2025年2月20日 · 本文详细介绍了开关电源的三种主要调制方式：PWM（脉冲宽度调制）、PFM（脉冲频率调制）和PSM（脉冲跨周期调制）。 PWM通过调整脉冲宽度保持恒定频率，适用于重负载，但轻负载效率低。 PFM则在轻负载时效率高，通过改变频率调整输出。 PSM结合了PWM和PFM的特点，轻负载时效率高且开关损耗与输出功率成正比。 现代电源控制器常采用PWM和PFM混合模式，以实现全负载范围的高效运行。 1. PWM/PFM/PSM 三种控制模式的 …

Pulse-frequency modulation (PFM) is a modulation method for representing an analog signal using only two levels (1 and 0). It is analogous to pulse-width modulation (PWM), in which the magnitude of an analog signal is encoded in the duty cycle of a square wave.

2022年4月11日 · This article will outline the differences between zirconia crowns and PFM crowns, highlighting their strengths, weaknesses and ideal uses.

modern DC/DC converters implement pulse frequency modulation (PFM), and as the output load current increases the mode of operation transitions to forced frequency pulse modulation (FPWM). This application note discusses the mode transitions and expected switching waveforms of LMR33620/30 and LMR36006/15.

2016年3月14日 · Efficiency characteristics of PWM and PFM illustrated. PWM, switching at fixed cycles even during a light load, can be low in efficiency. PFM, which operates by reducing the frequency under a light load, cuts switching losses and maintain a high efficiency.

2014年3月25日 · This article describes how PFM works, explains its benefits and some of its disadvantages, and then considers how some silicon vendors implement the technique in their integrated power chips. PWM vs. PFM PWM is not the only technique for regulating the output of a switching converter.

2023年9月27日 · When less load current is needed, PFM improves efficiency. The lower switching frequencies that occur under these conditions are less likely to cause problematic interference. When more load current is needed, however, PWM facilitates noise countermeasures without reducing efficiency through excessive switching.

Metal-ceramic FDPs demonstrated better outcomes in terms of framework and veneering material fracture resistance. The amount of identified marginal discrepancies increase with the size of the zirconia FPD span, whereas PFM calls for a time-consuming reduction.

2022年8月23日 · Learn when to use zirconia crowns and when to use PFM crowns for your next restorative case. To provide the best care possible for patients in need of restorative work, dentists must understand when to deliver zirconia crowns or PFM crowns.

For 50 years, PFM restorations have been the main type of esthetic indirect restoration used in dentistry. Zirconium-based all-ceramic restorations are emerging as an alternative to PFM restorations. In this article, I compared the two types of restorations relative to soft-tissue compatibility, strength of restorations, service record to date ...