Showing papers on "Pulse-frequency modulation published in 2016"

Fundamental Duty Modulation of Dual-Active-Bridge Converter for Wide-Range Operation

Abstract: This paper proposed a modulation scheme for the dual-active-bridge (DAB) converter to reduce rms current in wide-range operating conditions. The operating principle of the proposed fundamental duty modulation (FDM) is formulated based on the fundamental component analysis of the DAB converter. By modulating the PWM signals in the fundamental component domain, the optimal operation is implemented with a simple controller structure not requiring an operating mode classification, offline calculation, or current information. Operating characteristics including rms current level and ZVS characteristics are analyzed to compare loss breakdowns of the proposed scheme to those of recent related works. The proposed FDM achieves high efficiency under wide operation conditions due to reduced conduction level and wide ZVS range. Experimental results are obtained under various voltage gain and load conditions to confirm the operation of the proposed modulation scheme. A thorough experimental comparison with other sophisticated modulation schemes has verified the efficiency improvement of FDM.

Dynamic Voltage Balancing Algorithm for Modular Multilevel Converter: A Unique Solution

Abstract: The modular multilevel converter (MMC) has several submodules in cascade. To control the submodule capacitors voltage, a new generalized dynamic voltage balancing algorithm along with a simple pulse width modulator structure is proposed in this paper. With proposed pulse width modulator structure, the dynamic voltage balancing algorithm can be easily implemented with any type of carrier based pulse width modulation (including level-shifted and phase-shifted pulse width modulation) scheme without any modifications. This method does not require the sorting technique for selection of submodule capacitors voltage. The performance of the proposed voltage balancing algorithm is presented for MMC with three-level flying capacitor submodules (MMC-3L-FC). The proposed method is also applicable to the conventional two-level half bridge submodules as well. The effectiveness of the proposed voltage balancing algorithm is verified with the phase-shifted carrier-based pulse with modulation scheme. The results obtained from the MATLAB/SIMULINK simulations on 6-kV/ 2.5-MW system and the dSPACE DS1103-based laboratory prototype of 208-V/3-kVA MMC-3L-FC system are in close relationship, and thus, the proposed methodology is validated.

Research on Synchronized SVPWM Strategies Under Low Switching Frequency for Six-Phase VSI-Fed Asymmetrical Dual Stator Induction Machine

Abstract: In high-power traction drive systems, the switching frequency of the inverter is strictly limited owing to the restrictions on switching losses and cooling conditions. In this case, the multimode modulation strategy is usually adopted. Based on the analysis of a modified 24-sector space vector pulse width modulation (SVPWM) technique, several synchronous modulation strategies with different pulse numbers are proposed in this paper, which can be applied to the two-level six-phase voltage-inverter-fed asymmetrical dual-stator induction machines. By comparing the harmonic performance of the synchronized modulations, the authors present a set of multimode SVPWM strategy, which is suitable for the high-power traction drive systems under low switching frequency. At the same time, the switching strategy for transitions between different modulation modes is proposed as well. Simulation and experimental results verify the validity and effectiveness of the proposed synchronized modulation strategies and the switching strategy between different modulation modes.

Switching Frequency Analysis of Staircase-Modulated Modular Multilevel Converters and Equivalent PWM Techniques

Abstract: The large number of voltage levels in a modular multilevel converter (MMC) make staircase modulation a feasible alternative, particularly in high-power applications. However, staircase waveforms do not necessarily mean operation of the MMC submodules (SMs) at the fundamental frequency. This paper presents an analysis of SM switching frequencies in staircase-modulated MMCs and their correlation to the modulation index and load phase angle. A carrier-based pulsewidth-modulation (CB-PWM) equivalent technique is also developed. This analysis demonstrates that CB-PWM techniques provide a similar switching frequency with superior harmonic performance and improved voltage balancing characteristics at all modulation indices compared to staircase modulation. The theoretical analysis is verified with extensive simulation results for MMCs with different SMs and experimental results from a laboratory prototype.

A Charge Equalizer With a Combination of APWM and PFM Control Based on a Modified Half-Bridge Converter

Abstract: A charge equalizer with a combination of asymmetrical pulse width modulation and pulse frequency modulation control based on a modified half-bridge converter for electric vehicles is proposed in this paper. The reliability of the charge equalizer can be improved because the split capacitors are not required and the soft switching of power switches can be achieved by the proposed control. In addition, with the proposed rectification, the number of bridge rectifiers at the secondary side of the transformer can be reduced by half, which also cuts the cost and conduction loss by half. The circuit topology, operation analysis, and control strategy of the proposed charge equalizer are described in detail. Finally, the experimental results are provided to verify the feasibility and performance of the proposed charge equalizer.

An Efficient Switched-Capacitor DC-DC Buck Converter for Self-Powered Wearable Electronics

Abstract: This paper introduces an efficient reconfigurable, multiple voltage gain switched-capacitor dc-dc buck converter as part of a power management unit for wearable electronics. The proposed switched-capacitor converter has an input voltage of 0.6 V to 1.2 V generated from an energy harvesting source. The switched-capacitor converter utilizes pulse frequency modulation to generate multiple regulated output voltage levels, namely 1 V, 0.8 V, and 0.6 V based on two reconfigurable bits over a wide range of load currents from 10 $\mu\text{A}$ to 800 $\mu\text{A}$ . The switched-capacitor converter is designed and fabricated in 65-nm low-power CMOS technology and occupies an area of 0.493 mm2. The design utilizes a stack of MIM and MOS capacitances to optimize the circuit area and efficiency. The measured peak efficiency is 80% at a load current of 800 $\mu\text{A}$ and regulated load voltage of 1 V.

Selective Voltage Noise Cancellation in Three-Phase Inverter Using Random SVPWM

Abstract: This study has focused on the noise elimination at a selected frequency from the line voltage of a two-level three-phase inverter, when it is driven by random space-vector pulse-width modulation. Distribution of noise power in a wide range of frequencies in the conventional random pulse-width modulation (RPWM) methods may cause system resonant frequency excitation. Therefore, it can increase the acoustic noise and vibration in loads of inverters, especially ac motors. Thus, for the effective utilization of RPWM techniques, it is necessary to cancel noise at a specified frequency. The proposed method is able to create a gap in the spectrum of the line voltage at a selective frequency in the human hearing range. Therefore, unlike conventional RPWM techniques, switching periods are determined based on the position of the rotary reference vector. The presented relation between switching periods and the reference vector is used for the conventional space-vector pulse-width modulation (SVPWM) and two-phase SVPWM. The simulation and experimental results confirm that the proposed method effectively creates a gap at the selected frequency in power spectrum density of the line voltage of the three-phase inverter using random SVPWM.

A DCM-Only Buck Regulator With Hysteretic-Assisted Adaptive Minimum-On-Time Control for Low-Power Microcontrollers

Abstract: A 40-mA buck regulator operating in the inherently stable Discontinuous Conduction Mode (DCM) for the entire load range is presented. A pulse frequency modulation control scheme is implemented using a proposed hysteretic-assisted adaptive minimum-on-time controller to automatically adapt the regulator to a wide range of operating scenarios in terms of input, output, and passive component values while ensuring compensationless DCM operation with minimized inductor peak current. Thus, compact silicon area, low quiescent current, high efficiency, and robust performance across all possible scenarios can be achieved without any calibration. Moreover, power gating is employed in the analog circuits of the proposed controller to further improve efficiency at sub-mA loads. The regulator is integrated within a low-power microcontroller in 90-nm CMOS to power its digital core while allowing maximum flexibility in the powering options of the microcontroller and the choice of the passive components. It occupies 0.1 mm2 and achieves 92% peak efficiency, and 78.5% and 86% efficiency at 200-μA and 40-mA loads, respectively. It handles an input in the range of 1.8–4.2 V, an output in the range of 0.9–1.4 V, an inductor in the range of 4.7–10 μH, and an output capacitor in the range of 2.2–10 μF without any calibration or reoptimization.

Novel Carrier-Based PWM Strategy With Zero-Sequence Voltage Injected for Three-Level NPC Inverter

Abstract: To solve the issue of neutral-point (NP) balancing in the three-level NP-clamed inverter, a novel carrier-based pulsewidth modulation (CPWM) strategy of double modulation waveforms is proposed in this paper. By combining the injection of zero-sequence voltage with the decomposition of modulation waveform organically, NP balancing is achieved over full range of inverter output voltages and load angles for linear loads. Furthermore, the switching frequency of power devices is significantly reduced as an optimal selection method of zero-sequence voltage is applied for the proposed strategy, which is equal to that for the CPWM strategy of single modulation waveform. Effectiveness of the proposed strategy is validated by both theoretical derivation and experimental results.

Electro-optic modulator with ultra-low residual amplitude modulation for frequency modulation and laser stabilization.

Abstract: The reduction of the residual amplitude modulation (RAM) induced by electro-optic modulation is essential for many applications of frequency modulation spectroscopy requiring a lower system noise floor. Here, we demonstrate a simple passive approach employing an electro-optic modulator (EOM) cut at Brewster’s angle. The proposed EOM exhibits a RAM of a few parts per million, which is comparable with that achieved by a common EOM under critical active temperature and bias voltage controls. The frequency instability of a 10 cm cavity-stabilized laser induced by the RAM effect of the proposed EOM is below 3×10−17 for integration times from 1 to 1000 s, and below 4×10−16 for comprehensive noise contributions for integration times from 1 to 100 s.

Analysis of different modulation techniques for multilevel inverters

Abstract: Analysis of different modulation techniques for multilevel inverter is discussed. To control the multilevel inverters, different modulation techniques have been used. Amongst them multi carrier Sine Pulse Width Modulation (SPWM) techniques are widely used for different multilevel inverter topologies. These modulation techniques are derived from the conventional two level inverter SPWM technique. Different modulation techniques are compared on the basis of the output THD, utilization of DC link voltages and common mode voltage. The detailed analysis of modulation techniques are shown on the basis of the output THD offered by the five level Neutral Point Clamped or Diode Clamped (NPC) inverter.

Steady-state analysis of the phase shift modulated LLC resonant converter

Abstract: In many applications, phase shift modulation (PSM) has been proven to be a promising supplement of pulse frequency modulation (PFM) in LLC resonant converter. However, steady-state analysis of PSM LLC converter is not thoroughly studied yet. This paper presents a generalized PSM LLC model which can provide accurate prediction on resonant voltage and current behavior, dc gain and all the other steady-state information. Then, operation modes, mode boundaries and distribution are discussed with three cases according to the relationship between switching frequency and resonant frequency. Meanwhile, dc voltage gain and zero-voltage switching characteristics of each operation mode are briefly analyzed. Simulation results verify the accuracy of proposed analysis.

Enhanced modulation rates via field modulation in spin torque nano-oscillators

Abstract: Spin Transfer Nano-Oscillators (STNOs) are promising candidates for telecommunications applications due to their frequency tuning capabilities via either a dc current or an applied field. This frequency tuning is of interest for Frequency Shift Keying concepts to be used in wireless communication schemes or in read head applications. For these technological applications, one important parameter is the characterization of the maximum achievable rate at which an STNO can respond to a modulating signal, such as current or field. Previous studies of in-plane magnetized STNOs on frequency modulation via an rf current revealed that the maximum achievable rate is limited by the amplitude relaxation rate Γp, which gives the time scale over which amplitude fluctuations are damped out. This might be a limitation for applications. Here, we demonstrate via numerical simulation that application of an additional rf field is an alternative way for modulation of the in-plane magnetized STNO configuration, which has the advantage that frequency modulation is not limited by the amplitude relaxation rate, so that higher modulation rates above GHz are achievable. This occurs when the modulating rf field is oriented along the easy axis (longitudinal rf field). Tilting the direction of the modulating rf field in-plane and perpendicularly with respect to the easy axis (transverse rf field), the modulation is again limited by the amplitude relaxation rate similar to the response observed in current modulation.

Sampling Effect Characterization of Digital SPWM of VSI in Time Domain

Abstract: This paper characterizes the sampling effect in digital sinusoidal pulse width modulation (SPWM) of voltage source inverter (VSI). The time-domain analysis presented in this paper establishes the relation between the fundamental frequency, carrier frequency, and the sampling frequency at different modulation indices of the SPWM. The analysis investigates the effect of sampling frequency of the digital controller on the output of the VSI. It is shown that the low-frequency harmonic components appear in the frequency spectrum of the VSI output voltage due to sampling. As a result, the output current of digitally controlled VSI is stepped in nature. The double Fourier integral solution of the switched waveform for inner and outer integral limits has been used to derive the expression. The integral solution is obtained using Jacobi-Anger expansions. The generalized results developed in this paper are useful to investigate the sampling effect in high switching frequency DSPWM. The proposed sampling effect has been analyzed for SPWM of single-phase H-bridge inverter. The analytical results are verified using simulation and experimental results. The experimental results have been obtained with the use of field-programmable gate array (FPGA) as a digital controller.

Distributed pulse width modulation control

Abstract: A distributed pulse-width modulation system includes an array of pulse-width modulation elements, each element including a digital memory for storing a multi-bit digital value and a drive circuit that drives an output device in response to the multi-bit digital value stored in the digital memory. A system controller includes a memory for storing a multi-bit digital value for each element and a communication circuit for communicating each multi-bit digital value to each corresponding pulse-width modulation element.

Configurable Multimode Digital Control for Light Load DC–DC Converters With Improved Spectrum and Smooth Transition

Abstract: Efficiency in a light load dc–dc converter is improved by reducing the switching frequency with the load current. Further, a bifrequency operation (BFO) using pulse train (PT) control can achieve spread spectrum. Using discrete-time models, this paper shows that a stable periodic BFO is generally not achievable in existing PT control methods. Thereafter, a unified multimode digital control technique is proposed, in which a voltage-mode digital pulse-width-modulator (DPWM) is used to control a predefined periodic BFO. Beside the fixed-frequency DPWM, an extra multiplexer is considered for real-time configuration to: 1) bifrequency pulse frequency modulation; 2) PT control; or 3) pulse regulation control; or 4) pulse skipping control with smooth transition. Analysis and design methods are discussed to ensure periodic BFO and to customize the power spectrum with predictable ripple parameters. A buck converter prototype is made, and the proposed control is implemented using an FPGA device.

Frequency Chirp Supported Complex Modulation of Directly Modulated Lasers

Abstract: The frequency chirp of the directly modulated lasers (DML) has long been regarded as the performance barrier preventing the DML from being employed in high-speed optical transmissions. In contrast, we regard the chirp as the combination of intensity modulation (IM) and frequency modulation in this paper. By utilizing coherent detection which provides a wavelength reference by the local oscillator, FM can be converted to phase modulation via time integral. Namely, we realize a 2 dimensional complex modulation (CM) using a single DML. The channel of a complex modulation of directly modulated lasers (CM-DML) is convolutional due to the integral operation. The maximum likelihood sequence estimation can be applied for demodulation. CM-DML offers more than 10-dB system OSNR sensitivity advantages over the conventional IM-DML using coherent detection, which shrinks the sensitivity penalty to 1000-km transmission of the standard single mode fiber. This reach record of the optical PAM reveals the great potentials of the CM-DML to replace the commercialized DP-QPSK products for medium reach applications.

Secondary-side control method and secondary-side control circuit of switching power supply

Abstract: The invention provides a switching power supply, especially a secondary-side control method and a secondary-side control circuit of an isolated switching power supply According to the method and the circuit, an error amplifier is installed at a secondary side, the output voltage of the power supply is sampled and an error signal is generated, and the error signal is modulated into an opening signal of different frequencies to realize PFM (Pulse Frequency Modulation) The opening signal is transmitted to a primary side to open a main power tube, different current limiting voltage is generated at the primary side according to the frequency of the opening signal, and the main power tube is closed at the current limiting voltage to realize PWM Through the method and the circuit of the invention, the precision of output voltage and the load regulation rate are improved, good dynamic performance is achieved, synchronous rectification is easy to realize, and the no-load power consumption is reduced

FQAM/FPSK modulation for spatial modulation systems

Abstract: Spatial Modulation (SM) is a recently developed transmit technique, and it has attracted wide interests for it gains higher transmit rate than single-input-single-output (SISO) system and provides simpler transceiver structure and lower power consumption compared with traditional MIMO system. In this paper, we propose the spatial modulation systems with frequency and quadrature amplitude modulation (FQAM)/frequency and phase shift keying (FPSK), which combine frequency shift keying (FSK) and quadrature amplitude modulation (QAM)/phase shift keying (PSK). Simulation results show that the proposed scheme (i.e. FQAM/FPSK-SM) achieves significantly better bit error performance (BER) than traditional SM system and FQAM/FPSK system using maximum likelihood (ML) detector, and it can assign information flexibly among the constellation modulation, the index of the active antenna and the index of the active frequency. We also compare and analyze system performance and complexity of optimal detector and sub-optimal detector.

High-Speed Frequency Modulated Low-Noise Single-Frequency Fiber Laser

Abstract: A novel high-speed frequency modulating scheme based on the self-injection locked single-frequency fiber laser is demonstrated. The laser frequency noise reaches −5 dB re Hz/Hz $^{1/2}$ at $\sim 25$ kHz, while the linewidth is estimated to be $\sim 800$ Hz. By modulating the length of external cavity to which the laser is locked, a stable frequency modulated laser with a modulation speed up to 160 kHz, and modulation amplitude >145 MHz at a modulation speed of 60 kHz are realized. The intensity noise spectrum of the frequency modulated fiber laser is found to be the same with that of the laser before modulation, except a series of gradually weakened harmonic peaks at the modulating frequency.

Dual-mode non-return-to-zero (NRZ)/ four-level pulse amplitude modulation (PAM4) receiver with digitally enhanced NRZ sensitivity

Abstract: A four-level pulse amplitude modulation receiver has a four-level pulse amplitude modulation mode and a non-return-to-zero modulation mode. First, second, and third four-level pulse amplitude modulation samplers are coupled to an input. Each of the samplers has a corresponding output in turn including a corresponding binary decision of the first, second, and third samplers. A four-level pulse amplitude modulation decoder circuit has inputs coupled to the outputs of the samplers. The four-level pulse amplitude modulation decoder circuit is active in the four-level pulse amplitude modulation mode. The receiver also includes a non-return-to-zero majority voting circuit coupled to the outputs of the samplers. The non-return-to-zero majority voting circuit has an output and is configured to output a majority decision of the corresponding binary decisions of the samplers, and is active in the non-return-to-zero modulation mode.

Frequency response control of semiconductor laser by using hybrid modulation scheme.

Abstract: A hybrid modulation scheme that simultaneously applies the direct current modulation and intra-cavity loss modulation to a semiconductor laser is proposed Both numerical calculations using rate equations and experiments using a fabricated laser show that the hybrid modulation scheme can control the frequency response of the laser by changing a modulation ratio and time delay between the two modulations The modulation ratio and time delay provide the degree of signal mixing of the two modulations and an optimum condition is found when a non-flat frequency response for the intra-cavity loss modulation is compensated by that for the direct current modulation We experimentally confirm a 864-dB improvement of the modulation sensitivity at 20 GHz compared with the pure direct current modulation with a 07-dB relaxation oscillation peak

Relationship between two different space-vector modulation methods of eight-switch three-phase inverters

Abstract: In this paper, two different space-vector modulation (SVM) methods based on different basic voltage vectors of eight-switch three-phase inverters (ESTPIs), which are the post-fault reconfigured topologies for the three-level neutral-point-clamped (3L-NPC) inverter with the open-circuit fault in a leg, are analyzed. Based on the pulse-width modulation regular sampling method, the equivalent carrier-based pulse-width modulation (CBPWM) methods of these two different SVM methods are derived, respectively. By comparing these two CBPWM methods, the relationship between the two different SVM methods of ESTPIs is revealed. On the basis of that, the comprehensive relationship between CBPWM methods and SWM methods of ESTPIs is also revealed. Experimental results have shown the validity of the theoretical analysis.

A new algorithm for a high-modulation frequency and high-speed digital lock-in amplifier

Abstract: To increase the maximum modulation frequency of the digital lock-in amplifier in an online system, we propose a new algorithm using a square wave reference whose frequency is an odd sub-multiple of the modulation frequency, which is based on odd harmonic components in the square wave reference. The sampling frequency is four times the modulation frequency to insure the orthogonality of reference sequences. Only additions and subtractions are used to implement phase-sensitive detection, which speeds up the computation in lock-in. Furthermore, the maximum modulation frequency of a lock-in is enhanced considerably. The feasibility of this new algorithm is tested by simulation and experiments.

A 254 GHz CMOS Transmitter With VCO-Q Modulation

Abstract: This letter presents a transmitter at 254 GHz, which uses both amplitude and frequency changes of a transformer-based VCO output by control voltage Amplitude modulation is achieved by VCO-Q modulation of the VCO with varactor control voltage $(V_{\text{CONT}})$ Wide-deviation frequency modulation is also achieved due to its wide tuning range, which improves the amplitude modulation by filtering out a low-amplitude band at a receiver It is fabricated by a 65 nm CMOS process and demonstrates a high data rate of over 10 Gb/s and a low dc power consumption of 23 mW The amplitude modulation is improved by 97 dB with an implemented receiver

Design and Analysis of a High Bandwidth Rectifying Regulator With PWM and PFM Modes

Abstract: We propose a novel rectifying regulator to wirelessly power a neural stimulator in 65 nm CMOS process. The regulating rectifier operates at 13.56 MHz and has two operating modes. In the high power pulse width modulation (PWM) mode, it regulates the output voltage by controlling the conduction time during every cycle of the incoming HF signal. The PWM mode is designed with a high bandwidth feedback loop to satisfy the transient time requirements of the stimulator. The rectifier also incorporates a pulse frequency modulation (PFM) mode to power the stimulator in sleep mode wherein it controls the frequency at which the rectifier conducts to efficiently deliver low output power. We present the theory and develop an analytical model for the rectifying regulator and validate the model for both PWM and PFM operating modes.

Comparative evaluation of pulse width modulation techniques on effective DC link voltage utilization of grid connected inverter

Abstract: In this paper, comparison between two different Pulse Width Modulation (PWM) techniques employed for three phase voltage source inverter (VSI) is discussed. The three phase voltage source inverter is basic topology used to supply a grid. In this paper we have design a LC filter between the inverter and the grid in order to stabilize the output voltage. The filter gives sinusoidal three phase voltage at the output of the inverter with almost zero/less harmonic distortion. A suitable PWM technique is employed to obtain the required output voltage in the line side of the inverter. The PWM generation techniques used mainly based on sinusoidal based Pulse Width Modulation (SPWM) and Space Vector based Pulse Width Modulation (SVPWM). In SPWM method involves the comparison of the three phase reference modulating signals with a common triangular carrier wave to generate the pulses for the three phases. Whereas, in SVPWM method, a revolving reference voltage vector is provided as voltage reference instead of three phase modulating waves. This paper analyses these two Pulse Width Modulation techniques for grid connected inverter and to study the performance of the same by comprehensively analyzing the simulation results.

Noise performance and nonlinear distortion of semiconductor laser under two-tone modulation for use in analog CATV systems

Abstract: We introduce numerical modeling of noise performance and distortion of semiconductor lasers subject to two-tone modulation according to the National Television Standards Committee NTSC plan for the cable television (CATV) signal transport. The waveform of the laser signal is simulated over wide ranges of the modulation index and placements of the modulation channel. The power and frequency spectra of the relative intensity noise (RIN) are characterized, and the associated second-order harmonic distortion (2HD), and the second-order (IMD2) and third-order intermodulation distortions (IMD3) are calculated. The calculated data are used to predict the measures of the CATV system performance. The dynamic range of linearity of the laser is evaluated in terms of the spuriousfree dynamic range SFDR. We show that under weak modulation, the low-frequency RIN is constant at � 168dB/Hz regardless the modulation frequency. Within this accepted noise level, IMD2 is 4dBm higher than 2HD and 10dBm higher than IMD3. When the modulation index exceeds 25%, the laser emits clipped signals associated with large values of signal distortions. Accepted values of the carrier to noise ratio and distortions correspond to lower modulation index and/or channel frequency. Copyright © 2015 John Wiley & Sons, Ltd. Received 26 January 2015; Revised 15 March 2015; Accepted 17 April 2015