Infineon Technologies Austria Ag

Roberto Quaglino

Giuseppe Bernacchia

Peter Green

Cesar Augusto Braz

Hongying Ding

Techniques are provided for avoiding an avalanche breakdown voltage across a synchronous rectification (SR) switch on the secondary side of an isolated switched-mode power converter operating in a low-power mode, e.g., a burst mode, during which a load of the power converter draws negligible current. This is accomplished via use of a two-level switch driver for controlling a power switch on the primary side of the power converter. The two-level switch driver is configured to source low current levels to a control terminal (e.g., gate) of the power switch during burst-mode operation. This low current reduces the slope of the rising edge of voltage pulses on the primary and secondary sides of the power converter which, in turn, limits the peak of the voltage ringing across the SR switch. By limiting the voltage in this manner, the SR switch avoids entering avalanche breakdown.

Two-level switch driver for preventing avalanche breakdown for a synchronous rectification switch in a power converter operating in a low-power burst mode

A power converter with an isolated topology may include a primary side and a secondary side. The secondary side includes a self-powered synchronous rectifier. The synchronous rectifier includes a synchronous rectifier transistor having at least a drain and a gate, a voltage regulator having at least an input that is coupled to the drain of the synchronous rectifier transistor, and an auxiliary transistor having at least a drain that is coupled to the drain of the synchronous rectifier transistor. The auxiliary transistor is on a same die as the synchronous rectifier transistor. The synchronous rectifier also includes a clamping device having at least an output that is coupled to the gate of the auxiliary transistor, and a gate driver circuit having at least: a power supply input that is coupled to the output of the voltage regulator, and an output that is coupled to a gate of the synchronous rectifier transistor.

Self supply for synchronous rectifiers using off state reverse voltage

In one example, a circuit for controlling synchronous rectification includes a first current compensation module, a second current compensation module, and a control module. The first current compensation module is configured to provide a first current into parasitic capacitance at a drain pin when a drain of a synchronous rectifier draws current from the parasitic capacitance. The drain pin is coupled to the drain of the synchronous rectifier via a resistor. The first current compensation module is further configured to generate a triggering signal using the first current. The second current compensation module is configured to draw a second current from the parasitic capacitance when the drain of the synchronous rectifier provides current into the parasitic capacitance and generate an arming signal using the second current. The control module is configured to activate the synchronous rectifier using the triggering signal and the arming signal.

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Villach, Austria

Roberto Quaglino