Audio signal switch soft start circuit

Abstract

The invention discloses a soft start circuit for an audio signal switch. The soft start circuit is composed of a signal input buffer module, a soft start control module, a signal voltage division module and a bidirectional amplitude limiting module. The signal input buffer module ensures that an audio input signal is pure, the soft start control module can enable the signal to be rapidly closed and slowly opened during switching of a switch, the signal voltage dividing module adjusts the grid voltage according to an instruction of the soft start control module through a field effect transistor and a voltage dividing resistor so as to control the voltage dividing proportion, and the bidirectional amplitude limiting module ensures that the amplitude of the output signal is safe. The soft start control module comprises a first switch unit, an RC delay circuit and a triode control unit. When the switch is switched off, the RC time-delay circuit slowly charges the capacitor, so that the internal resistance of the field-effect tube is gradually increased, signal soft start is realized, and audio switching noise is avoided; when the switch is closed, the capacitor discharges quickly, and quick signal break and no reverse impact are realized. Not only is audio smooth transition ensured, but also a post-stage circuit is protected, and the stability and the reliability of an audio system are improved.

Description

Technical Field

[0001] This application relates to the technical field of soft start, and more specifically, to an audio signal switch soft start circuit. Background Art

[0002] In today's electronic devices and audio systems, the stable transmission and processing of audio signals are crucial. In many application scenarios involving audio signal switches, the mechanical signal switches in the prior art lack a smooth transition from off to on. As Figure 1 shown, when a complete signal passes through the switch, the signal peak will directly impact the subsequent circuit.

[0003] For example, in the professional audio field, such as recording studios, sound systems for large-scale performances, etc., the quality of audio signals directly affects the final artistic presentation effect. During the recording process, when switching different audio input sources, such as switching from a microphone to an instrument input, using a traditional mechanical signal switch will cause an impact sound, and the impact signal generated instantaneously by the switch will be recorded and become noise in the audio file, seriously affecting the purity of the audio. Moreover, in scenarios that require frequent switching operations, frequent impact signals may also accelerate the aging of subsequent audio devices such as speakers, increasing the equipment maintenance cost and replacement frequency.

[0004] In summary, the existing audio signal switch methods lack a smooth transition during switch switching, and the generated impact signals will bring serious negative impacts in the application scenarios. Therefore, there is an urgent need for a new circuit to solve these problems, and the audio signal switch soft start circuit of this application emerges as the times require. Summary of the Invention

[0005] This application provides an audio signal switch soft start circuit, which realizes the rapid closing and slow opening of the signal during switch switching, solves the defect that the existing mechanical switch has no smooth transition and the impact signal affects the subsequent circuit, effectively protects the subsequent circuit and improves the signal transmission quality.

[0006] An audio signal switch soft start circuit includes:

[0007] A signal input buffer module, configured to receive an audio input signal and perform buffer isolation;

[0008] A soft start control module, connected to the signal input buffer module, configured to realize the rapid closing and slow opening of the signal during switch switching;

[0009] A signal voltage division module, including a field effect transistor and a voltage division resistor, wherein the gate of the field effect transistor is controlled by the soft start control module, and the voltage division ratio is controlled by adjusting the gate voltage;

[0010] A bidirectional amplitude limiting module, connected to the signal voltage dividing module, for limiting the amplitude of the output signal;

[0011] Among them, the soft start control module includes:

[0012] A first switch unit, for triggering the switching of the switch state;

[0013] An RC delay circuit, composed of a first resistor, a second resistor and a first capacitor connected in series. One end of the first resistor is connected to the power supply, and the other end is connected to the positive electrode of the first capacitor through the second resistor. The negative electrode of the first capacitor is grounded;

[0014] A triode control unit, controlling the conduction state of the field effect transistor according to the voltage change of the RC delay circuit;

[0015] When the first switch unit is disconnected, the RC delay circuit slowly charges the first capacitor through the first resistor and the second resistor, so that the internal resistance of the field effect transistor gradually increases, realizing signal soft start;

[0016] When the first switch unit is closed, the first capacitor discharges quickly through the ground, pulling the gate voltage of the field effect transistor down to the ground level, realizing signal fast shutdown.

[0017] Optionally, the signal input buffer module includes an operational amplifier, and the operational amplifier is configured as a voltage follower. The input signal is output to the signal voltage dividing module after being isolated by the operational amplifier.

[0018] Optionally, the triode control unit includes a PNP type triode and an NPN type triode;

[0019] The emitter of the PNP type triode is connected to the power supply, the collector is connected to the gate of the field effect transistor through a third resistor, and the base is respectively connected to the collector of the NPN type triode through a fourth resistor and grounded through a fifth resistor;

[0020] The base of the NPN type triode is grounded through a sixth resistor, a first diode and the first switch unit;

[0021] When the first switch unit is closed, the PNP type triode conducts, pulling the gate voltage of the field effect transistor down to the ground level;

[0022] When the first switch unit is disconnected, the NPN type triode conducts as the voltage of the RC delay circuit rises, and the PNP type triode gradually turns off.

[0023] Optionally, the bidirectional amplitude limiting module includes two diode groups connected in antiparallel. The diode groups are connected in series to the signal output terminal, and the amplitude limiting voltage is the sum of the forward conduction voltages of the two diode groups.

[0024] Optionally, the field effect transistor is an N-channel MOS transistor with a conduction internal resistance less than 10 mΩ and a cut-off internal resistance greater than 1 MΩ. The resistance value of the voltage dividing resistor is 1 kΩ to 10 kΩ.

[0025] Optionally, in the RC delay circuit, the total resistance value of the first resistor and the second resistor is 10 kΩ to 100 kΩ, and the capacitance value of the first capacitor is 1 μF to 10 μF.

[0026] Optionally, the anode of the first diode is connected to the positive electrode of the first capacitor, and the cathode of the first diode is grounded through the first switch unit, which is used to quickly release the charge of the first capacitor when the first switch unit is closed.

[0027] Optionally, it further includes a second diode. The anode of the second diode is connected to the base of the PNP transistor, and the cathode is grounded through the first switch unit, which is used to accelerate the drop of the gate voltage of the field effect transistor when the first switch unit is closed.

[0028] Optionally, it further includes a seventh resistor. The output terminal of the signal voltage dividing module is connected to the bidirectional amplitude limiting module through the seventh resistor. The resistance value of the seventh resistor is 100 Ω to 1 kΩ, which is used to adjust the attenuation ratio of the output signal.

[0029] Optionally, the soft start control module further includes a transient suppression circuit. The transient suppression circuit is composed of a second capacitor and an eighth resistor connected in parallel, and is connected to the output terminal of the signal input buffer module, which is used to filter out high-frequency noise.

[0030] As can be seen from the above technical solutions, an audio signal switch soft start circuit provided by an embodiment of the present application is composed of a signal input buffer module, a soft start control module, a signal voltage dividing module, and a bidirectional amplitude limiting module. The signal input buffer module receives the audio input signal and performs buffering isolation to ensure the pure input of the signal; the soft start control module is responsible for quickly closing and slowly opening the signal during the switch transition; the signal voltage dividing module adjusts the gate voltage according to the control of the soft start control module through the field effect transistor and the voltage dividing resistor, and then controls the voltage dividing ratio; the bidirectional amplitude limiting module limits the amplitude of the output signal to ensure that the output signal is within a safe range.

[0031] Among them, the specific design of the soft start control module effectively solves the defects of the prior art. The soft start control module includes a first switch unit, an RC delay circuit composed of a first resistor, a second resistor and a capacitor, and a triode control unit. When the first switch unit is disconnected, the RC delay circuit slowly charges the capacitor through the first resistor and the second resistor, causing the internal resistance of the field effect transistor to gradually increase, realizing a slow rise of the signal from off to on, that is, the soft start process, ensuring a smooth transition of the audio signal and avoiding the appearance of noise during the switching process. When the first switch unit is closed, the first capacitor discharges quickly through the ground, and the gate voltage of the field effect transistor is pulled down to the ground level, realizing a quick turn-off of the signal. This enables timely response when it is necessary to quickly cut off the audio signal, and no reverse impact signal will be generated, further protecting the subsequent circuit and improving the stability and reliability of the entire audio system. Description of the Drawings

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0033] Figure 1 It is a schematic diagram of signal fluctuation through a mechanical signal switch disclosed in the background art of the present application;

[0034] Figure 2 It is a schematic diagram of a soft start circuit for an audio signal switch disclosed in an embodiment of the present application;

[0035] Figure 3 It is another schematic diagram of a soft start circuit for an audio signal switch disclosed in an embodiment of the present application. Detailed Embodiments

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0037] Next, the solution of the present application will be introduced. The present application proposes the following technical solutions. For details, please refer to the following text.

[0038] Figure 2 It is a schematic diagram of a soft start circuit for an audio signal switch disclosed in an embodiment of the present application.

[0039] Figure 3Another schematic diagram of a soft start circuit for an audio signal switch disclosed in an embodiment of the present application.

[0040] As Figure 2 shown, the circuit may include:

[0041] A signal input buffer module 1 for receiving an audio input signal and performing buffer isolation;

[0042] A soft start control module 2 connected to the signal input buffer module for achieving fast signal shutdown and slow startup during switch switching;

[0043] A signal voltage division module 3 including a field effect transistor and a voltage division resistor, the gate of the field effect transistor being controlled by the soft start control module to control the voltage division ratio by adjusting the gate voltage;

[0044] A bidirectional amplitude limiting module 4 connected to the signal voltage division module for limiting the amplitude of the output signal;

[0045] Wherein, the soft start control module 2 includes:

[0046] A first switch unit for triggering a switch state change;

[0047] An RC delay circuit composed of a series-connected first resistor, a second resistor, and a first capacitor, one end of the first resistor being connected to a power supply, the other end being connected to the positive electrode of the first capacitor through the second resistor, and the negative electrode of the first capacitor being grounded;

[0048] A triode control unit for controlling the conduction state of the field effect transistor according to the voltage change of the RC delay circuit;

[0049] When the first switch unit is disconnected, the RC delay circuit slowly charges the first capacitor through the first resistor and the second resistor, causing the internal resistance of the field effect transistor to gradually increase, realizing signal soft start;

[0050] When the first switch unit is closed, the first capacitor quickly discharges through the ground, pulling the gate voltage of the field effect transistor down to the ground level, realizing signal fast shutdown.

[0051] Specifically, the soft start circuit for the audio signal switch is composed of four key modules: a signal input buffer module, a soft start control module, a signal voltage division module, and a bidirectional amplitude limiting module. The four modules cooperate to enable the audio signal to achieve a smooth transition during switch switching, avoid the signal impact problem generated by the traditional switch method, protect the subsequent circuit, and improve the audio signal transmission quality.

[0052] The function of the signal input buffer module is to receive the audio input signal and perform buffering isolation. It generally uses circuits such as operational amplifiers, and utilizes the characteristics of high input impedance and low output impedance to enhance the driving ability of the signal, reduce the attenuation and distortion of the signal during transmission, effectively isolate the input audio signal from the subsequent circuit, avoid mutual interference, and ensure that the input signal enters the subsequent circuit stably and purely.

[0053] The soft start control module is the core to achieve smooth signal switching. Among them, the first switch unit is used to receive the switch operation signal of the user and trigger the switching of the switch state. Among them, the RC delay circuit is composed of a series-connected resistor and capacitor. When the first switch unit is disconnected, the power supply slowly charges the capacitor through the resistor; when the first switch unit is closed, the capacitor quickly discharges. The triode control unit controls the conduction state of the field effect transistor according to the change of the voltage across the capacitor in the RC delay circuit. By changing the working state of the triode, the internal resistance and other parameters of the field effect transistor are affected, and finally the signal is controlled to achieve the effect of slow signal turn-on and fast signal turn-off.

[0054] As Figure 3 shown, the first switch unit S1 receives the user switch signal and triggers the circuit state switching. The RC delay circuit is composed of the series-connected first resistor R27, second resistor R26 and first capacitor C16. One end of R27 is connected to the power supply VCC, and the other end is connected to the positive electrode of C16 through R26, and the negative electrode of C16 is grounded. When S1 is disconnected, VCC slowly charges C16 through resistors R27 and R26; when S1 is closed, C16 quickly discharges.

[0055] The signal voltage division module includes a field effect transistor and a voltage dividing resistor. The gate of the field effect transistor is controlled by the soft start control module. By adjusting the voltage of the gate of the field effect transistor, the internal resistance of the field effect transistor is changed, so as to achieve the control of the voltage division ratio, and thus adjust the voltage magnitude of the audio signal to make the signal intensity meet the requirements.

[0056] The function of the bidirectional amplitude limiting module is to limit the amplitude of the output signal. It is usually composed of components such as diodes. Using the unidirectional conductivity of the diodes, when the signal voltage exceeds a certain value, the diodes conduct, limiting the signal amplitude within a specified range, preventing the amplitude of the output audio signal from being too large and exceeding the range that the subsequent circuit can withstand, and avoiding damage to the components of the subsequent circuit.

[0057] In the audio signal switch soft start circuit, the newly added second diode and seventh resistor further optimize the circuit performance.

[0058] The anode of the second diode is connected to the base of the PNP type triode, and the cathode is grounded through the first switch unit, and is used to accelerate the voltage drop of the gate of the field effect transistor when the first switch unit is closed.

[0059] The output terminal of the signal voltage division module is connected to the bidirectional amplitude limiting module through the seventh resistor, and the resistance value of the seventh resistor is 100Ω to 1kΩ, which is used to adjust the attenuation ratio of the output signal.

[0060] Specifically, the anode of the second diode is connected to the base of the PNP transistor, and the cathode is grounded through the first switching unit. When the first switching unit is closed, the process of the original capacitor discharging rapidly to reduce the gate voltage of the field effect transistor is accelerated. This is because the second diode provides an additional fast path for the capacitor to discharge at this time, and the current can pass through more quickly, prompting the gate voltage of the field effect transistor to drop faster, thereby achieving a faster signal turn-off and enhancing the response speed of the circuit when the signal is turned off.

[0061] The output terminal of the signal voltage division module is connected to the bidirectional amplitude limiting module via the seventh resistor, and its resistance value ranges from 100Ω to 1kΩ. This resistor can adjust the attenuation ratio of the output signal. When the audio signal is output from the signal voltage division module and passes through the seventh resistor to the bidirectional amplitude limiting module, the resistance value determines the degree of signal attenuation. By reasonably setting the resistance value of this resistor, the intensity of the output signal can be accurately adjusted to better adapt to the working requirements of the bidirectional amplitude limiting module and the signal intensity requirements of the subsequent circuit, ensuring the stability and accuracy of the entire audio signal transmission process.

[0062] In some embodiments of the present application, each component in the audio signal switch soft-start circuit is introduced separately:

[0063] Signal input buffer module 1:

[0064] The signal input buffer module includes an operational amplifier, and the operational amplifier is configured as a voltage follower. The input signal is output to the signal voltage division module after being isolated by the operational amplifier.

[0065] Specifically, the signal input buffer module takes the operational amplifier as the core and configures it in the voltage follower mode. In this configuration, when the input signal enters the operational amplifier, it can utilize its high input impedance and low output impedance characteristics to effectively isolate the input signal from the subsequent circuit, reduce mutual interference, ensure the stable transmission of the signal to the signal voltage division module, and minimize signal attenuation and distortion during the transmission process.

[0066] Such as Figure 3As shown in the figure, the signal input buffer module 1 includes an operational amplifier U2B. The audio input signal is input from the LINE1_IN terminal of the interface P2 and is connected to the non-inverting input terminal of U2B through the resistor R22. U2B is configured as a voltage follower. Utilizing its high input impedance and low output impedance characteristics, it buffers and isolates the input signal, enhances the signal driving ability, reduces the attenuation and distortion of the signal during transmission, and the output signal is transmitted to the subsequent module through R7.

[0067] Bidirectional limiter module 4:

[0068] The bidirectional limiter module includes two diode groups connected in reverse parallel. The diode groups are connected in series to the signal output terminal, and the limiting voltage is the sum of the forward conduction voltages of the two diode groups.

[0069] Specifically, the bidirectional limiter module is composed of two diode groups connected in reverse parallel, namely Figure 3 D9 and D11, D10 and D12 in, and the diode groups are connected in series to the signal output terminal LINE1_OUT. The diode has unidirectional conductivity. When the signal voltage is higher than or lower than a certain threshold, the corresponding diode group conducts. The limiting voltage is the sum of the forward conduction voltages of the two diode groups, thereby limiting the amplitude of the output signal and preventing it from exceeding the tolerance range of the subsequent circuit, protecting the components of the subsequent circuit from high voltage impact.

[0070] Signal voltage division module 3:

[0071] The field effect transistor is an N-channel MOS transistor, its on-resistance is less than 10 mΩ, and its off-resistance is greater than 1 MΩ. The resistance value of the voltage division resistor is 1 kΩ to 10 kΩ.

[0072] Specifically, the field effect transistor of the signal voltage division module uses an N-channel MOS transistor, which has obvious performance parameter advantages. The on-resistance is less than 10 mΩ, which means that when in the on state, the signal loss is extremely small when passing through; the off-resistance is greater than 1 MΩ, which can effectively block the signal. The resistance value of the voltage division resistor is set in the range of 1 kΩ to 10 kΩ. By working together with the field effect transistor, according to the adjustment of the gate voltage of the field effect transistor by the soft start control module, the internal resistance of the field effect transistor is changed, and then the voltage division ratio is accurately controlled to adjust the audio signal voltage to meet the requirements of the subsequent circuit for the signal strength.

[0073] In some embodiments of the present application, in combination with Figure 3 the components in the soft start control module 2 are introduced:

[0074] Triode control unit:

[0075] The triode control unit includes a PNP-type triode Q3 and an NPN-type triode Q2;

[0076] The emitter of the PNP transistor Q3 is connected to the power supply VCC, the collector is connected to the gate of the field-effect transistor Q1 through the third resistor R23, and the base is respectively connected to the collector of the NPN transistor Q2 through the fourth resistor R32 and grounded through the fifth resistor R35;

[0077] The base of the NPN transistor Q2 is grounded through the sixth resistor R25, the first diode D1 and the first switch unit S1;

[0078] When the first switch unit S1 is closed, the PNP transistor Q3 conducts, pulling the gate voltage of the field-effect transistor Q1 to the ground level;

[0079] When the first switch unit S1 is opened, the NPN transistor Q2 conducts as the voltage of the RC delay circuit rises, and the PNP transistor Q3 gradually turns off.

[0080] Wherein, the anode of the first diode is connected to the positive electrode of the first capacitor, and the cathode of the first diode is grounded through the first switch unit, and is used to quickly discharge the charge of the first capacitor when the first switch unit is closed.

[0081] Specifically, the triode control unit is composed of a PNP transistor and an NPN transistor working together. The emitter of the PNP transistor is connected to the power supply, providing the necessary energy source for its operation. The collector is connected to the gate of the field-effect transistor through the third resistor, which enables the PNP transistor to regulate the gate voltage of the field-effect transistor.

[0082] The collector of the NPN transistor is connected to the base of the PNP transistor through the fourth resistor, and this connection mode constructs a signal transmission channel between the two transistors. The base of the NPN transistor is grounded through the sixth resistor, the first diode and the first switch unit, and this circuit structure determines that the conduction state of the NPN transistor is jointly affected by the first switch unit and the RC delay circuit.

[0083] When the first switch unit is closed, the current path changes, causing the PNP transistor to conduct. At this time, the PNP transistor pulls the gate voltage of the field-effect transistor to the ground level, achieving a rapid shutdown of the signal. This is because the reduction of the gate voltage of the field-effect transistor causes its internal resistance to rapidly decrease, thereby blocking the signal transmission.

[0084] When the first switch unit is turned off, the RC delay circuit starts to work. As the capacitor in the RC delay circuit charges, the voltage gradually rises. When the voltage rises to a certain level, the NPN transistor conducts. The conduction of the NPN transistor causes a change in the base potential of the PNP transistor, which in turn leads to the gradual turn-off of the PNP transistor. During this process, the gate voltage of the field effect transistor gradually increases and the internal resistance gradually increases, achieving a soft start of the signal.

[0085] Among them, the anode of the first diode is connected to the positive electrode of the first capacitor, and the cathode is grounded through the first switch unit. When the first switch unit is closed, the first diode provides a rapid discharge path for the first capacitor, enabling the charge of the first capacitor to be quickly released, thereby accelerating the process of the gate voltage of the field effect transistor dropping and further increasing the speed of signal turn-off.

[0086] RC delay circuit:

[0087] In the RC delay circuit, the total resistance value of the first resistor and the second resistor is 10 kΩ to 100 kΩ, and the capacitance value of the first capacitor is 1 μF to 10 μF.

[0088] Specifically, in the RC delay circuit, the total resistance value of the first resistor and the second resistor is set in the range of 10 kΩ to 100 kΩ, and the capacitance value of the first capacitor is between 1 μF and 10 μF. This combination of resistor and capacitor parameters determines the charging speed of the capacitor, which in turn affects the soft start time of the signal. When the first switch unit is turned off, the power supply charges the first capacitor through the first resistor and the second resistor. Due to the current-limiting effect of the resistor, the charging process of the capacitor is relatively slow, thus realizing the slow rise of the signal from nothing, that is, the soft start process. The specific values of the resistor and capacitor can be adjusted according to actual needs to meet different soft start time requirements.

[0089] In addition, the soft start control module may further include a transient suppression circuit, which is composed of a second capacitor and an eighth resistor in parallel, connected to the output end of the signal input buffer module for filtering high-frequency noise.

[0090] Specifically, the soft start control module may also be equipped with a transient suppression circuit composed of a second capacitor and an eighth resistor in parallel. This circuit is connected to the output end of the signal input buffer module, and its main function is to filter high-frequency noise. During the transmission of audio signals, it is inevitable to mix in some high-frequency noises, which may interfere with the normal operation of the circuit. The parallel combination of the second capacitor and the eighth resistor forms a low-pass filter, which can effectively attenuate high-frequency signals and only allow low-frequency audio signals to pass through, thereby improving the purity of the signal and ensuring the quality of the audio signal.

[0091] Finally, it should also be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, circuit, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, circuit, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, circuit, article or device comprising the element.

[0092] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same and similar parts among the various embodiments, reference can be made to each other.

[0093] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An audio signal switch soft start circuit, characterized in that, Comprising: A signal input buffer module, configured to receive an audio input signal and perform buffering isolation; A soft start control module, connected to the signal input buffer module, configured to achieve fast shutdown and slow startup of the signal during switch switching; A signal voltage division module, including a field effect transistor and a voltage division resistor, the gate of the field effect transistor being controlled by the soft start control module, and the voltage division ratio being controlled by adjusting the gate voltage; A bidirectional amplitude limiting module, connected to the signal voltage division module, configured to limit the amplitude of the output signal; Wherein, the soft start control module includes: A first switch unit, configured to trigger a switch state change; An RC delay circuit, composed of a first resistor, a second resistor and a first capacitor connected in series, one end of the first resistor being connected to a power supply, and the other end being connected to the positive electrode of the first capacitor through the second resistor, and the negative electrode of the first capacitor being grounded; A triode control unit, configured to control the conduction state of the field effect transistor according to the voltage change of the RC delay circuit; When the first switch unit is disconnected, the RC delay circuit slowly charges the first capacitor through the first resistor and the second resistor, so that the internal resistance of the field effect transistor gradually increases, realizing signal soft start; When the first switch unit is closed, the first capacitor discharges quickly through the ground, so that the gate voltage of the field effect transistor is pulled down to the ground level, realizing signal fast shutdown.

2. The circuit according to claim 1, wherein The signal input buffer module includes an operational amplifier, and the operational amplifier is configured as a voltage follower, and the input signal is isolated by the operational amplifier and then output to the signal voltage division module.

3. The circuit according to claim 1, characterized in that, The triode control unit includes a PNP type triode and an NPN type triode; The emitter of the PNP type triode is connected to a power supply, the collector is connected to the gate of the field effect transistor through a third resistor, and the base is respectively connected to the collector of the NPN type triode through a fourth resistor and grounded through a fifth resistor; The base of the NPN type triode is grounded through a sixth resistor, a first diode and the first switch unit; When the first switch unit is closed, the PNP type triode conducts, pulling down the gate voltage of the field effect transistor to the ground level; When the first switch unit is disconnected, the NPN type triode conducts as the voltage of the RC delay circuit rises, and the PNP type triode gradually turns off.

4. The circuit according to claim 1, characterized in that, The bidirectional amplitude limiting module includes two diode groups connected in reverse parallel, and the diode groups are connected in series to the signal output end, and the amplitude limiting voltage is the sum of the forward conduction voltages of the two diode groups.

5. The circuit according to claim 1, wherein The field effect transistor is an N-channel MOS transistor, its on-resistance is less than 10 mΩ, its off-resistance is greater than 1 MΩ, and the resistance value of the voltage division resistor is 1 kΩ to 10 kΩ.

6. The circuit according to claim 1, wherein In the RC delay circuit, the total resistance value of the first resistor and the second resistor is 10 kΩ to 100 kΩ, and the capacitance value of the first capacitor is 1 μF to 10 μF.

7. The circuit according to claim 3, wherein The anode of the first diode is connected to the positive electrode of the first capacitor, and the cathode of the first diode is grounded through the first switch unit, and is used to quickly release the charge of the first capacitor when the first switch unit is closed.

8. The circuit according to claim 3, wherein It further includes a second diode, the anode of the second diode is connected to the base of the PNP transistor, and the cathode is grounded through the first switching unit, which is used to accelerate the drop of the gate voltage of the field effect transistor when the first switching unit is closed.

9. The circuit according to claim 1, characterized in that, It further includes a seventh resistor. The output end of the signal voltage dividing module is connected to the bidirectional limiting module through the seventh resistor. The resistance value of the seventh resistor is 100Ω~1kΩ, which is used to adjust the attenuation ratio of the output signal.

10. The circuit according to claim 1, characterized in that, The soft start control module further includes a transient suppression circuit, which is composed of a second capacitor and an eighth resistor in parallel, and is connected to the output end of the signal input buffer module for filtering high-frequency noise.

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