower also includes a third resistor and a fourth resistor. One end of the third resistor is connected to the first normally open terminal, the other end of the third resistor and one end of the fourth resistor are both grounded, and the other end of the fourth resistor is connected to the second normally closed terminal.

7. The transmitting circuit according to claim 2, wherein The adjustment unit includes two of the first emitter followers and two of the second emitter followers, and the switching unit includes two of the first analog switches and two of the second analog switches. Among them, the two first emitter followers are a first-level emitter follower and a second-level emitter follower respectively, the two second emitter followers are a third-level emitter follower and a fourth-level emitter follower respectively, the two first analog switches are a first-level analog switch and a second-level analog switch respectively, and the two second analog switches are a third-level analog switch and a fourth-level analog switch respectively.

8. The transmitting circuit according to claim 7, wherein The first-level emitter follower is connected to the first common terminal of the first-level analog switch, the normally open terminal of the first-level analog switch is connected to the second-level emitter follower, the second-level emitter follower is connected to the first normally closed terminal of the second-level analog switch, the first normally open terminal of the second-level analog switch is connected to the third-level emitter follower, the third-level emitter follower is connected to the second normally closed terminal of the third-level analog switch, the second common terminal of the third-level analog switch is connected to the fourth-level emitter follower, the fourth-level emitter follower is connected to the second normally open terminal of the fourth-level analog switch, and the common terminal of the fourth-level analog switch is used to output the voltage signal; The first controlled terminals of the first-level analog switch and the second-level analog switch and the second controlled terminals of the third-level analog switch and the fourth-level analog switch are all connected to the control unit, and the first normally closed terminal of the first-level analog switch, the first common terminal of the second-level analog switch, the second normally open terminal of the third-level analog switch, and the second normally closed terminal of the fourth-level analog switch are connected in parallel.

9. A control method, characterized in that, Applied to the transmitting circuit according to any one of claims 1 to 8, including: If a adjustment instruction for adjusting the input voltage is received, confirm the type of the adjustment instruction. Among them, the adjustment instruction includes a first instruction and a second instruction. The first instruction is used to increase the upper and lower limits of the input voltage, and the second instruction is used to decrease the upper and lower limits of the input voltage; If the type of the adjustment instruction is the first instruction, control the first analog switch to be connected to the second analog switch; If the type of the adjustment instruction is the second instruction, control the first analog switch to be connected to the second emitter follower, and control the second analog switch to be connected to the second emitter follower.

10. An infrared touch screen, characterized in that, Includes the transmitting circuit according to any one of claims 1 to 8.

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