How to avoid interference with switching regulated power supplies
Switching regulated power supply (stabilized voltage supply) is able to provide stable AC or DC power for the load of electronic devices, including AC regulated power supply and DC regulated power supply two categories. When the grid voltage or load instantaneous fluctuations, stabilized voltage supply will be 10-30ms response speed to compensate for the voltage amplitude, so that it is stabilized within ± 2%.
Switching regulated power supply is a relatively new type of power supply. It has the advantages of high efficiency, light weight, step-up and step-down voltage, and large output power. But because the circuit works in the switching state, it is relatively noisy. With the figure below, let's briefly talk about the working principle of a buck switching power supply. As shown in the figure, the circuit consists of a switch K (the actual circuit for the triode or field effect tube), the continuity diode D, the energy storage inductance L, filter capacitor C and so on. When the switch is closed, the power supply through the switch K, inductor L to the load power supply, and part of the electrical energy will be stored in the inductor L and capacitor C.
Switching regulated power supply operation switching transistor and current diode (can also be another switching transistor) is always alternately on or off, KQ and KD is not an ideal device, the two state transitions require a certain amount of time, which produces a spike interference. In the process of state transition, the on switch is not fully on, and the cut-off switch is not cut-off moment, there is a direct path from the power supply to ground, resulting in a transient current Is. The current is related to the switching transistor conduction current Imax and the cut-off current Icmin the difference between the switching transistor current Imax and cut-off current Icmin, switching KQ and KD at the same time conduction time, such as the duration. Due to the influence of the circuit distribution parameters, ringing oscillations appear in the waveform.
The switching regulator power supply works by radiating interference into space. The radiation noise level is inversely proportional to the distance from the radiation source. General away from 5cm away from the wiring can be. If the structure does not allow it, it should be shielded. Power input line around the strong electromagnetic field, in order to reduce the electromagnetic coupling between the input line and the output line, the two must be far away.
