High-impedance level-shifting amplifier capable of handling input signals with a voltage magnitude that exceeds a supply voltage
Granted: March 31, 2009
Patent Number:
7511572
A level-shifting amplifier is provided for level-shifting an input signal with a voltage magnitude that exceeds a supply voltage of the amplifier. In operation, the amplifier has an input impedance of greater than 100 MOhms.
Method and apparatus for overshoot and undershoot errors correction in analog low dropout regulators
Granted: March 10, 2009
Patent Number:
7502719
The present invention provides a method and apparatus for dynamically correcting overshoot and undershoot errors in an analog integrated circuit by improving the reaction time (?t) of the analog integrated circuit. Equivalently, an error correction circuit is disclosed including an overshoot correction circuit and an undershoot correction circuit that are only activated to reduce overshoot and undershoot errors by increasing the bandwidth of the integrated circuit when either undershoot…
Class D audio amplifier with PWM and feedback
Granted: November 25, 2008
Patent Number:
7456685
The present invention introduces methods and systems to amplify digital audio signals for driving speakers. First, digital audio signals are converted to PWM audio signals by a liner PWM modulator that is open-loop. Then, PWM audio signals are amplified by a Class D audio amplifier that has at least one feedback loop.
Method and apparatus for controlling a discharge lamp in a backlighted display
Granted: October 28, 2008
Patent Number:
7443107
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…
Method of 1-bit hysteretic control in N-bit A/D conversion
Granted: October 28, 2008
Patent Number:
7443330
The present invention introduces methods to eliminate 1-bit jitter problem in the N-bit A/D conversion applications. The methods do not require any increase in the total bit of A/D conversion.
Current balancing technique with magnetic integration for fluorescent lamps
Granted: October 21, 2008
Patent Number:
7439685
Methods and apparatus are disclosed for balancing currents passing through multiple parallel circuit branches and in some cases through parallel fluorescent lamps. Single transformers with multiple-leg magnetic cores are wound in specific manners that simplify current balancing. Conventional three-legged EE-type magnetic cores, with disclosed windings are used to balance current in circuits with three or more parallel branches, such as parallel connected Cold Cathode Fluorescent Lamps…
Constant-peak-current minimum-off-time pulse frequency modulator for switching regulators
Granted: October 21, 2008
Patent Number:
7439720
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…
Lamp voltage feedback system and method for open lamp protection and shorted lamp protection
Granted: September 9, 2008
Patent Number:
7423384
A circuit comprises a detector circuit and a protection triggering circuit in a discharge lamp system. The detector circuit detects both open lamp and shorted lamp conditions and is coupled with detecting devices, such as sensing capacitors. A DC bias is added to the sensing capacitors so that capacitor voltages are always greater than zero volts. The output voltage of the detector circuit is coupled to the protection triggering circuit, which triggers an open lamp protection when open…
Fixed lamp frequency synchronization with the resonant tank for discharge lamps
Granted: September 9, 2008
Patent Number:
7423388
Control methods and apparatus are disclosed for operating a full-bridge inverter at resonant frequency mode, hybrid frequency mode, and fixed frequency mode. The operating frequency of the inverter equals to the user programmed frequency if the user programmed frequency is above the resonant tank frequency; and the operating frequency is synchronized with the resonant tank frequency if the user programmed frequency is below the resonant tank frequency.
Linear charger where the material temperature directly affects the circuit thermal control
Granted: September 2, 2008
Patent Number:
7420792
Methods and apparatus are disclosed for protecting circuits from damages caused by elevated temperatures. Presented embodiments illustrate IC thermal protection circuits that shut down power delivery circuits when the circuit temperature reaches a predefined upper threshold and restart the circuit when the circuit cools down to a predefined lower threshold. Other embodiments provide soft shutdown and soft restart, where not only the temperature range between the shutdown and the restart…
Hybrid control for discharge lamps
Granted: September 2, 2008
Patent Number:
7420829
Control methods and apparatus are disclosed for operating an inverter at resonant mode, where the inverter adapts its frequency to the resonant tank characteristics before a lamp is struck, and operates at fixed frequency after the lamp is struck. Disclosed embodiments combine the advantages of operation in fixed mode as well as the variable mode.
System and method for open lamp protection
Granted: September 2, 2008
Patent Number:
7420337
A method for responding to an open lamp condition in a discharge lamp system is disclosed. The method monitors a current feedback signal flowing through a lamp and a voltage feedback signal indicative of a voltage across said lamp. A switch is used to switch between the current feedback signal to the voltage feedback signal upon detection of an open lamp condition.
Method for high efficiency audio amplifier
Granted: August 26, 2008
Patent Number:
7417503
The present invention introduces methods and circuits to amplify audio signals for driving speakers. An additional feedback circuit is added in an audio amplifier to couple the amplifier stage and output stage of the audio amplifier. The feedback circuit turned off as long as output voltages of the audio amplifier are not near saturation. The feedback circuit is turned on to reduce audible noises if output voltages of the audio amplifier are near saturation.
Method and system for open lamp protection
Granted: July 1, 2008
Patent Number:
7394203
A detector circuit monitors the phase relationship between the lamp voltage and the excitation voltage, and if one or more conditions are met, triggers the open lamp protection process in a discharge lamp system. The detection circuit can be incorporated into a lamp voltage feedback circuit and implemented on the integrated circuit level with less cost and circuit complexity.
High-impedance level-shifting amplifier capable of handling input signals with a voltage magnitude that exceeds a supply voltage
Granted: June 10, 2008
Patent Number:
7385446
A level-shifting amplifier is provided for level-shifting an input signal with a voltage magnitude that exceeds a supply voltage of the amplifier. In operation, the amplifier has an input impedance of greater than 100M Ohms.
Method for starting a discharge lamp using high energy initial pulse
Granted: April 8, 2008
Patent Number:
7355354
The described DC to AC inverter efficiently controls the amount of electrical power used to drive a cold cathode fluorescent lamp (CCFL). Additionally, during striking of the CCFL, a higher energy initial energy pulse is used. During normal operation, a lower energy pulse is used.
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,…
