Joined in 2023 
82 
63 About this deal
The (A) signal graph shows the filter effect of the capacitor. When the waveform reaches its highest point, the capacitor will charge up. Then, the waveform will start to drop. At the same time, the capacitor will discharge, filling the gap between each highest point of the waveform. The operating frequency of an unloaded SMPS is sometimes in the audible human range and may sound subjectively quite loud for people whose hearing is very sensitive to the relevant frequency range. It is one of the ways to connect the transformer with the input and output. When we use it on the switching power supply circuit, we would need a transformer with a high frequency of 20 kHz or more. a b c Foutz, Jerrold. "Switching-Mode Power Supply Design Tutorial Introduction". Archived from the original on 2004-04-06 . Retrieved 2008-10-06. Sha, Zhanyou; Wang, Xiaojun; Wang, Yanpeng; Ma, Hongtao (2015-06-15). Optimal Design of Switching Power Supply. John Wiley & Sons. ISBN 978-1-118-79094-6.
Mild high-frequency interference may be generated by AC rectifier diodes under heavy current loading, while most other supply types produce no high-frequency interference. Some mains hum induction into unshielded cables, problematic for low-level audio signals. a b ON Semiconductor (July 11, 2002). "SWITCHMODE Power Supplies—Reference Manual and Design Guide" (PDF) . Retrieved 2011-11-17. Extremely large peak "in-rush" surge current limited only by the impedance of the input supply and any series resistance to the filter capacitors. Ban Looms for External Transformers". Archived from the original on 2019-05-15 . Retrieved 2007-09-07. Note that this is not perfect. When connected to a heavier load, the capacitor discharge cannot keep up with filling the gap anymore.The inverter stage converts DC, whether directly from the input or from the rectifier stage described above, to AC by running it through a power oscillator, whose output transformer is very small with few windings, at a frequency of tens or hundreds of kilohertz. The frequency is usually chosen to be above 20kHz, to make it inaudible to humans. The switching is implemented as a multistage (to achieve high gain) MOSFET amplifier. MOSFETs are a type of transistor with a low on- resistance and a high current-handling capacity. Like other power supplies, an SMPS transfers power from a DC or AC source (often mains power, see AC adapter) to DC loads, such as a personal computer, while converting voltage and current characteristics. Unlike a linear power supply, the pass transistor of a switching-mode supply continually switches between low- dissipation, full-on and full-off states, and spends very little time in the high dissipation transitions, which minimizes wasted energy. A hypothetical ideal switched-mode power supply dissipates no power. Voltage regulation is achieved by varying the ratio of on-to-off time (also known as duty cycles). In contrast, a linear power supply regulates the output voltage by continually dissipating power in the pass transistor. The switched-mode power supply's higher electrical efficiency is an important advantage. Energy Savings Opportunity by Increasing Power Supply Efficiency". Archived from the original on 2010-10-25 . Retrieved 2008-12-22.
In 2001, the European Union put into effect the standard IEC 61000-3-2 to set limits on the harmonics of the AC input current up to the 40th harmonic for equipment above 75W. The standard defines four classes of equipment depending on its type and current waveform. The most rigorous limits (class D) are established for personal computers, computer monitors, and TV receivers. To comply with these requirements, modern switched-mode power supplies normally include an additional power factor correction (PFC) stage. Simple off-line switched mode power supplies incorporate a simple full-wave rectifier connected to a large energy-storing capacitor. Such SMPSs draw current from the AC line in short pulses when the mains instantaneous voltage exceeds the voltage across this capacitor. During the remaining portion of the AC cycle the capacitor provides energy to the power supply. Active/passive power factor correction in the SMPS can offset this problem and are even required by some electric regulation authorities, particularly in the EU. The internal resistance of low-power transformers in linear power supplies usually limits the peak current each cycle and thus gives a better power factor than many switched-mode power supplies that directly rectify the mains with little series resistance. Kilbane, Doris (2009-12-07). "Robert Boschert: A Man Of Many Hats Changes The World Of Power Supplies". Electronic Design . Retrieved 2019-09-12.Metal Oxide Semiconductor (MOS) Transistor Demonstrated". The Silicon Engine. Computer History Museum . Retrieved August 31, 2019.
Great Deal 
New Comment