Showing papers on "Pulse-width modulation published in 1978"

Apparatus for and method of programming the minimum energy threshold for pacing pulses to be applied to a patient's heart

Abstract: A method and apparatus is disclosed for programming a threshold mode of operation into a pacing generator whereby the minimum level of energy of the stimulating pulse as generated by the pacing generator is determined. First, the original level of energy of the stimulating pulses is determined when this mode is commenced. The original energy level and in particular the pulse width is decremented by a predetermined incremental amount, and an encoded signal indicative of the new reduced pulse width is transmitted to the pacing generator, whereby the pacing generator applies the pulses of the reduced pulse width to the patient's heart. Further, there is included means for counting the number of pulses of reduced pulse width and after the application of a given number of pulses by the pacing generator to the patient's heart, the programming apparatus programs a new energy level decremented from the previously programmed value to be then transmitted to the pacing generator.

Pulse Interval and Width Modulation for Video Transmission

Abstract: This paper proposes new pulse analog modulation system; Pulse Interval and Width Modulation suitable for light emitting diodes. In this system pulses have information on both their width and interval between them. Pulse Interval and Width Modulation is characterized by the following compared with Pulse Interval Modulation. First: Pulse repetition frequency is reduced by one half. Second: Duty ratio is 50 % on the average. Third: More power is needed while carrier to noise ratio could be improved instead. The paper shows how it works and comparison with another pulse analog modulation such as Pulse Frequency Modulation or Pulse Interval Modulation. The paper also shows an experiment of twin channel transmission employing two light emitting diodes, two optical fiber transmission lines and two PIN photodiodes as an example of application of Pulse Interval and Width Modulation.

Temporal compression of light

Abstract: The 5890 A output from a CW dye laser was converted into a train of 0.5 ns pulses by frequency modulation and passage through a near-resonant atomic vapor delay line of Na. The theory of the process is discussed in both the time and frequency domains. Using a modulation index of 120 at a frequency of 17.8 MHz, we obtained values for the temporal compression ratio and intensity enhancement of 112 and 14, easily the largest that have been reported.

Master-slave voltage regulator employing pulse width modulation

Abstract: A pulse width modulation (PWM) converter circuit for transforming a first DC voltage into a secondvoltage (AC or DC), wherein the magnitude of the second voltage is regulated by the converter circuit. The converter circuit comprises a clock circuit, a master pulse width modulator (PWM) circuit and n slave pulse width modulator (PWM) circuits. The clock circuit provides a symmetrical train of rectangular pulses on each of n+1 conductors, wherein only one pulse occurs on any one of the conductors at one time. The master PWM means is responsive both to the train of pulses on one of the n+1 conductors and to a feedback signal indicative of the magnitude of the second voltage; the master PWM means controls the flow of current, due to the first DC voltage, through a portion of a transformer primary winding. Each of the slave PWM circuits is responsive both to the train of pulses on n of the n+1 conductors, in a one-to-one relationship, and to an output control signal based both upon the feedback signal, indicative of the magnitude of the second voltage, and upon the difference in the magnitude of the charge passed by the master PWM circuit and the charge passed by the respective slave PWM circuits; each of the slave PWM circuits controls the flow of current, due to the first DC voltage, through a portion of the transformer primary winding.

Single line multiplexing system for sensors and actuators

Abstract: A single line refigurable power transmission and signal multiplexing system having a central processor and a plurality of remotely located devices such as sensors, actuators and associated interfaces. Communications between the central processor and the remote devices is accomplished via a single bi-directional transmission line. A negative logic pulse width encoding technique is utilized to facilitate power and signal transmission. Selective activation is accomplished by a pulse width discriminator associated with each interface which employs a two-part recognition test to identify specific pulse width signals.

Pulse width modulated feedback arrangement for illumination control

Abstract: Illumination amplifier devices such as liquid crystal devices (LCDs) are controlled with feedback servo arrangements using pulse modulated signals such as pulse width modulated signals or using proportional analog signals. In a preferred embodiment, illumination is controlled with an LCD, where the controlled illumination is monitored with a electro-optical sensor to generate a feedback signal related to a characteristic of the controlled illumination. The feedback signal is processed with an illumination servo to provide a control signal to the LCD for precisely controlling illumination with the LCD. A pulse modulation circuit provides pulse modulation signals to control the LCD, thereby providing a form of proportional control with signals that provide on-off type characteristics. This arrangement provides more precise control for illumination amplifiers and provides proportional control with the illumination amplifier operating in an on-off manner.

Optimum PWM waveforms of a microprocessor controlled inverter

Abstract: Microprocessors eliminate the need to use PWM techniques which are easily implemented with hardware for inverter control. A search is thus made for an optimum technique regardless of complexity. Several techniques including a new one which minimizes distortion in an RL load are compared analytically and experimentally. A microprocessor-controlled inverter was built to implement these techniques. The new technique is suggested as a possible method of optimal adaptive inverter control.

Class D amplifier system

Abstract: In a Class D amplifier system comprising a pulse width modulator for pulse width modulating with an audio signal a carrier signal having a frequency higher than that of the audio signal, an output switching amplifier connected to the modulator, and a lowpass filter connected to the output amplifier to supply a demodulated audio signal to a load in which a trap circuit resonant at a carrier signal frequency is provided in the lowpass filter to permit part of an output signal from the trap circuit which is free from a carrier signal component to be negative-fed back to the pulse width modulator.

Clock pulse regenerator

Abstract: A clock pulse regenerator is constructed with digital circuits and may be built using large scale integration techniques. An oscillator produces first pulses at a repetition rate higher than that of the incoming digital data signal. A first counter counts the first pulses to produce the regenerated clock pulses. A gate pulse generator is responsive to both the incoming digital data signal and the regenerated clock pulses to generate a gate pulse having a pulse width proportional to a phase difference between the two signals. A third counter counts the number of leading and trailing edges of the incoming digital data signal. The pulse outputs of the second and third counters are supplied to a gate circuit. A fourth counter counts the pulses transmitted by the gate circuit to produce, after a predetermined count, a reset pulse for the first, second, third and fourth counters. The second, third and fourth counters therefore serve as a phase detector. The detection output resets the first counter which generates the clock pulse sequence with the received input.

Digital servo system for rotating member

Abstract: A digital servo system for a rotating member which detects a difference between phases of a reference signal and a signal representing the rotation phase of the rotating member thereby to control its rotation in accordance with the phase difference. Comparison is made by a digital rotation phase comparator between points of time at which first and second predetermined counts are made by a clock pulse counter which is cleared for each period of the reference signal and a point of time at which the rotation phase information signal of the rotating member is produced. When the rotation phase signal appears during an interval between the first and second counts, a latch signal is generated in synchronization with the rotation phase signal to cause an instantaneous count between the first and second counts of the counter to be loaded into a latch circuit. A pulse width modulator generates a pulse train whose width corresponds to the latched count; and the rotation of the rotation member is controlled in accordance with a DC output voltage level of a driving circuit which corresponds to the pulse width of the pulse width modulated signal.

Apparatus for producing pulse width modulated signals

Abstract: A microprocessor based engine control system including an engine control unit for producing a plurality of pulse width modulated output signals of programmable frequency. The pulse width and frequency of each output is contained in a control word provided to the engine control unit. The control word contains a pulse width number and a frequency code. The control unit includes a free-running counter and logic means which switches the output signal to one level when the number of stages of the counter defined by the frequency code are all zero and switches the output signal to a second level when the content of the aforementioned number of counter stages is greater than the pulse width modulated number.

Control circuit for a tone generator

Abstract: A control circuit for a tone generator that is adapted to cause the tone generator to produce a plurality of readily distinguishable audible sounds, including a chime sound, a pulse tone and a steady tone. The control circuit has particular application for use on an automobile to monitor such conditions as "seat belts buckled", "headlamps on", and "key in the ignition". The control circuit includes three oscillator circuits that are adapted to produce square wave output signals at three different frequencies. The chime sound is generated by pulse width modulating the highest frequency signal and "restriking" the decaying sound at the frequency of the lowest frequency oscillator. The steady tone is produced by driving the tone generator directly with the output signal from the highest frequency oscillator. To generate the pulse tone, the highest frequency oscillator is repeatedly enabled and disabled in accordance with the output signal from the middle frequency oscillator. Novel pulse width modulating circuitry for producing the chime sound is also disclosed.

Motor driving circuit

Abstract: PURPOSE: To prevent the variation of gain, etc of motor driving circuit by supplying to motor coil a signal amplified for pulse width modulation means in accordance with signal level detecting the rotation position of rotor CONSTITUTION: The output signal of the rotor rotation position detector 4 is applied to the operational amplifier 10, and then its output signal is put in the comparators 21 and 22 to make pulse width modulation by the output signal of the trianglar wave-generating circuit 23 The sigbal d is inversed by the polarity inversion circuit 24 and then supplied to the transistor 14a of the power amplifying circiut 11, and also the signal e is supplied to the transistor 14b and thereby the transistors 14a and 14b undergo alternate switching operation according to the pulse signals f and e And, the signal e is given through the integrator 25 to the polarity inversion circuits 26a and 26b to drive the transistors 15a and 15b of the power amplifying circuit 12 and thus control current flows in the motor coil 2 through the low-path filter consisting of the inductance 27 and the condenser 28 COPYRIGHT: (C)1979,JPO&Japio

Multi-mode programmable digital cardiac pacemaker

Abstract: A programmable cardiac pacemaker pulse generator utilizing digital circuitry for controlling the provision of cardiac stimulating pulses. The pulse generator is capable of having the rate, the pulse width, the pulse amplitude, the refractory period, the sensitivity and the mode of operation programmed. In addition, the pulse generator can have the output inhibited and can respond to programming signals causing a threshold margin test to be performed, effects of closure of the reed switch overridden, a hysteresis function added and a high rate exceeding the normal upper rate limit programmed. Many of the programmable functions of the pulse generator can either be programmed on a permanent or a temporary basis. The pulse generator further includes means for signaling the acceptance of a programming signal, and means to reset the program acceptance circuit if extraneous signals are detected as programming signals. The program signal acceptance circuit performs several different checks on the detected programming signal including a parity check, an access code check and determining if the proper number of signals were transmitted within a given time. The timing circuit of the pulse generator includes a crystal clock oscillator and counter means for counting the clock pulses therefrom to determine the rate of the pacemaker. The pulse width of each pacemaker pulse is determined by using a voltage controlled oscillator in place of the crystal oscillator to obtain energy compensation due to the battery voltage decreasing with time.

Generation of pulse bursts at 212.8 nm by intracavity modulation of an Nd:YAG laser

Abstract: Bursts of 1064 nm pulses at a repetition rate of 120 kHz were generated by placing a resonant, acoustooptic birefringence modulator inside the cavity of a flash-pumped Nd:YAG laser The resulting pulse trains were converted to 532, 266, and 213 nm by a three-step nonlinear generation process in crystals that permit 90° phase matching for these wavelengths An average power of 26 mW at 213 nm was achieved This method of pulse generation develops much lower peak powers than are obtained with ordinary Q -switching at the same average power, and is therefore useful in applications which require that the power be focused on a small sample without damage Construction of the 120 kHz modulator and details of the nonlinear experiments are presented The phase matching temperature for sum frequency generation of 2128 nm in KDP was found to be -35°C, which is 50°C warmer than the value predicted from refractive index data in the literature

Pulse-Interval Modulation Applicable to Narrowband Transmission

Abstract: Pulse-interval modulation (PIM) is reviewed considering its application to the voice band transmission of still picture signals in industrial TV systems. Although PIM seems to have scarcely been utilized in practice, some advantages as an analog pulse modulation can be expected in the case of narrowband transmission. As to the signal-to-noise ratio and the analog message bandwidth, comparisions with PPM and FM are made, which proves that PIM is suited for the TV signal transmission. The dominant defect of PIM is the matter concerning the errors introduced into the pulse spacing by the mutual interferences of bandlimited pulses. Assuming an ideal filter, the effects of bandlimiting are discussed. The differential gain characteristics, and the interference outputs owing to the unwanted lower sidebands of a pulse train are examined, which indicates the effectiveness of lowpass filtering of post-detection signals.

Transistorized D-C/A-C converter

Abstract: A self-balancing d-c/a-c converter comprises a transformer whose primary winding is split into a pair of symmetrical halves each connected in series with a respective transistor and an associated resistor across a supply of direct current. A differential amplifier, with inputs connected across the two resistors through a pair of low-pass filters, generates an unbalance signal d in the form of a voltage of either polarity which is additively and subtractively superimposed upon a reference voltage e to provide two control signals e+d and e-d fed to respective inputs of two comparators. Two synchronized signal generators produce a sawtooth oscillation a and a square wave f, the latter having a period which is twice that of the former. Sawtooth wave a is fed in parallel to the other inputs of the two comparators while the square wave f and its complement g alternately unblock a pair of AND gates in cascade with these comparators. Two resulting pulse trains h and i, of a pulse width varying with the sign and magnitude of the unbalance signal d, energize the bases of the two transistors in a manner tending to rebalance the current traversing the transformer primary.

Narrow pulse eliminator

Abstract: A circuit for eliminating pulses of a minimum predetermined period including a pulsed current source for charging an integrating capacitor, the potential of which is sensed by a threshold detecting circuit. The connection between the current source and the integrating capacitor is selectively controlled by a pair of complementary field effect transistors responsive to the signal including the narrow pulses. The minimum pulse width is determined by a number of device design parameters as well as an externally applied oscillation frequency.

Programmable digital cardiac pacemaker with means to override effects of reed switch closure

Abstract: A programmable cardiac pacemaker pulse generator utilizing digital circuitry for controlling the provision of cardiac stimulating pulses. The pulse generator is capable of having the rate, the pulse width, the pulse amplitude, the refractory period, the sensitivity and the mode of operation programmed. In addition, the pulse generator can have the output inhibited and can respond to programming signals causing a threshold margin test to be performed, effects of closure of the reed switch overridden, a hysteresis function added and a high rate exceeding the normal upper rate limit programmed. Many of the programmable functions of the pulse generator can either be programmed on a permanent or a temporary basis. The pulse generator further includes means for signaling the acceptance of a programming signal, and means to reset the program acceptance circuit if extraneous signals are detected as programming signals. The program signal acceptance circuit performs several different checks on the detected programming signal including a parity check, an access code check and determining if the proper number of signals were transmitted within a given time. The timing circuit of the pulse generator includes a crystal clock oscillator and counter means for counting the clock pulses therefrom to determine the rate of the pacemaker. The pulse width of each pacemaker pulse is determined by using a voltage controlled oscillator in place of the crystal oscillator to obtain energy compensation due to the battery voltage decreasing with time.

Timing of laser pulses produced by combined passive and active mode-locking

Abstract: The equations of combined active and passive mode-locking are solved approximately in the limit when the saturable absorber determines the width of the pulse, and the active modulator the timing. An equation identical with the Adler equation of oscillator phase locking is obtained for the phase of the pulse with respect to the active modulation. In the case of synchronization between the mode-locked pulse-train and the active modulation (time independent solution), the phase of the pulse with respect to the modulation maximum is determined as a function of detuning and modulation (depth. Beyond a critical detuning of the round-trip time Tn from the modulation period TM, synchronisation ceases and the pulses' slip through ' the active modulation with a phase that has a periodic variation superimposed on the uniform slippage rate. Finally, we investigate the effect of noise on the pulse timing. The spectrum of the pulse phase is the same as the spectrum of the phase of an injection-locked single-mode oscill...

Digital-to-analog converter of the pulse width modulation type

Abstract: A digital-to-analog converter of a pulse width modulation type in which a single counting cycle of a clock pulse counter is divided into 2m elementary periods where m represents a selected number of less significant bits of a digital input data to be converted into analog quantity and elementary pulses in number determined in dependence on the logic values of the more significant bits are distributed among the elementary periods, while supplementary elementary pulses are produced in the elementary periods selected in dependence on the logic values of the less significant bits of the digital input data. These elementary pulses are integrated for every elementary period and the integrated output value is converted into a corresponding DC analog output signal.

Anti-flood circuit for use with an electronic fuel injection system

Abstract: A pulse width computer for a fuel-injected internal combustion engine generates injector actuation control pulses, the widths of which increase with decreasing engine temperature. These actuation control pulses are normally applied to control an injector drive circuit that, in turn, controls the duration of activation of one or more electromagnetically-actuated injectors in synchronization with the engine cycle. During engine cranking operations, the widths of the injector actuation control pulses are also integrated on a capacitor to generate a voltage that is compared with a temperature dependent reference voltage selected to represent an incipient flood condition. When the capacitor voltage is detected as having increased to this reference voltage, the comparator causes an attenuation of the injector actuation control pulse. In one embodiment, the injector actuation control pulse is attenuated by being inhibited for the remainder of the cranking period after which the capacitor is suitably discharged. In another embodiment, the injector actuation control signal is inhibited until the capacitor is discharged at a predetermined rate to a level below the incipient flood level. And, in a third embodiment, the width of the injector actuation control signal is decreased by a one shot pulse the width of which varies with one or more engine parameters.

Hybrid pulse width-pulse rate digital-to-analog converter method and apparatus

Abstract: A digital-to-analog converter method and apparatus is disclosed which utilizes a hybrid technique of combined pulse width and pulse rate modulation to achieve improved performance with reduced logic and circuitry requirements. Lower order bits of an N-bit digital data input for conversion to a corresponding analog output voltage level are treated in a manner similar to pulse rate modulation approaches utilized previously. High order bits are handled together in a variant form of pulse width (duration) modulation in which the pulse width required to generate the given analog voltage level corresponding to the high order digital bit inputs is divided into a fixed number of slices in a given sample time, each slice having a width or duration of pulse output which is variable in itself in correspondence to a function of both the high and low order bit value inputs. A low pass filter or integrator combines all of the pulses in a given sample to produce the analog voltage level output.

Digital cardiac pacemaker with refractory, reversion and sense reset means

Abstract: A programmable cardiac pacemaker pulse generator utilizing digital circuitry for controlling the provision of cardiac stimulating pulses. The pulse generator is capable of having the rate, the pulse width, the pulse amplitude, the refractory period, the sensitivity and the mode of operation programmed. In addition, the pulse generator can have the output inhibited and can respond to programming signals causing a threshold margin test to be performed, effects of closure of the reed switch overridden, a hysteresis function added and a high rate exceeding the normal upper rate limit programmed. Many of the programmable functions of the pulse generator can either be programmed on a permanent or a temporary basis. The pulse generator further includes means for signaling the acceptance of a programming signal, and means to reset the program acceptance circuit if extraneous signals are detected as programming signlas. The program signal acceptance circuit performs several different checks on the detected programming signal including a parity check, an access code check and determining if the proper number of signals were transmitted within a given time. The timing circuit of the pulse generator includes a crystal clock oscillator and counter means for counting the clock pulses therefrom to determine the rate of the pacemaker. The pulse width of each pacemaker pulse is determined by using a voltage controlled oscillator in place of the crystal oscillator to obtain energy compensation due to the battery voltage decreasing with time.

Sine-wave static converter

Abstract: The method and apparatus of converting a sine-wave signal of one frequency to a sine-wave signal of a different frequency comprises a four port pass means that is controlled by at least two control signals. An error signal is generated by the difference between the rectified output signal and a locally generated reference signal. The error signal is compared to a high frequency sawtooth signal to provide a pulse width signal which generates a two state output signal. The first state is when the amplitude of the sawtooth signal is less than the error signal and the second state is when the amplitude of the sawtooth signal is greater than the amplitude of the error signal. The two state pulse width modulated signal is combined with the output from a polarity control means for obtaining the control signals.

Sliding notch pulse width modulation (PWM)

Abstract: The RMS voltage of the output sine wave of a power inverter is regulated by pulse width modulation (PWM) of the rectangular waveform fundamental signal of the inverter bridge with a single sliding notch in each half cycle of the rectangular wave, each notch having a pulse width and position in the wave which is dependent on the required attenuation of the RMS value, and which may be varied, in a continuous manner, between a variable pulse width edge notch, a fixed pulse width notch which slides from an edge notch to a center notch position, and a variable pulse width center notch

Compensation circuit for trailing edge distortion of pulse-width modulated signal

Abstract: When a pulse-width series modulator is connected to the cathode of an RF radio transmitter tube for the purpose of series modulation, filtration of the PWM switching signal is required to eliminate the switching signal from the output modulating signal. Stray capacitive effects in this filtration generate undesirable distortion in the trailing edge of the signal appearing in the last stage of the PWM thereby producing non-linearity in the modulation of the RF output tube. The present disclosure illustrates circuitry for complimentarily modifying the leading edge of the pulses so as to maintain a linear relationship in the time integral of voltage in the output signal. This modification is accomplished through a plurality of capacitive units each having different time constants for charging and discharging.

Automatic failure-resistant radar transmitter

Abstract: Apparatus is shown for controlling pulse width in pulsed, step-wise frequency modulated transmitters employing relatively long pulse widths and receiving pulse compression. Also disclosed is a pulsed pseudo-random coded radar system having fixed code word duration. Individual solid-state, RF power amplifier modules are paralleled, all spares included, and the full parallel group is operated at a power level such that individual units operate substantially below maximum power rating. RF solid-state device life is thereby increased. Failures of individual solid-state modules are recognized by a power monitor which operates to lengthen the pulse width in the FM staircase embodiment and to increase power supply input and, therefore, peak pulse power in the pseudo-random coded embodiment, thereby restoring average nominal transmitter power, notwithstanding one or more failed solid-state RF amplifiers.

Input surge protection for converter circuit

Abstract: A power converter circuit is disclosed utilizing pulse width modulation for power regulation. A rapid acting surge protection circuit for the power driving switch is operated from a string of zener diodes to disable the power switch. A base charge removal circuit is included for removing accumulated base charges on the driving transistor without the need for a bipolar driving signal for the power transistor.

Detecting circuit for data signal

Abstract: PURPOSE:To obtain the data signal detecting circuit which detects and reproduces the data signal with a good precision, by converting the data signal fed repeatedly in a plural number of times into the high speed pulse train having the number of pulses proportional to the pulse width.