Liquid crystal screen stereo input peak automatic limiting control circuit and method

Abstract

The application relates to a liquid crystal screen stereo input peak automatic limiting control circuit and method, which comprises the following: an audio input unit which is provided with an insertion detection circuit; a main audio processor which integrates an EQ adjusting function; a peak detection and comparison unit which is used for converting an audio signal into a direct current voltage and comparing the direct current voltage with a threshold value to output an over-blast flag signal; a volume controller which is used for two-stage volume adjustment; a power amplifier unit; a micro control unit which is connected with the insertion detection circuit at a first input end, connected with the peak detection and comparison unit at a second input end, connected with the main audio processor at a first output end, connected with the volume controller at a second output end, and connected with the power amplifier unit MUTE pin at a third output end; the micro control unit sends a MUTE signal when detecting audio insertion, adjusts the volume of the main audio processor when detecting over-blast, and cancels the MUTE signal after the over-blast disappears; the application realizes audio insertion automatic muting and over-blast automatic limiting, and prevents blast distortion.

Description

Technical Field

[0001] This invention relates to the field of audio signal processing technology, and more specifically, to an automatic peak limiting control circuit and method for stereo input of an LCD screen. Background Technology

[0002] AUX (Auxiliary) audio input interface, also known as "auxiliary input interface" or "audio input interface," is a basic and universal audio interface in electronic devices, primarily used for transmitting analog audio signals. With the popularization of consumer electronics, this interface has evolved from its initial role as a pre-connector to a standard feature in various audio equipment, widely used in LCD monitors, car audio systems, home speakers, and professional audio equipment. Its core function is to directly transmit audio signals from external audio source devices such as mobile phones, MP3 players, computers, and tablets to LCD monitors, speakers, amplifiers, or car audio systems for playback via physical cables.

[0003] However, existing AUX audio input speaker devices have the following technical problems in practical applications: (1) Input audio overload causes popping and distortion; When the output volume of an external audio source device (such as a mobile phone or computer) is set to a certain percentage, the amplitude of its output audio signal often exceeds the rated input level of the LCD screen or audio equipment. This excessively large audio signal, after being directly amplified by the power amplifier, can cause noticeable popping, distortion, or even noise from the speakers, severely affecting the listening experience.

[0004] (2) Lack of input detection and automatic protection mechanisms; The existing equipment lacks audio insertion detection and cannot identify whether an external audio source is connected. Furthermore, it lacks volume threshold detection and automatic adjustment mechanisms; when the input audio signal is too loud, it cannot automatically reduce the volume to prevent popping sounds, requiring users to manually adjust the output volume of the external audio source device, which is cumbersome and slow to respond.

[0005] (3) Insufficient sound quality adjustment capability; The sound quality of existing devices is entirely dependent on the input source, lacking independent adjustment functions for bass, midrange, and treble. Users cannot adjust the sound quality according to personal preferences or audio content type, resulting in harsh, unlayered sound and a poor listening experience.

[0006] (4) Lack of a graded volume control architecture; Existing equipment relies solely on the fixed gain of the power amplifier for amplification, lacking a tiered adjustment architecture with a pre-amplifier and secondary volume controllers. This makes it difficult to achieve gain compensation and fine-tuning of the audio signal, and to maintain a consistent listening experience across different input sources.

[0007] (5) Weak anti-interference ability; The audio input interface of existing equipment lacks effective electrostatic discharge (ESD) protection and DC blocking capacitor design, making it prone to generating unexplained abnormal noises due to ESD or the introduction of DC components. Furthermore, the lack of ferrite bead isolation for grounding easily introduces ground loop interference, affecting the purity of the audio signal.

[0008] In summary, existing LCD screen AUX audio input technology has significant shortcomings in terms of popping noise protection, automatic amplitude limiting, sound quality adjustment, and anti-interference. There is an urgent need for a circuit and device that can automatically detect audio insertion, monitor audio peaks in real time, automatically limit amplitude control, and have multi-level volume adjustment functions to improve the user experience. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide an automatic peak limiting control circuit for stereo input of an LCD screen, and to provide an automatic peak limiting control method for stereo input of an LCD screen, in view of the above-mentioned defects of the prior art.

[0010] The technical solution adopted by this invention to solve its technical problem is: An automatic peak limiting control circuit for stereo input of an LCD screen is constructed, comprising: an audio input unit including at least one audio input socket, wherein the audio input socket is configured with an insertion detection circuit; The main audio processor has its input terminal electrically connected to the output terminal of the audio input unit and integrates EQ low, mid, and high-frequency main volume adjustment functions; The peak detection and comparison unit has its input terminal electrically connected to the output terminal of the main audio processor. It is used to convert the audio AC signal into DC voltage and compare it with the threshold voltage, and output an over-exposure flag signal when the threshold voltage is exceeded. A volume controller, whose input is electrically connected to the output of the main audio processor, is used for two-level volume adjustment of the audio signal; The power amplifier unit has its input terminal electrically connected to the output terminal of the volume controller; A microcontroller unit has a first input terminal connected to the insertion detection circuit, a second input terminal connected to the peak detection and comparison unit, a first output terminal connected to the main audio processor, a second output terminal connected to the volume controller, and a third output terminal connected to the MUTE pin of the power amplifier unit; the microcontroller unit is configured as follows: When an audio connector is detected to be inserted, a MUTE signal is emitted through the third output terminal to put the power amplifier unit into a mute state. Detect whether the second input terminal receives the overexplosion flag signal; If the overexposure flag signal is received, the volume of the main audio processor is adjusted through the first output terminal, and the second input terminal is re-detected until the overexposure flag signal is no longer received; If the over-exposure flag signal is not received, the MUTE signal is canceled through the third output terminal, causing the power amplifier unit to exit the mute state.

[0011] The automatic peak limiting control circuit for stereo input of LCD screen according to the present invention includes, wherein the insertion detection circuit comprises: an ESD transistor, a first resistor, a second resistor, a third resistor, a fourth resistor, a first NPN transistor, and a first capacitor. The base of the first NPN transistor is connected to one end of the first resistor, one end of the second resistor, and one end of the third resistor. The other end of the first resistor is connected to the power supply, the other end of the second resistor is grounded, and the other end of the third resistor is connected to one end of the ESD transistor and the corresponding audio input jack. The other end of the ESD transistor is grounded. The emitter of the first NPN transistor is grounded, and the collector is connected to one end of the fourth resistor, one end of the first capacitor, and the first input terminal of the microcontroller unit. The other end of the fourth resistor is connected to the power supply, and the other end of the first capacitor is grounded.

[0012] The automatic peak limiting control circuit for stereo input of LCD screen according to the present invention includes an audio input unit comprising an AUDIO audio input jack and an AUX audio input jack. The main audio processor includes an audio processing chip; The first set of input terminals of the audio processing chip are connected to the two output terminals of the digital-to-analog converter chip through the fifth resistor and the sixth resistor, respectively, to receive analog audio signals from the digital-to-analog converter chip; The second set of input terminals of the audio processing chip are connected to the two output terminals of the AUDIO audio input socket through the seventh resistor and the eighth resistor, respectively, to receive analog audio signals from the AUDIO audio input socket; The third set of input terminals of the audio processing chip is connected to the two output terminals of the AUX audio input jack through the ninth resistor and the tenth resistor, respectively, to receive analog audio signals from the AUX audio input jack; The first output terminal of the audio processing chip is coupled to the first input terminal of the volume controller via the eleventh resistor and the second capacitor; the second output terminal of the audio processing chip is coupled to the second input terminal of the volume controller via the twelfth resistor and the third capacitor. The audio processing chip communicates with the microcontroller unit via an I²C bus.

[0013] The LCD screen stereo input peak automatic limiting control circuit of the present invention includes a peak detection and comparison unit comprising: a first operational amplifier, a second operational amplifier, an NMOS transistor, a diode, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, an eighteenth resistor, a nineteenth resistor, a twentieth resistor, a twenty-first resistor, a twenty-second resistor, a twenty-third resistor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, an eighth capacitor, and an electrolytic capacitor; The positive input terminal of the first operational amplifier is connected to the power supply through the twelfth resistor, and the negative input terminal is connected to one end of the thirteenth resistor, one end of the fourteenth resistor, one end of the fifteenth resistor, and one end of the fourth capacitor; the other end of the thirteenth resistor is connected to one end of the fifth capacitor, and the other end of the fifth capacitor is connected to the first output terminal of the audio processing chip; the other end of the fourteenth resistor is connected to one end of the sixth capacitor, and the other end of the sixth capacitor is connected to the second output terminal of the audio processing chip; the output terminal of the first operational amplifier is connected to the positive terminal of the diode, the other end of the fifteenth resistor, and the other end of the fourth capacitor. The negative terminal of the diode is connected to one end of the sixteenth resistor, and the other end of the sixteenth resistor is connected to the positive terminal of the electrolytic capacitor, one end of the seventh capacitor, and one end of the seventeenth resistor; the negative terminal of the electrolytic capacitor and the other end of the seventh capacitor are both grounded, and the other end of the seventeenth resistor is connected to one end of the eighteenth resistor and the positive input terminal of the second operational amplifier, and the other end of the eighteenth resistor is grounded. The negative input terminal of the second operational amplifier is connected to one end of the nineteenth resistor and one end of the twentieth resistor. The other end of the nineteenth resistor is connected to a 5V power supply, and the other end of the twentieth resistor is grounded. The output terminal of the second operational amplifier is connected to one end of the twenty-first resistor. The other end of the twenty-first resistor is connected to one end of the eighth capacitor, one end of the twenty-second resistor, and the gate (G) of the NMOS transistor. The other ends of the eighth capacitor and the twenty-second resistor are both grounded. The source (S) of the NMOS transistor is grounded, and the drain (D) is connected to one end of the twenty-third resistor and the second input terminal of the microcontroller unit. The other end of the twenty-third resistor is connected to the power supply.

[0014] The automatic peak limiting control circuit for stereo input of LCD screen according to the present invention includes a volume controller comprising a volume control chip. The LIN and RIN pins of the volume control chip serve as the first and second input terminals of the volume controller, respectively, and are correspondingly coupled to the first and second output terminals of the audio processing chip. The SCL and SDA pins of the volume control chip are connected to the microcontroller unit via the I²C communication bus. The LO and RO pins of the volume control chip are connected as output terminals to the input terminals of the power amplifier unit.

[0015] The automatic peak limiting control circuit for stereo input of LCD screen according to the present invention includes a power amplifier unit comprising a power amplifier chip. The MUTE pin of the power amplifier chip is connected to the third output terminal of the microcontroller unit through a second NPN transistor; The LIN and RIN pins of the power amplifier chip are respectively connected to a set of coupling capacitors and current-limiting resistors to the LO and RO pins of the volume control chip. The output of the power amplifier chip drives the speaker via an LC filter network.

[0016] The automatic peak limiting control circuit for stereo input of LCD screen described in this invention, wherein the microcontroller unit adopts an MCU chip; Pin 21 of the MCU chip is used as the third output terminal, pin 22 as the second input terminal, and pins 45 and 46 as the first output terminal and the second output terminal, respectively.

[0017] The automatic peak limiting control circuit for stereo input of LCD screen according to the present invention further includes a display unit; The digital-to-analog converter chip is connected to the display unit and is used to convert the I2S digital audio signal from the LCD screen main control chip into an analog signal. The display unit communicates with the microcontroller unit via the I²C bus to receive and display status prompts for volume overload and automatic attenuation.

[0018] The LCD screen stereo input peak automatic limiting control circuit of the present invention includes a main audio processor with a main volume adjustment range of 0dB to -78.75dB and a step size of 1.25dB; a bass and treble adjustment range of -14dB to +14dB; and a volume controller with a volume adjustment range of 0dB to -83dB and a step size of 1dB.

[0019] A method for automatic peak limiting control of stereo input on an LCD screen, employing the aforementioned automatic peak limiting control circuit for stereo input on an LCD screen, wherein the method includes: S1: Detects the insertion status of the audio input jack. When the insertion of the audio jack is detected, the microcontroller sends a MUTE signal through the third output terminal to put the power amplifier unit into a mute state. S2: In silent mode, the microcontroller detects whether the second input terminal receives the over-exposure flag signal output by the peak detector and comparison unit; S3: If an overexposure flag signal is received, the microcontroller reduces the volume of the main audio processor through the first output terminal, the volume controller keeps the current volume setting unchanged, and then returns to step S2 to re-detect until no overexposure flag signal is received. S4: If no over-explosion warning signal is received, the microcontroller cancels the MUTE signal through the third output terminal, causing the power amplifier unit to exit the mute state; S5: During normal playback after the power amplifier unit exits the mute state, if the over-exposure flag signal is detected again, the microcontroller unit will directly reduce the volume of the main audio processor through the first output terminal while maintaining the normal operation of the power amplifier unit. The volume controller will keep the current volume setting unchanged, and then return to step S2 to re-detect until the over-exposure flag signal disappears.

[0020] The beneficial effects of this invention are as follows: (1) Insertion detection and automatic mute to eliminate insertion and removal popping noises; By configuring an insertion detection circuit in the audio input jack and having the microcontroller immediately send a MUTE signal through the third output terminal when the audio connector is detected to be inserted, the power amplifier unit enters a mute state. This design silences the power amplifier the instant the audio connector is inserted, effectively preventing the popping sound problem caused by the amplification of the surge signal generated by hot-plugging, thus achieving noiseless insertion.

[0021] (2) Peak detection and closed-loop limiting automatically prevent overload distortion; By setting up a peak detection and comparison unit, the audio AC signal output by the main audio processor is converted into a DC voltage and compared with a threshold voltage. When the voltage exceeds the threshold, an over-exposure flag signal is output. After receiving this signal, the microcontroller adjusts the volume of the main audio processor through the first output terminal and continuously monitors until the over-exposure flag signal disappears. This closed-loop control mechanism enables the circuit to automatically reduce the output level of the main audio processor when the external audio source volume is too high, fundamentally eliminating the popping and distortion problems caused by input audio overload, without requiring the user to manually adjust the external audio source volume.

[0022] (3) A graded volume control architecture that balances amplitude limiting and user experience; By employing a two-stage cascaded architecture for the main audio processor and volume controller, the main audio processor handles EQ adjustment and the first-stage main volume control (for over-exposure prevention), while the volume controller handles the second-stage fine-tuning (maintaining user settings). During automatic limiting, the microcontroller only adjusts the volume of the main audio processor, while the volume controller keeps the user-set volume unchanged. This design achieves both automatic anti-exposure protection and ensures user autonomy over volume, enhancing ease of use.

[0023] (4) MUTE signal is automatically canceled, enabling seamless playback recovery; When the microcontroller detects the disappearance of the over-exposure flag signal, it automatically cancels the MUTE signal through the third output terminal, causing the power amplifier unit to exit the mute state. This design ensures that the power amplifier can automatically resume output after the audio signal returns to normal, without requiring manual operation by the user, achieving a seamless transition from mute to normal playback.

[0024] (5) Dynamic monitoring during playback, with continuous protection against popping sounds; During normal playback after the power amplifier unit has exited mute mode, if the external audio source suddenly increases in volume, triggering the over-exposure warning signal again, the microcontroller unit can directly adjust the volume of the main audio processor while maintaining normal operation of the power amplifier unit. This design achieves dynamic real-time limiting during playback, continuously providing anti-exposure protection even when the user adjusts the volume of the external audio source, ensuring a smooth listening experience throughout. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort: Figure 1 This is a block diagram of the automatic peak limiting control circuit for stereo input of the LCD screen according to a preferred embodiment of the present invention; Figure 2 This is an AUX audio input circuit diagram of the LCD screen stereo input peak automatic limiting control circuit according to a preferred embodiment of the present invention; Figure 3 This is an AUDIO audio input circuit diagram of the LCD screen stereo input peak automatic limiting control circuit according to a preferred embodiment of the present invention; Figure 4 This is a circuit diagram of the peak detection and comparison unit of the LCD screen stereo input peak automatic limiting control circuit according to a preferred embodiment of the present invention; Figure 5 This is a circuit diagram of the main audio processor of the LCD screen stereo input peak automatic limiting control circuit according to a preferred embodiment of the present invention; Figure 6 This is a circuit diagram of the volume controller of the LCD screen stereo input peak automatic limiting control circuit according to a preferred embodiment of the present invention; Figure 7 This is a circuit diagram of the microcontroller unit of the LCD screen stereo input peak automatic limiting control circuit according to a preferred embodiment of the present invention; Figure 8 This is a circuit diagram of the display unit of the LCD screen stereo input peak automatic limiting control circuit according to a preferred embodiment of the present invention; Figure 9This is a circuit diagram of the power amplifier unit of the LCD screen stereo input peak automatic limiting control circuit according to a preferred embodiment of the present invention; Figure 10 This is a circuit diagram of the digital-to-analog converter chip of the LCD screen stereo input peak automatic limiting control circuit according to a preferred embodiment of the present invention. Figure 11 This is a flowchart of a preferred embodiment of the present invention for an automatic peak limiting control method for stereo input of an LCD screen. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, a clear and complete description will be provided below in conjunction with the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0027] The preferred embodiment of the LCD screen stereo input peak automatic limiting control circuit of the present invention, such as... Figure 1 As shown, see also Figures 2-10 ,include: The audio input unit 100 includes at least one audio input jack, which is equipped with an insertion detection circuit. The main audio processor 200 has its input terminal electrically connected to the output terminal of the audio input unit 100, and integrates EQ low, mid, and high frequency main volume adjustment functions; The peak detection and comparison unit 300 has its input terminal electrically connected to the output terminal of the main audio processor 200. It is used to convert the audio AC signal into DC voltage and compare it with the threshold voltage, and output an over-exposure flag signal when the threshold voltage is exceeded. The volume controller 400 has its input terminal electrically connected to the output terminal of the main audio processor 200, and is used for two-level volume adjustment of the audio signal; The power amplifier unit 500 has its input terminal electrically connected to the output terminal of the volume controller 400; The microcontroller unit 600 has a first input terminal connected to the insertion detection circuit, a second input terminal connected to the peak detection and comparison unit 300, a first output terminal connected to the main audio processor 200, a second output terminal connected to the volume controller 400, and a third output terminal connected to the MUTE pin of the power amplifier unit 500. The microcontroller unit 600 is configured as follows: When the insertion of the audio connector is detected, a MUTE signal is sent through the third output terminal to put the power amplifier unit 500 into a mute state. Detect whether the second input terminal receives an overexplosion flag signal; If an overexposure flag signal is received, the volume of the main audio processor 200 is adjusted through the first output terminal, and the second input terminal is re-detected until no overexposure flag signal is received. If no over-explosion warning signal is received, the MUTE signal is canceled through the third output terminal, causing the power amplifier unit 500 to exit the mute state; The insertion detection circuit monitors the audio connector insertion status in real time and immediately mutes the power amplifier unit 500 when insertion is detected, effectively preventing the impact popping sound caused by hot plugging; at the same time, the peak detection and comparison unit 300 monitors the peak value of the audio signal in real time, and in conjunction with the closed-loop control logic of the microcontroller unit 600, the volume of the main audio processor 200 is automatically reduced when the audio is overloaded, fundamentally eliminating the popping sound distortion problem. like Figure 2 and Figure 3 As shown, the audio input unit 100 includes an AUDIO audio input jack JK1 and an AUX audio input jack JK2; each audio input jack corresponds to an insertion detection circuit. Taking the detection circuit corresponding to JK2 as an example, it is explained as follows: The insertion detection circuit includes: ESD transistor D11, first resistor R330, second resistor R329, third resistor R327, fourth resistor R328, first NPN transistor Q31, and first capacitor C254. The base of the first NPN transistor Q31 is connected to one end of the first resistor R330, one end of the second resistor R329, and one end of the third resistor R327. The other end of the first resistor R330 is connected to the power supply, the other end of the second resistor R329 is grounded, and the other end of the third resistor R327 is connected to one end of the ESD transistor D11 and the corresponding audio input jack. The other end of the ESD transistor D11 is grounded. The emitter of the first NPN transistor Q31 is grounded, and the collector is connected to one end of the fourth resistor R328, one end of the first capacitor C254, and the first input terminal of the microcontroller unit 600. The other end of the fourth resistor R328 is connected to the power supply, and the other end of the first capacitor C254 is grounded.

[0028] Electrostatic discharge protection is provided by ESD transistor D11 to prevent electrostatic breakdown from damaging subsequent circuits; reliable detection of the audio connector insertion status is achieved by pulling up the first resistor R330 and pulling down the ground pin of the audio jack; when the audio connector is not inserted, the microcontroller 600 receives a low-level signal; when the audio connector is inserted, the microcontroller 600 receives a high-level signal, accurately identifying the insertion event.

[0029] like Figure 5 and Figure 10 As shown, the main audio processor 200 includes an audio processing chip U500; The first set of input terminals of the audio processing chip U500 is connected to the two output terminals of the digital-to-analog converter chip U55 through the fifth resistor R544 and the sixth resistor R545 respectively, to receive the analog audio signal from the digital-to-analog converter chip U55; The second set of input terminals of the audio processing chip U500 are connected to the two output terminals of the AUDIO audio input jack JK1 through the seventh resistor R538 and the eighth resistor R539 respectively, to receive analog audio signals from the AUDIO audio input jack JK1; The third set of input terminals of the audio processing chip U500 is connected to the two output terminals of the AUX audio input jack JK2 through the ninth resistor R550 and the tenth resistor R551 respectively, to receive the analog audio signal from the AUX audio input jack JK2; The first output terminal of the audio processing chip U500 is coupled to the first input terminal of the volume controller 400 via the eleventh resistor R556 and the second capacitor C560; the second output terminal of the audio processing chip U500 is coupled to the second input terminal of the volume controller 400 via the twelfth resistor R557 and the third capacitor C561. The audio processing chip U500 communicates with the microcontroller unit 600 via the I²C bus.

[0030] The audio processing chip U500 receives three audio signals from the digital-to-analog converter chip U55, the AUDIO input, and the AUX input via three independent input terminals, enabling multi-source audio selection. The U500's built-in EQ low, mid, and high-frequency adjustment functions, as well as master volume control, allow users to adjust the sound quality according to the audio content type and personal preference. The audio signal is cleanly transmitted to the next-stage volume controller 400 via an RC coupling network consisting of the eleventh resistor R556, the second capacitor C560, the twelfth resistor R557, and the third capacitor C561, while simultaneously filtering out DC components.

[0031] like Figure 4 As shown, the peak detection and comparison unit 300 includes: a first operational amplifier U23-A, a second operational amplifier U23-B, an NMOS transistor Q32, a diode D12, a twelfth resistor R332, a thirteenth resistor R334, a fourteenth resistor R335, a fifteenth resistor R333, a sixteenth resistor R336, a seventeenth resistor R337, an eighteenth resistor R331, a nineteenth resistor R339, a twentieth resistor R338, a twenty-first resistor R340, a twenty-second resistor R341, a twenty-third resistor R342, a fourth capacitor C256, a fifth capacitor C257, a sixth capacitor C258, a seventh capacitor C259, an eighth capacitor C261, and an electrolytic capacitor C255; The positive input terminal of the first operational amplifier U23-A is connected to the power supply through the twelfth resistor R332. The negative input terminal is connected to one end of the thirteenth resistor R334, one end of the fourteenth resistor R335, one end of the fifteenth resistor R333, and one end of the fourth capacitor C256. The other end of the thirteenth resistor R334 is connected to one end of the fifth capacitor C257, and the other end of the fifth capacitor C257 is connected to the first output terminal of the audio processing chip U500. The other end of the fourteenth resistor R335 is connected to one end of the sixth capacitor C258, and the other end of the sixth capacitor C258 is connected to the second output terminal of the audio processing chip U500. The output terminal of the first operational amplifier U23-A is connected to the positive terminal of the diode D12, the other end of the fifteenth resistor R333, and the other end of the fourth capacitor C256. The cathode of diode D12 is connected to one end of the sixteenth resistor R336. The other end of the sixteenth resistor R336 is connected to the anode of electrolytic capacitor C255, one end of the seventh capacitor C259, and one end of the seventeenth resistor R337. The cathode of electrolytic capacitor C255 and the other end of the seventh capacitor C259 are both grounded. The other end of the seventeenth resistor R337 is connected to one end of the eighteenth resistor R331 and the positive input terminal of the second operational amplifier U23-B. The other end of the eighteenth resistor R331 is grounded. The negative input terminal of the second operational amplifier U23-B is connected to one end of the nineteenth resistor R339 and one end of the twentieth resistor R338. The other end of the nineteenth resistor R339 is connected to a 5V power supply, and the other end of the twentieth resistor R338 is grounded. The output terminal of the second operational amplifier U23-B is connected to one end of the twenty-first resistor R340. The other end of the twenty-first resistor R340 is connected to one end of the eighth capacitor C261, one end of the twenty-second resistor R341, and the gate of the NMOS transistor Q32. The other ends of the eighth capacitor C261 and the twenty-second resistor R341 are both grounded. The source of the NMOS transistor Q32 is grounded, and the drain is connected to one end of the twenty-third resistor R342 and the second input terminal of the microcontroller unit 600. The other end of the twenty-third resistor R342 is connected to the power supply.

[0032] The left and right channel audio signals are amplified by addition using the first operational amplifier U23-A, and then rectified by diode D12 and smoothed by electrolytic capacitor C255 to be converted into DC voltage. This DC voltage is then divided by resistors R337 and R331 and input to the positive input terminal of the second operational amplifier U23-B, where it is compared with a threshold voltage set by resistors R339 and R338. When the audio signal is too large and the DC voltage exceeds the threshold, the second operational amplifier U23-B outputs a high level, the NMOS transistor Q32 is turned on, the second input terminal of the microcontroller 600 is pulled low, and an over-exposure flag signal is received. This circuit realizes real-time detection of audio peaks and rapid output of over-exposure signals, with fast response speed and high detection accuracy.

[0033] like Figure 6 As shown, the volume controller 400 includes a volume control chip U400; The LIN and RIN pins of the volume control chip U400 serve as the first and second input terminals of the volume controller 400, respectively, and are correspondingly coupled to the first and second output terminals of the audio processing chip U500. The SCL and SDA pins of the volume control chip U400 are connected to the microcontroller unit 600 via the I²C communication bus. The LO and RO pins of the volume control chip U400 are connected as output terminals to the input terminals of the power amplifier unit 500.

[0034] The volume control chip U400 provides a second level of fine volume adjustment, with a volume adjustment range of 0dB to -83dB and a step size of 1dB. During automatic limiting, the volume control chip U400 keeps the user-set volume unchanged, and only the main audio processor 200 performs over-exposure prevention adjustment, which achieves both automatic protection and respects the user's volume preference.

[0035] like Figure 9 As shown, the power amplifier unit 500 includes a power amplifier chip U600; The MUTE pin of the power amplifier chip U600 is connected to the third output terminal of the microcontroller 600 through the second NPN transistor Q601; The LIN and RIN pins of the power amplifier chip U600 are connected to the LO and RO pins of the volume control chip U400, respectively, with a set of coupling capacitors and current-limiting resistors. The output of the power amplifier chip U600 drives the speaker SPK via an LC filter network.

[0036] The MUTE control of the power amplifier unit 500 is achieved through the second NPN transistor Q601. When the third output terminal of the microcontroller unit 600 outputs a low level, the second NPN transistor Q601 is cut off, the MUTE pin is pulled up to a high level, and the power amplifier chip U600 enters the mute state; when the third output terminal outputs a high level, the second NPN transistor Q601 is turned on, the MUTE pin is pulled down to a low level, and the power amplifier chip U600 exits the mute state. This circuit has a simple structure and a fast response. Combined with the control logic of the microcontroller unit 600, it achieves dual protection functions of insertion mute and over-explosion mute.

[0037] like Figure 7 As shown, the microcontroller unit 600 uses the MCU chip U3; Pin 21 of MCU chip U3 is used as the third output terminal, pin 22 is used as the second input terminal, and pins 45 and 46 are used as the first output terminal and the second output terminal, respectively.

[0038] The entire system is intelligently controlled by the MCU chip U3. The MCU chip U3 monitors the insertion detection signal and over-exposure flag signal in real time, and automatically executes MUTE control, volume adjustment and other operations according to the preset control logic without user intervention. At the same time, it communicates with the main audio processor 200 and the volume controller 400 through the I²C bus to achieve precise adjustment of volume and tone.

[0039] like Figure 8 and Figure 10 As shown, it also includes a display unit 700; U55 digital-to-analog converter chip ( Figure 1 The part marked 800 is connected to the display unit 700 and is used to hard decode the I2S digital audio signal from the LCD screen main control chip into an analog signal; The display unit 700 communicates with the microcontroller unit 600 via the I²C bus to receive and display status prompts for volume overload and automatic attenuation.

[0040] The display unit 700 intuitively presents the status information of volume overload and automatic attenuation to the user, allowing the user to understand the working status of the audio system in real time. When over-exposure or limiting occurs, the LCD screen will display corresponding prompts, enhancing the user's interactive experience. An automatic peak limiting control method for stereo input of an LCD screen, employing the aforementioned automatic peak limiting control circuit for stereo input of an LCD screen, such as... Figure 11 As shown, the method includes: S1: Detects the insertion status of the audio input jack. When the insertion of the audio jack is detected, the microcontroller unit 600 sends a MUTE signal through the third output terminal (pin 21) to put the power amplifier unit 500 into a mute state. S2: In silent mode, the microcontroller unit 600 detects whether the second input terminal (pin 22) receives the over-exposure flag signal output by the peak detector and comparison unit 300; S3: If an over-exposure flag signal is received, the microcontroller 600 reduces the volume of the main audio processor 200 through the first output terminal (pin 45, pin 46), the volume controller 400 keeps the current volume setting unchanged, and then returns to step S2 to re-detect until no over-exposure flag signal is received. S4: If no over-explosion flag signal is received, the microcontroller unit 600 cancels the MUTE signal through the third output terminal (pin 21), causing the power amplifier unit 500 to exit the mute state; S5: During normal playback after the power amplifier unit 500 exits the mute state, if the over-exposure flag signal is detected again, the microcontroller unit 600 will directly reduce the volume of the main audio processor 200 through the first output terminal (pin 45, pin 46) while keeping the power amplifier unit 500 in normal working condition. The volume controller 400 will keep the current volume setting unchanged, and then return to step S2 to detect again until the over-exposure flag signal disappears. The above control method realizes a complete closed-loop control process of automatic muting upon audio insertion, automatic amplitude limiting for excessive audio, and automatic resumption of playback after amplitude limiting. This method requires no user intervention, has a high degree of automation, effectively solves the problem of distortion caused by excessive input audio in existing technologies, and improves the user experience. It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A stereo input peak automatic limiting control circuit for an LCD screen, characterized in that, include: An audio input unit includes at least one audio input jack, the audio input jack being configured with an insertion detection circuit; The main audio processor has its input terminal electrically connected to the output terminal of the audio input unit and integrates EQ low, mid, and high-frequency main volume adjustment functions; The peak detection and comparison unit has its input terminal electrically connected to the output terminal of the main audio processor. It is used to convert the audio AC signal into DC voltage and compare it with the threshold voltage, and output an over-exposure flag signal when the threshold voltage is exceeded. A volume controller, whose input is electrically connected to the output of the main audio processor, is used for two-level volume adjustment of the audio signal; The power amplifier unit has its input terminal electrically connected to the output terminal of the volume controller; A microcontroller unit has a first input terminal connected to the insertion detection circuit, a second input terminal connected to the peak detection and comparison unit, a first output terminal connected to the main audio processor, a second output terminal connected to the volume controller, and a third output terminal connected to the MUTE pin of the power amplifier unit; the microcontroller unit is configured as follows: When an audio connector is detected to be inserted, a MUTE signal is emitted through the third output terminal to put the power amplifier unit into a mute state. Detect whether the second input terminal receives the overexplosion flag signal; If the overexposure flag signal is received, the volume of the main audio processor is adjusted through the first output terminal, and the second input terminal is re-detected until the overexposure flag signal is no longer received; If the over-exposure flag signal is not received, the MUTE signal is canceled through the third output terminal, causing the power amplifier unit to exit the mute state.

2. The automatic peak limiting control circuit for stereo input of the LCD screen according to claim 1, characterized in that, The insertion detection circuit includes: an ESD transistor, a first resistor, a second resistor, a third resistor, a fourth resistor, a first NPN transistor, and a first capacitor; The base of the first NPN transistor is connected to one end of the first resistor, one end of the second resistor, and one end of the third resistor. The other end of the first resistor is connected to the power supply, the other end of the second resistor is grounded, and the other end of the third resistor is connected to one end of the ESD transistor and the corresponding audio input jack. The other end of the ESD transistor is grounded. The emitter of the first NPN transistor is grounded, and the collector is connected to one end of the fourth resistor, one end of the first capacitor, and the first input terminal of the microcontroller unit. The other end of the fourth resistor is connected to the power supply, and the other end of the first capacitor is grounded.

3. The automatic peak limiting control circuit for stereo input of the LCD screen according to claim 1, characterized in that, The audio input unit includes an AUDIO audio input jack and an AUX audio input jack; The main audio processor includes an audio processing chip; The first set of input terminals of the audio processing chip are connected to the two output terminals of the digital-to-analog converter chip through the fifth resistor and the sixth resistor, respectively, to receive analog audio signals from the digital-to-analog converter chip; The second set of input terminals of the audio processing chip are connected to the two output terminals of the AUDIO audio input socket through the seventh resistor and the eighth resistor, respectively, to receive analog audio signals from the AUDIO audio input socket; The third set of input terminals of the audio processing chip is connected to the two output terminals of the AUX audio input jack through the ninth resistor and the tenth resistor, respectively, to receive analog audio signals from the AUX audio input jack; The first output terminal of the audio processing chip is coupled to the first input terminal of the volume controller via the eleventh resistor and the second capacitor; the second output terminal of the audio processing chip is coupled to the second input terminal of the volume controller via the twelfth resistor and the third capacitor. The audio processing chip communicates with the microcontroller unit via an I²C bus.

4. The automatic peak limiting control circuit for stereo input of the LCD screen according to claim 3, characterized in that, The peak detection and comparison unit includes: a first operational amplifier, a second operational amplifier, an NMOS transistor, a diode, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, an eighteenth resistor, a nineteenth resistor, a twentieth resistor, a twenty-first resistor, a twenty-second resistor, a twenty-third resistor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, an eighth capacitor, and an electrolytic capacitor; The positive input terminal of the first operational amplifier is connected to the power supply through the twelfth resistor, and the negative input terminal is connected to one end of the thirteenth resistor, one end of the fourteenth resistor, one end of the fifteenth resistor, and one end of the fourth capacitor; the other end of the thirteenth resistor is connected to one end of the fifth capacitor, and the other end of the fifth capacitor is connected to the first output terminal of the audio processing chip; the other end of the fourteenth resistor is connected to one end of the sixth capacitor, and the other end of the sixth capacitor is connected to the second output terminal of the audio processing chip; the output terminal of the first operational amplifier is connected to the positive terminal of the diode, the other end of the fifteenth resistor, and the other end of the fourth capacitor. The negative terminal of the diode is connected to one end of the sixteenth resistor, and the other end of the sixteenth resistor is connected to the positive terminal of the electrolytic capacitor, one end of the seventh capacitor, and one end of the seventeenth resistor; the negative terminal of the electrolytic capacitor and the other end of the seventh capacitor are both grounded, and the other end of the seventeenth resistor is connected to one end of the eighteenth resistor and the positive input terminal of the second operational amplifier, and the other end of the eighteenth resistor is grounded. The negative input terminal of the second operational amplifier is connected to one end of the nineteenth resistor and one end of the twentieth resistor. The other end of the nineteenth resistor is connected to a 5V power supply, and the other end of the twentieth resistor is grounded. The output terminal of the second operational amplifier is connected to one end of the twenty-first resistor. The other end of the twenty-first resistor is connected to one end of the eighth capacitor, one end of the twenty-second resistor, and the gate (G) of the NMOS transistor. The other ends of the eighth capacitor and the twenty-second resistor are both grounded. The source (S) of the NMOS transistor is grounded, and the drain (D) is connected to one end of the twenty-third resistor and the second input terminal of the microcontroller unit. The other end of the twenty-third resistor is connected to the power supply.

5. The automatic peak limiting control circuit for stereo input of the LCD screen according to claim 3, characterized in that, The volume controller includes a volume control chip; The LIN and RIN pins of the volume control chip serve as the first and second input terminals of the volume controller, respectively, and are correspondingly coupled to the first and second output terminals of the audio processing chip. The SCL and SDA pins of the volume control chip are connected to the microcontroller unit via the I²C communication bus. The LO and RO pins of the volume control chip are connected as output terminals to the input terminals of the power amplifier unit.

6. The automatic peak limiting control circuit for stereo input of the LCD screen according to claim 5, characterized in that, The power amplifier unit includes a power amplifier chip; The MUTE pin of the power amplifier chip is connected to the third output terminal of the microcontroller unit through a second NPN transistor; The LIN and RIN pins of the power amplifier chip are respectively connected to a set of coupling capacitors and current-limiting resistors to the LO and RO pins of the volume control chip. The output of the power amplifier chip drives the speaker via an LC filter network.

7. The automatic peak limiting control circuit for stereo input of the LCD screen according to claim 3, characterized in that, The microcontroller unit uses an MCU chip. Pin 21 of the MCU chip is used as the third output terminal, pin 22 as the second input terminal, and pins 45 and 46 as the first output terminal and the second output terminal, respectively.

8. The automatic peak limiting control circuit for stereo input of the LCD screen according to claim 3, characterized in that, It also includes a display unit; The digital-to-analog converter chip is connected to the display unit and is used to convert the I2S digital audio signal from the LCD screen main control chip into an analog signal. The display unit communicates with the microcontroller unit via the I²C bus to receive and display status prompts for volume overload and automatic attenuation.

9. The automatic peak limiting control circuit for stereo input of the LCD screen according to claim 1, characterized in that, The main audio processor has a main volume adjustment range of 0dB to -78.75dB with a step size of 1.25dB; the main audio processor has a bass and treble adjustment range of -14dB to +14dB; and the volume controller has a volume adjustment range of 0dB to -83dB with a step size of 1dB.

10. A method for automatic peak limiting control of stereo input on an LCD screen, using the automatic peak limiting control circuit for stereo input on an LCD screen as described in any one of claims 1-9, characterized in that, The method includes: S1: Detects the insertion status of the audio input jack. When the insertion of the audio jack is detected, the microcontroller sends a MUTE signal through the third output terminal to put the power amplifier unit into a mute state. S2: In the silent state, the microcontroller detects whether the second input terminal receives an over-explosion flag signal output by the peak detector and comparison unit; S3: If the over-exposure flag signal is received, the microcontroller reduces the volume of the main audio processor through the first output terminal, the volume controller keeps the current volume setting unchanged, and then returns to step S2 to re-detect until the over-exposure flag signal is no longer received; S4: If the over-exposure flag signal is not received, the microcontroller unit cancels the MUTE signal through the third output terminal, causing the power amplifier unit to exit the mute state; S5: During normal playback after the power amplifier unit exits the mute state, if the over-exposure flag signal is detected again, the microcontroller unit directly reduces the volume of the main audio processor through the first output terminal while maintaining the normal operation of the power amplifier unit. The volume controller keeps the current volume setting unchanged, and then returns to step S2 to re-detect until the over-exposure flag signal disappears.

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