6377 results about "Feedback circuits" patented technology

An electrosurgical system can include an electrosurgical generator, a feedback circuit or controller, and an electrosurgical tool. The feedback circuit can provide an electrosurgery endpoint by determining the phase end point of a tissue to be treated. The electrosurgical system can include more than one electrosurgical tool for different electrosurgical operations and can include a variety of user interface features and audio/visual performance indicators. The electrosurgical system can also power conventional bipolar electrosurgical tools and direct current surgical appliances.

An LDO voltage regulator includes an error amplifier having a first input coupled to a first reference voltage, a second input receiving a feedback signal, and an output producing a first control signal. An output transistor has a gate, a drain coupled to an unregulated input voltage, and a source coupled to produce a regulated output voltage on an output conductor. A feedback circuit is coupled between the output conductor and a second reference voltage. An overvoltage comparator has a first input coupled to receive the first reference voltage and a second input coupled to respond to the feedback signal to produce a discharge control signal indicating occurrence of an output overvoltage of at least a predetermined magnitude to control a discharge transistor coupled between the output conductor and the second reference voltage. An output current sensing circuit produces a control current representative of the drain current of the output transistor. An offset capacitor is coupled between the output of the error amplifier and the gate of the output transistor, and a servo amplifier has a first input coupled to receive a third reference voltage, a second input coupled to the output of the error amplifier, and an output coupled to the gate of the output transistor to produce a second control signal thereon. A current sensor circuit, a current capacitor, and an AND circuit operate to allow the discharge transistor to be turned on only if the output current is below a certain level.

The switching frequency of an LLC converter is controlled by a control unit to which a feedback circuit provides a first current dependent upon the output voltage of the converter. An oscillator circuit produces a sawtooth waveform at a frequency dependent upon the first current, up to a limit equal to a second current set by a resistor. Two complementary switch control signals are produced for controlling two switches of the converter for conduction in alternate cycles of the sawtooth waveform. A timer produces dead times between the two complementary switch control signals in dependence upon the second current. Another resistor provides a current constituting a minimum value of the first current, and a charging current of a capacitor in series with a resistor modifies the first current for soft starting of the converter.

Line load compensation and reflection reduction in a signal transmitting circuit is provided using feedback capacitors. The feedback capacitor serially coupled with a resistance generates an RC rise/fall time that is independent of the line load. Additionally, by selecting a capacitor that yields a rise/fall time of approximately ⅓ of the maximum bit transmission time, signal reflection on the signal line can be reduced. Accordingly, by incorporating the feedback capacitor with a differential drive circuit, such as the IB 485 driver, variations in line load can be compensated for while also reducing signal reflection due to un-terminated or improperly terminated signal lines, thus allowing a free topology implementation.

A feedback compensation detector for a direct conversion transmitter includes a baseband processor, a direct up-converter, an antenna, and an impairment detection and compensation feedback circuit. The baseband processor generates an in-phase (I) baseband signal and a quadrature-phase (Q) baseband signal. The direct up-converter is coupled to the baseband processor, and combines the I and Q baseband signals with an RF carrier signal to generate an RF output signal. The antenna is coupled to the direct up-converter, and transmits the RF output signal. The impairment detection and compensation feedback circuit is coupled to the RF output signal and the I and Q baseband signals. The impairment detection and compensation feedback circuit down-converts the RF output signal to generate an intermediate frequency (IF) signal, measures as least one signal impairment in the IF signal, and pre-distorts the I and Q baseband signals to compensate for the measured signal impairment.

An output voltage amplifier, and a driving device of a liquid crystal display using the same are disclosed. The output voltage amplifier includes: an amplifying unit to generate first and second signals corresponding to a gray voltage input to a first input terminal and a feedback signal input to a second input terminal, and to output a first voltage by using first and second switches driven to be on or off according to the first and second signals; an output unit to apply the first and second data signals to the first and second pixels by using third and fourth switches turned on or off according to the first and second signals; and a feedback circuit unit to selectively supply one of the first voltage and the first and second data signals to the second input terminal. Heating characteristics and a slew rate can be improved.

A power supply system comprises a low-speed power supply and a high-speed power supply configured to operate in first and second frequency ranges, respectively, and generate first and second outputs, respectively. The lower end of the second frequency range is at least higher than a lower end of the first frequency range. A frequency blocking power combiner circuit combines the power from the first output with the power from the second output to generate a combined, third output for driving a load, while providing frequency-selective isolation between the first and second outputs. A feedback circuit is coupled to receive the combined, third output through a global feedback loop. The feedback circuit generates first and second power supply control signals for controlling the low-speed power supply and the high-speed power supply, respectively, based on a difference between the third output and the predetermined control signal.

A transmitter system for wireless communication with implanted medical devices includes a transmitter circuit having a resonant network the resonant frequency of which is adjusted by a feedback circuit in order to minimize the current drain from the power source and maximizing the power source life. The transmitter system may be powered by a power supply block which uses commonly available RS-232 signals of a host computer as a raw power source, combined with a high value storage capacitor to provide power for the wireless medical data programmer. A feedback circuit monitors the charging current as well as voltage impressed across the storage capacitor in order to maintain the charging current at maximum level during the charging time and in order to stop the charging once the full charge of the storage capacitor has been reached.

Techniques for reliably and efficiently generating an output voltage for use within an electronic device, such as a memory system, are disclosed. A voltage generation circuit generates the output voltage. The voltage generation circuit includes regulation circuitry that controls regulation of the output voltage to maintain the output voltage at a substantially constant level. According to one aspect, regulation is provided through use of different feedback circuits. By selectively disabling one of the feedback circuits, power consumption can be reduced and the other of the feedback circuits can support the continued regulation of the output voltage. The voltage generation circuit is therefore able to operate in an accurate, stable and power efficient manner.

A power conversion circuit senses an output voltage to detect shorted lamp conditions in a backlight system. The power conversion circuit can drive at least one fluorescent lamp. A voltage sensing feedback circuit, such as a capacitive voltage divider or a resistive voltage divider, senses the output voltage at an output of the power conversion circuit and generates a voltage feedback signal for a shorted lamp detector. The shorted lamp detector reliably detects a shorted lamp condition of one fluorescent lamp in a multi-lamp configuration or detects a short circuit condition of the output voltage line coupling the output voltage of the power conversion circuit to the fluorescent lamps.

Embodiments of the present invention relate to a low voltage differential signal driver (LVDS) circuit which comprises a current source, logic controlled switches for controlling the driver's output, an electronic load circuit coupled across the circuit, and a common-mode resistor feedback circuit coupled across the circuit, in parallel with the RC load, for tuning the driver's impedance. The driver is enabled to operate without op-amps and achieves optimum performance at 1.8 v supply voltages.

A switching voltage regulator achieves high efficiency by automatically switching between a pulse frequency modulation (PFM) mode and a pulse-width modulation (PWM) mode. Switching between the modes of voltage regulation is accomplished by monitoring the output voltage and the output current, wherein the regulator operates in PFM mode at small output currents and in PWM mode at moderate to large output currents. PFM mode maintains a constant output voltage by forcing the switching device to skip cycles when the output voltage exceeds its nominal value. In PWM mode, a PWM signal having a variable duty cycle controls the switching device. A constant output voltage is maintained by feedback circuitry which alters the duty cycle of the PWM signal according to fluctuations in the output voltage.

A capacitive load driving circuit which includes an operational amplifier, a pulse width modulator, a digital power amplifier, a first filter, a first feedback circuit and a second feedback circuit. The operational amplifier outputs a differential signal between a signal fed back to the inverting input terminal and an input signal inputted to the non-inverting input terminal. The pulse width modulator pulse width-modulates output from the operational amplifier and outputs a digital signal. The digital power amplifier amplifies power of the digital signal. The first filter smooths output of the digital power amplifier and inputs the smoothed signal to the capacitive load as the driving signal. The first feedback circuit feeds back the driving signal outputted from the first filter to the inverting input terminal of the operational amplifier. The second feedback circuit feeds back a signal outputted from the digital power amplifier, which signal includes a phase which is advanced relative to the driving signal, to the inverting input terminal of the operational amplifier.

System and method for improving efficiency in driving LEDs. A preferred embodiment comprises a switch current regulator coupled to a current control signal input, the switch current regulator to control an amount of current provided to the LED based upon a magnitude of a voltage on the current control signal input, a switching voltage regulator coupled to the switch current regulator and the LED, the switching voltage regulator to provide current to the LED, and a sensor coupled to the switch current regulator, the LED, and a signal feedback circuit, the sensor to measure status information regarding the switch current regulator and the LED and provides the information to a controller, wherein the status information can be used to adjust the current on the current control signal input.