Switching Power Amplifier Research Articles

Study on High Performance Power Amplifier for Maglev Flywheel

Power amplifier for maglev flywheel control system should have the characteristics of low ripple and fast response. In this paper, a maglev flywheel and a method of two-level power amplifier based on DSP and FPGA are proposed. An equivalent model of switching power amplifier based on Fourier series is established and simulation analysis is carried on as well. Experimental platform for switching amplifier is built and experiment results show that the coil current signal can track command signal fast and stably, which proves the validity of the proposed design method. Simulation results are close to the experimental result, which means that the model can guide the power amplifier design.

Research of Drives of Power Amplifiers of Magnetic Levitation Servo Spindle Applied to Micro EDM Based on FPGA

The drives of power amplifiers of magnetic levitation servo spindle applied to micro EDM (Electron discharge machining) based on FPGA (Field programmable gate array) are developed. The drive module that produces the PWM (Pulse width modulation) waves that conform to the requirements of spindle power amplifiers involving three-level half bridge switch power amplifier, three-level full bridge switch power amplifier and motor power amplifier, according to input of action values from magnetic levitation servo spindle controller DSP (Digital signal processor) is designed. Multi-PWM producing algorithm by single timer with multi comparing nodes is proposed. After being applied to control system of magnetic levitation servo spindle, the drives accomplish conversion from DSP action values to PWM waves. The PWMs that drive radial coil current power amplifier have phase difference of 180°. The PWMs that drive axial coil current power amplifier have dead zone time and their wave shapes are complementary. The PWMs that drive the motor power amplifier conform to requirements of power amplifier chip LMD18200. Using FPGA to realize the drive function of spindle power amplifier makes the drive design more flexible, resource distribution of DSP more optimized, the task of algorithms running more centralized, and the drives module gets simpler and more reliable because the phase shift circuit and dead zone circuit are cancelled but the function of phase shift and dead zone is reserved.

Self-Tuning High-Voltage High-Frequency Switching Power Amplifier for Atmospheric-Based Plasma Sterilization

In this paper, the implementation of a power supply for the generation of plasma, with the purpose of sterilizing a surface, is presented. A power supply based on a Class-E switching amplifier is proposed. This switch-mode amplifier is capable of producing a high-voltage and high-frequency output for plasma generation. In addition, a feedback mechanism is used to handle load variation. This is achieved through the characterization of the load at high voltages while generating plasma. Portability of the system is the primary goal of this paper. Thus, the implementation of a miniaturized circuit capable of achieving high efficiency and low power consumption at the same time is critical. The design and implementation of the complete battery-powered system, as well as the simulation and measurement results are discussed.

Single-Bit Pseudoparallel Processing Low-Oversampling Delta–Sigma Modulator Suitable for SDR Wireless Transmitters

The oversampling requirement in a delta-sigma modulator (DSM) is considered one of the limiting factors toward its employment in current high-frequency applications, such as wireless software defined radio (SDR) systems. This paper advances that the critical requirement for DSMs is high-frequency processing and not a high-oversampling ratio. A single-bit semiparallel processing structure to accomplish the high-frequency processing is proposed in this paper. Using the suggested low-oversampling digital DSM architecture, high-speed, high-complexity computations, which are normally required for wireless applications, are executed simultaneously. This facilitates the design of embedded SDR multistandard transmitters using commercially available digital processors. The most favorable application of the proposed single-bit DSM is to build an radio frequency transmitter that includes a one-bit quantifier with two-level switching power amplifier for both high linearity and high efficiency. Performance analysis is carried out by using MATLAB simulations, which shows a reduction of the oversampling ratio by a factor of 16 (for a baseline oversampling ratio of 256) with the same signal-to-noise ratio (SNR). The proposed DSM is also implemented on a field-programmable gate array (FPGA) board and its performance is validated by using a code division multiple access signal. The bandwidth of the output signal is increased four times without increasing the processing frequency. Simultaneously, quality of the output signal remains the same but FPGA resource usage is increased by a factor of three.

Efficient Switching Power Amplifiers Using the Distributed Switch Architecture

Wireless transmitters employing switching power amplifiers are popular both in RF and mm-wave designs. The efficiency of switching power amplifiers is dictated mainly by the maximum achievable switch size which in turn is governed by the switch transition frequency (tradeoff between switch on-resistance and capacitance). This paper presents a new architecture, the distributed switching power amplifier (DSPA), that helps break this tradeoff by distributing the switch in the nonlinear amplifier design, especially at high frequencies. A comprehensive analytical framework has been developed and the theory has been compared with simulation results.

A Self-Sensing Active Magnetic Bearing Based on a Direct Current Measurement Approach

Active magnetic bearings (AMBs) have become a key technology in various industrial applications. Self-sensing AMBs provide an integrated sensorless solution for position estimation, consolidating the sensing and actuating functions into a single electromagnetic transducer. The approach aims to reduce possible hardware failure points, production costs, and system complexity. Despite these advantages, self-sensing methods must address various technical challenges to maximize the performance thereof. This paper presents the direct current measurement (DCM) approach for self-sensing AMBs, denoting the direct measurement of the current ripple component. In AMB systems, switching power amplifiers (PAs) modulate the rotor position information onto the current waveform. Demodulation self-sensing techniques then use bandpass and lowpass filters to estimate the rotor position from the voltage and current signals. However, the additional phase-shift introduced by these filters results in lower stability margins. The DCM approach utilizes a novel PA switching method that directly measures the current ripple to obtain duty-cycle invariant position estimates. Demodulation filters are largely excluded to minimize additional phase-shift in the position estimates. Basic functionality and performance of the proposed self-sensing approach are demonstrated via a transient simulation model as well as a high current (10 A) experimental system. A digital implementation of amplitude modulation self-sensing serves as a comparative estimator.

The Research on Switch-Linear Hybrid of Precise Current Source

In this paper, a novel current control strategy of precise current source is presented, which combines switch power conversion mode with linear amplification mode. The linear power amplifier is used as the power converter in the current loop. The current controller is a double cascaded PI (DCPI) controller which is put up by the way of analog circuit, it can suppress the high frequency disturbance signal effectively. The switch-filter circuit can generate a special power supply for linear power amplifier, the voltage of this special power supply changes as the load voltage does. The topology of four-level H-Bridge works as the power converter of the switch power amplifier, the LC filter circuit can eliminate the current ripple caused by the PWM chopper.The simulation and experimental results verify that the Switch-Linear Hybrid (SLH) scheme is of high efficiency and output quality. The bandwidth of the precise current source is 5.4 kHz and the phase margin is 42 degree.

Self-sensing active magnetic bearing using real-time duty cycle

In a self-sensing active magnetic bearing (AMB) system driven by pulse width modulation (PWM) switching power amplifiers, the rotor position information can be extracted from coil current and voltage signals by a specific signal demodulation process. In this study, to reduce the complexity of hardware, the coil voltage signal was not filtered but measured in the form of a duty cycle by the eCAP port of DSP (TMS320F28335). A mathematical model was established to provide the relationship between rotor position, current ripple, and duty cycle. Theoretical analysis of the amplitude-frequency characteristic of the coil current at the switching frequency was presented using Fourier series, Jacobi-Anger identity, and Bessel function. Experimental results showed that the time-varying duty cycle causes infinite side frequencies around the switching frequency. The side frequency interval depends on the varying frequency of the duty cycle. Rotor position can be calculated by measuring the duty cycle and demodulating the coil current ripple. With this self-sensing strategy, the rotor system supported by AMBs can steadily rotate at a speed of 3000 r/min.

A High-Performance Digital Servo Driver for Magnetic Levitation Planar Motor

A new digital DC servo driver based on DSP and FPGA for planar motor was designed in this paper. Current feedback and digital self-tuning PID algorithm control strategy are applied. Switching power amplifier or class D amplifier is the choice of power amplifier. The most prominent characteristic of the servo driver used in planar motor is high efficiency, low temperature drift, small size, fast response, and high-bandwidth. Finally, the performance parameters and power loss parameters of the servo driver are given.

A Study on Multi-Level PWM and Asynchronous /spl Sigma/ /spl Delta/ Modulations for Enhanced Bandlimited Signal Tracking in Switching Power Amplifiers

This work deals with multi-level switching amplifiers, in the context of high-efficiency power amplification for signal tracking applications. In particular, this paper evaluates the reduction in the error signal's power due to multi-level power amplification (compared to conventional two-level amplifiers) and compares the performance of two multi-level pulse modulations: PWM and Asynchronous ΣΔ Modulation. First the intrinsic bandwidth limits of multi-level switching amplifiers are inferred, to clearly state the advantages and limitations of multi-level power amplification. From the existing analyses of Pulse Width Modulation already reported in the literature, PWM is herein extended to multiple levels based on an equivalent representation, which allows to derive a closed expression for the power spectrum of multi-level PWM in bandlimited signal tracking. The Asynchronous ΣΔ Modulation is extended to multiple levels and the resulting multi-level encoding algorithm is analyzed in both time and frequency domains. The performance of both modulations is characterized and compared at different operating frequencies and using different number of levels. The main outcomes of this in-depth characterization show that, if the switching frequency is high enough, the tracking error is independent of the modulation and the switching frequency, i.e., it only depends upon the number of levels, which points out the suitability of asynchronous modulations for relatively low switching frequencies (compared to the number of levels).

Designing Harmonic-Controlled Drivers for Switching Power Amplifiers

A driver for a switching power amplifier is designed by an iterative least squares method. With only one stub and two lines in each input and output matching network, amplitude and phase responses up to ninth-order harmonic frequencies have been controlled. The designed amplifier is built, and the method is verified with measurements.

Analysis and Design of a New Topology of Soft-Switching Inverters

This paper proposes the power conversion mechanism of a bailer-charge-transfer zero-current-switching (CT-ZCS) circuit. The operation modes are analyzed and researched using state trajectory equations. The topology of CT-ZCS based on soft-switching inverters offers some merits such as: tracking the input reference signal dynamically, bearing load shock and short circuit, multiplying inverter N+1 redundancy parallel, coordinating power balance for easy control, and soft-switching commutation for high efficiency and large capacity. These advantages are distinctive from conventional inverter topologies and are especially demanded in AC drives: new energy generation and grid, distributed generation systems, switching power amplifier, active power filter, and reactive power compensation and so on. Prototype is manufactured and experiment results show the feasibility and dynamic voltage-tracking characteristics of the topology.

SWITCHING POWER AMPLIFIER AND METHOD OF CONTROLLING THE SAME

A switching power amplifier having a pulse width modulation (PWM) signal generation unit that converts an input audio signal into a PWM signal with a predetermined carrier frequency, a correction unit that corrects the difference between an audio signal included in the PWM signal and a negative feedback output audio signal to generate a corrected PWM signal, a low pass filter that removes a high-frequency component from the corrected PWM signal, a frequency modulation unit that modulates the corrected PWM signal so that the corrected PWM signal has a switching frequency different from the carrier frequency of the input PWM signal to generate a modulated PWM signal, and a power amplification unit that amplifies a power of the modulated PWM signal.

Current-Sensing Resistor Design to Include Current Derivative in PWM H-Bridge Unipolar Switching Power Amplifiers for Magnetic Bearings

To effectively reject the influence of digital control delay on system bandwidth and stability in pulsewidth-modulation H-bridge unipolar switching power amplifiers for magnetic bearings and to overcome the disadvantages of the traditional linear predictive control, this paper presents a current-sensing resistor design to include current derivation. The proposed solution can realize predictive current control by the proportional-differential current-sensing resistor networks. The common problems associated with the digital control delay are successfully resolved by the proposed method. Moreover, compared to the traditional linear prediction, the proposed one not only shortens the calculation time of the digital signal processor but also increases the tracking precision and significantly reduces the current noise. Analysis, simulation, and experimental results are presented to demonstrate the effectiveness and superiority of the proposed method.

Comparison of ordinary and time-varying Volterra analysis for finding distortion contributions

Volterra analysis can be used to perform distortion contribution analysis. It is shown here that an ordinary time-invariant (TI) Volterra analysis with fitted polynomial models can be used in such a non-linear application as mixers and switching power amplifiers, where time-varying (TV) Volterra analysis has often been used. TI and TV Volterra analyses are compared behaviorally, and the use of TI Volterra with fitted polynomial coefficients is illustrated by analyzing two highly non-linear example circuits using a recently developed Volterra-on-Harmonic-Balance (VoHB) analysis tool.

Impact of Switching Glitches in Class-G Power Amplifiers

Envelope elimination and restoration (EER) based transmitters have attracted attention recently for two reasons: 1) The desire for increased spectral efficiency has mandated modulation standards that have large peak-to-average ratios (PAR). The increase in spectral efficiency is traded off against a decrease in average power-added-efficiency (PAE) when a linear power amplifier is used; however, when EER is used, it is decoupled somewhat from spectral efficiency. 2) Through the use of fast on-chip signal processing, the natural advantage of scaled CMOS is exploited by enabling switching power amplifier classes (e.g., class-E). This letter examines limitations associated with voltage supply switching glitches in class-G power amplifiers.

Self-Adaptive Phase-Lead Compensation Based on Unsymmetrical Current Sampling Resistance Network for Magnetic Bearing Switching Power Amplifiers

To adaptively reduce the influence of phase lag of traditional current mode switching power amplifiers on system stability and static and dynamic performances for magnetic bearing systems, this paper proposes a new, simple, and effective phase-lead compensation strategy based on unsymmetrical current sampling resistance network. The common problems associated with the existing phase-lead compensation methods for magnetic bearing power amplifiers are successfully handled via this method without additional hardware or software resources. The effectiveness and superiority of this proposed strategy have been demonstrated by both simulation and experimental results.

The Design and Research of Switching Power Amplifier Used on Magnetic Suspension Support

This paper focuses on the switching power amplifier of magnetic suspension support. The principle of magnetic suspension support was described. Due to the particularity that the load of magnetic suspension support is inductive, the response speed, efficiency and stability should be considered when the switching power amplifier is designed. In the power amplifier, PI circuit can make feedback current follow the given signal in time. In this paper, the amplifier adopts pulse width modulation (PWM) control strategy. The design of PI circuit, PWM circuit as well as the driving circuit were presented in the paper. After completing the designs of all parts, we choose MULTISIM as simulation software, which can establish an accurate circuit model. The simulation results show that the switching power amplifier designed in this paper has bigger bandwidth and less distortion and it can respond timely.

Comparison and Improvement for PWM Output Circuit

The switch power amplifier is widely used in magnetic bearing system, the lab uses pulse width modulator TL494 which is produced by U.S. Texas instruments company to drive power tubes. It can generate PWM signal. In this paper, a three level half bridge switch power amplifier is designed based on TL494.The original design of the double op-amp circuit is analyzed and improved through analyzing positive input signal for the internal error amp of TL494. Removing the redundant circuit, the new signal input circuit can realize the same function as the double op-amp circuit and the circuit structure can be more compact.

Tunable continuous-time ΔΣ modulator for switching power amplifier

Tunable continuous-time ΔΣ modulator for switching power amplifier