Marvell International Limited

Marvellworld Trade Ltd.

Hong Liang Zhang

Wanfeng Zhang

Ravishanker Krishnamoorthy

David Gozali

Sureshkumar Ramalingam

Hubertus Notohamiprodjo

Ying Tian Li

Jianqing Lin

Biing Long Shu

Sen Dou

In one embodiment, an apparatus for performing power factor correction is provided. A power factor corrector includes an input configured to sense a current from an input circuit. A reference generator generates a current limit based on an input voltage. The current limit reference is dynamically changed based on the input voltage. A control signal generator controls the current in the input circuit based on a comparison of the current and the generated current limit.

Adaptive current limit for power factor correction

Disclosed is flyback converter having a controller that performs a startup switching process when the flyback converter is powered up, and then performs normal switching afterward. The controller includes a pulse generator to generate a control signal for normal switching. During startup switching, the controller may generate a control signal by output every Npulse from the pulse generator. In another embodiment, the controller may generate pulses based on a sense signal provided from an input section of the flyback converter.

Reducing voltage stress in a flyback converter design

A comparator circuit for providing hysteresis comprises first and second differentially coupled transistors. The first of the differentially coupled transistors provides drain current to first and second load transistors. The second of the differentially coupled transistors provides drain current to third and fourth load transistors. In one example embodiment, the drain of the first of the differentially coupled transistors also drives the gate of the first and third load transistors, while the drain of the second of the differentially coupled transistors drives the gate of the second and fourth transistors.

Differential hysteresis comparator circuits and methods

Some of the embodiments of the present disclosure provide an apparatus comprising a voltage sensor circuit configured to generate a voltage feedback signal indicative of an output voltage of the apparatus, a current sensor circuit configured to generate a current feedback signal indicative of a load current of the apparatus, a converter configured to receive the current feedback signal, and generate a fault signal that is indicative of a fault condition associated with the load current, and an optocoupler configured to receive the voltage feedback signal and the fault signal, and generate a feedback signal that is indicative of the output voltage and indicative of the fault condition. Other embodiments are also described and claimed.

Multi-function feedback using an optocoupler

In a current switch, a bias generation circuit electrically connected to a high voltage power supply generates a bias current. The bias current is mirrored by a current mirror containing a first plurality of transistors to a first one of a second plurality of transistors. The first one of the second plurality of transistors amplifies the mirrored bias current and transmits the amplified bias current to a second one of the second plurality of transistors. The second one of the second plurality of transistors sinks the amplified bias current into a node shared by an internal reference voltage, thereby putting the node in a first logic state. A third one of the second plurality of transistors receives the amplified bias current from the second one of the second plurality of transistors and sinks the amplified bias current into a node shared by a gate of a high voltage p-type transistor, thereby putting the node in the first logic state. Putting both nodes in the first logic state turns off the high voltage transistor.

Current switch for high voltage process

In a method and apparatus for controlling power factor correction (PFC) in mixed operation modes, a frequency of the input voltage is obtained by detecting the zero crossing points of the input voltage. A peak of the input voltage is obtained by detecting input voltage with 90 degree phase. Thus, the present invention predicts the input voltage by its frequency and peak and the characteristic of the sine wave. A digital signal processor computes the duty and frequency of a boost switch, switching the operation mode of the boost converter among continuous mode, critical mode and discontinuous mode according to input voltage or the load. According to another aspect, the operation is switched to critical mode from the average current mode when a zero current is detected before the charging and recharging cycle of the boost switch is finished. Overcurrent protection may be achieved by controlling current in response to detected voltage to provide a substantially constant power level. The overcurrent protection may be adaptive in nature. In this aspect, an adaptive driver for a PFC controller reduces the slew rate of signals over the boost switch of the PFC controller. The adaptive driver may have a group of transistors which may be divided into a plurality of branches. The charging current through the boost switch may be increased by turning on an increasing number of branches until the voltage over the switch exceeds a reference voltage, and this may determine the number of branches to drive the boost switch during normal operation.

Method and apparatus for controlling power factor correction

An operational transconductance amplifier is configured with an asymmetric output current capability. When current sunk from the output exceeds a rated load, the normally equal input voltages diverge. A comparator coupled to the OTA inputs senses when the output current drain exceeds the rated load and changes state when the OTA input voltages diverge. When used in conjunction with a current mirror transistor of known proportion, current through an output transistor, such as quiescent current through the output stage of a class A/B amplifier, can be accurately detected. A current source in parallel with the OTA output can be used to offset the current sensing trigger point.

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Singapore, Singapore

Hong Liang Zhang