As you know that many clients and enginners all concerned about the DC to DC converter ripple, which could effectively working device directly, then Why are there ripples in DC to DC converters becomes a questions. we have made a reach finding that In dc-dc converters many factors come into play when we consider about ripples.
Typitally there are three basics:
1. The duty ratio of switch.
2. The inductance value
3. The mode of operation
Depending on the value of energy storage elements and load current, ripples at switching frequency exist in DC-DC Converter. Lower the value of energy storage elements and higher value of load current results into high ripples in DC-DC Converter is necessary.
How to reduce the ripple in DC to DC converters?
CHONDA engineer give the three idea to make the ripple down for our clients, hope the below tips is helpful for all the clients and reader.
1# connect LDO filter after switching power supply output
This is of the most effective way to reduce ripple and noise, keep the same output voltage and don't change the existing feedback system , but it is also the most expensive and highest -power exhaust method. Any LDO has an indicator : noise rejection. -dB frequency curve.To reduce the ripple .
Switching Power Supply PCB layout is critical, it is a very hertz hand problems. A dedicated switching mode power supply PCB engineers work for high-frequency noise due to the high frequency amplitude is large, although there are some stage filtering effect ,finally the effect is not obvious. There are specialized research in this area , the simple approach is on the diode and capacitor C or RC, or series inductance.
2# the diode parallel connection capacitor C or RC
When high-speed diode turned off ,considering the parasitic parameters . During the diode reverse recovery , equivalent inductance and equivalent capacitance becomes a RC oscillator which generates a high-frequency oscillation. To suppress this high frequency oscillation , need parallel connection capacitance C or RC across the diode shunt . Resistance generally 10Ω-100 Ω, capacitance take 4.7pF-2.2nF. It is necessary to test for many times regarding the value of parallel connection capacitance C or RC, If the value works well would be fine for the power supplies , if not,it will cause more serious oscillation.
Demanding high-frequency noise , you can use soft-switching technology . About soft-switching , there are many books devoted .
3# diode connected inductance (EMI filter )
It is also commonly used in high-frequency noise suppression method . For noise frequency , select the appropriate inductance element ,can effectively suppress noise as well. Note that the current rating of the inductor must meet the actual requirements .
The above is about switching power supply ripple , if they can add some waveform and adopt my content would be better. Although it may not quite full , but for general application is enough. About noise suppression , are not necessarily all practical applications , it is important according to their design requirements, such as product size, cost , development cycle , select the appropriate method .