Ripple is due to DC stabilized power supply It is a phenomenon caused by the voltage fluctuation of the DC stabilized power supply. Because the DC stabilized power supply is generally formed by the AC power supply through rectification and voltage stabilization and other links, it is inevitable that there are some AC components in the DC stabilized quantity. This AC component superimposed on the DC stabilized quantity is called ripple. Ripple components are more complex, and its form is generally a sine wave like harmonic wave with a frequency higher than the power frequency, and the other is a pulse wave with a very narrow width. Ripple is the AC component of a DC voltage. DC voltage is supposed to be a fixed value, but most of the time it is obtained through AC voltage rectification and filtering. Because the filtering is not clean, there will be residual AC components. Even so, even if the battery is used for power supply, ripples will occur due to load fluctuations. In fact, the output voltage of even the best voltage reference device is wavy.
Ripple voltage will affect the operation of the system Noise 。 Therefore, the power supply should have enough filtering measures to limit the ripple within a certain range. Harm of ripple: 1) It is easy to generate harmonics on electrical appliances, and harmonics will cause more harm;
2) Reduce the efficiency of power supply;
3) Strong ripple will cause surge The generation of voltage or current causes the burning of electrical appliances; 4) It will interfere with the logic relationship of the digital circuit and affect its normal operation;
5) It will cause noise interference and make image equipment and audio equipment unable to work normally.
In short, they are harmful where we don't need them, and we need to avoid them. There are many ways to suppress and remove harmonics and ripples, but it seems difficult to completely eliminate them. We only have to control them within an allowable range and achieve our goal if they do not affect the environment and equipment.
Common methods to resist ripple voltage are as follows:
1) Full wave or three-phase full wave rectification circuit shall be adopted as far as possible if the cost and volume allow;
2) Increase the capacitance in the filter circuit, and use LC filter circuit with better effect if conditions permit;
3) The voltage stabilizing circuit with good effect is used, and analog voltage stabilizing power supply is used instead of switching power supply in places with high requirements for ripple suppression;
4) Reasonable wiring.
With the bandwidth of 20M oscilloscope as the limiting standard, the voltage is set to PK-PK (there is also one that measures the effective value), the clamp and ground wire on the oscilloscope control head are removed (because the clamp and ground wire will form a loop, like an antenna receiving noise, introducing some unnecessary noise), and the ground ring is used (it is OK not to use the ground ring, but the error generated should be considered), Connect a 10UF electrolytic capacitor and a 0.1UF ceramic chip capacitor in parallel on the probe, and test directly with the probe of the oscilloscope; If the oscilloscope probe does not directly contact the output point, it should be measured with twisted pair or 50 Ω coaxial cable. [1]
