STMicroelectronics Inc. (ST, Geneva, Switzerland) presented its new STSR3 MOSFET driver that provides the high current output necessary to allow the MOSFETs to be used as synchronous rectifiers in flyback converters, high-power adaptors and low output-voltage dc/dc flyback modules. Operating at a frequency range of 30kHz to 750kHz, the IC runs from a 4V to 5.5V supply and offers a typical peak output current of 2A (source) and 3.5A (sink).
The part uses a synchronizing clock input from the secondary side of the isolation transformer to generate a driving signal with set dead times with respect to the primary-side pulse-width modulation (PWM) signal. This prevents secondary side shoot-through conditions when the primary turns on. The control is provided by a fast, cycle-by-cycle, logic control mechanism, based on a high-frequency oscillator synchronized to the clock signal.
A special inhibit function allows the drive output to be shut off by sensing the synchronous rectifier source/drain voltage and turning it off when necessary. The STSR3 allows the implementation of synchronous rectification in discontinuous-mode PWM, continuous-mode PWM and quasi-resonant flyback converters.
