The UCC25661x-Q1 family implements a high-speed low latency slew-rate detection block to optimize the dead time between high-side and low-side pulses. The adaptive dead-time block adjusts the dead time to prevent shoot-through or excessive body-diode conduction.

At the core of the adaptive dead time block is the slew rate detector block, capable of detecting slew rates up to 200V/ns; UCC25661x-Q1 family is an excellent choice for use in high frequency resonant converters.

In burst mode, during a ZCS prevention operation or in power stages where the slew rate can be very slow, use the resonant tank current polarity signal (Ipolarity comparator output) to augment the slew-rate detector.

Because of the natural symmetric operation of LLC, only the dead time between high-side switch turn off and low-side switch turn on are determined by the slew rate detector. Dead time is copied and then applied to the dead time between low-side MOSFET turn off and high-side MOSFET turn on. There are a few exceptions where the dead time is not copied. The conditions are listed below.

• Missing slew rate detector signal in the previous high to low transition
• ZCS detection in the previous cycle

Under the above-mentioned conditions, use the Ipolarity comparator based on the ISNS signal to adjust the dead time during low to high transitions.