Patents by Inventor Ji Yeoul Ryoo

Ji Yeoul Ryoo 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).

  • Patent number: 10728969
    Abstract: Aspects of the subject technology relate to control circuitry for light-emitting diodes. The control circuitry may operate a light-emitting diode using a multi-peak pulse-width-modulation signal. The control circuitry may include a multi-stage driver having a relatively larger driver stage for providing a direct current through a light-emitting diode and a relatively smaller driver stage configured to cooperate with a pulse-width-modulation controller to pulse-width-modulate a current through the light-emitting diode.
    Type: Grant
    Filed: March 14, 2019
    Date of Patent: July 28, 2020
    Assignee: Apple Inc.
    Inventors: Mohammad J. Navabi-Shirazi, Alejandro Lara Ascorra, Asif Hussain, Ji Yeoul Ryoo, Jingdong Chen, Jun Qi, Manisha P. Pandya, Yanhui Xie
  • Patent number: 10678092
    Abstract: Aspects of the subject technology relate to display circuitry such as backlight control circuitry for operating parallel strings of light-emitting diodes (LEDs). A voltage supply circuit of the backlight control circuitry provides a common supply voltage to the strings of LEDs. Headroom control circuitry samples a residual voltage at the end of each string, determines a minimum of the residual voltages, and provides feedback, based on the determined minimum voltage, to the voltage supply circuit. A headroom control feedback loop may be provided including sampling lines coupled to the second end of each string of LEDs for sampling a residual voltage of each string. Headroom control circuitry may modify the supply voltage based on the minimum residual voltage. Sample-and-hold circuitry may be provided that holds the sampled residual voltages until the voltage supply circuit is ready for an update.
    Type: Grant
    Filed: September 21, 2017
    Date of Patent: June 9, 2020
    Assignee: APPLE INC.
    Inventors: Ji Yeoul Ryoo, Asif Hussain, Jingdong Chen, Mohammad J. Navabi-Shirazi, Yanhui Xie
  • Patent number: 10383186
    Abstract: Aspects of the subject technology relate to control circuitry for light-emitting diodes. The control circuitry may include a feedforward loop and a feedback loop for a power supply for the light-emitting diodes. The light-emitting diodes may be arranged in strings that are individually controllable by a current control transistor on the string. The feedforward loop may determine a total upcoming load current for the power supply based on reference voltages for controlling each of the current control transistors. The output of the power supply may be modified based on a combination of a current from the feedforward loop and a current from the feedback loop.
    Type: Grant
    Filed: October 16, 2017
    Date of Patent: August 13, 2019
    Assignee: Apple Inc.
    Inventors: Yanhui Xie, Asif Hussain, Ji Yeoul Ryoo, Jingdong Chen, Mohammad J. Navabi-Shirazi
  • Publication number: 20190215924
    Abstract: Aspects of the subject technology relate to control circuitry for light-emitting diodes. The control circuitry may operate a light-emitting diode using a multi-peak pulse-width-modulation signal. The control circuitry may include a multi-stage driver having a relatively larger driver stage for providing a direct current through a light-emitting diode and a relatively smaller driver stage configured to cooperate with a pulse-width-modulation controller to pulse-width-modulate a current through the light-emitting diode.
    Type: Application
    Filed: March 14, 2019
    Publication date: July 11, 2019
    Inventors: Mohammad J. Navabi-Shirazi, Alejandro Lara Ascorra, Asif Hussain, Ji Yeoul Ryoo, Jingdong Chen, Jun Qi, Manisha P. Pandya, Yanhui Xie
  • Patent number: 10237936
    Abstract: Aspects of the subject technology relate to control circuitry for light-emitting diodes. The control circuitry may operate a light-emitting diode using a multi-peak pulse-width-modulation signal. The control circuitry may include a multi-stage driver having a relatively larger driver stage for providing a direct current through a light-emitting diode and a relatively smaller driver stage configured to cooperate with a pulse-width-modulation controller to pulse-width-modulate a current through the light-emitting diode.
    Type: Grant
    Filed: October 16, 2017
    Date of Patent: March 19, 2019
    Assignee: Apple Inc.
    Inventors: Mohammad J. Navabi-Shirazi, Alejandro Lara Ascorra, Asif Hussain, Ji Yeoul Ryoo, Jingdong Chen, Jun Qi, Manisha P. Pandya, Yanhui Xie
  • Publication number: 20190059136
    Abstract: Aspects of the subject technology relate to control circuitry for light-emitting diodes. The control circuitry may operate a light-emitting diode using a multi-peak pulse-width-modulation signal. The control circuitry may include a multi-stage driver having a relatively larger driver stage for providing a direct current through a light-emitting diode and a relatively smaller driver stage configured to cooperate with a pulse-width-modulation controller to pulse-width-modulate a current through the light-emitting diode.
    Type: Application
    Filed: October 16, 2017
    Publication date: February 21, 2019
    Inventors: Mohammad J. NAVABI-SHIRAZI, Alejandro Lara ASCORRA, Asif HUSSAIN, Ji Yeoul RYOO, Jingdong CHEN, Jun QI, Manisha P. PANDYA, Yanhui XIE
  • Publication number: 20190053337
    Abstract: Aspects of the subject technology relate to control circuitry for light-emitting diodes. The control circuitry may include a feedforward loop and a feedback loop for a power supply for the light-emitting diodes. The light-emitting diodes may be arranged in strings that are individually controllable by a current control transistor on the string. The feedforward loop may determine a total upcoming load current for the power supply based on reference voltages for controlling each of the current control transistors. The output of the power supply may be modified based on a combination of a current from the feedforward loop and a current from the feedback loop.
    Type: Application
    Filed: October 16, 2017
    Publication date: February 14, 2019
    Inventors: Yanhui XIE, Asif HUSSAIN, Ji Yeoul RYOO, Jingdong CHEN, Mohammad J. NAVABI-SHIRAZI
  • Publication number: 20180373094
    Abstract: Aspects of the subject technology relate to display circuitry such as backlight control circuitry for operating parallel strings of light-emitting diodes (LEDs). A voltage supply circuit of the backlight control circuitry provides a common supply voltage to the strings of LEDs. Headroom control circuitry samples a residual voltage at the end of each string, determines a minimum of the residual voltages, and provides feedback, based on the determined minimum voltage, to the voltage supply circuit. A headroom control feedback loop may be provided including sampling lines coupled to the second end of each string of LEDs for sampling a residual voltage of each string. Headroom control circuitry may modify the supply voltage based on the minimum residual voltage. Sample-and-hold circuitry may be provided that holds the sampled residual voltages until the voltage supply circuit is ready for an update.
    Type: Application
    Filed: September 21, 2017
    Publication date: December 27, 2018
    Inventors: Ji Yeoul RYOO, Asif HUSSAIN, Jingdong CHEN, Mohammad J. NAVABI-SHIRAZI, Yanhui XIE
  • Patent number: 8446138
    Abstract: A stability compensation circuit and a DC-DC converter including the same are provided. When an output voltage of the DC-DC converter decreases more than a predetermined value, the stability compensation circuit quickly charges an integral capacitor by using an additional converter or by reducing an effective resistance of a charging circuit which charges the capacitor. Since an output voltage of an integrator in the stability compensation circuit is enabled to quickly reach a control voltage, the instant decrease of the output voltage of the DC-DC converter can be quickly compensated for.
    Type: Grant
    Filed: August 31, 2009
    Date of Patent: May 21, 2013
    Assignee: Samsung Electronics Co., Ltd.
    Inventor: Ji Yeoul Ryoo
  • Patent number: 8054112
    Abstract: A reset control apparatus may include a first reference generator adapted to output a first reference value in response to an enable signal from an external power source, a second reference generator adapted to receive the first reference value and to output a second reference value, and a set signal generator adapted to output a set signal when the second reference value exceeds a predetermined value.
    Type: Grant
    Filed: April 30, 2008
    Date of Patent: November 8, 2011
    Assignee: Samsung Electronics Co., Ltd.
    Inventor: Ji-Yeoul Ryoo
  • Patent number: 8054604
    Abstract: This disclosure provides a method and apparatus for reducing an inrush current inflowing from an external power source during an initial transient state. The method may include generating a first signal based on a level of internal voltage. The first signal may linearly increase or decrease, wherein the slope of the first signal may be fixed. The method may further include comparing the first signal with the reference voltage, and controlling an overcurrent prevention function based on the comparison results. An inrush current reducing device may include a reference voltage generating unit configured to compare a first signal and the reference voltage to control an overcurrent sensing gain, a gain unit configured to compare a first signal and the reference voltage to control an overcurrent sensing gain, and an overcurrent prevention signal generating unit configured to control an overcurrent prevention function based on the comparison results.
    Type: Grant
    Filed: July 28, 2008
    Date of Patent: November 8, 2011
    Assignee: Samsung Electronics Co., Ltd.
    Inventor: Ji-Yeoul Ryoo
  • Patent number: 8022680
    Abstract: A power converter includes a power switch adapted to receive an input power from an external power source and to generate an output power, and an adaptive oscillator adapted to output an adaptive minimum-on signal of the power switch in response to a change in measured magnitude of at least one of the input power and the output power.
    Type: Grant
    Filed: March 28, 2008
    Date of Patent: September 20, 2011
    Assignee: Samsung Electronics Co., Ltd.
    Inventor: Ji-Yeoul Ryoo
  • Patent number: 8022574
    Abstract: A maximum voltage source selector adapted for use in a semiconductor device operative in a disable state or an enable state is disclosed. The maximum voltage source selector includes an output unit having an output node providing a maximum voltage selected from a first input voltage and a second input voltage. First and second gate transistors are commonly coupled to the output node and are respectively configured to select and provide the greater of the first and second input voltages to the output node in response to first and second selection signals without regard to whether the semiconductor device is in the disable state or the enable state. A selection unit generates the first and second selection signals in response to the first and second input voltages.
    Type: Grant
    Filed: November 24, 2008
    Date of Patent: September 20, 2011
    Assignee: Samsung Electronics Co., Ltd.
    Inventor: Ji-Yeoul Ryoo
  • Patent number: 7948300
    Abstract: A negative supply voltage generating circuit includes a pulse generating circuit and a charge pump. The pulse generating circuit generates a first pulse signal and a second pulse signal in response to a clock signal. The first and second pulse signals have pulse widths different from each other. The charge pump generates a negative supply voltage by performing a charge pumping operation in response to the first and second pulse signals, and has a time interval between a switch-on time duration for charging a flying capacitor and a switch-on time duration for transmitting charges to an output capacitor.
    Type: Grant
    Filed: August 12, 2009
    Date of Patent: May 24, 2011
    Assignee: Samsung Electronics Co., Ltd.
    Inventor: Ji-Yeoul Ryoo
  • Publication number: 20100052640
    Abstract: A stability compensation circuit and a DC-DC converter including the same are provided. When an output voltage of the DC-DC converter decreases more than a predetermined value, the stability compensation circuit quickly charges an integral capacitor by using an additional converter or by reducing an effective resistance of a charging circuit which charges the capacitor. Since an output voltage of an integrator in the stability compensation circuit is enabled to quickly reach a control voltage, the instant decrease of the output voltage of the DC-DC converter can be quickly compensated for.
    Type: Application
    Filed: August 31, 2009
    Publication date: March 4, 2010
    Applicant: Samsung Electronics Co., Ltd.
    Inventor: Ji Yeoul Ryoo
  • Publication number: 20100039170
    Abstract: A negative supply voltage generating circuit includes a pulse generating circuit and a charge pump. The pulse generating circuit generates a first pulse signal and a second pulse signal in response to a clock signal. The first and second pulse signals have pulse widths different from each other. The charge pump generates a negative supply voltage by performing a charge pumping operation in response to the first and second pulse signals, and has a time interval between a switch-on time duration for charging a flying capacitor and a switch-on time duration for transmitting charges to an output capacitor.
    Type: Application
    Filed: August 12, 2009
    Publication date: February 18, 2010
    Applicant: SAMSUNG ELECTRONICS CO., LTD.
    Inventor: Ji-Yeoul Ryoo
  • Publication number: 20090134708
    Abstract: A maximum voltage source selector adapted for use in a semiconductor device operative in a disable state or an enable state is disclosed. The maximum voltage source selector includes an output unit having an output node providing a maximum voltage selected from a first input voltage and a second input voltage. First and second gate transistors are commonly coupled to the output node and are respectively configured to select and provide the greater of the first and second input voltages to the output node in response to first and second selection signals without regard to whether the semiconductor device is in the disable state or the enable state. A selection unit generates the first and second selection signals in response to the first and second input voltages.
    Type: Application
    Filed: November 24, 2008
    Publication date: May 28, 2009
    Applicant: SAMSUNG ELECTRONICS CO., LTD.
    Inventor: Ji-Yeoul RYOO
  • Publication number: 20090128113
    Abstract: A power converter having an auto conversion function for a pulse skip mode (PSM) and a related control method are provided. The power converter having an auto conversion function for a PSM and a control method thereof can provide a PSM capable of preventing unnecessary switching operations and, thus, improving the efficiency of the power converter by automatically switching to the PSM even when a load is small.
    Type: Application
    Filed: November 13, 2008
    Publication date: May 21, 2009
    Applicant: SAMSUNG ELECTRONICS CO., LTD.
    Inventor: Ji-Yeoul RYOO
  • Publication number: 20090058383
    Abstract: A power converter includes a power switch adapted to receive an input power from an external power source and to generate an output power, and an adaptive oscillator adapted to output an adaptive minimum-on signal of the power switch in response to a change in measured magnitude of at least one of the input power and the output power.
    Type: Application
    Filed: March 28, 2008
    Publication date: March 5, 2009
    Inventor: Ji-Yeoul Ryoo
  • Publication number: 20090040677
    Abstract: This disclosure provides a method and apparatus for reducing an inrush current inflowing from an external power source during an initial transient state. The method may include generating a first signal based on a level of internal voltage. The first signal may linearly increase or decrease, wherein the slope of the first signal may be fixed. The method may further include comparing the first signal with the reference voltage, and controlling an overcurrent prevention function based on the comparison results. An inrush current reducing device may include a reference voltage generating unit configured to compare a first signal and the reference voltage to control an overcurrent sensing gain, a gain unit configured to compare a first signal and the reference voltage to control an overcurrent sensing gain, and an overcurrent prevention signal generating unit configured to control an overcurrent prevention function based on the comparison results.
    Type: Application
    Filed: July 28, 2008
    Publication date: February 12, 2009
    Inventor: Ji-Yeoul Ryoo