Showing papers on "Relaxation oscillator published in 1992"

Apparatus and method for detection of latent faults in redundant systems

Abstract: Apparatus and method are provided for fault detecting in an electrical system such as a redundant or fault-tolerant system. A current receiving device connected in shunt or in series in such a system draws electric current from the electrical system being monitored. During normal operation, while current is still flowing properly through the system being monitored, an appropriate indication such as a continued series of pulses is generated, which is interpreted as indicating proper operation. If that current flow is cut off, indicating a fault condition, then the apparatus and method provide an appropriate signal (such as cutoff of the series of pulses) to a communication system which provides an appropriate indication to an external location. The current receiving device can be a relaxation oscillator together with another device which can be a pulse generator, an L-C energy transfer arrangement, a bridge circuit including an inductor, a two-winding inductor or a capacitor. The latter such device can be connected in shunt or in series with the electrical system being monitored. The relaxation oscillator is connected in shunt with the system being monitored. The communication device can, for example, be a photoemitter in combination with a photodetector, or could alternatively be a two-winding transformer.

Multimode Small-Signal Analysis of Side-Mode Injection-Locked Semiconductor Lasers

Abstract: Temporal response of side-mode injection-locked semiconductor lasers is studied using a small signal analysis of multimode rate equations. The relaxation oscillation frequency and the decay rate are shown to be sensitive to the choice of the injection target mode. Modes with shorter wavelengths have higher relaxation frequencies due to their larger differential gain. Maximum enhancement of the relaxation frequency occurs within that group of target modes. The analysis, together with the previously predicted enhancement of stable locking range, suggests feasibility of applying the side-mode injection technique to increase the modulation bandwidth of semiconductor lasers and hence the transmission speed in optical communication systems, while preserving the usual benefits of injection locking.

Plural oscillator circuit arrangement for rapidly resetting a computer circuit

Abstract: A circuit arrangement for providing a frequency for a computer circuit is suggested in which, in adition to a quartz oscillator, an additional oscillator which quickly begins to oscillate is provided. To ensure a quick operation of the computer circuit when switching on the computer circuit or after voltage dips, the oscillator which quickly begins to oscillate is first connected with the computer circuit when voltage is applied, so that the resetting processes can proceed very quickly. If the quartz oscillator has begun to oscillate and has reached a stable operating state, a switching is effected from the oscillator which quickly begins to oscillate to the quartz oscillator which takes over from the latter to continue providing a frequency for the computer circuit. The circuit arrangement can also contain a comparator whose inputs are connected to the respective oscillators and which compares the oscillator frequencies of the output signals from both oscillators. The frequency comparator can be connected to a switch which connects one or the other of the oscillators to the input of the computer circuit according to the comparison of oscillator frequencies in the comparator.

Coupling of the relaxation and resonant elements in the autonomous chaotic relaxation oscillator (ACRO).

Abstract: If a harmonic oscillator is embedded in a relaxation oscillator, the resulting system may behave like an autonomous chaotic relaxation oscillator (ACRO). The discharge transient of the relaxation oscillator excites sinusoidal oscillations in the harmonic oscillator and these sinusoids affect when the next discharge occurs. This can lead to chaotic intervals in the oscillator periods. A simple electronic model of the ACRO is studied over a wide range of parameters using numerical, analytic, and experimental techniques. The dynamics of the ACRO is found to be determined by three parameters: (1) tuning, (2) coupling, and (3) damping. Complex, intermittent outputs can always be inhibited by increasing the damping of the harmonic oscillator. For weak damping, strong coupling yields chaotic periods. With weak damping and weak coupling, complex behavior only occurs if the relaxation oscillator is tuned near a resonance of the harmonic oscillator. A new path to chaos, called a disruption bifurcation, is the source for intermittency in the ACRO. This bifurcation occurs when the amplitude of internal resonances is excited to the degree that existing limit cycles are disrupted.

Phase diagram of a modulated relaxation oscillator with a finite resetting time.

Abstract: A modulated relaxation oscillator with a finite resetting time is considered. The underlying return map, a combination of a circle map and an inverse circle map, respectively, divide the parameter space into four regions of qualitatively different behavior. One region is chaotic, as the return map is not invertible. In another region, a gap exists in the return map and only periodic attractors are possible. In a third region, the return map simultaneously is noninvertible and contains a gap, which gives rise to a wide range of nonlinear phenomena

Controlled retroreflection - A technique for understanding and eliminating parasitic lasing

Abstract: Parasitic lasing is examined with an emphasis on understanding and quantifying its effect on high-gain laser systems. Parasitic lasing is unwanted stimulated emission commonly found in high-gain optical systems. A general technique was developed that carefully retroreflects light back into the optical system, thereby creating an externally induced oscillator. Discrepancies between experimental data and threshold calculations for the externally induced oscillator are direct evidence of optical misalignment or of component performance problems. Any changes in the optical system can be directly measured as a change in threshold for the externally induced oscillator. This technique also enables one to align the system for maximum parasitic suppression with the system fully operational. Experimental data illustrating the utility of this technique are presented.

Electrical resistance test device with an attached comparison resistance set

Abstract: A megohm tester for determining resistance utilizing a relaxation oscillator which generates output pulses, at a rate dependent on an unknown resistance detected at a test site within an electronic apparatus, which can then be compared to known values provided as standards.

Switching circuit for HF low pressure discharge lamp - uses series oscillator resonated at characteristic frequency for lamp ignition

Abstract: The switching circuit comprises a series oscillator with a capacitor (2) connected in parallel with the gas discharge lamp (7), a second capacitor (3) and an inductance (8). The operating voltage for the series oscillator is provided by a voltage source (6a,6b) supplied via a smoothing capacitor (11). The inductance (8) may be provided by a transformer, with a further inductance, or a controlled switch (10) connected in parallel with the lamp (7). The switch may lie in series with a control transistor (5) receiving a control pulse sequence (4) at its base, with the second capacitor (3) in parallel with the control transistor. ADVANTAGE - Reduced circuit complexity and longer operational life by minimising operational voltage.

250 MHz nMOS relaxation oscillator with enhanced linear voltage-frequency characteristic and temperature stability

Abstract: The design of an nMOS relaxation oscillator with an operating frequency of 60–250MHz is presented. The design can be incorporated in a PLL system with centre frequency up to 190 MHz. The oscillator gives a highly linear voltage-frequency characteristic and its temperature coefficient is maintained within ±200 ppm for temperatures ranging from 0 to 80°C. The design was found to be suitable in PLL system applications.

No drift zero-offset magnetometer

Abstract: A magnetometer for measuring a magnetic field has a relaxation oscillator circuit and a measurement element for providing a signalrepresenting the magnitude of the magnetic field. The oscillator includes a sensor having a coil (13) for controlling the period of the oscillator circuit, and the coil having first and second terminals. The oscillator also includes a first resistor (15) coupled to the first terminal and a second resistor (17) coupled to the second terminal. The oscillator also includes a switching element (19) coupled to the first and second terminals and to the input terminal of a driver element (11) for coupling the input terminal alternately to the first and second terminals. A gate element (21) shunts the first resistor to a DC potential when the switching element couples the input terminal of the driver element to the second terminal, and vice versa. the magnetometer will have no output drift when no field is applied.

Research on the relaxation oscillator with BNRT

Abstract: A piecewise linear (with three or four segments) dynamic version for relaxation oscillations in a circuit with a bidirectional negative resistance transistor (BNRT) is studied. The circuit and dynamic equations are given, and some properties of the relaxation oscillations are discussed. Experimental results agree well with the computations, showing that the dynamic model is adequate and useful. >

Short duration power supply back=up for digital counter ICs - uses capacitor and associated switching circuitry to maintain stored counter value during power supply interruptions

Abstract: The circuit is formed from a MOS counter (ICI), a timing oscillator, a smoothing/storage capacitor (C2) and a zenor diode (Z1). The square-wave oscillator is formed from transistor T2, capacitor C3 and resistors R1 and R2, the oscillator time constant being determined by R1 and C3. The oscillator output is rectified by a diode (D8B) and, together with the circuit voltage fed via reverse blocking diode (D8A), is used to enable the switching transistor to control the supply voltage to the ICI timing input (5). Capacitors C1 and C5 buffer the oscillator output and provide smoothing, respectively. The circuit voltage is determined by the zener diode and, under normal conditions, is fed via a reverse blocking diode (D4) to the ICI power supply input (16) and to the smoothing capacitor. When the supply voltage (Ub) is removed, the oscillator power supply (to R1, R2 and C3) is broken, the switching transistor is turned off and the counter supplied with power from the smoothing capacitor. ADVANTAGE - Counter backup supply prevents stored counter value being lost in event of power supply interruption.

Speed-adjusting devices for direct current electric railcars used in mine

Abstract: The utility model relates to a speed-adjusting devices for direct current electric railcars used in mines. The utility model mainly solves the technical problems in the prior art that circuits are complicated, controlled silicones are easily out of controlling, and the controlled silicones are influenced by the frequent fluctuation of electric voltage of wirings. A single controlled silicone is adopted to be used as a direct current switch, a relaxation oscillator is composed of an unijunction transistor, a capacitor, and a resistor; pulses which are generated by the relaxation oscillator can change the time for switching on of the controlled silicone by being magnified and triggering the controlled silicone; regulate mean voltages which are transmitted by regulating the frequencies of the pulses. So the terminal voltages of a direct current motor is changed, and the regulation of speed is realized. The utility model has the advantages of simple structure, reliable work, big regulating ranges, stable work, etc.

Systems of Relaxation Oscillators with Time-Delayed Coupling

Abstract: We study systems of relaxation oscillators in the presence of nearest-neighbor coupling. It is shown that introduction of delay in the coupling leads to a depression of the frequency of individual oscillators as well as of the average frequency of the system. In certain parameter ranges, we also observe the existence of metastable states. Both phenomena can be understood in a simple mean-field like theory.