Class D power amplifier oscillator circuit, class D power amplifier oscillator and frequency adjustment method thereof

Abstract

A class D power amplifier oscillator circuit is provided. A current control signal that changes with the input amplitude is obtained by adding a peak detection output module and a current conversion module. An oscillator module that adjusts the carrier frequency according to the current control signal is added. The class D power amplifier oscillator circuit can adjust the carrier frequency based on the change of the input amplitude of an audio differential signal. As a result, when the input amplitude of the audio differential signal becomes smaller, the carrier frequency becomes larger and the distortion of the signal is reduced. When the input amplitude of the audio differential signal becomes larger, the carrier frequency becomes smaller and the efficiency of the circuit is improved. The problem that the traditional technical solution cannot adapt to the change of the input amplitude of the audio signal, resulting in large signal distortion or low overall circuit efficiency is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of oscillation control, and in particular relates to a class D power amplifier oscillator circuit, a class D power amplifier oscillator and a frequency adjustment method thereof. Background Art

[0002] At present, traditional audio power amplifiers generally use Class D amplifiers with fixed frequency modulation. However, for Class D audio amplifiers with lower carrier frequencies, the smaller the input amplitude of the audio signal, the greater the distortion; for Class D audio amplifiers with higher carrier frequencies, the larger the input amplitude of the audio signal, the lower the overall system efficiency.

[0003] Therefore, the conventional technical solution has the problem of being unable to adapt to the change of the input amplitude of the audio signal, resulting in large signal distortion or low overall circuit efficiency. Summary of the invention

[0004] In view of this, an embodiment of the present invention provides a class D power amplifier oscillator circuit, a class D power amplifier oscillator and a frequency adjustment method thereof, aiming to solve the problem that traditional technical solutions cannot adapt to changes in the input amplitude of audio signals, resulting in large signal distortion or low overall circuit efficiency.

[0005] A first aspect of an embodiment of the present invention provides a class D power amplifier oscillator circuit, including:

[0006] A peak detection output module for receiving an audio differential signal, comparing voltage peaks of two single-ended signals in the audio differential signal, and outputting the single-ended signal with the larger voltage peak;

[0007] A current conversion module connected to the peak detection output module and the oscillation module, and used for converting the single-ended signal with a larger voltage peak value into a current control signal proportional to the input amplitude of the audio differential signal; and

[0008] An oscillation module connected to the current conversion module and used to adjust the carrier frequency during oscillation according to the current control signal.

[0009] In one embodiment, the peak detection output module includes: a first comparator, a first inverter, a first controllable switch and a second controllable switch, the positive input terminal of the first comparator and the first end of the first controllable switch are connected together as the first input terminal of the peak detection output module, the negative input terminal of the first comparator and the first end of the second controllable switch are connected together as the second input terminal of the peak detection output module, the output terminal of the first comparator and the control terminal of the second controllable switch are connected to the input terminal of the first inverter, the output terminal of the first inverter is connected to the control terminal of the first controllable switch, and the second end of the first controllable switch and the second end of the second controllable switch are connected together as the output terminal of the peak detection output module.

[0010] In one embodiment, the current conversion module includes:

[0011] A current conversion unit connected to the output end of the peak detection output module and used for converting the single-ended signal with a larger voltage peak value into a current control signal; and

[0012] A current ratio amplification unit connected to the output end of the current conversion unit and the input end of the oscillation module, and used to amplify the current control signal according to a preset ratio.

[0013] In one embodiment, the circuit conversion unit includes: a first operational amplifier, a second operational amplifier, a first resistor and a first transistor, the positive phase input terminal of the first operational amplifier is used to access a reference voltage, the negative phase input terminal of the first operational amplifier and the output terminal of the first operational amplifier are commonly connected to the first end of the first resistor, the second end of the first resistor is connected to the output terminal of the second operational amplifier and the input terminal of the first transistor, the positive phase input terminal of the second operational amplifier is connected to the output terminal of the peak detection output module, the negative phase input terminal of the second operational amplifier is connected to the control terminal of the first transistor, and the output terminal of the first transistor serves as the output terminal of the circuit conversion unit.

[0014] In one embodiment, the current ratio amplification unit includes: a second transistor and a third transistor, the control end of the second transistor, the input end of the second transistor and the control end of the third transistor are connected together as the input end of the current ratio amplification unit, the output end of the second transistor is connected to the input end of the third transistor, and the output end of the third transistor serves as the output end of the current ratio amplification unit.

[0015] In one embodiment, the oscillation module includes: a fourth transistor, a fifth transistor, a sixth transistor, a seventh transistor, an eighth transistor, a ninth transistor, a tenth transistor, an eleventh transistor, a first capacitor, a third controllable switch, a fourth controllable switch, a second comparator and a second inverter, the input end of the fourth transistor, the control end of the fourth transistor, the control end of the fifth transistor and the control end of the sixth transistor are connected together as the input end of the oscillation module, the input end of the oscillation module is connected to a current control signal and a reference current, the output end of the fourth transistor, the output end of the fifth transistor, the output end of the sixth transistor, the second end of the first capacitor and the output end of the eleventh transistor are connected together to the ground, the output end of the fifth transistor and the control end of the seventh transistor, the output end of the seventh transistor and the control end of the eighth transistor are connected together, the input end of the seventh transistor and the input end of the eighth transistor are connected together, and the eighth transistor The output end of the first controllable switch is connected to the input end of the ninth transistor, the control end of the ninth transistor, the control end of the tenth transistor, the output end of the second comparator, the control end of the third controllable switch, the control end of the fourth controllable switch and the input end of the second inverter are connected in common, the output end of the ninth transistor, the input end of the tenth transistor, the first end of the first capacitor, the input end of the eleventh transistor and the non-inverting input end of the second comparator are connected in common, the output end of the tenth transistor is connected to the input end of the sixth transistor, the first end of the third controllable switch is externally connected to the first reference voltage, the second end of the third controllable switch and the second end of the fourth controllable switch are commonly connected to the inverting input end of the second comparator, the first end of the fourth controllable switch is externally connected to the second reference voltage, the control end of the fourth controllable switch, the control end of the eleventh transistor and the output end of the second inverter are commonly connected, and the output end of the inverter serves as the output end of the oscillation module.

[0016] A second aspect of an embodiment of the present invention provides a class D power amplifier oscillator, comprising:

[0017] An audio preamplifier circuit, used for receiving an audio analog signal, amplifying the audio analog signal and outputting an audio differential signal; and

[0018] As described in the first aspect of the embodiment of the present invention, the class D power amplifier oscillator circuit is connected to the audio pre-amplifier circuit.

[0019] In one embodiment, the audio pre-amplifier circuit includes: a third operational amplifier, a second capacitor, a third capacitor, a second resistor, a third resistor, a fourth resistor and a fifth resistor, the first end of the second capacitor is connected to the audio analog signal, the second end of the second capacitor is connected to the first end of the second resistor, the second end of the second resistor and the first end of the third resistor are connected to the first input end of the third operational amplifier, the first end of the third capacitor is grounded, the second end of the third capacitor is connected to the first end of the fourth resistor, the second end of the fourth resistor is connected to the second output end of the third operational amplifier and the first end of the fifth resistor, the first differential signal output single-end of the third operational amplifier and the second end of the third resistor are connected together as the first single-ended signal output end of the audio pre-amplifier circuit, and the second differential signal output single-end of the third operational amplifier and the second end of the fifth resistor are connected together as the second single-ended signal output end of the audio pre-amplifier circuit.

[0020] A third aspect of an embodiment of the present invention provides a frequency adjustment method for a class D power amplifier oscillator, comprising:

[0021] Get the audio analog signal input by the Class D power amplifier;

[0022] Based on the input amplitude of the audio analog signal, generating a current control signal that is proportional to the input amplitude of the audio analog signal;

[0023] The current control signal is superimposed on a reference current of a class D power amplifier oscillator and then output to the class D power amplifier oscillator.

[0024] In one embodiment, the step of generating a current control signal proportional to the input amplitude of the audio differential signal based on the input amplitude of the audio differential signal comprises:

[0025] amplifying the audio analog signal and converting it into an audio differential signal having two single-ended signals;

[0026] Comparing the voltage peak values ​​of the two single-ended signals of the audio differential signal and generating a comparison result;

[0027] Output a single-ended signal with a larger voltage peak value according to the comparison result;

[0028] The single-ended signal is converted into a current control signal in direct proportion.

[0029] The above-mentioned class D power amplifier oscillator circuit and class D power amplifier oscillator, by adding a peak detection output module and a current conversion module, obtain a current control signal that changes with the input amplitude, and by adding an oscillation module that adjusts the carrier frequency according to the current control signal, it is realized that the class D power amplifier oscillator circuit can adjust the carrier frequency based on the change of the input amplitude of the audio differential signal, thereby realizing that when the input amplitude of the audio differential signal becomes smaller, the carrier frequency becomes larger and the distortion of the signal is reduced, and when the input amplitude of the audio differential signal becomes larger, the carrier frequency becomes smaller and the efficiency of the circuit is improved, thereby solving the problem that the traditional technical solution cannot adapt to the change of the input amplitude of the audio signal, resulting in large signal distortion or low overall circuit efficiency. The above-mentioned frequency adjustment method of the class D power amplifier oscillator generates a current control signal that is proportional to the input amplitude of the audio analog signal, and superimposes the current control signal on the reference current of the class D power amplifier oscillator, so that the carrier frequency of the class D power amplifier oscillator is proportional to the current control signal, so that the carrier frequency can be adjusted according to the input amplitude change, which solves the problem that the traditional technical solution cannot adapt to the input amplitude change of the audio signal, resulting in large signal distortion or low overall circuit efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0031] Figure 1 A circuit diagram of a class D power amplifier oscillator circuit provided by an embodiment of the present invention;

[0032] Figure 2 for Figure 1 An example circuit schematic diagram of a peak detection output module in a class D power amplifier oscillation circuit is shown;

[0033] Figure 3 for Figure 1 An example circuit schematic diagram of a current conversion module in a class D power amplifier oscillation circuit is shown;

[0034] Figure 4 for Figure 1 An example circuit schematic diagram of an oscillation module in a class D power amplifier oscillation circuit is shown;

[0035] Figure 5 A circuit diagram of a class D power amplifier oscillator provided in one embodiment of the present invention;

[0036] Figure 6 for Figure 5 An example circuit schematic diagram of an audio preamplifier circuit in a Class D power amplifier oscillator is shown;

[0037] Figure 7 A specific flow chart of a frequency adjustment method for a class D power amplifier oscillator provided in one embodiment of the present invention;

[0038] Figure 8 for Figure 7 The specific flow chart of step S200 of the frequency adjustment method of the class D power amplifier oscillator is shown. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0040] See also Figure 1 , a circuit diagram of a class D power amplifier oscillator circuit provided by an embodiment of the present invention, for the sake of convenience of explanation, only the part related to the present embodiment is shown, which is described in detail as follows:

[0041] The class D power amplifier oscillator circuit in this embodiment includes: a peak detection output module 100, a current conversion module 200 and an oscillation module 300. The output end of the peak detection output module 100 is connected to the input end of the current conversion module 200, and the output end of the current conversion module 200 is connected to the input end of the oscillation module 300. The peak detection output module 100 is used to receive the audio differential signals OUTP and OUTN, compare the voltage peaks of the two single-ended signals OUTP and OUTN in the audio differential signal, and output the single-ended signal with a larger voltage peak as the voltage output signal VPEAK; the current conversion module 200 is used to convert the single-ended signal with a larger voltage peak into a current control signal IBCON proportional to the input amplitude of the audio differential signal; the oscillation module 300 is used to adjust the carrier frequency of the oscillation according to the current control signal IBCON.

[0042] It should be understood that the peak detection output module 100 can be composed of a device or chip with a comparison function, such as a comparator, a microprocessor or an integrated circuit with a comparison logic processing function; the current conversion module 200 can be composed of a combination of devices capable of converting voltage into current, such as a resistor; the oscillation module 300 can be a current oscillation module 300, an RC oscillation module 300, etc.; the single-ended signal with a larger voltage peak is proportional to the current control signal IBCON, and the single-ended signal is positively correlated with the input amplitude of the audio differential signal, so the current control signal IBCON is proportional to the input amplitude of the audio differential signal, and the proportionality coefficient of the proportional relationship can be adjusted by adjusting the internal parameters of the voltage-to-current conversion device, for example, it can be achieved by adjusting the resistance value of the resistor, or it can be adjusted by adjusting the amplification ratio of the current control signal IBCON. When the voltage peak value of the single-ended signal OUTP is greater than the voltage peak value of the single-ended signal OUTN, the single-ended signal OUTP is output to the current conversion module 200 as a voltage output signal VPEAK. Conversely, when the voltage peak value of the single-ended signal OUTN is greater than the voltage peak value of the single-ended signal OUTP, the single-ended signal OUTN is output to the current conversion module 200 as a voltage output signal VPEAK. Optionally, the peak detection output module 100 may include a comparison unit and a selection output unit. The two input ends of the comparison unit are respectively connected to the single-ended signal OUTP and the single-ended signal OUTN. The input end of the comparison unit is connected to the control end of the selection output unit. The input end of the selection output unit is respectively connected to the single-ended signal OUTP and the single-ended signal OUTN. The output end of the selection output unit is connected to the input end of the current conversion module 200. The comparison unit is used to compare the voltage peak values ​​of the two single-ended signals in the audio differential signal and output the comparison result. The selection output unit is used to output the single-ended signal with a larger voltage peak value according to the comparison result. The comparison result can be a high or low level. The comparison unit can be composed of a comparator, and the selection output unit can be composed of an inverter and a controllable switch.

[0043] It should be understood that the peak value of the signal is positively correlated with the input amplitude of the signal, that is, the voltage peak value of the single-ended signal in this embodiment is positively correlated with the input amplitude of the audio differential signal, that is, the larger the input amplitude of the audio differential signal, the larger the voltage peak value of the corresponding single-ended signal, and the smaller the input amplitude of the audio differential signal, the smaller the voltage peak value of the corresponding single-ended signal; the current control signal IBCON is a current signal that is in direct proportion to the single-ended signal with a larger voltage peak value, that is, the current control signal IBCON is in direct proportion to the input amplitude of the audio differential signal. In this embodiment, by adding the current control signal IBCON to the oscillation module 300, the load The wave frequency is inversely proportional to the input amplitude of the audio differential signal, that is, when the input amplitude of the audio differential signal increases, the current control signal IBCON increases, at this time the carrier frequency is lowered, and the efficiency of the Class D power amplifier oscillation circuit increases, avoiding the problem of low system efficiency caused by the input signal amplitude increasing while the carrier frequency remains at the original value in the traditional technical solution; when the input amplitude of the audio differential signal decreases, the current control signal IBCON decreases, at this time the carrier frequency is increased, and the distortion of the Class D power amplifier oscillation circuit decreases, avoiding the problem of excessive distortion caused by the input signal amplitude decreasing while the carrier frequency remains at the original value in the traditional technical solution.

[0044] The class D power amplifier oscillator circuit in this embodiment obtains a current control signal IBCON that changes with the input amplitude by adding a peak detection output module 100 and a current conversion module 200, and by adding an oscillation module 300 that adjusts the carrier frequency according to the current control signal IBCON, the class D power amplifier oscillator circuit can adjust the carrier frequency based on the change of the input amplitude of the audio differential signal, so that when the input amplitude of the audio differential signal becomes smaller, the carrier frequency becomes larger and the distortion of the signal is reduced, and when the input amplitude of the audio differential signal becomes larger, the carrier frequency becomes smaller and the efficiency of the circuit is improved, which solves the problem that the traditional technical solution cannot adapt to the change of the input amplitude of the audio signal, resulting in large signal distortion or low overall circuit efficiency.

[0045] See also Figure 2In one embodiment, the peak detection output module 100 includes: a comparator U1, an inverter F1, a controllable switch S1 and a controllable switch S2, the positive input terminal of the comparator U1 and the first terminal of the controllable switch S1 are connected together as the first input terminal of the peak detection output module 100, the negative input terminal of the comparator U1 and the first terminal of the controllable switch S2 are connected together as the second input terminal of the peak detection output module 100, the output terminal of the comparator U1 and the control terminal of the controllable switch S2 are connected to the input terminal of the inverter F1, the output terminal of the inverter F1 is connected to the control terminal of the controllable switch S1, and the second terminal of the controllable switch S1 and the second terminal of the controllable switch S2 are connected together as the output terminal of the peak detection output module 100. It should be understood that the first input terminal of the peak detection output module 100 is connected to the single-ended signal OUTP in the audio differential signal, and the second input terminal of the peak detection output module 100 is connected to the single-ended signal OUTN in the audio differential signal.

[0046] It should be understood that the comparator U1 in this embodiment is a voltage comparator, the inverter F1 can be replaced by a NOT gate, and the controllable switch S1 and the controllable switch S2 can be controllable switch devices such as thyristors and switch tubes. The peak detection output module 100 in this embodiment adds the comparator U1 as a comparison unit to compare the two single-ended signals in the audio differential signal in real time, and adds the inverter F1, the controllable switch S1 and the controllable switch S2 as the selection output unit, so as to select the controllable switch S1 connected to the single-ended signal OUTN or the controllable switch S2 connected to the single-ended signal OUTP according to the output result of the comparator U1, and output the single-ended signal with a larger voltage peak as the voltage output signal VPEAK to the current conversion module 200 according to the comparison result.

[0047] See also Figure 3 In one embodiment, the current conversion module 200 includes: a current conversion unit 210 and a current proportional amplification unit 220. The input end of the current conversion unit 210 is connected to the output end of the peak detection output module 100 as the input end of the current conversion module 200, and the output end of the current conversion unit 210 is connected to the input end of the current proportional amplification unit 220. The output end of the current proportional amplification unit 220 is connected to the oscillation module 300 as the output end of the current conversion module 200. The current conversion unit 210 is used to convert a single-ended signal with a larger voltage peak into a current control signal IBCON. The current proportional amplification unit 220 is used to amplify the current control signal IBCON according to a preset ratio.

[0048] It should be understood that the current conversion unit 210 can be composed of an operational amplifier, a resistor, etc.; the current proportional amplification unit 220 can be composed of a mirror current source, and the current control signal IBCON is in direct proportion to the single-ended signal with a larger voltage peak. The current conversion module 200 in this embodiment converts the single-ended signal with a larger voltage peak output by the peak detection output module 100 into the current control signal IBCON by adding the current conversion unit 210, and amplifies the current control signal IBCON by adding the current proportional amplification unit 220, thereby achieving adjustable control of the size of the current control signal IBCON.

[0049] See also Figure 3 In one embodiment, the circuit conversion unit includes: an operational amplifier U2, an operational amplifier U3, a resistor R1 and a transistor Q1, the positive phase input terminal of the operational amplifier U2 is used to access the reference voltage VREF, the negative phase input terminal of the operational amplifier U2 and the output terminal of the operational amplifier U2 are commonly connected to the first end of the resistor R1, the second end of the resistor R1 is connected to the output end of the operational amplifier U3 and the input end of the transistor Q1, the positive phase input terminal of the operational amplifier U3 is connected to the output end of the peak detection output module 100, the negative phase input terminal of the operational amplifier U3 is connected to the control end of the transistor Q1, and the output end of the transistor Q1 serves as the output end of the circuit conversion unit.

[0050] It should be understood that the transistor Q1 can be an NMOS tube, a PMOS tube, an IGBT thyristor or a triode, etc. For example, when the transistor Q1 is an NMOS tube, the gate of the NMOS tube is the control terminal of the transistor Q1, the drain of the NMOS tube is the input terminal of the transistor Q1, and the source of the NMOS tube is the output terminal of the transistor Q1. The reference voltage VREF in this embodiment is a common mode voltage signal. The calculation formula of the current control signal IBCON in this embodiment is: IBCON = (VPEAK-VREF) / R1.

[0051] See also Figure 3 In one embodiment, the current ratio amplification unit 220 includes: a transistor Q2 and a transistor Q3, the control end of the transistor Q2, the input end of the transistor Q2 and the control end of the transistor Q3 are connected together as the input end of the current ratio amplification unit 220, the output end of the transistor Q2 is connected to the input end of the transistor Q3, and the output end of the transistor Q3 is used as the output end of the current ratio amplification unit 220.

[0052] It should be understood that transistor Q2 and transistor Q3 can be NMOS tubes, PMOS tubes, IGBT thyristors or triodes, etc. For example, when the transistor is an NMOS tube, the gate of the NMOS tube is the control end of the transistor, the drain of the NMOS tube is the input end of the transistor, and the source of the NMOS tube is the output end of the transistor.

[0053] It should be understood that the internal operating parameters of transistors Q2 and Q3 can be adjusted to make them operate in the amplification region, thereby achieving amplification of the current control signal IBCON. The amplification ratio of the current ratio amplification unit 220 in this embodiment is 1:1.

[0054] See also Figure 4 In one embodiment, the oscillation module 300 includes: a transistor Q4, a transistor Q5, a transistor Q6, a transistor Q7, a transistor Q8, a transistor Q9, a transistor Q10, a transistor Q11, a capacitor C1, a controllable switch S3, a controllable switch S4, a comparator U4 and an inverter F2, an input end of the transistor Q4, a control end of the transistor Q4, a control end of the transistor Q5 and a control end of the transistor Q6 are connected together as an input end of the oscillation module 300, an input end of the oscillation module 300 is connected to a current control signal IBCON and a reference current IBOSC, an output end of the transistor Q4, an output end of the transistor Q5, an output end of the transistor Q6, a second end of the capacitor C1 and an output end of the transistor Q11 are connected together to ground, an output end of the transistor Q5 and a control end of the transistor Q7, an output end of the transistor Q7 and a control end of the transistor Q8 are connected together, an input end of the transistor Q7 and an input end of the transistor Q8 are connected together, an output end of the transistor Q8 and a control end of the transistor Q11 are connected together, The input end of the controllable switch S3 is connected to the input end of the oscillator module 300, the control end of the transistor Q9, the control end of the transistor Q10, the output end of the comparator U4, the control end of the controllable switch S3, the control end of the controllable switch S4 and the input end of the inverter F2 are connected in common, the output end of the transistor Q9, the input end of the transistor Q10, the first end of the capacitor C1, the input end of the transistor Q11 and the non-inverting input end of the comparator U4 are connected in common, the output end of the transistor Q10 is connected to the input end of the transistor Q6, the first end of the controllable switch S3 is externally connected to the first reference voltage V1, the second end of the controllable switch S3 and the second end of the controllable switch S4 are commonly connected to the inverting input end of the comparator U4, the first end of the controllable switch S4 is externally connected to the second reference voltage V2, the control end of the controllable switch S4, the control end of the transistor Q11 and the output end of the inverter F2 are commonly connected, and the output end of the inverter F2 serves as the output end of the oscillation module 300, and the output end of the oscillation module 300 is used to be connected to an external circuit to provide a clock oscillation signal for the external circuit.

[0055] It should be understood that transistor Q4, transistor Q5, transistor Q6, transistor Q7, transistor Q8, transistor Q9, transistor Q10, and transistor Q11 can be NMOS tubes, PMOS tubes, IGBT thyristors or triodes, etc. For example, when the transistor is an NMOS tube, the gate of the NMOS tube is the control end of the transistor, the drain of the NMOS tube is the input end of the transistor, and the source of the NMOS tube is the output end of the transistor; the comparator U4 can be a voltage comparator; the inverter F2 can be replaced by a NOT gate, and the controllable switch S3 and the controllable switch S4 can be controllable switch devices such as thyristors and switch tubes.

[0056] The carrier frequency of the oscillation module 300 in this embodiment is: T=2(V2-V1)*C1 / (IBCON+IBSOC). The carrier frequency of the oscillation module 300 is a time-varying frequency that changes with the current control signal IBCON, that is, the carrier frequency can be adjusted based on the change of the input amplitude of the audio differential signal.

[0057] See also Figure 5 The second aspect of the embodiment of the present invention provides a class D power amplifier oscillator, including: an audio pre-amplifier circuit 400 and a class D power amplifier oscillator circuit as in the first aspect of the embodiment of the present invention, the audio pre-amplifier circuit 400 is connected to the input end of the peak detection output module 100 of the class D power amplifier oscillator circuit, the audio pre-amplifier circuit 400 is used to access the audio analog signal, amplify the audio analog signal and output the audio differential signal, the class D power amplifier oscillator circuit is as in the first aspect of the embodiment of the present invention, and will not be described in detail here.

[0058] See also Figure 6 In one embodiment, the audio pre-amplifier circuit 400 includes: an operational amplifier U5, a capacitor C2, a capacitor C3, a resistor R2, a resistor R3, a resistor R4 and a resistor R5, the first end of the capacitor C2 is connected to the audio analog signal, the second end of the capacitor C2 is connected to the first end of the resistor R2, the second end of the resistor R2 and the first end of the resistor R3 are connected to the first input end of the operational amplifier U5, the first end of the capacitor C3 is grounded, the second end of the capacitor C3 is connected to the first end of the resistor R4, the second end of the resistor R4 is connected to the second output end of the operational amplifier U5 and the first end of the resistor R5, the first differential signal output single end of the operational amplifier U5 and the second end of the resistor R3 are connected together as the first single-ended signal output end of the audio pre-amplifier circuit 400, and the second differential signal output single end of the operational amplifier U5 and the second end of the resistor R5 are connected together as the second single-ended signal output end of the audio pre-amplifier circuit 400. It should be understood that the signal amplitude, voltage parameters, current parameters, etc. of the audio analog signal and the audio differential signal in the embodiment of the present invention are positively correlated. When the amplification ratio of the operational amplifier U5 is 1:1, the audio analog signal and the audio differential signal are the same signal.

[0059] See also Figure 7 A third aspect of an embodiment of the present invention provides a frequency adjustment method for a class D power amplifier oscillator, comprising:

[0060] Step S100: obtaining an analog audio signal input by a class D power amplifier.

[0061] It should be understood that the audio analog signal can be obtained by directly connecting to the audio analog signal output terminal of the class D power amplifier, or the audio digital signal of the class D power amplifier can be obtained and then converted into an audio analog signal through a digital-to-analog conversion chip.

[0062] Step S200 : Based on the input amplitude of the audio analog signal, generate a current control signal IBCON proportional to the input amplitude of the audio analog signal.

[0063] Optional, see Figure 8 , step S200 specifically includes:

[0064] Step S210: amplifying the audio analog signal and converting it into an audio differential signal having two single-ended signals;

[0065] It should be understood that the audio analog signal can be amplified and converted into an audio differential signal and output by the audio pre-amplifier circuit 400 of the second aspect of this embodiment.

[0066] Step S220: comparing the voltage peak values ​​of the two single-ended signals of the audio differential signal and generating a comparison result;

[0067] It should be understood that the peak values ​​of the voltages of the two single-ended signals of the audio differential signal can be compared by the peak detection output module 100 in the embodiment of the present invention.

[0068] Step S230: outputting a single-ended signal with a larger voltage peak value according to the comparison result;

[0069] It should be understood that a single-ended signal with a relatively large voltage peak value can be output by the peak detection output module 100 in the embodiment of the present invention.

[0070] Step S240: converting the single-ended signal into a current control signal IBCON in direct proportion.

[0071] It should be understood that the current conversion module 200 in the embodiment of the present invention can convert a single-ended signal with a larger voltage peak value into a current control signal IBCON that is directly proportional to the single-ended signal.

[0072] It should be understood that the audio analog signal is positively correlated with the audio differential signal, that is, the input amplitude of the audio analog signal is positively correlated with the size of the single-ended signal of the audio differential signal, and the single-ended signal is in direct proportion to the current control signal, so the input amplitude of the audio analog signal is in proportional to the current control signal.

[0073] Step S300: superimposing the current control signal IBCON with the reference current IBOSC of the class D power amplifier oscillator and outputting the superimposed current to the class D power amplifier oscillator.

[0074] It should be understood that the carrier frequency of the class D power amplifier oscillator is inversely proportional to the reference current IBOSC. By superimposing the current control signal IBCON and the reference current IBOSC as a new current to control the carrier frequency, the carrier frequency is inversely proportional to the current control signal IBCON, that is, the carrier frequency is inversely proportional to the input amplitude of the audio analog signal, that is, the carrier frequency of the class D power amplifier oscillator is adjusted according to the input amplitude of the audio analog signal, so that when the input amplitude of the audio analog signal becomes smaller, the carrier frequency becomes larger and the distortion of the signal is reduced, and when the input amplitude of the audio analog signal becomes larger, the carrier frequency becomes smaller and the efficiency of the circuit is improved, which solves the problem that the traditional technical solution cannot adapt to the change of the input amplitude of the audio signal, resulting in large signal distortion or low overall circuit efficiency.

[0075] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A class D power amplifier oscillator circuit, characterized in that: include: A peak detection output module for receiving an audio differential signal, comparing voltage peaks of two single-ended signals in the audio differential signal, and outputting the single-ended signal with the larger voltage peak; A current conversion module connected to the peak detection output module, used for converting the single-ended signal with a larger voltage peak value into a current control signal proportional to the input amplitude of the audio differential signal; as well as An oscillation module connected to the current conversion module and used to adjust the carrier frequency during oscillation according to the current control signal; The peak detection output module includes: a first comparator, a first inverter, a first controllable switch and a second controllable switch, wherein the positive input terminal of the first comparator and the first terminal of the first controllable switch are connected together as the first input terminal of the peak detection output module, the negative input terminal of the first comparator and the first terminal of the second controllable switch are connected together as the second input terminal of the peak detection output module, the output terminal of the first comparator and the control terminal of the second controllable switch are connected to the input terminal of the first inverter, the output terminal of the first inverter is connected to the control terminal of the first controllable switch, and the second terminal of the first controllable switch and the second terminal of the second controllable switch are connected together as the output terminal of the peak detection output module; wherein the first comparator is a voltage comparator.

2. The class D power amplifier oscillator circuit according to claim 1, characterized in that: The current conversion module comprises: A current conversion unit connected to the output end of the peak detection output module and used for converting the single-ended signal with a larger voltage peak value into a current control signal; and A current ratio amplification unit connected to the output end of the current conversion unit and the input end of the oscillation module, and used to amplify the current control signal according to a preset ratio.

3. The class D power amplifier oscillator circuit according to claim 2, characterized in that: The current conversion unit includes: a first operational amplifier, a second operational amplifier, a first resistor and a first transistor, the positive phase input terminal of the first operational amplifier is used to access the reference voltage, the negative phase input terminal of the first operational amplifier and the output terminal of the first operational amplifier are commonly connected to the first end of the first resistor, the second end of the first resistor is connected to the negative phase input terminal of the second operational amplifier and the input terminal of the first transistor, the positive phase input terminal of the second operational amplifier is connected to the output terminal of the peak detection output module, the output terminal of the second operational amplifier is connected to the control terminal of the first transistor, and the output terminal of the first transistor serves as the output terminal of the current conversion unit.

4. The class D power amplifier oscillator circuit as claimed in claim 2, characterized in that: The current ratio amplification unit includes: a second transistor and a third transistor, the control end of the second transistor, the input end of the second transistor and the control end of the third transistor are connected together as the input end of the current ratio amplification unit, the output end of the second transistor is connected to the input end of the third transistor, and the output end of the third transistor serves as the output end of the current ratio amplification unit.

5. The class D power amplifier oscillator circuit according to claim 1, characterized in that: The oscillation module includes: a fourth transistor, a fifth transistor, a sixth transistor, a seventh transistor, an eighth transistor, a ninth transistor, a tenth transistor, an eleventh transistor, a first capacitor, a third controllable switch, a fourth controllable switch, a second comparator and a second inverter. The input end of the fourth transistor, the control end of the fourth transistor, the control end of the fifth transistor and the control end of the sixth transistor are connected together as the input end of the oscillation module. The input end of the oscillation module is connected to a current control signal and a reference current. The output end of the fourth transistor, the output end of the fifth transistor, the output end of the sixth transistor, the second end of the first capacitor and the output end of the eleventh transistor are connected to the ground. The input end of the fifth transistor and the control end of the seventh transistor, the output end of the seventh transistor and the control end of the eighth transistor are connected together. The input end of the seventh transistor and the input end of the eighth transistor are connected together. The output end of the transistor is connected to the input end of the ninth transistor, the control end of the ninth transistor, the control end of the tenth transistor, the output end of the second comparator, the control end of the third controllable switch and the input end of the second inverter are connected in common, the output end of the ninth transistor, the input end of the tenth transistor, the first end of the first capacitor, the input end of the eleventh transistor and the non-inverting input end of the second comparator are connected in common, the output end of the tenth transistor is connected to the input end of the sixth transistor, the first end of the third controllable switch is externally connected to a first reference voltage, the second end of the third controllable switch and the second end of the fourth controllable switch are commonly connected to the inverting input end of the second comparator, the first end of the fourth controllable switch is externally connected to a second reference voltage, the control end of the fourth controllable switch, the control end of the eleventh transistor and the output end of the second inverter are commonly connected, and the output end of the inverter serves as the output end of the oscillation module.

6. A class D power amplifier oscillator, characterized in that: include: An audio preamplifier circuit, used for receiving an audio analog signal, amplifying the audio analog signal and outputting an audio differential signal; and The class D power amplifier oscillator circuit according to any one of claims 1 to 5, wherein the class D power amplifier oscillator circuit is connected to the audio pre-amplifier circuit.

7. The class D power amplifier oscillator as claimed in claim 6, characterized in that: The audio pre-amplifier circuit includes: a third operational amplifier, a second capacitor, a third capacitor, a second resistor, a third resistor, a fourth resistor and a fifth resistor, the first end of the second capacitor is connected to the audio analog signal, the second end of the second capacitor is connected to the first end of the second resistor, the second end of the second resistor is connected to the first end of the third resistor and the first input end of the third operational amplifier, the first end of the third capacitor is grounded, the second end of the third capacitor is connected to the first end of the fourth resistor, the second end of the fourth resistor is connected to the second output end of the third operational amplifier and the first end of the fifth resistor, the first differential signal output single end of the third operational amplifier and the second end of the third resistor are connected together as the first single-ended signal output end of the audio pre-amplifier circuit, and the second differential signal output single end of the third operational amplifier and the second end of the fifth resistor are connected together as the second single-ended signal output end of the audio pre-amplifier circuit.

8. A frequency adjustment method for a class D power amplifier oscillator as claimed in claim 6 or 7, characterized in that: include: Get the audio analog signal input by the Class D power amplifier; Based on the input amplitude of the audio analog signal, generating a current control signal that is proportional to the input amplitude of the audio analog signal; The current control signal is superimposed on a reference current of a class D power amplifier oscillator and then output to the class D power amplifier oscillator.

9. The frequency adjustment method of the class D power amplifier oscillator according to claim 8, characterized in that: The step of generating a current control signal proportional to the input amplitude of the audio analog signal based on the input amplitude of the audio analog signal comprises: amplifying the audio analog signal and converting it into an audio differential signal having two single-ended signals; Comparing the voltage peak values ​​of the two single-ended signals of the audio differential signal and generating a comparison result; Output a single-ended signal with a larger voltage peak value according to the comparison result; The single-ended signal is converted into a current control signal in direct proportion.

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