Method and apparatus for single-ended conversion of DC to AC power for driving discharge lamps
Granted: February 26, 2008
Patent Number:
7336038
The present disclosure introduces a simple method and apparatus for converting DC power to AC power, and, specifically, to single-ended inverter circuits for driving discharge lamps such as a Cold Cathode Fluorescent Lamp (CCFL) or an External Electrode Fluorescent Lamp (EEFL). Among other advantages, these circuits offer nearly symmetrical voltage waveform to drive discharge lamps when the duty cycle is close to 50%. They also eliminate the high current and high voltage resonant…
Minimizing bond wire power losses in integrated circuit full bridge CCFL drivers
Granted: January 29, 2008
Patent Number:
7323829
A technique is described that reduces parasitic losses in circuits used to drive current through a load. An example of a system according to the technique includes four switches in series with five pins such that one pin is connected to ground. An example of an apparatus according to the technique may include four switches in series with two switches connected to ground and to a load and two switches connected to a power source. An example of a method according to the technique involves…
Method and apparatus for driving discharge lamps in a floating configuration
Granted: December 4, 2007
Patent Number:
7304441
A technique is described that facilitates sensing current through a load. A method according to the technique includes mounting a discharge lamp in a floating point configuration, sensing current through the discharge lamp, and controlling current through the discharge lamp to improve power conversion efficiency. A device constructed according to the technique may include two AC voltage sources that are out-of-phase with respect to one another. A current sense circuit may be coupled…
Fixed operating frequency inverter for cold cathode fluorescent lamp having strike frequency adjusted by voltage to current phase relationship
Granted: November 13, 2007
Patent Number:
7294974
A method of driving a lamp that uses a DC to AC inverter that is connected to a primary winding of a transformer is disclosed. The inverter frequency is variable, and in one embodiment, may be controlled by a voltage controlled oscillator. Circuitry is included that monitors the phase relationship between a voltage across a secondary of the transformer and a current through the primary of the transformer. The circuitry monitors the phase relationship and adjusts the inverter frequency,…
Matrix inverter for driving multiple discharge lamps
Granted: November 6, 2007
Patent Number:
7291991
Methods and apparatus are disclosed for converting DC power to AC and for driving multiple discharge lamps and, more particularly, Cold Cathode Fluorescent Lamps (CCFLs), External Electrode Fluorescent Lamps (EEFLs), and Flat Fluorescent Lamps (FFLs). Disclosed methods, among other advantages, allow accurate current sharing among the lamps, minimization of the total number of power switches, and, in general, simplification of the complexity of the control system.
Methods and protection schemes for driving discharge lamps in large panel applications
Granted: September 4, 2007
Patent Number:
7265497
The present disclosure introduces a simple method and apparatus for converting DC power to AC power for driving discharge lamps such as a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL), or a flat fluorescent lamp (FFL). Among other advantages, the invention allows the proper protection under short circuit conditions for applications where the normal lamp current is greater than safe current limit.
Isolated gate driver circuit for power switching devices
Granted: June 26, 2007
Patent Number:
7236041
Embodiments of isolated gate driver circuits are disclosed for driving high- and low-side switching devices for half- and full-bridge power converter topology. Disclosed circuits provide sufficient dead-time, operate over a wide range of duty cycles, and require a single power supply (Vcc). Typical applications for such circuits include cold cathode fluorescent lamp (CCFL) inverters that are powered by a high voltage DC rail.
Active damping control for a switch mode power supply
Granted: June 12, 2007
Patent Number:
7230838
Methods and apparatus are disclosed for suppressing circuit noise due to parasitic elements in switch mode power supplies. The presented embodiments use actively controlled damping devices such as controllable resistors, current sources, and tri-state power devices to achieve required damping and to minimize power loss.
Soft start system and method for switching regulator
Granted: April 24, 2007
Patent Number:
7208927
The present invention introduces methods and circuits to provide a soft start for a switching regulator. A feedback voltage from output terminal is monitored and used to regulate the bias current of the regulator's error amplifier. The present invention also enables a smooth transition from the soft start to normal operation.
Method and apparatus for driving an external electrode fluorescent lamp
Granted: January 16, 2007
Patent Number:
7164240
A technique for driving one or more EEFLs, having first and second ends, in a bank of EEFLs involves driving the EEFLs at both the first and second ends. In a non-limiting embodiment a device constructed according to the technique includes a bank of EEFLs connected in parallel. The device further includes a first transformer, wherein a secondary winding of the first transformer is coupled to the first end of the bank of EEFLs. The device further includes a second transformer, wherein a…
Method and apparatus for single-ended conversion of DC to AC power for driving discharge lamps
Granted: January 9, 2007
Patent Number:
7161305
The present disclosure introduces a simple method and apparatus for converting DC power to AC power, and, specifically, to single-ended inverter circuits for driving discharge lamps such as a Cold Cathode Fluorescent Lamp (CCFL) or an External Electrode Fluorescent Lamp (EEFL). Among other advantages, these circuits offer nearly symmetrical voltage waveform to drive discharge lamps when the duty cycle is close to 50%. They also eliminate the high current and high voltage resonant…
Constant-peak-current minimum-off-time pulse frequency modulator for switching regulators
Granted: October 3, 2006
Patent Number:
7116089
Methods and apparatus are disclosed for controlling switching regulators to automatically switch from a traditional pulse-width modulation (PWM) mode, when the load current is higher than a predetermined value, to a pulse-frequency modulation (PFM) mode, when the load current drops to a point lower than the predetermine value. Switching modes increases the efficiency of the regulator when the load current is low without provoking a large output voltage transient. In some embodiments, a…
Method and apparatus for self-oscillating differential feedback class-D amplifier
Granted: May 16, 2006
Patent Number:
7046727
The present disclosure introduces a simple method and apparatus for a Class-D amplification and Pulse Width Modulation (PWM) of an input signal, such as a voice signal. The proposed circuits do not require reference input signals such as triangular signals; rather, the combination of the circuits' self-oscillating device arrangements and the delay elements performs pulse width modulation at higher frequencies while producing less noise. Among other advantages, these circuits offer…
Voltage regulator using a transimpedance block to measure output
Granted: December 20, 2005
Patent Number:
6977825
A method of controlling the output voltage of a voltage regulator that uses a transimpedance block is disclosed. The method comprises measuring the voltage representative current of the output and comparing the voltage representative current to a reference current. Finally, the charging process is stopped if the voltage representative current of the secondary winding is substantially the same as the reference current.
Fixed operating frequency inverter for cold cathode fluorescent lamp having strike frequency adjusted by voltage to current phase relationship
Granted: July 19, 2005
Patent Number:
6919694
A method of driving a lamp that uses a DC to AC inverter that is connected to a primary winding of a transformer is disclosed. The inverter frequency is variable, and in one embodiment, may be controlled by a voltage controlled oscillator. Circuitry is included that monitors the phase relationship between a voltage across a secondary of the transformer and a current through the primary of the transformer. The circuitry monitors the phase relationship and adjusts the inverter frequency,…
Method for starting a discharge lamp using high energy initial pulse
Granted: May 31, 2005
Patent Number:
6900600
The described DC to AC inverter efficiently controls the amount of electrical power used to drive a cold cathode fluorescent lamp (CCFL). The inverter uses a full bridge that is controlled to deliver energy to the CCFL using pulse width modulation (PWM). Additionally, during striking of the CCFL, a wider initial energy pulse is used. During normal operation, a lower energy pulse is used.
Integrated circuit driver having stable bootstrap power supply
Granted: May 24, 2005
Patent Number:
6897643
An integrated circuit driver is disclosed. The driver comprises a high side transistor and a low side transistor connected in series. The output of the driver is taken from the source of the high side transistor and the drain of the low side transistor. A bootstrap contact pad is connected to the output node. Connected to the bootstrap contact pad is a bootstrap capacitor that is also connected to a high side gate drive that selectively controls the high side transistor.
Full wave sense amplifier and discharge lamp inverter incorporating the same
Granted: January 27, 2004
Patent Number:
6683422
A full wave sense amplifier for sensing a periodic current flowing through a discharge lamp is disclosed. The full wave sense amplifier comprises a first circuit for sensing the positive going portion of the periodic current. The amplifier also includes a second circuit for sensing the negative going portion of the periodic current. Finally, an output circuit for combining the negative going portion and the positive going portion into a current flow signal is provided.
Lateral high voltage transistor having spiral field plate and graded concentration doping
Granted: January 20, 2004
Patent Number:
6680515
A lateral high voltage transistor device is disclosed. The transistor includes a gate, a drain, and a source. The drain is located apart from the gate to form an intermediate drift region. The drift region has variable dopant concentration between the drain and the gate. In addition, a spiral resistor is placed over the drift region and is connected to the drain and either the gate or the source of the transistor.
Method and apparatus for controlling a discharge lamp in a backlighted display
Granted: October 14, 2003
Patent Number:
6633138
The described DC to AC inverter efficiently controls the amount of electrical power used to drive a cold cathode fluorescent lamp (CCFL). The output is a fairly pure sine wave which is proportional to an input control voltage. The output waveform purity is ensured by driving a symmetrical rectangular waveform into a second-order, low pass filter at the resonant frequency of the filter for all conditions of line voltage and delivered power. Operating stress on the step-up transformer is…
