Abstract: A new control technique based on dead beat control theory to obtain a nearly sinusoidal PWM inverter output voltage is described. The closed-loop digital feedback system measures the output and controls the inverter switches to generate the required pulsewidth-modulated (PWM) pattern to produce low total harmonic distortion (THD) sinusoidal output voltage. This scheme inherently provides very good voltage regulation, phase positioning, and compensation for load disturbances and nonlinear loads. A theoretical analysis, computer simulation, and experimental results for a single-phase bridge inverter controlled by an Intel 8086 microprocessor-based system is presented.

Abstract: The switching lag-time that prevents the phase shortage of inverter arms causes serious waveform distortions and fundamental voltage drops in pulsewidth-modulated inverter output. Distortions in the PWM inverter-fed induction motor system over the various frequencies of the carrier are investigated and a correction circuit with PWM potential feedback is proposed; the effectiveness of that circuit is shown by experiments.

Abstract: This paper proposes new method of high performance current and/or voltage control of three phase PWM inverter, especially suitable for high speed switching devices such as Transistor and BIMOS. As the controller for calculation of the dead beat algorism, a high speed digital controller, such as the digital signal processor is assumed. Following new methods are successfully adopted and combined to realize high quality. (1) Three phase inverter current and voltage are transformed to synchronizing d-q-0 frame, and discretized equations of current and voltage are derived, which clearly reveal coupling of voltage and current of inverter on d-q frame. (2) Using above discretized equation of main circuit, algorism of Dead Beat control with compensation for decoupling is developed. (3) New method for compensation of computing time delay and full utilization of sampling interval for inverter output pulse width is developed, which utilizes 2nd order load current prediction and discretization with twice time of sampling period. (4) Double Dead Beat control system is developed for sinusoidal output voltage inverter, which has high speed current minor loop to constrain inverter current within safety limit. Validity of these techniques has been confirmed by simulation using a hybrid computer.

Abstract: An active power filter using quad-series voltage-source PWM converters is used to suppress ac harmonics by injecting PWM modulated currents to the ac side. In this paper, the calculation circuits for the harmonic currents to be injected, the compensation characteristics, and the capacity of the dc capacitor are discussed. A new control circuit for the dc capacitor voltage is proposed. These discussions focus on transient states and are on the basis of the instantaneous reactive power theory. Finally, a passive LC filter is designed to remove the switching voltage and current ripples caused by the PWM converters at the ac side. Some experiments to illustrate the details of the study are shown.

Abstract: A pulsewidth modulation (PWM) control technique suitable for fully controlled three-phase ac/dc converters is analyzed, which gives sinusoidal input currents and ideally smoothed dc voltage. The technique allows four-quadrant operation and full-range control of the input power factor. An extension to a simplified converter scheme, capable of one-quadrant operation, is also considered. Operation of the converter is analyzed under both ideal and actual conditions. Control implementation and design criteria are discussed and experimental results are reported.

Abstract: A method of obtaining the exact solution to the nonlinear equations for eliminating several lower-order harmonics in the output voltage of a PWM inverter is illustrated. This procedure permits the widespread use of this technique in the entire frequency range in power control.

Abstract: Quasi-resonant converters are a recently introduced family of single-switch resonant converters featuring zero-current or zero-voltage switching. Recognition of the topological structure uniting these converters — and the PWM converters on which they are based — leads to general models of their dc and low-frequency ac behavior. An expression is derived that yields the dc conversion ratio of a quasi-resonant converter in terms of the well-known conversion ratio of the underlying PWM topology. A small-signal, low-frequency dynamic model is developed whose parameters also incorporate the PWM conversion ratio. The dc and ac models reveal that any quasi-resonant converter with a full-wave resonant switch has dc and low-frequency behavior identical to that of its PWM parent, with switching frequency control replacing duty ratio control. Converters with half-wave resonant switches act more like PWM converters under current programming or discontinuous conduction mode, exhibiting lossless damping in the small-signal model and output resistance at dc.

Abstract: The modulation and differential detection characteristics of optical CPFSK transmission systems are investigated both theoretically and experimentally. The error rate expressions of differentially detected CPFSK are derived by considering phase noise of LD's. It is clear that the linewidth requirement is less than 0.68 m percent of the bit rate, where m is modulation index. The performances of CPFSK are then experimentally presented at 400 Mbit/s using external optical feedback DFB LD's as the optical source. A beat spectral linewidth of less than 200 kHz for the transmitter and local oscillator LD's is achieved. The frequency response nonuniformity of frequency modulation efficiency is compensated by electrical circuits within 3 dB and 60°. To reduce IF thermal noise, a resonance-type preamplifier is used, with a 4.8 pA/ \sqrt{Hz} average input noise current density, and a receiver sensitivity 1.3 dB better than the conventional preamplifier. Differential detection of the 400-Mbit/s CPFSK modulation is performed. The generation of CPFSK is confirmed by good correlation between the output spectrum and theory. The average received optical power at a 10-9bit error rate is -49.9 dBm which improves direct detection by 10.3 dB. No additional power penalties due to 290-km transmission exist.

Abstract: An analysis is presented of a voltage source delta modulation (DM) inverter. The delta modulation method provides several advantageous characteristics over commonly used sine modulation process. It is relatively easy to implement and provides low harmonics at the inverter output. The inherent features of the delta modulation also provide control of ratio of voltage to frequency and commutation numbers of an inverter without much complexity in control circuit. These and other features of DM inverters are investigated theoretically and verified experimentally. Successful implementation of DM techniques in three-phase inverters are reported.

Abstract: An electrostatic precipitator is supplied with a d-c voltage of variable level upon which is superimposed a series of voltage pulses. For each voltage pulse, the difference between a positive current-time area and a negative current-time area beneath a current-voltage curve is determined and maximized by changing the pulse amplitude, pulse width, pulse repetition frequency and/or the rate of pulse rise. In addition, the d-c voltage is controlled to have a value at a point of maximum slope of the function of precipitator current with respect to the magnitude of the d-c voltage.

Abstract: Two controlled-current pulsewidth-modulated (PWM) converters have been integrated into rectifier-inverter links of variable-speed ac motor drives. The authors focus on developing a mathematical model of the rectifier-inverter link and presenting experimental justification of the model. The characteristics of the rectifier-inverter system and the constraints imposed by the voltage feedback loop and dc link voltage are discussed. The rectifier-inverter system is made to drive a "selfcontrolled" synchronous motor, thus forming a system for which both the utility and the motor currents are near sinusoidal. The optimized power conversion capability of the motor is now matched by unity power factor operation on the rectifier side. Fast reversal from motoring to regenerative braking capability is demonstrated experimentally.

Abstract: A ballast for controlling the light emitted by fluorescent lamps (25) is disclosed. DC power derived from either a DC source or a rectified AC source is switched on and off at a high frequency rate by a switch (15) to control the flow of current through the primary winding of the transformer of a flyback converter (27). The switched output is rectified and applied by the flyback converter to the filaments of the fluorescent lamps (25) to be controlled. The rectified, switched output is also applied by a π filter (17) to a commutator circuit (21) that controls the starting of the fluorescent lamps (25). The commutator circuit (21) is switched at a lower frequency rate. The bridge input voltage and current are sensed and fed back to a control circuit (23), which includes a regulating pulse width modulator and a bridge switching circuit. The control circuit (23) also receives a pulse current feedback signal from the switch (15) and an external dimming control signal. The control circuit (23) controls the application of high frequency switching signals to the switch (15) that controls the application of power by the flyback converter based on the voltage, current and pulse current feedback signals. Which one of these three signals actually controls is determined by which signal first reaches a reference level. If the magnitude of the feedback voltage first reaches the magnitude set by an open circuit voltage reference, the feedback voltage signal controls. If the magnitude of the feedback pulse current signal first exceeds a predetermined magnitude, the feedback pulse current signal controls. If the feedback current first exceeds a reference magnitude controlled by the external dimming control, the feedback current signal controls.

Abstract: A harmonic suppressing device provided in a power system such as, for example, a transmission and distribution system or a power generating system, to filter higher harmonic currents generated by a higher harmonic current source of the power system such as, for example, a cycloconverter. The harmonic suppressing device comprises, as the principal components thereof, a passive filter serving as a high-order higher harmonic filtering unit for filtering higher harmonic currents of comparatively high order among those generated by the higher harmonic current source, and an active filter serving as low-order higher harmonic filtering unit for filtering higher harmonic currents of comparatively low orders among those generated by the higher harmonic current source. The active filter comprises: a main active filtering circuit comprising a plurality of switching transistors, rectifying diodes combined with the switching transistors, respectively, a capacitor, and a reactor; an operating circuit which calculates controlling data for controlling the commutating action of the main active filtering circuit on the basis of the detected values of the higher harmonic currents that flows into the power source side of the power system and the detected values of the output voltage of the higher harmonic current source; and a control circuit which gives control signals such as, for example, pulse width modulating signals to the main active filtering circuit. The harmonic suppressing device is capable of filtering higher harmonic currents in a wide frequency band.

Abstract: An uninterruptible power supply device uses a transformer with a first primary winding and secondary winding tightly coupled to one another to transmit AC input electrical power to a voltage sensitive load. A series regulator switches taps in the first primary to keep the load output voltage within certain limits during minor variations in the AC input voltage. A standby inverter supplies standby power to the load after a loss or large variation in the AC input voltage by driving PWM pulses into a secondary primary winding of the transformer. The transformer loosely couples the second primary winding to the secondary winding to aid in synthesizing the output sinusoidal wave from the PWM pulses. The regulator opens all of the taps to prevent the inverter from supplying power to the AC input. A voltage monitor continuously senses the AC waveform of an AC sample signal produced from the output load voltage in the normal mode and from the AC input voltage in the standby mode to determine forward and reverse transfers between modes. A clipped AC sample signal detector inhibits transfer in high peak current conditions, and a digital phase-locked loop circuit operating at a fraction of the AC input frequency synchronizes the phase of a precision sine wave signal with the phase of the AC input voltage.

Abstract: A pulse width modulation control system for an electronically commutated motor (ECM) adapted to be energized from a DC power source includes a power switching system coupled in circuit with each winding stage terminal of the ECM for selectively coupling each terminal to the DC power source for applying a DC voltage to selected ones of the winding stages of the ECM in a preselected sequence to effect energization of the ECM. The control system includes signal processing circuitry for generating switching signals for identifying selected power switching devices for energization in order to connect each terminal of the ECM to the power source in the preselected sequence. A pulse width modulation (PWM) circuit generates PWM enables signals for energizing the selected power switching devices and includes a clock for generating periodic clock signals defining sequential clock intervals of predetermined duration. A logic circuit is coupled to the PWM circuit for limiting the cycling of the PWM enable signal to once per clock interval.

Abstract: One of the major problems in inverter-fed motors is the high level of audible noise produced by harmonic current and voltage components To analyze these phenomena the field in the machine airgap is calculated using the rotating field theory together with the Maxwell stress theorem This analysis yields a way for predicting the spectrum components produced by the motor and for relating it to the airgap flux density distribution time harmonics caused by the nonsinusoidal supply The theoretical approach is used for calculating the airgap flux density distribution and the frequency spectrum components of a small three-phase squirrel-cage induction motor fed by a six-step voltage source inverter (VSI) and by a pulsewidth-modulated (PWM) inverter The theoretical results are compared with experiments

Abstract: The development of digital devices has led to the production of PWM inverters for driving induction motors having high-frequency carriers over 10 000 Hz. However, the popular digital devices exhibit difficulties in arriving at the precise switching instants because of limitation of available memory capacity and of bits, especially in the low-frequency region. Basic discussions on the magnetic flux and torque ripple and an introduction to a memory-saving and low-torque-ripple new PWM (split zero vector) method are given. The experiments show fairly good current waveforms, low iron loss, and low acoustic noise.

Abstract: It is usual to provide a short “dead time” between switching one device in an inverter leg off and switching the other device on, to prevent them conducting simultaneously. It is known that this expedient modifies the harmonic content of the output voltage waveform of a pulse-width modulation (PWM) inverter. It changes the amplitude of the fundamental component, which can be significant in variable-speed drives when the frequency ratio is changed. It also introduces low-amplitude, low-order harmonic components which are not wanted in uninterruptible power supplies when voltage waveforms of high purity are demanded. This problem has been treated quantitatively and it has been shown by a systematic set of experiments that the proposed theoretical method is reliable. It has been found that the amplitudes of the odd harmonics produced depend only upon the ratio of the dead time to the period of the switching frequency. Similarly the amplitudes of the even harmonics, which only occur with even frequency ratios, depend on the ratio of the dead time to the period of the fundamental frequency. Accordingly it has been possible to present generalised curves which allow the design engineer to estimate the amplitudes of these harmonics for any combinations of fundamental and modulating frequencies. These results have been presented in such a way that they are applicable to both single-phase and 3-phase PWM inverters.

Abstract: A numerical model which simulates the mode partition noise in semiconductor lasers under CW as well as pulsed operation is presented. The noise levels in the individual modes under CW operation are in agreement with those predicted by an analytic small-signal model. Under simulated pulse modulation with pulse repetition frequencies of 633 MHz and 2.2 GHz, the probability density functions for the relative photon numbers in the individual modes are found. The data allow for an evaluation of the mode partition parameter k . For the central modes, k factors are in the range of 0.31-0.42, depending on bias level and modulation frequency. Weaker side modes carrying less than 5 percent of the total output have k factors smaller than 0.16.

Abstract: The calculation of power losses in high-power bipolar transistors is examined for several of the commonly encountered types of power circuits. The magnitude of switching and conduction losses is dependent on the type of circuit in which they are used, the type of load, switching frequency, and characteristics of the transistor itself. Curves, based on computer simulation and mathematical analysis, are presented to aid in the calculation of these losses. Parameters taken into account are dynamic saturation voltage, load power factor, effect of snubbers, and recovery characteristics of circuit associated diodes.

Abstract: The pulse width modulation (PWM) technique has been revisited and analyzed to evaluate its merits for application to analog signal transmission in fiber-optic links. Fourier analysis of the PWM signal reveals that it can be used as a vehicle to launch an analog signal onto optical fiber when a symmetrical natural sampling process is used. The SNR of the modulated signal depends on the timing jitter of the carrier pulses and a wide-band (45 MHz) SNR of 45 dB has been obtained with a commercially available multimode laser transmitter. A linear dynamic range of over 50 dB has been experimentally demonstrated. The full fiber bandwidth can be utilized by using a very high pulse carrier frequency, while a more popular pulse frequency modulation technique provides about a 10-MHz analog signal bandwidth when 1 km of multimode fiber is used in conjunction with a short wavelength (0.87 μm) LED transmitter. Analog transmission capability was experimentally demonstrated by constructing a simple video link using common laboratory equipment. The performance of the video link supports the PWM modulation theory developed here and elsewhere. The experimental results indicated that PWM is potentially very attractive for low-cost broad-band local area network (LAN) application, including future highly interactive offices, hospitals, and automated factory floors.

Abstract: There is disclosed herein a modular, high power, flyback transformer based power supply with step up and step down capability. The power supply uses multiple flyback transformers having switching transistors which may be either connected to one terminal of the primary winding or which may be placed in the center of the primary winding. The switching transistors are driven by pulse trains which are out of phase with each other. This results in lowered RMS values for ripple current through the input and output capacitors. The flyback voltage transients may be used to step up or step down the input voltage by varying the pulse width of the pulse in the switching pulse trains. In embodiments where the switching transistors are placed in the middle of the primary windings, better suppression of radio frequency emissions and current in safety ground wires is achieved. There is also disclosed a combination of such power supply modules in series or parallel on either the input or output to deliver higher power or higher output voltage or to be able to handle higher levels of D.C. input voltage. There is also disclosed an improved an improved flyback transformer design having substantially lower leakage inductance using coaxial cable as the wire from which the primary and secondary windings are made.

Abstract: A GTO current source inverter which consists of six main GTO's, two auxiliary GTO's, and three capacitors is presented. This inverter can supply both the sinusoidal voltage and current to the motor by pulsewidth modulation (PWM) techniques. The normal PWM pattern produced by two control signals with the carrier and the modulating waves and the optimal PWM pattern determined by the harmonic analysis are described. The experimental waveforms for 2.2-kW induction motor drives are given and the circuit operation of this inverter in the PWM technique is clearly shown. In addition, the steady-state characteristics of this inverter-induction motor drive system are analyzed by the state-variable methods, and a close agreement between the analyzed and the experimental waveforms is obtained. It is shown that the harmonic components are eliminated or reduced by using the optimal PWM pattern, and the new inverter with sinusoidal current and voltage is very excellent for ac motor drive.

Abstract: A new method of direct inverter pulsewidth modulation (PWM) is described. In this technique the pulsewidths are determined by equating the incremental areas of the reference signal with the output pulse areas. This PWM method is compared to conventional methods, such as the natural PWM and the regular PWM, which are based on geometrical constructions. Harmonic analysis shows that the direct PWM method has less harmonic distortion that the other methods. Moreover, this technique is particularly suitable for microprocessor-based implementation since the pulsewidths are computable in real time from simple analytic expressions. It is shown that the output pulsewidths are directly proportional to the reference amplitude and inversely proportional to frequency. Therefore, constant volts/hertz operations and other modes of operation can be implemented very simply with a minimal storage requirement.

Abstract: The controlled-current PWM converter has the capability of delivering near sinusoidal current waveforms with unity and even leading power factors. This paper describes its transient characteristics when operated with a simple proportional feedback control to ensure regulated dc voltage output. Experimental tests show that it has fast step response and that it survives abnormal operational conditions such as brown-outs and loss of a single phase.

Abstract: A pulse width modulation control unit for energizing a vehicle head lamp. During daylight operation of a motor vehicle the control unit energizes the head lamp by pulse width modulating the battery output and coupling the modulating output across the head lamp. As battery voltage changes the pulse width modulation is adjusted to maintain power output of the head lamp. An over current condition in a switching transistor is monitored and used to de-activate the pulse width modulation of the head lamp energization.

Abstract: PURPOSE:To obtain the output of a high picture quality even when a memory capacity and the data capacity at the time of communication are small by converting to the multi-value data of the prescribed number of the bit with a multi-value circuit after the input image data of the prescribed bit are binarized, stored into a memory and transferred through a communicating line. CONSTITUTION:The data of one picture element 8 bits outputted from a digital data output device 1 are half-tone-processed by using an organizational dither method or an average error minimum method at a binarization processing circuit 2, converted to the binary data of one picture element one bit, and thereafter, stored into a memory device 3. The binary data outputted from the memory device 3 are inputted to a multi-value circuit 4, converted to the multi-value data of the one picture element 8 bits again and transferred to a PWM circuit 5. At the PWM circuit 5, a pulse width modulating processing is executed to the inputted picture element data of 8 bits and the data are outputted as a pulse width modulating signal (PWM signal) to a terminal 39. The numeric value on respective lines displays the number of the bit.

Abstract: The PWM-controlled circuit includes an up/down counter and utilizes the fact that, when a numerical value is a complementary binary value, the sign is indicated by its most significant bit (sign bit). In the PWM control circuit, the up/down counter is controlled so that when its preset input receives a reference signal, a PWM signal of a duty factor proportional to the reference signal is directly obtained from the most significant bit of the output count.

Abstract: Optical frequency-shift-keying (FSK) signals are obtained from directly modulated distributed feedback (DFB) semiconductor lasers. Experimental studies of the direct frequency modulation (FM) characteristics of the DFB lasers show a nonuniform FM response due to the competing effects of thermal modulation of the laser active region and carrier density modulation. Equalization of the signal current to the laser is employed to produce a flat FM response from 30 kHz to 1 GHz. Optical FSK transmission and heterodyne detection experiments at 560-Mbit/s and 1-Gbit/s are conducted at a wavelength of 1497 nm. Receiver sensitivities of -39 dBm at 560 Mbit/s and -37 dBm at 1 Gbit/s are obtained. Transmission through 100 km of single-mode fiber at 1 Gbit/s is achieved with no degradation in receiver sensitivity.