19-01-2016, 02:46 PM
Abstract
Conventional active clamping circuits for driving the pulse transformer in isolated forward DC-DC converters put considerable voltage stress on the DMOS power devices at high duty ratio. This is not so much an issue for an implementation based on discrete DMOS components, but monolithic integration becomes nearly impossible. This paper presents a new 4-transistor active clamping H-bridge topology that significantly reduces the voltage requirements and allows integration in a junction-isolated smart-power IC technology.
INTRODUCTION
N many applications the electronic circuitry is powered by isolated DC-DC converters for safety reasons or other system requirements. Typical examples are the power supplies in central-office ADSL and VDSLtelecommunication equipment or the power supply units in Power-over-Ethernet devices. Widely used isolated converter topologies are the fly-back, the forward and the combined forward/fly-back architectures [1] [2], where the driving electronics at the primary side of the pulse transformer and the rectifying electronics at the secondary side are employing discrete power transistors and/or diodes. When trying to optimize the power efficiency and reduce the physical size of the system, monolithic integration of the driving and rectifying electronics in an appropriate highvoltage smart-power IC technology seems an attractive approach, but the practical IC design is not straightforward. This paper describes the single-chip implementation of the driving electronics at the primary side of the pulse transformer in the specific case of an isolated forward DCDC converter.