Patents by Inventor Sreeraman Venkitasubrahmanian
Sreeraman Venkitasubrahmanian 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: 10542591Abstract: A light emitting diode (LED) apparatus is provided for driving a plurality of LED lamps (in parallel. The light emitting diode apparatus includes at least one LED driver circuit to provide a LED driving current for the plurality of LED lamps. The LED driver circuit includes a current setting resistance circuit for setting a maximum value of the LED driving current and a detection circuit to detect presence or absence of each of the plurality of LED lamps by detection of the current flowing through each of the LED lamps. The detection circuit adjusts the current setting resistance circuit based on the detection of presence or absence and the current setting resistance circuit includes a plurality of setting resistors and a plurality of transistors.Type: GrantFiled: July 12, 2017Date of Patent: January 21, 2020Assignee: SIGNIFY HOLDING B.V.Inventors: Yuhong Fang, Wilhelmus Josephus Cornelissen, Sreeraman Venkitasubrahmanian
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Publication number: 20190166662Abstract: A light emitting diode (LED) apparatus is configured for driving multiple LED lamps in parallel. The light emitting diode apparatus includes at least one of the LED lamps, and a detection circuit (151, 152) that detects presence of each of the LED driver circuit (140). The LED driver circuit adjusts power and/or current to the detected LED lamps based on the detection of presence.Type: ApplicationFiled: July 12, 2017Publication date: May 30, 2019Inventors: YUHONG FANG, WILHELMUS JOSEPHUS CORNELISSEN, SREERAMAN VENKITASUBRAHMANIAN
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Patent number: 9906153Abstract: A dimmer switch (110-x, 200, 400, 600, 700A, 700B, 1200) adapted to be coupled to an alternating current (AC) source and to a load so as to control an amount of power delivered from the AC source to the load, the dimmer switch may include: a triode for AC (TRIAC) (208, 408, 612) coupled between the AC source and the load, and which when triggered conducts to deliver a controlled amount of power from the AC source to the load for a corresponding half-cycle of one or more half cycles of the AC source. The dimmer switch may include first and second triggering circuits (606, 608) configured to trigger the TRIAC when charged after being enabled. One or more of the triggering circuits may be a self-balancing triggering circuit. The dimmer switch may further include a controller (412, 602, 1210) which selects and thereafter enables one or more of the first or second triggering circuits.Type: GrantFiled: January 23, 2013Date of Patent: February 27, 2018Assignee: PHILIPS LIGHTING HOLDING B.V.Inventors: Shangwu Chen, Sreeraman Venkitasubrahmanian
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Patent number: 9380685Abstract: A device provides a bypass path for leakage current of a neutral-less controller in a lighting control system for selectively supplying line voltage to a load. The device includes a dummy load, a voltage sensor, a bypass switch, a switch controller and a delay timer. The voltage sensor senses line voltage at an output of the neutral-less controller. The bypass switch selectively connects the dummy load in parallel with the lighting load. The switch controller activates the bypass switch to connect the dummy load in parallel with the lighting load when the line voltage is low, providing a bypass path for the leakage current, and deactivates the bypass switch after a delay period to disconnect the dummy load from being in parallel with the lighting load when the line voltage is high. The delay timer implements the delay period in response to the line voltage transitioning from low to high.Type: GrantFiled: July 5, 2013Date of Patent: June 28, 2016Assignee: KONINKLIJKE PHILIPS N.V.Inventors: Deepak Shivaram Shet, Prasannakumar Gore, Sreeraman Venkitasubrahmanian
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Publication number: 20150181682Abstract: A device provides a bypass path for leakage current of a neutral-less controller in a lighting control system for selectively supplying line voltage to a load. The device includes a dummy load, a voltage sensor, a bypass switch, a switch controller and a delay timer. The voltage sensor senses line voltage at an output of the neutral-less controller. The bypass switch selectively connects the dummy load in parallel with the lighting load. The switch controller activates the bypass switch to connect the dummy load in parallel with the lighting load when the line voltage is low, providing a bypass path for the leakage current, and deactivates the bypass switch after a delay period to disconnect the dummy load from being in parallel with the lighting load when the line voltage is high. The delay timer implements the delay period in response to the line voltage transitioning from low to high.Type: ApplicationFiled: July 5, 2013Publication date: June 25, 2015Inventors: Deepak Shivaram Shet, Prasannakumar Gore, Sreeraman Venkitasubrahmanian
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Publication number: 20150171762Abstract: A dimmer switch (110-x, 200, 400, 600, 700A, 700B,1200) adapted to be coupled to an alternating current (AC) source and to a load so as to control an amount of power delivered from the AC source to the load, the dimmer switch may include: a triode for AC (TRIAC) (208, 408, 612) coupled between the AC source and the load, and which when triggered conducts to deliver a controlled amount of power from the AC source to the load for a corresponding half-cycle of one or more half cycles of the AC source. The dimmer switch may include first and second triggering circuits (606, 608) configured to trigger the TRIAC when charged after being enabled. One or more of the triggering circuits may be a self-balancing triggering circuit. The dimmer switch may further include a controller (412, 602, 1210) which selects and thereafter enables one or more of the first or second triggering circuits.Type: ApplicationFiled: January 23, 2013Publication date: June 18, 2015Inventors: Shangwu Chen, Sreeraman Venkitasubrahmanian
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Publication number: 20060097666Abstract: A striation correction circuit 300 is arranged to apply a first striation correction current to the first fluorescent lamp L1 and a second striation correction current to the second fluorescent lamp L2. A first voltage appearing across the first fluorescent tube L1 due to the first striation correction current is substantially similar in magnitude but has inverted polarity with respect to a second voltage across the second fluorescent tube L2 due to the second striation correction current. Detection of an end-of-life condition of a fluorescent lamp is facilitated.Type: ApplicationFiled: November 18, 2003Publication date: May 11, 2006Applicant: Koninklijke Philips Electronics N.V.Inventors: Sreeraman Venkitasubrahmanian, Ramakrishnan Venkatraman, Amr Ghazala
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Patent number: 6628091Abstract: The present invention provides electronic switching for a bi-level fluorescent lamp fixture that allows power to be switched on and off to a group of lamps in a fixture when more or less illumination is needed in an area. The power can be switched without the need to power down the fixture when switching from high level with all lamps illuminated to a low level with only part of the lamps illuminated. The lamp current or frequency can be adjusted to save power when only part of the lamps are illuminated.Type: GrantFiled: May 29, 2001Date of Patent: September 30, 2003Assignee: Koninklijke Philips Electronics N.V.Inventors: John Griffin, Romel Panlilio, Sreeraman Venkitasubrahmanian
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Publication number: 20020180378Abstract: The present invention provides electronic switching for a bi-level fluorescent lamp fixture that allows power to be switched on and off to a group of lamps in a fixture when more or less illumination is needed in an area. The power can be switched without the need to power down the fixture when switching from high level with all lamps illuminated to a low level with only part of the lamps illuminated. The lamp current or frequency can be adjusted to save power when only part of the lamps are illuminated.Type: ApplicationFiled: May 29, 2001Publication date: December 5, 2002Inventors: John Griffin, Romel Panlilio, Sreeraman Venkitasubrahmanian
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Patent number: 6356027Abstract: A 0-10V dimming interface protection circuit generating an indication that line voltage is applied across first and second leads of the dimming interface controlling light output by a lamp, includes a first device for limiting current serially connected between a line voltage source and the first lead of the dimming interface, a second device connected across the first and second leads for detecting application of line voltage to the dimming interface and for generating a control signal, and a third device for switching, operated in response to the control signal, for causing an increase in resistance of the first device to thereby limit current to the dimmer interface and limit light output by the lamp. According to one aspect of the invention, the protection circuit also includes a fourth device for preventing spurious operation of the second device.Type: GrantFiled: May 7, 1999Date of Patent: March 12, 2002Assignee: Philips Electronics North America CorporationInventors: Michael Y. Zhang, Adan Hernandez, Sreeraman Venkitasubrahmanian
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Patent number: 6100647Abstract: An electronic ballast for an electron discharge lamp includes a resonant inverter driven by a high frequency switching signal supplied by a drive circuit which is substantially comprised in an integrated circuit, the lamp being connected in an output circuit of the inverter and powered thereby. The lamp intensity is controlled by changing the switching signal frequency, thereby changing the power supplied to the lamp. In order to prevent parasitic capacitance of remote wiring between the ballast and the lamp from causing inaccuracies in determination of the power being supplied to the lamp, the ballast takes into account the phase difference between lamp current and voltage in making such determination. For example, by deriving the product of rectified lamp voltage and rectified lamp current, and using the arithmetic summation of such products during each operating cycle as a measure of lamp power.Type: GrantFiled: December 28, 1998Date of Patent: August 8, 2000Assignee: Philips Electronics North America Corp.Inventors: Demetri J. Giannopoulos, Ihor T. Wacyk, Sreeraman Venkitasubrahmanian
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Patent number: 5872429Abstract: A communication method particularly suited for lighting control employs encoding of perturbations in a voltage signal having a fundamental period with a nominal waveform. A control period includes a pre-selected number of fundamental periods of the voltage signal. Different control commands are indicated by imposing a selected perturbation, such as a phase cut, on the nominal waveform with a respective occurrence signature within the control period. The control commands are decoded from the voltage signal by detecting the occurrence signature of the perturbations within each control period. Decoding is accomplished by differentiating the nominal waveform to detect encoded perturbations.Type: GrantFiled: March 25, 1997Date of Patent: February 16, 1999Assignee: Philips Electronics North America CorporationInventors: Yongping Xia, Sreeraman Venkitasubrahmanian, Raj Jayaraman, Thomas Farkas
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Patent number: 5850127Abstract: A dimming ballast lamp includes a lamp, a ballast circuit for converting AC input power to AC output power, a dimming interface circuit for generating a dimming control signal having a voltage level indicative of a selected dimming level of the lamp and a dimming circuit responsive to the dimming control signal for controlling operation of the ballast circuit. A feedback control circuit detects the lamp voltage and produces a feedback control signal in response to the lamp voltage exceeding a perscribed threshold voltage level. The dimming circuit, responsive to the feedback control signal, controls operation of the ballast circuit so as to increase lamp current thereby increasing the dimming level of the lamp, ensuring low temperature ignition of the lamp and protecting against lamp shutdown.Type: GrantFiled: May 10, 1996Date of Patent: December 15, 1998Assignee: Philips Electronics North America CorporationInventors: Joshua Zhu, Sreeraman Venkitasubrahmanian
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Patent number: 5808422Abstract: A ballast for a gas discharge lamp includes a detection circuit which detects an operating state of the lamp in which the lamp current for the column discharge of one polarity is different from the lamp current for the column discharge of the other polarity by detecting the DC component of the voltage across the discharge lamp. The detection circuit includes (i) a device coupled such that a DC voltage is imposed there across when the lamp current is different for the column discharge according to one polarity verses the other polarity, and (ii) a sensing circuit for sensing the DC voltage across the device. The device may be a capacitive device, and in a particularly inexpensive implementation, is a DC blocking capacitor or a ballast capacitor. The sense circuit senses when the DC voltage across the device exceeds a threshold value, which may corresponds to fully-rectified state of the lamp or more favorably, to a lesser state of imbalance.Type: GrantFiled: May 10, 1996Date of Patent: September 15, 1998Assignee: Philips Electronics North AmericaInventors: Sreeraman Venkitasubrahmanian, Clint Mason, Yongping Xia, Feng-Kang Hu, Jaap Schlejen
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Patent number: 5751115Abstract: A ballast includes safety circuitry which senses lamp status through various phases of ballast operation. According to one feature, the ballast is prevented from supplying an output voltage upon initial energization of the ballast when a lamp is not present at the output terminals. The presence of a filament is sensed via a DC path extending through the filament heater windings of an output transformer. When the DC path is not complete, a control input, for example the power supply input of the ballast controller, is not provided with a voltage to start ballast operation. The DC path is also used to restart the ballast if a defective lamp is replaced with a good one. Over-voltage and capacitive mode detection is also disclosed to shut down ballast output upon lamp failure/removal.Type: GrantFiled: December 3, 1996Date of Patent: May 12, 1998Assignee: Philips Electronics North America CorporationInventors: Raj Jayaraman, Yongping Xia, Sreeraman Venkitasubrahmanian, Paul Leyton
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Patent number: 5691605Abstract: A lamp controller includes an interface circuit, or receiver, which receives an input signal and decodes control signals supplied from a transmitting device, such as a power line wall controller, according to at least two of the following communication techniques: phase angle control, step control, and coded control. The receiver tests the input signal and identifies which type of control technique is employed by the wall controller connected to the lamp controller. The receiver then decodes the control command from the input signal. In a disclosed embodiment, the lamp controller is gas discharge lamp dimming ballast having a two wire input for connection to the hot dimmed and neutral leads of the power line controller. The ballast has an improved topology in which a pre-conditioner supplies a substantially constant DC voltage to a ballast stage including an inverter, a resonant tank output and a control circuit.Type: GrantFiled: August 9, 1995Date of Patent: November 25, 1997Assignee: Philips Electronics North AmericaInventors: Yongping Xia, Joshua Zhu, Sreeraman Venkitasubrahmanian, Raj Jayaraman, Thomas Farkas
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Patent number: 5650694Abstract: A ballast includes safety circuitry which senses lamp status through various phases of ballast operation. According to one feature, the ballast is prevented from supplying an output voltage upon initial energization of the ballast when a lamp is not present at the output terminals. The presence of a filament is sensed via a DC path extending through the filament heater windings of an output transformer. When the DC path is not complete, a control input, for example the power supply input of the ballast controller, is not provided with a voltage to start ballast operation. The DC path is also used to restart the ballast if a defective lamp is replaced with a good one. Over-voltage and capacitive mode detection is also disclosed to shut down ballast output upon lamp failure/removal.Type: GrantFiled: March 31, 1995Date of Patent: July 22, 1997Assignee: Philips Electronics North America CorporationInventors: Raj Jayaraman, Yongping Xia, Sreeraman Venkitasubrahmanian, Paul Leyten
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Patent number: 5604411Abstract: A dimming ballast for use with a phase control dimmer, and particularly a triac dimmer, includes an EMI filter selected with a high impedance to avoid excessive voltage and peak currents in the filter due to resonance with the phase controlled AC waveform at low conduction angles, when the load presented by the lamp is low. The EMI filter includes a filter capacitor connected at the output of a rectifier. The ballast also includes circuitry to sense the rectified DC voltage and to discharge the filter capacitor when the rectified voltage is at or near zero, to thereby keep the EMI filter loaded and prevent misfiring of the triac dimmer. In a favorable embodiment, the sensing and discharge function is carried out by a pre-conditioner of the switched-mode type.Type: GrantFiled: March 31, 1995Date of Patent: February 18, 1997Assignee: Philips Electronics North America CorporationInventors: Sreeraman Venkitasubrahmanian, Gert W. Bruning, Paul Veldman, Thomas Farkas, Raj Jayaraman, Yongping Xia
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Patent number: 5559395Abstract: A gas discharge lamp dimming ballast has a two wire input for connection to the hot dimmed and neutral leads of a phase control dimmer. The ballast has an improved topology in which a pre-conditioner supplies a substantially constant DC voltage to a ballast stage including an inverter, a resonant tank output and a control circuit. A dimming interface circuit derives a dimming signal having a voltage equal to the average value of the rectified output voltage of a full-bridge rectifier feeding the pre-conditioner circuit. The dim signal is independent of the DC rail voltage and, in combination with the maintenance of a substantially constant DC rail voltage, permits of improved dimming control while providing the ease of installation of a two wire ballast. The response time of the interface circuit relative to the pre-conditioner is selected to avoid power imbalances.Type: GrantFiled: March 31, 1995Date of Patent: September 24, 1996Assignee: Philips Electronics North America CorporationInventors: Sreeraman Venkitasubrahmanian, Thomas Farkas, Raj Jayaraman, Yongping Xia
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Patent number: 5519313Abstract: A temperature-compensated voltage regulator includes a field effect transistor voltage buffer which receives a high-voltage input and provides a low-voltage output, and a voltage generator having a series connection of a zener diode and at least one p-n junction diode for generating a reference voltage. The voltage generator is coupled between the low-voltage output of the voltage buffer and the input of a current mirror, with the output of the current mirror being coupled to the gate electrode of the field effect transistor in the voltage buffer. Additionally, the output of the current mirror is coupled to the low-voltage output of the voltage buffer by a resistor. The resulting voltage regulator circuit features high performance in a simple, economical configuration.Type: GrantFiled: April 6, 1993Date of Patent: May 21, 1996Assignee: North American Philips CorporationInventors: Stephen L. Wong, Sreeraman Venkitasubrahmanian