Pulse-frequency modulation

About: Pulse-frequency modulation is a research topic. Over the lifetime, 4151 publications have been published within this topic receiving 53039 citations. The topic is also known as: PFM.

Sinusoidal and Space Vector Pulse Width Modulation for Inverter

Abstract: Inverters inherently have the property of controlling output frequency but the output volt- age can't be varied. Usually to vary output voltage we have to vary supply voltage which is not always possible for this reason PWM techniques gained momentum. Basic aim of PWM technique is to control output voltage and harmonic reduction. Pulse-width modulation (PWM), or pulse- duration modulation (PDM), is a commonly used technique for controlling power to inertial electri- cal devices, made practical by modern electronic power switches. Here we apply PWM techniques like Sinusoidal pulse width modulation (SPWM) and Space Vector Pulse width Modulation (SVPWM) to inverter and study its performance. In Sinusoidal Pulse width modulation (SPWM) we generate the gating signals by com- paring a sinusoidal reference signal with a trian- gular carrier wave. In Space vector Modulation (SVPWM) we consider a rotating phased which is obtained by adding all the three voltages. Modula- tion is accomplished by switching state of an in- verter. Thus by comparing these two techniques we study the performance of our inverter.

The Questions of Circuitry Design when Forming the Switching Functions of the Control System of the Matrix Frequency Converter

Abstract: The switching function generator of the matrix frequency converter control system is described. This device can be used in the control systems of frequency-controlled AC drives and special consumers. The output voltage of the matrix frequency converter is generated by this device on the principle of amplitude modulation of the reference sinusoid by steps that are formed from the twelve-phase input voltage sections. The described device enables to generate the output voltage in the range from extremely low frequencies up to the frequency of 150 Hz. At the same time in the low frequency region up to 15 Hz the total harmonic distortion of output voltage complies with the value specified in GOST 13109-97. The frequency range above 15 Hz requires the use of pulse-width modulation to shift the higher harmonics to the high frequency region. The device design consisting of individual identical blocks allows simplifying the manufacturing process, and applying modular technology in the manufacture and maintenance of the device itself and the entire control system in general.

A compact spectrum constant envelope digital phase modulation

Abstract: A digital modulation system with compact spectrum and constant envelope is proposed, based on the results of theoretical and experimental studies. This modulation system is suitable for digital mobile communication, which generally is subject to deep and rapid fading. It is characterized with a possibility of practical and stable instrumentation. In the modulator, modulation signal parameters are read out of the memories, by which precise spectrum and waveform can be realized. For the modulator, an orthogonal phase modulation, whose parameters are stable, can be adopted by pertinent parameter design for the modulating signal stored in the memories. The experimental results agree well with the design.

A New Control Circuit Extends the Effective Duty Cycle Range of Flyback Converters

Abstract: Voltage source flyback converters in the discontinuous conduction mode with a new control strategy is presented in this paper, that is capable of operating over a wide range of input and output voltage variation Over the normal range, pulse width modulation at fixed frequency is used as in conventional system At low duty cycle demands, constant pulse width with variable frequency is used to extend the effective duty cycle range

R.F. spectra of waves frequency modulated with white noise

Abstract: Although comprehensive sets of curves are available giving the radio-frequency spectra of waves phase modulated with band-limited white noise (simulating f.d.m. telephony signals), the corresponding problem for frequency modulation turns out to be much more intractable. In the present paper the frequency-modulation problem is attacked using a method employed in an earlier paper, in conjunction with numerical devices for improving the convergence rate of very slowly converging series. The results are presented as a set of curves covering the range of modulation parameters likely to be encountered in trunk radio systems. This information is necessary for the evaluation of system bandwidth and interference due to unwanted carriers. To bring the analysis within reasonable bounds, the minimum modulating frequency has been taken as zero. It is known that unless the ratio between r.m.s. frequency deviation and maximum modulating frequency is large, the shape of the central portion of the spectrum changes substantially as the minimum modulating frequency departs from zero. However, for practical ranges of parameters there is evidence indicating that the shape of the spectrum tails (which is of particular importance in connection with distortion problems) is not greatly sensitive to variations in the minimum modulating frequency.