Audio drive circuit

Abstract

The utility model relates to an audio drive circuit, which comprises a Type-C USB (Universal Serial Bus) interface, a planar magnetic array unit loudspeaker, a USB sound card PCM2704 and an AB type operational amplifier chip 8002A, wherein the Type-C USB interface is used for being connected with mobile equipment supporting a USB1.1 / 2.0 protocol; a mobile device connected to a USB interface provides a 5V standard voltage for the audio drive circuit and inputs the 5V standard voltage to the USB sound card PCM2704 and the AB type operational amplifier chip 8002A. An audio signal sent by the mobile device is transmitted to a data I / O pin of the USB sound card PCM2704 through a data I / O pin of the USB interface; an audio signal processed by the USB sound card PCM2704 is transmitted to an input pin of an AB type operational amplifier chip 8002A through an output pin of the USB sound card PCM2704; and the audio signal processed by the class AB operational amplifier chip 8002A is output to a planar magnetic array unit loudspeaker connected to an output pin of the class AB operational amplifier chip 8002A.

Description

Technical Field

[0001] This utility model relates to the field of electronic technology, and in particular to an audio driving circuit. Background Technology

[0002] Traditional electrodynamic loudspeakers typically consist of a magnet, soft iron, a voice coil, a diaphragm, and a mounting mechanism. When a coil connected to the diaphragm is placed in a constant magnetic field and an audio current is passed through it, the coil moves within the magnetic field in response to changes in the audio current, causing the diaphragm to vibrate and produce sound. The vibration of the voice coil is transmitted to the diaphragm; the area where the voice coil is attached vibrates first, then the vibration spreads towards the center and edges of the diaphragm. This transmission process involves asynchronous vibration, known as split vibration, which causes significant harmonic distortion. Because traditional electrodynamic loudspeakers have low impedance, their power requirements generally exceed 3W. Therefore, they require high-power audio operational amplifiers, and precise power matching is crucial to prevent damage.

[0003] Currently, the mainstream audio driver unit market mainly consists of cone-shaped audio units, racetrack-shaped audio units, and dynamic drivers. Significant progress has been made in new speaker units (electrostatic speakers, MEMS speakers, armature speakers, and planar magnetic array speakers), with planar magnetic array units being widely used in the headphone field. However, no related solutions have yet emerged in the portable speaker field.

[0004] See Figure 1 This is a schematic diagram comparing the sound production of an electrodynamic loudspeaker and a planar magnetic array loudspeaker. Figure 1 The left side shows an electrodynamic loudspeaker, and the right side shows a planar magnetic array loudspeaker. Planar magnetic array units generate sound by regulating the current flowing through a thin film suspended between magnets, which possess equal magnetic forces. The magnets are placed on both sides of an electroactive diaphragm material. When an current is applied, the film becomes charged, generating a magnetic field. When the magnets on both sides of the diaphragm react with this magnetic field, it causes the diaphragm to move, thus generating sound waves. Due to the isodynamic field, these movements are constant, continuous, and uniformly distributed across the entire diaphragm, ensuring balanced sound reproduction. Planar magnetic array units therefore possess unparalleled advantages in distortion and sound field compared to other units. However, the high cost of most ultra-thin diaphragm materials and the excessively thick FPC films on the market (requiring high power and resulting in low sound pressure levels) have hindered their market penetration compared to dynamic drivers.

[0005] There is an urgent need to develop an audio driver circuit to solve the problem of driving planar magnetic array unit speakers via USB bus. Summary of the Invention

[0006] Therefore, the purpose of this utility model is to provide an audio driving circuit that solves the problem of driving a planar magnetic array unit speaker via a USB bus.

[0007] To achieve the above objectives, this utility model provides an audio driver circuit, including a Type-C USB interface for connecting a mobile device supporting the USB 1.1 / 2.0 protocol, a planar magnetic array unit speaker, a USB sound card PCM2704, and an AB class operational amplifier chip 8002A; the mobile device connected to the USB interface provides a 5V standard voltage to the audio driver circuit and inputs to the USB sound card PCM2704 and the AB class operational amplifier chip 8002A; the audio signal sent by the mobile device is transmitted to the data I / O pin of the USB sound card PCM2704 via the data I / O pin of the USB interface; the audio signal processed by the USB sound card PCM2704 is transmitted to the input pin of the AB class operational amplifier chip 8002A via the output pin of the USB sound card PCM2704; the audio signal processed by the AB class operational amplifier chip 8002A is output to the planar magnetic array unit speaker connected to the output pin of the AB class operational amplifier chip 8002A.

[0008] The impedance of the planar magnetic array unit loudspeaker is 26 ohms.

[0009] The planar magnetic array unit loudspeaker is a printed circuit liquid biofilm planar magnetic array unit loudspeaker.

[0010] The printed circuit liquid biofilm planar magnetic array unit speaker is the KYLIN50 speaker.

[0011] The planar magnetic array unit speaker is assembled in a portable speaker.

[0012] The power pin and ground pin of the USB interface are connected to the corresponding pins of the chip B0505S-1WR3, and the output pin of the chip B0505S-1WR3 outputs a standard 5V voltage.

[0013] In summary, the audio driving circuit of this invention can drive a planar magnetic array unit speaker based on a USB bus, providing a stable power driving unit and clear audio with low distortion while being compatible with mainstream mobile devices on the market. Attached Figure Description

[0014] The technical solution and other beneficial effects of this utility model will become apparent from the following detailed description of specific embodiments, in conjunction with the accompanying drawings.

[0015] Figure 1 A schematic diagram comparing the sound production of an electrodynamic loudspeaker and a planar magnetic array loudspeaker;

[0016] Figure 2 This is a circuit block diagram of the audio driver circuit of this utility model;

[0017] Figure 3 This is a schematic diagram of the USB sound card PCM2704 circuit in a preferred embodiment of the audio driver circuit of this utility model;

[0018] Figure 4 This is a schematic diagram of the USB interface circuit in a preferred embodiment of the audio driver circuit of this utility model;

[0019] Figure 5 This is a schematic diagram of the left speaker circuit in a preferred embodiment of the audio driving circuit of this utility model;

[0020] Figure 6 This is a schematic diagram of the right speaker circuit in a preferred embodiment of the audio driver circuit of this utility model. Detailed Implementation

[0021] See Figure 2 This is a circuit block diagram of the audio driver circuit of this utility model, which can be combined with... Figures 3 to 6 To understand the design of this utility model, Figure 3 This is a schematic diagram of the USB sound card PCM2704 circuit in a preferred embodiment of the audio driver circuit of this utility model. Figure 4 Therefore, a schematic diagram of the USB interface circuit in the preferred embodiment is provided. Figure 5 This is a schematic diagram of the left speaker circuit in a preferred embodiment. Figure 6 Therefore, a schematic diagram of the right speaker circuit in a preferred embodiment is shown.

[0022] In this preferred embodiment, the audio driver circuit of this invention includes a Type-C port for connecting to mobile devices supporting the USB 1.1 / 2.0 protocol. The system includes a USB interface, two planar magnetic array unit speakers (L and R) on the left and right sides, a PCM2704 USB sound card, and an 8002A Class AB operational amplifier chip. The mobile device connected to the USB interface provides a 5V standard voltage to the audio driver circuit via the VBUS pin of the USB interface, and inputs this voltage to the corresponding pins of the PCM2704 and 8002A Class AB operational amplifier chip as power for the driver chips. The audio signal sent by the mobile device is transmitted to the data I / O pins D+ and D- of the PCM2704 USB sound card via the data I / O pins DP1, DN1, DP2, and DN2 of the USB interface. The audio signal processed by the PCM2704 USB sound card is transmitted to the input pins +IN and -IN of the 8002A Class AB operational amplifier chip via the output pins VOUTL and VOUTR of the PCM2704 USB sound card. The audio signal processed by the 8002A Class AB operational amplifier chip is output to the planar magnetic array unit speakers connected to the output pins of the 8002A Class AB operational amplifier chip.

[0023] In this preferred embodiment, the audio unit employs a printed circuit liquid biofilm planar magnetic array unit speaker, specifically taking the KYLIN50 series unit as an example. The parameters are as follows: size, 50*50*10mm; impedance, 26Ω; sensitivity: 100dB at 1kHz; diaphragm, 2µm liquid biofilm. This preferred embodiment utilizes a planar magnetic array unit speaker, which reduces the size of portable speakers. Compared to traditional electrodynamic speakers, it employs a completely different structural design, consisting of a flexible diaphragm printed with a serpentine circuit and permanent magnets that repel each other on both sides and adjacent to each other. Audio signals are transmitted into the flexible circuit diaphragm and converted into electromagnetic signals. The diaphragm vibrates in the magnetic field of the permanent magnets, thus producing sound. Because the coils are evenly distributed on the diaphragm, the entire diaphragm vibrates, resulting in minimal segmented vibration, low distortion, and a more natural tone compared to traditional electrodynamic speakers. The main diaphragm uses a liquid biofilm, which significantly reduces the thickness compared to a typical FPC flexible circuit board to 2µm, resulting in higher mechanical vibration efficiency. Nickel-plated N55 neodymium magnets were selected, which are easier to use to increase the upper limit of sound pressure level compared to ordinary ferrite magnets. At the same time, the circuit layout was improved, the coil impedance was increased to 26Ω, the sensitivity was increased to 100dB, and the driving requirements were reduced. Due to the advantages of the planar magnetic array, the overall unit thickness is 50% thinner than that of a traditional speaker of the same size.

[0024] This invention proposes a USB bus audio driving scheme based on a planar magnetic array unit with printed circuit diaphragm sound generation. It uses printed circuit and liquid biofilm, which is easy to drive sound generation and reduces costs. At the same time, it uses AB class operational amplifier chip 8002A + USB sound card PCM2704 to achieve USB bus driving and enhance multi-device compatibility.

[0025] The audio amplification system of the utility model's driving circuit consists of a driverless USB sound card PCM2704 and a low-power Class AB operational amplifier chip 8002A. Furthermore, a chip B0505S-1WR3 is used to isolate the 5V standard voltage. (See also...) Figure 4 The power pin VBUS and ground pin GND of the USB interface are connected to the corresponding pins +VIN and GND of the chip B0505S-1WR3, respectively. The isolated 5V standard voltage is output by the output pins +VO and -VO of the chip B0505S-1WR3.

[0026] The USB sound card portion of this invention uses the PCM2704 USB sound card solution. The PCM2704 USB sound card is a 98dB SNR stereo USB 2.0 FS DAC with linear output and S / PDIF output, bus-powered / self-powered, enabling driverless compatibility with most mobile devices and transmission of clear audio signals.

[0027] The audio amplification section uses the 8002A BTL bridge-connected Class AB op-amp chip solution to achieve a stable 3W output under 5V conditions, with THD+N<=10%, and minimizes distortion.

[0028] The working process of the audio driver circuit of this utility model is as follows:

[0029] 1. Bus power supply identification stage: When a mobile device supporting the USB 1.1 / 2.0 protocol is connected to the USB interface, the mobile device provides a standard 5V voltage to enable the driver system to work normally and identifies the system as an audio DAC module. After successful identification, the system starts audio decoding. The PCM2704 chip of the USB sound card itself has an audio DAC protocol and is highly compatible with multiple devices.

[0030] 2. USB sound card decoding stage: The mobile device sends an audio signal, which is transmitted to the data terminal of the USB sound card PCM2704 through the USB data I / O pin. The PCM2704 performs high-precision signal analysis and digital decoding processing, outputting a clearer audio signal, which is then transmitted to the audio operational amplifier module for amplification.

[0031] 3. Audio Amplification Stage: The processed audio signal is transmitted to the 8002A Class AB op-amp chip, powered by VBUS, providing low-noise audio signal amplification before being transmitted to the speaker unit. Compared to Class D op-amps, Class AB op-amps offer superior THD+N and PSRR performance with extremely low noise, exhibiting powerful audio characteristics at the same 3W power level.

[0032] 4. Vibration and Sound Generation Stage: The final audio signal processed by the audio system is transmitted to the diaphragm serpentine circuit inside the planar magnetic array unit speaker. The signal generates electromagnetic waves through this circuit. Due to mutual repulsion within the magnetic field of the array magnets, the change in the audio signal causes variable mechanical vibration of the diaphragm. This mechanical vibration is ultimately converted into a sound field and diffuses outward, forming external sound.

[0033] In summary, the audio driving circuit of this invention can drive a planar magnetic array unit speaker based on a USB bus, providing a stable power driving unit and clear audio with low distortion while being compatible with mainstream mobile devices on the market. When used in portable speakers, it can reduce the size of the speaker while achieving excellent sound effects and strong compatibility with mobile devices.

[0034] As described above, those skilled in the art can make various other corresponding changes and modifications based on the technical solution and concept of this utility model, and all such changes and modifications should fall within the protection scope of the appended claims of this utility model.

Claims

1. An audio driving circuit, characterized in that: It includes a Type-C USB interface for connecting a mobile device supporting the USB1.1 / 2.0 protocol, a planar magnetic array unit speaker, a USB sound card PCM2704, and a class AB operational amplifier chip 8002A; the mobile device connected to the USB interface provides a 5V standard voltage to an audio driving circuit and inputs the USB sound card PCM2704 and the class AB operational amplifier chip 8002A; the audio signal sent by the mobile device is transmitted to the data I / O pin of the USB sound card PCM2704 via the data I / O pin of the USB interface; the audio signal processed by the USB sound card PCM2704 is transmitted to the input pin of the class AB operational amplifier chip 8002A via the output pin of the USB sound card PCM2704; the audio signal processed by the class AB operational amplifier chip 8002A is output to the planar magnetic array unit speaker connected to the output pin of the class AB operational amplifier chip 8002A.

2. The audio driving circuit according to claim 1, characterized in that: The impedance of the planar magnetic array unit speaker is 26 ohms.

3. The audio driving circuit according to claim 1, characterized in that: The planar magnetic array unit loudspeaker is a printed circuit liquid biofilm planar magnetic array unit loudspeaker.

4. The audio driving circuit according to claim 3, characterized in that: The printed circuit liquid biofilm planar magnetic array unit speaker is a KYLIN50 speaker.

5. The audio driving circuit according to claim 1, characterized in that: The planar magnetic array unit loudspeaker is assembled in a portable sound box.

6. The audio driving circuit according to claim 1, characterized in that: The power pin and the ground pin of the USB interface are respectively connected to the corresponding pins of the chip B0505S-1WR3, and the output pin of the chip B0505S-1WR3 outputs a 5V standard voltage.

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