Monolithic integration of an active asynchronous voltage clamp with a 12V/3A full bridge synchronous rectifier

In transformer isolated converters, a large voltage overshoot is present on the secondary side switching nodes at every switch transition. As is well known in the design of monolithically integrated high voltage circuits, the peak voltage stress in a circuit is the paramount parameter for an efficient implementation of smart-power circuits. A voltage clamping circuit that minimizes the voltage stress in the circuit is crucial for an efficient monolithic implementation of a synchronous rectifier in a smart-power technology. This paper presents a smart-power implementation of an asynchronous active clamping circuit on the same IC as a 12V/3A synchronous rectifier for a full bridge phase shifted dc-dc converter. The asynchronous clamping circuit minimizes the number and size of required external components to provide the voltage clamping, and optimizes the efficiency of the synchronous rectifier by accurately controlling the clamping operation.