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.

Power supply circuitry and adaptive transient control

Abstract: A control circuitry can be configured to receive an error signal indicating a difference between an output voltage of the power supply and a desired setpoint for the output voltage. According to one configuration, depending on the error signal, the control circuitry initiates switching between operating the control circuitry in a pulse width modulation mode and operating the control circuitry in a pulse frequency modulation mode to produce an output voltage. Operation of the control circuitry in the pulse frequency modulation mode during a transient condition, such as when a dynamic load instantaneously requires a different amount of current, enables the power supply to satisfy current consumption by the dynamic load. Subsequent to the transient condition, the control circuitry switches back to operation in the pulse width modulation mode.

Harmonic Reduction in Inverters by Use of Sinusoidal Pulsewidth Modulation

Abstract: This paper presents a new technique for harmonic reduction in inverters using sinusoidal pulsewidth modulation. In this inverter, the output wave with sinusoidal pulsewidth distribution can be kept in maximum degree of symmetry, and so it offers excellent harmonic control in comparison with any other modulation technique. Detailed analysis shows that the harmonics lower than the ninth (or the thirteenth) are all less than one percent of the fundamental component when the number of pulses per half cycle is over seven (or nine). These results are confirmed by the theoretical data obtained from the natural sampling, and the experimental observations for single-phase full-bridge sinusoidal pulsewidth modulated (SPWM) inverters. It is concluded that by the use of this new technique it is quite easy to design an inverter with a distortion-free sinusoidal output.

Power losses for space vector modulation techniques

Abstract: Space vector modulation (SVM) allows 15% more bus utilization than sinusoidal pulse width modulation (PWM). In addition, variations of the SVM method can offer 33% less switching edges. With power losses in the inverter being a significant concern, a reduction in modulation losses can be a significant benefit. Different SVM techniques are discussed along with the calculations for determining both switching losses and conduction losses in the transistors and diodes. Equations for the average and RMS transistor and diode currents are derived based on a quantitative analysis of the current waveforms. The switching losses are plotted against power factor to illustrate the effect of power factor on switching losses for the various SVM techniques. The results are discussed and compared. In at least one case, an analysis of the strategy can lead to specialized power electronics optimized to the switching strategy.

Use of a chopper and a sigma-delta modulator for downconverting and digitizing an analog signal including information modulated by a carrier

Abstract: To demodulate an analog signal having information modulated by a carrier, the analog signal is chopped by a chopper, the chopped signal is digitized by a sigma-delta analog-to-digital converter to produce a series of digital samples at a sampling frequency, the digital samples are filtered in a digital decimating filter to produce data words, and the data words are modulated by an intermediate frequency signal to produce a detected information signal. The various frequency signals are generated by a phase-lock loop so that the intermediate frequency is the difference between the carrier frequency and the chopping frequency, and both the chopping frequency and the intermediate frequency are sub-multiples of the sampling frequency. Therefore aliases and artifacts caused by the chopper are either cancelled or fall on multiples of the output sampling frequency, and the intermediate frequency signal can be a square wave without generating artifacts that need be removed by filtering of the detected information signal. Preferably the chopper is placed in an analog portion of a feedback loop of the sigma-delta modulator, and an exclusive-OR gate is placed in the digital portion of the feedback loop, so that the gain of the demodulation process becomes independent of the gain of the chopper. The detection process is especially suited for detecting an angular-rate signal from a vibrating quartz angular rate sensor, because the detection process has very high accuracy, resolution, and linearity.

Signal transmission system and method

Abstract: A sub-center type switched-star CATV system network in which a number of transmission signals are transmitted from a central source to a number of sub-centers over a number of sets of optical fibers. In view of the long distances involved, the transmission signals are transmitted in pulse frequency modulation form, one pulse frequency modulation signal being applied to each optical fiber. At each sub-center, each pulse frequency modulation signal is converted into a frequency modulation signal by first frequency dividing the pulse frequency modulation signal and then passing the divided signal through a band-pass filter which eliminates all signal components except the fundamental frequency. The pulse frequency modulated signals may pass through a switch to select the number of transmission signals which ultimately reach the subscribers. The frequency modulated signals are then frequency multiplexed to produce a multiplexed signal and the multiplexed signal is sent to a number of subscribers. A single optical fiber connects a sub-center with each associated subscriber, respectively. At each subscriber, the multiplexed signal is converted back into the selected number of transmission signals.