Switching Power Supply: A Solution to Reduce Ripple and Noise Voltage
Reduce EMI interference
Using a metal shell as a shield to reduce external electromagnetic field radiation interference. To reduce electromagnetic interference from the power line input, an EMI filter is added at the power input end.
Using capacitors with good high-frequency performance and low ESR at the output end
Aluminum or tantalum electrolytic capacitors using polymer solid electrolytes as output capacitors are the best, characterized by small size and large electrical capacity, low ESR impedance at high frequencies, and allowable ripple current. It is most suitable for high-efficiency, low voltage, high current step-down DC/DC converters and DC/DC module power supplies as output capacitors.
Adopting frequency synchronization with the product system
To reduce output noise, the switching frequency of the power supply should be synchronized with the frequency in the system, that is, the switching power supply should use external synchronization to input the frequency of the system, so that the switching frequency is the same as the system frequency.
Avoiding mutual interference between multiple module power supplies
Multiple module power supplies may work together on the same PCB. If the module power supply is unshielded and close together, it may interfere with each other and increase the output noise voltage. To avoid such mutual interference, shielding measures can be taken or they can be appropriately kept away to reduce the interference caused by their mutual influence.
Add LC filter
To reduce the ripple and noise of the module power supply, LC filters can be added to the input and output terminals of the DC/DC module.
Increase LDO
Adding a low voltage differential linear regulator (LDO) after the output of a switching power supply or module power supply can significantly reduce output noise to meet the needs of circuits with special noise requirements, and the output noise can reach μ Class V.
Due to the voltage difference (difference between input and output voltage) of LDO being only a few hundred mV, the standard voltage can be output when the output of the switching power supply is slightly higher than that of LDO by a few hundred mV, and its loss is not significant.
Add active EMI filters and active output ripple attenuators
Active EMI filters can attenuate common mode and differential mode noise between 150kHz and 30MHz, and are particularly effective in attenuating low-frequency noise. At 250kHz, it can attenuate 60dB common mode noise and 80dB differential mode noise, and the efficiency can reach 99% at full load.
The output ripple attenuator can reduce power output ripple and noise by more than 30dB in the range of 1-500kHz, and can improve dynamic response and reduce output capacitance.
