In order to prevent converter operational issues related to the minimum on-time of the controller, specifically during high frequency operation, a pulse skipping mode has been implemented for the TPS7H500x-SEP controllers. During this mode, the primary outputs (OUTA/OUTB) will stop switching periodically. For the controllers with SR outputs, SRA/SRB remain on during pulse skipping if the soft-start period has ended. If the device enters into pulse skipping during the soft-start sequence, SRA/SRB remain off since the outputs are not yet active. Having a minimum on-time that is too long in duration during high frequency operation can lead to an issue such as inductor current runaway during the soft-start period. Pulse skipping allows for overcoming this issue by reducing the peak inductor current during the start-up period. In high frequency converter designs where the VIN to VOUT ratio of the converter may lead to required duty cycles that are less than the minimum on-time, the controller outputs will skip pulses in order to maintain the required output voltage. Pulse skipping will occur when both of the following conditions are present:
When the duty cycle limit of a compatible controller is set to 50% and both OUTA and OUTB are active, the number of pulses skipped by each of the primary outputs will be equal. This will ensure the volt-second balance is maintained across the transformer and that flux-walking that leads to transformer saturation is avoided in isolated topologies such as the push-pull.