Patent attributes
A start-up routine for a Switched-Mode Power Supply (SMPS) gradually increases the duty cycle while reducing an initial dead time to a final optimal dead time for normal operation. Reliability is improved by the larger initial dead time that reduces ringing in switching transistors during low-voltage conditions early in the start-up sequence. Efficiency is improved by reducing the optimal dead time as voltages approach operating levels. The initial dead time is pre-calculated as a function of the input voltage and initial duty cycle. Optimal dead times are pre-calculated as a function of output voltage and output current. The optimal dead time is adjusted for each iteration of a second loop that also increases duty cycle until the target operating output voltage is reached. Pre-calculated dead times are based on the time required to fully charge and discharge parasitic drain-to-source capacitances in the switching transistors in the SMPS circuit.
