Patents by Inventor Nai-Chi Lee
Nai-Chi Lee 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).
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Patent number: 11272591Abstract: An LED driver includes a voltage detector and a controller. The voltage detector is configured to couple to an LED string comprising a plurality of series-coupled LEDs and to detect a voltage across the LED string to generate a feedback signal. The controller is configured to control an amount of current provided to the LED string in response to the feedback signal, with an amount of power provided to the LED string being substantially constant. The voltage detector can be coupled in parallel with the LED string, and may be a resistor divider. The controller is further configured to couple to a DC-DC converter comprising a switch controlled by the controller and configured to generate an output current and an output voltage coupled to the LED string to provide the amount of power to the LED string.Type: GrantFiled: December 2, 2020Date of Patent: March 8, 2022Assignee: Allegro MicroSystems, LLCInventor: Nai-Chi Lee
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Patent number: 10412797Abstract: A driver coupled to a configurable load includes a first switch coupled between an intermediate node of the load and a converter supply voltage and a second switch coupled between the converter supply voltage and a reference potential. A slew rate control circuit is responsive to a command input signal and to a feedback voltage across the first and second switches and is configured to generate switch control signals with a controllable slew rate for coupling to control terminals of the first and second switches. In an embodiment, the command input signal includes a load configuration command and a converter mode command.Type: GrantFiled: October 2, 2017Date of Patent: September 10, 2019Assignee: Allegro MicroSystems, LLCInventor: Nai-Chi Lee
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Publication number: 20180049283Abstract: A driver coupled to a configurable load includes a first switch coupled between an intermediate node of the load and a converter supply voltage and a second switch coupled between the converter supply voltage and a reference potential. A slew rate control circuit is responsive to a command input signal and to a feedback voltage across the first and second switches and is configured to generate switch control signals with a controllable slew rate for coupling to control terminals of the first and second switches. In an embodiment, the command input signal includes a load configuration command and a converter mode command.Type: ApplicationFiled: October 2, 2017Publication date: February 15, 2018Applicant: Allegro MicroSystems, LLCInventor: Nai-Chi Lee
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Patent number: 9825528Abstract: In one aspect, an integrated circuit (IC) is configured to receive an input signal and includes a boost duty cycle control circuit configured to provide duty cycle control to a power conversion stage configured to drive a load. The power conversion stage is configured to receive an input voltage. The IC also includes a current control circuit configured to control current of a first current source coupled to the first load and an inverter configured to provide an output signal comprising a negative of the input voltage, the output of the inverter configured to be coupled to the boost duty cycle control circuit.Type: GrantFiled: December 28, 2015Date of Patent: November 21, 2017Assignee: Allegro Microsystems, LLCInventors: Nai-Chi Lee, Pranav Raval
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Patent number: 9781789Abstract: An LED driver for driving a plurality of series-coupled LEDs includes a bypass switch having first and second terminals coupled across a portion of the LEDs and a control terminal. A slew rate control circuit is responsive to a command input signal and to a feedback voltage associated with the bypass switch and is configured to generate a bypass switch control signal with a controllable slew rate. The slew rate control circuit is further configured to detect a rate of change of the switch feedback voltage and establish the bypass switch slew rate in response to the detected rate of change. Also described is method for controlling a bypass switch coupled across a portion of a plurality of series-coupled LEDs including detecting a rate of change of a voltage associated with the bypass switch and generating a control signal for the bypass switch in response to a command input signal and to the detected rate of change of the voltage.Type: GrantFiled: May 13, 2016Date of Patent: October 3, 2017Assignee: Allegro Microsystems, LLCInventors: Nai-Chi Lee, Vijay Mangtani
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Publication number: 20170187280Abstract: In one aspect, an integrated circuit (IC) is configured to receive an input signal and includes a boost duty cycle control circuit configured to provide duty cycle control to a power conversion stage configured to drive a load. The power conversion stage is configured to receive an input voltage. The IC also includes a current control circuit configured to control current of a first current source coupled to the first load and an inverter configured to provide an output signal comprising a negative of the input voltage, the output of the inverter configured to be coupled to the boost duty cycle control circuit.Type: ApplicationFiled: December 28, 2015Publication date: June 29, 2017Applicant: Allegro Microsystems, LLCInventors: Nai-Chi Lee, Pranav Raval
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Patent number: 9642203Abstract: In one aspect, an integrated circuit (IC) is configured to receive an input signal. The IC includes a boost switch driver configured to provide a switching operation to a boost converter to drive a string of light emitting diodes (LEDs), a current sink driver connected to a current source and configured to provide a current signal to the string of LEDs, and a delay module configured to delay the current signal to the string of LEDs with respect to the input signal.Type: GrantFiled: June 7, 2016Date of Patent: May 2, 2017Assignee: Allegro Microsystems, LLCInventors: Nai-Chi Lee, Pranav Raval
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Patent number: 9615413Abstract: An LED driver circuit selects a regulated voltage value for use in driving one or more LEDs based on dimming duty cycle. In some embodiments, the regulated voltage value may be selected in accordance with a function that decreases monotonically with increasing dimming duty cycle. In this manner, LED current accuracy can be achieved at lower dimming duty cycles, while still achieving enhanced operational efficiency at higher dimming duty cycles.Type: GrantFiled: August 29, 2013Date of Patent: April 4, 2017Assignee: Allegro Microsystems, LLCInventors: Pranav Raval, Bassem Alnahas, Nai-Chi Lee
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Patent number: 9538601Abstract: A driver circuit for driving one or more loads in a controlled manner includes multiple operational modes. In one mode, bypass switching may be used to adjust a drive signal applied to the one or more loads. In another mode, a DC-DC converter may be used to adjust the drive signal applied to the one or more loads. In at least one embodiment, the driver circuit is a light emitting diode driver circuit.Type: GrantFiled: October 8, 2015Date of Patent: January 3, 2017Assignee: ALLEGRO MICROSYSTEMS, LLCInventors: Vijay Mangtani, Nai-Chi Lee
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Publication number: 20160366742Abstract: In one aspect, an integrated circuit (IC) is configured to receive an input signal. The IC includes a boost switch driver configured to provide a switching operation to a boost converter to drive a string of light emitting diodes (LEDs), a current sink driver connected to a current source and configured to provide a current signal to the string of LEDs, and a delay module configured to delay the current signal to the string of LEDs with respect to the input signal.Type: ApplicationFiled: June 7, 2016Publication date: December 15, 2016Applicant: Allegro Microsystems, LLCInventors: Nai-Chi Lee, Pranav Raval
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Patent number: 8994279Abstract: Control circuits and techniques are provided for use with DC-DC converters. The circuits and techniques may, in some implementations, be used with LED driver systems. In some embodiments control circuits are provided that rely on multiple different feedback paths to adjust a duty cycle of a DC-DC converter. In some embodiments, control circuits are provided that switch between multiple capacitors to provide as duty cycle control signal for use with a DC-DC converter.Type: GrantFiled: January 29, 2013Date of Patent: March 31, 2015Assignee: Allegro Microsystems, LLCInventors: Pranav Raval, Gregory Szczeszynski, Bassem Alnahas, Nai-Chi Lee
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Publication number: 20150061528Abstract: An LED driver circuit selects a regulated voltage value for use in driving one or more LEDs based on dimming duty cycle. In some embodiments, the regulated voltage value may be selected in accordance with a function that decreases monotonically with increasing dimming duty cycle. In this manner, LED current accuracy can be achieved at lower dimming duty cycles, while still achieving enhanced operational efficiency at higher dimming duty cycles.Type: ApplicationFiled: August 29, 2013Publication date: March 5, 2015Applicant: Allegro Microsystems, LLCInventors: Pranav Raval, Bassem Alnahas, Nai-Chi Lee
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Publication number: 20140210359Abstract: Control circuits and techniques are provided for use with DC-DC converters. The circuits and techniques may, in some implementations, be used with LED driver systems. In some embodiments control circuits are provided that rely on multiple different feedback paths to adjust a duty cycle of a DC-DC converter. In some embodiments, control circuits are provided that switch between multiple capacitors to provide as duty cycle control signal for use with a DC-DC converter.Type: ApplicationFiled: January 29, 2013Publication date: July 31, 2014Inventors: Pranav Raval, Gregory Szczeszynski, Bassem Alnahas, Nai-Chi Lee
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Patent number: 8610371Abstract: In one aspect, a circuit includes a plurality of comparators. Each comparator is configured to receive a first input from a corresponding load of a plurality of loads and to receive a second input as a regulation voltage. The circuit also includes an amplifier configured to receive signals provided by the plurality of comparators, a pulse-width modulation (PWM) circuit configured to receive a control signal from the amplifier and to provide a signal to a primary switch to control voltage provided to the loads and an output switch sequencer coupled to each of the comparators and configured to provide control signals to control switches coupled to the primary switch enabling one control switch to be active at a time. Each control switch provides a voltage increase to a respective load of the plurality of loads if enabled.Type: GrantFiled: December 22, 2011Date of Patent: December 17, 2013Assignee: Allegro Microsystems, LLCInventors: Nai-Chi Lee, Gregory Szczeszynski, Vijay Mangtani
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Publication number: 20130162152Abstract: In one aspect, a circuit includes a plurality of comparators. Each comparator is configured to receive a first input from a corresponding load of a plurality of loads and to receive a second input as a regulation voltage. The circuit also includes an amplifier configured to receive signals provided by the plurality of comparators, a pulse-width modulation (PWM) circuit configured to receive a control signal from the amplifier and to provide a signal to a primary switch to control voltage provided to the loads and an output switch sequencer coupled to each of the comparators and configured to provide control signals to control switches coupled to the primary switch enabling one control switch to be active at a time. Each control switch provides a voltage increase to a respective load of the plurality of loads if enabled.Type: ApplicationFiled: December 22, 2011Publication date: June 27, 2013Applicant: Allegro Microsystems, Inc.Inventors: Nai-Chi Lee, Gregory Szczeszynski, Vijay Mangtani
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Patent number: 7787262Abstract: A capacitor charging circuit is provided with a primary side output voltage sensing circuit including an RC network having an RC time constant with a predetermined relationship to the RC time constant of the output capacitor. Once the capacitor voltage reaches a fully charged level, the charging mode is terminated. The output voltage is continuously detected by measuring the voltage across the primary side RC network that decays at a predetermined rate with respect to the output capacitor and the charging mode is commenced once the RC voltage falls to a predetermined level. According to a further aspect of the invention, a switch control circuit in a flyback converter controls the switch off time in response to detection of a change in the slope polarity of the voltage at a terminal of the switch.Type: GrantFiled: December 19, 2006Date of Patent: August 31, 2010Assignee: Allegro Microsystems, Inc.Inventors: Vijay Mangtani, Nai-Chi Lee, Tseng-Nan Tsai, John Humenick
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Patent number: 7449867Abstract: A multi-phase converter comprising 2N+1 inductors; and 2N+1 switching converters parallel connected and each including a switched node; wherein N is an even integer, a pair of said inductors are coupled and wound about a common core and each said coupled inductor is connected at one pole thereof to a respective switched node and at another pole thereof to an output node, and at least one of said inductors is uncoupled from the other inductors.Type: GrantFiled: July 21, 2006Date of Patent: November 11, 2008Assignee: International Rectifier CorporationInventors: Wenkai Wu, Nai-chi Lee, George Schuellein
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Publication number: 20080084717Abstract: A multi-phase converter comprising 2N+1 inductors; and 2N+1 switching converters parallel connected and each including a switched node; wherein N is an even integer, a pair of said inductors are coupled and wound about a common core and each said coupled inductor is connected at one pole thereof to a respective switched node and at another pole thereof to an output node, and at least one of said inductors is uncoupled from the other inductors.Type: ApplicationFiled: October 5, 2006Publication date: April 10, 2008Inventors: Wenkai Wu, Nai-chi Lee, George Schuellein
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Publication number: 20080019158Abstract: A multi-phase converter comprising 2N+1 inductors; and 2N+1 switching converters parallel connected and each including a switched node; wherein N is an even integer, a pair of said inductors are coupled and wound about a common core and each said coupled inductor is connected at one pole thereof to a respective switched node and at another pole thereof to an output node, and at least one of said inductors is uncoupled from the other inductors.Type: ApplicationFiled: July 21, 2006Publication date: January 24, 2008Applicant: INTERNATIONAL RECTIFIER CORPORATIONInventors: Wenkai Wu, Nai-chi Lee, George Schuellein
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Publication number: 20070103943Abstract: A capacitor charging circuit is provided with a primary side output voltage sensing circuit including an RC network having an RC time constant with a predetermined relationship to the RC time constant of the output capacitor. Once the capacitor voltage reaches a fully charged level, the charging mode is terminated. The output voltage is continuously detected by measuring the voltage across the primary side RC network that decays at a predetermined rate with respect to the output capacitor and the charging mode is commenced once the RC voltage falls to a predetermined level. According to a further aspect of the invention, a switch control circuit in a flyback converter controls the switch off time in response to detection of a change in the slope polarity of the voltage at a terminal of the switch.Type: ApplicationFiled: December 19, 2006Publication date: May 10, 2007Inventors: Vijay Mangtani, Nai-Chi Lee, Tseng-Nan Tsai, John Humenick