The changes of electric field and magnetic field will be generated alternately. The electromagnetic radiation emission of switching power supply for tube amp is generated by the way of spreading kinetic energy in space at the speed of light. Among the main parameters affecting radiation, they cannot be changed arbitrarily. Therefore, the only thing that can effectively suppress radiation and sometimes be freely grasped by designers is to reduce the main parameter of the loop occupying the ground. Reducing the floor area occupied by the loop as much as possible is an important way to reduce the radiated noise. Here, in the layout and wiring of the printed circuit board requiring the power transformer, the layout of electronic devices should be inseparable from each other, and the current line and its return line in the wiring should be close to each other. In the primary circuit, the required input capacitor, triode and transformer need to be close to this. In the secondary circuit, the demand diode is close to the transformer and output inductance.
In the layout of packaging printing board, a simple way to reduce the floor occupied by the circuit is to lay a wire next to the current carrying transmission line, which should be as close as possible to the current carrying transmission line. Smaller loops occupy the ground, which is beneficial to reduce differential mode radiation and sensitivity to external dry deflection.
If it is a two-layer circuit board, lay a wire around the current carrying transmission line on the other side of the circuit board, close to the lower part of the current carrying transmission line, and the wire shall be wider as possible. The originally generated circuit occupies the ground, which is equivalent to the thickness of the circuit board multiplied by the size of the current carrying transmission line. The external electromagnetic fields caused by the positive and negative current charged conductors close to the parallel plane tend to cancel each other.
Another effective layout scheme is to arrange the positive and negative current conductors on the same surface and close to each other, while the front of the packaging printing board is only used as the "ground" (or another uniform motion potential surface), so that the mirror image current induced by the "ground" plate tends to offset the relative electromagnetic field.
A better method is to select multi-layer printed circuit board. At this time, the grounding layer is arranged above the power supply layer at the same time, because the stage where the interlayer spacing is closest to the standard has the most appropriate effect on the suppression of radiation. Of course, this also comes at the cost of cost.
