Two-stage D-class power amplifier circuit on computer mainboard
By introducing the audio power amplifier NS4258 on the computer motherboard and connecting resistors and capacitors in series with the sound card SN6140, combined with a filtering circuit, the background noise problem caused by the internal Class D amplifier of the sound card is solved, and compatibility with higher-power speakers and noise reduction are achieved.
Patent Information
- Application Number
- CN202422511960.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-17
- Publication Date
- 2025-09-12
- Estimated Expiration
- 2034-10-17
AI Technical Summary
In existing computer motherboard designs, the Class D amplifier inside the sound card inevitably has background noise, which causes persistent background noise issues in the speakers and cannot meet the needs of new customers for higher-power speakers.
An audio power amplifier NS4258 is introduced on the computer motherboard, and connected to the audio signal output port of the sound card SN6140 through a series resistor and capacitor to limit the output power of the internal amplifier of the sound card, and a filtering circuit is combined to reduce noise.
This effectively reduces the noise floor of the secondary Class-D amplifier, meeting new customer demands for higher-power speakers while avoiding a significant increase in motherboard design and production costs.
Smart Images
Figure CN223334650U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of electronic computers, in particular to a secondary class D power amplifier circuit on a computer mainboard. Background Art
[0002] A power amplifier, also known as a power amplifier, is a basic device in an audio system. Its function is to amplify weak signals from the sound source or preamplifier, driving the speakers to produce sound.
[0003] Class D amplifiers refer to Class D audio power amplifiers (sometimes also called digital amplifiers). Compared to conventional linear Class AB amplifier circuits, Class D amplifiers feature high efficiency and compact size. Class D amplifiers operate in a switching mode in which the amplifying elements operate in a switching state. When no signal is input, the amplifier is in a cutoff state and consumes no power. During operation, the input signal drives the transistors into saturation, acting as a closed switch, directly connecting the power supply to the load. Ideal transistors consume no power because they have no saturation voltage drop. However, in reality, transistors always have a small saturation voltage drop, which consumes some energy. This power consumption depends solely on the characteristics of the transistors and is independent of the signal output, making it particularly advantageous in ultra-high-power applications.
[0004] When it comes to computer motherboard design, the current common solution involves connecting an amplifier to a port on the sound card that doesn't already have one. This approach is suitable for the initial stages of a motherboard design. For machines with mature motherboard designs that already utilize the sound card's internal amplifier, for example, if a design for an existing customer uses the sound card's built-in amplifier to support two-wire 2.2W speakers, and a new customer requests two-wire 3.3W speakers, the existing motherboard design won't meet the new customer's amplifier requirements. Considering the cost and resource constraints of computer motherboards, when developing a targeted design based on the existing motherboard design, one might consider adding an external amplifier circuit to the sound card's built-in 2.2W amplifier. However, the Class D amplifiers in commonly used sound cards inevitably have background noise, which is transmitted to the external amplifier, resulting in a persistent background noise in the speakers. The applicant encountered this problem when designing a motherboard using the SN6140 sound card, and a solution was urgently needed. Summary of the Invention
[0005] Therefore, the purpose of the present invention is to provide a two-stage Class D power amplifier circuit on a computer motherboard to reduce the background noise of the two-stage Class D power amplifier.
[0006] To achieve the above-mentioned objectives, the present invention provides a secondary Class D power amplifier circuit on a computer motherboard, comprising: a sound card SN6140, and an audio power amplifier NS4258; the audio signal output port of the sound card SN6140 is electrically connected to the corresponding audio signal input port of the audio power amplifier NS4258 via a resistor and a capacitor connected in series, the resistance value of the resistor is 50 to 100 kilo-ohms, and the internal power amplifier output power of the sound card SN6140 is limited to 0.70 to 1.2 watts.
[0007] Wherein, the capacitance value of the capacitor is 56 nanofarads.
[0008] The audio power amplifier NS4258 is electrically connected to a 5V power supply on the mainboard.
[0009] The resistance of the resistor is 50 kilo-ohms, and the output power of the internal amplifier of the sound card SN6140 is limited to 0.70 watts.
[0010] The resistance of the resistor is 100 kilo-ohms, and the output power of the internal amplifier of the sound card SN6140 is limited to 1.20 watts.
[0011] The resistance of the resistor is 82 kilo-ohms, and the output power of the internal amplifier of the sound card SN6140 is limited to 0.75 watts.
[0012] The audio signal output port of the sound card SN6140 is also electrically connected to a filter circuit to filter the audio signal output.
[0013] In summary, the secondary Class D power amplifier circuit on the computer motherboard of the present invention can reduce the background noise of the secondary Class D power amplifier. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The following detailed description of the specific embodiments of the present invention in conjunction with the accompanying drawings will make the technical solutions and other beneficial effects of the present invention apparent.
[0015] Figure 1 This is a partial port wiring diagram of a sound card SN6140 in a preferred embodiment of a secondary Class D power amplifier circuit on a computer motherboard of the utility model;
[0016] Figure 2 This is a schematic diagram of the port wiring of the audio power amplifier NS4258 in a preferred embodiment of the secondary Class D power amplifier circuit on the computer motherboard of the utility model. DETAILED DESCRIPTION
[0017] See also Figure 1 and Figure 2 , Figure 1This is a partial port wiring diagram of a sound card SN6140 in a preferred embodiment of a secondary Class D power amplifier circuit on a computer motherboard of the utility model. Figure 2 For this purpose, the port wiring diagram of the audio power amplifier NS4258 in the preferred embodiment is as follows: Figure 1 and Figure 2 The parts related to the key points of the technical solution of this utility model are marked with boxes.
[0018] In the applicant's original computer motherboard design project, the power amplifier of the SN6140 sound card was used. However, in the subsequent design for new customers, it is necessary to introduce an audio power amplifier based on the original circuit. Since the Class D power amplifier inside the sound card inevitably has background noise and it will be transmitted to the external power amplifier, if the conventional design is continued, the speaker will have continuous background noise.
[0019] The secondary class D power amplifier circuit of this preferred embodiment mainly includes a sound card SN6140 with an internal power amplifier and an audio power amplifier NS4258 for connecting to a speaker; Figure 1 and Figure 2 As shown, according to the left and right channels, positive and negative signals, the audio signal output port of the sound card SN6140 is electrically connected to the corresponding audio signal input port of the audio power amplifier NS4258 via series resistors (PR1, PR2, PR3, PR4) and capacitors (C21, C22, C30, C31), the resistance of the resistor is 82 kilo-ohms, and the internal power amplifier output power of the sound card SN6140 is limited to 0.75 watts; the capacitance value of the capacitor is 56 nanofarads; the audio power amplifier NS4258 is electrically connected to the 5-volt power supply P5V on the motherboard.
[0020] In this preferred embodiment, the applicant uses the sound card SN6140 + amplifier NS4258 to meet the needs of customers. The power of the internal amplifier of the sound card SN6140 can generally be adjusted through the firmware. The applicant limits the output power of the amplifier through the firmware and adjusts the resistance of the signal line to the secondary amplifier. The two cooperate with each other, and through continuous experiments, the best configuration that meets the customer's power requirements is tested. Specifically, by setting the SN6140 amplifier to 0.75w (default 2.2w) and setting the resistance on the series signal line to 82kΩ, the background noise will be greatly reduced. At the same time, since the technical solution of the utility model is implemented by adding simple components and circuit structures on the basis of the original motherboard circuit, it will not significantly increase the design and production costs of the motherboard.
[0021] In this preferred embodiment, the audio signal output ports 12, 14, 15 and 17 of the sound card SN6140 are also electrically connected to the filter circuit to filter the audio signal output. Each audio signal output port 12, 14, 15 and 17 is grounded via a 15 ohm resistor and a 220pF capacitor connected in series for filtering, thereby further improving the audio signal quality and reducing noise.
[0022] When implementing the technical solution of the present invention, the resistance value of the resistor connected between the audio signal output port of the sound card SN6140 and the corresponding audio signal input port of the audio power amplifier NS4258 can also be selected within the range of 50 to 100 kilo-ohms. At this time, the output power of the internal power amplifier of the sound card SN6140 is limited to 0.70 to 1.2 watts; for example, the resistance value of the resistor is 50 kilo-ohms, and the output power of the internal power amplifier of the sound card SN6140 is limited to 0.70 watts; or, the resistance value of the resistor is 100 kilo-ohms, and the output power of the internal power amplifier of the sound card SN6140 is limited to 1.20 watts, which can also achieve a better noise reduction effect.
[0023] In summary, the secondary Class D power amplifier circuit on the computer motherboard of the present invention can reduce the background noise of the secondary Class D power amplifier.
[0024] As described above, for ordinary technicians in this field, various other corresponding changes and modifications can be made according to the technical solution and technical concept of the utility model, and all these changes and modifications should fall within the scope of protection of the claims attached to the utility model.
Claims
1. A secondary Class D power amplifier circuit on a computer motherboard, characterized in that: include: A sound card SN6140 and an audio power amplifier NS4258; the audio signal output port of the sound card SN6140 is electrically connected to the corresponding audio signal input port of the audio power amplifier NS4258 via a resistor and a capacitor connected in series, the resistance of the resistor is 50 to 100 kilo-ohms, and the output power of the internal power amplifier of the sound card SN6140 is limited to 0.70 to 1.2 watts.
2. The secondary Class D power amplifier circuit on a computer motherboard as claimed in claim 1, characterized in that: The capacitance value of the capacitor is 56 nanofarads.
3. The secondary Class D power amplifier circuit on a computer motherboard as claimed in claim 1, characterized in that: The audio power amplifier NS4258 is electrically connected to a 5V power supply on the mainboard.
4. The secondary Class D power amplifier circuit on a computer motherboard as claimed in claim 1, characterized in that: The resistance of the resistor is 50 kilo-ohms, and the output power of the internal amplifier of the sound card SN6140 is limited to 0.70 watts.
5. The secondary Class D power amplifier circuit on a computer motherboard as claimed in claim 1, characterized in that: The resistance of the resistor is 100 kilo-ohms, and the output power of the internal amplifier of the sound card SN6140 is limited to 1.20 watts.
6. The secondary Class D power amplifier circuit on a computer motherboard as claimed in claim 1, characterized in that: The resistance of the resistor is 82 kilo-ohms, and the output power of the internal amplifier of the sound card SN6140 is limited to 0.75 watts.
7. The secondary Class D power amplifier circuit on a computer motherboard as claimed in claim 1, characterized in that: The audio signal output port of the sound card SN6140 is also electrically connected to a filter circuit to filter the audio signal output.