I'm working on the design of a 24V to 30V boost converter that needs to have an output ripple of less than 100 mV with an output current between 0 and 2 A.
The output is used to power a controller for a voice coil actuator. Unfortunately the controller only has a single power input and cannot be changed or modified. This means that the actuator drive current and analog sensor electronics are powered from the same supply. The boost converter needs to have a low output ripple to ensure the position sensors have low noise, and support a large variation in output current depending if the actuator is accelerating (2 A max.) or when it's just holding position (10-20 of mA).
I have preliminary selected the TPS55340 boost converter with integrated switch to use in my design. Using TI's WEBENCH and back-of-the-envelope calculations I selected a L = 12 uH inductor and using a switching frequency of 750 kHz. Pulse-skipping starts below 17 mA. It should be possible to avoid pulse-skipping by adding a minimal load.
The problem I see is that the DCM-CCM boundary occurs at Iout_crit = 224 mA. So I think I need to optimise the design such that it operates well in both DCM and CCM. I am unsure how to approach such design.
- In general, how bad is it to have a change-over from CCM to DCM? In previous designs I was always able to ensure the controller was operating in CCM.
- If the CCM to DCM mode switching should be prevented; how could I change the design such that it always operates in either CCM or DCM over the full 0 - 2 A operating range?
- How to determine the component values for the compensation network?
- If someone could point me to a relevant application note or other source of information, that would be helpful.
Thanks
