Low frequency switch power supply ripple suppression method

Switching power supply output ripple comes mainly from five aspects: input ripple at low frequency, high frequency ripple, ripple common-mode noise caused by parasitic parameters, high-frequency resonance occurring in the process of power switch device and closed loop regulation caused ripple noise. Low frequency ripple is related to the output filter capacitance of the circuit. Capacitance capacity could not have unlimited increase, leading to a low ripple output of residue. After ac ripple attenuation by the DC/DC converter, the switching power supply output performance for low frequency noise, its size by DC/DC converter is decided by the variable ratio and the gain of the control system. Current mode control of DC/DC converter ripple suppression than a slightly better rate of voltage type. But its outputs low frequency ac ripple is still larger. If you want to achieve a low ripple output switching power supply, it must be the low frequency power supply ripple filter measures. Can adopt advance level before the voltage regulator and closed loop gain to eliminate the DC/DC converter. Low frequency ripple suppression method: first, using the method of feedforward control, low frequency ripple component. Second, increase the output of low-frequency filtering inductance, capacitance parameter, make low frequency ripple is reduced to the required index.