Safety Energy Saving Long Life Power Adapter

How can I suppress the noise of power adapter?

There is no lack of low-end products in the power adapter, in the work will emit some nuisance sound, some friends should have encountered, because the power adapter itself is a source of electrical noise, qualified power adapter electromagnetic interference and radio frequency interference must be designed in the specified standard range. At the same time, in order to be able to work stably, should have a strong anti-interference performance.

Noise is divided into conducted noise and radiated noise. Conducted noise is transmitted by the wire useless electromagnetic energy, its frequency range is below 30MHz, the frequency range of the signal wavelength is longer, radiation to space is very small; and radiated noise is leaked from the electronic equipment or its connecting wires to the space of the useless electromagnetic energy, its frequency range is more than 30MHz, so how to suppress the noise in the power supply design is very good?

Methods to suppress conducted noise in power adapters include:

1. Connect a common mode and differential mode noise filter in series at the input of the switching power supply to suppress conducted noise. The attenuation factor of the noise filter depends on the size of the switching power supply, the switching frequency, the design scheme, the application method, and the usage environment.

2. Where it is required that no transient currents pass through the case, an insulating spacer with a shield can be installed between the switching tube case and the heat sink, and the shield can be connected to switching circuit ground, so that capacitive currents caused by voltage variations, du/dt, enter the switching circuit instead of the case or safety ground.

3. The high-speed turn-on and turn-off of the switching tube is a source of noise in the switching power supply, for which the switching waveform needs to be shaped and processed, which is the reason why power switching devices need buffer circuits.

Power adapter inevitably generates radiated noise, the effective way to inhibit is shielding, that is, with good conductivity materials for electric field shielding, with high permeability materials for magnetic field shielding. In order to prevent the magnetic field of the pulse transformer leakage, the closed loop can be used to form a magnetic shielding, in addition, the electric field shielding. Shielding should consider the heat dissipation and ventilation problems, shielding shell on the ventilation holes for the best round holes, in order to meet the ventilation conditions, the number of holes can be more, the size of each hole should be as small as possible. The joints should be welded to ensure electromagnetic continuity, and if screws are used for fixing, the spacing between the screws should be short. Filtering measures should be taken at the introduction and exit wires of the shielded enclosure, otherwise, these will become interference transmitting antennas, seriously reducing the shielding effect of the shielded enclosure. If electric field shielding is used, the shielding enclosure must be grounded, otherwise, the shielding effect will not be achieved; if magnetic field shielding is used, the shielding enclosure does not need to be grounded. For non-embedded external switching power supply shell must be electric field shielding, otherwise, it is difficult to pass the radiation interference test.

Eahunt is a national high-tech enterprises, with many years of experience in power adapter R & D and production, mastering the industry-leading power supply R & D and production technology, joint U.S. MPS was the first to apply synchronous rectification technology, line loss compensation technology, joint Weltrend charging giant to jointly develop the intelligent recognition of the charging technology, the success of the import of a number of cases, safety, energy saving, long life, select the Choose Eahunt.