Implementation method of a new type of digital modulation direct drive power amplifier device with low distortion

Abstract

The present invention provides a method for implementing a novel low-distortion digital modulation direct-drive power amplifier device, which relates to the field of radio frequency power supplies for plasma generation. This method realizes the acquisition of modulation waveform signals through Δ-Σ oversampling technology, and further improves the sampling rate of modulation waveform signals through the interpolation filter in the PDM pulse distribution unit. The exciter can generate multi-phase PDM modulation waveform pulses and carrier drive pulses, directly driving the power amplifier module to complete carrier generation and waveform modulation; multi-phase PDM modulation can achieve better modulation waveform THD (Total Harmonic Distortion) indicators, ensuring that the modulation waveform signals are recovered with basically no distortion. However, in order to reduce the complexity of the system and take into account the total harmonic distortion index of the modulation waveform, multi-phase PDM modulation is generally controlled within 12 phases. In addition, multi-phase PDM modulation and superposition technology divide the modulation waveform signals into multiple equal-amplitude PDM square wave signals, enabling the power amplifier to operate in a switching state and improving the efficiency of the power amplifier.

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] Aiming at the problems in the prior art, the purpose of the present invention is to provide a method for realizing a new type of low-distortion digital modulation direct-drive power amplifier device, and solve the problems described in the above background technology: through this method, a digital modulation direct-drive plasma generating radio frequency power supply with a new technology, new system and new architecture can be realized.

[0006] The present invention adopts the following technical solutions to realize: A method for realizing a new type of low-distortion digital modulation direct-drive power amplifier device, including:

[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 the modulation waveform signal through Δ-Σ oversampling technology, and further improves the sampling rate of the modulation waveform signal through the interpolation filter in the PDM pulse distribution unit. The exciter can generate multi-phase PDM modulation 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-channel multi-phase PDM modulation waveform drive signals, the generation of radio frequency drive signals, the reference switching of internal and external clocks, the sampling acquisition of radio frequency voltage and current, and the sampling acquisition of the 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 the n-channel PDM modulation waveform drive signals generated by the exciter, and the distributed signals are sent 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 method for realizing the new type of low-distortion digital modulation direct-drive power amplifier device further 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 method for realizing the new type of low-distortion digital modulation direct-drive power amplifier device further includes a matching transformation unit, which completes impedance change and suppression of specific frequencies through T-type impedance matching and suppression network.

[0014] As a preferred technical solution of the present invention, the implementation method of the new low-distortion digital modulation direct-drive power amplifier device further includes a power supply unit, and the power supply unit generates the voltage required for the input of the BUCK of the power amplifier module unit and the auxiliary power supply required for other systems of the whole machine after rectifying and filtering the externally input power.

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

[0016] As a preferred technical solution of the present invention, the remote control is controlled by a common IO port.

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

[0018] The exciter disclosed in the present invention receives modulation waveform signals of multiple formats (analog signals, digital signals, text signals) sent from the outside. Among them, the digital signals and text signals are digital modulation waveform signals, and their sampling rate is generally 48 kHz. The analog modulation waveform signal is converted from analog to digital through a modulation waveform AD chip, and the sampling rate of the modulation waveform AD chip is generally 96 kHz. In order to facilitate the processing of the FPGA and save the FPGA logic resources, here the modulation waveform sampling rate is uniformly selected as 48 kHz. Then, the digital modulation waveform signal is uniformly converted to 48 kHz after the modulation waveform rate / format conversion and sent to the FPGA. The current input modulation waveform format can be selected through the upper computer / dial switch. The number of phases N can be selected through the upper computer / dial switch. The 48 kHz modulation waveform signal is upsampled to 0.048*N kHz through an interpolation filter inside the FPGA. Since the frequency range of the radio frequency is 500 kHz to 15 MHz, the higher the number of phases selected, the easier it is to filter out the sampling switch frequency. The interpolated 0.048*N KHz modulation waveform signal is compared with a single-phase triangular wave signal to obtain a PDM pulse signal whose pulse width is proportional to the amplitude of the modulation waveform. Here, if 6-phase modulation is selected, then the frequency of the triangular wave signal is 48 kHz × 6 = 288 kHz.

[0019] As shown in the attached Figure 2 and the attached Figure 3 of the specification of the present invention, the attached Figure 2 and the attached Figure 3The modulated waveform signal is simultaneously input into different comparators. The phase difference between adjacent ones of the N triangular wave signals is 360° / N respectively. After passing through the comparators, multi-phase PDM modulation of the modulated waveform is achieved. The components of the modulated waveform are in a parallel relationship, and the high-frequency noise signals generated by the modulation are in a frequency superposition relationship. Therefore, the harmonic frequency is increased, which is more conducive to the miniaturization of the subsequent low-pass filter. Multi-phase PDM modulation can achieve better Total Harmonic Distortion (THD) indicators of the modulated waveform, ensuring that the modulated waveform signal is restored with basically no distortion. However, in order to reduce the complexity of the system and take into account the total harmonic distortion index of the modulated waveform, multi-phase PDM modulation is generally controlled within 12 phases. In addition, multi-phase PDM modulation and superposition technology divide the modulated waveform signal into multiple equal-amplitude PDM square wave signals, enabling the power amplifier to operate in a switching state and improving the efficiency of the power amplifier. Brief Description of the Drawings

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

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

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

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

[0024] Figure 4 It is a schematic diagram of the single-phase PDM signal generation principle of the present invention;

[0025] Figure 5 It is a schematic diagram of the three-phase PDM signal generation principle of the present invention;

[0026] Figure 6 It is a schematic diagram of the three-phase PDM signal generation principle of the present invention;

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

[0028] Figure 8 It is a block diagram of the H-bridge of the single power amplifier module of the present invention. Detailed Embodiments

[0029] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific illustrations. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0030] Embodiment 1

[0031] Please refer to Figure 1 , which is a system principle block diagram of an implementation method for a new type of low-distortion digital modulation direct drive power amplifier device.

[0032] An implementation method for a new type of low-distortion digital modulation direct drive power amplifier device includes: an exciter that 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 that further improves the sampling rate of the modulation waveform signal through the PDM pulse distribution unit.

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

[0035] Please refer to Figure 1 , this 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 transformation unit, a power detection unit, a matching box, a cavity, etc.

[0036] Please continue to refer to 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 functions such as n-channel multi-phase PDM modulation waveform drive signals, generation of radio frequency drive signals, switching of internal and external clock references, sampling and acquisition of radio frequency voltage and current, and sampling and acquisition of the power supply of the power amplifier module.

[0037] Please continue to refer to Figure 1 As shown, the PDM pulse distribution unit mainly completes the distribution of the n-channel PDM modulation waveform drive signals generated by the exciter, and distributes them into 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 to refer to Figure 1 As shown, the radio frequency drive distribution unit mainly completes the distribution of a single radio frequency drive signal generated by the exciter, and sends it into the H-bridge circuit of the power amplifier module unit to complete the generation of the carrier voltage.

[0039] Please continue to refer to Figure 1 As shown, the matching transformation unit completes impedance change and suppression of specific frequencies through T-type impedance matching and suppression networks.

[0040] Please continue to refer to Figure 1As shown in the figure, the power supply unit mainly generates the 400V voltage required for the input of the power amplifier module unit BUCK after rectifying and filtering the external incoming power, as well as the auxiliary power supplies required for other systems of the whole machine (such as power supplies of ±15V, +5V, etc.).

[0041] Please continue to refer to Figure 1 As shown in the figure, the control unit completes the status reading and logic control of all subsystems of the system, as well as external interlock control and remote control. Here, to ensure the reliability of the system, the remote control is controlled by ordinary IO ports instead of communication form control, which can greatly reduce the abnormal shutdown or poor broadcast caused by the unreliability of communication.

[0042] Embodiment 2

[0043] Please refer to Figures 2-8 , this embodiment has the same parts as the above Embodiment 1, and the same parts will not be elaborated in this embodiment. The specific differences are as follows:

[0044] Please refer to Figure 2 , the exciter of the present invention receives modulated waveform signals of various formats (analog signals, digital signals, text signals) sent from the outside. Among them, the digital signals and text signals are digital modulated waveform signals, and their sampling rate is generally 48kHz. The analog modulated waveform signal is converted from analog 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 the processing of the FPGA and save the FPGA logic resources, the modulated waveform sampling rate is uniformly selected as 48kHz here. Then, the digital modulated waveform signal is uniformly converted to 48kHz through the modulated waveform rate / format conversion and sent to the FPGA. The current input modulated waveform format can be selected through the upper computer / dial switch. The number of phases N can be selected through the upper computer / dial switch. The 48kHz modulated waveform signal is upsampled to 0.048*N kHz through an interpolation filter inside the FPGA. Since the frequency range of the radio frequency is 500kHz to 15MHz, the higher the number of phases selected, the easier it is to filter out the sampling switch frequency. The upsampled 0.048*N KHz modulated waveform signal is compared with a single-phase triangular wave signal to obtain a PDM pulse signal whose pulse width is proportional to the amplitude of the modulated waveform. Here, if 6-phase modulation is selected, the frequency of the triangular wave signal is 48kHz×6 = 288kHz.

[0045] Please refer to Figure 3, in the present invention, the modulated waveform signal is simultaneously input into different comparators. The phases of N triangular wave signals are respectively different by 360° / N from each other. After passing through the comparators, multi-phase PDM modulation of the modulated waveform is achieved. The components of the modulated waveform are in a parallel relationship, and the high-frequency noise signals generated by the modulation are in a frequency superposition relationship. Therefore, the harmonic frequency is increased, which is more conducive to the miniaturization of the subsequent low-pass filter. Multi-phase PDM modulation can achieve better Total Harmonic Distortion (THD) indicators of the modulated waveform, ensuring that the modulated waveform signal is recovered with basically no distortion. However, in order to reduce the complexity of the system and take into account the total harmonic distortion index of the modulated waveform, multi-phase PDM modulation is generally controlled within 12 phases. In addition, multi-phase PDM modulation and superposition technology divide the modulated waveform signal into multiple equal-amplitude PDM square wave signals, enabling the power amplifier to operate in a switching state and improving the efficiency of the power amplifier.

[0046] Please refer to Figure 4 , in the present invention, a PDM pulse signal whose pulse width is proportional to the amplitude of the modulated waveform signal is generated by comparing the modulated waveform signal with a triangular wave signal.

[0047] Embodiment 3

[0048] Please continue to refer to Figures 2-8 , this embodiment has the same parts as the above Embodiment 1 and Embodiment 2, and the same parts will not be elaborated in this embodiment. The specific differences are as follows:

[0049] Please refer to Figure 5 , in the present invention, the phases of three triangular wave signals are respectively different by 120° from each other, which is equivalent to an interval of 120° for each triangular wave signal. When the number of times the amplitude of the modulated waveform is higher than the amplitude of the triangular wave at a certain moment is the amplitude of the PDM pulse, because it is 3-phase PDM, the maximum amplitude of the synthesized PDM is 3 and the minimum is 0 finally. The higher the PDM amplitude, the larger the modulated waveform signal represents. On the contrary, the smaller it is, the smaller the modulated waveform signal represents.

[0050] Please refer to Figure 6 , in the present invention, the phases of nine triangular wave signals are respectively different by 40° from each other, which is equivalent to an interval of 40° for each triangular wave signal. When the number of times the amplitude of the modulated waveform is higher than the amplitude of the triangular wave at a certain moment is the amplitude of the PDM pulse, because it is 9-phase PDM, the maximum amplitude of the synthesized PDM is 9 and the minimum is 0 finally. The higher the PDM amplitude, the larger the modulated waveform signal represents. On the contrary, the smaller it is, the smaller the modulated waveform signal represents.

[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. Here, multi-phase generally refers to three-phase, four-phase, six-phase, nine-phase, twelve-phase, and sixteen-phase.

[0052] Embodiment 4

[0053] Please continue to refer to Figures 2-8 , this embodiment has the same parts as the above-mentioned Embodiment 1, Embodiment 2, and Embodiment 3, and the same parts will not be elaborated in this embodiment. The specific differences are as follows:

[0054] Please refer to Figure 7 , Figure 7 where N in represents the number of phases of a single module. Generally, 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 be independently 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 whole machine PDM is an integer multiple of 3 or 4. Taking the number of phases of a single module PDM as 4 as an example, in order to obtain a better modulation waveform distortion, our whole machine can select 16-phase / 12-phase PDM, so that every 4 / 3 power amplifier modules form a group.

[0055] When there is no modulation waveform modulation, the modulation of the carrier level is completed by adjusting the fixed duty cycle of the 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] where m represents the modulation depth.

[0058] Since the input of the BUCK is 400V, the carrier level does not exceed 200V to meet the ±100% modulation. Therefore, the PDM duty cycle does not exceed 50%. The carrier level is equivalent to adding a DC bias to the modulation waveform. After superimposing the carrier level and the modulation waveform level and comparing with the triangular wave, the generated PDM pulse contains the amplitude information of the carrier and the information of the modulation waveform. 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 a radio frequency drive signal, which is distributed to each power amplifier module through the radio frequency drive distribution board to complete the control of the H-bridge circuit. The frequency of the drive pulse signal of the H-bridge 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] Please refer to Figure 8 , the present invention Figure 8The dead time of the H-bridge in the middle and the H-bridge drive pulse signal are generated by processing the radio frequency drive signal through a processing circuit, and the dead time is controlled within dozens of nanoseconds, meeting the requirements of the radio frequency power supply frequency range of 500 kHz to 15 MHz for plasma generation.

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

[0061] In addition, the PDM described in the present invention is a modulation method that provides an analog signal 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 period. 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 positive voltage amplitude; while a PDM signal composed entirely of "0" corresponds to a negative voltage amplitude; an alternating composition of "1" and "0" corresponds to an intermediate amplitude.

[0062] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. The descriptions in the above embodiments and the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for implementing a new type of digital modulation direct-drive power amplifier device with low distortion, characterized in that, Including: An exciter that 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 that further improves the sampling rate of the modulation waveform signal through the PDM pulse distribution unit; Among them, this method realizes the acquisition of the modulation waveform signal through Δ-Σ oversampling technology, and further improves the sampling rate of the modulation waveform signal through the interpolation filter in the PDM pulse distribution unit. The exciter can generate multi-phase PDM modulation waveform pulses and carrier drive pulses, and directly drive the power amplifier module to complete carrier generation and waveform modulation; The exciter completes the acquisition and processing of signals of different waveform formats, and generates n-channel multi-phase PDM modulation waveform drive signals, the generation of radio frequency drive signals, the reference switching of internal and external clocks, the sampling acquisition of radio frequency voltage and current, and the sampling acquisition of the power supply of the power amplifier module; The implementation method of this new type of low-distortion digital modulation direct drive power amplifier device further includes a matching transformation unit, and the matching transformation unit completes impedance change and suppression of specific frequencies through T-type impedance matching and suppression network; The implementation method of this new type of low-distortion digital modulation direct drive power amplifier device further includes a power supply unit, and the power supply unit completes rectification and filtering of external incoming power to generate the voltage required for the BUCK input of the power amplifier module unit and the auxiliary power supply required for other systems of the whole machine; 2. The implementation method of a novel low-distortion digital modulation direct-drive power amplifier device according to claim 1, characterized in that: The PDM pulse distribution unit completes the distribution of the n-channel PDM modulation waveform drive signals generated by the exciter, and the distribution is sent to the BUCK circuit of the power amplifier module unit to complete the generation of the modulation waveform modulation voltage; 3. The implementation method of a novel low-distortion digital modulation direct-drive power amplifier device according to claim 1, characterized in that: The implementation method of this new type of low-distortion digital modulation direct drive power amplifier device further includes a radio frequency drive distribution unit, and the radio frequency drive distribution unit 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.

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