Apple Inc.

Vijay G Phadke

Prudhvi Mohan Maddineni

Liang Zhou

Bogdan Tudor Bucheru

Joao Luiz Andres

Marco A Davila, Jr

Balal Khan

An AC-DC power supply can include a PFC stage that receives a rectified AC input voltage and produces an intermediate DC bus voltage; a DC-DC stage that receives the intermediate DC bus voltage and produces a regulated DC output voltage; and a digital controller. The digital controller can include a relatively faster DC-DC stage controller that receives DC-DC stage feedback signal(s) and produces DC-DC drive signal(s) for switching device(s) of the DC-DC stage; a relatively slower PFC stage controller that receives PFC feedback signal(s) and produces PFC drive signal(s) for switching device(s) of the PFC stage; and control logic that receives periodic output power indications of the AC-DC power supply and uses them to cause the PFC drive signal(s) to respond to a change in output power of the AC-DC power supply more quickly than would be achieved by the relatively slower PFC stage controller.

Dynamic control of AC-DC power converter PFC front end during load transients

A quasi-planar transformer can include a first winding comprising one or more turns of wire, a second winding comprising one or more turns of a conductive trace disposed on a printed circuit board, and a magnetic core positioned with respect to the first and second windings so as to provide a magnetic flux path coupling the first and second windings. The first winding can be a primary winding having a first half wound in a clockwise direction on a first side of the printed circuit board and a second half wound in a counterclockwise direction on a second side of the printed circuit board, wherein the first and second halves are formed of a single continuous wire. The single continuous wire can pass through an opening in the printed circuit board. The first and second halves of the primary winding can be secured to the printed circuit board.

Quasi-planar transformer construction

Disclosed herein is an improved flyback converter that separates the magnetic components of the converter into a transformer and a separate, discrete energy storage inductor. This arrangement can improve the operating efficiency of the converter by reducing the commutation losses as compared to a conventional flyback converter. The magnetic components may be constructed on separate magnetic cores or may be constructed on magnetic cores having at least one common element, thereby allowing for at least partial magnetic flux cancellation in a portion of the core, reducing core losses.

Flyback converters with improved magnetic configurations

A two-stage power converter can incorporate a buck pre-regulator and a resonant bus converter. Such a converter may be operated to achieve unconditional soft switching operation (zero voltage switching a/k/a ZVS) over a wide input and output range, while delivering excellent power conversion efficiency at lower power levels and in a no load condition.

High performance two stage power converter with enhanced light load management

Power converter magnetic configurations

Disclosed herein are synchronous rectifier control techniques for Discontinuous Current Mode (DCM) converters. These techniques may be particularly advantageous where the current shape is triangular in nature with a fixed down-slope. Such converters may include DCM flyback converters and DCM buck converters. The proposed control techniques can reduce body diode conduction of the synchronous rectifier and optimize turn-off timing, while negating the effect of parasitic circuit elements. These techniques may also help simplify the control of synchronous rectifiers operated in parallel mode. Finally, such techniques may also help achieve higher performance in variable output voltage converters and converters that operate at high switching frequencies.

High performance synchronous rectification in discontinuous current mode converters

Systems and methods for operating improved flyback converters are disclosed, in which leakage energy is returned to the input power source rather than to the output load, while still achieving zero voltage switching (i.e., ZVS) operation. In some embodiments, the improved converters may transfer the energy stored in the leakage inductance to a snubber capacitor(s) at the instant of turning off of the control switch. Further, the improved converter embodiments may also retain the stored energy in the snubber capacitor(s) when the power is being delivered to the load by the secondary circuits. The improved converter embodiments may start the transfer of leakage energy stored in the snubber capacitor(s) to the primary winding once the energy stored in the transformer is delivered to the load. Finally, the improved converter embodiments may intelligently control their active clamp switches such that all leakage inductance energy is returned to the input source.

Systems and methods of operation for power converters having series-parallel mode active clamps

This disclosure describes a flyback converter with a series-parallel mode (SPM) active clamp. The active clamp, coupled in parallel with the primary coil, may include a clamp switch, two or more snubber capacitors, and associated diodes. The active clamp may be configured to absorb and retain the leakage energy from the leakage inductance of the flyback converter. The clamp switch may be turned on selectively as the primary switch approaches one of a plurality peak values to adjust frequencies of the switching devices. With the active clamp circuit, the flyback converter may first re-capture the leakage energy in the active clamp circuit and then recover it back to the power source.

Control of series-parallel mode (SPM) clamped flyback converter

A flyback converter can include an auxiliary winding magnetically coupled to the secondary (output) for sensing a reflected output voltage. A controller can operate a power switch of the flyback converter in a burst mode to deliver a number of pulses, causing the output voltage to reach a threshold, and thereafter suspend switching for a predetermined time period before delivering a further number of pulses. The delivered number of pulses can be counted, and, responsive to a determination that the count is less than a predetermined minimum number of pulses, the predetermined time period can be increased. Responsive to a determination that the count is greater than a predetermined maximum number of pulses, the predetermined time period can be decreased.

Adaptive wakeup time control in burst mode of a primary side regulated flyback converter

A flyback converter can include a series-parallel mode (SPM) active clamp circuit. The active clamp circuit, coupled in parallel with the primary coil, may include multiple networks in parallel. The first network, comprising a switch, one or more snubber capacitors, and one or more diodes, may be configured to absorb and retain the leakage energy from the leakage inductance of the flyback converter. The second network, comprising another switch and a diode, may be configured to create a circulating circuit for the flow of current through the primary coil in a reverse direction and clamp the current to a threshold level. With the active clamp circuit, the flyback converter may first re-capture the leakage energy in the active clamp circuit and then recover it back to the power source.

Growing community of inventors

Santa Clara, CA, United States of America

Vijay G Phadke