Disclosed examples include flyback converters, control circuits and methods to facilitate secondary side regulation of the output voltage. A primary side control circuit operates a primary side switch to independently initiate power transfer cycles to deliver power to a transformer secondary winding in a first mode. A secondary side control circuit operates a synchronous rectifier or secondary side switch to generate a predetermined cycle start request signal via a transformer auxiliary winding to assume secondary side regulation and to cause the primary side controller to initiate new power transfer cycles.

Flyback converter with secondary side regulation

A synchronous rectifier driver pre-positions a gate of a synchronous rectifier to allow for fast turn-off. The synchronous rectifier driver turns ON the synchronous rectifier by driving the gate at a high level for a period of time that is based on a previous conduction time of the synchronous rectifier. The synchronous rectifier driver thereafter drives the gate at a lower level that is sufficient to keep the synchronous rectifier ON. The synchronous rectifier can be quickly turned OFF by further reducing the level of the drive signal at the gate of the synchronous rectifier.

Gate pre-positioning for fast turn-off of synchronous rectifier

Disclosed examples include isolated phase shifted dual active bridge DC to DC converters with a first bridge circuit operative according to a primary side clock signal to provide a primary voltage signal to a transformer primary winding, a second bridge circuit operative according to a secondary side clock signal to convert a secondary voltage signal from a transformer secondary winding to provide an output voltage signal, and a secondary side control circuit that alternately operates in a first mode to regulate the output voltage signal by controlling a phase shift angle between switching transitions of secondary side switching control signals and switching transitions of the secondary side clock signal, and a second mode to discontinue the secondary side switching control signals and synchronize the secondary side clock signal to transitions in the secondary voltage signal while the secondary side switching control signals are discontinued.

Isolated phase shifted DC to DC converter with frequency synthesizer to reconstruct primary clock

Disclosed examples include isolated dual active bridge (DAB) DC to DC converters with first and second bridge circuits, a transformer with a sense coil, and a secondary side control circuit to provide secondary side switching control signals to regulate an output voltage or current signal by controlling a phase shift angle between switching transitions of the secondary side switching control signals and switching transitions of a secondary side clock signal, where the secondary side control circuit includes a clock recovery circuit to synchronize the secondary side clock signal to transitions in a sense coil voltage signal of the sense coil.

Isolated phase shifted DC to DC converter with secondary side regulation and sense coil to reconstruct primary phase

A synchronous rectifier circuit can include: a full-bridge rectifier circuit having first, second, third, and fourth switches, where a common node of the first and fourth switches is configured as a first input terminal of the synchronous rectifier circuit, and a common node of the second and third switches is configured as a second input terminal of the synchronous rectifier circuit; a switching control circuit configured to generate a first control signal to control the first and third switches, and a second control signal to control the second and fourth switches; and the switching control circuit being configured to self-adjust the first and second control signals to control operating points of the first, second, third, and fourth switches to be approximately ideal operating points.

Synchronous rectifier circuit and control method thereof

A circuit includes a conduction detector configured to monitor conduction of a body diode of a synchronous rectifier switch relative to a predetermined threshold and to generate a detector output that indicates conduction or non-conduction of the body diode. A window analyzer is configured to generate a timing signal to indicate if the synchronous rectifier switch is turned off prematurely or turned off late relative to an on-time turn off based on the detector output from the conduction detector. A controller is configured to adjust the timing of the synchronous rectifier switch based on whether the timing signal indicates that the synchronous rectifier switch is turned off prematurely or turned off late relative to the on-time turn off.

Fan Wang

Papers

Automatic timing adjustment for synchronous rectifier circuit