Implementation method of novel low-distortion digital modulation direct drive power amplifier device

Abstract

The invention provides an implementation method of a novel low-distortion digital modulation direct drive power amplifier device, and relates to the field of plasma generation radio frequency power supplies, the method realizes acquisition of modulation waveform signals through a delta-sigma oversampling technology, and realizes further improvement of the sampling rate of the modulation waveform signals through a PDM pulse distribution unit interpolation filter. The exciter can generate multi-phase PDM modulation waveform pulses and carrier wave driving pulses, and directly drives the power amplifier module to complete carrier wave generation and waveform modulation. Multi-phase PDM modulation can achieve a better modulation waveform THD (Total Harmonic Distortion) index, it is ensured that a modulation waveform signal is basically subjected to distortion-free recovery, but in order to reduce the complexity of a system and give consideration to the modulation waveform total harmonic distortion index, the multi-phase PDM modulation is generally controlled within 12 phases. In addition, a modulation waveform signal is divided into a plurality of equal-amplitude PDM square wave signals by a multi-phase PDM modulation and superposition technology, so that the power amplifier works in an on-off state, and the efficiency of the power amplifier is improved.

Description

Technical Field

[0001] The invention relates to the field of plasma-generated radio frequency power supply, and in particular to a method for realizing a novel low-distortion digital modulation direct-drive power amplifier device. Background Art

[0002] Plasma is a form of matter mainly composed of free electrons and charged particles. It is widely present in the universe and is called the fourth state of matter. It has high electrical conductivity and is rich in a large number of high-energy electrons, ions, and a large number of active substances. It has a wide range of applications in food processing, metal smelting, environmental governance, biomedicine, semiconductor etching and thin film deposition, surface cleaning, aerospace, and other fields. In the actual application of plasma, the special power supply used to generate plasma is the core. It is generally composed of four categories: high-voltage DC power supply, high-voltage pulse power supply, high-frequency AC power supply, and radio frequency power supply. Among them, radio frequency power supply is mainly used in the nuclear technology industry and the semiconductor manufacturing industry. When the radio frequency power supply excites and generates plasma, a large reflection signal will be generated in the early stage of plasma establishment due to the drastic change of load impedance. The reflection signal is very harmful to the radio frequency power supply. In order to reduce the harm of the reflection signal to the radio frequency power supply, the radio frequency signal is generally modulated by establishing an initial trapezoidal wave or exponential function wave to reduce the accumulation of reflection energy in the initial stage of plasma establishment in a short time.

[0003] At present, there are relevant patents in the industry that disclose patented technologies for low-distortion power amplifiers, such as patent No. 202110545047.6, which discloses a method for implementing a high-power, low-distortion Class D power amplifier based on a high-performance MCU. The main steps are: 1) Select and display the input signal mode. 2) Preprocess the input signal to obtain audio data. 3) Transmit the audio data to the STM32F407 minimum system and output PWM to the half-bridge driver module. 4) Every two half-bridge driver modules drive a full-bridge power amplifier to achieve power amplification of small signals. 5) Filter the output of the full-bridge power amplifier. 6) Current sampling of the output after the low-pass filter is performed and fed back to the minimum system. 7) According to the output feedback signal, the digital filter is set to filter the audio data in 1). 8) Repeat 2)-7) to achieve negative feedback control of the output. The present invention solves the problem of instantaneous noise interference when the Class D power amplifier is powered on at a relatively low cost, and can also compensate for high frequencies through IIR to solve the problem of high requirements for filters for Class D power amplifiers when the switching frequency is low.

[0004] The patent of this invention provides a method for realizing a new type of low-distortion digital modulation direct-drive power amplifier device. Through this method, a new technology, new system, and new architecture of digital modulation direct-drive plasma to generate RF power can be realized. Summary of the invention

[0005] In view of the problems in the prior art, the purpose of the present invention is to provide a new method for realizing a low-distortion digital modulation direct-drive power amplifier device to solve the problem described in the above background technology: this method can realize a new technology, new system, and new architecture of digital modulation direct-drive plasma to generate RF power.

[0006] The present invention adopts the following technical solutions to achieve: a method for realizing a novel low-distortion digital modulation direct drive power amplifier device, comprising:

[0007] An exciter, which collects and processes signals of different waveform formats and generates multi-phase PDM modulation waveform pulses and carrier drive pulses;

[0008] A PDM pulse distribution unit, through which the sampling rate of the modulation waveform signal is further improved;

[0009] Among them, this method realizes the acquisition of modulated waveform signals through Δ-Σ oversampling technology, and further improves the sampling rate of the modulated waveform signals through the interpolation filter of the PDM pulse distribution unit. The exciter can generate multi-phase PDM modulated waveform pulses and carrier drive pulses, and directly drive the power amplifier module to complete carrier generation and waveform modulation.

[0010] As a preferred technical solution of the present invention, the exciter completes the acquisition and processing of signals of different waveform formats, and generates n-way multi-phase PDM modulated waveform drive signals, generates RF drive signals, switches the reference of internal and external clocks, samples and acquires RF voltage and current, and samples and acquires power supply of the power amplifier module.

[0011] As a preferred technical solution of the present invention, the PDM pulse distribution unit completes the distribution of n-channel PDM modulation waveform driving signals generated by the exciter, and distributes them to the BUCK circuit of the power amplifier module unit to complete the generation of the modulation waveform modulation voltage.

[0012] As a preferred technical solution of the present invention, the implementation method of the new low-distortion digital modulation direct-drive power amplifier device also includes a radio frequency drive distribution unit, which completes the distribution of a radio frequency drive signal generated by the exciter and sends it to the H-bridge circuit of the power amplifier module unit to complete the generation of the carrier voltage.

[0013] As a preferred technical solution of the present invention, the implementation method of the novel low-distortion digital modulation direct drive power amplifier device also includes a matching transformation unit, which completes impedance change and suppression of specific frequencies through a T-type impedance matching and suppression network.

[0014] As a preferred technical solution of the present invention, the implementation method of the novel low-distortion digital modulation direct-drive power amplifier device also includes a power supply unit, which completes the external power input rectification and filtering to generate the voltage required for the amplifier module unit BUCK input and the auxiliary power required by other systems of the whole machine.

[0015] As a preferred technical solution of the present invention, the implementation method of the novel low-distortion digital modulation direct drive power amplifier device also includes a control unit, which completes the status reading and logic control of all subsystems of the system as well as external interlocking control and remote control.

[0016] As a preferred technical solution of the present invention, the remote control adopts ordinary IO port control.

[0017] The beneficial effects of the present invention are:

[0018] The exciter disclosed in the present invention receives modulated waveform signals of various formats (analog signal, digital signal, text signal) sent from the outside, wherein the digital signal and the text signal are digital modulated waveform signals, and the sampling rate thereof is generally 48kHz. The analog modulated waveform signal is converted to digital by a modulated waveform AD chip, and the sampling rate of the modulated waveform AD chip is generally 96kHz. In order to facilitate FPGA processing and save FPGA logic resources, the sampling rate of the modulated waveform is uniformly selected as 48kHz. Then the digital modulated waveform signal is uniformly converted to 48kHz by the modulated waveform rate / format conversion and sent to the FPGA. The current input modulated waveform format can be selected by the host computer / dip switch. The phase number N can be selected by the host computer / dip switch. The 48kHz modulated waveform signal is increased to 0.048*N kHz by an interpolation filter inside the FPGA. Because the frequency range of the radio frequency is 500kHz to 15MHz, the higher the phase number is, the easier it is to filter out the sampling switch frequency. The interpolated 0.048*N KHz modulated waveform signal is compared with a single-phase triangle wave signal to obtain a PDM pulse signal whose pulse width is proportional to the amplitude of the modulated waveform. If 6-phase modulation is selected here, the frequency of the triangle wave signal is 48kHz×6=288kHz.

[0019] As the specification of the present invention Figure 2 And the instruction manual Figure 3 As shown in the instruction manual, Figure 2 And the instruction manual Figure 3The modulation waveform signal is input into different comparators at the same time. The phase difference between the adjacent N triangle wave signals is 360° / N. After passing through the comparator, the modulation waveform multi-phase PDM modulation is realized. The modulation waveform components are in parallel relationship, and the high-frequency noise signal generated by the modulation is in frequency superposition relationship. Therefore, the harmonic frequency is increased, which is more conducive to the miniaturization of the low-pass filter later. Multi-phase PDM modulation can achieve better modulation waveform THD (Total Harmonic Distortion) index, ensuring that the modulation waveform signal is basically restored without distortion. However, in order to reduce the complexity of the system and take into account the total harmonic distortion index of the modulation waveform, the multi-phase PDM modulation is generally controlled within 12 phases. In addition, the multi-phase PDM modulation and superposition technology divides the modulation waveform signal into multiple equal-amplitude PDM square wave signals, so that the power amplifier works in a switching state, which improves the efficiency of the power amplifier. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0021] Figure 1 This is a block diagram of the system principle of the present invention;

[0022] Figure 2 The present invention is a block diagram of the PDM principle for the modulation waveform processing of the exciter;

[0023] Figure 3 The multi-phase PDM generation principle block diagram of the present invention is shown;

[0024] Figure 4 The single-phase PDM signal generation principle diagram of the present invention;

[0025] Figure 5 The three-phase PDM signal generation principle diagram of the present invention;

[0026] Figure 6 The three-phase PDM signal generation principle diagram of the present invention;

[0027] Figure 7 This is a block diagram of the PDM modulation principle of a single power amplifier module of the present invention;

[0028] Figure 8 This is a principle block diagram of the H-bridge of a single power amplifier module of the present invention. DETAILED DESCRIPTION

[0029] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific diagrams. It should be noted that the embodiments in this application and the features in the embodiments can be combined with each other without conflict.

[0030] Example 1

[0031] See also Figure 1 , is a system principle block diagram of a new method for realizing a low-distortion digital modulation direct drive power amplifier device,

[0032] A novel method for realizing a low-distortion digital modulation direct drive power amplifier device comprises: an exciter, which collects and processes signals of different waveform formats and generates multi-phase PDM modulation waveform pulses and carrier drive pulses;

[0033] A PDM pulse distribution unit, through which the sampling rate of the modulation waveform signal is further improved;

[0034] Among them, this method realizes the acquisition of modulated waveform signals through Δ-Σ oversampling technology, and further improves the sampling rate of the modulated waveform signals through the interpolation filter of the PDM pulse distribution unit. The exciter can generate multi-phase PDM modulated waveform pulses and carrier drive pulses, and directly drive the power amplifier module to complete carrier generation and waveform modulation.

[0035] See also Figure 1 The device includes an exciter, a control unit, a PDM pulse distribution unit, a radio frequency drive distribution unit, a power supply unit, a power amplifier module unit, a matching conversion unit, a power detection unit, a matching box, a cavity, etc.

[0036] Please continue reading Figure 1 As shown, the exciter mainly completes the acquisition and processing of signals of different waveform formats (analog signals, digital signals, text signals) and generates n-channel multi-phase PDM modulated waveform drive signals, RF drive signal generation, internal and external clock reference switching, RF voltage and current sampling and acquisition, and power amplifier module power sampling and acquisition and other functions.

[0037] Please continue reading Figure 1 As shown, the PDM pulse distribution unit mainly completes the distribution of n-channel PDM modulation waveform driving signals generated by the exciter, and distributes them to the BUCK (step-down conversion circuit) circuit of the power amplifier module unit to complete the generation of the modulation waveform modulation voltage.

[0038] Please continue reading Figure 1 As shown, the RF drive distribution unit mainly distributes one RF drive signal generated by the exciter and sends it to the H-bridge circuit of the power amplifier module unit to complete the generation of the carrier voltage.

[0039] Please continue reading Figure 1 As shown, the matching transformation unit achieves impedance change and suppression of specific frequencies through a T-type impedance matching and suppression network.

[0040] Please continue reading Figure 1As shown, the power supply unit mainly completes the external power input rectification and filtering to generate the 400V voltage required for the amplifier module unit BUCK input and the auxiliary power supply (such as ±15V, +5V, etc.) required by other systems of the whole machine.

[0041] Please continue reading Figure 1 As shown, the control unit completes the status reading and logic control of all subsystems of the system, as well as external interlocking control and remote control. In order to ensure the reliability of the system, the remote control adopts ordinary IO port control instead of communication control, which can greatly reduce abnormal shutdown or poor broadcast caused by unreliable communication.

[0042] Example 2

[0043] See also Figure 2-8 This embodiment is similar to the above-mentioned embodiment 1, and the similarities are not described in this embodiment. The specific differences are:

[0044] See also Figure 2 The exciter of the present invention receives modulated waveform signals of various formats (analog signal, digital signal, text signal) sent from the outside, wherein the digital signal and the text signal are digital modulated waveform signals, and the sampling rate thereof is generally 48kHz. The analog modulated waveform signal is converted to digital by the modulated waveform AD chip, and the sampling rate of the modulated waveform AD chip is generally 96kHz. In order to facilitate FPGA processing and save FPGA logic resources, the sampling rate of the modulated waveform is uniformly selected as 48kHz. Then the digital modulated waveform signal is uniformly converted to 48kHz by the modulated waveform rate / format conversion and sent to the FPGA. The current input modulated waveform format can be selected by the host computer / dip switch. The phase number N can be selected by the host computer / dip switch. The sampling rate of the 48kHz modulated waveform signal is increased to 0.048*N kHz by the interpolation filter inside the FPGA. Because the frequency range of the radio frequency is 500kHz to 15MHz, the higher the phase number is selected, the easier it is to filter out the sampling switch frequency. The interpolated 0.048*N KHz modulated waveform signal is compared with the single-phase triangle wave signal to obtain a PDM pulse signal whose pulse width is proportional to the amplitude of the modulated waveform. If 6-phase modulation is selected here, the frequency of the triangle wave signal is 48kHz×6=288kHz.

[0045] See also Figure 3The modulation waveform signal of the present invention is simultaneously input into different comparators, and the phase difference between the adjacent N triangle wave signals is 360° / N. After passing through the comparator, the multi-phase PDM modulation of the modulation waveform is realized. The modulation waveform components are in a parallel relationship, and the high-frequency noise signal generated by the modulation is in a frequency superposition relationship, thereby increasing the harmonic frequency, which is more conducive to the miniaturization of the subsequent low-pass filter. The multi-phase PDM modulation can achieve a better modulation waveform THD (Total Harmonic Distortion) index, ensuring that the modulation waveform signal is basically restored without distortion. However, in order to reduce the complexity of the system and take into account the total harmonic distortion index of the modulation waveform, the multi-phase PDM modulation is generally controlled within 12 phases. In addition, the multi-phase PDM modulation and superposition technology divides the modulation waveform signal into multiple equal-amplitude PDM square wave signals, so that the power amplifier works in a switching state, which improves the efficiency of the power amplifier.

[0046] See also Figure 4 The present invention generates a PDM pulse signal whose pulse width is proportional to the amplitude of the modulation waveform signal by comparing the modulation waveform signal with the triangle wave signal.

[0047] Example 3

[0048] Please continue reading Figure 2-8 This embodiment is similar to the above-mentioned embodiment 1 and embodiment 2, and the similarities are not described in this embodiment. The specific differences are:

[0049] See also Figure 5 In the present invention, three adjacent triangle wave signals are 120° apart, which is equivalent to each triangle wave signal being 120° apart. When the modulation waveform amplitude is higher than the triangle wave amplitude at a certain moment, the number is the amplitude of the PDM pulse. Because it is a three-phase PDM, the maximum PDM amplitude after the final synthesis is 3 and the minimum is 0. The higher the PDM amplitude, the larger the modulation waveform signal, and vice versa. The smaller the PDM amplitude, the smaller the modulation waveform signal.

[0050] See also Figure 6 In the present invention, the phase difference between the nine adjacent triangle wave signals is 40°, which is equivalent to that each triangle wave signal is 40° apart. When the modulation waveform amplitude is higher than the triangle wave amplitude at a certain moment, the number is the amplitude of the PDM pulse. Because of the 9-phase PDM, the maximum PDM amplitude after the final synthesis is 9 and the minimum is 0. The higher the PDM amplitude, the larger the modulation waveform signal, and vice versa.

[0051] The exciter generates a multi-phase PDM modulated waveform pulse signal, and the power amplifier module completes the modulation of the multi-phase PDM signal. Multi-phase here generally refers to three phases, four phases, six phases, nine phases, twelve phases, and sixteen phases.

[0052] Example 4

[0053] Please continue reading Figure 2-8 This embodiment has the same features as the above-mentioned Embodiment 1, Embodiment 2 and Embodiment 3, which will not be described in this embodiment. The specific differences are:

[0054] See also Figure 7 , Figure 7 N in the figure represents the number of phases of a single module. In order to reduce the complexity of PDM modulation of a single power amplifier module and take into account the flexible application of a single module (a single module can independently become a system power amplifier), N = 3 or 4 is generally selected. After the number of phases of a single module is determined, the number of phases of the PDM of the whole machine is an integer multiple of 3 or 4. Let's take the single module PDM phase number 4 as an example. In order to obtain better modulation waveform distortion, we can choose 16-phase / 12-phase PDM for the whole machine, so that every 4 / 3 power amplifier modules are a group.

[0055] When there is no modulation waveform modulation, the carrier level is modulated by adjusting the fixed duty cycle of PDM. The higher the duty cycle, the higher the carrier level, and the lower the duty cycle, the lower the carrier level. The waveform modulation formula is as follows:

[0056] S AM (t) = [A0 + A m cosΩt](cosω c t+θ c )=A0[1+mcosΩt](cosω c t+θ c ) (Formula 1)

[0057] in m represents the modulation depth.

[0058] Because the input of BUCK is 400V, the carrier level must not exceed 200V to meet ±100% modulation, so the PDM duty cycle does not exceed 50%. The carrier level is equivalent to adding a DC bias to the modulation waveform. The carrier level and the modulation waveform level are superimposed and compared with the triangle wave to generate the PDM pulse, which contains the carrier amplitude information and modulation waveform information. Then the frequency information and phase information of the carrier are mainly completed by the inverter H-bridge circuit after the BUCK circuit in the power amplifier module. The exciter outputs an RF drive signal that is distributed to each power amplifier module through the RF drive distribution board to complete the control of the H-bridge circuit. The frequency of the H-bridge drive pulse signal is the frequency of the carrier. If synchronization with other devices is required, the rising edge of the H-bridge drive pulse signal needs to be synchronized with the synchronization signal.

[0059] See also Figure 8 , the present invention Figure 8The dead time of the H-bridge and the H-bridge driving pulse signal are generated by the RF driving signal after the processing circuit, and the dead time is controlled within tens of ns, meeting the requirements of the RF power supply frequency range of 500kHz to 15MHz for plasma generation.

[0060] A single power amplifier module can be designed to output 2.5kW, supporting 3-phase / 4-phase PDM modulation, and 3 / 4 power amplifier modules support 9-phase / 12-phase / 16-phase PDM modulation. According to the power requirements of the whole machine, the number of combined modules can achieve an output power of 2kW to 400kW for the whole machine. If higher power output is required, it can be achieved to MW level output power through parallel connection. Through multi-phase PDM modulation and switch amplifiers, high-efficiency and low-distortion RF power supply can be achieved, with power amplifier efficiency > 90% and distortion < 1%.

[0061] In addition, the PDM described in the present invention is a modulation method for providing analog signals in the digital field. In the PDM signal, logic "1" represents a single pulse, and logic "0" represents no pulse. Usually logic "1" and logic "0" are discontinuous, and logic "1" is relatively evenly distributed in each modulation signal cycle. Among them, a single pulse does not represent the amplitude, but the density of a series of pulses corresponds to the amplitude in the analog signal. A PDM signal composed entirely of "1" corresponds to a voltage with a positive amplitude; a PDM signal composed entirely of "0" corresponds to a voltage with a negative amplitude; and a PDM signal composed alternately of "1" and "0" corresponds to an intermediate amplitude.

[0062] The basic principles, main features and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and the description in the specification are only to illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A novel method for realizing a low-distortion digital modulation direct drive power amplifier device, characterized in that: include: An exciter, which collects and processes signals of different waveform formats and generates multi-phase PDM modulation waveform pulses and carrier drive pulses; A PDM pulse distribution unit, through which the sampling rate of the modulation waveform signal is further improved; Among them, this method realizes the acquisition of modulated waveform signals through Δ-Σ oversampling technology, and further improves the sampling rate of the modulated waveform signals through the interpolation filter of the PDM pulse distribution unit. The exciter can generate multi-phase PDM modulated waveform pulses and carrier drive pulses, and directly drive the power amplifier module to complete carrier generation and waveform modulation.

2. The method for implementing a novel low-distortion digital modulation direct drive power amplifier device according to claim 1, characterized in that: The exciter completes the acquisition and processing of signals of different waveform formats, and generates n-way multi-phase PDM modulated waveform drive signals, generates RF drive signals, switches the reference of internal and external clocks, samples and acquires RF voltage and current, and samples and acquires power supply of the power amplifier module.

3. The method for implementing a novel low-distortion digital modulation direct drive power amplifier device according to claim 1, characterized in that: The PDM pulse distribution unit distributes the n-channel PDM modulation waveform driving signals generated by the exciter, and distributes the signals to the BUCK circuit of the power amplifier module unit to generate the modulation waveform modulation voltage.

4. The method for implementing a novel low-distortion digital modulation direct drive power amplifier device according to claim 1, characterized in that: The implementation method of the novel low-distortion digital modulation direct drive power amplifier device also includes a radio frequency drive distribution unit, which completes the distribution of a radio frequency drive signal generated by the exciter and sends it to the H-bridge circuit of the power amplifier module unit to complete the generation of the carrier voltage.

5. The method for implementing a novel low-distortion digital modulation direct drive power amplifier device according to claim 2, characterized in that: The implementation method of the novel low-distortion digital modulation direct drive power amplifier device also includes a matching transformation unit, and the matching transformation unit completes impedance change and suppression of specific frequencies through a T-type impedance matching and suppression network.

6. The method for implementing a novel low-distortion digital modulation direct drive power amplifier device according to claim 5, characterized in that: The implementation method of the novel low-distortion digital modulation direct drive power amplifier device also includes a power supply unit, which completes external power rectification and filtering to generate the voltage required for the amplifier module unit BUCK input and the auxiliary power required by other systems of the whole machine.

7. The method for implementing a novel low-distortion digital modulation direct drive power amplifier device according to claim 1, characterized in that: The implementation method of the novel low-distortion digital modulation direct drive power amplifier device also includes a control unit, which completes the status reading and logic control of all subsystems of the system as well as external interlocking control and remote control.

8. The method for implementing a novel low-distortion digital modulation direct drive power amplifier device according to claim 7, characterized in that: The remote control adopts common IO port control.

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