Pulse Density Modulation Research Articles

Selected-Interharmonic-Injected Pulse Density Modulation for One-to-Many WPT Systems

Selected-Interharmonic-Injected Pulse Density Modulation for One-to-Many WPT Systems

Performance Improvement of Wireless Power Transfer System for Sustainable EV Charging Using Dead-Time Integrated Pulse Density Modulation Approach

The recent developments in electric vehicle (EV) necessities the requirement of a human intervention free charging system for safe and reliable operation. Wireless power transfer (WPT) technology shows promising options to automate the charging process with user convenience. However, the operation of the WPT system is designed to operate at a high-frequency (HF) range, which requires proper control and modulation technique to improve the performance of power electronic modules. This paper proposes a dead-time (DT) integrated Pulse Density Modulation (PDM) technique to provide better control with minimal voltage and current ripples at the switches. The proposed technique is investigated using a LCC-LCL compensated WPT system, which predominantly affects the high-frequency voltage and current ripples. The performance analysis is studied at different density conditions to explore the impact of the integrated PDM approach. Moreover, the PDM technique gives better control over the power transfer at different levels of load requirement. The simulation and experimental analysis was performed for a 3.7 kW WPT prototype test system under different modes of operation of the high-frequency power converters. Both the simulated and experimental results demonstrate that the proposed PDM technique effectively enhances the efficiency of the HF inverter while significantly reducing output current ripples, power dissipation and improving the overall WPT system efficiency to 92%, and leading to a reduction in the power loss in the range of 10% to 20%. This leads to improved overall system control and performance.

ClosedLoop Control of Pulse-Density-Modulated Wireless Power Transfer with Fast MEPT

Efficient wireless power transfer (WPT) requires closedloop control to perform maximum efficiency point tracking (MEPT) against the dynamic changes of operating conditions. In this paper, we took the latest deltasigma pulse-density-modulated (PDM) WPT system as the plant and presented a systematic control design procedure. The WPT system was modeled by the reducedorder dynamic phasor method and further decoupled under the tuned condition. It was identified that the coupled resonators behave like a secondorder system, and its natural frequency is much lower than the resonant frequency. This was considered in the closedloop design to derive a suitable loop gain and ensure stability. The nonlinearity caused by the dualside PDM control is limited to a small inner loop so that the entire loop is linear and simple. Experimental results showed that the closedloop voltage regulation and MEPT took only about 10 ms after load stepping. The system DC output voltage was always tightly regulated, and the steadystate efficiency was very close to the theoretical maximum value under different coupling conditions.

Acoustic stimulation of the human round window by laser-induced nonlinear optoacoustics.

The feasibility of low frequency pure tone generation in the inner ear by laser-induced nonlinear optoacoustic effect at the round window was demonstrated in three human cadaveric temporal bones (TB) using an integral pulse density modulation (IPDM). Nanosecond laser pulses with a wavelength in the near-infrared (NIR) region were delivered to the round window niche by an optical fiber with two spherical lenses glued to the end and a viscous gel at the site of the laser focus. Using IPDM, acoustic tones with frequencies between 20Hz and 1kHz were generated in the inner ear. The sound pressures in scala tympani and vestibuli were recorded and the intracochlear pressure difference (ICPD) was used to calculate the equivalent sound pressure level (eq. dB SPL) as an equivalent for perceived loudness. The results demonstrate that the optoacoustic effect produced sound pressure levels ranging from 140eq. dB SPL at low frequencies ≤ 200Hz to 90eq. dB SPL at 1kHz. Therefore, the produced sound pressure level is potentially sufficient for patients requiring acoustic low frequency stimulation. Hence, the presented method offers a potentially viable solution in the future to provide the acoustic stimulus component in combined electro-acoustic stimulation with a cochlear implant.

Continuous Pulse Density Modulation of Series Resonant Converter for Wide-Range High-Resolution Output Voltage and High Efficiency

Continuous Pulse Density Modulation of Series Resonant Converter for Wide-Range High-Resolution Output Voltage and High Efficiency

Fuzzy Logic Controlled Pulse Density Modulation Technique for Bidirectional Inductive Power Transfer Systems

Fuzzy Logic Controlled Pulse Density Modulation Technique for Bidirectional Inductive Power Transfer Systems

Conditional Pulse Density Modulation for Inductive Power Transfer Systems

Conditional Pulse Density Modulation for Inductive Power Transfer Systems

Battery-less luminance sensor biomimicking human sensory nervous system

With the evolution of materials science and microfabrication processes, energy harvesters have become sophisticated, achieving power outputs in the range of several milliwatts, and have become a promising alternative to conventional batteries. Although their output power is insufficient to continuously operate a wireless sensor module, energy harvesters can operate small integrated circuits, including timers, watches, and ring oscillators. In this study, we emulated the human sensory nervous system to develop a battery-less sensor with a built-in analog-to-digital converter. The human sensory nervous system comprises a sophisticated sensing mechanism that digitalizes external stimuli by pulse-density modulation. To mimic this behavior, we integrated a ring oscillator with photovoltaics, allowing it to function as a luminance sensor with an event-driven operation. The oscillation frequency of the ring oscillator changes with respect to the operating voltage; hence, the output voltage of the photovoltaic modulates the frequency by more than two orders of magnitude. The sensor exhibits oscillation frequencies of 10 kHz and 7.7 MHz corresponding to luminance levels of 25–25 000 lx. Its response times are 40 μs and 15 ms when the light source is turned on and off, respectively. Battery-less sensors expand the opportunities for the application of energy harvesters in biomedical, wearable, and environmental sensing.

Implementation of the irregular pulse density modulation‐controlled wireless power transfer system for constant current and constant voltage output

SummaryIn this paper, irregular 32 pulse density modulation (PDM)‐controlled wireless power transfer (WPT) system is proposed for constant current (CC) and constant voltage (CV) outputs. The proposed WPT system has a load independent ZPA frequency characteristic with CC and CV outputs. Thus, soft switching conditions are achieved for both CC and CV outputs. An experimental prototype was prepared to validate the effectiveness of the proposed irregular 32 PDM‐controlled WPT system. WPT coil design parameters are presented and analyzed with lateral and rotational misalignment conditions in ANSYS. The experiments were determined as 3 A for CC output and 200 V for CV output. The maximum efficiency of the proposed system is measured (95.34%) at aligned coils with 100 mm air gap. In addition, the efficiency results are presented and evaluated by performing experimental studies under both lateral and rotational misalignment conditions.

Sigma-Delta Modulation on a Three-Phase Four-Leg VSI to Eliminate the Common Mode Voltage and Comply With the Military Standards

This paper demonstrates sigma-delta pulse density modulation (PDM) without common mode voltage on a four-leg voltage source inverter designed as a grid-forming inverter. Using PDM ensures that switching updates occur simultaneously for all phases and sigma-delta modulation is the most advantageous PDM for this application. The converter does not produce common mode voltage in the switching frequency range, thus meeting the conducted electromagnetic interference limits in MIL-STD-461G without the need for a large common mode choke. Further, the proposed common mode elimination method does not degrade the output voltage power quality, which meets the requirements in MIL-STD-1399 section 300 part I for type 1 voltage. The practical implementation of the control system on a Field Programmable Gate Array (FPGA) is presented and compliance with the two military standards is demonstrated on a laboratory prototype built with SiC MOSFETs.

Reduction of Spurious Switching in Direct Vector Quantized Space Vector Pulse Density Modulation Scheme for Multilevel Inverters

A generalized online switching scheme for multi-level inverter based on Direct Vector Quantized Space Vector Pulse Density Modulation (DVQSVPDM) suitable for adjustable speed drive is proposed in this article. The existing DVQSVPDM schemes have spurious switching as the voronoi region is determined from integrated error vector of Sigma Delta Modulator (SDM). This results in high Total Harmonic Distortion (THD) of Common Mode Voltage (CMV) at lower modulation index. In the proposed DVQSVPDM the nearest three space vectors to the reference vector forms the triangular voronoi region. The integrated error vector of SDM is quantized to its nearest space vector in the voronoi region to generate the switching vectors. This reduces spurious switching associated with DVQSVPDM schemes and improves the performance at lower modulation index by reducing THD of CMV. The proposed scheme works for all n-level inverter topologies and the computations required remain same irrespective of level of inverter. Redundant states of switching vectors are not considered for switching which results in the discontinuous nature of proposed scheme. The performance of proposed DVQSVPDM is compared with space vector based modulation schemes and third harmonic injected sine PWM scheme and the results are presented. The proposed scheme is experimentally validated for a 3hp open end winding induction motor fed with three-level inverters on both sides.

Efficient Sigma-Delta Sensor Array Beamforming.

Nowadays, sensors with built-in sigma-delta modulators (ΣΔMs) are widely used in consumer, industrial, automotive, and medical applications, as they have become a cost-effective and convenient way to deliver data to digital processors. This is the case for micro-electro-mechanical system (MEMS), digital microphones that convert analog audio to a pulse-density modulated (PDM) bitstream. However, as the ΣΔMs output a PDM signal, sensors require either built-in or external high-order decimation filters to demodulate the PDM signal to a baseband multi-bit pulse-code modulated (PCM) signal. Because of this extra circuit requirement, the implementation of sensor array algorithms, such as beamforming in embedded systems (where the processing resources are critical) or in very large-scale integration (VLSI) circuits (where the power and area are crucial) becomes especially expensive as a large number of parallel decimation filters are required. This article proposes a novel architecture for beamforming algorithm implementation that fuses delay and decimation operations based on maximally flat (MAXFLAT) filters to make array processing more affordable. As proof of concept, we present an implementation example of a delay-and-sum (DAS) beamformer at given spatial and frequency requirements using this novel approach. Under these specifications, the proposed architecture requires 52% lower storage resources and 19% lower computational resources than the most efficient state-of-the-art architecture.

Evaluation and Suppression of Oscillations in Inductive Power Transfer Systems With Constant Voltage Load and Pulse Skipping Modulation

This paper identifies how Constant Voltage Load (CVL) characteristics cause Inductive Power Transfer (IPT) systems to exhibit a poorly damped oscillation mode. When operated with pulse skipping strategies such as Pulse Density Modulation (PDM), the skipped voltage pulses can excite this mode and cause severe oscillations that do not appear in systems with a constant resistance load (CRL). The critical mode is identified from a linearized state-space model of the system and two control approaches are proposed for attenuating the oscillations in current amplitude and power flow. Firstly, the influence of the operating frequency on the critical eigenvalue is analyzed and it is shown how slightly off-resonant operation can increase the damping of the oscillation mode. Secondly, an active damping method based on sending current feedback control is studied. The active damping is based on Phase Shift Modulation (PSM) with limited phase shift angles applied to the PDM signal when oscillations are detected. The effectiveness and feasibility of the proposed methods are validated by simulations and experimental results from a small-scale laboratory prototype.

Pulse-Density-Modulated Microwave Generator Using Single-Flux-Quantum Circuits for Controlling Qubits

Superconducting qubits are generally controlled by irradiation with microwave pulses. We propose a 5-GHz-range microwave pulse generator based on pulse density modulation for controlling qubits using single-flux-quantum (SFQ) circuits. The proposed microwave pulse generator comprises a 100-GHz circular shift register and a band-pass filter (BPF). In this study, we investigated the relationship between the target envelope of the microwave amplitude and the SFQ pulse density based on the transfer function for the BPF and the frequency spectrum of an SFQ pulse. We implemented a 64-bit circular shift register and demonstrated its operation up to 68 GHz.

Sub-GHz resolution line-by-line pulse shaper for driving superconducting circuits

We demonstrate a sub-GHz resolution, fully programmable Fourier-domain pulse shaper capable of generating arbitrary optical pulse patterns for superconducting circuit platforms. This high resolution allows line-by-line pulse shaping of a 1 GHz-spaced comb, and the pulse shaper can accommodate an optical bandwidth as large as 1 THz, which represents the highest resolution programmable line-by-line pulse shaping to our knowledge. Linear optical sampling with a dual-comb system confirms independent control of 1 GHz-spaced optical lines, and the low phase noise of the pulse shaper is characterized. We apply the pulse shaper as an optical drive for an array of Josephson junctions operating at a temperature of 4 K, where cryogenic photodetection of pulse doublets with user-defined separation characterizes the Josephson junction response. Furthermore, we demonstrate a pulse-density modulation pattern of 4 ps duration optical pulses that can serve as the high bandwidth drive of a quantum-based Josephson arbitrary waveform synthesizer. By leveraging the exquisite control, large bandwidth, and low noise of photonics, this represents an important advance toward the realization of high power and high spectral purity AC voltage standards at gigahertz frequencies without requiring 100 GHz bandwidth driving electronics.

I-V Characteristics Measuring System for PV Generator based on PDM Inverter

This paper presents a new method to characterize photovoltaic panels. The power electronic converter used is a Pulse Density Modulation (PDM) inverter. In this method, the inverter plays two roles: First, it is a DC inductor emulator. Second, it allows assembly between inductive and capacitive load methods. The PDM inverter is adapted to operate at very high switching frequency. In this application, it avoids the difficulties of making DC inductors with high DC current and its control remains very simple. This is an asset for increasing the power, power density and rapidity of tracers based on this method. The main disadvantage of this method, compared to methods based on DC-DC converter, is the use of twice as many semiconductor components. But this disadvantage can be compensated by a gain on reactive components. The simulations and experimental results of the proposed system are shown.

Efficacious Zero Sequence Voltage Elimination in Space Vector Modulation by Sigma Delta Modulation

The growing popularity of electric motor driven systems emphasize the need for proper motor maintenance and necessitates zero sequence voltage (ZSV) elimination in electrical machines and drives. A spread spectrum modulation scheme for eliminating zero sequence voltage, utilizing space vector pulse density modulation (SVPDM) approach is proposed in this article. In the presented five-level inverter scheme, when vectors that do not contribute zero sequence voltage are considered, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$30^{0}$</tex-math></inline-formula> tilted three-level space vector diagram with inner and outer layer is formed. Reference vector residing in outer layer is mapped to inner layer and is vector quantized in a space vector quantizer to generate inner layer switching vectors. Outer layer switching vectors are then realized by the process of reverse mapping. The article investigates two-level SVPDM scheme and ZSV eliminated two-level SVPDM scheme, to prove that effectiveness of ZSV elimination can be determined from the shape of demodulated waveform. Better the ZSV elimination, better will be the resemblance of demodulated waveform to sinusoidal signal. The scheme is experimentally validated with 2.2 kW five-level dual inverter fed induction motor drive and is compared with space vector pulse width modulation (SVPWM) scheme. Results of comparison confirms the effectiveness of proposed scheme.

High Efficiency and Full MPPT Range Partial Power Processing PV Module-Integrated Converter

To increase the energy yield of PV systems in presence of module level power mismatches, Maximum Power Point Tracking (MPPT) should be performed by converters at module level. Using module level converters at the output of the PV panels adds a constant loss even when there is no power mismatch which increases the overall system losses and compromises part of the energy yield improvement. To decrease this constant loss especially when there is no power mismatch, Partial Power Processing (PPP) concept is used in this paper to achieve a new high-frequency and high-efficiency module integrated PV converter, which can achieve full range MPPT and maximum possible efficiency when there is no mismatch. To overcome the challenge of limited MPPT range for partial power converters a special Pulse Density Modulation (PDM) technique is proposed, which preserves the merits of PPP and renders full range MPPT. A 220 W prototype converter is implemented to justify the converter principal of operation and analyses. The proposed converter reached 99.6% to 96.5% efficiency for the power mismatches in the PV module ranging from 0 to 50% of the maximum module power generation capability, respectively. The efficiency drop is shown to be linear with power mismatch level without any abrupt reductions that is commonly observed in conventional PV module integrated converters.

A self-oscillating series-none inductive power transfer system using a matrix converter

Power density and conversion efficiency are two critical parameters of inductive power transfer (IPT) systems. These parameters are related to the number of components in the power conversion circuit as well as its modulation method. The combination of Midpoint Matrix Converter and pulse-density modulation (PDM) has a potential to improve these parameters, due to a low number of semiconductor switches utilization as well as constant efficiency at the maximum output and partial load operations . In this context, this paper analyzes the performance of a three-phase to single-phase Midpoint Matrix Converter using a Free-wheeling Switch (MMCFS) and the PDM in a high coupling factor series-none IPT application. This converter utilizes on–off control to manage power transfer, which automatically tracks the load resonant frequency. Dynamic and steady-state mathematical equations were derived to represent the converter and the IPT system characteristics. These equations show a relationship between the link efficiency, the link gain, the damping ratio and the coupling factor. A kick-start method and a multistep switching strategy were developed to start and operate the converter, respectively. Additionally, a 150 W MMCFS-based IPT prototype was built to verify the improvement, which demonstrated an efficiency of around 80% at the maximum output and partial load operations.

A Single-Coil Multi-Tapped PDM-Based Induction Heating System for Domestic Applications

The conventional heating system is inefficient as the major part of the heating coil lies out-side the vessel it is placed on. This research article proposes a new single-coil multi-tapped induction heating system. This novel induction heating system is facilitated by a half-bridge resonant converter controlled by zero-voltage switching (ZVS). The multi-tapping winding system ensures an effective heat transfer between the coil and the working vessel with the windings of the induction coil segmented to an equivalent size of the vessel. The pulse density modulation (PDM) scheme employed here as the control proves to be the most versatile one. The whole system is duly simulated for an 850 W IH setup in MATLAB Simulink and implemented as a hardware prototype using a half-bridge resonant converter. The control pulses are developed through the PDM in a PIC16F877A controller. The simulation and experimental results prove the credibility of the proposed induction heating (IH) scheme, and during heavy loading conditions, it outperforms the single-coil IH system by gaining an efficiency of 89.29%