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.
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Patent•
02 Nov 2006TL;DR: In this paper, a method for varying the type of modulation employed for a pulse width modulation (PWM) signal is presented. But the method is limited to a power converter system having a load.
Abstract: In one embodiment, in a power converter system having a load, a method is provided for varying the type of modulation employed for a pulse width modulation (PWM) signal. The method includes the following: monitoring the load of the power converter system; using leading edge modulation for the PWM signal under light load condition; and using trailing edge modulation for the PWM signal under heavy load condition; thereby optimizing operation of the power converter system.
18 citations
15 Oct 2000
TL;DR: In this article, a new control method of a piezoelectric transformer (PT) converter by PWM and PFM was presented, where the combination of an active-clamp circuit and a resonant circuit makes it possible to control the output voltage of the PT converter at a fixed switching frequency and a fixed duty ratio.
Abstract: A new control method of a piezoelectric transformer (PT) converter by PWM and PFM is presented. The combination of an active-clamp circuit and a resonant circuit makes it possible to control the output voltage of the PT converter by PWM at a fixed switching frequency and PFM at a fixed duty ratio. The PT converter implemented on a printed circuit board was experimentally evaluated and a good controllability was successfully achieved.
18 citations
Patent•
03 Oct 2012
TL;DR: In this paper, a backlight dimming method is proposed for 1D and 2D backlight driving circuits, which comprises the following steps that: a determination module of a main control unit acquires a pulse signal duty ratio according to a gray scale value of a picture to be displayed and compares the duty ratio with a set duty ratio threshold value.
Abstract: The invention discloses a backlight dimming method, which comprises the following steps that: a determination module of a main control unit acquires a pulse signal duty ratio according to a gray scale value of a picture to be displayed and compares the duty ratio with a set duty ratio threshold value; when the duty ratio acquired by the determination module is greater than the duty ratio threshold value, a pulse width modulation (PWM) signal generation module of the main control unit generates a PWM signal and outputs the signal to a light dimming controller; when the duty ratio acquired by the determination module is smaller than the duty ratio threshold value, a pulse frequency modulation (PFM) signal generation module of the main control unit generates a PFM signal and outputs the signal to the light dimming controller; and the light dimming controller performs light dimming according to the input PWM signal or the input PFM signal. The invention also discloses a corresponding backlight driving circuit. When required output backlight current is relatively low, the working efficiency of the system can be effectively improved; the power consumption is reduced, the electromagnetic interference (EMI) is reduced, and the color temperature consistency of a light emitting diode (LED) backlight source during working at low current is improved; and when the backlight dimming method is applied to 1D dimming and 2D dimming, an effect is relatively good.
18 citations
01 Jan 2006
TL;DR: In this article, the authors present the analysis of the modulation strategies for the AC/DC line-side converters and examine the influence of the discussed modulation methods on the line current distortion and the switching frequency.
Abstract: The paper presents the analysis of the modulation strategies for the AC/DC line-side converters. The application of the different modulation methods to the control system of the AC/DC converter has been presented. The operation of the AC/DC converter in different dynamic states strongly depends on the modulation method applied. The theoretical background of Hysteresis-Band Modulation, Carrier-Based Sinusoidal Modulation and Space-Vector Modulation has been presented. The issue of overmodulation has been discussed. Voltage Oriented Control of the AC/DC line-side converter has been chosen to examine the presented modulation methods. The influence of the discussed modulation methods on the line current distortion and the switching frequency has been examined. The simulation results of the presented techniques have been demonstrated and concluded.
18 citations
TL;DR: In this paper, the frequency modulation due to injection current modulation of vapor phase transported distributed feedback (VPT DFB) semiconductor lasers is measured as a function of modulation frequency from 10 kHz to 1 GHz.
Abstract: The frequency modulation (FM) due to injection current modulation of vapor phase transported distributed feedback (VPT DFB) semiconductor lasers is measured as a function of modulation frequency from 10 kHz to 1 GHz. A large frequency modulation response of 350 MHz/mA is obtained for the modulation frequency range of 10 to 1000 MHz. Demodulation of optical frequency shift keying (FSK) at 560 Mb/s is demonstrated, indicating that frequency modulation due to thermal modulation does not pose a significant limitation at this bit rate or higher. The large FM response together with modulation bandwidths up to 8 GHz makes the VPT DFB laser an attractive source for high bit rate optical FSK transmission.
17 citations