1, spurious arguments.
Because the work at a high frequency, low frequency component characteristics LED dimming power supply would change occurs, whereby noise occurs. At high frequencies, the stray coupling parameters of great influence on the properties of the channel, and the channel becomes spread capacitance EMI.
2, the switching circuit.
The switch circuit is mainly composed of switches and high-frequency transformer. Exists between the switch and the heat sink and enclosure and power supply leads inside the spread capacitance, du it happens / dt has a greater level of pulse, wide-band and rich harmonics. Load switch high-frequency transformer primary coil, rational load. When originally turned the switch off, the high-frequency transformer leakage inductance happened back EMF E = -Ldi / dt, which is proportional to the current value of the rate of change of the collector, and is proportional to the leakage inductance, superimposed on off on-off voltage, constituting the turn-off voltage spikes and constitute conducted interference.
3, rectifier diode rectifier circuit.
There is a reverse current when the output rectifier diode is cut off, the recovery time to zero junction capacitance and other factors related. It will happen under the influence of the transformer leakage inductance and other parameters distribute large current change di / dt, the occurrence of a strong high-frequency interference, frequency of up to tens of megahertz.