Earphone type identification circuit, audio device and method

Abstract

The invention relates to the field of audio system signal processing, in particular to a multi-standard earphone type identification circuit and method. Comprising an earphone insertion detection unit, a bias voltage generation unit, a buffer operational amplifier unit and a voltage comparison unit, and the voltage comparison unit outputs a comparison result of a bias voltage loaded on an SLEEVE port detection line or an RING2 port detection line and a reference voltage. Judging whether the SLEEVE port detection circuit or the RING2 port detection circuit is a microphone according to the comparison result, and further identifying the type of the earphone; the circuit also comprises an RC low-pass filtering unit and a variable gain amplification unit. According to the identification result, the corresponding function types of the SLEEVE port and the RING2 port can be judged, so that the earphone type is judged, meanwhile, POP sound caused when a bias voltage loading line is switched can be reduced, and reference voltage can be provided for a variable gain amplifier.

Description

Technical Field

[0001] The present invention relates to the field of audio system signal processing, in particular to a multi-standard earphone type recognition circuit and method. Background Art

[0002] Common types of headphones used in embedded audio systems for personal computer terminals usually include 4-segment headsets with stereo headphones and monaural microphones and 3-segment headsets (HEADPHONE) with only stereo sound. The 3.5mm jack on the audio system is connected to these external component headphones or headsets. Among them, the 4-segment headsets have two standards: the American standard headset (CTIAHEADSET, referred to as the American standard headset) and the 4-segment European standard headset (OMTP HEADSET, referred to as the European standard headset).

[0003] Existing detection methods mostly use current feedback detection for 3-segment headphones and 4-segment headsets, but there is no effective identification method for American standard headsets and European standard headsets, which are both 4-segment headsets, and there is no identification method for universal 3-segment headphones and two types of 4-segment headsets. Summary of the invention

[0004] In a first aspect, an embodiment of the present application provides an identification circuit that can effectively identify 4-segment American standard headsets and European standard headsets as well as 3-segment headphones.

[0005] The circuit includes: An earphone insertion detection unit, used to detect an earphone insertion state and generate an earphone insertion signal when the earphone is inserted; An earphone insertion detection unit, used to detect an earphone insertion state and generate an earphone insertion signal when the earphone is inserted; A bias voltage generating unit, which generates a bias voltage according to the headphone insertion signal; the output end of the bias voltage generating unit has a first bias voltage output branch and a second bias voltage output branch; A buffer operational amplifier unit, wherein the input end of the buffer operational amplifier unit is connected to the first bias voltage output branch, the output end of the buffer operational amplifier unit outputs a microphone bias voltage, the output end of the buffer operational amplifier unit has a first microphone bias voltage branch and a second microphone bias voltage branch, the first microphone bias voltage branch is connected to a SLEEVE port detection circuit, the second microphone bias voltage branch is connected to a RING2 port detection circuit, the SLEEVE port detection circuit is connected to a SLEEVE port, and the RING2 port detection circuit is connected to a RING2 port; A voltage comparison unit, the voltage comparison unit comprising a first comparison input terminal, a second comparison input terminal and a comparison output terminal, the first comparison input terminal is connected to a SLEEVE port detection circuit or a RING2 port detection circuit, the second comparison input terminal is connected to a comparison reference voltage input terminal; the comparison output terminal outputs a comparison result of a microphone bias voltage loaded by the SLEEVE port detection circuit or the RING2 port detection circuit and a reference voltage; An RC low-pass filter unit, comprising a resistor and a capacitor connected in parallel, wherein an input end of the RC low-pass filter unit is connected to the SLEEVE port detection circuit or the RING2 port detection circuit, an output end of the RC low-pass filter unit outputs a PGA reference voltage, and the capacitor is connected to the second bias voltage output branch; The variable gain amplifier unit includes an analog signal input terminal, a PGA reference voltage input terminal and a gain output terminal, wherein the analog signal input terminal is connected to the SLEEVE port detection circuit or the RING2 port detection circuit, the PGA reference voltage input terminal is connected to the output terminal of the RC low-pass filter unit, and the gain output terminal outputs an audio gain signal.

[0006] Through the above circuit, the bias voltage is loaded on the SLEEVE port and RING2 port of the headset in turn. According to the detection result of the bias voltage, the function type corresponding to the SLEEVE port and the RING2 port can be determined, thereby determining the type of headset. It is suitable for 4-segment American standard headsets, European standard headsets and 3-segment headsets. At the same time, the charging and discharging characteristics of the capacitor can effectively smooth the voltage changes in the detection process, reduce the POP sound in the recognition process, and extract the DC voltage of the microphone after correctly identifying the American standard headset or the European standard headset, providing a reference voltage for the variable gain amplifier (PGA) of the audio system recording channel.

[0007] In a possible implementation, a charge and discharge control switch is provided on the second bias voltage output branch.

[0008] In a possible implementation, the SLEEVE port detection circuit is provided with a SLEEVE port detection circuit switch, and the RING2 port detection circuit is provided with a RING2 port detection circuit switch; the SLEEVE port detection circuit is connected to a first ground circuit, and a first NMOS is provided on the first ground circuit; the RING2 port detection circuit is connected to a second ground circuit, and a second NMOS is provided on the second ground circuit.

[0009] In a possible implementation, the SLEEVE port detection circuit and the RING2 port detection circuit are connected to the analog input end of the variable gain amplifier unit through an analog input circuit; the SLEEVE port detection circuit and the RING2 port detection circuit are connected to the RC low-pass filter unit through a reference voltage circuit, and an output control switch is provided on the reference voltage circuit.

[0010] In a possible implementation manner, the SLEEVE port detection circuit and the RING2 port detection circuit are connected to the first comparison input terminal of the voltage comparison unit through a comparator input circuit.

[0011] In a possible implementation, the headphone insertion detection unit includes a detection circuit, one end of the detection circuit is connected to the voltage input end, the other end of the detection circuit is grounded, a voltage dividing network consisting of a first voltage dividing resistor and a second voltage dividing resistor is provided on the detection circuit, a voltage output circuit is connected between the first voltage dividing resistor and the second voltage dividing resistor of the detection circuit, the voltage output circuit is connected to the detection unit, and the detection unit determines the insertion status of the headphone according to the level signal output by the voltage output circuit.

[0012] In a second aspect, an embodiment of the present application further provides an audio device, wherein the audio device comprises any one of the earphone type identification circuits in the first aspect.

[0013] In a third aspect, an embodiment of the present application further provides a method for identifying the type of a multi-standard headset, which is implemented based on the identification circuit of the first aspect, and includes the following steps: Waiting for and receiving headphone plug-in signal; After receiving the headphone insertion signal, a bias voltage is generated to charge the capacitor, and the bias voltage is passed through a buffer amplifier to generate a microphone bias voltage; Connecting the SLEEVE port detection circuit of the earphone to load the bias voltage to the SLEEVE port of the earphone; Compare the voltage loaded to the SLEEVE port with a reference voltage to obtain a first comparison result; When the first comparison result matches the first earphone comparison result, identifying the inserted earphone as an American standard 4-band earphone; Identify the inserted earphone as a US standard 4-segment earphone, and obtain the DC voltage of the microphone of the US standard 4-segment earphone from the SLEEVE port as a PGA reference voltage and an analog input signal; Variable gain amplification is performed according to the PGA reference voltage and the analog input signal, and the microphone signal after gain amplification is output to the recording path.

[0014] In a possible implementation manner, when the first comparison result does not match the first headphone comparison result, further performing the following steps: Capacitor smooth discharge; Turn off the SLEEVE port detection circuit of the headset, turn on the RING2 port detection circuit of the headset, and load the microphone bias voltage to the RING2 port; Compare the microphone bias voltage loaded to the RING2 port with a reference voltage to obtain a second comparison result; When the second comparison result matches the second headphone comparison result, identifying the inserted headphone as a European standard 4-band headphone; After identifying that the inserted earphone is a European standard 4-band earphone, the DC voltage of the microphone of the European standard 4-band earphone is obtained from the RING2 port detection circuit as a PGA reference voltage and an analog input signal; Variable gain amplification is performed according to the PGA reference voltage and the analog input signal, and the microphone signal after gain amplification is output to the recording path.

[0015] In a possible implementation, when the second comparison result does not match the second headphone comparison result, it is identified as a three-stage headphone. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the American standard headset terminal structure; Figure 2 This is a schematic diagram of the European standard headset terminal structure; Figure 3 This is a schematic diagram of the 3-section headphone terminal structure; Figure 4 A logic representation diagram of a mechanical switch of an earphone insertion detection module in an embodiment; Figure 5 An equivalent circuit diagram of an earphone detection port of an earphone insertion detection module in an embodiment; Figure 6 is a circuit diagram of a first embodiment; Figure 7 This is a schematic diagram of level changes during the American standard headset detection process of the first embodiment; Figure 8 This is a schematic diagram of level changes during the European standard headset detection process in the first embodiment; Fig. 9 It is a schematic diagram of level changes during the three-segment earphone detection process of the first embodiment; Fig.10 FIG. 4 is a flow chart of the third embodiment of the present invention. DETAILED DESCRIPTION

[0017] The following is a further detailed description in conjunction with specific embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments, not all of the embodiments. Based on the following embodiments, all other embodiments proposed by ordinary technicians in this field without creative work also fall within the scope of protection of the present invention.

[0018] The disclosure of the embodiments provides many different implementations or examples to implement different schemes of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described in the embodiments. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, reference numerals and / or reference letters can be repeated in different examples in the embodiments, and this repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various implementations and / or settings discussed.

[0019] In order to facilitate understanding of the working principle of the embodiment of the present application, before describing the specific scheme of the embodiment of the present application, the relevant basic principles of existing headphone types and audio systems are first described.

[0020] The common types of existing earphones include 3-band earphones and 4-band earphones. 3-band earphones are earphones without microphone input function, and 4-band earphones are earphones with microphone input function. Among them, 4-band earphones are divided into American standard earphones and European standard earphones. The functional differences in input and output of the above earphones are caused by the different functional settings of each connection terminal on the connector. If the corresponding audio system cannot effectively identify each earphone type, it cannot control the input and output of audio signals accordingly, and can only work for specific earphone types.

[0021] like Figure 1 As shown, the connection terminals of the American standard headset are distributed from right to left as follows: the two front terminals TIP and RING1 are standard stereo connections, corresponding to the left channel (L+) and the right channel (R+) respectively; the two rear terminals RING2 and SLEEVE are used for grounding and microphone signals, corresponding to the ground (GND) and the microphone (MIC) respectively.

[0022] like Figure 2 As shown, the connection terminals of the European standard headset are distributed from right to left: the two front terminals TIP and RING1 are standard stereo connections, corresponding to the left channel (L+) and the right channel (R+) respectively; the two rear terminals RING2 and SLEEVE are used for microphone signals and grounding, corresponding to the microphone (MIC) and ground (GND) respectively.

[0023] like Figure 3As shown, the connection terminals of the 3-section headphone head are distributed from right to left as follows: the two terminals TIP and RING1 are standard stereo connections, corresponding to: left channel (L+), right channel (R+) respectively; the last terminal SLEEVE is used for grounding, corresponding to ground (GND).

[0024] From the layout and definition of the above connection terminals, it can be seen that only the last two segments of the three types of headphones are different. The RING2 and SLEEVE of the 4-segment American standard headset are the microphone and ground respectively, the RING2 and SLEEVE of the 4-segment European standard headset are the ground and microphone respectively, and the SLEEVE of the 3-segment headset (RING2 and SLEEVE are combined into one SLEEVE) is grounded.

[0025] Therefore, the overall principle in the embodiment of the present application is to identify the type of earphone by analyzing each terminal type by testing and verifying the terminals. The configurations of the American standard earphone and the European standard earphone are tested in sequence, and if both fail the test, it is determined to be a 3-segment earphone.

[0026] Accordingly, the audio system is a software and hardware system set in various audio and video devices for processing headphone signals to realize audio input and output. The audio system can be embedded in the software and hardware systems of personal computers, tablet computers, mobile communication terminals, and multimedia playback devices. The basic functional modules in such audio systems that are directly related to the work of the embodiments of the present application include a headphone insertion detection module, a headphone type recognition state machine, and a microphone input module.

[0027] The starting working point of the headphone type recognition circuit in this embodiment is to recognize the headphone insertion signal, combined with Figure 4 and Figure 5 As shown, the headphone insertion detection (Jack Detection) module logically mainly includes a mechanical switch and a jack detection (JACK SENSE) port. When no headphone is inserted, the mechanical switch 304 is disconnected from the jack detection port 303. Figure 5 As shown, at this time, the insertion detection port 303 is disconnected, JD Input is equal to VDD, and the Jack Detection output is low level, indicating that no earphone is inserted; when an earphone is inserted, the mechanical switch 304 is pressed, and the insertion detection port 303 is connected and connected to the ground. At this time, JD Input is equal to VDD multiplied by the voltage divider network composed of resistors 301 and 302, and the Jack Detection output is high level, indicating that an earphone is inserted. At this time, the earphone insertion detection (Jack Detection) module sends an earphone insertion signal.

[0028] The headphone insertion detection module is in an idle state when no headphone is inserted. The embodiment of the present application mainly describes the identification operation performed after the headphone is inserted, and the above-mentioned headphone insertion detection step will not be repeated.

[0029] like Figure 6 As shown, the first embodiment of the present application is a headset type identification circuit, the identification circuit comprising: An earphone insertion detection unit 1 is used to detect the earphone insertion state and generate an earphone insertion signal when the earphone is inserted; A bias voltage generating unit 2, which generates a bias voltage according to the headphone insertion signal; the output end of the bias voltage generating unit has a first bias voltage output branch 21 and a second bias voltage output branch 22; A buffer operational amplifier unit 3, wherein the input end of the buffer operational amplifier unit 3 is connected to the first bias voltage output branch 21, and the output end of the buffer operational amplifier unit 3 outputs a microphone bias voltage. The output end of the buffer operational amplifier unit 3 has a first microphone bias voltage branch 31 and a second microphone bias voltage branch 32, wherein the first microphone bias voltage branch 31 is connected to a SLEEVE port detection circuit A, and the second microphone bias voltage branch 32 is connected to a RING2 port detection circuit B, wherein the SLEEVE port detection circuit A is connected to the SLEEVE port, and the RING2 port detection circuit B is connected to the RING2 port; A voltage comparison unit 4, wherein the voltage comparison unit 4 comprises a first comparison input terminal 41, a second comparison input terminal 42 and a comparison output terminal 43. When the voltage comparison unit is working, the first comparison input terminal 41 is connected to the SLEEVE port detection circuit A or the RING2 port detection circuit B, and the second comparison input terminal 42 is connected to the comparison reference voltage input terminal; the comparison output terminal 43 outputs a comparison result between the bias voltage loaded on the SLEEVE port detection circuit A or the RING2 port detection circuit B and the reference voltage, and determines that the SLEEVE port detection circuit A or the RING2 port detection circuit B is a microphone according to the comparison result, thereby identifying the type of earphone; An RC low-pass filter unit 5, comprising a resistor 51 and a capacitor 52 connected in parallel, wherein the input end of the RC low-pass filter unit 5 is connected to the SLEEVE port detection circuit A or the RING2 port detection circuit B, the output end of the RC low-pass filter unit outputs a PGA reference voltage, and the capacitor 52 is connected to the second bias voltage output branch 22; The variable gain amplifier unit 6 includes an analog signal input terminal 61, a PGA reference voltage input terminal 62 and a gain output terminal 63. The analog signal input terminal is connected to the SLEEVE port detection line A or the RING2 port detection line B. The PGA reference voltage input terminal 62 is connected to the output terminal of the RC low-pass filter unit 5. The gain output terminal 63 outputs an audio gain signal.

[0030] When working, the multi-standard headphone detection logic can determine the type of headphones by identifying the position of the MIC. It is generally believed that the equivalent impedance of the MIC is greater than 1K ohms. If the bias voltage is loaded on the MIC through a resistor, a relatively high voltage will be obtained; if the bias voltage is loaded on the ground through a resistor, a voltage close to the ground will be obtained; the output result of the voltage comparator can be used to determine the position of the MIC and the ground, and the type of headphones inserted will be known.

[0031] When the headphone insertion detection unit 1 detects that the headphone is inserted, a headphone insertion signal is generated. At this time, the bias voltage generating unit 2 generates a bias voltage. The generated bias voltage first charges the capacitor 52 in the RC low-pass filter unit 5 through the second bias voltage output branch 22 to generate an "S" type bias voltage, and then the SLEEVE port detection circuit A is turned on. The bias voltage is buffered and amplified by the buffer amplifier unit 3 to generate a microphone bias voltage and loaded to the SLEEVE port of the headphone through the SLEEVE port detection circuit A. At this time, a bias voltage is generated in the SLEEVE port detection circuit A, and the first comparison input terminal 41 of the voltage comparison unit 4 compares the bias voltage on the SLEEVE port detection circuit A with the comparator reference voltage. At this time, if the bias voltage on the SLEEVE port detection circuit A is greater than the comparator reference voltage, the voltage comparison unit 4 outputs the detection result MIC Bias Detect as a low level, indicating that the MIC is detected, the MIC of the American standard headset is correctly connected, and the American standard headset type headset is successfully identified.

[0032] After the American standard headset is successfully recognized, the bias voltage generating unit 2 and the buffer amplifier unit 3 form a proportional amplifier, and the DC voltage on the microphone of the American standard headset is provided as a reference voltage for the variable gain amplifier unit 6 via the RC low-pass filter unit 5. At this time, the microphone of the American standard headset can work normally.

[0033] If the bias voltage on the SLEEVE port detection circuit A is smaller than the comparator reference voltage, the voltage comparison unit 4 outputs the detection result MIC Bias Detect as a high level, which means that the microphone is not detected and the American standard headset recognition fails. At this time, the bias voltage generator is first discharged through the capacitor in the RC low-pass filter unit 5, and then the bias voltage generating unit 2 generates a bias voltage. The generated bias voltage first charges the capacitor 52 in the RC low-pass filter unit 5 through the second bias voltage output branch 22 to generate an "S" type bias voltage, and then the RING2 port detection circuit B is turned on, and the bias voltage is buffered and amplified by the buffer amplifier unit 3 to generate a microphone bias voltage and loaded to the RING2 port of the headset through the RING2 port detection circuit B. At this time, a bias voltage is generated in the RING2 port detection circuit B, and the first comparison input terminal 41 of the voltage comparison unit 4 compares the bias voltage on the RING2 port detection circuit B with the comparator reference voltage. At this time, if the bias voltage on the RING2 port detection circuit B is larger than the comparator reference voltage, the voltage comparison unit 4 outputs the detection result MIC Bias Detect is low level, indicating that MIC is detected, the MIC of the European standard headset is connected correctly, and the European standard headset type headphone is identified successfully.

[0034] Through the above circuit, the bias voltage is loaded on the SLEEVE port and RING2 port of the headset in turn. According to the detection result of the bias voltage, the function type corresponding to the SLEEVE port and the RING2 port can be determined, thereby determining the type of headset. It is suitable for 4-segment American standard headsets, European standard headsets and 3-segment headsets. At the same time, the charging and discharging characteristics of the capacitor can effectively smooth the voltage changes in the detection process, reduce the POP sound in the recognition process, and extract the DC voltage of the microphone after correctly identifying the American standard headset or the European standard headset, providing a reference voltage for the variable gain amplifier (PGA) of the audio system recording channel.

[0035] In this embodiment, a charge and discharge control switch 23 is provided on the second bias voltage output branch 22, and the control switch is closed when the capacitor is charged and discharged; the charge and discharge control switch 23 is used to control the bias voltage generating unit 2 to charge the capacitor 52 when identifying the type of headphones, and to smoothly discharge the capacitor 52 through the bias voltage generating unit 2 during the switching of the detection circuit, so as to avoid POP sound caused by the bias voltage switching on the detection circuit.

[0036] In this embodiment, the SLEEVE port is connected via a SLEEVE port detection line A, the RING2 port is connected via a RING2 port detection line B, the SLEEVE port detection line is provided with a SLEEVE port detection line switch A1, and the RING2 port detection line B is provided with a RING2 port detection line switch B1; the SLEEVE port detection line A is connected to a first grounding line 81, and a first NMOS 83 is provided on the first grounding line 81; the RING2 port detection line connection 72 is provided with a second grounding line 82, and a second NMOS 84 is provided on the second grounding line 82.

[0037] In this embodiment, the SLEEVE port detection circuit A and the RING2 port detection circuit B are connected to the analog input end of the variable gain amplifier unit 6 through the analog input circuit 9; the SLEEVE port detection circuit A and the RING2 port detection circuit B are connected to the RC low-pass filter unit 5 through the reference voltage circuit 10, and the reference voltage circuit 10 is provided with an output control switch 101.

[0038] In this embodiment, the SLEEVE port detection circuit A and the RING2 port detection circuit B are connected to the first comparison input terminal of the voltage comparison unit 4 through a comparator input circuit 11 .

[0039] In terms of other circuit components, the bias voltage generator described in this embodiment has a MIC BiasEnable terminal. When the MIC Bias Enable terminal is at a high level, the bias voltage generator generates a bias voltage. When the MIC BiasEnable terminal is at a low level, the capacitor can discharge to the bias voltage generator.

[0040] The following describes the overall headphone type identification process in combination with specific circuits and switch on / off states.

[0041] When no earphone is plugged in, the entire earphone identification circuit is in IDLE state. Figure 2 The first grounding line 81 is connected to the ground through the first NMOS 83, the second grounding line 82 is connected to the ground through the second NMOS 84, and the other switches are in the open state.

[0042] When a US standard headset is inserted, the headset insertion detection module will be triggered to generate a JACK DETECTION signal, and the HEADSET DETECTION signal will be pulled high. At this time, the DELAY state delay is required to ensure that the headset is fully inserted; During the first identification, it is first assumed that the inserted earphone type is a US standard 4-band earphone, the MIC Bias Enable signal is pulled high, the charge and discharge control switch is closed, the output control switch 101 is opened, and the bias voltage generator charges the capacitor 52 to generate an "S" type bias voltage; at this time, the switch 104 is in the open state, and the bias voltage generates a microphone bias voltage through the buffer amplifier unit 3; the first branch switch 33 (Headset Select A signal control) is closed and the second branch switch 34 (Headset Select B signal control) is opened, and the microphone bias voltage is loaded to the SLEEVE port of the earphone through the first branch resistor 35 (generally 2.2K ohms); the first ground line 81 is disconnected from the ground through the first NMOS 83, and the second ground line 82 is kept connected to the ground through the second NMOS 84. At this time, the first ground line 81 is connected to the SLEEVE (MIC) of the headphone plug, and the second ground line 82 is connected to the RING2 (GND) of the headphone plug; the switch A1 (Headset Select B signal control) on the SLEEVE port detection line A is connected to the SLEEVE (MIC) of the headphone plug, and the second ground line 82 is connected to the RING2 (GND) of the headphone plug; A signal control) switch is closed, switch B1 (Headset Select B signal control) on the detection line B of the RING2 port is opened, and the voltage of the first ground line 81 is compared with the reference voltage of the comparator. According to the design, the voltage of the first ground line 81 is greater than the reference voltage of the comparator at this time, and the voltage comparator outputs the detection result MIC Bias Detect as a low level, indicating that the MIC is detected, the MIC and GND of the American Standard headset are correctly connected, and the American Standard headset is successfully recognized; After the American Standard headset is successfully recognized, the audio system switches to the BUTTON MONITOR state. Figure 2 The switch state in is that the first NMOS 83 is disconnected and the second NMOS 84 is turned on, the charge and discharge control switch is disconnected, the first branch switch 33 is closed and the second branch switch 34 is disconnected, the switch A1 on the SLEEVE port detection circuit A is closed and the switch B1 on the RING2 port detection circuit B is disconnected; the switch 104 is closed, at this time the amplifier and the resistor in the buffer amplifier unit 3 form a proportional amplifier, and the size of the microphone bias voltage can be adjusted as needed; the output control switch 101 is closed, and the resistor 51 and the capacitor 52 together form a low-pass filter with a very small cutoff frequency, which obtains the DC voltage of the MIC on the American standard headset and provides a reference voltage for the variable gain amplifier. In the BUTTON MONITOR state, the MIC of the headset can record normally, and can also monitor whether there is a button pressed on the headset at any time. The detection of the button is other state control of the audio system, which is not within the scope of the working principle of this embodiment and will not be described in detail.

[0043] Figure 7The following is a schematic diagram of the level signal change process in the audio system during the American standard headset recognition process. Figure 7 As shown, when the headset is not detected, the audio system is in the idle state (IDLE), and the Jack Detection signal is low. When the headset is inserted, the Jack Detection signal is high. At this time, the corresponding MIC Bias Enable is pulled high, driving the bias voltage generator to generate a bias voltage, the voltage on the SLEEVE port detection line A increases, and Headset Select A is pulled high. At this time, when the MIC Bias Detect signal output by the voltage comparison unit is low, the American standard headset is successfully recognized.

[0044] When the voltage comparator outputs the detection result MIC Bias Detect as a high level, it means that the MIC is not detected and the American standard headset recognition fails; it is necessary to switch the detection line to further detect the function of the RING2 port in order to further identify the European standard headset or 3-band headset.

[0045] When switching lines, the MIC Bias Enable signal is pulled low, and the charge on the capacitor 52 is discharged through the bias voltage generating unit 1 to avoid POP sound caused by a large change in the voltage of the headset port when the line is switched; after the discharge is completed, the MIC Bias Enable signal is pulled high again, the charge and discharge control switch is closed, the output control switch 101 is disconnected, and the bias voltage generator charges the capacitor 52 again to generate an "S" type bias voltage; at this time, the switch 104 is disconnected, and the bias voltage generates a microphone bias voltage through the buffer amplifier unit 3; the first branch switch 33 (Headset Select A signal control) is disconnected and the second branch switch 34 (Headset Select B signal control) is closed, and the microphone bias voltage is loaded to the RING2 port of the headset through the second branch resistor 36 (generally 2.2K ohms); the first grounding line 81 is connected to the ground through the first NMOS 83, and the second grounding line 82 is connected to the ground through the second NMOS 84 is disconnected from the ground, at this time, the first grounding line 81 is connected to the SLEEVE (GND) of the headphone plug, and the second grounding line 82 is connected to the RING2 (MIC) of the headphone plug; the switch A1 (Headset Select A signal control) on the SLEEVE port detection line A is disconnected, and the switch B1 (HeadsetSelect B signal control) on the RING2 port detection line B is closed, and the voltage of the second grounding line 82 is compared with the reference voltage of the comparator. According to the design, the voltage of the second grounding line 82 is greater than the reference voltage of the comparator at this time, and the voltage comparator outputs the detection result MIC BiasDetect as a low level, indicating that the MIC is detected, the MIC and GND of the European standard headset are correctly connected, and the European standard headset is successfully identified; After the European standard headset is successfully recognized, the status jumps to BUTTON MONITOR status. Figure 2 The switch states in the figure are: the first NMOS 83 NMOS is turned on, the second NMOS 84 NMOS is turned off, the charge and discharge control switch is turned off, the first branch switch 33 is turned off, the second branch switch 34 is turned on, the switch A1 on the SLEEVE port detection line A is turned off, and the switch B1 on the RING2 port detection line B is turned on; the switch 104 is turned on, at this time the amplifier 106 and the resistors 107A and 107B form a proportional operational amplifier, and the size of the microphone bias MIC Bias Voltage can be adjusted as needed; the output control switch 101 is turned on, the resistor 51 and the capacitor 52 together form a low-pass filter with a very small cutoff frequency, and the DC voltage of the MIC on the European standard headset is obtained to provide a reference voltage for the PGA. In the BUTTON MONITOR state, the MIC of the headset can record normally.

[0046] If the voltage comparator outputs the detection result MIC Bias Detect as a high level, it means that the MIC is not detected and the European standard headset recognition fails. After the European standard headset recognition fails, it is considered that a three-stage headset is inserted and returns to the IDLE state. Figure 2 Except for the first NMOS 83 and the second NMOS 84 which are turned on and grounded, the other switches are in the off state.

[0047] Figure 8 The following is a schematic diagram of the level signal change process in the audio system during the European standard headset recognition process. Figure 8 As shown, Figure 8 The level change of the front-end American standard headset detection in Figure 7 The same, only when MIC Bias Detect is high, it is further switched to European standard headset detection. At this time, the headset is in inserted state, so the Jack Detection signal is high. At this time, the corresponding MIC Bias Enable is pulled high, driving the bias voltage generator to generate a bias voltage, the voltage on the SLEEVE port detection line B increases, and Headset Select B is pulled high. At this time, when the MIC BiasDetect signal output by the voltage comparison unit is low, the European standard recognition is successful.

[0048] Fig. 9 The figure is a diagram showing the level signal changes in the audio system during the 3-segment headphone recognition process. Fig. 9 As shown, Fig. 9 The first two stages of the American standard headset test phase and the European standard headset test phase are the same as Figure 8 Similarly, only when MIC Bias Detect is at a high level, it is further switched directly to the 3-stage headset mode. At this time, no microphone is working and all working levels enter a low level state.

[0049] The second embodiment of the present application also provides an audio device, the audio device includes any one of the identification circuits in the first aspect. The audio device is a device having a headphone interface, which can send and receive audio with the headphone after identifying the type of the headphone, the headphone types include American standard headsets, European standard headsets and ordinary headphones, and the corresponding interfaces are American standard 4-segment headset interfaces, European standard 4-segment headset interfaces and three-segment headset interfaces.

[0050] The audio device may be a personal computer (PC), including a desktop computer, a laptop computer and a tablet computer; a smart phone; a multimedia playback device, etc., including devices and equipment with audio signal input and output functions.

[0051] The audio device of this embodiment identifies the type of earphones through the identification circuit in the first aspect, and the headset or earphones can be used normally after the identification.

[0052] Combination Figure 6 and 10 As shown, the third embodiment of the present application further provides a method for identifying the type of a multi-standard headset, which is implemented based on the identification circuit in the first embodiment, and includes the following steps: S1. Wait and receive the headphone insertion signal; S2. After receiving the headphone insertion signal, a bias voltage is generated to charge the capacitor, and the bias voltage is buffered by an operational amplifier to generate a microphone bias voltage; S3. Connect the SLEEVE port detection circuit of the headset and load the microphone bias voltage to the SLEEVE port of the headset; S4. Compare the microphone bias voltage loaded into the SLEEVE port with the reference voltage to obtain a first comparison result; S5. When the first comparison result matches the comparison result of the first headset, the inserted headset is identified as an American standard 4-segment headset; S6. Identify the inserted earphone as a US standard 4-segment earphone, and obtain the DC voltage of the microphone of the US standard 4-segment earphone from the SLEEVE port as the PGA reference voltage and analog input signal; S7. Perform variable gain amplification according to the PGA reference voltage and the analog input signal, and output the microphone signal after gain amplification to the recording path.

[0053] Among them, the first earphone comparison result is a low level, that is, when the first comparison result is a low level, it means that the first comparison result is consistent with the first earphone comparison result, and the inserted earphone is identified as an American standard 4-segment earphone.

[0054] Combination Figure 6 As shown, in this embodiment, when the first comparison result does not conform to the first earphone comparison result, that is, when the first comparison result is a high level, the following steps are further performed: S8. Capacitor discharges smoothly; at this time, the MIC Bias Enable terminal signal of the bias voltage generator 2 is pulled low, the charge and discharge control switch 23 is closed, and the capacitor 52 is discharged smoothly through the bias voltage generator 2.

[0055] S9. Turn off the SLEEVE port detection circuit of the headset, turn on the RING2 port detection circuit of the headset, and load the bias voltage to the RING2 port; S10. Compare the microphone bias voltage loaded to the RING2 port with the reference voltage to obtain a second comparison result; S11. When the second comparison result matches the second headphone comparison result, identifying the inserted headphone as a European standard 4-segment headphone; S12 identifies the inserted headset as a European standard 4-segment headset, obtains the DC voltage of the microphone of the European standard 4-segment headset from the RING2 port detection circuit as the PGA reference voltage and analog input signal; S13. Perform variable gain amplification according to the PGA reference voltage and the analog input signal, and output the microphone signal after gain amplification to the recording path.

[0056] S14. In a possible implementation, when the second comparison result does not match the second headphone comparison result, it is identified as a three-stage headphone.

[0057] The above workflow is performed based on the identification circuit in the first embodiment. For specific step execution contents, please refer to the contents in the first embodiment, which will not be repeated here.

[0058] The above description is only a preferred embodiment of the embodiments of the present application, and does not limit the disclosure scope of the embodiments of the present application. Any equivalent structure or equivalent process transformation made using the embodiment description and drawings of the present application, or directly or indirectly used in other related technical fields, are also included in the patent protection scope supported by the embodiments of the present application.

Claims

1. A headphone type identification circuit, characterized in that: include: An earphone insertion detection unit, used to detect an earphone insertion state and generate an earphone insertion signal when the earphone is inserted; A bias voltage generating unit, generating a bias voltage according to the headphone insertion signal; The output end of the bias voltage generating unit has a first bias voltage output branch and a second bias voltage output branch; A buffer operational amplifier unit, wherein the input end of the buffer operational amplifier unit is connected to the first bias voltage output branch, the output end of the buffer operational amplifier unit outputs a microphone bias voltage, the output end of the buffer operational amplifier unit has a first microphone bias voltage branch and a second microphone bias voltage branch, the first microphone bias voltage branch is connected to a SLEEVE port detection circuit, the second microphone bias voltage branch is connected to a RING2 port detection circuit, the SLEEVE port detection circuit is connected to a SLEEVE port, and the RING2 port detection circuit is connected to a RING2 port; A voltage comparison unit, the voltage comparison unit comprising a first comparison input terminal, a second comparison input terminal and a comparison output terminal, the first comparison input terminal is connected to a SLEEVE port detection circuit or a RING2 port detection circuit, the second comparison input terminal is connected to a comparison reference voltage input terminal; the comparison output terminal outputs a comparison result of a microphone bias voltage loaded by the SLEEVE port detection circuit or the RING2 port detection circuit and a reference voltage; An RC low-pass filter unit, comprising a resistor and a capacitor connected in parallel, wherein an input end of the RC low-pass filter unit is connected to the SLEEVE port detection circuit or the RING2 port detection circuit, an output end of the RC low-pass filter unit outputs a PGA reference voltage, and the capacitor is connected to the second bias voltage output branch; The variable gain amplifier unit includes an analog signal input terminal, a PGA reference voltage input terminal and a gain output terminal, wherein the analog signal input terminal is connected to the SLEEVE port detection circuit or the RING2 port detection circuit, the PGA reference voltage input terminal is connected to the output terminal of the RC low-pass filter unit, and the gain output terminal outputs an audio gain signal.

2. The earphone type identification circuit according to claim 1, characterized in that: The second bias voltage output branch is provided with a charge and discharge control switch.

3. The earphone type identification circuit according to claim 1, characterized in that: The SLEEVE port detection circuit is provided with a SLEEVE port detection circuit switch, and the RING2 port detection circuit is provided with a RING2 port detection circuit switch; the SLEEVE port detection circuit is connected to a first grounding circuit, and a first NMOS is provided on the first grounding circuit; the RING2 port detection circuit is connected to a second grounding circuit, and a second NMOS is provided on the second grounding circuit.

4. The earphone type identification circuit according to claim 1, characterized in that: The SLEEVE port detection circuit and the RING2 port detection circuit are connected to the analog input end of the variable gain amplifier unit through an analog input circuit; the SLEEVE port detection circuit and the RING2 port detection circuit are connected to the RC low-pass filter unit through a reference voltage circuit, and an output control switch is provided on the reference voltage circuit.

5. The earphone type identification circuit according to claim 1, characterized in that: The SLEEVE port detection circuit and the RING2 port detection circuit are connected to the first comparison input terminal of the voltage comparison unit through a comparator input circuit.

6. The earphone type identification circuit according to claim 1, characterized in that: The headphone insertion detection unit includes a detection circuit, one end of the detection circuit is connected to the voltage input end, the other end of the detection circuit is grounded, a voltage dividing network consisting of a first voltage dividing resistor and a second voltage dividing resistor is provided on the detection circuit, a voltage output circuit is connected between the first voltage dividing resistor and the second voltage dividing resistor of the detection circuit, the voltage output circuit is connected to the detection unit, and the detection unit determines the insertion status of the headphone according to the level signal output by the voltage output circuit.

7. An audio device, characterized in that The audio device comprises the headphone type identification circuit according to any one of claims 1 to 6.

8. A method for identifying the type of earphone based on the earphone type identification circuit according to any one of claims 1 to 6, characterized in that: The steps include: Waiting for and receiving headphone plug-in signal; After receiving the headphone insertion signal, a bias voltage is generated to charge the capacitor, and the bias voltage is passed through a buffer amplifier to generate a microphone bias voltage; Connecting the SLEEVE port detection circuit of the earphone to load the bias voltage to the SLEEVE port of the earphone; Compare the microphone bias voltage loaded to the SLEEVE port with a reference voltage to obtain a first comparison result; When the first comparison result matches the first earphone comparison result, identifying the inserted earphone as an American standard 4-band earphone; Identify the inserted earphone as a US standard 4-segment earphone, and obtain the DC voltage of the microphone of the US standard 4-segment earphone from the SLEEVE port as a PGA reference voltage and an analog input signal; Variable gain amplification is performed according to the PGA reference voltage and the analog input signal, and the microphone signal after gain amplification is output to the recording path.

9. The headphone type identification method according to claim 8, characterized in that: When the first comparison result does not match the first earphone comparison result, further performing the following steps: Capacitor smooth discharge; Turn off the SLEEVE port detection circuit of the headset, turn on the RING2 port detection circuit of the headset, and load the microphone bias voltage to the RING2 port; Compare the microphone bias voltage loaded to the RING2 port with a reference voltage to obtain a second comparison result; When the second comparison result matches the second headphone comparison result, identifying the inserted headphone as a European standard 4-band headphone; After identifying that the inserted earphone is a European standard 4-segment earphone, the DC voltage of the microphone of the European standard 4-segment earphone is obtained from the RING2 port detection circuit as a PGA reference voltage and an analog input signal; Variable gain amplification is performed according to the PGA reference voltage and the analog input signal, and the microphone signal after gain amplification is output to the recording path.

10. The earphone type identification method according to claim 9, characterized in that: When the second comparison result does not match the second earphone comparison result, it is identified as a three-stage earphone.

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