CN214098404U - External sound card - Google Patents

Abstract

The utility model provides an external sound card, including interface, power management module, battery, level conversion module, application circuit and the live equipment interface that charges, still include direct current isolation power module, direct current isolation power module sets up charge the interface with between the power management module, perhaps set up power management module with between the level conversion module, direct current isolation power module is including the first converting circuit, transformer and the second converting circuit who connects gradually, and first converting circuit is used for converting the direct current of input into the alternating current and exports to the primary side of transformer, and second converting circuit is used for receiving the alternating current of the secondary output of transformer and converts it into direct current output. The direct current isolation power supply module isolates the reference ground of the charging loop and the reference ground of the audio signal loop from each other, and therefore the direct broadcast effect is guaranteed.

Description

External sound card

Technical Field

The utility model relates to a sound card technical field, especially an external sound card.

Background

With the popularization of the live broadcast industry, more and more anchor broadcasters select simple live broadcast scenes carried by mobile terminals such as mobile phones and external sound cards to realize live broadcast. In the process of live broadcasting by a main broadcast, the situation that the electric quantity of a mobile phone and an external sound card is insufficient sometimes occurs.

When a multi-port USB charger or a computer is adopted to charge the mobile phone and the external sound card at the same time, obvious noise is generated, and the live broadcast effect is seriously influenced.

SUMMERY OF THE UTILITY MODEL

Based on above-mentioned current situation, the utility model discloses a main aim at provides an external sound card to solve the noise problem of charging that exists among the prior art.

In order to achieve the above object, the utility model adopts the following technical scheme:

an external sound card comprises a charging interface, a power management module, a battery, a level conversion module, an application circuit and a live broadcast equipment interface, wherein the charging interface and the battery are connected with the power management module, the power management module is used for controlling the battery charging process of the external sound card and the power supply process of the application circuit, the level conversion module is used for carrying out level conversion on the current output by the power management module and then transmitting the current to the application circuit, the live broadcast equipment interface is connected with the application circuit,

the external sound card also comprises a direct current isolation power supply module which is arranged between the charging interface and the power supply management module or between the power supply management module and the level conversion module,

the direct-current isolation power supply module comprises a first conversion circuit, a transformer and a second conversion circuit which are sequentially connected, wherein the first conversion circuit is used for converting input direct current into alternating current and outputting the alternating current to the primary side of the transformer, and the second conversion circuit is used for receiving the alternating current output by the secondary side of the transformer and converting the alternating current into direct current to be output.

Preferably, the power management module comprises a power supply management circuit and a charging management circuit,

the input end of the charging management circuit is connected with the charging interface, and the output end of the charging management circuit is connected with the battery;

the first input end of the power supply management circuit is connected with the charging interface, the second input end of the power supply management circuit is connected with the battery, and the output end of the power supply management circuit is connected with the level conversion module;

the direct current isolation power supply module is arranged between the output end of the power supply management circuit and the level conversion module.

Preferably, the power management module comprises a power supply management circuit and a charging management circuit,

the input end of the charging management circuit is connected with the charging interface, and the output end of the charging management circuit is connected with the battery;

the input end of the power supply management circuit is connected with the battery, and the output end of the power supply management circuit is connected with the level conversion module;

the direct current isolation power supply module is arranged between the output end of the power supply management circuit and the level conversion module, or between the charging management circuit and the battery, or between the battery and the power supply management circuit.

Preferably, the transformer includes more than two common mode inductors, primary windings of the more than two common mode inductors are arranged in parallel, and secondary windings of the more than two common mode inductors are arranged in series.

Preferably, the first conversion circuit comprises a control chip, a PMOS transistor and an NMOS transistor, and the control chip is configured to control on/off of the PMOS transistor and the NMOS transistor to generate a PWM signal wave with a set duty ratio.

Preferably, the second conversion circuit includes a first diode, a second diode, a third diode and a fourth diode, a negative end of the first diode and a positive end of the second diode are connected to one end of the secondary winding of the transformer, a negative end of the third diode and a positive end of the fourth diode are connected to the other end of the secondary winding of the transformer, a positive end of the first diode and a positive end of the third diode are connected to the ground, a negative end of the second diode and a negative end of the fourth diode are connected to the output end, and a third resistor, a fourth capacitor and a fifth capacitor are connected in parallel between the output end and the ground.

Preferably, a charging end and a data transmission end are integrated in the charging interface, the charging end is connected with the power management module, the data transmission end is connected with the application circuit, and a data isolation module is arranged between the data transmission end and the application circuit.

Preferably, the data isolation module includes an opto-coupler.

Preferably, the sound card further comprises an accompaniment device interface, and the accompaniment device interface is connected with the application circuit.

Preferably, the transformer includes three common mode inductors, primary windings of the three common mode inductors are connected in parallel, and secondary windings of the three common mode inductors are connected in series;

first converting circuit, second converting circuit and three common mode inductance is integrated on a circuit board, the circuit board is the rectangle, wherein two common mode inductance sets up side by side a long avris of circuit board, another one common mode inductance sets up a short avris of circuit board, first converting circuit with second converting circuit sets up three common mode inductance and in another long avris, another short avris of circuit board enclosed the space.

The utility model provides a be provided with direct current isolation power module in the external sound card, direct current isolation power module sets up between the interface and the power management module that charge of external sound card, perhaps set up between power management module and level conversion module, so, direct current isolation power module separates charging circuit's the ground of reference and audio signal return circuit's ground of reference each other, avoid charging circuit's ground of reference and audio signal return circuit's ground of reference to form the loop, lead to sound card audio signal return circuit's ground of reference to appear additionally undulant and appear obvious electric current sound in the audio signal that live cell-phone received, guarantee live effect.

Other advantages of the present invention will be described in the detailed description, and those skilled in the art can understand the technical advantages brought by the technical features and technical solutions through the descriptions of the technical features and the technical solutions.

Drawings

Preferred embodiments according to the present invention will be described below with reference to the accompanying drawings. In the figure:

fig. 1 is a schematic view of a scenario in which a live phone, an external sound card, and an accompanying phone are used simultaneously, and a multi-port USB charger is used to charge the live phone and the external sound card simultaneously;

FIG. 2 is a current walk diagram for the scenario of FIG. 1;

fig. 3 is a current trend chart when the direct broadcasting mobile phone, the external sound card and the computer are used simultaneously and the direct broadcasting mobile phone and the external sound card are charged simultaneously by the computer;

fig. 4 is a circuit diagram of an external sound card according to a first embodiment of the present invention;

fig. 5 is a circuit diagram of an external sound card according to a second embodiment of the present invention;

fig. 6 is a circuit diagram of an external sound card according to a third embodiment of the present invention;

fig. 7 is a circuit diagram of a dc isolation power module of an external sound card according to an embodiment of the present invention;

fig. 8 is a schematic layout view of a dc isolation power module of an external sound card according to an embodiment of the present invention on a circuit board;

fig. 9 is a current walking diagram when the live phone, the external sound card, and the computer are used simultaneously, the computer is used to charge the live phone and the external sound card simultaneously, and audio data is transmitted to the external sound card;

fig. 10 is a circuit diagram of an external sound card according to a fourth embodiment of the present invention.

In the figure:

1. an external sound card; 2. live broadcasting a mobile phone; 3. an accompaniment mobile phone; 4. a charger;

10. a charging interface; 20. a power management module; 21. a power supply management circuit; 22. a charging management circuit; 30. a battery; 40. a level conversion module; 50. an application circuit; 60. a live device interface; 70. an accompaniment device interface; 80. a DC isolation power supply module; 81. a first conversion circuit; 82. a transformer; 821. a common mode inductor; 83. a second conversion circuit; 90. a circuit board; 110. and a data isolation module.

Detailed Description

The present invention will be described below based on examples, but the present invention is not limited to only these examples. In the following detailed description of the present invention, certain specific details are set forth in order to avoid obscuring the spirit of the present invention, well-known methods, procedures, flows, and components have not been described in detail.

Further, those of ordinary skill in the art will appreciate that the drawings provided herein are for illustrative purposes and are not necessarily drawn to scale.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, what is meant is "including, but not limited to".

In the description of the present invention, it is to be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In addition, in the description of the present invention, "a plurality" means two or more unless otherwise specified.

For the problem of charging noise of the existing external sound card, the applicant finds that, when a multi-port USB charger charges the external sound card and the live broadcast mobile phone at the same time, as shown in fig. 1 and fig. 2, a solid line is a 5V charging circuit, a dotted line is a charging reference ground, a two-dot chain line is an audio signal, the charging reference ground and the audio signal reference ground form a loop, a large loop is easily subjected to electromagnetic interference, and as the charging current is large, the ground of the charger fluctuates greatly, so that No. 1 ground fluctuates additionally, so that the audio signal received by the live broadcast mobile phone 2 appears obvious current sound, that is, the noise monitored when the external sound card 1 and the mobile phone are charged by using one charger 4 is current sound. The situation is similar when a multi-port USB charger is used for simultaneously charging the external sound card 1 and the accompaniment mobile phone 3. In addition, as shown in fig. 3, the solid line is a 5V charging circuit, the dotted line is a charging reference ground, the two-dot chain line is an audio signal, when the external sound card and the live broadcast mobile phone are charged by using the same computer, the charging reference ground and the original ground network of the system form a loop, the change of the magnetic field in the circuit surrounded by the loop generates a potential difference on the ground network, a difference value Δ V exists between the ground networks of the transmitting end a and the receiving end B of the analog audio loop during charging in fig. 3, the Δ V fluctuation frequency is related to the charger circuit, and the output end of the audio circuit represents continuous noise. To solve this problem, the present application provides an external sound card, as shown in fig. 4, the external sound card includes a charging interface 10, a power management module 20, a battery 30, a level conversion module 40, an application circuit 50, and a live device interface 60, both the charging interface 10 and the battery 30 are connected to the power management module 20, the power management module 20 is configured to control a charging process of the battery 30 of the external sound card 1 and a power supply process to the application circuit 50, the level conversion module 40 is configured to perform level conversion on a current output by the power management module 20 and then transmit the current to the application circuit 50, and the application circuit 50 includes an audio processing circuit for processing audio, a control circuit for controlling a button and an indicator light, and the like. The level shift module 40 is, for example, a level shift chip, and is configured to shift an input voltage to a voltage required by each of the circuits, where the voltage required by different circuits may be different, for example, 3.3V, 2.5V, 1.8V, 1.2V, and so on, and each voltage is set by the level shift chip separately for voltage shift.

The live broadcast device interface 60 is connected to the application circuit 50, and audio signals, control signals and the like in the application circuit 50 can be transmitted to live broadcast devices (e.g., live broadcast mobile phones) through the live broadcast device interface 60, so that live broadcast is realized.

In order to solve the problem of charging noise, the external sound card 1 of the present application further includes a dc isolation power module 80, the dc isolation power module 80 may be disposed between the charging interface 10 and the power management module 20, or disposed between the power management module 20 and the level conversion module, the dc isolation power module 80 includes a first conversion circuit 81, a transformer 82, and a second conversion circuit 83, which are connected in sequence, the first conversion circuit 81 is configured to convert an input dc into an ac and output the ac to the primary side of the transformer 82, and the second conversion circuit 83 is configured to receive an ac output by the secondary side of the transformer 82 and convert the ac into a dc output. The arrangement of the direct-current isolation power supply module 80 can ensure the normal operation of the charging process, and can separate the reference ground of the charging loop and the reference ground of the audio signal loop, so as to avoid the situation that the reference ground of the charging loop and the reference ground of the audio signal loop form a loop, which causes the reference ground of the sound card audio signal loop to generate extra fluctuation and generate obvious current sound in the audio signal received by the live broadcast mobile phone 2, and ensure the live broadcast effect.

Further, as shown in fig. 4, the external sound card may further include an accompaniment device interface 70, the accompaniment device interface 70 is connected to the application circuit 50, and accompaniment devices such as the accompaniment mobile phone 3 may be connected to the application circuit 50 through the accompaniment device interface 70, so as to provide accompaniment audio to the application circuit 50 through the accompaniment device interface 70, and the application circuit 50 mixes the accompaniment audio and the anchor audio and then transmits the mixture to live devices such as the live mobile phone 2 through the live device interface 60. The external sound card 1 and the accompaniment mobile phone 3 can also have the problem of obvious noise when simultaneously charging by using one charger 4, and the external sound card 1 provided by the application can also solve the problem.

In the embodiment shown in fig. 4, the power management module 20 includes a power management circuit 21 and a charging management circuit 22, wherein an input terminal of the charging management circuit 22 is connected to the charging interface 10, and an output terminal thereof is connected to the battery 30; the input end of the power supply management circuit 21 is connected with the battery 30, and the output end is connected with the level conversion module 40. When the external sound card 1 supplies power to the internal circuit (i.e., is not externally connected), the current of the battery 30 is converted by the power management circuit 21 and the level conversion module 40 and then supplied to the application circuit 50. When the external sound card 1 supplies power to the external device (i.e., the external power supply charges the battery 30), the charging interface 10, the charging management circuit 22, the battery 30, and the power management circuit 21 form a charging circuit, and the dc isolation power module 80 may be disposed at any position of the charging circuit, for example, in the embodiment shown in fig. 4, the dc isolation power module 80 is disposed between the output end of the power management circuit 21 and the level conversion module 40, and of course, the dc isolation power module 80 may also be disposed between the charging management circuit 22 and the battery 30, or between the battery 30 and the power management circuit 21.

Of course, it is understood that, if the space allows, as shown in fig. 5, the dc isolated power module 80 may also be disposed between the charging interface 10 and the power management module 20.

In another embodiment, as shown in fig. 6, the power management module 20 includes a power management circuit 21 and a charging management circuit 22, wherein an input terminal of the charging management circuit 22 is connected to the charging interface 10, and an output terminal thereof is connected to the battery 30; the first input end of the power supply management circuit 21 is connected with the charging interface 10, the second input end is connected with the battery 30, and the output end is connected with the level conversion module 40. When the external sound card 1 supplies power to the inside (i.e. not externally connected), the current of the battery 30 enters the power management circuit 21 through the second input terminal and is supplied to the application circuit 50 after being converted by the power level conversion module 40. When the external sound card 1 is externally powered (i.e., the external power supply charges the battery 30), the current of the charging interface 10 is supplied to the application circuit 50 through the first input terminal via the power supply management circuit 21 and the level conversion module 40, and the dc isolation power supply module 80 is disposed between the output terminal of the power supply management circuit 21 and the level conversion module 40.

The dc isolation power supply module 80 may adopt any module capable of achieving isolation effect, and in a preferred embodiment, as shown in fig. 7, the first conversion circuit 81 includes a control chip, a PMOS transistor and an NMOS transistor, where the control chip is used to control on/off of the PMOS transistor and the NMOS transistor to generate a PWM signal wave with a set duty ratio. For example, in a specific embodiment, the control chip includes a TON pin, a CLK pin, a GDN pin, a VCC pin, an NMOS pin, and a PMOS pin, wherein the TON pin, the CLK pin, and the VCC pin are all connected to the source of the PMOS transistor through a first line, the PMOS pin is connected to the gate of the PMOS transistor through a second line, the GDN pin is connected to the source of the NMOS transistor through a third line, the NMOS pin is connected to the gate of the NMOS transistor through a fourth line, the drain of the PMOS transistor is connected to the drain of the NMOS transistor through a fifth line, the TON pin is further connected to the positive electrode of the power supply side through a sixth line, the GDN pin is further connected to the negative electrode of the power supply side through a seventh line, a first resistor R1 is disposed between the first line and the second line, a second resistor R2 is disposed between the third line and the fourth line, a first capacitor C1 is connected between the sixth line and the seventh line, one end of the primary winding of the transformer 82 is connected to the fifth line, and a second capacitor C2 is disposed between the other end of the first line, and a third capacitor C3 is arranged between the third line and the third circuit. The first conversion circuit forms a control signal generation circuit, and a PWM signal wave with a set duty ratio is generated by controlling the on-off of the PMOS tube and the NMOS tube through the control chip.

Since the output will have a voltage drop when the circuit load is running, in order to ensure that the output voltage is within the required range, the transformer 82 needs to be set to 1: n, the value of N may be determined according to the specific circuit, and the transformer 82 needs to be customized. Preferably, as shown in fig. 7, the transformer 82 includes a common mode inductor 821 (the number of primary windings of the common mode inductor 821 is equal to the number of secondary windings), two or more common mode inductors 821 are provided, two or more primary windings of the common mode inductor 821 are connected in parallel, and two or more secondary windings of the common mode inductor 821 are connected in series, so that the plurality of common mode inductors 821 are connected in the manner of forming a 1: the N transformers do not need to be specially customized, and the common-mode inductors with proper quantity are selected according to specific circuits to be connected, so that industrial production is facilitated. The number of the common mode inductors 821 is also determined according to the specific circuit, so as to meet the output voltage requirement, for example, in the embodiment shown in fig. 6, the number of the common mode inductors 821 is three, and of course, may be set to 2, 4 or more according to the specific requirement.

Further, the second converting circuit 83 is provided with a load of about 1mA to prevent the no-load output voltage of the circuit from exceeding the input of the subsequent stage, and in the embodiment shown in fig. 6, the load is a third resistor R3 arranged between the output terminal of the second converting circuit 83 and the ground terminal.

As shown in fig. 7, the second conversion circuit 83 includes a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4, a negative terminal of the first diode D1 and a positive terminal of the second diode D2 are connected to one end of the secondary winding of the transformer 82, a negative terminal of the third diode D3 and a positive terminal of the fourth diode D4 are connected to the other end of the secondary winding of the transformer 82, a positive terminal of the first diode D1 and a positive terminal of the third diode D3 are connected to the ground, a negative terminal of the second diode D2 and a negative terminal of the fourth diode D4 are connected to the output terminal, and a fourth capacitor C4 and a fifth capacitor C5 are connected in parallel between the output terminal and the ground. In this way, the alternating current on the secondary winding side is converted into direct current by the first diode D1, the second diode D2, the third diode D3, and the fourth diode D4 and is output.

Considering the requirement of portability, the external sound card has a high requirement on compactness, and preferably, the dc isolation power module 80 is disposed between the output terminal of the power management circuit 21 and the level conversion module 40, where the current is small, so as to effectively reduce the size of the transformer, and further preferably, as shown in fig. 8, the first conversion circuit 81, the second conversion circuit 82 and the three common mode inductors are integrated on a circuit board 90, the circuit board 90 is rectangular, wherein two common mode inductors 821 are disposed side by side on one long side of the circuit board 90, the other common mode inductor 821 is disposed on one short side of the circuit board 90, and the first conversion circuit 81 and the second conversion circuit 83 are disposed in a space surrounded by the three common mode inductors 821 and the other long side and the other short side of the circuit board 90. Through reasonable layout of the first conversion circuit 81, the second conversion circuit 83 and the three common-mode inductors 821, the structure of the dc isolation power module 80 is more compact, and it is ensured that the external sound card 1 does not affect the compactness of the structure thereof due to the introduction of the dc isolation power module 80.

In the above embodiment, the charging interface 10 is an interface that only has a charging function, the audio data transmission is performed through other interfaces, such as a 3.5mm audio interface, a USB interface, and the like, in another embodiment, the charging interface 10 is used for performing data transmission in addition to the charging of the external sound card 1, that is, a charging terminal and a data transmission terminal are integrated in the charging interface 10, the charging terminal is connected with the power management module 20, so as to charge the external sound card 1 through the charging terminal, and the data transmission terminal is connected with the application circuit 50, so that data interaction between the external sound card 1 and the external device is realized through the charging interface 10, for example, as shown in fig. 9, the external device is a computer, and the computer can transmit accompaniment audio data to the application circuit 50 through the data transmission terminal of the charging interface 10. When a computer is used to charge the direct-broadcast mobile phone 2 and the external sound card 1 at the same time, and the computer is used to transmit audio data to the external sound card 1, as shown in fig. 9, the solid line is a 5V charging circuit, the dotted line is a charging reference ground, and the two-dot chain line is an audio signal, in order to isolate the charging reference ground from the original ground grid of the system, the dc isolation power module 80 needs to be provided, and the addition of the dc isolation power module 80 may damage an audio data transmission loop, so as shown in fig. 10, a data isolation module 110 needs to be provided between the data transmission end and the application circuit 50, so that the circuit may not form a ground loop, but may normally transmit the audio signal. The data isolation module 110 may be any structure capable of achieving isolation without affecting data transmission, such as a photocoupler. The dc isolation power module 80 may be disposed between the power management module 20 and the level shift module 40 as shown in fig. 10, or may be disposed between the charging interface 10 and the power management module 20. Of course, it can be understood that, in the case that the charging terminal and the data transmission terminal are integrated in the charging interface 10, the external sound card may also be additionally provided with a 3.5mm audio interface, a USB interface, and other data transmission interfaces.

It will be appreciated by those skilled in the art that the above-described preferred embodiments may be freely combined, superimposed, without conflict.

It will be understood that the above-described embodiments are illustrative only and not restrictive, and that various obvious and equivalent modifications and substitutions may be made in the details described herein by those skilled in the art without departing from the basic principles of the invention.

Claims (10)

1. An external sound card comprises a charging interface, a power management module, a battery, a level conversion module, an application circuit and a live broadcast equipment interface, wherein the charging interface and the battery are connected with the power management module, the power management module is used for controlling the charging process of the battery of the external sound card and the power supply process of the battery to the application circuit, the level conversion module is used for carrying out level conversion on the current output by the power management module and then transmitting the current to the application circuit, the live broadcast equipment interface is connected with the application circuit, and the external sound card is characterized in that,

the external sound card also comprises a direct current isolation power supply module which is arranged between the charging interface and the power supply management module or between the power supply management module and the level conversion module,

the direct-current isolation power supply module comprises a first conversion circuit, a transformer and a second conversion circuit which are sequentially connected, wherein the first conversion circuit is used for converting input direct current into alternating current and outputting the alternating current to the primary side of the transformer, and the second conversion circuit is used for receiving the alternating current output by the secondary side of the transformer and converting the alternating current into direct current to be output.

2. The external sound card of claim 1, wherein the power management module comprises a power management circuit and a charging management circuit,

the input end of the charging management circuit is connected with the charging interface, and the output end of the charging management circuit is connected with the battery;

the first input end of the power supply management circuit is connected with the charging interface, the second input end of the power supply management circuit is connected with the battery, and the output end of the power supply management circuit is connected with the level conversion module;

the direct current isolation power supply module is arranged between the output end of the power supply management circuit and the level conversion module.

3. The external sound card of claim 1, wherein the power management module comprises a power management circuit and a charging management circuit,

the input end of the charging management circuit is connected with the charging interface, and the output end of the charging management circuit is connected with the battery;

the input end of the power supply management circuit is connected with the battery, and the output end of the power supply management circuit is connected with the level conversion module;

the direct current isolation power supply module is arranged between the output end of the power supply management circuit and the level conversion module, or between the charging management circuit and the battery, or between the battery and the power supply management circuit.

4. The external sound card according to any one of claims 1 to 3, wherein the transformer comprises more than two common mode inductors, primary windings of the more than two common mode inductors are arranged in parallel, and secondary windings of the more than two common mode inductors are arranged in series.

5. The external sound card according to any one of claims 1 to 3, wherein the first conversion circuit comprises a control chip, a PMOS tube and an NMOS tube, and the control chip is configured to control on/off of the PMOS tube and the NMOS tube to generate a PWM signal wave with a set duty ratio.

6. The external sound card according to any one of claims 1 to 3, wherein the second conversion circuit comprises a first diode, a second diode, a third diode and a fourth diode, a negative terminal of the first diode and a positive terminal of the second diode are connected to one end of the secondary winding of the transformer, a negative terminal of the third diode and a positive terminal of the fourth diode are connected to the other end of the secondary winding of the transformer, a positive terminal of the first diode and a positive terminal of the third diode are connected to the ground terminal of the second conversion circuit, a negative terminal of the second diode and a negative terminal of the fourth diode are connected to the output terminal of the second conversion circuit, and a third resistor, a fourth capacitor and a fifth capacitor are connected in parallel between the output terminal of the second conversion circuit and the ground terminal of the second conversion circuit.

7. The external sound card according to any one of claims 1 to 3, wherein a charging terminal and a data transmission terminal are integrated in the charging interface, the charging terminal is connected to the power management module, the data transmission terminal is connected to the application circuit, and a data isolation module is disposed between the data transmission terminal and the application circuit.

8. The external sound card of claim 7, wherein the data isolation module comprises an opto-coupler.

9. The external sound card according to any one of claims 1 to 3, wherein the sound card further comprises an accompaniment device interface, the accompaniment device interface being connected to the application circuit.

10. The external sound card according to any one of claims 1 to 3, wherein the transformer comprises three common mode inductors, primary windings of the three common mode inductors are connected in parallel, and secondary windings of the three common mode inductors are connected in series;

first converting circuit, second converting circuit and three common mode inductance is integrated on a circuit board, the circuit board is the rectangle, wherein two common mode inductance sets up side by side a long avris of circuit board, another one common mode inductance sets up a short avris of circuit board, first converting circuit with second converting circuit sets up three common mode inductance and in another long avris, another short avris of circuit board enclosed the space.

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