A Consideration for the Regulation Characteristics of the Digitally Controlled DC-DC Converter

The digital control circuits are often employed in the dc-dc converter in order to realize the high reliability of the electronic power supply, since they are less affected by the influence of environmental disturbances such as electric noise, temperature, aging, etc. as compared with analog ones. In the digitally controlled dc-dcconverter, the regulation of the output voltage is divided broadly into three modes, i.e., the integral control mode, the proportional control one and the open loop one in which the regulation cannot be performed. Especially, in the integral control mode, the regulation characteristics is so ideal that there exists no steady-state output voltage error for changes of the input voltage and the load. For this reason, the digitally controlled dc-dc converter is usually used in the integral control mode. This paper deals with the steady-state analysis of the digitally controlled dc-dc converter in the integral control mode. As a result, it is revealed that the circumscription of the regulation range is due to not only the overflow or underflow phenomenon in the integral mode control circuit but also the maximum or minimum on-time of the trasistor switch. Also, the resolution of the output voltage is analyzed, and the relations among output voltage resolution, number of pulse from the voltage-controlled oscipator (VCO) and regulation range are clarified. These analytical results are verified by the experiments