This slide provides a more detailed look at the anti-capacitive protection function. With the L6599A IC, there were a number of extra components required to do the average current sensing. Fewer components are required when using the L6699 IC, making it easy to implement the new design by merely removing some components and changing the values of a few others. With this change, the IC senses the instantaneous current and makes sure that it is lagging behind the applied voltage. That means that there is a positive phase shift in the resonant tank circuit’s current. The IC increases the switching frequency if the positive phase shift gets too close to zero. If the phase shift suddenly becomes negative, the IC stops switching for 50 µs, then does a soft-restart. During this idle period, the PFC control IC is pulled low so that it stops switching while the LLC controller is in the pause mode.