Ensuring the Clock Stability of Power Converters

The article presents the main advantages of using synchronous PWM with subordinate peak current control in DC voltage converters. The DC/DC converter operation in the modes of intermittent and continuous currents with varying duty factors is analyzed. Factors causing the occurrence of subharmonic oscillations during the converter operation in the continuous current mode with a duty factor higher than 0.5 are considered. Analytical relationships describing the necessary and sufficient conditions for stable operation of the converter in a continuous current mode are given. Methods for excluding subharmonic oscillations through the introduction of a corrective sawtooth voltage in the feedback loop are proposed. A computer simulation model of the converter both with and without the introduced correcting circuit is presented along with the diagrams demonstrating the effectiveness of the proposed approach for ensuring clock stability. Circuit design solutions are proposed that make it possible to produce a sawtooth corrective voltage without using a sawtooth voltage generator integrated into the PWM controller. Instead, the same can be obtained by connecting to the PWM controller output. Analytical relationships are presented using which it is possible to determine both the sawtooth corrective voltage value and the stability boundaries.