Patents Assigned to Supertex, Inc.
  • Patent number: 7453307
    Abstract: A process independent voltage controlled logarithmic attenuator has an attenuator control stage block having a first input coupled to a controlled input and a second input coupled to an offset generator. An attenuator transistor is coupled to the attenuator controlled stage block. An output of the attenuator controlled stage block is both slope and maximum voltage definable for a process independent design.
    Type: Grant
    Filed: February 23, 2005
    Date of Patent: November 18, 2008
    Assignee: Supertex, Inc.
    Inventors: Wilson Wai-Sum Chan, Hau-Yiu Tsui, Ka-Wai Ho, Isacc Terasuth Ko
  • Publication number: 20080242987
    Abstract: A method of transducer excitation in medical ultrasound imaging. Based on a stepped approximation of Gaussian modulated cosines, the transmit waveform provides bandlimited spectrum and low level of second order harmonics while retaining the duration of the transmitting within two carrier cycles. The waveform is constructed as a linear composition of four unipolar, rectangle pulses of unity amplitude. Furthermore, the described embodiment supports digitally controlled transmit apodization and focusing.
    Type: Application
    Filed: March 21, 2008
    Publication date: October 2, 2008
    Applicant: Supertex, Inc.
    Inventor: Lazar A. Shifrin
  • Patent number: 7417483
    Abstract: A regulated cascode current source has a current source circuit. A level shifter circuit is coupled to the current source circuit. The level shifter circuit has a circuit for independently controlling a voltage on a cascode node.
    Type: Grant
    Filed: June 13, 2006
    Date of Patent: August 26, 2008
    Assignee: Supertex, Inc.
    Inventors: Chi Chun Wong, Terasuth Ko
  • Patent number: 7362253
    Abstract: A Digital to Analog (D/A) converter has a plurality of stages. Each of the plurality of stages has a first resistive element. A second resistive element is coupled to the first resistive element and has approximately twice a resistive value of the first resistive element. A capacitor is coupled to the second resistive element. A switching circuit is coupled to the capacitor. A summing integrator is coupled to each of the plurality of stages.
    Type: Grant
    Filed: September 11, 2006
    Date of Patent: April 22, 2008
    Assignee: Supertex, Inc.
    Inventor: Terasuth Ko
  • Patent number: 7336122
    Abstract: A low power high side current monitor has an input terminal and a load terminal. A current sensing element is coupled to the input terminal and the load terminal. A first resistor is coupled to the input terminal. A first pair of transistors is coupled together and to the first resistor. A second pair of transistors is coupled together and to the first pair of transistors. A third pair of transistors is coupled together and to the second pair of transistors. At least one diode is coupled to the second pair of transistors and the third pair of transistors. A transistor has a first terminal coupled to the third pair of transistors and a second terminal coupled to the second pair of transistors. A second resistor is coupled to a third terminal of the transistor and to ground.
    Type: Grant
    Filed: December 6, 2005
    Date of Patent: February 26, 2008
    Assignee: Supertex, Inc.
    Inventors: Isaac Terasuth Ko, Iris Ho
  • Patent number: 7330364
    Abstract: A method and circuit for converting high voltage AC to low voltage DC using a switched power supply and rising edge conduction has an alternating current (AC) power source. A rectifier is coupled to the AC power source. A switching device is coupled to the rectifier. The switching device is opened and closed only during rising edge conduction. Control circuitry is coupled to the switching device for opening and closing of the switching device only during rising edge conduction. A storage capacitive element is coupled to the switching device.
    Type: Grant
    Filed: October 20, 2004
    Date of Patent: February 12, 2008
    Assignee: Supertex, Inc.
    Inventor: Scott Lynch
  • Patent number: 6992509
    Abstract: A switched-capacitor sample/hold circuit and method having reduced slew-rate and settling time requirements provides for lower-cost and/or lower-power implementation of sample/hold circuits and/or reduced error due to amplifier characteristics. The switched-capacitor sample/hold circuit incorporates a pair of capacitors that are alternatively and mutually-exclusively switched between an input sample position and an amplifier hold position, providing a dual sampled amplifier output signal that has reduced transitions at each sample interval. An alternative embodiment of the sample/hold circuit incorporates a fully-differential amplifier having a differential input and a differential output. Four capacitors are employed forming two of the dual sampled switched-capacitor circuits, one in each negative feedback path (inverted output to non-inverting input, non-inverted output to inverting input) of the amplifier.
    Type: Grant
    Filed: October 2, 2003
    Date of Patent: January 31, 2006
    Assignee: Supertex, Inc.
    Inventors: Terasuth Ko, Chi Chun Wong
  • Patent number: 6958920
    Abstract: A switching power converter and method of controlling an output voltage thereof using predictive sensing of magnetic flux provides a low-cost switching power converter via primary-side control using a primary-side winding. An integrator generates a voltage that represents flux within a magnetic element by integrating a primary-side winding voltage. A detection circuit detects the end of a half-cycle of post-conduction resonance that occurs in the power magnetic element subsequent to zero energy level in the power magnetic element. The integrator voltage is stored at the end of the half-cycle and is used to determine a sampling point prior to or equal to the start of post-conduction resonance in a subsequent switching cycle of the power converter. The primary-side winding voltage is then sampled at the sampling point, providing an indication of the output voltage of the power converter by which the output voltage of the converter can be controlled.
    Type: Grant
    Filed: May 4, 2004
    Date of Patent: October 25, 2005
    Assignee: Supertex, Inc.
    Inventors: Alexander Mednik, David Chalmers Schie, James Hung Nguyen, Wei Gu
  • Patent number: 6940733
    Abstract: A switch state controller generating a pulse train is used in a power converter utilizing a plurality of converter stages all simultaneously controlled by a single switch controlled by said pulse train. On time of the pulse train is controlled according to an input or interim node characteristic of the supply and period is controlled by a characteristic of the output of the converter. This allows development of AC-to-DC converters, including power-factor-correction converters, and DC to DC converters with high conversion ratio with minimal parts count & high reliability.
    Type: Grant
    Filed: August 22, 2003
    Date of Patent: September 6, 2005
    Assignee: Supertex, Inc.
    Inventors: David Chalmers Schie, Alexander Mednik, James Hung Nguyen, Sang Ton Ngo, Khai Minh Le, Wei Gu, Larry Kerenyi
  • Patent number: 6917504
    Abstract: An apparatus and method for adaptively controlling power supplied to a hot-pluggable subsystem controls the inrush current of the hot-pluggable subsystem when the subsystem is coupled to another system that supplies power, and optionally other signal connections. The apparatus and method adaptively control a pass device by detecting the voltage at the gate of the pass device during initial charging of the gate. The gate voltage may be sampled and used subsequently to control the operation of the pass device, and short-circuit conditions may be detected by determining that the miller effect does not change the charging of the gate capacitance. Automatic restart circuitry can be included to generate multiple startup attempts, and under-voltage lockout circuitry and power-on-reset timers can be used to provide a robust solution. The apparatus and method can be adapted to provide a three terminal device that does not require a feedback connection from a power supply output.
    Type: Grant
    Filed: May 2, 2001
    Date of Patent: July 12, 2005
    Assignee: Supertex, Inc.
    Inventors: James Hung Nguyen, Sang Ton Ngo, David Chalmers Schia, Ladislas G. Kerenyi, Khai Minh Le
  • Patent number: 6841950
    Abstract: A method for dimmable control of a multiple output EL lamp driver is disclosed. The multiple output EL lamp driver has a power converter. A plurality of EL lamps are provided wherein one terminal of each EL lamp is coupled to a single common terminal. A plurality of half bridge circuits are provided wherein each circuit has an output impedance. One half bridge circuit is coupled to the single common terminal and each remaining terminal of each EL lamp is coupled to a separate individual half bridge circuit. A logic circuit is coupled to each of the half bridge. An oscillator is coupled to the logic circuit. The method comprises: minimizing the output impedance of the half bridge circuit coupled to the single common terminal to prevent to brightness crosstalk between EL lamps; selecting output impedances of remaining half bridge circuits to produce rounded waveforms across terminals of the EL lamps; and manipulating a drive waveform of one of the plurality of EL lamps to control brightness.
    Type: Grant
    Filed: October 2, 2003
    Date of Patent: January 11, 2005
    Assignee: Supertex, Inc.
    Inventor: James T. Walker
  • Patent number: 6781351
    Abstract: AC/DC cascaded power converters having high DC conversion ratio and improved AC line harmonics provide low input harmonic currents, high power factor and efficient operation for low voltage DC outputs when coupled directly to a source of unfiltered rectified AC voltage. The power converter incorporates an intermediate storage element that provides most or all of the energy storage capacitance within the power converter and a blocking device that enables continuous energy transfer from AC line to output to achieve unity power factor and regulated output while maintaining low AC input current ripple.
    Type: Grant
    Filed: October 28, 2002
    Date of Patent: August 24, 2004
    Assignee: Supertex Inc.
    Inventors: Alexander Mednik, David Chalmers Schie, Wei Gu
  • Patent number: 6710773
    Abstract: A inductorless method and apparatus for driving electroluminescent (EL) panels enables fabrication of an integrated circuit that provides a complete EL panel driver solution in one package. The high voltage required to drive the EL panel is generated by a plurality of charge pump circuits. A multi-stage charge pump may be used to provide a high voltage power supply that does not require an external capacitor to store energy for the power supply.
    Type: Grant
    Filed: August 2, 2001
    Date of Patent: March 23, 2004
    Assignee: Supertex, Inc.
    Inventors: James Michael Oliver Jenkins, Jimes Lei
  • Patent number: 6667583
    Abstract: A method an apparatus for efficiently driving a low-voltage device from a wide-range input supply uses and inductor and a diode coupled in parallel to provide a high-efficiency energy storage circuit. The parallel diode/inductor circuit is coupled to a switch for intermittently supplying a current to maintain a level of energy storage in the circuit. The switch is coupled to a control circuit for controlling the switch. The external device be a relay and the inductor may be a coil of the relay. The external device may be one or more LEDs connected in series and the diode may be the series LED circuit. The control circuit may include a fault-tolerant synchronization input for connection to multiple driver circuits, whereby audible noise produced by beat frequencies between the relays is eliminated.
    Type: Grant
    Filed: May 7, 2002
    Date of Patent: December 23, 2003
    Assignee: Supertex, Inc.
    Inventor: Ladislas G. Kerenyi
  • Patent number: 6555967
    Abstract: A low noise method and apparatus for driving electroluminescent (EL) panels provides reduction in EL panel noise, and in the preferred embodiment, voltage compensation as the EL panel ages. The output of a high voltage power supply is applied to the EL panel through a circuit having an optimized time-constant, producing a waveform that reduces EL panel vibration. Additionally, if the time constant is derived in part from the capacitance of the EL panel, the time constant may be chosen such that aging of the EL panel maintains the time constant in the proper range to maintain noise reduction over the life of the panel and compensate for brightness reduction due to aging of the EL panel.
    Type: Grant
    Filed: September 19, 2001
    Date of Patent: April 29, 2003
    Assignee: Supertex, Inc.
    Inventors: Scott Lynch, Jimes Lei, Roshanak Aflatouni
  • Patent number: 6525515
    Abstract: A feedback apparatus and method for adaptively controlling power supplied to a hot-pluggable subsystem controls the inrush current of the hot-pluggable subsystem upon application of power. The apparatus and method adaptively control a pass device by detecting the current through the pass device during initial charging of a load capacitance and scaling back the turn-on rate at the pass device control terminal input in conformity with the detected current and a predetermined rate set by a ramp generator. A ramp capacitor is coupled to the control terminal of the pass device through a diode to permit use of the capacitor for timing purposes as well as preventing transient turn-on of the pass device during initial application of power.
    Type: Grant
    Filed: September 24, 2001
    Date of Patent: February 25, 2003
    Assignee: Supertex, Inc.
    Inventors: Sang Ton Ngo, James Hung Nguyen, David Chalmera Schie, Ladislas G. Kerenyi, Khai Minh Le
  • Patent number: 6304461
    Abstract: A dc power converter having bipolar output and bi-directional reactive current transfer is disclosed. The dc power converter comprises: a direct current source; a modulator coupled to the direct current source, the modulator comprising at least two switch means for generating a waveform pulse; a transformer primary winding capacitively coupled to the modulator; at least two transformer secondary windings magnetically coupled to the transformer primary winding; and two synchronous rectifiers coupled to a first and second secondary winding respectively of the at least two transformer secondary windings. The first and second synchronous rectifiers each comprise: a switching means for interrupting a current path connected in series with a respective secondary winding first polarity pole, and a capacitor coupled in series with the switching means.
    Type: Grant
    Filed: June 15, 2000
    Date of Patent: October 16, 2001
    Assignee: Supertex, Inc.
    Inventor: James T. Walker
  • Patent number: 6169391
    Abstract: A device which rectifies and regulates high voltage alternating current without the use of transformers, large capacitive coupling circuits or high voltage linear regulators. The device includes a rectifier, a control circuit for sensing the output voltage of the rectifier and switching on and off the input power, a storage capacitor and a low voltage linear regulator. The control circuit, which incorporates a voltage sensing circuit and a switch, limits the output voltage of the rectifier as seen by the linear regulator.
    Type: Grant
    Filed: July 12, 1999
    Date of Patent: January 2, 2001
    Assignee: Supertex, Inc.
    Inventor: Jimes Lei
  • Patent number: 6087863
    Abstract: A method for improving the efficiency of H-bridge electrical switching devices that drive a capacitive load such as electroluminescent lamps, liquid crystal devices and piezoelectric transducers. The method provides for discharge steps that first discharge the capacitive load to a difference in voltage potential of zero (0) volts before re-charging from the opposite side. By implementing the method, the DC power supply will only be required to charge the capacitive load from zero (0) volts to +Vcs volts, rather than +Vcs volts to -Vcs volts as in prior art. With less energy required from the DC power supply to accomplish the same result, a more efficient switching network is achieved.
    Type: Grant
    Filed: March 16, 1998
    Date of Patent: July 11, 2000
    Assignee: Supertex, Inc.
    Inventor: Roshanak Aflatouni
  • Patent number: 5815383
    Abstract: The present invention relates to a switchmode power supply (SMPS) high voltage start-up integrated circuit (IC) with output voltage sensing and output current limiting. The high voltage start-up IC allows low voltage pulse width modulated (PWM) controller ICs to operate directly off rectified AC lines of up to 450 VDC. The high voltage start-up IC allows PWM controller ICs to start-up with a start threshold larger than its operating voltage. The output voltage is monitored internally so that the internal high voltage switch turns off when the output voltage decreases below an internally set trip point voltage (V.sub.off) The internal high voltage switch remains off and an external auxiliary voltage is generated and applied to the output voltage. If the output voltage falls below a lower set trip point voltage (V.sub.reset) the internal high voltage switch turns back on. This allows the start-up circuit to reset itself when the PWM controller IC's auxiliary voltage does not power up properly.
    Type: Grant
    Filed: December 27, 1996
    Date of Patent: September 29, 1998
    Assignee: Supertex, Inc.
    Inventor: Jimes Lei