Showing papers on "Integrating ADC published in 1996"

Three-pin buck and four-pin boost converter having open loop output voltage control

Abstract: A controlled output voltage is provided for a switching mode power converter operating in the continuous conduction mode without requiring a feedback path coupled to monitor the output voltage. Instead, a voltage related to the input voltage is monitored. The monitored voltage is compared to a periodic waveform for forming a switch control signal. In the case of a buck converter operating as a voltage regulator, over each period of the periodic waveform, the periodic waveform is representative of the inverse function. In the case of a boost converter operating as a voltage regulator or buck converter operating as a bus terminator or power amplifier, over each period of the periodic waveform, the periodic waveform has a linear slope. The switch control signal controls a duty cycle of the power switches. Therefore, switching is controlled in an open loop, rather than in a closed loop. By monitoring a voltage related to the input voltage, rather than the output voltage, an integrated circuit for controlling the buck converter or boost converter requires few pins and can sink or source current.

Soft switching DC-to-DC converter with coupled inductors

Abstract: A DC-to-DC converter topology is provided having switching devices that are switched under zero voltage switching conditions to minimize switching losses. The converter of the present invention includes two input side converter bridges, each based on a two switch forward converter topology. The input side converter bridges may be connected in series for high input voltage levels and in parallel for low voltage levels. The switching devices of each input side converter bridge are coupled together by coupling inductors. The turning-off of a switching device in one bridge causes part of the energy stored in the corresponding coupled inductor to discharge an output capacitance of an incoming switching device in the other bridge, causing an anti-parallel connected diode to conduct. The incoming switch can thus be turned on under zero voltage switching conditions. Zero voltage switching can be achieved over a wide load range by properly sizing the coupled inductors. The converter switching devices are preferably provided switching signals from a peak current control controller that controls the duty cycle of the converter to regulate the peak of the output currents to control the output power delivered to a load.

A high-resolution, linear resistance-to-frequency converter

Abstract: A resistance-to-frequency converter consisting of a Wheatstone bridge followed by an integrator and a comparator is described. In concept the circuit represents a relaxation oscillator whose frequency changes linearly with a resistance change detected by the bridge. Analyses show that a resolution better than 0.05% is possible with the simple configuration, and an excellent linearity is maintained over the wide resistance change by using a simple compensation method. The converter is therefore suited as a signal conditioner of a resistive sensor. Experimental results are included to demonstrate its performance.

Switched-capacitor-based DC-to-DC converter with improved input current waveform

Abstract: A new type of DC-to-DC converter is proposed by using dual basic quasi-switched-capacitor (QSC) converter cells. The prominent feature of this converter is its improved input current waveform, which can reduce the electromagnetic interference due to the conducted emissions as compared to the classical PWM-type and SC-based converters. The concept of energy transfer is realized by two symmetrical converter cells, operating in two cyclical phases. The d.c. voltage conversion ratio is determined by the voltage applied to the quasi-switch in each cell for controlling the charging trajectory of the capacitors in order to maintain a constant output voltage for a wide range of load and supply voltage. As the converter does not contain any inductive element, it makes the converter of small size, light weight, high power density and possible in IC form. The small-signal frequency response shows that the designed converter has good operation stability. A prototype of 36 W, 12 V/9 V, step-down DC-to-DC converter has been built, giving an overall efficiency of 73% with power density of 20 W/in/sup 3/.

Programmable gain for delta sigma analog-to-digital converter

Abstract: A programmable gain delta sigma analog-to-digital converter includes an analog input terminal receiving an analog input voltage, a charge summing conductor, an input capacitive switching circuit, and a feedback reference capacitive switching circuit coupled to the charge summing conductor. An integrator is coupled between the charge summing conductor and a comparator which supplies a stream of digital pulses to a digital filter that produces a digital number representing the analog input voltage. The feedback reference capacitive switching circuit includes a plurality of reference sampling capacitors, selectively coupling charge between a feedback reference voltage source and an integrating capacitor of the integration in response to a programmable gain control circuit so as to provide a selected gain for the analog-to-digital converter. The sampling rate of the capacitive switching circuits is adjusted proportionally to the selected gain to improve the dynamic range of the analog-to-digital converter.

Variable-frequency variable-input-voltage converter with minimum frequency limit

Abstract: A variable-input-voltage variable-switching-frequency power converter with a minimum frequency limit. The switching frequency never goes below a certain minimum while the converter is on. Thus switching frequency is dependent on input voltage, for input voltages in one range, and is NOT dependent on input voltage, for input voltages in another range.

Self-compensating switching power converter

Abstract: A self-compensating high voltage switched power converter monitors the variations in real time of the resonant frequency of the converter, and controls a switching transistor of the converter to establish an operating frequency which corresponds to the resonant frequency. The collector voltage of the switching transistor is monitored, and the transistor is switched only when the collector voltage is decreasing toward a minimum value and is below a predetermined reference level. This enables the power converter to operate at a high frequency, which affords small size, light weight, and high efficiency.

Single-stage AC-to-DC full-bridge converter with magnetic amplifiers for input current shaping independent of output voltage regulation

Abstract: An ac-to-dc switching full-bridge converter employing voltage bidirectional switches as controllable series input switches, preferably implemented with magnetic amplifiers, that couple ac rectifiers to a single-stage full-bridge dc-to-dc converter in order to provide unity power factor operation by control of input current using a fast current loop to modulate the duty ratio d1 of the voltage bidirectional amplifier switches while independent output voltage regulation is maintained by voltage feedback to the full-bridge converter switches through modulation of the switch duty ratio d of the converter (where d1

Analog-to digital converter with delta-sigma modulator

Abstract: An analog-to-digital converter according to the present invention comprising a comparator having first and second inputs, and an output, the comparator comparing an analog input voltage at the first input to a tracking voltage at the second input to place a digital output on the comparator output in response thereto, a voltage switching matrix having an input connected to the output of the comparator and an output, an integrator having an input connected to the output of the voltage switching matrix and an output connected to the second input of the comparator to complete a feedback loop and to provide the tracking signal to the second input of the comparator, and a digital filter coupled to the output of the comparator, the digital filter to form a digital output corresponding to the analog input signal at the first input of the comparator.

Optimum dynamic performance of a buck converter

Abstract: The application of optimal control theory concepts justifies the use of a bang-bang control to reach in minimum time a specified reference in steady-state in the case of the buck converter. The derived control function is unique and insensitive to the converter initial conditions. The converter trajectories in the phase-plane are used as control functions and sliding-mode control is introduced to regulate the output voltage.

High-order delta sigma modulator

Abstract: A delta-sigma modulator includes, in one embodiment, cascaded unit-delay integrators, the number of which is selected depending upon the order desired. The modulator further includes an n-bit (or multi-bit) A/D converter coupled to the output of the last cascaded integrator, and an n-bit (or multi-bit) D/A converter coupled to the output of the A/D converter. A truncator also is coupled to the output of the A/D converter. Truncation error correction is performed digitally by a truncation corrector. A one-bit D/A converter provides feedback from the output of the truncator to differential summing junctions interposed at the input of each unit-delay integrator. The multi-bit D/A converter output signal is fed back to differential summing junctions at the input of the third order and higher unit-delay integrators. The multi-bit D/A converter requires no digital correction of its linearity and only unit-delay integrators are used so that N-1 delay free integrators do not all have to settle within one clock period. The modulator therefore utilizes multiple quantizer bits to provide increased converter resolution and is stable at high orders.

Input harmonic current corrected AC-to-DC converter with multiple coupled primary windings

Abstract: An AC-to-DC power converter achieves greater than 80 percent power factor correction with greater than 75 percent efficiency using only one power switch, only one magnetic component, only one control loop, and a storage capacitor. The only magnetic component is a transformer having first primary winding, a second primary winding, and at least one secondary winding. During a first time interval of the period of the AC input current, the second primary winding is energized with energy previously stored in a storage capacitor. During a second time interval of the period of the AC input current, the first primary winding is energized with energy of an input current flowing through the AC input terminals. As a result, the AC-to-DC power converter drawns input current for an extended period of time before the point in time when the input voltage peaks and also for an extended period of time after the point in time when the input voltage peaks. Magnitudes of input current harmonics with respect to the fundamental input current are therefore reduced with an AC-to-DC power converter having only one magnetic component.

Multi-channel D/A converter utilizing a coarse D/A converter and a fine D/A converter

Abstract: A digital to analog (D/A) converter which has good monotonicity and is small in scale of circuitry, wherein a coarse D/A converter is separated from the fine D/A converter, and the output from the coarse D/A converter is added to the output from the fine D/A converter, and wherein the coarse D/A converter converts an upper bit digital input signal to an analog output signal, and the fine D/A converter converts a lower bit digital input signal to an analog output signal, wherein differential pairs are provided having different weighted transconductances based on the lower bit digital input signal, and are controlled to add at the same time the converted analog output signal from the fine D/A converter to the converted analog output signal from the coarse D/A converter, whereby resolution is substantially improved.

Low voltage temperature-to-voltage converter

Abstract: A temperature-to-voltage converter includes a first circuit for developing a signal having a positive temperature coefficient and a second circuit for developing a signal having a voltage offset and a negative temperature coefficient. The converter also includes an adder circuit configured to subtract the negative-temperature-coefficient signal from the positive-temperature-coefficient signal. The resulting difference signal is a low voltage that exhibits linear temperature-to-voltage conversion, allowing the converter to be powered by a low operating voltage.

Compact log-domain current mode integrator with high transconductance-to-bias current ratio

Abstract: A current mode, class AB, MOST log-domain integrator with high transconductance-to-bias current ratio is presented. Large and small time constants are achievable, maintaining a low bias current and low capacitance.

Digital integrator V/Hz relay for generator and transformer over-excitation protection

Abstract: A system for implementing accurate V/Hz value measurement and trip time determination for generator/transformer overexcitation protection independent of the conventional frequency tracking and phasor estimation based on Discrete Fourier Transformation (DFT) techniques. A sampled sinusoidal voltage signal is passed through a digital integrator and the magnitude of the digital integrator's output is measured as representative of the V/Hz ratio. The digital integrator is implemented in software using a difference equation in a generator protection unit. The technique may be used with either a fixed or a variable sampling frequency. When the sampling frequency is variable, the filter coefficients of the digital integrator are recalculated on-line each time the sampling frequency is changed, and a new value for the peak magnitude of the output of the digital integrator is calculated using the recalculated filter coefficients. Non-linear frequency response characteristics of the voltage sensors and non-ideal characteristics of the digital integrator are also adjusted using the measured frequency and error-frequency characteristics of the particular digital integrator and voltage sensors used.

Feed-forward bandpass delta-sigma converter with tunable center frequency

Abstract: Delta sigma modulators for accepting input signals having amplitudes up to -1 dB of full-scale and a center frequency (FS) in the range FS /90, 44F 90!, and which are not prone to internal overflow, require few circuit parameters, and yield a signal transfer function with the inherent property that the modulator magnitude response is close to unity gain in the frequency region of interest include, in one embodiment, a pair of cascaded integrators, a unit delay element coupled to the output of the second integrator, an analog-to-digital (A/D) converter, and a one-bit digital-to-analog (D/A) converter controlled by output signals from the A/D converter. A first differential summing junction coupled to the output of the D/A converter is responsive to delta sigma modulator input signals. A second differential summing junction, coupled to the output of the first differential summing junction, is also coupled to receive a feedback signal from the second integrator. A third differential summing junction, coupled to the output of the unit delay element, also receives feed-forward signals from the second integrator.

Power converter with selectively variable output and controller and display system therefor

Abstract: A system to control the output voltage of a power converter in response to a specific load battery condition. The system contains a power converter, a TCMS interface attached thereto and a controller for selectively and/or adaptably changing the magnitude of converter output voltage. A control module is incorporated in the system to automatically change converter output voltage up or down in response to the load (input) voltage. The module contains a microcontroller to sense the battery (input) voltage process said input voltage with an analog-to-digital converter. The microcontroller is programmed to execute a series of routines to determine the proper charging voltage for the system. Thereafter, the control module communicates this information through the interface of the power converter to cause the power converter to charge at the optimum voltage. In the alternative, a plug-in component containing passive circuitry may be used to manually signal the power converter to charge at a predetermined voltage.

Low cost AC-to-DC converter having input current with reduced harmonics

Abstract: An AC-to-DC power converter draws input current through an inductor. When the input voltage of the converter is sufficiently high and the switch of the converter is on, current flows into the converter, through the inductor, to the tap of a transformer, through a first primary winding of the transformer, and through the switch. When the switch is then turned off, current continues to flow through the inductor and to the tap of the transformer but then flows through a second primary of the transformer and into a storage capacitor. Energy stored in the storage capacitor is transferred to the load when it is not possible to obtain sufficient energy from the input current to supply the load. The AC-to-DC converter has very few circuit components and low input current harmonics.

High-frequency, high-efficiency converter with recirculating energy control for high-density power conversion

Abstract: A front-end converter processes only a fraction (e.g., about 10%) of the power delivered by an efficient output (i.e., the main) converter in order to control the output voltage thereof. Because only a fraction of the delivered power is processed, the losses associated with the front-end converter are a very small fraction of the total delivered power, leading to very high overall efficiencies. The input power to the front-end converter is provided from the output of the main converter; this reduced power is thus circulated within the converter. Regulation of the output voltage by controlling the dc voltage relieves the regulating function from the main converter, allowing the main converter to be selected strictly on the basis of efficiency and small size. The result is an overall efficient, compact dc-to-dc converter with minimal output filter requirements and protection against output short circuits. Additionally, the converter bandwidth is determined by the bandwidth of the low-power front-end converter which can have a higher bandwidth than a full-rated converter. Therefore, a significantly higher bandwidth can be achieved as compared with presently available converters, advantageously resulting in a reduced output filter size and faster speed of response.

Combination shared capacitor integrator and digital-to-analog converter circuit with data dependency cancellation

Abstract: A modulator, in conjunction with a load circuit, is provided The modulator forms part of an A/D converter system The modulator includes a series of switched capacitors connected in a shared capacitor arrangement The shared capacitors receive samples from an input signal and, depending upon the logic value fed into a D/A converter, the shared capacitor further receives a feedback reference voltage The reference voltage is thereby coupled to the switched capacitor network, as well as to a load circuit which cancels data-dependent values modulated upon the reference voltage supply The load circuit thereby serves to eliminate ac components within the reference voltage supply resulting from data dependent loading

Accurate digital-to-analog converter

Abstract: A digital-to-analog converter that includes pairs of positive and negative current sources that are connected through switches to two differential output lines. The switches are controlled as a function of a digital data. Each pair of current sources includes a pair of transistors of an output stage of a transconductance amplifier. The transconductance amplifier receives a reference voltage at a non-inverting input, and receives at an inverting input, the voltage at the middle node of a bridge of resistors that is connected between the two differential out-put lines. The output of the converter is the voltage between the two differential output lines.

VVVF On-line Control of Matrix Converter

Abstract: A matrix converter doesn't have any energy storage components, so it is smaller than a converter-inverter system with same KVA. Though matrix converter requires 18 switching devices instead of 12, each device capacity is 0.383 times and total capacity is 0.575 times that of the converter-inverter system. For the matrix converter, we proposed a firing sequence which eliminated voltage and current spikes in switching operations, and control method I which generated the output voltage of 0.866 times the supply voltage. Moreover, we proposed control method II which improved the waveform distortion of the input current and realized unity input power factor. In this paper, we propose a new VVVF gate circuit based on control method II for matrix converter, which can on-line control input current waveform and output voltage waveform to sinusoidal even if there are fluctuation, asymmetry and/or harmonics in the supply voltage. We also confirm by experiments that the waveform distortion of the input current and the input power factor were greatly improved.

Predictive waveform acquisition

Abstract: A tester exercises a DUT with a repetitive signal pattern, supplying a trigger signal for each repetition. The waveform on a conductor of the DUT is to be acquired by repeatedly measuring voltage at each of a number of sample points following the trigger, using a charged-particle probe system having an integrator-filter loop for analyzing energy of secondary particles. Before measurement at a sample point, integrator is reset and the filter voltage needed to settle the loop for the sample point is set using a predictive scheme. When the measurement is made, the predicted filter voltage is summed with the integrator output voltage to produce the actual filter voltage. The integrator then measures the error between the predicted filter voltage and the actual filter voltage needed to settle the loop. The time needed to settle the loop is thereby minimized. Various predictive schemes can be used. An adaptive predictive scheme uses the error measured by the integrator to update the filter voltage prediction for the next measurement at the same sample point. The predicted filter voltage can be a previous measurement or an average of previous measurements taken at that sample point or an average of previous measurements taken over some time interval or a value determined by any other desired predictive scheme.

Frequency converter device which adaptively responds to a power failure

Abstract: A frequency converter device comprises a first converter 5 in a pulse-width modulation system for converting an AC voltage into a DC voltage; a second converter 2 in a pulse-width modulation system for supplying an AC voltage with a variable voltage and a variable frequency to a motor; a capacitor 15 connected between an output side of said first converter 5 and an input side of said second converter 15; a current suppressing circuit connected to the input side of said first converter 5 and consisting of a resistor 31 and a relay 32; a detection circuit 19 for detecting the presence or absence of the power supply inputted to said first converter 5; a circuit 16 for measuring the voltage across said capacitor 15; a drive control circuit 30a for stopping the conversion of said first converter 5 when power failure of an input power supply occurs and when the voltage across the capacitor is not smaller than a prescribed value, continuing the drive state of the relay 32 and said second converter 2, thereby continuing an output.

Photodetector integrator circuit having a window comparator

Abstract: An improved photodetector integrator circuit is provided having a photodetector, such as a photodiode, which produces photocurrent responsive to incident illumination. The photodetector is coupled to an integrator stage which converts the photocurrent into voltage and integrates the voltage over an integration period to provide an output signal. A window comparator in the circuit receives the output signal from the integrator stage and compares the output signal to a first threshold and a second threshold to provide, as a measurement signal, a pulse having a width which corresponds to the time interval over which the output signal increases from the first threshold to the second threshold. In the window comparator, the second threshold is greater than the first threshold. The integrator stage has two inputs coupled across the photodetector which are biased by a bias voltage below the first threshold, and a switch, preferably a mechanical relay, coupled to the integrator stage which when enabled resets the integrator stage to provide its output signal substantially equalling the bias voltage. A programmed microcontroller may also be provided for controlling the switch to reset the integrator stage, determining the time interval corresponding to the width of the pulse, and measuring the photocurrent produced by the photodetector responsive to the determined time interval. The circuit can be used in an optical analyzing instrument, such as spectrophotometer, to increase accuracy for measuring photocurrents.

Direct current voltage converter with soft switching

Abstract: The invention relates to a direct current voltage converter with soft switching, comprising a transformer (Np, Ns) of which the primary is particularly of the half-bridge mount type and susceptible of being connected to an input voltage source (Ve) through two electronic switches (INT1, INT2) and of which the secondary, of the monoalternating type, is susceptible of being connected to a load through a series inductance (L2) and means (1-3, G1, G2) to alternatingly control the two switches, at fixed frequency, according to a regulation through pulse width modulation as a function of the output voltage (Vo) so as to achieve at the primary a zero voltage switching, said converter being characterized in that said secondary comprises, additionally, a resonant circuit (L1, C1) so as to perform at said secondary a zero current quasi-resonant switching.

Low-voltage CMOS GM-C filter with rail-to-rail common-mode voltage

Abstract: In this paper, a CMOS design of low-voltage 5th-order elliptic low-pass GM-C filter with rail-to-rail common-mode input voltage is introduced. The Operational Transconductance Amplifier (OTA) inside this filter is a low-voltage rail-to-rail voltage-to-current converter (V-I converter). In this V-I converter, an N-type V-I converter cell is connected in parallel with its counterpart, a P-type V-I converter cell, to achieve common-mode rail-to-rail operation. Maximum-current selecting circuits are utilized to generate constant-gm output currents for this OTA. This 5th-order elliptic low-pass GM-C filter operates at a supply voltage of 3 V and has a cutoff frequency of 500 kHz.

A 1.2 V companding current-mode integrator for standard digital CMOS processes

Abstract: A low-voltage current-mode integrator using voltage companding and operating in class AB is presented. The integrator is made only with transistors without any functional capacitors and is therefore suited to the integration in a digital CMOS process. It has been used in a 4th-order Tchebycheff low-pass filter which can be tuned from 20 Hz to 20 kHz and achieves total harmonic distortions smaller than 1% for input currents smaller than 10 times the bias current. The dynamic range is typically 55 dB and the power consumption is 1.16 /spl mu/W for a cut-off frequency of 5 kHz.

Apparatus for programming a voltage within a storage element

Abstract: The present invention is an apparatus for storing a voltage level within a storage element such as an EEPROM. The apparatus includes a track and hold circuit that receives the voltage level to be stored and an integrator that determines a target voltage to be applied to the storage element representative of a voltage level less than the received voltage level. The apparatus further includes a voltage ramp circuit that applies a voltage ramp signal to the storage element for increasing an amount of voltage held in the storage element while simultaneously reading a voltage level of the storage element to determine whether the voltage of the storage element matches the target voltage and a comparator that deactivates the voltage ramp signal when the voltage of the storage element matches the target voltage. The integrator also reads a resulting stored voltage of the storage element, determines a new target voltage, and controls the voltage ramp circuit and the comparator to apply the new target voltage to the storage element a predetermined number of times.