Chipset Controls Dead Time to Reduce MOSFET Failure Risk

Accurately controlling dead time in synchronous rectifiers helps minimize power loss and risk of MOSFET failure. With that in mind, Texas Instruments incorporated intelligent digital control and a body-diode sensing feature into its latest chipset to optimize secondary-side synchronous rectification in ac-dc and isolated dc-dc power supplies. The chipset comprises the UCD3138A digital controller and UCD7138 low-side gate driver.

The controller/driver combo uses body-diode voltage information with digital control algorithms to optimize dead time and compensate for power-stage component variations without calibration or screening during mass production. Intelligent sensing adjusts timing for minimal diode conduction to boost efficiency and reliability while eliminating the traditional signal-to-noise ratio channels of MOSFET V_{DS_ON} sensing devices.

The gate driver features an asymmetrical, rail-to-rail, 4-A source and 6-A sink peak-current drive to support load range of a few hundred watts to a kilowatt (for multiple paralleled FETs). Operation maintains high efficiency at frequencies up to 2 MHz, thanks to the controller’s hardware peripherals in addition to 14-ns propagation delays and fast rise/fall teams. A 3- by 3-mm QFN package helps conserve board space.