Abstract: A plurality of semiconductor die, which may be of diverse size and diverse junction pattern, are fixed to a common lead frame and within a common package The semiconductor die are mounted on respective main pad areas that are laterally spaced from one another and which have respective heat sinks The heat sinks extend from the boundary of the device package and form external pins that are available for external connection at the same or at different potentials Isolated pins are also provided The device package may be used for high and low side chopper circuits, synchronous regulator circuits, single-mode bridges, and the like

Abstract: A low-noise CMOS instrumentation amplifier for low-frequency thermoelectric infrared sensor applications is described which uses a chopper technique to reduce low-frequency noise and offset. The offset reduction efficiency of the band-pass filter, implemented to reduce residual offset due to clock feedthrough, has been analyzed and experimentally verified. The circuit has been integrated in a transistor-only 1-/spl mu/m single-poly n-well CMOS process. It features a gain of 52 dB with a 500 Hz bandwidth and a common-mode rejection ratio (CMRR) of more than 70 dB. The equivalent input low frequency noise is 15 nV//spl radic/Hz. The typical residual input offset is 1.5 /spl mu/V. The amplifier power consumption is 1.3 mW.

Abstract: An amplifier is disclosed including at least three integrator stages connected to provide a low-frequency path from a signal input to a signal output, and a relatively high-frequency bypass path around the first integrator stage. The first integrator stage uses dynamic offset reduction such as chopper stabilization, and an analog low-pass filter reduces artifacts of the dynamic offset reduction. The paths converge at a current summing node. To prevent instability when the integrators are saturated by large signals, the paths have respective saturation current limits selected so that the relatively high-frequency path is not saturated when the low-frequency path saturates. To ensure that the conditional stability is substantially unaffected by adjustment of closed-loop gain, a current feedback input adjusts the open-loop gain in a fashion inversely proportional to resistance presented to the current feedback input by a feedback circuit.

Abstract: MOSFETs and insulated gate bipolar transistor (IGBT) devices are increasingly used in electronic circuits due to both their easy driving and ability to handle high currents and voltages at high-switching frequencies. This paper deals with a new driver technique that allows optimization of the switching speed, reduction of the energy losses during the switching time, and limitation of the electromagnetic interference (EMI). First, an analysis of voltage- and current-switching waveforms of gate-insulated devices is performed. Then, a method of controlling voltage and current slopes independently is shown using the "one-cycle" method or a suitable adaptive-driving technique based on a phase-locked loop (PLL) approach. These techniques were adopted in order to allow correct generation of the gate signals regardless of the operating conditions. Finally, practical results of the proposed driving circuit obtained using a single IGBT switch chopper are presented.

Abstract: A fuzzy adaptive model following mechanism for the position control of a traveling-wave-type ultrasonic motor (USM) is described in this study. Since the dynamic characteristics of the USM are difficult to obtain and the motor parameters are time varying, fuzzy adaptive control is applied to design the position controller of the USM for high-performance applications. The driving circuit for the USM, which is composed of a high-frequency boost DC-DC chopper, a two-phase series-loaded resonant inverter and an inner speed loop, is built first. Next, the control algorithm for fuzzy adaptive control is discussed. Then, a simple linear position control loop is designed and augmented by the model-following error-driven fuzzy adaptive mechanism to reduce the influence of parameter variations. The effectiveness of the proposed controller is demonstrated by some experimental results.

Abstract: A new type of multi-chopper for cutting strands or ribbon shaped material such as strands of glass fibers, and a method of using this chopper, is disclosed. The chopper has at least two chopper assemblies on a rotating frame. When one chopper assembly needs repair, the frame is rotated which brings a rebuilt or repaired chopper assembly into operating position quickly and also brings the assembly needing repair into a position where it can be worked on while the other chopper is operating resulting in much reduced downtime. The frame of the chopper can rotate around a vertical or horizontal line, or around a line passing through two opposite corners of a frame.

Abstract: This paper presents a technique for single phase power factor correction of nonlinear loads employing an active power filter. The current control strategy is the same used in the boost pre-regulator, which is the average current mode technique. The paper focuses on the design methodology and the analysis of the control strategy which allows the compensation of harmonics and phase displacement of the input current, for single and multiple nonlinear and linear loads. Simulation results of an active filter controlling a single load, which consists of a 1600 W rectifier with a capacitive filter, and a multiple load, which consists of a 800 W rectifier with a capacitive filter and a 800 W AC chopper, are provided. Experimental results of an active filter controlling a 400 W rectifier with a capacitive filter, a 800 W AC chopper and a 580 W multiple load, which consists of a rectifier with a capacitive filter and an AC chopper, are presented.

Abstract: A quarterfold folding device and method forms groupings of signatures in a signature product stream by delaying selected signatures during transport to a chopper mechanism, the chopper mechanism adapted to fold multiple signatures in a single chop, thereby increasing throughput of the quarterfold folding device and reducing the rate of operation of the chopper mechanism.

Abstract: A CMOS chopper opamp has been realized. The low-pass filter, which is necessary to remove modulated offset and noise components, is implemented as a sample-and-hold filter, which has the advantages of not limiting the band width and easy integration. The opamp features an offset of 30 µV, noise of 300nV/√Hz, 120dB gain and 75 µW power consumption. The opamp has better trade-offs for offset, noise, chip area and power consumption than traditional auto-zeroed opamps.

Abstract: A system of class B choppers equalizes the DC voltages of the back-to-back multilevel converters of the UPFC thus removing the constraint that the voltages of the series and the shunt converter must operate at a fixed ratio. This allows the UPFC to operate with independent controls over the real power and the reactive powers on both sides. The claims are substantiated by digital simulations and laboratory experiments.

Abstract: A multi-stage down chopper for arc welding by creating current flow between an electrode and a workpiece, the chopper includes a D.C. input source, a first switching stage, with a first switch device and a first choke, this first stage selectively connects the D.C. input source across the electrode and workpiece at a controlled duty cycle and switching rate and a second switching stage, with a second switch device and a second choke, the second stage also selectively connects the D.C. input source across the electrode and workpiece at the aforesaid controlled duty cycle and switching rate, wherein the chopper is improved by the first and second chokes onto a single core and by providing a minimum current override feedback circuit.

Abstract: This invention is a fiber-based multi-color pyrometry set-up for real-time non-contact temperature and emissivity measurement. The system includes a single optical fiber to collect radiation emitted by a target, a reflective rotating chopper to split the collected radiation into two or more paths while modulating the radiation for lock-in amplification (i.e., phase-sensitive detection), at least two detectors possibly of different spectral bandwidths with or without filters to limit the wavelength regions detected and optics to direct and focus the radiation onto the sensitive areas of the detectors. A computer algorithm is used to calculate the true temperature and emissivity of a target based on blackbody calibrations. The system components are enclosed in a light-tight housing, with provision for the fiber to extend outside to collect the radiation. Radiation emitted by the target is transmitted through the fiber to the reflective chopper, which either allows the radiation to pass straight through or reflects the radiation into one or more separate paths. Each path includes a detector with or without filters and corresponding optics to direct and focus the radiation onto the active area of the detector. The signals are recovered using lock-in amplification. Calibration formulas for the signals obtained using a blackbody of known temperature are used to compute the true temperature and emissivity of the target. The temperature range of the pyrometer system is determined by the spectral characteristics of the optical components.

Abstract: A motor drive apparatus and an air-conditioner using the motor control apparatus has a feature which allows it to gradually increase a dc voltage value to a predetermined value when starting the switching operation of a chopper circuit by dc voltage control thereof, and when stopping the switching operation of the chopper circuit to be able to gradually decrease the dc voltage value to a predetermined value. Further, the dc voltage command value is adjusted so as to make it possible to maintain a preferred value of dc voltage. Thereby, fluctuation in the number of revolutions of the motor can be prevented even if the converter is started or stopped while the motor is operating, thereby allowing the motor drive apparatus and air-conditioner using the motor control apparatus of the invention to be operated at their maximum capacities.

Abstract: A low-offset integrated circuit useful for the readout of the signal coming from various types of integrated resistive bridge sensors has been developed in standard bipolar technology. The circuit, using a first order /spl Sigma/-/spl Delta/ A/D converter, provides a clock-synchronous pulse rate output which is highly suitable for the communication with a microprocessor and for a bus environment. An almost perfect offset cancellation is achieved by chopping the bridge voltage supply. The simplicity of the circuit makes it ideal for the integration with the sensors itself, while the digital interference rejection allows the integration of the digital control circuits for the bus on the same chip. The experimental results show that with a clock frequency of 200 kHz a resolution of 12 bits is obtained with a conversion time of 20 ms. The remaining offset is /spl plusmn/5 /spl mu/V. The bridge imbalance can be up to 18 mV/V. Depending on the chosen resolution the input signal bandwidth could be from about 25 Hz (12 bits) up to 400 Hz (8 bits).

Abstract: In a switching power supply a stable dc output voltage having a higher power factor is obtained even for an unstable ac input voltage using a sufficiently broadened duty ratio of the switching signal. The switching power supply include a rectifying circuit 10 for full-wave rectifying an ac input voltage to output a pulsating current, a chopper circuit having a switching device Q1 driven at a sufficiently higher frequency than that of the ac input voltage, an inductor L1 connected in series with the switching device Q1 between output terminals of the rectifying circuit 10, and a capacitor C1 for smoothing a current fed through the inductor L1 to supply a stabilized dc output voltage, an error amplifier 11 and a multiplier 12 for providing a threshold level signal having a full-wave rectified waveform, in which the phase thereof is the same as that of the ac input voltage, and an amplitude corresponding to an error voltage included in an output voltage of the chopper circuit, a comparator 13 for comparing the current of the switching device Q1 with the threshold level signal, and a monostable multivibrator 20 for driving the switching device Q1 according to the output signal of the comparator 13. The turn off time of Q1 becomes shorter when the immediately preceding turn on time becomes longer.

Abstract: A non-row-sensitive forage harvesting header for attachment to a mobile frame carrying a chopper has a pair of rotatable cutting discs for severing stalks as the frame moves across a field. Positioned above the cutting discs are a pair of drum-shaped transfer devices rotatable in opposite directions about upright axes coaxial with the rotational axes of the respective cutting discs for gathering severed stalks to a central location between the devices. A pair of endless gripping elements extend about respective ones of the transfer devices and present opposed rearwardly moveable runs extending between the central location and the chopper when the header is attached to the frame. The opposed runs of the gripping elements are operable to cooperatively grip each gathered stalk therebetween while moving the stalk rearwardly from the central location to the chopper. The header may be provided with rotatable auger cylinders positioned adjacent opposite sides of the chopper inlet when the header is attached to the mobile frame, with each cylinder having flighting for directing crop material downwardly toward the chopper inlet.

Abstract: This paper describes a newly developed high-efficiency uninterruptible power supply (UPS) having an active filtering ability which is composed of a three arm bridge. The developed single-phase UPS, of rating 3 kW and 100, V has the following three abilities: (1) in normal operation, the UPS works as an active filter by using two arms and not only eliminates harmful harmonics created by nonlinear loads, but can also realize high efficiency; (2) the three-arm bridge converter/inverter can compensate any change in input supply voltage acting like a voltage regulator; and (3) at the power-off state, one arm works its a chopper to maintain constant DC link voltage and other two arms work as a bridge inverter. As a result, the developed UPS is achieved with an input power factor of 99% and an efficiency of over 95% in active filter operation and also a output voltage distortion of under 2% in converter/inverter operation.

Abstract: An improved chopper stabilized operational amplifier is disclosed, along with an improved method of timing the switchings of chopper switches in such an amplifier. The disclosure includes an integrated circuit and method for generating a true random voltage signal having a truly random RMS voltage value within a selected range. The true random voltage signal is obtained by amplifying and bandpass filtering random white noise voltages generated by a component of the circuit. The white noise voltages include shot noise voltages generated by bipolar transistors in an input amplifier stage. The random signal generator circuit and method is employed with an oscillator to form a random clock signal generator on the integrated circuit chip. The amount of time between each clocking pulse output by the random clock signal generator truly randomly varies within a selected range of time, and repeats only by random chance. The random clock signal generator is used to control the amount of time between each switching of a chopper switch in a chopper-stabilized operational amplifier, so that the chopping frequency is truly random. The truly random variation of the chopper switching frequency reduces interference due to aliasing of noise typically created by such switches.

Abstract: In this paper, an improved circuit of AC choppers for single-phase systems are proposed and investigated. This new circuit employs a DC chopper modulated switch with a diode bridge rectifier and two switches to provide a freewheeling path for the load current when the modulated switch is off. The attractive feature of this improved circuit is that it uses only a single modulated switch. The improved circuit has many advantages compared with the conventional AC choppers such as simple design requirements, easy implementation, higher power capacity, fast dynamic response, high reliability, high power factor, low cost, low switching loss and consequently high efficiency. By digital simulation several characteristics are investigated.

Abstract: Device for controlling an inductive charge, particularly, of an electromagnetic coil, comprising a chopper switch in series with the coil and governed by a pulse width modulator, and an opening switch which is also mounted in series with the coil. A transfomer converter (20) has two secondary windings, of which one is connected to the modulator (11) and the other one is connected to the grid of the opening transistor (T2) via a switch (25) biased by the opening signal.

Abstract: A multilevel chopper has been proposed as a suitable topology for high voltage application. In this paper, the optimal design of the multilevel inverter for UPS application is presented. A simulation-optimization system is used to perform the optimal design. This system is a combination of an optimization tool and a simulation program. The simulation program is with knowledge of the sequences of operation and is used to perform an accurate computation of the power inverter characteristics. The optimization tool however is used as a powerful procedure for the resolution of the design problem formulated in terms of objective function and constraints. The optimal design results of the multilevel inverter are verified by an experimental prototype.

Abstract: PROBLEM TO BE SOLVED: To eliminate a chopper to reduce size, weight and cost of a system apparatus and make an inverter input voltage variable to improve a system efficiency. SOLUTION: One side ends of the windings of an AC motor 103 are connected to the AC output side of a voltage-type inverter 101 which receives a DC voltage and outputs a variable AC voltage with a variable frequency and the other side ends of the windings of the AC motor are connected to each other together to form a neutral. A variable voltage type energy storage device 105 is connected between the neutral and one of the DC input terminals of the inverter 101 and an automotive DC power supply 106 is connected between both the ends of the energy storage device 105. Further, the inverter 101 is made to practise a chopper operation by switching operation of a zero-voltage mode of the inverter 101 and a power is delivered between the variable voltage type energy storage device 105 and the DC input side of the inverter 101 through the inverter 101.

Abstract: A modification to a commercial FT-Raman spectrometer is presented for the elimination of thermal backgrounds in FT-Raman spectra. The modification involves the use of a mechanical chopper to modulate the CW laser, remote collection of the signal via fiber optics, and connection of a dual-phase digital signal processor lock-in amplifier between the detector and the spectrometer's collection electronics to demodulate and filter the optical signals. The resulting modulated FT-Raman fiber-optic spectrometer is capable of completely eliminating thermal backgrounds at temperatures exceeding 370 C. In addition, the signal/noise of generated Raman spectra is greater than for spectra collected with the conventional FT-Raman under identical conditions and incident laser power. This is true for both room-temperature and hot samples. The method allows collection of data using preexisting spectrometer software. The total cost of the modification (excluding fiber optics) is approximately $3000 and requires less than 2 h to implement. This is the first report of Fr-Raman spectra collected at temperatures in excess of 300 C in the absence of thermal backgrounds.

Abstract: A boost and buck chopper type potential source excitation system for a synchronous type electric power generator which is capable of having an operational characteristic which is better than that of a conventional voltage source excitation system with respect to a rated input voltage and forcing an excitation field by boosting an excitation input voltage using a boost chopper when an excitation input voltage is decreased due to a failure in a cable. The system includes a boost chopper for receiving an output voltage from the buck transformer, converting the thusly received voltage into a direct current voltage, adjusting a level of the same, outputting the same to the thyristor as an excitation voltage, boosting the direct current voltage when the output voltage from the electric power generator is decreased, and outputting the thusly boosted voltage to the thyristor.

Abstract: A beam chopping system for a cyclotron is in operation at the JAERI cyclotron facility. A combination of a pulse voltage chopper in the injection line and a sinusoidal voltage chopper after the exit of the cyclotron is adopted to produce beam pulses spaced at 1 μs–1 ms intervals from natural cyclotron beams. The chopping system was designed according to a simple formulation of the chopping process in which the multiturn extraction was taken into account. Performance of the chopping system was experimentally proved to satisfy requirements of the design. In actual operation to produce beam pulses at long intervals, however, the number of the multiturn extraction is usually larger than the assumed value in the design because of a large phase acceptance of the cyclotron. Careful tuning of the acceleration phase width or the base magnetic field of the cyclotron is necessary to reduce it. It is essential to strictly define the acceleration phase of injected beams in the central region of the cyclotron to improve this situation.

Abstract: Thermal imaging chopper (22) having a frame (42) with an open window (47) and a covered window (48). The covered window (48) is preferably covered with a material that partially blocks a selected amount of thermal radiation from a scene and randomly scatters the remaining thermal radiation from the scene that is transmitted through the covered window. The open window (47) allows unrestricted transmission of thermal radiation from the scene.

Abstract: In a photodetector amplifier scheme, the invention compensates for variations in photodetector quiescent current by sampling the amplifier output and subtracting a controllable current from the input to the amplifier. When a chopper or other modulator is used on the optical signal, the samples are taken periodically during the chopping cycle. This sampled signal is processed by a combination of gain and low pass filtering. The result of this processing controls a current source which subtracts a significant fraction of the average quiescent current from the total detector current. In a typical application, the amplifier is of the resettable current integrator type. In this case, the invention makes it possible to use smaller integration capacitors resulting in larger signals than if the quiescent current were not reduced by the operation of the invention. The gain, frequency response, and range of compensated quiescent currents and can be altered by changing timing signals. Implementation is directed toward using components which take up little area when fabricated as an integrated circuit.

Abstract: PROBLEM TO BE SOLVED: To provide an ignition device for a capacitor discharge type internal combustion engine of a direct current voltage boosting type for igniting even when an output voltage of a direct current power supply part is low. SOLUTION: When a detection signal Vil of a primary electric current of a booster transformer 2 reaches to a cutoff value set signal Vis obtained from a resistance voltage dividing circuit 4b, a switch 3 for chopper is turned off to cut off the primary electric current of the booster transformer. A resistor R30 for adjusting a cutoff value is connected between an output port B3 of a microcomputer 10A and a voltage dividing point of the resistance voltage dividing circuit 4b. When a power supply voltage E0 reaches to a reference value, a voltage equal to the power supply voltage E0 is outputted from the output port B3 and the cutoff value set signal Vis is switched to a high value. When the power supply voltage E0 does not reach to the reference value, an output of a voltage from the output port B3 stops and the cutoff value set signal Vis is switched to a low value.