ST

The SRK2000 smart driver implements a control scheme specific to secondary-side synchronous rectification in LLC resonant converters that use a transformer with center-tap secondary winding for full-wave rectification.

It provides two high-current gate-drive outputs, each capable of driving one or more N-channel Power MOSFETs. Each gate driver is controlled separately and an interlocking logic circuit prevents the two synchronous rectifier MOSFETs from conducting simultaneously.

The control scheme in this IC allows for each synchronous rectifier to be switched on as the corresponding half-winding starts conducting and switched off as its current goes to zero. A unique feature of this IC is its intelligent automatic sleep-mode. It allows the detection of a low-power operating condition for the converter and puts the IC into a low consumption sleep-mode where gate driving is stopped and quiescent consumption is reduced. In this way, converter efficiency improves at light load, where synchronous rectification is no longer beneficial. The IC automatically exits sleep-mode and restarts switching as it recognizes that the load for the converter has increased.

A noticeable feature is the very low external component count required.

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Circuit Diagram