Power amplifier connection switching system for automobile sound equipment calibration

Abstract

The invention relates to the technical field of automobile electronic testing, and discloses a power amplifier connection switching system for automobile sound equipment calibration, which comprises a central control module, a multi-channel switching matrix module, a state monitoring and analyzing module and a communication interface module. The multi-channel switching matrix module integrates a switching element array and an auxiliary switching network comprising a current-limiting resistor and an energy discharge branch; the state monitoring and analyzing module is used for monitoring electrical characteristics of equipment and capturing a signal zero crossing point. And the central control module responds to the switching instruction, calculates a switching risk index based on a load characteristic baseline and a target power amplifier damping coefficient, selects a direct switching, soft start or zero-crossing synchronous soft start strategy according to the switching risk index, and drives a switching matrix to execute a corresponding time sequence action. According to the invention, through quantitative risk assessment and multi-level strategy matching, switching surge and contact arc are effectively suppressed, audio impact noise is reduced, and safety and data accuracy of a calibration process are improved.

Description

Technical Field

[0001] This invention relates to the field of automotive electronic testing technology, specifically to a power amplifier connection switching system for automotive audio calibration. Background Technology

[0002] During the development and tuning phase of automotive audio systems, technicians frequently need to evaluate the matching effect between different models of power amplifiers and the vehicle's speaker system. To improve testing efficiency, automated switching matrix equipment is usually used to replace manual cable plugging and unplugging, enabling rapid switching between multiple amplifiers under test and the load.

[0003] However, existing switching devices have many technical limitations in practical applications. Traditional switching systems typically employ simple relay direct-connection logic, lacking mechanisms for pre-monitoring and evaluating circuit states. When switching channels during audio signal transmission or high-power output, due to the inductive load characteristics of the speaker voice coil, a high reverse induced electromotive force is generated at the moment the circuit is opened, and a large surge current is generated at the moment it is closed. This electrical surge not only easily causes arcing and gradual erosion of the relay contacts, shortening the equipment's lifespan, but also easily damages the output stage circuit of the power amplifier under test due to the current surge.

[0004] Furthermore, the switching action of existing equipment is usually performed asynchronously, meaning the switching time is independent of the phase state of the audio signal. If the switching action happens to occur at the peak of the audio signal voltage or current, it will momentarily truncate the signal, generating high-frequency transient pulses in the audio channel. This phenomenon manifests as noticeable popping sounds or impact noise, interfering with the stability of the acoustic testing environment and affecting subjective listening evaluation.

[0005] On the other hand, most existing switching systems lack the function of detecting the matching between load impedance and power amplifier driving capability, which can easily lead to forced connection under severe impedance mismatch, resulting in equipment overload. At the same time, such test systems usually need to be connected to an external host computer for control. Due to the lack of proper power and signal isolation circuits, ground loops can easily form between the host computer and the test equipment, introducing common-mode interference. This causes the acquired audio calibration data to be mixed with background noise, affecting the final test accuracy. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a power amplifier connection switching system for car audio calibration, which solves the problems of contact arcing, high audio transient impact noise, and equipment damage caused by the mismatch between load impedance and power amplifier damping characteristics during car audio calibration.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A power amplifier connection switching system for car audio calibration includes: a central control module, a multi-channel switching matrix module, a status monitoring and analysis module, and a communication interface module.

[0009] The multi-channel switching matrix module is equipped with input ports for connecting multiple power amplifiers under test (PADs) and output ports for connecting the vehicle speaker system. This module integrates a switching element array. The status monitoring and analysis module, connected to both the multi-channel switching matrix module and the central control module, monitors the electrical characteristics of the PADs connected to the input ports and the vehicle speaker system connected to the output ports, generating electrical characteristic monitoring data and sending it to the central control module. The communication interface module, connected to the central control module, receives switching commands from an external host computer and sends them back to the central control module.

[0010] The central control module is connected to the multi-channel switching matrix module, the status monitoring and analysis module, and the communication interface module. The central control module is configured to execute the following control logic: in response to a received switching command, it calculates the risk index of the current switching operation based on a pre-stored load characteristic baseline and the output characteristic parameters of the target power amplifier extracted from electrical characteristic monitoring data; based on the calculated risk index, it selects a matching switching strategy and generates a corresponding switching control signal, which is then sent to the multi-channel switching matrix module. The multi-channel switching matrix module is also configured to, in response to the switching control signal, execute corresponding switching timing actions to establish the connection loop between the target power amplifier under test and the vehicle speaker system.

[0011] Furthermore, to suppress inrush current and eliminate residual energy during switching, the multi-channel switching matrix module adopts a topology that includes a common audio bus, an auxiliary switching network, and output ports. The auxiliary switching network is integrated between the common audio bus and the output ports, and includes a soft-start control branch and an energy discharge branch. The soft-start control branch is connected in series in the connection loop between the common audio bus and the output ports, and consists of a current-limiting resistor and a bypass relay connected in parallel with the current-limiting resistor. The energy discharge branch is connected across the positive and negative terminals of the output ports, and consists of a discharge resistor and a discharge control relay connected in series.

[0012] Furthermore, to achieve precise zero-crossing and reduce electromagnetic interference, the condition monitoring and analysis module includes a signal zero-crossing detection circuit. This circuit utilizes a high-speed analog comparator, with its non-inverting input connected to the currently selected audio signal path and its inverting input connected to analog ground, and is configured with a positive feedback network to introduce hysteresis. The output of this high-speed analog comparator is connected to the external interrupt input pin of the central control module, used to output a hardware trigger signal synchronized with the zero-crossing of the audio signal as part of the electrical characteristic monitoring data to the central control module.

[0013] Furthermore, this invention introduces a risk assessment mechanism based on quantitative data. The central control module uses a switching risk index calculation logic to determine the risk index. The specific process includes: extracting the maximum load impedance amplitude from the load characteristic baseline, obtaining the damping coefficient of the target power amplifier from electrical characteristic monitoring data, substituting the maximum load impedance amplitude and the damping coefficient into the calculation logic, and calculating the switching risk index, which characterizes the transient impact risk level of the switching operation.

[0014] Based on the aforementioned risk indices, the central control module executes a tiered strategy selection: It determines whether the switching risk index is less than a preset low-risk threshold; if so, it selects a direct switching strategy. It then determines whether the switching risk index is between the low-risk threshold and a preset high-risk threshold; if so, it selects a soft-start switching strategy. Finally, it determines whether the switching risk index is greater than or equal to the high-risk threshold; if so, it selects a zero-crossing synchronization soft-start strategy. Both the low-risk and high-risk thresholds are dimensionless values ​​preset based on the system's tolerance capabilities.

[0015] Furthermore, when the system executes the zero-crossing synchronous soft-start strategy, the central control module sends a switching control signal containing specific timing logic to the multi-channel switching matrix module: first, it generates an instruction to disconnect the current channel and control the multi-channel switching matrix module to complete energy discharge; then, it confirms that the bypass relay in the multi-channel switching matrix module is in the open state; next, it monitors the hardware trigger signal from the status monitoring and analysis module, and after capturing the zero-crossing event, it generates an instruction to drive the channel switching relay of the target channel to close, so that current is injected into the load through the current-limiting resistor; it maintains the preset soft-start hold time; after the soft-start hold time ends, it monitors the hardware trigger signal again, and after the zero-crossing condition is met, it generates an instruction to drive the bypass relay to close, so that the current-limiting resistor is short-circuited.

[0016] Furthermore, this invention possesses the ability to automatically acquire key electrical parameters. The condition monitoring and analysis module integrates a reference load resistor. The central control module controls the multi-channel switching matrix module by sending switching control signals, causing the power amplifier under test to be in both an open-circuit state and a state connected to the reference load resistor, and reads the open-circuit voltage value and the load voltage value respectively. Using the open-circuit voltage value, the load voltage value, and the resistance value of the reference load resistor, the central control module calculates the damping coefficient using damping coefficient estimation logic.

[0017] Furthermore, during the load characteristic learning phase, the load characteristic analysis circuit in the central control module's control status monitoring and analysis module injects test signals into the vehicle speaker system to acquire voltage and current sampling sequences as electrical characteristic monitoring data. Frequency domain data is obtained by performing a Fast Fourier Transform on the voltage and current sampling sequences, and the complex impedance of the vehicle speaker system is calculated based on this frequency domain data, thereby establishing a load characteristic baseline.

[0018] To ensure signal integrity and security, the system also includes a power supply module. This power supply module constructs a zoned isolated power supply architecture, including a drive power supply branch for powering the multi-channel switching matrix module, a digital power supply branch for powering the central control module, and an analog power supply branch for powering the status monitoring and analysis module. The digital ground of the digital power supply branch and the analog ground of the analog power supply branch are connected only at the power input terminal through a ferrite bead or a zero-ohm resistor. Simultaneously, an electrical isolation circuit is provided between the communication interface module and the central control module, employing an Ethernet interface architecture or a serial communication architecture, and ground loop current between the external host computer and the central control module is blocked through a network isolation transformer or a digital isolation chip, respectively.

[0019] This invention provides a power amplifier connection switching system for car audio calibration. It has the following advantages:

[0020] 1. This invention establishes a risk assessment model based on load impedance and power amplifier damping coefficient, and dynamically matches direct switching, soft start, or zero-crossing synchronous soft start strategies according to the calculated risk index. Combined with the current-limiting resistors and energy discharge branches integrated in the multi-channel switching matrix module, the system can first discharge residual load energy and limit circuit surge current when performing high-risk switching operations. This effectively prevents arcing of relay contacts during high-current switching, extends the service life of switching components, and protects the output stage of the power amplifier under test from electrical shock damage.

[0021] 2. This invention utilizes the signal zero-crossing detection circuit in the state monitoring and analysis module, in conjunction with the microsecond-level timing control logic of the central control module, to force the switching action to remain synchronized with the zero-crossing point of the audio signal. This synchronous control mechanism ensures that the circuit performs state transitions at the moment when the voltage or current amplitude is at its lowest, eliminating high-frequency transient interference caused by asynchronous switching at the source, reducing popping and impact noise during audio calibration, and thus ensuring the acoustic stability of the test environment.

[0022] 3. This invention has the functions of establishing load characteristic baseline and real-time estimation of damping coefficient. It can sense the matching degree between the vehicle speaker and the amplifier under test before the physical connection is connected, avoiding equipment overload caused by severe impedance mismatch. In addition, by adopting a partitioned isolated power supply architecture and setting an electrical isolation circuit at the communication interface, this invention effectively blocks the ground loop current between the external host computer and the internal analog circuit of the system, suppresses the influence of common mode interference on audio signal acquisition, and improves the accuracy of calibration data and the anti-interference capability of the system. Attached Figure Description

[0023] Figure 1 This is a structural block diagram of a power amplifier connection switching system for car audio calibration according to an embodiment of the present invention;

[0024] Figure 2 This is a flowchart illustrating the process of a power amplifier connection switching method for car audio calibration according to an embodiment of the present invention.

[0025] Among them, 10 is the central control module; 20 is the multi-channel switching matrix module; 30 is the status monitoring and analysis module; 40 is the communication interface module; and 50 is the power supply module. Detailed Implementation

[0026] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] See attached document Figure 1 The present invention provides a power amplifier connection switching system for car audio calibration, which serves as the connection hub between multiple power amplifiers under test and the vehicle speaker system in the car audio calibration environment.

[0028] The system may include: a central control module 10, a multi-channel switching matrix module 20, a status monitoring and analysis module 30, a communication interface module 40, and a power supply module 50.

[0029] The central control module 10 is electrically connected to the multi-channel switching matrix module 20, the status monitoring and analysis module 30, and the communication interface module 40, respectively, and is used to perform data processing, algorithm calculation, timing control, and global scheduling of various modules of the system.

[0030] The multi-channel switching matrix module 20 integrates an array of switching elements that can be controlled by the central control module 10. This module has multiple input ports and one output port. The multiple input ports are used to connect to multiple power amplifiers under test, and the output port is used to connect to the vehicle's speaker system.

[0031] The status monitoring and analysis module 30 is used to monitor and analyze the electrical characteristics of the power amplifier under test and the vehicle speaker system connected to this system under the control of the central control module 10, and to provide the data obtained from the monitoring and analysis to the central control module 10.

[0032] The communication interface module 40 is used to establish a communication link between this system and an external host computer, and is responsible for receiving control commands from the host computer and sending status information of this system.

[0033] See attached document Figure 2 This invention provides a power amplifier connection switching method for car audio calibration, comprising the following steps:

[0034] S1, the system is powered on and started. The central control module 10 performs hardware function self-test and initialization configuration on the multi-channel switching matrix module 20, the status monitoring and analysis module 30 and the communication interface module 40.

[0035] S2, after the initial configuration is completed, the system enters the load characteristic learning stage. The central control module 10 controls the status monitoring and analysis module 30 to inject test signals into the connected vehicle speaker system, collect response data and calculate complex impedance spectrum, establish load characteristic baseline and store it.

[0036] S3. After the load characteristic baseline is established, the system enters the standby monitoring stage. The status monitoring and analysis module 30 continuously monitors the DC bias voltage of the output terminal of all power amplifiers under test that are connected to the input port but not selected. If an abnormality is detected, the corresponding channel is locked.

[0037] S4, During the standby monitoring phase, when the communication interface module 40 receives the switching command, the central control module 10 calculates the risk index of this switching operation based on the stored load characteristic baseline and the output characteristic parameters of the target power amplifier.

[0038] S5, based on the calculation results of the risk index, the central control module 10 selects a matching switching strategy, and when a zero-crossing point of the audio signal is detected, controls the multi-channel switching matrix module 20 to execute the corresponding switching timing action.

[0039] S6. After the switching timing action is completed, the central control module 10 generates switching result feedback information and sends it to the host computer through the communication interface module 40.

[0040] The following section will provide a detailed explanation of each step and the technical details involved, taking into account the specific circuit structure and algorithm logic.

[0041] See attached document Figure 1 The central control module 10 is electrically connected to the multi-channel switching matrix module 20, the status monitoring and analysis module 30, and the communication interface module 40, and is configured to perform data acquisition, logic operations, and hardware drive control.

[0042] The central control module 10 includes a microcontroller, a storage unit, a timer unit, and input / output interfaces. The microcontroller preferably employs a 32-bit microprocessor with a floating-point unit (FPU), such as a chip based on the ARM Cortex-M4 core, to meet the computational power requirements for performing a Fast Fourier Transform (FFT) on complex impedance spectra. The microcontroller's peripheral circuitry includes a clock oscillation circuit, a reset circuit, and a debugging interface; the specific circuit design is well-known in the art and will not be described in detail here.

[0043] The storage unit includes non-volatile memory and volatile memory. The non-volatile memory is used to store system firmware, configuration parameters, and load characteristic baselines. The load characteristic baselines include complex impedance amplitude data and phase data of the vehicle speaker system within a preset audio frequency range. The volatile memory is used to temporarily store real-time voltage sampling sequences and current sampling sequences transmitted by the condition monitoring and analysis module 30.

[0044] In terms of logical operations, the central control module 10 is configured to quantify the handover risk based on a preset algorithm. Specifically, the central control module 10 calculates the handover risk index using a handover risk index calculation formula. The handover risk index calculation formula is as follows:

[0045] ;

[0046] In the formula, This represents the switching risk index, which is a dimensionless value used to characterize the transient impact risk level of a switching operation. This represents the impedance weighting coefficient, which is a preset dimensionless constant. This represents the maximum impedance magnitude of the load, in ohms (Ω). This value is extracted from the load characteristic baseline by the central control module 10 and corresponds to the maximum impedance magnitude of the vehicle speaker system in the scanning frequency band. This indicates the speaker's rated impedance, measured in ohms (Ω). This value is a known nominal value. This constitutes the normalized load impedance term, used to characterize the difficulty of driving the load; This represents the damping weighting coefficient, which is a preset dimensionless constant; The damping coefficient of the target power amplifier is a dimensionless value, measured by the condition monitoring and analysis module 30. This constitutes the reciprocal term of the damping, used to characterize the power amplifier's ability to control the load's back electromotive force.

[0047] The central control module 10 also includes a hardware timer unit and an external interrupt interface. The external interrupt interface is connected to the output of the status monitoring and analysis module 30 and is configured to generate an interrupt signal in response to a zero-crossing event of the audio signal. The hardware timer unit is configured to generate a delay control signal with microsecond precision upon receiving the interrupt signal, for precise control of energy discharge time and soft-start access time.

[0048] In terms of hardware interfaces, the central control module 10 is connected to the multi-channel switching matrix module 20 via a general purpose input / output (GPIO) interface. To improve anti-interference capabilities, an optocoupler isolation circuit is connected in series between the GPIO interface and the relay drive circuit of the multi-channel switching matrix module 20. The central control module 10 is connected to the status monitoring and analysis module 30 via a serial communication bus (such as an SPI bus or an I2C bus) for sending control commands and reading sampled data.

[0049] The multi-channel switching matrix module 20 is positioned between multiple power amplifiers under test and the vehicle speaker system. The multi-channel switching matrix module 20 includes an input interface array, a channel selection unit, a common audio bus, an auxiliary switching network, and an output interface.

[0050] The input interface array contains N sets of terminals, each set corresponding to an output channel of the power amplifier under test. Given that car audio power amplifiers typically use a bridged load (BTL) output mode, each set of terminals includes both a positive and a negative input for receiving differential audio signals.

[0051] The channel selection unit consists of N groups of channel switching relays (denoted as N). to The system consists of N channel switching relays. Each group of channel switching relays is configured as a double-pole double-throw (DPDT) structure or a dual-channel double-pole single-throw (DPST) structure to simultaneously switch on and off the positive and negative paths of the audio signal. The contact material of the channel switching relays is preferably a gold-plated silver alloy to ensure that its contact resistance is less than a preset impedance threshold. The input sides of the N group of channel switching relays are connected to the corresponding input interface terminals, and the output sides of the N group of channel switching relays are connected in parallel to a common audio bus. The common audio bus includes a positive bus and a negative bus.

[0052] The auxiliary switching network is integrated between the common audio bus and the output interface. The auxiliary switching network includes a soft-start control branch and an energy discharge branch.

[0053] The soft-start control branch is connected in series in the connection loop between the common audio bus and the output interface. Specifically, the soft-start control branch includes a current-limiting resistor ( ) and a bypass relay connected in parallel with the current-limiting resistor ( A current-limiting resistor and a bypass relay are symmetrically installed on both the positive and negative circuits. The current-limiting resistor is a non-inductive power resistor, and its resistance is configured to be 1 to 3 times the rated impedance of the speaker. The control terminal of the bypass relay is connected to the central control module 10. Under normal conditions, the bypass relay is in the open state, allowing current to flow through the current-limiting resistor; in the closed state, the bypass relay short-circuits the current-limiting resistor, forming a low-impedance direct path.

[0054] The energy discharge branch is connected between the positive and negative terminals of the output interface. The energy discharge branch includes a discharge resistor connected in series (…). ) and discharge control relay ( The value of the bleed resistor is configured to be less than or equal to the rated impedance of the speaker system. The control terminal of the bleed control relay is connected to the central control module 10 and is used to close during the dead time of channel switching to dissipate the stored energy in the speaker load through the bleed resistor.

[0055] The multi-channel switching matrix module 20 also includes a relay drive circuit. The relay drive circuit is connected between the general-purpose input / output interface of the central control module 10 and the coils of each relay. The relay drive circuit uses a Darlington transistor array or a metal-oxide-semiconductor field-effect transistor (MOSFET) to form a low-side drive structure, and a freewheeling diode is connected in reverse parallel across each relay coil to absorb the induced electromotive force generated when the coil is disconnected, thus protecting the drive circuit.

[0056] The condition monitoring and analysis module 30 is electrically connected to the central control module 10 and the multi-channel switching matrix module 20, and is used to perform complex impedance characteristic measurement of the vehicle speaker system, electrical condition monitoring of the power amplifier, and real-time capture of the zero-crossing moment of the audio signal. The condition monitoring and analysis module 30 includes a load characteristic analysis circuit, a power amplifier condition monitoring circuit, and a signal zero-crossing detection circuit.

[0057] The load characteristic analysis circuit is used in conjunction with the central control module 10 to establish a baseline of the load characteristics of the vehicle speaker system. The load characteristic analysis circuit includes a signal excitation unit and a signal acquisition unit. The signal excitation unit consists of a digital-to-analog converter (DAC) and a power drive circuit, used to inject a variable-frequency test signal into the vehicle speaker system under the control of the central control module 10. The signal acquisition unit includes a precision sampling resistor connected in series in the loop. The system includes a dual-channel high-precision analog-to-digital converter (ADC). Precision sampling resistors are used to convert the current signal flowing through the speaker into a voltage signal. The ADC then samples the voltage signals across the speaker terminals. The voltage signal across the precision sampling resistor is used to obtain the current signal. .

[0058] The central control module 10 performs a Fast Fourier Transform (FFT) on the acquired discrete voltage and current sequences, converting the time-domain signals into frequency-domain signals, and uses the complex impedance calculation formula to calculate the loudspeaker system at different angular frequencies. The complex impedance is given by the formula:

[0059] ;

[0060] In the formula, Indicates angular frequency as The complex impedance at time includes the impedance magnitude part and the impedance phase part; Indicates angular frequency as The load voltage phasor at that time is obtained by performing a Fourier transform on the voltage sampling sequence; Indicates angular frequency as The load current phasor at that time is obtained by performing a Fourier transform on the current sampling sequence. This is achieved by changing the angular frequency. The value is set to cover the preset audio frequency band, and the central control module 10 can obtain the load characteristic baseline data including amplitude frequency characteristics and phase frequency characteristics.

[0061] The power amplifier status monitoring circuit is used to perform DC bias detection and damping factor estimation. For DC bias detection, this circuit includes a high input impedance buffer and an RC low-pass filter connected to each channel of the power amplifier under test. The cutoff frequency of the RC low-pass filter is set below 20Hz (e.g., 5Hz) to filter out AC audio components, extract the DC level component at the output, and transmit this DC level component to the analog-to-digital converter for threshold comparison.

[0062] For damping coefficient estimation, the condition monitoring and analysis module 30 integrates a reference load resistor ( The central control module 10 controls the multi-channel switching matrix module 20 to put the power amplifier under test (PAD) into an open-circuit state and a state connected to a reference load resistor, respectively. The central control module 10 calculates the damping coefficient of the PAD using a damping coefficient estimation formula. The damping coefficient estimation formula is as follows:

[0063] ;

[0064] In the formula, This represents the damping coefficient of the power amplifier under test, and its value is a dimensionless value. This represents the rated impedance of the loudspeaker, which is a known constant. This represents the effective value of the load terminal voltage measured when the power amplifier under test is connected to the reference load resistor; This represents the resistance value of the reference load resistor, which is a known constant. This represents the effective value of the output voltage measured when the power amplifier under test is in an open-circuit state. This represents the voltage drop caused by the voltage division due to the internal resistance of the power amplifier output. This formula is derived based on the voltage regulation principle and accurately reflects the power amplifier's ability to suppress the load back electromotive force.

[0065] A signal zero-crossing detection circuit is used to generate a hardware trigger signal synchronized with the zero-crossing point of the audio signal. This circuit includes a high-speed analog comparator. The non-inverting input of the high-speed analog comparator is connected to the currently selected audio signal path, and the inverting input is connected to the analog ground level. To improve noise immunity and prevent signal noise from causing multiple flips near the zero-crossing point, the high-speed analog comparator is configured with a positive feedback network to introduce hysteresis. When the instantaneous level of the audio signal crosses the zero point and the hysteresis interval, the output of the high-speed analog comparator generates a level transition. This transition signal is directly connected to the external interrupt input pin of the central control module 10 as a time reference for initiating the switching sequence.

[0066] See attached document Figure 1 The communication interface module 40 is connected to the central control module 10 and is configured as a data transmission channel between this system and an external host computer. The communication interface module 40 receives switching commands and configuration parameters sent by the host computer and sends status feedback information and load characteristic baseline data of this system.

[0067] The communication interface module 40 includes a physical interface circuit and a level conversion circuit. In one embodiment, the communication interface module 40 adopts an Ethernet interface architecture, which includes an RJ45 connector, a network isolation transformer, and a physical layer transceiver (PHY) connected in sequence. The network isolation transformer is configured to electrically isolate the communication line and suppress common-mode interference. The physical layer transceiver is connected to the Media Access Control (MAC) interface of the central control module 10. In another embodiment, the communication interface module 40 adopts a serial communication architecture, which includes a USB-to-serial bridge chip and a digital isolation chip. The digital isolation chip is disposed between the USB-to-serial bridge chip and the Universal Asynchronous Receiver / Transmitter (UART) interface of the central control module 10 to block ground loop current between the host computer and the system, ensuring signal integrity. The specific circuit connection methods of the above interfaces can be designed by those skilled in the art based on relevant chip datasheets; these are well-known technologies in the field and will not be elaborated further here.

[0068] The input terminal of the power module 50 is connected to an external power supply, and the output terminal is electrically connected to the central control module 10, the multi-channel switching matrix module 20, and the status monitoring and analysis module 30, respectively. The power module 50 is configured to construct a partitioned isolated power supply architecture, including a main power conversion unit, a drive power branch, a digital power branch, and an analog power branch.

[0069] The main power conversion unit is used to convert the externally input DC power supply into the intermediate DC bus voltage.

[0070] The drive power supply branch is connected between the intermediate DC bus voltage and the multi-channel switching matrix module 20. The drive power supply branch includes an LC filter network to provide drive power to the relay coil. The LC filter network is configured to suppress transient current fluctuations and conducted interference from reverse induced electromotive force generated during relay operation on other power supply branches.

[0071] The digital power supply branch is connected between the intermediate DC bus voltage and the central control module 10 and the communication interface module 40. The digital power supply branch uses a step-down switching regulator (DC-DC Buck Converter) to provide the low DC voltage required by the logic circuit.

[0072] The analog power supply branch is connected between the intermediate DC bus voltage and status monitoring and analysis module 30. The analog power supply branch uses a low-dropout linear regulator (LDO) to provide low-ripple, high-power-resistance analog power to the operational amplifier and analog-to-digital converter. Furthermore, the power module 50 employs a single-point grounding topology; the digital ground (DGND) of the digital power supply branch and the analog ground (AGND) of the analog power supply branch are connected only at the power input terminal via a ferrite bead or a zero-ohm resistor to isolate the influence of digital switching noise on the analog signal acquisition circuit.

[0073] The central control module 10 integrates a non-volatile storage unit, which contains a core data structure library to support system operation. This core data structure library is logically divided into a load characteristic baseline storage area and a system configuration parameter storage area. The central control module 10 organizes and manages the data according to the following steps or structural definitions:

[0074] S301, Construct the load characteristic baseline data structure. The load characteristic baseline storage area is used to store the frequency response impedance data of the entire vehicle speaker system. This data is organized in the form of a frequency-complex impedance mapping table, containing N data nodes. Each data node corresponds to a discrete frequency point. ), and store the impedance amplitude at that frequency point ( ) and impedance phase ( The frequency distribution covers a preset audio test frequency band (e.g., 20Hz to 20kHz). When performing a switching risk assessment, the central control module 10 extracts the maximum value as the maximum load impedance value by traversing the impedance amplitude data in the mapping table. ), used for the calculation of the aforementioned switching risk index formula.

[0075] S302, Configure algorithm weight coefficients. The system configuration parameter storage area stores impedance weight coefficients ( ) and damping weight coefficient ( These two coefficients are configured as readable and writable floating-point data. The communication interface module 40 can respond to instructions from the host computer to perform online corrections on these two coefficients, thereby adjusting the emphasis of the central control module 10 on load impedance characteristics and power amplifier control characteristics when calculating the switching risk index.

[0076] S303 stores hardware calibration parameters. The system configuration parameter storage area stores the actual calibration value of the precision sampling resistor ( ) and the actual calibrated value of the reference load resistance ( When performing complex impedance calculation and damping coefficient estimation, the central control module 10 calls the actual calibration value instead of the theoretical nominal value to participate in the calculation, so as to eliminate the measurement error introduced by component manufacturing tolerances and improve the calculation accuracy.

[0077] S304 defines timing control parameters. The system configuration parameter storage area stores the energy release time ( ) and soft-start retention time ( ).

[0078] Energy release time ( The discharge control relay in the multi-channel switching matrix module 20 is defined. The duration of closure within the switching dead zone is preferably between 50 milliseconds and 200 milliseconds.

[0079] Soft start hold time ( The bypass relay in the multi-channel switching matrix module 20 is defined. The delay time after the main channel is closed is preferably between 100 milliseconds and 500 milliseconds. The central control module 10 configures a hardware timer according to the timing control parameters to precisely control the action sequence of each relay.

[0080] S305, set the safety protection threshold. The system configuration parameter storage area stores the DC bias alarm threshold ( The central control module 10 is configured to compare the DC voltage value detected in real time by the status monitoring and analysis module 30 with the threshold. If the value exceeds the threshold, a channel locking mechanism is triggered.

[0081] The central control module 10 is configured to run a switching risk assessment program after receiving a switching command for the target power amplifier in order to determine the appropriate hardware action timing strategy.

[0082] S321, Central Control Module 10 performs parameter extraction. Central Control Module 10 accesses the load characteristic baseline storage area, traverses the frequency complex impedance mapping table, and retrieves the maximum impedance amplitude of the vehicle speaker system within a preset frequency band. Simultaneously, the central control module 10 acquires the damping factor (DF) of the target power amplifier. If the current damping factor data is invalid or expired, the central control module 10 will retrieve the default value stored in the system configuration parameter storage area. Furthermore, the central control module 10 reads the impedance weighting coefficient (DF). Damping weighting coefficient ( ) and speaker rated impedance ( ).

[0083] S322, the central control module 10 uses a handover risk index calculation formula to quantify the current handover risk. The handover risk index calculation formula is:

[0084] .

[0085] S323, the central control module 10 will calculate the switching risk index ( ) and the preset low-risk threshold ( ) and high-risk threshold ( Compare the results to select the switching strategy:

[0086] Low-risk mode ( The central control module 10 executes a direct switching strategy. The timing sequence is as follows: the control multi-channel switching matrix module 20 disconnects the relay of the current channel; waits for a preset mechanical dead time; and closes the relay of the target channel. In this mode, the bypass relay remains closed, and the soft-start function is not activated.

[0087] Medium risk model ( Central control module 10 executes a soft-start switching strategy. The timing sequence is: disconnect the relay for the current channel; close the energy discharge relay (…). And maintain energy release time ( Disconnect the energy discharge relay; ensure the bypass relay ( The relay is in the open state; the relay that closes the target channel (at this time, current flows through the current-limiting resistor). ); Maintain soft-start retention time Close the bypass relay (short-circuit the current-limiting resistor, restore shoot-through).

[0088] High-risk mode ( The central control module 10 executes a zero-crossing synchronous soft-start strategy. Under this strategy, the central control module 10 executes the same relay action sequence as the medium-risk mode described above, but the triggering time of each relay action is based on the interrupt signal output by the status monitoring and analysis module 30, and is forced to synchronize with the zero-crossing point of the audio signal to minimize contact arcing and signal truncation noise.

[0089] S324, the central control module 10 generates the corresponding GPIO control sequence according to the determined switching strategy and writes it into the hardware execution queue to drive the multi-channel switching matrix module 20 to complete the physical switching.

[0090] The central control module 10 runs a finite state machine (FSM) program to manage the timing of the actions of each relay in the multi-channel switching matrix module 20. This finite state machine program defines the input response and output control logic of the system at different switching stages.

[0091] S331, the system is in an idle hold state. In this state, the central control module 10 maintains the relay state of the currently closed channel and polls the receive buffer of the communication interface module 40. When the central control module 10 parses a valid switching command and the aforementioned risk assessment algorithm has output a clear switching strategy control, the state machine transitions to the disconnection processing state.

[0092] S332, the system executes the safety disconnect phase. The central control module 10 controls the currently closed channel switching relay ( Disconnect. If the current switching strategy is "zero-crossing synchronous soft-start strategy", the central control module 10 first enables external interrupt requests, using the comparator signal output by the status monitoring and analysis module 30 as the interrupt source. When a zero-crossing interrupt (rising edge or falling edge) of the audio signal is captured, the central control module 10 immediately toggles the GPIO level in the interrupt service function to disconnect the relay. After the relay is disconnected, the central control module 10 starts a hardware timer to enter dead-time counting, forcibly maintaining the preset minimum dead time. This dead time is configured to be greater than the mechanical release time of the relay (e.g., 10ms) to prevent common-mode conduction between the old and new channels at the moment of switching.

[0093] S334, the system executes the current-limiting access phase. This phase is only executed under the "soft-start switching strategy" or the "zero-cross synchronization soft-start strategy". The central control module 10 first detects and ensures the bypass relay ( The soft-start current-limiting resistor is in the off state, causing it to be in the soft-start current-limiting resistor ( It is connected in series in the circuit. Subsequently, if the current switching strategy is a "zero-crossing synchronous soft-start strategy", the central control module 10 will wait for the zero-crossing interrupt signal output by the status monitoring and analysis module 30; after capturing the zero-crossing event, or if the current strategy is only a "soft-start switching strategy" and there is no need to wait for the zero-crossing, the central control module 10 drives the channel switching relay of the target channel ( The circuit breaker closes. At this time, the output current of the power amplifier is injected into the load through the current-limiting resistor, and the voltage build-up rate across the load is limited. The system maintains this state until the preset soft-start hold time is reached.

[0094] S335, the system executes the full-power conduction phase. If a "direct switching strategy" is used, the central control module 10 will first close the bypass relay after the dead time ends. The current-limiting resistor is short-circuited, and then the channel switching relay of the target channel is closed. This achieves a direct physical connection with low impedance. If a "soft-start switching strategy" or a "zero-crossing synchronous soft-start strategy" is used, the soft-start hold time ( After completion, if the current switching strategy is "zero-crossing synchronous soft-start strategy", the central control module 10 will again detect and wait for the zero-crossing point of the audio signal; if the zero-crossing condition is met or in a non-high-risk mode, the central control module 10 will drive the bypass relay ( The bypass relay will close the current-limiting resistor. A short circuit switches the circuit to pass-through mode, allowing the power amplifier to resume full damping control of the speaker.

[0095] S336, the state machine returns to the idle hold state. The central control module 10 sends a switch completion confirmation frame to the host computer through the communication interface module 40. In any of the above stages, if the state monitoring and analysis module 30 detects that the DC bias voltage exceeds the safety threshold, the state machine will immediately jump to the fault lockout state through the highest priority interrupt, unconditionally disconnect all relays and lock the system until a reset command is received.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A power amplifier connection switching system for car audio calibration, characterized in that, It includes a central control module, a multi-channel switching matrix module, a status monitoring and analysis module, and a communication interface module; The multi-channel switching matrix module is provided with input ports for connecting multiple power amplifiers under test and output ports for connecting the vehicle speaker system. The multi-channel switching matrix module integrates a switching element array. The status monitoring and analysis module is connected to the multi-channel switching matrix module and the central control module, and is used to monitor the electrical characteristics of the power amplifier under test connected to the input port and the vehicle speaker system connected to the output port, generate electrical characteristic monitoring data and send it to the central control module; The communication interface module is connected to the central control module and is used to receive switching instructions sent by an external host computer and send them to the central control module. The central control module is connected to the multi-channel switching matrix module, the status monitoring and analysis module, and the communication interface module, respectively; the central control module is configured as follows: In response to the received switching command, the risk index of this switching operation is calculated based on the pre-stored load characteristic baseline and the output characteristic parameters of the target power amplifier extracted from the electrical characteristic monitoring data. Based on the calculation results of the risk index, a matching switching strategy is selected, and a corresponding switching control signal is generated and sent to the multi-channel switching matrix module. The multi-channel switching matrix module is also configured to respond to the switching control signal by performing a corresponding switching timing action to connect the connection circuit between the target power amplifier under test and the vehicle speaker system.

2. The power amplifier connection switching system for car audio calibration according to claim 1, characterized in that, The multi-channel switching matrix module includes a common audio bus, an auxiliary switching network, and an output port; The auxiliary switching network is integrated between the common audio bus and the output port, and the auxiliary switching network includes a soft-start control branch and an energy discharge branch. The soft-start control branch is connected in series in the connection loop between the common audio bus and the output port. The soft-start control branch includes a current-limiting resistor and a bypass relay connected in parallel with the current-limiting resistor. The energy discharge branch is connected between the positive and negative terminals of the output port, and the energy discharge branch includes a discharge resistor and a discharge control relay connected in series.

3. The power amplifier connection switching system for car audio calibration according to claim 1, characterized in that, The status monitoring and analysis module includes a signal zero-crossing detection circuit; The signal zero-crossing detection circuit includes a high-speed analog comparator. The non-inverting input of the high-speed analog comparator is connected to the currently selected audio signal path, and the inverting input is connected to the analog ground level. The high-speed analog comparator is configured with a positive feedback network to introduce hysteresis characteristics. The output of the high-speed analog comparator is connected to the external interrupt input pin of the central control module, and is used to output a hardware trigger signal that is synchronized with the zero-crossing point of the audio signal as part of the electrical characteristic monitoring data to the central control module.

4. The power amplifier connection switching system for car audio calibration according to claim 3, characterized in that, The central control module calculates the risk index using the switching risk index calculation formula and is specifically configured to perform the following actions: Extract the maximum load impedance amplitude from the load characteristic baseline; Obtain the damping coefficient of the target power amplifier from the electrical characteristic monitoring data; Substituting the maximum load impedance amplitude and the damping coefficient into the switching risk index calculation formula, the switching risk index, which characterizes the transient impact risk level of the switching operation, is calculated.

5. The power amplifier connection switching system for car audio calibration according to claim 4, characterized in that, The central control module is configured to perform the following comparison action to select the switching strategy: Determine whether the switching risk index is less than a preset low-risk threshold; if so, select a direct switching strategy. Determine whether the switching risk index is greater than or equal to the low-risk threshold and less than the preset high-risk threshold. If so, select the soft-start switching strategy. Determine whether the switching risk index is greater than or equal to the high-risk threshold. If so, select the zero-cross synchronization soft-start strategy. Wherein, both the low-risk threshold and the high-risk threshold are dimensionless values ​​preset based on the system's tolerance capacity.

6. The power amplifier connection switching system for car audio calibration according to claim 5, characterized in that, When the switching strategy is the zero-crossing synchronous soft-start strategy, the central control module is configured to send a switching control signal containing the following timing logic to the multi-channel switching matrix module: The command is generated to disconnect the current channel and control the multi-channel switching matrix module to complete energy release. Confirm that the bypass relay in the multi-channel switching matrix module is in the off state; The hardware trigger signal from the status monitoring and analysis module is monitored, and after a zero-crossing event is captured, an instruction is generated to drive the channel switching relay of the target channel to close, so that current is injected into the load through the current limiting resistor. Maintain the preset soft-start hold time; After the soft-start hold time ends, the hardware trigger signal is monitored again. If the zero-crossing condition is met, an instruction is generated to drive the bypass relay to close, causing the current-limiting resistor to short-circuit.

7. The power amplifier connection switching system for car audio calibration according to claim 1, characterized in that, The condition monitoring and analysis module integrates a reference load resistor; the central control module is configured to perform the following actions to obtain the damping coefficient: Send the switching control signal to control the multi-channel switching matrix module so that the power amplifier under test is in an open circuit state, and read the open circuit voltage value from the electrical characteristic monitoring data; Sending the switching control signal controls the multi-channel switching matrix module to connect the power amplifier under test to the reference load resistor, and reads the load voltage value from the electrical characteristic monitoring data; The damping coefficient is calculated using the open-circuit voltage value, the load voltage value, and the resistance value of the reference load resistor, employing a damping coefficient estimation formula.

8. The power amplifier connection switching system for car audio calibration according to claim 1, characterized in that, The status monitoring and analysis module includes a load characteristic analysis circuit; the central control module is configured to perform the following actions during the load characteristic learning phase: The load characteristic analysis circuit is controlled to inject test signals into the vehicle speaker system. Acquire the voltage sampling sequence and current sampling sequence as the electrical characteristic monitoring data; Perform a Fast Fourier Transform on the voltage sampling sequence and the current sampling sequence to obtain frequency domain data; Based on the frequency domain data, the complex impedance of the vehicle speaker system is calculated using the complex impedance calculation formula, and the load characteristic baseline is established.

9. The power amplifier connection switching system for car audio calibration according to claim 1, characterized in that, It also includes a power module; The power supply module is configured to construct a partitioned isolated power supply architecture, which includes a drive power supply branch for powering the multi-channel switching matrix module, a digital power supply branch for powering the central control module, and an analog power supply branch for powering the status monitoring and analysis module; the digital ground of the digital power supply branch and the analog ground of the analog power supply branch are connected only at the power input terminal through a ferrite bead or a zero-ohm resistor.

10. The power amplifier connection switching system for car audio calibration according to claim 1, characterized in that, An electrical isolation circuit is provided between the communication interface module and the central control module; the communication interface module adopts an Ethernet interface architecture or a serial communication architecture, and respectively blocks the ground loop current between the external host computer and the central control module through a network isolation transformer or a digital isolation chip.

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