阅读说明：本技术 开关电路 (Switching circuit ) 是由 蔡佳琪 高立龙 于 2018-06-26 设计创作，主要内容包括：一种开关电路,包含：一开关以及一电位平移电路。该开关包含一导通端点以及一输入端点,该输入端点系用以接收一输入电压,而该导通端点上的一导通电压控制该开关的导通状态。该电位平移电路包含一电位输入端点以及一电位输出端点,其中该电位输入端点耦接至该输入端点以接收该输入电压,该电位平移电路系用以平移该输入电压以产生一平移电压于该电位输出端点,以及该导通电压系由该平移电压所决定。(A switching circuit, comprising: a switch and a level shift circuit. The switch includes a conducting terminal and an input terminal, the input terminal is used to receive an input voltage, and a conducting voltage at the conducting terminal controls the conducting state of the switch. The level shift circuit includes a level input terminal and a level output terminal, wherein the level input terminal is coupled to the input terminal for receiving the input voltage, the level shift circuit is used for shifting the input voltage to generate a shift voltage at the level output terminal, and the turn-on voltage is determined by the shift voltage.)

1. A switching circuit, comprising:

a switch including a conducting terminal and an input terminal, wherein the input terminal is used for receiving an input voltage, and a conducting voltage on the conducting terminal controls the conducting state of the switch; and

a level shift circuit, comprising a level input terminal and a level output terminal, wherein the level input terminal is coupled to the input terminal of the switch to receive the input voltage, the level shift circuit is used to shift the input voltage to generate a shift voltage at the level output terminal, and the turn-on voltage is determined by the shift voltage.

2. The switch circuit of claim 1, wherein the switch comprises a mosfet.

3. The switch circuit of claim 2, wherein the turn-on terminal is coupled to a gate terminal of the mosfet.

4. The switch circuit of claim 2, wherein the input terminal of the switch is coupled to a source terminal of the mosfet.

5. The switching circuit of claim 1, further comprising:

a buffer circuit coupled between the potential output terminal and the conducting terminal for receiving the translation voltage on the potential output terminal to generate the conducting voltage on the conducting terminal.

6. The switch circuit of claim 5, wherein the buffer circuit comprises a first input terminal, a second input terminal, and an output terminal, the second input terminal is coupled to the output terminal, the output terminal is coupled to the conducting terminal, and the first input terminal is coupled to the potential output terminal of the potential shifting circuit.

7. The switch circuit of claim 1, wherein the potential shifting circuit comprises a first transistor, the potential input terminal is coupled to a gate terminal of the first transistor, and the potential output terminal is coupled to a source terminal of the first transistor.

8. The switch circuit of claim 7, wherein the level shift circuit further comprises a second transistor, the level output node is coupled to a drain terminal of the second transistor, a gate terminal of the second transistor is coupled to a drain terminal of the first transistor.

9. The switch circuit of claim 7, wherein the level shifter further comprises a current source coupled between a reference voltage and the source terminal of the first transistor, or a current source coupled between a reference voltage and a drain terminal of the first transistor.

10. The switch circuit of claim 7, wherein the level shifter circuit further comprises an amplifier, the level output terminal is coupled to an output terminal of the amplifier, a first input terminal of the amplifier is coupled to a drain terminal of the first transistor.

Technical Field

The present invention relates to a switch circuit, and more particularly, to a circuit with high linearity, suitable for negative voltage operation, and applicable to high power output audio products.

Background

The conventional analog switch is usually implemented by a transmission gate (transmission gate), which utilizes a parallel connection of a P-type Metal Oxide Semiconductor Field Effect Transistor (MOSFET) and an N-type MOSFET to reduce the equivalent impedance and increase the linearity, but the achieved specification is still insufficient for audio products unless a considerable area cost is paid, and since the source terminal and the base of the MOSFET are connected together, once the input voltage is a negative voltage, the base of the MOSFET is conducted with a P-type substrate (P-substrate) to cause a leakage current, the switch circuit implemented by the transmission gate is not suitable for the use of products such as a ground reference earphone amplifier (HP _ AMP), this is the structure frequently used in current audio products to save the cost of parts.

Disclosure of Invention

An object of the present invention is to provide a switch circuit having a high linearity and being not affected by a negative voltage of an input voltage, so as to solve the problems in the prior art.

According to an embodiment of the present invention, a switch circuit is disclosed, which comprises a switch and a level shift circuit, wherein the switch comprises a conducting terminal and an input terminal, the input terminal is used for receiving an input voltage, and a conducting voltage on the conducting terminal controls a conducting state of the switch; the level shift circuit includes a level input terminal and a level output terminal, wherein the level input terminal is coupled to the input terminal for receiving the input voltage, the level shift circuit is used for shifting the input voltage to generate a shift voltage at the level output terminal, and the turn-on voltage is determined by the shift voltage.

Drawings

FIG. 1 is a schematic diagram of a switching circuit according to an embodiment of the present invention.

FIG. 2 is a diagram of a level shift circuit according to an embodiment of the present invention.

FIG. 3 is a diagram of a level shift circuit according to another embodiment of the present invention.

Detailed Description

Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. This specification and the claims that follow do not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. Furthermore, the term "coupled" is used herein to encompass any direct and indirect electrical connection, such that if a first device is coupled to a second device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections.

FIG. 1 is a schematic diagram of a switch circuit 10 according to an embodiment of the present invention, as shown in FIG. 1, the switch circuit 10 is used for receiving an input voltage V_inAnd outputs an output voltage V_outThe switch circuit 10 includes a switch 101, a level shift circuit and a buffer circuit 103, wherein the switch 101 includes a conducting terminal T_oAnd an input terminal T_iThe level shift circuit 102 includes a level input terminal T_viAnd a potential output terminal T_vo. Input terminal T of switch 101_iReceiving an input voltage V_inTo turn on the terminal T_oA turn-on voltage V of_onFor determining the on-state of the switch 101; potential input terminal T of the level shift circuit 102_viReceiving an input voltage V_inMake the level shift circuit 102 shift the input voltage V_inTo generate a translation voltage V_shiftAt the potential output terminal T_vo(ii) a The buffer circuit 103 is implemented by an amplifier circuit in the embodiment, wherein the buffer circuit 103 includes a first input terminal T_in1A second input terminal T_in2And an output terminal T_boWherein the first input terminal T_in1Is coupled to the potential output terminal T_voTo receive a translation voltage V_shiftA second input terminal T_in2Coupled to the output terminal T as shown_boSo that the amplifier circuit forms a negative feedback to achieve the effect of a buffer circuit and the buffered translation voltage V_shiftOutput to the conducting terminal T_oForm a turn-on voltage V_onTo control the conductive state of the switch 101. It should be noted that the purpose of the buffer circuit 103 is to avoid the output voltage V_outCoupling to a heavy load causes signal distortion, which is not a necessary circuit, in that itIn other embodiments, the buffer circuit 103 can be omitted, so that the potential output terminal T_voIs directly connected to the conducting terminal T_oSo as to shift the voltage V_shiftIs equal to the turn-on voltage V_onTo control the conductive state of the switch 101. In the present embodiment, the switch 101 includes a transistor T₁In detail, it is a Metal Oxide Semiconductor Field Effect Transistor (MOSFET), in which the transistor T₁A gate terminal of the first transistor is coupled to the conduction terminal T_oA source terminal coupled to the input terminal T_iTo receive an input voltage V_inAnd generating an output voltage V at a drain terminal_outIt is noted that the present invention is not limited to the transistor T₁Of the type, e.g. transistor T₁Can be P-type metal oxide semiconductor field effect transistor or N-type metal oxide semiconductor field effect transistor when transistor T is connected₁When it is an NMOS, the level shift circuit 102 will input the voltage V_inShift upwards (i.e. increase a voltage value) so that the transistor T₁The conduction voltage on the gate terminal of (1) is higher than that on the source terminal; when the transistor T₁When it is a P-type metal oxide semiconductor field effect transistor, the level shift circuit 102 will input the voltage V_inShift down (i.e. decrease a voltage value) so that the transistor T₁The gate terminal is turned on with a lower voltage than the source terminal, and those skilled in the art should understand that the operation of turning on the transistor by controlling the potential difference between the gate voltage and the source voltage of the transistor to be greater than the threshold voltage of the transistor is omitted for brevity.

In detail, when the input voltage V is_inThrough the potential input terminal point T_viAfter entering the level shift circuit 102, a shift voltage V is generated by shifting_shiftGenerating a turn-on voltage V through the buffer circuit 103_onIn the transistor T₁Such that the potential difference between the gate terminal and the source terminal exceeds the transistor T₁Thereby ensuring that the turn-on voltage of the switch 101 is not affected by the input voltage V_inInfluence of amplitude negative voltage, canCompared with the conventional transmission gate switch, the switch circuit 10 has the advantages that the linearity is improved, and even if a heavy load is connected, distortion is not easy to generate by using relatively large on-resistance, so that the circuit area and the manufacturing cost are reduced.

FIG. 2 is a diagram of a level shift circuit 102 according to an embodiment of the present invention, in which the level shift circuit 102 includes a transistor T₂And T₃And a current source C₁And C₂Wherein in this embodiment, the transistor T₂Is realized by a P-type metal oxide semiconductor field effect transistor T₃The transistor T is implemented by an NMOS, but this is not a limitation of the present invention, and those skilled in the art should easily understand that the transistor T₂And T₃Other implementations of (4). As shown in fig. 2, the transistor T₂A gate terminal of the transistor is coupled to the input voltage V_inTo generate a translation voltage V_shiftAt a source terminal, a transistor T₂Is coupled to the transistor T₃A gate terminal of the transistor T₃Is coupled to the transistor T₂The source terminal, transistor T₃A source terminal of which is coupled to a reference voltage (a ground voltage in this embodiment), a current source C₂Coupled to the transistor T₂Between the drain terminal and ground voltage, a current source C₁Coupled to the transistor T₂The source terminal and another reference voltage (a supply voltage in this embodiment). In the embodiment, the level shift circuit 102 is implemented by a source follower circuit, but this is not a limitation of the present invention, and in other embodiments, the level shift circuit 102 can be implemented by other circuits as long as the input voltage V can be obtained_inTranslating a potential difference to generate a translation voltage V_shiftI.e. shall belong to the scope of the present invention.

FIG. 3 is a schematic diagram of a level shift circuit 102 according to another embodiment of the present invention, and the difference between the embodiment shown in FIG. 3 and the embodiment of FIG. 2 is that FIG. 3 replaces the transistor T in the embodiment of FIG. 2 with an amplifier amp₃The rest components are the same, whereinOne of the inputs of the amplifier amp is coupled to the transistor T₂Another input terminal of the drain terminal is coupled to a reference voltage Vref, and an output terminal is coupled to the transistor T₂Thus, the current source C can be increased₂Thereby optimizing the performance of the level shift circuit.

Briefly summarized, the present invention provides a switch circuit, which generates a shift voltage by shifting an input voltage by a potential shift circuit, and generates the shift voltage at a gate terminal of a mosfet through a buffer circuit, such that a potential difference exists between a voltage at the gate terminal and a voltage at a source terminal, the potential difference being greater than a threshold voltage of the mosfet, thereby enabling the mosfet to be turned on at any time without being affected by a negative voltage of an input voltage amplitude, and further optimizing the linearity of the switch. For example, the switch circuit provided by the invention can be coupled between a high-specification amplifier and a low-power amplifier, so that a user can randomly switch modes when using an audio product, for example, when the user needs to listen to music, the switch circuit provided by the invention is required to be coupled to the high-specification amplifier, when the user dials a telephone, the switch circuit provided by the invention is not required to be coupled to the low-power amplifier, and the switch circuit provided by the invention can be switched to be coupled to the low-power amplifier so as to save power loss.

The above-mentioned embodiments are only preferred embodiments of the present invention, and all equivalent changes and modifications made in the claims of the present invention should be covered by the present invention.

Description of the symbols

10 switching circuit

101 switch

102 level shift circuit

103 buffer circuit

V_inInput voltage

V_out Output voltage

T_viPotential input terminal

T_voPotential output terminal

T_oConduction terminal

T_iInput endpoint

T_in1First input terminal

T_in2Second input terminal

T_boOutput end

T₁、T₂、T₃Transistor with a metal gate electrode

C₁、C₂Current source

an amp amplifier.