Linear driving amplifier without blocking capacitor

Abstract

The utility model relates to the technical field of linear amplifiers, and discloses a linear driving amplifier without a blocking capacitor, which solves the problems in the background technology, and comprises an input circuit, a negative charge pump circuit, an amplification stage, a feedback structure, a negative charge pump circuit and a negative charge pump circuit, comprising a first clock signal driving external flying capacitor Cfly, and an output signal of the first clock signal driving external flying capacitor Cfly drives an external PVSS capacitor; one end of an external flying capacitor is connected with a first positive signal C1P, the other end of the external flying capacitor is connected with a first negative signal C1N, one end of an external Cpvss capacitor is connected with a negative charge pump output signal PVSS and is simultaneously connected with an amplifier negative power supply rail SVSS, and the other end of the external Cpvss capacitor is connected with GND; the negative power rail generated by the negative charge pump circuit and the positive power rail act together to bias the output of the amplifier near the GND, so that an output isolation capacitor is omitted, the area of a circuit board is saved, and the amplifier obtains better low-frequency characteristics.

Description

Technical Field

[0001] The utility model belongs to the technical field of linear amplifiers, in particular to a linear drive amplifier which does not require a DC isolation capacitor. Background Art

[0002] Traditional audio amplifier circuits adopt a single-power supply strategy, and the output signal swing is between the positive power supply level VDD and the ground level GND. This design causes the amplifier input to only pass positive voltage signals, so a DC bias is added to obtain a larger output swing, but the DC bias will cause losses to the speaker equipment connected to the output. In order to achieve isolation between the DC bias and the speaker, a capacitor is usually coupled between the two to form a high-pass filter together with the resistive load. To achieve an ideal filtering effect, the output coupling capacitor needs to have a large capacitance, which will greatly occupy the circuit board space.

[0003] In view of this, the purpose of the utility model is to provide a linear drive amplifier that does not require a DC blocking capacitor. Unlike the traditional single-power supply amplifier circuit whose output voltage fluctuates around VDD / 2, the audio amplifier of the utility model is powered by an external single power supply, but an internal negative charge pump structure is designed to generate a negative voltage (PVSS) that is completely opposite to the positive voltage. The two serve as negative and positive voltage sources of the linear drive amplifier to ensure that the amplifier output oscillates around GND. Since the output voltage amplitude is GND, there is no other DC component in the output signal, ensuring that the output is "noise-free", thereby eliminating the need for a large output isolation capacitor. From the perspective of structural changes, only two ceramic capacitors with smaller capacitance values ​​need to be provided externally, including a charge pump flying capacitor (Cfly) and Cpvss between the negative voltage PVSS and GND, so that the output port can be free of isolation DC capacitors. Resistors Rfb and Rin are set outside the circuit to achieve adjustable gain of the linear drive amplifier. The above structure supports the amplifier circuit to operate at a lower power supply voltage. Utility Model Content

[0004] The utility model provides a linear drive amplifier without an output DC blocking capacitor, which is used to remove the output DC blocking capacitor and effectively reduce noise. To achieve the above purpose, the utility model provides the following scheme: a linear drive amplifier without a DC blocking capacitor, comprising an input circuit, a negative charge pump circuit, an amplifier stage, and a feedback structure; wherein the input circuit comprises left and right control input signals;

[0005] The amplifier stage includes left and right channel amplifiers, the two channels are symmetrical to each other, and are used to amplify the signal output by the input circuit and output it externally;

[0006] The negative charge pump circuit provides a negative power rail for the amplifier stage;

[0007] The feedback structure is used for external connection of the amplifier to realize the adjustable gain function of the amplifier, and includes a first feedback resistor Rfb1 and a second feedback resistor Rfb2, a first input resistor Rin1 and a second input resistor Rin3;

[0008] One end of the first feedback resistor is connected to the first input resistor and the inverting input end of the right channel amplifier, and the other end is connected to the output end of the right amplifier;

[0009] One end of the second feedback resistor is connected to the second input resistor and the inverting input end of the left channel amplifier, and the other end is connected to the output end of the left channel amplifier;

[0010] One end of the first input resistor is connected to the first feedback resistor and is also connected to the inverting input end of the right channel amplifier; the other end is connected to the right channel input signal;

[0011] One end of the second input resistor is connected to the second feedback resistor and is also connected to the inverting input end of the left channel amplifier; the other end is connected to the left channel input signal;

[0012] The negative charge pump circuit optionally includes a first clock signal driving an external flying capacitor Cfly, whose output signal drives an external PVSS capacitor;

[0013] The first clock signal is provided by an internal circuit of the linear drive amplifier;

[0014] One end of the external flying capacitor is connected to the first positive signal C1P, and the other end is connected to the first negative signal C1N.

[0015] One end of the external Cpvss capacitor is connected to the negative charge pump output signal PVSS and the amplifier negative power rail SVSS, and the other end is connected to GND;

[0016] The amplifier stage is a left and right channel amplifier, the two channel amplifiers are symmetrical to each other, and optionally include an input stage, a voltage comparison structure, an intermediate stage, a compensation circuit, an output stage, and an overcurrent protection circuit;

[0017] The input stage includes a first differential pair for receiving an input signal;

[0018] The intermediate stage is used to receive the output current of the input stage, convert it into a first control signal and a second control signal for output;

[0019] The voltage comparison structure responds to the change in the working state of the first differential pair device of the input stage, and dynamically adjusts the output voltage of the intermediate stage;

[0020] The output stage is used to receive the intermediate stage output voltage and bias the output;

[0021] The overcurrent protection circuit is used to sample the output stage current, and includes first and second sampling tubes, and first and second overcurrent control tubes. When the output stage current is too large, the output signal is adjusted.

[0022] Compared with the prior art, the beneficial effects of the utility model are:

[0023] The utility model eliminates the output blocking capacitor, thereby effectively reducing the size of the circuit board. The negative power rail provided by the negative charge pump provides twice the power for the amplifier stage, supports the amplifier to operate in a low voltage 1.8V environment, effectively improves the working efficiency of the amplifier, and after eliminating the output blocking capacitor, it prevents the output capacitor from introducing distortion under low frequency conditions, thereby obtaining better low-frequency characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0025] Figure 1 This is the structural block diagram of the amplifier of the utility model;

[0026] Figure 2 This is a block diagram of the internal structure of the left and right channel amplifier of the utility model; DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all of the embodiments; based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the utility model.

[0028] The utility model provides a linear drive amplifier without an output DC blocking capacitor, a linear drive amplifier without a DC blocking capacitor, comprising an input circuit, a negative charge pump circuit, an amplifier stage, and a feedback structure; wherein the input circuit comprises left and right control input signals; the amplifier stage comprises left and right channel amplifiers, the two channels are symmetrical to each other, and are used to amplify the signal output by the input circuit and output it to the outside; the negative charge pump circuit provides a negative power rail for the amplifier stage.

[0029] like Figure 1The feedback structure provided in the amplifier shown is used for external connection of the amplifier to realize the adjustable gain function of the amplifier, including a first feedback resistor Rfb1 and a second feedback resistor Rfb2, a first input resistor Rin1 and a second input resistor Rin3; one end of the first feedback resistor is connected to the first input resistor and is also connected to the inverting input end of the right channel amplifier, and the other end is connected to the output end of the right amplifier; one end of the second feedback resistor is connected to the second input resistor and is also connected to the inverting input end of the left channel amplifier, and the other end is connected to the output end of the left channel amplifier; one end of the first input resistor is connected to the first feedback resistor and is also connected to the inverting input end of the right channel amplifier; the other end is connected to the right channel input signal; one end of the second input resistor is connected to the second feedback resistor and is also connected to the inverting input end of the left channel amplifier; the other end is connected to the left channel input signal.

[0030] A negative charge pump circuit includes a negative charge pump, which generates a negative power supply opposite to the positive voltage through two external small capacitors Cfly and Cpvss. A clock signal can be generated through an internal oscillator of an amplifier as a negative charge pump switch configuration signal to control the capacitor to perform charging and discharging operations. The generated clock signal includes a first clock signal to drive an external flying capacitor Cfly, and its output signal drives an external Cpvss capacitor; one end of the external flying capacitor is connected to a first positive signal C1P, and the other end is connected to a first negative signal C1N; one end of the external Cpvss capacitor is connected to a negative charge pump output signal PVSS, and is also connected to the amplifier negative power rail SVSS, and the other end is connected to GND.

[0031] In the first half of the first cycle of the clock signal, the C1P signal charges the flying capacitor Cfly of the utility model, and the voltage between the two plates of the capacitor rises. In the second half of the cycle, charge is transferred between Cfly and Cpvss. Since one end of Cpvss is connected to GND, as the circuit repeats this process, the charge between the capacitors is continuously transferred, causing the negative charge pump output signal PVSS voltage to be gradually lowered until the amplitude reaches the negative power rail, and the charge transfer between the capacitors stops. According to the specific implementation of the utility model, MOS devices are required to act as switching devices, corresponding to four switching devices.

[0032] like Figure 2 The left and right channel amplifier internal structure block diagram shown shows the amplifier stage left and right channel amplifiers. The two channel amplifiers are symmetrical to each other, and the internal structures of the left and right amplifiers are exactly the same, including an input stage, a voltage comparison structure, an intermediate stage, a compensation circuit, an output stage, and an overcurrent protection circuit.

[0033] The input stage adopts a P differential structure, including a first differential pair for receiving input signals, the positive input terminal SGND of the amplification channel is connected to GND, the intermediate stage is used to receive the input stage output current, and convert it into a first control signal and a second control signal output; the voltage comparison structure responds to the working state change of the first differential pair device of the input stage, and dynamically adjusts the output voltage of the intermediate stage; the output stage is used to receive the output voltage of the intermediate stage and bias the output; the overcurrent protection circuit is used to sample the output stage current, including the first and second sampling tubes, the first and second overcurrent control tubes, and adjusts the output signal when the output stage current is too large. The input P differential tube is always turned on, so the states of the left and right amplifiers are determined by their respective input signals. After the input signal changes, the two differential tube pairs are biased. The current is shunted, and its drain voltage changes accordingly. The change is transmitted to the gate of the voltage comparison structure P tube, and its drain voltage changes accordingly. The voltage signal is used to assist the change of the intermediate stage common source and common gate structure. Combined with the current change provided by the input stage, it is ensured that the intermediate stage correctly and timely provides the control signal to the output stage to ensure the normal operation of the left and right channel amplifiers. The RC Miller structure is used on the amplification channel to compensate the frequency of the amplification channel. The overcurrent sampling tube is connected in parallel at both ends of the output tube, and its source is connected to the overcurrent protection circuit. The overcurrent control tube affects the gate voltage of the output tube. The left and right amplifiers automatically detect whether there is an overcurrent at the output. When the output is overcurrent, the switch tube is turned on and the output tube is turned off. When the amplifier is turned off, the amplifier output can still be kept near GND.

[0034] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0035] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A linear drive amplifier without a DC blocking capacitor, characterized in that: It includes input circuit, negative charge pump circuit, amplifier stage and feedback structure; Wherein the input circuit includes left and right control input signals; The amplifier stage includes left and right channel amplifiers, the left and right channels are symmetrical to each other, and are used to amplify the signal output by the input circuit and output it externally; The negative charge pump circuit provides a negative power rail for the amplifier stage; The feedback structure is used for external connection of the amplifier to realize the adjustable gain function of the amplifier.

2. The linear drive amplifier without a DC blocking capacitor according to claim 1, characterized in that: The feedback structure includes a first feedback resistor Rfb1 and a second feedback resistor Rfb2, a first input resistor Rin1 and a second input resistor Rin3; One end of the second feedback resistor is connected to the second input resistor and the inverting input end of the left channel amplifier, and the other end is connected to the output end of the left channel amplifier; One end of the first input resistor is connected to the first feedback resistor and is also connected to the inverting input end of the right channel amplifier; the other end is connected to the right channel input signal; One end of the second input resistor is connected to the second feedback resistor and connected to the inverting input end of the left channel amplifier; the other end is connected to the left channel input signal.

3. The linear drive amplifier without a DC blocking capacitor according to claim 1, characterized in that: The negative charge pump circuit has an external flying capacitor Cfly, the capacitor Cfly is driven by a first clock signal, and the first clock output signal drives an external PVSS capacitor; The first clock signal is provided by an internal circuit of the linear drive amplifier; One end of the external flying capacitor is connected to the first positive signal C1P, and the other end is connected to the first negative signal C1N; One end of the external Cpvss capacitor is connected to the negative charge pump output signal PVSS and the amplifier negative power rail SVSS, and the other end is connected to GND.

4. The linear drive amplifier without a DC blocking capacitor according to claim 1, characterized in that: The left and right channel amplifiers each include an input stage, a voltage comparison structure, an intermediate stage, a compensation circuit, an output stage, and an overcurrent protection circuit; The input stage includes a first differential pair for receiving an input signal; The intermediate stage is used to receive the output current of the input stage, convert it into a first control signal and a second control signal for output; The voltage comparison structure responds to the change in the working state of the first differential pair device of the input stage, and dynamically adjusts the output voltage of the intermediate stage; The output stage is used to receive the intermediate stage output voltage and bias the output; The overcurrent protection circuit is used to sample the output stage current, and includes first and second sampling tubes, and first and second overcurrent control tubes. When the output stage current is too large, the output signal is adjusted.

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