Audio voltage limiter based on Schottky diode and application thereof

Abstract

The invention relates to the technical field of audio signal processing, in particular to an audio voltage limiter based on a Schottky diode and application of the audio voltage limiter, the audio voltage limiter comprises a diode threshold value unit and a voltage division attenuation unit, the diode threshold value unit sets a voltage limit threshold value through diode type combination; the voltage division attenuation unit forms an N: 1 voltage division network by two resistors so as to realize compression ratio control; the diode threshold unit is formed by at least two diodes which are reversely connected in parallel or are subjected to bridge rectification; the voltage limiter breaks through the cost and volume limitation of the traditional voltage limiter, realizes efficient dynamic control through the extremely simple combination of the diodes and the resistors, and is particularly suitable for the scenes sensitive to the cost, such as automobile audio and the like. The modular design supports flexible adjustment of a threshold value, and a signal protection scheme with high cost performance is provided for the fields of vehicle-mounted sound equipment, consumer electronics and the like.

Description

Technical Field

[0001] This invention relates to the field of audio signal processing technology, specifically to an audio limiter based on a Schottky diode and its applications. Background Technology

[0002] Traditional audio limiters rely on complex operational amplifiers or dedicated chips, costing as much as $10-20, making them unsuitable for the low-cost requirements of automotive audio systems. In automotive scenarios, when the output voltage of the power amplifier chip (such as the TDA7388) exceeds 8V (16W power for a 4Ω load), it is prone to cutoff distortion or speaker damage due to excessive volume, and existing solutions cannot be widely adopted due to size and cost limitations. Summary of the Invention

[0003] (a) Purpose of the invention To address the technical problems existing in the background art, this invention proposes an audio limiter based on a Schottky diode and its application.

[0004] (II) Technical Solution To address the aforementioned technical problems, this invention provides an audio limiter based on a Schottky diode, comprising a diode threshold unit and a voltage divider attenuation unit, wherein: The diode threshold unit sets the voltage limit threshold by combining diode types; The voltage divider attenuation unit consists of an N:1 voltage divider network composed of two resistors to achieve compression ratio control; The diode threshold unit is composed of at least two diodes connected in reverse parallel or a bridge rectifier.

[0005] Preferably, when two Schottky diodes are connected in reverse parallel, the threshold voltage is 200mV±20mV; When a bridge rectifier with four Schottky diodes is used, the threshold voltage is 400mV±30mV.

[0006] Preferably, the voltage divider network resistors satisfy R1 / R2=N, and the compression ratio can be adjusted from 3:1 to 5:1 by adjusting the resistance ratio.

[0007] Preferably, the Schottky diode anti-parallel circuit includes: input Vin, output Vout, resistor R1, resistor R2, and two diodes D1 and D2 connected in anti-parallel; wherein, One end of resistor R1 is connected to the input Vin, and the other end is connected to the output Vout. One end of resistor R2 is connected to the output Vout, and the other end is connected to the cathode of diode D1 and the anode of diode D2. The anode of diode D1 is connected to the cathode of diode D2 and grounded.

[0008] Preferably, the Schottky diode bridge rectifier circuit includes: input Vin, output Vout, resistor R1, resistor R2, and four diodes D1, D2, D3, and D4 constituting the rectifier; wherein, One end of the resistor R1 is connected to the input Vin, and the other end is connected to the output Vout. Diodes D1 to D4 are connected in series, and the cathode of diode D1 is connected to the anode of diode D2 and then connected to the output Vout. The cathode of diode D3 is connected to the anode of diode D4 and then grounded. The two ends of the resistor R2 are respectively connected to the common terminal of diodes D1 and D3, and the common terminal of diodes D2 and D4.

[0009] Preferably, the resistor R2 is a variable resistor, and a diode D5 is connected between the resistor R2 and the common terminal of diodes D2 and D4. The cathode of the diode D5 is connected to the resistor R2, and the anode is connected to the common terminal of diodes D2 and D4.

[0010] The application of Schottky diode-based audio limiters in automotive audio systems involves connecting the power amplifier chip in series at the signal input to prevent output overload.

[0011] Preferably, the power amplifier chip includes, but is not limited to, TDA7388 and TDA7851.

[0012] The above-described technical solution of the present invention has the following beneficial technical effects: The design of this invention costs less than $0.20, requires only 2-5 diodes and 2 resistors, has an adjustable threshold, can be achieved by replacing the diodes, has a volume of less than 2 square centimeters, and a distortion rate of less than 0.1%. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the reverse parallel circuit structure of the two Schottky diodes in this invention; Figure 2 This is a schematic diagram of the Schottky diode bridge rectifier circuit structure in this invention; Figure 3 This is a schematic diagram of the combined circuit structure of bridge rectifier and diode in this invention; Figure 4 This is a schematic diagram of the circuit structure in one embodiment of the present invention. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0015] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" are not specifically singular and may include plural forms. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0016] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0017] In the description of this application, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0018] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0019] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, these terms have no special meaning and therefore should not be construed as limiting the scope of protection of this application. Additionally, although the terminology used in this application is selected from commonly known and used terms, some terms mentioned in this application's specification may have been chosen by the applicant according to his or her judgment, and their detailed meanings are explained in the relevant sections of this description. Moreover, this application should be understood not only through the actual terms used, but also through the meaning implied by each term. Definition: MCU: Controller.

[0020] This application proposes an audio limiter based on a Schottky diode and its application. The limiter threshold is set by the diode's forward voltage, and the compression ratio is controlled by the resistor voltage division ratio, thus constructing a very simple and low-cost limiter.

[0021] Specifically as follows: The audio limiter includes a diode threshold unit and a voltage divider attenuation unit, wherein: The diode threshold unit sets the voltage limit threshold by combining diode types; The voltage divider attenuation unit consists of an N:1 voltage divider network composed of two resistors to achieve compression ratio control; The diode threshold unit is composed of at least two diodes connected in reverse parallel or a bridge rectifier.

[0022] refer to Figure 1 When two Schottky diodes are connected in reverse parallel, the threshold voltage is 200mV±20mV. The Schottky diode reverse parallel circuit includes: input Vin, output Vout, resistor R1, resistor R2, and two diodes D1 and D2 connected in reverse parallel; wherein, One end of resistor R1 is connected to the input Vin, and the other end is connected to the output Vout. One end of resistor R2 is connected to the output Vout, and the other end is connected to the cathode of diode D1 and the anode of diode D2. The anode of diode D1 is connected to the cathode of diode D2 and grounded.

[0023] refer to Figure 2 When a bridge rectifier using four Schottky diodes is employed, the threshold voltage is 400mV ± 30mV. The Schottky diode bridge rectifier circuit includes: input Vin, output Vout, resistors R1 and R2, and four diodes D1, D2, D3, and D4 constituting the rectifier; wherein, One end of the resistor R1 is connected to the input Vin, and the other end is connected to the output Vout. Diodes D1 to D4 are connected in series, and the cathode of diode D1 is connected to the anode of diode D2 and then connected to the output Vout. The cathode of diode D3 is connected to the anode of diode D4 and then grounded. The two ends of the resistor R2 are respectively connected to the common terminal of diodes D1 and D3, and the common terminal of diodes D2 and D4.

[0024] refer to Figure 3 Unlike the above embodiments, the resistor R2 is a variable resistor, and a diode D5 is connected between the resistor R2 and the common terminal of diodes D2 and D4. The cathode of the diode D5 is connected to the resistor R2, and the anode is connected to the common terminal of diodes D2 and D4.

[0025] It should be further noted that the voltage divider network resistors satisfy R1 / R2=N, and the compression ratio can be adjusted from 3:1 to 5:1 by adjusting the resistor ratio. For example, the voltage divider ratio is related to the compression ratio: when R1:R2=3:1, the compression ratio is fixed at 3:1 (if the input exceeds the threshold Vth, the output Vout=Vth+(Vin-Vth) / 3).

[0026] refer to Figure 4 In one embodiment of the present invention, R1 = 30kΩ and R2 = 10kΩ (1% accuracy) form a 3:1 voltage divider. The Schottky diode has a forward voltage drop of 0.2V and a reverse withstand voltage of ≥40V (e.g., 1N5819).

[0027] The working principle of the above embodiments is as follows: When the input level is less than 200mV, the Schottky diode cannot conduct, and the voltage limiter does not work; when the input level is greater than 200mV, the Schottky diode conducts, and the Schottky diode and the voltage dividing resistors R1 and R2 form a 3:1 voltage divider, thus realizing the function of the voltage limiter.

[0028] In one embodiment, the signal path is as follows: Audio signal source (host LineOut) → Limiter Vin terminal → Limiter Vout terminal → TDA7388 input terminal (chip pins 11 / 12 / 14 / 15) → Power amplifier output → Speaker. Grounding design: The negative terminal of the diode and R2 are grounded together to ensure a stable signal circuit.

[0029] Test conditions: Input a 1kHz sine wave and gradually increase the signal amplitude.

[0030] Expected results: 1. When Vin=200mV, Vout=200mV (voltage limit not triggered).

[0031] 2. When Vin = 300mV, Vout = 200mV + (300 - 200) / 3 ≈ 233mV (verified with a compression ratio of 3:1).

[0032] When Vin = 500mV, Vout = 200mV + (500 - 200) / 3 = 300mV, and the output is limited to a safe range.

[0033] This invention overcomes the cost and size limitations of traditional limiters, achieving efficient dynamic control through a simple combination of diodes and resistors, making it particularly suitable for cost-sensitive scenarios such as automotive audio. Its modular design supports flexible threshold adjustment, providing a cost-effective signal protection solution for fields such as car audio and consumer electronics.

[0034] The advantages of this invention are that it adapts to TDA7388 and TDA7851 power amplifier chips by connecting them in series at the signal input terminal to prevent output overload. It supports chips such as TDA7388 (pins 11 / 12 / 14 / 15) and TDA7851; the threshold voltage can be adjusted by changing the diode type or by designing a selector switch (200mV / 400mV / 600mV, etc.); the compression ratio can be flexibly adjusted by changing the resistor or by using an adjustable resistor; the low voltage drop (0.2V) of the Schottky diode avoids signal attenuation, and the measured total harmonic distortion (THD) is <0.1%.

[0035] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. An audio limiter based on a Schottky diode, characterized in that, Includes diode threshold units and voltage divider attenuation units, wherein: The diode threshold unit sets the voltage limit threshold by combining diode types; The voltage divider attenuation unit consists of an N:1 voltage divider network composed of two resistors to achieve compression ratio control; The diode threshold unit is composed of at least two diodes connected in reverse parallel or a bridge rectifier.

2. The audio limiter based on a Schottky diode according to claim 1, characterized in that, When two Schottky diodes are connected in reverse parallel, the threshold voltage is 200mV±20mV; When a bridge rectifier with four Schottky diodes is used, the threshold voltage is 400mV±30mV.

3. An audio limiter based on a Schottky diode according to claim 1, characterized in that, The voltage divider network resistors satisfy R1 / R2=N, and the compression ratio can be adjusted from 3:1 to 5:1 by adjusting the resistance ratio.

4. An audio limiter based on a Schottky diode according to claim 1, characterized in that, The Schottky diode anti-parallel circuit includes: input Vin, output Vout, resistor R1, resistor R2, and two diodes D1 and D2 connected in anti-parallel; wherein, One end of resistor R1 is connected to the input Vin, and the other end is connected to the output Vout. One end of resistor R2 is connected to the output Vout, and the other end is connected to the cathode of diode D1 and the anode of diode D2. The anode of diode D1 is connected to the cathode of diode D2 and grounded.

5. An audio limiter based on a Schottky diode according to claim 1, characterized in that, The Schottky diode bridge rectifier circuit includes: input Vin, output Vout, resistors R1 and R2, and four diodes D1, D2, D3, and D4 constituting the rectifier; wherein... One end of the resistor R1 is connected to the input Vin, and the other end is connected to the output Vout. Diodes D1 to D4 are connected in series, and the cathode of diode D1 is connected to the anode of diode D2 and then connected to the output Vout. The cathode of diode D3 is connected to the anode of diode D4 and then grounded. The two ends of the resistor R2 are respectively connected to the common terminal of diodes D1 and D3, and the common terminal of diodes D2 and D4.

6. An audio limiter based on a Schottky diode according to claim 5, characterized in that, The resistor R2 is a variable resistor, and a diode D5 is connected between the resistor R2 and the common terminal of diodes D2 and D4. The cathode of the diode D5 is connected to the resistor R2, and the anode is connected to the common terminal of diodes D2 and D4.

7. The application of the Schottky diode-based audio limiter according to any one of claims 1-6 in automotive audio, characterized in that, The adapter amplifier chip is connected in series at the signal input terminal to prevent output overload.

8. The application of the Schottky diode-based audio limiter according to claim 7 in automotive audio, characterized in that, The power amplifier chips include, but are not limited to, TDA7388 and TDA7851.

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