Analysis of the Parameters of the Power Circuit of a Pulse Step-Down Voltage Converter for Digital VLSI Power Supply

The development of a pulse step-down voltage converter begins with the calculation of the parameters of the inductor and the output capacitor. The value of the inductance of the inductor and the capacitance of the output capacitor depend on many characteristics of the converter, such as the power of the converter, the values of the input and output voltage, the permissible level of output voltage ripple, the permissible relative pulse of the output current, and the modulation frequency. As a rule, the characteristics of the converted voltage and the power of the converter are set by the technical specification and cannot be independently selected by the developer. The modulation frequency is not one of the parameters characterizing the output power of the converter and can be selected by the developer at his discretion. The values of the inductance of the inductor and the capacitance of the output capacitor have a significant dependence on the selected modulation frequency. The higher the modulation frequency, the lower the inductance and capacitance of the output capacitor of the converter. This minimizes the overall physical dimensions of the pulse converter. However, as the modulation frequency increases, energy losses on the power key increase and the effect of electromagnetic interference increases. Choosing the modulation frequency of a pulse voltage converter is always a search for a compromise between minimizing the size of the inductor with the output capacitor and reducing the efficiency of the converter, along with reducing the noise immunity of the powered device. This article provides an example of the analysis of the main parameters of the converter's power circuit in a wide range of modulation frequencies. These calculations help the developer to find the optimal ratio of the modulation frequency with the values of the inductor and the output capacitor, if different modulation frequencies are allowed in accordance with the technical specification. An example of calculating the dependence of the parameters of a pulse converter on the output voltage and output power at a fixed modulation frequency is also presented.

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