Apple Inc.

Zaohong Yang

Bogdan Tudor Bucheru

Behzad Mohtashemi

Juan Carlos Pastrana

Joao Luiz Andres

Poornima Mazumdar

Marco A Davila, Jr

Bharatkumar K Patel

A transformer-based switching power converter can include a slew rate limiter coupled to the switching stage and configured to limit rate of change of voltage across one or more switching devices of the switching stage, thereby reducing voltage spikes appearing on the secondary winding. The slew rate limiter may be configured to selectively operate to limit rate of change of voltage across one or more switching devices of the switching stage during startup of the switching stage, upon waking from burst mode, or at any time when zero voltage switching of the one or more switching devices is unavailable. The slew rate limiter can include at least one circuit element configured to selectively alter a time constant of a gate drive circuit of at least one switching device in the switching stage to increase a turn-on transition time of the at least one switching device.

Voltage slew rate limiters for transformer-based switching power converters

This disclosure relates to flyback transformer-based power converters that are capable of providing multiple output voltage levels. With respect to USB-PD adapter design, the flyback converter's output may be changed from 12V to 20V&#x2014;based on the charging device's request. By using a bias circuit that monitors an output voltage level of the flyback converter, a bias voltage for the bias circuit may be determined to improve efficiency of the flyback converter. Embodiments include a comparator, microcontroller or switches to compare output voltage levels and provide bias voltages to the bias circuit.

High efficiency primary and secondary bias flyback converter with dual outputs

Disclosed herein are a system, method and non-transitory program storage device that are intended to provide a control system with quick response for a multi-level power converter. The control system may regulate an output voltage of the power converter based on one or more feedback signals. The feedback signals may be generated based on a differential between the output voltage and a reference voltage. The control system may further include one or more feed-forward signals representative of either the output voltage or transients of the output voltage. The control system may further include one or more switches in parallel with the one or more capacitors to selectively enable and/or disable direct feed-forward and capacitive feed-forward responsive to the output voltage at different levels.

Control feedback loop design with fast transient response for multi-level converter

This disclosure relates to power converters that are capable of providing smooth transitions between multiple output voltage levels. The converter's output may need to be changed from, e.g., 5V to 12V, 15V, or 20V&#x2014;based on the charging device's request. By using improved power converter designs comprising both a flyback converter circuit and variable-frequency buck converter circuit that may each be selectively coupled to an output load, a more smooth, e.g., monotonous, transition between output voltage levels may be achieved. In particular, by varying the switching frequency of the buck converter in a controlled way, the output voltage of the power converter may rise monotonically during the transition between output voltage levels. According to some embodiments, once the output of the buck converter has reached its maximum value, the buck converter may be disabled, and the flyback converter may be enabled to begin supplying the output voltage to the load.

AC-DC power converters with improved voltage output level transitions

This disclosure describes an AC/DC power converter that produces multiple output voltage levels. The AC/DC power converter may include a gain adjustment circuit. The gain adjustment circuit may adjust the gain of a feedback signal of the converter in accordance with the converter's output voltage level. The gain adjustment circuit provides sufficient gain and phase margins to the converter and thus enhances the converter's stability.

Gain adjustment circuit to enhance stability of multiple-output AC/DC converters

The disclosed embodiments provide a system that operates a flyback converter. During activation of a synchronous rectifier (SR) controller on a secondary side of the power converter, the system temporarily disables driving of a gate of a metal-oxide-semiconductor field-effect transistor (MOSFET) by the SR controller to enable synchronization of the SR controller to a switching frequency on a primary side of the power converter. After driving of the gate of the MOSFET by the SR controller has been disabled for a pre-specified period, the system enables driving of the gate of the MOSFET by the SR controller.

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Plano, TX, United States of America

Zaohong Yang