Undesirable Sub-harmonic Currents in the Coil of Buck Converter Prototype - Project Bumblebee

J. Kaczmarek, R. Suszyński (Koszalin Univ. of Techn., Poland)

Control circuits for DC/DC converters are usually implemented as analog or digital transfer function (PID, type III etc). These solutions are usually effective in the close vicinity of projected bias point, and its change causes worsening of stabilized output voltage properties. It's necessary to consider not only work mode (CCM, DCM), but also changes of bias point of the device. Main factors that influence bias point are: changes in loads resistance and changes in input voltage value. The solution to those problems could be using concept of controlling DC/DC converters using law of conservation of energy (project Bumblebee). During the work on the project Bumblebee characteristic oscillations in the steady state were observed. Similar oscillations occur in the current method (Current Mode) if you do not use slope compensation coil current. The article shows the reason for this undesirable phenomenon and how to eliminate it.