How to solve the ripple harmonics and noise interference generated by switching power supplies
Ripple
Ripple: refers to a clutter signal consisting of periodic and random components attached to the DC level. The peak value of AC voltage in the output voltage under rated output voltage and current. Narrowly defined ripple voltage refers to the power frequency AC component contained in the output DC voltage.
noise
Noise: For the nominal noise in electronic circuits, it can be summarized as a collective term for all signals other than the destination signal. At first, people referred to the electronic signals that caused the noise emitted by sound equipment such as radios as noise. However, the consequences of some non purposeful electronic signals on electronic circuits are not always related to sound, so later people gradually expanded the concept of noise. For example, the electronic signals that cause white spots and stripes on the visual screen are also referred to as noise. It may be said that all signals in a circuit, except for the intended signal, regardless of whether they affect the circuit or not, can be referred to as noise. For example, ripples or self-excited oscillations in the power supply voltage can have adverse effects on the circuit, causing the audio device to emit alternating sound or causing circuit malfunction, but sometimes may not result in the aforementioned consequences. For this type of ripple or oscillation, it should be referred to as a type of noise in the circuit. There is a radio wave signal of a certain frequency, which is a normal target signal for a receiver that needs to receive this signal, while for another receiver it is a non target signal, which is noise. The term interference is often used in electronics and sometimes confused with the concept of noise. In fact, there is a difference. Noise is an electronic signal, while interference refers to a certain effect, which is an adverse reaction caused by noise on a circuit. There is noise in the circuit, but there may not always be interference. In digital circuits. It is often observed with an oscilloscope that there are small spikes mixed with normal pulse signals, which are not expected, but rather a form of noise. However, due to the characteristics of the circuit, these small spikes are not yet likely to cause confusion in the logic of the digital circuit, so it can be considered that there is no interference.
When a noise voltage is large enough to cause interference to the circuit, the noise voltage is called interference voltage. The maximum noise voltage applied to a circuit or device when it can still maintain normal operation is called the anti-interference tolerance or immunity of the circuit or device. Generally speaking, noise is difficult to eliminate, but efforts can be made to reduce the intensity of noise or improve circuit immunity to prevent noise from forming interference.
