Topic
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.
Papers published on a yearly basis
Papers
More filters
Patent•
26 Jun 2002TL;DR: In this paper, the sampling period of sampling cycles for pulse width modulation remains constant while the period of switching cycles are varied using random numbers to calculate delays between the start of coincident sampling and switching cycles.
Abstract: A system and method (705) for executing random pulse width modulation in electronic power converters. In accordance with the invention, the sampling period of sampling cycles for pulse width modulation remains constant while the period of switching cycles are varied. The periods of switching cycles (702) are varied using random numbers to calculate delays between the start of coincident sampling and switching cycles.
27 citations
TL;DR: In this paper, a 543 nm He-Ne laser stabilized to iodine using modulation transfer spectroscopy is described, and a beat-frequency comparison between it and a reference iodine-stabilized laser showed that it had a stability better than 2 × 10-12 after 140 seconds.
Abstract: A 543 nm He-Ne laser stabilized to iodine using modulation transfer spectroscopy is described. A beat-frequency comparison between it and a reference iodine-stabilized laser showed that it had a stability better than 2 × 10-12 after 140 seconds. The average frequency difference between the two lasers was only 12 kHz despite the lasers using different stabilization schemes. Two mechanisms for frequency shifts in modulation transfer spectroscopy are discussed, both arising from the presence of amplitude modulation on the phase-modulated saturating beam. The first is produced by the phase modulator itself and the second when the saturating beam propagates through the absorbing medium. For the laser described here, the frequency shifts are smaller than the uncertainty of the frequency measurement (∼ 10 kHz).
27 citations
26 Apr 2004
TL;DR: Ultra narrow band modulation and ultra wideband modulation have common mathematical roots, but the difference is in the baseband pulse width.
Abstract: Ultra narrow band modulation and ultra wideband modulation have common mathematical roots. The difference is in the baseband pulse width. UWB utilizes extremely short energy pulses, with long periods of no signal between pulses. UNB utilizes a continuous wave signal with individual RF cycles removed, or phase altered, to indicate a digital ONE.
27 citations
TL;DR: In this paper, an experimental study of an actively mode-locked erbium-doped all-fiber laser, based on a standing-wave acoustically-induced superlattice modulation, is presented.
Abstract: We report an experimental study of an actively mode-locked erbium-doped all-fiber laser, based on a standing-wave acoustically-induced superlattice modulation. Our experiments involve the characterization of the laser as a function of the active fiber length, and with different types of delay line fibers. The effect of the modulation on the laser performance was also investigated. Narrower pulses were obtained at higher modulation depths, normal dispersion, and shorter lengths of active fiber. Optical pulses of 160 mW peak power and 630 ps temporal width were obtained at 9 MHz repetition rate.
27 citations
04 Mar 2018
TL;DR: In this article, a bidirectional architecture is proposed to implement an on-board charger (OBC) including an interleaved totem bridgeless PFC and a Mode-Switched (MS) DC-DC converter.
Abstract: This paper proposes a bidirectional architecture to implement an on-board charger (OBC) including an interleaved totem bridgeless PFC and Mode-Switched (MS) DC-DC converter. In the charging mode with the relay on, the MS DC-DC converter behave as a high efficiency Pulse Frequency Modulation (PFM) LLC converter since the charging mode is the most majority application scenario for the OBC. The PFC output voltage is regulated between 360 V to 400 V feeding into the DC-DC converter, so that 900 V SiC MOSFETs can be used both in the AC-DC and DC-DC stage to realize high frequency and high efficiency owing to the fast switching speed and high voltage rating with low on-resistance. The synchronous rectification (SR) is applied on the secondary side MOSFETs of the LLC converter to further improve the efficiency taking advantage of the bidirectional full-bridge topology. In the discharging mode with the relay off, the MS DC-DC stage is a two-stage converter. The reverse operation of the LLC converter operates as a DC-DC transformer (DCX) at the resonant point, and its output voltage is regulated to the bus voltage by a boost converter because the reverse gain of the LLC converter is lower than 1. A 6.6 kW SiC MS bidirectional OBC of DC-DC stage is built. In the charging mode, the peak efficiency is 96.37% at 6.6 kW with 380 V input voltage and 336 V output voltage. In the discharging mode, the peak efficiency is 96.87% at 3.3 kW with 346 V input voltage and 380 V output voltage.
27 citations