High-isolation audio switching circuit and method suitable for negative voltage signal
Through the combined design of OSC module, charge pump and pull-down network module, the insufficient isolation and leakage of audio switches under negative voltage signals are solved, and the balance between high isolation and low conduction impedance is achieved, and the performance of negative voltage audio switches is improved.
Patent Information
- Application Number
- CN202510521533.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-24
- Publication Date
- 2025-07-18
AI Technical Summary
In the prior art, under negative voltage signal conditions, the isolation of the audio switch is insufficient and there is a leakage circuit path, making it difficult to improve the isolation while maintaining a low on-impedance.
The combination design of OSC module, charge pump, switch path module and pull-down network module is adopted. Through the synergistic effect of the control signals ctl1 and ctl2, the high-resistance state switching of the high-frequency path of transistors M1 and M2 and the capacitor C1 is realized, eliminating leakage paths and optimizing isolation.
The isolation of negative voltage audio switches is improved, the leakage circuit path is eliminated, and the impact of the pull-down network on the bandwidth of the switch path module is avoided, and the high-frequency isolation performance is enhanced.
Smart Images
Figure CN120343470A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an audio switch circuit and method, in particular to an audio switch circuit and method with high isolation suitable for negative pressure signals, belonging to the technical field of semiconductor integrated circuits. Background Art
[0002] In recent years, audio systems have been developing towards a multi-speaker mode. In such a system, a switch with the ability to transmit negative signals is required. By using an analog switch with the ability to transmit negative signals and combining it with an amplifier circuit with zero voltage bias, a signal source can be used by multiple speakers. When people use a phone, they can also use a music player simultaneously. By using an analog switch capable of transmitting negative pressure signals, the function of signals acting together can be well realized. Such a device has great commercial value.
[0003] In order to reduce the loss of the signal source transmitted on the analog switch path, it is required that the analog switch has a low on-resistance, which means a large area of the switch, resulting in a reduction in the isolation of the switch. In a positive pressure analog switch, the structure of a T-shaped switch can be used to reduce the isolation of the switch. Its structure is shown in Figure 2. 11 and 12 are the switches of the main path, and 10 is the switch connected to the ground 104 at the middle node 103 of the main path switch. When the main path switches 11 and 12 are turned off, the switch 10 is in the closed state, pulling the node 103 to 104 to achieve the effect of improving the isolation. However, when the port voltage is negative, using the traditional structure will result in a large leakage path between 104 and 101 / 102 due to the formation of parasitic diodes in the off state. To solve this problem, a new circuit structure needs to be designed to optimize the isolation of the negative pressure audio switch while eliminating the leakage path. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide an audio switch circuit and method with high isolation suitable for negative pressure signals, and improve the isolation of negative pressure high-frequency switches.
[0005] To solve the above technical problems, the technical solution adopted by the present invention is: An audio switch circuit with high isolation suitable for negative pressure signals, including an OSC module, a charge pump, a switch path module, and a pull-down network module. The output end of the OSC module is connected to the clock end of the charge pump. The output end of the charge pump is connected to the control end of the switch path module and generates a control signal ctl1. The middle node A of the switch path module is connected to the input end of the charge pump and the input end of the pull-down network module.
[0006] Further, the switch path module includes a transistor M1, a transistor M2, and a resistor R1. The gate of the transistor M1 is connected to one end of the resistor R1 and the gate of the transistor M2 and serves as the control end of the switch path module. The drain of the transistor M1 is connected to node B. The source of the transistor M1 is connected to the body terminal of the transistor M1, the other end of the resistor R1, the source of the transistor M2, and the body terminal of the transistor M2 at an intermediate node A. The drain of the transistor M2 is connected to node C.
[0007] Further, the transistor M1 and the transistor M2 are NMOS transistors or PMOS transistors.
[0008] Further, the transistor M1 and the transistor M2 are ldmos or demos.
[0009] Further, the pull-down network module includes a capacitor C1 and a transistor M3. One end of the capacitor C1 serves as the input end of the pull-down network module. The other end of the capacitor C1 is connected to the drain of the transistor M3. The source of the transistor M3 is grounded. The gate of the transistor M3 is connected to a control signal ctl2.
[0010] Further, the transistor M3 is an NMOS transistor.
[0011] Further, when the control signal ctl1 controls the transistor M1 and the transistor M2 to close, the control signal ctl2 controls the transistor M3 to turn off. When the control signal ctl1 controls the transistor M1 and the transistor M2 to turn off, the control signal ctl2 controls the transistor M3 to close.
[0012] A control method for an audio switch circuit with high isolation suitable for negative pressure signals includes the following steps: When the transistor M1 and the transistor M2 are closed, the input end of the charge pump inputs the level of the intermediate node A. The charge pump starts to work under the drive of the OSC module. The output end of the charge pump generates a control signal ctl1 higher than the level value of the intermediate node A. The control signal ctl1 makes the voltage difference generated between the gate and the source of the transistor M1 and the transistor M2 theoretically equal to the high-level voltage of the clock signal at the output end of the OSC module, thereby completely opening the channels of the transistor M1 and the transistor M2 to form a low-impedance path. The control signal ctl2 controls the transistor M3 to disconnect, so that the connection node between the capacitor C1 and the drain of the transistor M3 remains in a high-impedance state, preventing the capacitor C1 from absorbing current from the path of the transistor M1 and the transistor M2 and thus avoiding the influence of the capacitor C1 on the path bandwidth of the transistor M1 and the transistor M2. When the transistors M1 and M2 are turned off, the charge pump and the OSC module stop working. The control signal clt2 controls the transistor M3 to close, maintaining a good connection between the node connecting the capacitor C1 to the drain of the transistor M3 and GND, thereby absorbing the current on the paths of the transistors M1 and M2 and reducing the isolation of the switch. From the parasitic model of the isolation of the switch path module without a pull-down network, the transfer function of the isolation of the switch path module without a pull-down network can be obtained as ; (1) Among them, C p1 is the total parasitic capacitance between the drain of the transistor M1 and the intermediate node A, C p2 is the total parasitic capacitance between the drain of the transistor M2 and the intermediate node A, R L represents the externally connected load resistance, v in is the input signal, v out is the output signal; From the parasitic model of the isolation of the switch path module with a pull-down network, the transfer function of the isolation of the switch path module with a pull-down network can be obtained as ; (2) Among them, C pd is the capacitance value of the capacitor C1; It can be seen from formulas (1) and (2) that in the isolation model with a pull-down network added, the poles of the isolation appear at lower frequencies, meaning that the gain of the isolation decays at lower frequencies to cancel the zeros, thereby improving the isolation at higher frequencies.
[0013] Compared with the prior art, the present invention has the following advantages and effects: The present invention provides an audio switch circuit and method with high isolation suitable for negative pressure signals, improving the isolation of the negative pressure audio switch, eliminating the large circuit leakage path in the traditional T-type switch used in negative pressure audio signals, and while improving the leakage path, avoiding the influence of the pull-down network on the bandwidth of the switch path module. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 is a schematic diagram of an audio switch circuit with high isolation suitable for negative pressure signals according to the present invention.
[0015] Figure 2 is a schematic diagram of a T-type switch used in a traditional positive pressure switch in the prior art.
[0016] Figure 3 is a schematic diagram of the parasitic model of the isolation of the switch path module without a pull-down network in an embodiment of the present invention.
[0017] Figure 4 It is a schematic diagram of the parasitic model of the isolation degree of the switch path module with a pull-down network in the embodiment of the present invention.
[0018] Figure 5 It is a schematic diagram of the simulation results of the isolation degree of the switch path module with and without a pull-down network in the embodiment of the present invention. Detailed implementation manners
[0019] In order to elaborate in detail on the technical solutions adopted by the present invention to achieve the predetermined technical objectives, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only partial embodiments of the present invention, rather than all embodiments. And, without creative efforts, the technical means or technical features in the embodiments of the present invention can be replaced. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.
[0020] As Figure 1 shown, a high-isolation audio switch circuit applicable to negative pressure signals of the present invention includes an OSC module, a charge pump, a switch path module, and a pull-down network module. The output end of the OSC module is connected to the clock end of the charge pump. The output end of the charge pump is connected to the control end of the switch path module and generates a control signal ctl1. The intermediate node A of the switch path module is connected to the input end of the charge pump and the input end of the pull-down network module.
[0021] The OSC module includes, but is not limited to, an inverter-based oscillator, an operational amplifier-based oscillator, an LC-based oscillator, etc.
[0022] The charge pump includes, but is not limited to, a Dickson structure, a cross-coupled structure, a charge transfer structure, a Bootstrap structure.
[0023] The switch path module includes a transistor M1, a transistor M2, and a resistor R1. The gate of the transistor M1 is connected to one end of the resistor R1 and the gate of the transistor M2 and serves as the control end of the switch path module. The drain of the transistor M1 is connected to the node B. The source of the transistor M1 is connected to the body end of the transistor M1, the other end of the resistor R1, the source of the transistor M2, and the body end of the transistor M2 at the intermediate node A. The drain of the transistor M2 is connected to the node C.
[0024] The resistor R1 is used to reset the gate potential of the switch to the voltage level of the source when the charge pump is not working, ensuring that the transistors M1 and M2 are always turned off.
[0025] The transistors M1 and M2 are NMOS transistors or PMOS transistors. The sources and body terminals of the transistors M1 and M2 are both connected to the intermediate node A, forming a back-to-back parasitic diode structure to ensure the bidirectional breakdown voltage between the nodes B and C.
[0026] When there is a breakdown voltage requirement between the nodes B and C, the transistors M1 and M2 are ldmos or demos.
[0027] The pull-down network module includes a capacitor C1 and a transistor M3. One end of the capacitor C1 serves as the input terminal of the pull-down network module, the other end of the capacitor C1 is connected to the drain of the transistor M3, the source of the transistor M3 is grounded, and the gate of the transistor M3 is connected to the control signal ctl2.
[0028] The transistor M3 is an NMOS transistor.
[0029] When the control signal ctl1 controls the transistors M1 and M2 to turn on, the control signal ctl2 controls the transistor M3 to turn off. When the control signal ctl1 controls the transistors M1 and M2 to turn off, the control signal ctl2 controls the transistor M3 to turn on.
[0030] A control method for an audio switch circuit with high isolation suitable for negative voltage signals includes the following steps: When the transistors M1 and M2 are turned on, the input terminal of the charge pump inputs the level of the intermediate node A. The charge pump starts to work under the drive of the OSC module. The output terminal of the charge pump generates a control signal ctl1 higher than the level value of the intermediate node A. The control signal ctl1 makes the voltage difference generated between the gate and the source of the transistors M1 and M2 theoretically equal to the high-level voltage of the clock signal at the output terminal of the OSC module, thereby completely opening the channels of the transistors M1 and M2 to form a low-impedance path. The control signal ctl2 controls the transistor M3 to disconnect, so that the node connecting the capacitor C1 and the drain of the transistor M3 remains in a high-impedance state, preventing the capacitor C1 from absorbing current from the path of the transistors M1 and M2 and thus avoiding the influence of the capacitor C1 on the bandwidth of the path of the transistors M1 and M2.
[0031] When the transistors M1 and M2 are turned off, the charge pump and the OSC module stop working. The control signal clt2 controls the transistor M3 to turn on, maintaining a good connection between the node connecting the capacitor C1 and the drain of the transistor M3 and GND to absorb the current on the path of the transistors M1 and M2 and reduce the isolation of the switch.
[0032] As Figure 3 shown, the transfer function of the isolation of the switch path module without the pull-down network can be obtained from the parasitic model of the isolation of the switch path module without the pull-down network as ; (1) Among them, C p1 is the total parasitic capacitance between the drain of transistor M1 and the intermediate node A, C p2 is the total parasitic capacitance between the drain of transistor M2 and the intermediate node A, R L represents an externally connected load resistor, v in is the input signal, v out is the output signal.
[0033] As Figure 4 shown, the transfer function of the isolation degree of the switch path module with a pull-down network can be obtained from the parasitic model of the isolation degree of the switch path module with a pull-down network as ; (2) Among them, C pd is the capacitance value of capacitor C1.
[0034] From formula (1) and formula (2) and combined with Figure 5 it can be seen that in the isolation degree model with a pull-down network added, the poles of the isolation degree appear at lower frequencies, meaning that the gain of the isolation degree decays at lower frequencies to cancel the zeros, thereby improving the isolation degree at higher frequencies.
[0035] The present invention provides a high-isolation audio switch circuit and method suitable for negative pressure signals, which improves the isolation degree of the negative pressure audio switch, eliminates the large circuit leakage path of the traditional T-type switch when applied to negative pressure audio signals, and while improving the leakage path, avoids the influence of the pull-down network on the bandwidth of the switch path module.
[0036] The above are only preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art, without departing from the scope of the technical solution of the present invention, can make some changes or modifications using the above-disclosed technical content as equivalent embodiments of equivalent changes. However, as long as it does not depart from the content of the technical solution of the present invention, based on the technical essence of the present invention, any simple modification, equivalent replacement and improvement made to the above embodiments within the spirit and principles of the present invention still fall within the protection scope of the technical solution of the present invention.
Claims
1. A high-isolation audio switch circuit suitable for negative pressure signals, characterized in that: It includes an OSC module, a charge pump, a switch path module, and a pull-down network module. The output terminal of the OSC module is connected to the clock terminal of the charge pump. The output terminal of the charge pump is connected to the control terminal of the switch path module and generates a control signal ctl1. The intermediate node A of the switch path module is connected to the input terminal of the charge pump and the input terminal of the pull-down network module.
2. The high-isolation audio switch circuit applicable to negative pressure signals according to claim 1, wherein: The switch path module includes a transistor M1, a transistor M2, and a resistor R1. The gate of the transistor M1 is connected to one end of the resistor R1 and the gate of the transistor M2 and serves as the control terminal of the switch path module. The drain of the transistor M1 is connected to the node B. The source of the transistor M1 is connected to the body terminal of the transistor M1, the other end of the resistor R1, the source of the transistor M2, and the body terminal of the transistor M2 at the intermediate node A. The drain of the transistor M2 is connected to the node C.
3. The high-isolation audio switch circuit applicable to negative pressure signals according to claim 1, characterized in that: The transistor M1 and the transistor M2 are NMOS transistors or PMOS transistors.
4. The high-isolation audio switch circuit applicable to negative pressure signals according to claim 1, characterized in that: The transistor M1 and the transistor M2 are ldmos or demos.
5. The high-isolation audio switch circuit applicable to negative pressure signals according to claim 1, characterized in that: The pull-down network module includes a capacitor C1 and a transistor M3. One end of the capacitor C1 serves as the input terminal of the pull-down network module. The other end of the capacitor C1 is connected to the drain of the transistor M3. The source of the transistor M3 is grounded. The gate of the transistor M3 is connected to the control signal ctl2.
6. The high-isolation audio switch circuit applicable to a negative pressure signal according to claim 5, wherein: The transistor M3 is an NMOS transistor.
7. The high-isolation audio switch circuit applicable to a negative pressure signal according to claim 5, characterized in that: When the control signal ctl1 controls the transistor M1 and the transistor M2 to be closed, the control signal ctl2 controls the transistor M3 to be turned off. When the control signal ctl1 controls the transistor M1 and the transistor M2 to be turned off, the control signal ctl2 controls the transistor M3 to be closed.
8. A control method for an audio switch circuit with high isolation applicable to negative pressure signals according to any one of claims 1-7, characterized in that It includes the following steps: When the transistor M1 and the transistor M2 are closed, the input terminal of the charge pump inputs the level of the intermediate node A. The charge pump starts to work under the drive of the OSC module. The output terminal of the charge pump generates a control signal ctl1 higher than the level value of the intermediate node A. The voltage difference generated between the gate and the source of the transistor M1 and the transistor M2 theoretically equals the high-level voltage of the clock signal at the output terminal of the OSC module, thereby fully opening the channels of the transistor M1 and the transistor M2 to form a low-impedance path. The control signal ctl2 controls the transistor M3 to disconnect, so that the node connecting the capacitor C1 and the drain of the transistor M3 remains in a high-impedance state, preventing the capacitor C1 from absorbing current from the path of the transistor M1 and the transistor M2 and thus avoiding the influence of the capacitor C1 on the bandwidth of the path of the transistor M1 and the transistor M2. When the transistor M1 and the transistor M2 are turned off, the charge pump and the OSC module stop working. The control signal clt2 controls the transistor M3 to be closed, maintaining a good connection between the node connecting the capacitor C1 and the drain of the transistor M3 and GND to absorb the current on the path of the transistor M1 and the transistor M2 and reduce the isolation of the switch. The transfer function of the isolation of the switch path module without a pull-down network can be obtained from the parasitic model of the isolation of the switch path module without a pull-down network. ；（1） Among them, C p1 is the total parasitic capacitance between the drain of transistor M1 and the intermediate node A, C p2 is the total parasitic capacitance between the drain of transistor M2 and the intermediate node A, R L represents the externally connected load resistor, v in is the input signal, v out is the output signal; The transfer function of the isolation of the switch path module with a pull-down network can be obtained from the parasitic model of the isolation of the switch path module with a pull-down network. ；（2） where C pd is the capacitance value of capacitor C1; It can be seen from Equation (1) and Equation (2) that in the isolation model of the added pull-down network, the poles of the isolation appear at lower frequencies, which means that the gain of the isolation decays at lower frequencies to cancel out the zeros, thereby improving the isolation at higher frequencies.