What is the DC power shielding mechanism?
DC power transformer shielding principle Among them, C5 is the primary and secondary side capacitor of the transformer, which transmits the interference noise measured by the primary to the secondary. In theory, adding a Y capacitor (C4) is easiest and adds no additional losses. However, for safety reasons, the leakage current is not very large, so other methods have been proposed.
DC transformer shielding principle This connection method divides C1 into two parts, the primary side corresponds to the DC power shield, the secondary side is shielded, and both sides must be grounded, yes, it is divided into two capacitors and grounded in the middle. So that the primary noise of the DC power supply is bypassed, adding a metal plate on the primary secondary side divides the primary secondary capacitor into two parts. The principle of DC transformer shielding is that the primary noise can be grounded by the metal plate.
The principle of DC power transformer shielding DC high frequency transformer internal shielding internal shielding and external shielding: add winding or copper foil between the primary side and the secondary side, and connect one end to the working ground of the primary side. The main purpose is to return the common mode interference signal on the primary side to the interference source through the shielding layer. Without this shield, common mode interference signals are transmitted to the secondary side through the interlayer capacitance between them, and the primary and secondary windings will eventually cause output EMI problems.
External shielding of DC high frequency transformer: A layer of copper foil is tightly adhered to the magnetic core and external winding of the transformer. The copper foil layer must be closed in order to form the induction loop. The magnetic field in the leakage inductance core of the transformer is not closed, but leaks to the outside. In high frequency applications, strong leakage magnetic fields can induce voltage in the closed loop of the input and output ports, resulting in insufficient voltage, EMI test results, if there is an external shielding layer, according to the principle of electromagnetic induction, the shielding is induced in this layer current to form an opposite magnetic field, thereby canceling the effect of the transformer leakage magnetic field.
