Patents by Inventor Tillasthanam V. Sriram

Tillasthanam V. Sriram 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: 20160013637
    Abstract: A battery charging device for charging a battery with power drawn via a wall plug includes a full-wave rectifier of four diodes, two first metal-oxide varistors (MOVs), and a capacitor. The two MOVs are connected in parallel with the lower diodes of the bridge. The capacitor is arranged to electrically couple the anodes of the lower diode to a chassis ground of the device. This configuration allows for isolation voltage (hi-pot) testing to be performed with the MOVs in place.
    Type: Application
    Filed: July 9, 2014
    Publication date: January 14, 2016
    Inventors: ALEJANDRO OLIVARES PERL, TILLASTHANAM V. SRIRAM
  • Publication number: 20150049515
    Abstract: A LLC resonant converter that includes a plurality of electronic switches arranged to form a bridge and a controller. The bridge is operable to an operating mode that includes a full-bridge mode and a half-bridge mode. The controller is configured to adjust an operating frequency used to operate the bridge based on a comparison of a set-point value to an output value of an output voltage generated by converter, change the operating mode to the half-bridge mode if the operating mode is the full-bridge mode, an output current of the converter is less than a minimum current threshold, and the operating frequency is greater than a maximum frequency threshold, and change the operating mode to the full bridge mode if the operating mode is the half-bridge mode, and the operating frequency is less than a minimum frequency threshold.
    Type: Application
    Filed: August 13, 2013
    Publication date: February 19, 2015
    Inventors: JUDONG ZHAO, TILLASTHANAM V. SRIRAM
  • Patent number: 8344710
    Abstract: A control methodology for a two-stage PWM DC-DC conversion system, with transformer-isolation, in which the converter circuit input voltage is compared to a set voltage calibrated as a function of the desired output voltage and the maximum voltage conversion ratio provided by the second-stage converter. When the input voltage is above the set voltage, the second-stage converter is controlled to provide both output voltage regulation during normal operation and output current limiting during over-current conditions. However, when the input voltage is below the set voltage, the first-stage converter is controlled to provide output voltage regulation with minor output current limiting, and the second-stage converter is controlled to provide extended output current limiting independent of the input voltage.
    Type: Grant
    Filed: February 12, 2010
    Date of Patent: January 1, 2013
    Assignee: Delphi Technologies, Inc.
    Inventors: Tillasthanam V. Sriram, Alexandre M. S. Reis, Hua Zhou
  • Patent number: 7009311
    Abstract: A method is disclosed for starting a generator (10) from an internal combustion engine (14) to allow the generator (10) to charge a battery (32). The generator (10) includes a field bridge (36), having first (72) and second (74) switches, and a multiphase inverter (30), having upper (60, 62, 64) and lower (66, 68, 70) halves of switches. The method includes the step of providing a voltage from the battery (32) to the internal combustion engine (14). The voltage is used to crank the internal combustion engine (14). The first (72) and second (74) switches are closed to conduct and maximize the field current in the generator (10). The method includes the step of identifying when the internal combustion engine (14) is transitioning from a cranking state to an idling state. The method then switches the first (72) and second (74) switches off to decrease the field current to zero.
    Type: Grant
    Filed: August 24, 2004
    Date of Patent: March 7, 2006
    Assignee: Delphi Technologies, Inc.
    Inventor: Tillasthanam V. Sriram
  • Publication number: 20040012354
    Abstract: An electrical machine having a hybrid rotor, i.e., both electrical and permanent magnet excitation, and system and method for controlling such hybrid machine are provided.
    Type: Application
    Filed: April 22, 2003
    Publication date: January 22, 2004
    Inventors: Ronald J. Krefta, Tillasthanam V. Sriram
  • Patent number: 6670724
    Abstract: An improved series-pass over-voltage protection circuit for a motor vehicle electrical system includes first and second parallel connected power paths that respectively provide low current capability with low quiescent current drain, and high current capability with low on-resistance. The first power path, embodied by a P-channel MOSFET, supplies pass-through battery current to quiescent loads such as an engine control module during periods of vehicle inactivity. The second power path, embodied by at least one N-channel MOSFET, is activated by a gate voltage power supply during periods of vehicle activity. The second power path is configured to limit the circuit output voltage to a higher value than the first power path, so that the over-voltage protection during periods of vehicle activity is accomplished by the second power path.
    Type: Grant
    Filed: May 31, 2002
    Date of Patent: December 30, 2003
    Assignee: Delphi Technologies, Inc.
    Inventors: Jeffrey A. Ely, James W Ananias, Tillasthanam V. Sriram
  • Publication number: 20030222499
    Abstract: An improved series-pass over-voltage protection circuit for a motor vehicle electrical system includes first and second parallel connected power paths that respectively provide low current capability with low quiescent current drain, and high current capability with low on-resistance. The first power path, embodied by a P-channel MOSFET, supplies pass-through battery current to quiescent loads such as an engine control module during periods of vehicle inactivity. The second power path, embodied by at least one N-channel MOSFET, is activated by a gate voltage power supply during periods of vehicle activity. The second power path is configured to limit the circuit output voltage to a higher value than the first power path, so that the over-voltage protection during periods of vehicle activity is accomplished by the second power path.
    Type: Application
    Filed: May 31, 2002
    Publication date: December 4, 2003
    Inventors: Jeffrey A. Ely, James W. Ananias, Tillasthanam V. Sriram
  • Patent number: 6577097
    Abstract: Method and system for controlling a synchronous machine including a polyphase stator are provided. The machine may be used in a piece of equipment respectively as a generator and as a motor for starting an engine in the piece of equipment. The method allows to sense rotor position of the machine using a sensor assembly configured to supply a respective stream of pulses indicative of rotor position relative to each phase of the machine. The method further allows to process each stream of pulses from the sensor assembly to generate a first set of inverter control signals. The first set of inverter control signals is applied to an inverter circuit coupled to energize the phases of the stator to start the machine. The first set of control signals is configured to provide a first cycle-conduction angle relative to the zero-crossings of the respective phase EMF voltages of the machine to produce a sufficiently high level of torque during start of the machine.
    Type: Grant
    Filed: August 13, 2001
    Date of Patent: June 10, 2003
    Assignee: Delphi Technologies, Inc.
    Inventors: Ronald John Krefta, Tillasthanam V. Sriram
  • Publication number: 20030034755
    Abstract: Method and system for controlling a synchronous machine including a polyphase stator are provided. The machine may be used in a piece of equipment respectively as a generator and as a motor for starting an engine in the piece of equipment. The method allows to sense rotor position of the machine using a sensor assembly configured to supply a respective stream of pulses indicative of rotor position relative to each phase of the machine. The method further allows to process each stream of pulses from the sensor assembly to generate a first set of inverter control signals. The first set of inverter control signals is applied to an inverter circuit coupled to energize the phases of the stator to start the machine. The first set of control signals is configured to provide a first cycle-conduction angle relative to the zero-crossings of the respective phase EMF voltages of the machine to produce a sufficiently high level of torque during start of the machine.
    Type: Application
    Filed: August 13, 2001
    Publication date: February 20, 2003
    Inventors: Ronald John Krefta, Tillasthanam V. Sriram
  • Patent number: 6437462
    Abstract: Method and system for bi-directionally controlling power flow between two separate direct current power sources in a multi-stage power converter system are provided. The method allows providing at least first and second power converter stages coupled in parallel circuit to one another. The method further allows providing a first switching controller coupled to selectively actuate a pair of switching devices in the first power converter stage, and a second switching controller coupled to selectively actuate a pair of switching devices in the second power converter stage. One of the first and second switching controllers is selected as a master controller, and the other one of the first and second switching controllers is selected as a slave controller. An average voltage measurement is determined at a respective node of each the power converter stages. A compensating signal is generated based on the difference of the average voltage measurements at the respective nodes of each of the power converter stages.
    Type: Grant
    Filed: December 10, 2001
    Date of Patent: August 20, 2002
    Assignee: Delphi Technologies, Inc.
    Inventors: Robert Maple, Aurelien T. Mozipo, Tillasthanam V. Sriram
  • Patent number: 6366060
    Abstract: A MOSFET control circuit for use in generators with dual windings. The MOSFET switch consists of two or more MOSFETs connected between the upper and lower windings of a three-phase generator to permit the windings to operate in series or in parallel. The gate of one of the MOSFETs is controlled by a gate drive circuit that turns the MOSFET ON when the windings are to operate in series. The MOSFET is OFF when the windings are to operate in parallel.
    Type: Grant
    Filed: August 10, 2000
    Date of Patent: April 2, 2002
    Assignee: Delphi Technologies, Inc.
    Inventors: Jeffrey Alan Ely, Justin B. Lybbert, Tillasthanam V. Sriram, Steven Robert Mc Mullen
  • Patent number: 5739652
    Abstract: A sensorless method and apparatus for providing commutation timing signals for a brushless permanent magnet motor extracts the third harmonic back-emf of a three-phase stator winding and independently cyclically integrates the positive and negative half-cycles thereof and compares the results to a reference level associated with a desired commutation angle.
    Type: Grant
    Filed: December 20, 1996
    Date of Patent: April 14, 1998
    Assignee: General Motors Corporation
    Inventor: Tillasthanam V. Sriram