Direct-current signal elimination circuit in high-fidelity analog audio system
The parallel structure of the operational amplifier and the RC low-pass filter eliminate DC signals, which solves the audio signal distortion and impact sound problems caused by traditional capacitors, and achieves stable and pure sound quality of the high-fidelity audio system.
Patent Information
- Application Number
- CN202422125246.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-30
- Publication Date
- 2025-08-19
- Estimated Expiration
- 2034-08-30
AI Technical Summary
In high-fidelity analog audio systems, traditional capacitors eliminate DC signals and cause distortion of audio signal, frequency response changes and impact sound problems, affecting sound quality and acoustic equipment.
The first and second operational amplifiers are used to parallel structures and combined with an RC low-pass filter, the DC voltage is cancelled through the reverse input of the op amp to achieve accurate DC signal cancellation.
Maintain the integrity of the audio signal, avoid sound quality loss and impact sound, provide a pure and distorted audio experience, and protect acoustic equipment.
Smart Images
Figure CN223246695U_ABST
Abstract
Description
Technical Field
[0001] The present application belongs to the technical field of audio signal processing, and in particular relates to a DC signal elimination circuit in a high-fidelity analog audio system. Background Art
[0002] Maintaining signal purity and integrity is crucial in high-fidelity analog audio systems. However, unwanted DC signals often occur in circuits due to various reasons, including imperfect chip design or offset issues. Ideally, audio amplifiers and processors are designed to process only AC signals. However, imperfections in chip design can cause certain circuit components to output unwanted DC voltages. For example, improperly configured operational amplifiers can produce a DC offset at their output due to input bias current. Zero drift, also known as zero-point drift, occurs when electronic components such as sensors and amplifiers output a signal even when no input signal is present. This can be caused by factors such as temperature fluctuations and aging, resulting in an unwanted DC component in the output signal.
[0003] In existing technology, simply adding capacitors to circuits is a common method for eliminating DC signals. Capacitors can block DC signals from passing through, thereby separating pure AC signals. However, large-capacity capacitors can cause audible noise when charging, affecting sound quality and potentially damaging sensitive devices such as speakers. This is mainly manifested in:
[0004] 1. Audio parameter degradation: In traditional solutions, using coupling capacitors to isolate DC signals often results in changes in the frequency response and phase characteristics of the audio signal. This is because the capacitors present different impedances to signals of different frequencies, which may cause signal distortion or coloration.
[0005] 2. Impact sound problem: When a large-capacity DC-blocking capacitor is used in the circuit, the charging process of the capacitor at the moment the power is turned on may cause a large current impact, which manifests as an unpleasant popping or impact sound at the speaker terminal, affecting the user experience and may cause damage to the acoustic unit. Utility Model Content
[0006] In order to solve the above technical problems, the present application provides a DC signal elimination circuit in a high-fidelity analog audio system to eliminate or minimize the problems of audio signal distortion and coloration, impact sound, and damage to acoustic components that may be introduced due to the addition of capacitors or other components.
[0007] The DC signal elimination circuit in the high-fidelity analog audio system provided by this application mainly includes:
[0008] A first operational amplifier, having an inverting input terminal connected to the audio input interface, a non-inverting input terminal connected via a node of resistor R6, and an output terminal connected to the audio output interface, with a resistor R5 connected in parallel between the inverting input terminal and the output terminal of the first operational amplifier;
[0009] a second operational amplifier, having an inverting input terminal connected to the output terminal of the first operational amplifier, a non-inverting input terminal grounded, and an output terminal connected to the non-inverting input terminal of the first operational amplifier, and a capacitor C1 connected in parallel between the inverting input terminal and the output terminal of the second operational amplifier;
[0010] Wherein, an RC low-pass filter for filtering AC signals is provided between the output terminal of the first operational amplifier and the inverting input terminal of the second operational amplifier.
[0011] Preferably, the power pins of the first operational amplifier are connected to a positive power supply and a negative power supply respectively, so as to implement dual power supply.
[0012] Preferably, the positive power supply and the negative voltage of the first operational amplifier are connected to capacitors C3 and C4 respectively for filtering.
[0013] Preferably, the power pins of the second operational amplifier are connected to a positive power supply and a negative power supply respectively, so as to implement dual power supply.
[0014] Preferably, the RC low-pass filter includes a resistor R3 and a capacitor C2, the resistor R3 is connected in series between the output terminal of the first operational amplifier and the inverting input terminal of the second operational amplifier, one end of the capacitor C2 is connected to the resistor R3, and the other end is grounded.
[0015] This application can effectively avoid the deterioration of audio parameters caused by traditional DC-blocking capacitors, providing a purer and distortion-free sound quality experience. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 This is a circuit structure diagram of a preferred embodiment of a DC signal elimination circuit in a high-fidelity analog audio system of the present application. DETAILED DESCRIPTION
[0017] In order to make the purpose, technical solutions and advantages of the implementation of this application clearer, the technical solutions in the implementation of this application will be described in more detail below in conjunction with the drawings in the implementation of this application. In the drawings, the same or similar numbers throughout represent the same or similar elements or elements with the same or similar functions. The described implementation is a part of the implementation of this application, not all of the implementations. The implementation described below with reference to the drawings is exemplary and is intended to be used to explain this application, and should not be understood as a limitation on this application. Based on the implementation in this application, all other implementations obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The implementation of this application is described in detail below in conjunction with the drawings.
[0018] The present application provides a DC signal elimination circuit in a high-fidelity analog audio system, such as Figure 1 As shown, it mainly includes:
[0019] A first operational amplifier, having an inverting input terminal connected to the audio input interface, a non-inverting input terminal connected via a node of resistor R6, and an output terminal connected to the audio output interface, with a resistor R5 connected in parallel between the inverting input terminal and the output terminal of the first operational amplifier;
[0020] a second operational amplifier, having an inverting input terminal connected to the output terminal of the first operational amplifier, a non-inverting input terminal grounded, and an output terminal connected to the non-inverting input terminal of the first operational amplifier, and a capacitor C1 connected in parallel between the inverting input terminal and the output terminal of the second operational amplifier;
[0021] Wherein, an RC low-pass filter for filtering AC signals is provided between the output terminal of the first operational amplifier and the inverting input terminal of the second operational amplifier.
[0022] In some optional embodiments, the RC low-pass filter includes a resistor R3 and a capacitor C2, the resistor R3 is connected in series between the output end of the first operational amplifier and the inverting input end of the second operational amplifier, one end of the capacitor C2 is connected to the resistor R3, and the other end is grounded.
[0023] refer to Figure 1 The "DC+AC_IN" audio input interface carries a composite DC and AC signal and is connected to pin 2 (the inverting input) of the first operational amplifier U1-A. Resistors R5 and R6 connect to pins 2 and 3 of the first operational amplifier U1-A, respectively, serving as the inverting and non-inverting inputs.
[0024] After the composite signal flows into the inverting input terminal of the first operational amplifier U1-A, the output terminal of the first operational amplifier U1-A outputs a signal with DC and AC, and then passes through the low-pass filter composed of resistor R3 and capacitor C2, the AC signal is filtered out, and the remaining DC voltage reaches the inverting input terminal (pin 2) of the second operational amplifier U2-A through resistor R3 and resistor R2, and then the DC voltage is output from the output terminal 1 of the second operational amplifier U2-A, and the DC voltage is input to the non-inverting input terminal (pin 3) of the first operational amplifier U1-A through resistor R1.
[0025] The DC voltages at the non-inverting and inverting inputs of the first operational amplifier U1-A cancel each other out, causing the output of the first operational amplifier U1-A (pin 1) to output a smooth AC signal, which is then output through the audio output interface. This demonstrates that the present invention can convert a composite input DC and AC signal into a smoother AC output signal, achieving DC filtering.
[0026] This application achieves separation of the DC and AC components of the input signal by adding a carefully designed RC circuit. This design not only ensures the integrity of the audio signal, but also avoids the sound quality loss and audible noise issues that may be caused by traditional capacitive coupling.
[0027] This application uses the op amp's inverting input to receive a signal processed by an RC circuit, and uses its output to offset the DC voltage at the input of the preceding op amp, effectively eliminating the impact of the DC signal on subsequent circuits. This design simplifies the circuit structure and improves system stability and ease of use.
[0028] This application achieves accurate and efficient DC cancellation by adding the DC voltage output by the RC circuit to the op amp, and then the op amp output reverse voltage and the DC voltage at the input of the previous op amp cancel each other out. This mechanism ensures that the output signal contains only the required AC component, improving the fidelity of the audio system.
[0029] In some optional implementations, power pins of the first operational amplifier are respectively connected to a positive power supply and a negative power supply to implement dual power supply.
[0030] In some optional implementations, the positive power supply and negative voltage of the first operational amplifier are connected to capacitor C3 and capacitor C4 respectively for filtering.
[0031] In some optional implementations, power pins of the second operational amplifier are respectively connected to a positive power supply and a negative power supply to implement dual power supply.
[0032] In the above embodiment, the first operational amplifier U1-A and the second operational amplifier U2-A have a ±V dual power supply system, providing a positive voltage +V and a negative voltage -V, respectively. Capacitors C3 (1uF) and C4 (1uF) are connected in parallel for filtering and stabilization.
[0033] This application has the following advantages:
[0034] Through precise DC cancellation, this application effectively avoids the degradation of audio parameters caused by traditional DC-blocking capacitors. This means that the frequency response and phase characteristics of the audio signal are maintained as it passes through the circuit, providing a purer, distortion-free sound quality experience.
[0035] Reduced damage to acoustic units: By eliminating the power-on impact sound, this application not only improves the user's listening experience but also reduces potential damage to acoustic units such as speakers. This improvement is crucial for maintaining the long-term performance of audio equipment.
[0036] Improve system stability and ease of use: The circuit design of this application does not require frequent adjustments and maintenance, ensuring long-term stable operation of the system. At the same time, its simple design also reduces the difficulty of user operation, making it easy for non-professionals to use and maintain.
[0037] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.
Claims
1. A DC signal elimination circuit in a high-fidelity analog audio system, characterized in that: include: A first operational amplifier, having an inverting input terminal connected to the audio input interface, a non-inverting input terminal connected via a node of resistor R6, and an output terminal connected to the audio output interface, with a resistor R5 connected in parallel between the inverting input terminal and the output terminal of the first operational amplifier; a second operational amplifier, having an inverting input terminal connected to the output terminal of the first operational amplifier, a non-inverting input terminal grounded, and an output terminal connected to the non-inverting input terminal of the first operational amplifier, and a capacitor C1 connected in parallel between the inverting input terminal and the output terminal of the second operational amplifier; Wherein, an RC low-pass filter for filtering AC signals is provided between the output terminal of the first operational amplifier and the inverting input terminal of the second operational amplifier.
2. The DC signal elimination circuit in the high-fidelity analog audio system according to claim 1, wherein: The power pins of the first operational amplifier are respectively connected to a positive power supply and a negative power supply for dual power supply.
3. The DC signal elimination circuit in the high-fidelity analog audio system according to claim 2, wherein: The positive power supply and negative voltage of the first operational amplifier are connected to capacitor C3 and capacitor C4 respectively for filtering.
4. The DC signal elimination circuit in the high-fidelity analog audio system according to claim 1, wherein: The power pins of the second operational amplifier are respectively connected to a positive power supply and a negative power supply to implement dual power supply.
5. The DC signal elimination circuit in the high-fidelity analog audio system according to claim 1, wherein: The RC low-pass filter includes a resistor R3 and a capacitor C2. The resistor R3 is connected in series between the output terminal of the first operational amplifier and the inverting input terminal of the second operational amplifier. One end of the capacitor C2 is connected to the resistor R3 and the other end is grounded.