Digital power chipset optimises dead time automatically

May 22, 2015 // By Graham Prophet
Texas Instruments has introduced a power management chipset that includes intelligent digital control and a body-diode sensing feature to optimise secondary-side synchronous rectification in next-generation AC/DC and isolated DC/DC power supplies.

The UCD3138A digital controller and UCD7138 low-side gate driver improve system efficiency and claim to cut synchronous rectification MOSFET voltage stress in half compared to other digital-power solutions.

Accurate control of dead time in the synchronous rectifiers helps minimise power losses and reduces the risk of MOSFET failure. The UCD3138A and UCD7138 chipset use body-diode voltage information in fast digital control algorithms to dynamically optimise dead-time and compensate for power-stage component variations without calibration or screening during mass production. This helps designers to reach the 80 PLUS Titanium-grade for power supplies, which saves energy costs to information technology service providers that employ large server arrays.

The UCD3138A and UCD7138 pairing features:

- Intelligent diode voltage sensing to optimise dead time: Adjusting timing for minimal diode conduction increases efficiency and reliability, while eliminating the signal-to-noise ratio challenges of traditional MOSFET VDS ON sensing devices.

- High peak current supporting wide load range: The UCD7138’s asymmetrical, rail-to-rail 4-A source and 6-A sink peak-current drive supports load range of a few-hundred Watts to a kilowatt where multiple paralleled FETs are used.

- Compact solution to enable fast, efficient switching: A 3-mm by 3-mm QFN package reduces board space as well as parasitic inductances when placed alongside the synchronous rectifier MOSFETs.

- Efficient operation at frequencies up to 2 MHz: The hardware peripherals in the UCD3138A along with 14-nsec propagation delays and fast rise/fall times with minimised tolerances in UCD7138 enable extremely high frequencies.