A Bipolar Smart Power Synchronous Rectifier

As microelectronic systems voltages continue to drop towards 1V and below, the design and realisation of low cost high efficiency DC-to-DC power converters become increasingly problematic due to the small but finite forward voltage drop typically 0.4 - 0.5 V and consequent power loss incurred across the switching device typically a Schottky diode contained within the low-voltage output stage of the converter circuitry. Traditionally, in medium to low-voltage applications, replacement of the Schottky diode with a MOSFET based synchronous rectifier SR has proved an effective solution to the aforementioned problem. However, use of a synchronous rectifier requires additional control circuitry, which gives rise to an increase in both circuit complexity and cost. In this paper a novel bipolar based synchronous rectifier BiSync device design that overcomes many of the aforementioned difficulties is proposed. Fundamental modes of operation were verified using Silvaco TCAD simulations to demonstrate proof of concept. Results presented indicate that the final design can provide a substantially more compact and electrically efficient solution than a MOSFET based synchronous rectifier of equivalent area, while also being capable of manufacture using an industry standard bipolar transistor technology and suitable for use in medium-to-very-low voltage conversion applications.