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No Wires Adapter Usually In Its

No Wires Adapter Usually in its

Generation and Control of No - wire Adapter Noise

        In the no-wire adapter, electromagnetic components can be issued with inductors, transformers and power devices, usually around the use of conductive metal material as a shield, so that the electromagnetic wave attenuation. Against the weak electromagnetic components, necessary The effective way to suppress the electromagnetic interference of the power adapter is to shield, that is, the use of conductive metal materials to shield the electric field, with a high magnetic permeability of the magnetic field to shield the use of electromagnetic shielding of the electromagnetic shielding Method to solve the problem of EMI is not the effect of the normal work of the circuit shielding technology can be divided into the electromagnetic wave parts of the shielding and susceptible to electromagnetic waves affected by the shielding of components.

No wire adapter circuit board in the work will radiate noise, often the signal line through the ground to the chassis, causing resonance, from the chassis to radiate strong radiation noise, then should be done using multi-layer printed circuit board , The middle layer for the power line or ground, the power cord sealed in the board, which can effectively prevent the circuit radiation and receive noise. One printed circuit board "full ground." Draw high-frequency circuit, in addition to bold Line, the board should not be occupied by all the area as a ground wire, which can effectively reduce the parasitic inductance, reduce noise emissions.

Principle and Application of Synchronous Rectification of Switching Power Supply / Power Adapter

From the synchronous rectification schematic, it can be seen that the driving voltage of the rectifier tube VT3 and the free flow tube VT2 is taken out from the secondary winding of the transformer and added between the gate G and the drain D of the MOS tube. If the MOS tube This application can not be fully opened, loss is great, but used in synchronous rectification is a feasible simplification program. As the two tube switch state of mutual trivial, a tube open, another tube off, so we only briefly analyze the opening of the inductor current continuous, we know that MOS tube has a parasitic diode in vivo parasitic, so that the inductor current continuous application , The MOS transistor in parallel before the actual opening of the diode has been opened, the source S and drain D relative to the level of the grid is consistent, plus the voltage between the GD is equivalent to the voltage applied between the GS, so that the transformer secondary winding When the rectification tube is positive, the rectifier tube VT3 gate leakage voltage is positive, rectifier tube zero pressure open, when the transformer secondary winding is negative, the continued flow tube VT2 open, filter inductance freewheeling. The gate voltage must be synchronized with the phase of the rectified voltage to complete the rectification function, so called synchronous rectification.

Introduction:

Synchronous rectification is a new technology that uses a dedicated power MOSFET with a very low on-state resistance to replace rectifier diodes to reduce rectification losses. It can greatly improve the efficiency of the DC / DC converter and there is no deadband voltage caused by the Schottky barrier voltage.

Synchronous rectification of the basic circuit structure:

The power MOSFET is a voltage-controlled device that has a linear relationship between the volt-ampere characteristics at turn-on. When the power MOSFET is used as a rectifier, the gate voltage must be synchronized with the phase of the rectified voltage to complete the rectification function, so it is called synchronous rectification.


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