Reasonable use of current switching power supply EMI suppression measures
Switching power supply, we are familiar with, in every family is almost used, because it is people's current can be used reasonably, from Edison invented the light bulb, people have a further understanding of the switching power supply. Here I will introduce the measures for EMI suppression of switching power supplies.
In order to prevent the magnetic leakage of the high-frequency transformer from interfering with the surrounding circuit, the magnetic leakage field of the high-frequency transformer can be shielded by a shielding belt. The shielding belt is generally made of copper foil, wrapped around the outside of the transformer, and is grounded. The shielding belt is a short circuit ring relative to the leakage magnetic field, so as to inhibit the leakage of the leakage magnetic field.
Separately speaking, switching power supply EMI suppression has several major measures:
(1) Reasonable PCB design
(2) The reasonable application of varistor to reduce surge voltage
(3) Reduce dv/dt and di/dt (reduce their peaks and slow down their slopes)
(4) Damping network inhibits overshoot
(5) Use a reasonably designed power line filter
(6) Diode with soft recovery characteristics to reduce high band EMI
(7) Active power factor correction, and other harmonic correction techniques
(8) Effective shielding measures
(9) Reasonable grounding treatment
In high-frequency transformers, relative displacement occurs between magnetic cores and windings, resulting in noise (whistling, vibration) in the operation of high-frequency transformers. In order to prevent this noise, it is necessary to take reinforcement measures for the transformer:
(1) The three contact surfaces of the magnetic core (such as EE and EI magnetic core) are bonded with epoxy resin to inhibit the generation of relative displacement;
(2) Use "glass bead" adhesive to bond the magnetic core, the effect is better.
