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1. The noise generated by the switching transistor switching operation High-frequency switching power supply switching power supply transistor in the pulse current, the output of the positive and negative excitation converter and DC overlap regression converter are almost square wave, which contains rich harmonic In the wave, a current oscillates due to the leakage inductance of the transformer and the recovery characteristics of the output rectifier diode when the switch is connected, and a surge voltage is generated on the diode. When the switch is turned off, high-frequency oscillating voltages, that is, surge voltages, are also generated due to parasitic inductance and parasitic capacitance.
2. Noise generated by rectifier diode recovery characteristics When a PN junction type silicon diode is used for high-frequency rectification, the charge accumulated by the forward current cannot be eliminated immediately when the reverse voltage is applied. Due to the accumulation effect of carriers, the diode flows through the diode. When the current is reversed, if the current rise rate di/dt is large when the reverse current is restored, a large spike voltage is generated due to the inductance, which is the so-called recovery noise.
3. The noise generated by the transformer flows through the windings of the high-frequency switch-mode regulated power transformer windings to form a magnetic flux. Most of them pass through the magnetic core with high magnetic permeability, but there is still a small part of the winding clearance to radiate out and generate electromagnetic induction noise.
Source of noise from regulated power supplies
The main noise sources of switching power supply are:
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