Patents by Inventor Wanfeng Zhang

Wanfeng Zhang has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Publication number: 20120319621
    Abstract: A system includes a transformer. The transformer includes a first coil and a second coil. The first coil is configured to receive a first voltage based on an output of a switching circuit. The second coil is configured to generate a first current based on the first voltage to power a solid-state load. The system also includes a third coil. The third coil is configured to generate a second voltage based on the first voltage.
    Type: Application
    Filed: June 18, 2012
    Publication date: December 20, 2012
    Inventors: Sehat Sutardja, Pantas Sutardja, Wanfeng Zhang, Jinho Choi
  • Publication number: 20120230065
    Abstract: A system including a switch configured to supply power to a load. A first comparator is configured to compare a first current through the switch to a first threshold. A second comparator is configured to compare the first current through the switch to a second threshold. The second threshold is greater than the first threshold. A current control module is configured to turn off the switch (i) for a first duration in response to the first current through the switch being greater than or equal to the first threshold and (ii) for a second duration in response to the first current through the switch being greater than or equal to the second threshold. The current control module is configured to adjust the second duration based on a difference between an estimated current through the load and a desired current through the load.
    Type: Application
    Filed: February 24, 2012
    Publication date: September 13, 2012
    Inventors: Jinho Choi, Hao Peng, Wanfeng Zhang, Tuyen Doan
  • Publication number: 20120212258
    Abstract: Methods, circuits, and systems for determining the presence of a chopped input signal are disclosed. A digital signal generator can produce multiple digital signals when an alternating current (AC) signal input reaches multiple threshold voltages. The times at which the threshold voltages are reached can be determined by looking at the times at which the digital signals go high and low. The differences between the times at which the digital signals go high and low are used to determine if the AC signal input is a leading or trailing edge chopped signal. The AC input signal is a leading edge chopped signal when the difference between the times at which the digital signals go high is less than a predetermined time threshold, and is a trailing edge chopped signal when the difference between the times at which the digital signals go low is less than a predetermined time threshold.
    Type: Application
    Filed: February 16, 2012
    Publication date: August 23, 2012
    Inventors: Jinho Choi, Hao Peng, Wanfeng Zhang, Tuyen Doan
  • Publication number: 20120163040
    Abstract: 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 Nth pulse 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.
    Type: Application
    Filed: December 23, 2011
    Publication date: June 28, 2012
    Inventors: Hong Liang Zhang, Sen Dou, Ravishanker Krishnamoorthy, Biing Long Shu, Wanfeng Zhang
  • Publication number: 20120091910
    Abstract: In one embodiment, an apparatus includes circuitry configured to receive a dimming input to control a dimming level of a lamp. Also, the apparatus includes circuitry configured to generate a control signal based on the dimming input. The control signal indicates the dimming level for a converter of the lamp and the converter is configured to interpret the control signal to control to the dimming level of the lamp using a sinusoidal signal.
    Type: Application
    Filed: October 13, 2011
    Publication date: April 19, 2012
    Inventors: Wanfeng Zhang, Radu Pitigoi-Aron, Daniel Reed
  • Publication number: 20120081029
    Abstract: In one embodiment, an apparatus includes a transformer comprising a primary side and a secondary side. A switch is coupled to the primary side. A control signal circuit is configured to: sample a first current on the primary side of the transformer; estimate a second current value on the secondary side of the transformer using the sampling of the first current on the primary side and a turn ratio of the transformer; and output a signal to control a turn on time for the switch.
    Type: Application
    Filed: September 27, 2011
    Publication date: April 5, 2012
    Inventors: Jinho Choi, Yangsoo Park, Wanfeng Zhang
  • Publication number: 20120002449
    Abstract: In one embodiment, an apparatus includes a sampling component. The sampling component receives a first voltage signal on a primary side of a transformer and monitors the first voltage signal to determine a voltage sampling time. The determined voltage sampling time is when the first voltage signal is used to estimate a second voltage level on a secondary side of the transformer. The first component further samples the first voltage signal at the voltage sampling time to determine a first voltage level. A second component outputs a control signal to control a switch to regulate the second voltage level based on the first voltage level.
    Type: Application
    Filed: June 13, 2011
    Publication date: January 5, 2012
    Inventors: Yangsoo Park, Jinho Choi, Wanfeng Zhang
  • Publication number: 20110266976
    Abstract: An apparatus includes a LED and a regulator circuit. The regulator circuit controls the current provided to the LED according to a calibration signal that is coupled to the current. The regulator circuit adjusts the output of the LED when the calibration signal is adjusted. In this manner, the LED may be calibrated to generate light at a desired brightness level and color level.
    Type: Application
    Filed: May 2, 2011
    Publication date: November 3, 2011
    Inventors: Wanfeng Zhang, Pantas Sutardja
  • Publication number: 20110241572
    Abstract: A system including a calibration module, a selection module, and a control module. The calibration module is configured to generate calibration data for a plurality of light emitting diodes (LEDs). The calibration data include current through the LEDs and corresponding luminosities of the LEDs. The selection module is configured to select one of a plurality of templates corresponding to the LEDs. The selected template includes at least one of temperature, current, and voltage characteristics of the LEDs. The control module is configured to determine a temperature of the LEDs and adjust current through the LEDs based on the temperature, the selected template, and the calibration data to maintain a luminosity of the LEDs at a predetermined luminosity.
    Type: Application
    Filed: April 1, 2011
    Publication date: October 6, 2011
    Inventors: Wanfeng Zhang, Radu Pitigoi-Aron
  • Publication number: 20110199014
    Abstract: In one embodiment, a dimmer circuit is coupled to an electronic load and receives an alternating current (AC) signal. A phase control circuit turns the dimmer circuit on for a first portion of the AC signal to turn on the electronic load. The dimmer circuit turns off during a second portion of the AC signal to turn off the electronic load. A switch is coupled to the phase control circuit. The switch is controlled to couple the phase control circuit to ground when the dimmer circuit is off where the switch is part of a power supply supplying power to the electronic load.
    Type: Application
    Filed: February 8, 2011
    Publication date: August 18, 2011
    Inventors: Radu Pitigoi-Aron, Wanfeng Zhang, Jinho Choi
  • Publication number: 20110148312
    Abstract: A system includes a plurality of light emitting diodes (LEDs) and a control module configured to generate pulse width modulated (PWM) pulses to drive the LEDs. The LEDs and the control module are integrated in an integrated circuit (IC) package.
    Type: Application
    Filed: December 10, 2010
    Publication date: June 23, 2011
    Inventors: Wanfeng Zhang, Albert Wu
  • Publication number: 20110038184
    Abstract: An isolated alternating current (AC)-direct current (DC) converter is disclosed. The isolated AC-DC converter comprises a slave control circuit including a slave driver module configured to receive a command and to control coupling of the slave control circuit to a primary-side inductor of a transformer based on the command, a master control circuit coupled to a secondary-side inductor of the transformer, the master control circuit including a master control module configured to sense a feedback voltage across a load and to generate the command based on the feedback voltage and a reference voltage, and a coupler configured to communicate the command from the master control module to the slave driver module and to provide isolation between the master control module and the slave driver module.
    Type: Application
    Filed: June 14, 2010
    Publication date: February 17, 2011
    Inventors: Sehat Sutardja, Ravishanker Krishnamoorthy, Wanfeng Zhang
  • Publication number: 20100253395
    Abstract: Particular embodiments generally relate to driver structures. In one embodiment, an apparatus includes a first driver that drives a first current for a transistor. The first driver drives the first current during a first portion of a drive time of driving the transistor. The first driver is OFF during a second portion. A second driver drives a second current for the transistor during the second portion.
    Type: Application
    Filed: April 1, 2010
    Publication date: October 7, 2010
    Inventors: Radu Pitigoi-Aron, Wanfeng Zhang
  • Publication number: 20100090671
    Abstract: In one embodiment, the present invention includes a circuit comprising a voltage estimation circuit to receive a first voltage and generate an estimation of an output voltage of a power conversion circuit based on the first voltage. The first voltage is from a circuit node between a first terminal of a switch and a first terminal of an inductor. The circuit further comprises a current estimation circuit to receive a first current and generate an estimation of an output current of the power conversion circuit based on the first current. The first current is a current through the switch. The circuit further comprises a pulse width modulation circuit to produce a pulse width modulated signal based on the estimation of an output voltage and the estimation of an output current.
    Type: Application
    Filed: September 10, 2009
    Publication date: April 15, 2010
    Inventors: Wanfeng Zhang, Jianqing Lin, Shaoan Dai
  • Publication number: 20100079081
    Abstract: Apparatuses, methods, systems, and circuits for light-emitting diode (LED) control are disclosed. In one embodiment, an LED control circuit can include a first pin receiving an input voltage supply; a second pin receiving a primary signal from a primary winding of a transformer coupled to the LED; a third pin coupled to a ground supply; and logic configured to estimate an output current and/or output voltage at the LED coupled to a secondary winding of the transformer from the input voltage supply and the primary signal.
    Type: Application
    Filed: August 25, 2009
    Publication date: April 1, 2010
    Inventors: Wanfeng ZHANG, Jianqing LIN, Shaoan DAI
  • Patent number: 7514913
    Abstract: A method and apparatus to implement parallel current mode control that is suitable for digital and analog implementation. A duty cycle algorithm is composed of a voltage term and a parallel current term which depends on the inductor current change between the inductor current value at the beginning of a switching cycle and the reference inductor current value at the end of that switching cycle. Parallel current mode control can be applied to all DC-DC converters, including both non-isolated and isolated topologies. It can also be applied to AC-DC converters with power factor correction.
    Type: Grant
    Filed: December 5, 2007
    Date of Patent: April 7, 2009
    Assignee: iWatt Inc.
    Inventors: Wanfeng Zhang, Yan-Fei Liu, Bin Wu
  • Publication number: 20080122422
    Abstract: A method and apparatus to implement parallel current mode control that is suitable for digital and analog implementation. A duty cycle algorithm is composed of a voltage term and a parallel current term which depends on the inductor current change between the inductor current value at the beginning of a switching cycle and the reference inductor current value at the end of that switching cycle. Parallel current mode control can be applied to all DC-DC converters, including both non-isolated and isolated topologies. It can also be applied to AC-DC converters with power factor correction.
    Type: Application
    Filed: December 5, 2007
    Publication date: May 29, 2008
    Applicant: IWATT INC.
    Inventors: Wanfeng Zhang, Yan-Fei Liu, Bin Wu
  • Patent number: 7317625
    Abstract: A method and apparatus to implement parallel current mode control that is suitable for digital and analog implementation. A duty cycle algorithm is composed of a voltage term and a parallel current term which depends on the inductor current change between the inductor current value at the beginning of a switching cycle and the reference inductor current value at the end of that switching cycle. Parallel current mode control can be applied to all DC-DC converters, including both non-isolated and isolated topologies. It can also be applied to AC-DC converters with power factor correction.
    Type: Grant
    Filed: June 4, 2004
    Date of Patent: January 8, 2008
    Assignee: iWatt Inc.
    Inventors: Wanfeng Zhang, Yan-Fei Liu, Bin Wu
  • Publication number: 20050270813
    Abstract: A method and apparatus to implement parallel current mode control that is suitable for digital and analog implementation. A duty cycle algorithm is composed of a voltage term and a parallel current term which depends on the inductor current change between the inductor current value at the beginning of a switching cycle and the reference inductor current value at the end of that switching cycle. Parallel current mode control can be applied to all DC-DC converters, including both non-isolated and isolated topologies. It can also be applied to AC-DC converters with power factor correction.
    Type: Application
    Filed: June 4, 2004
    Publication date: December 8, 2005
    Inventors: Wanfeng Zhang, Yan-Fei Liu, Bin Wu