Abstract:
A dimmer circuit arrangement is disclosed including a second control circuit for controlling the operation of a triac for delivering current to a load, and a first control circuit for controlling the operation of an IGBT power semiconductor switch for controlling the rate of rise of load voltage. The first control circuit also controls the operation of the second control circuit.
Abstract:
A circuit for controlling a triac, comprising: a bidirectional current-limiting active element connecting the triac gate to its opposite power electrode; and a switch connecting the gate to the other power electrode of the triac.
Abstract:
A circuit arrangement for generating representations of supply voltages that includes a first path that receives control signals, the first path having a subtracter for forming a difference signal from two of the control signals and a low pass filter to receive the difference signal. A second path receives the control signals, the second path includes a second low pass filters that passes frequencies higher than the first low pass filter does. Output signals of the first and second paths are fed to a combination network which, as a function of the difference between the output signals of the first and second paths, passes on the output signals of one of the first and second paths.
Abstract:
A direct current voltage controlled triggering circuit for triacs connected via a consumer resistor to an alternating current supply voltage uses the controllable channel resistance of a field effect rransistor to distribute loading current among a series connection of capacitors connected via a load resistor and the consumer resistor to the a.c. supply voltage. A connection point of the load resistor and a load capacitor in the series connection is connected via a diac to the gate electrode of the triac, and the remaining series connected capacitors have an approximately equal value to provide symmetrization of the current flow phase angle for the diac.
Abstract:
A synchronization voltage is formed as the product of the output voltage of a phase-locked loop and the mean value of the magnitude of the network voltage. The synchronization voltage is compared with the network voltage. A first control signal is formed when both voltages are the same. A reversing switch, in a first switching state, conducts the network voltage and, in a second switching state, conducts the synchronization voltage to a reference frequency-input of the phase-locked loop. A second control signal is formed when the phase-locked loop locks or latches with the thereto inputted reference frequency. The reversing switch is controlled by both control signals such that upon absence of the first control signal and the simultaneous presence of the second control signal there is attained the second switching state and otherwise the first switching state. The circuit can be beneficially used in a current regulation circuit of a drive for a powerful electric motor, with a power supply network operating at up to 400 Hz with a weak generator.
Abstract:
A system for providing a firing signal to an electrical power switch at a selectable instant during each cycle of a periodic waveform electric power source. A comparator receives a signal varying monotonically with time and a control voltage as inputs, and produces the firing signal at such time that one of these inputs first exceeds the other. The control voltage is clamped to a predetermined value to provide a minimum power output from the electrical power switch.
Abstract:
A power circuit for a precipitator utilizes a pair of silicon controlled rectifiers (SCR's) which are triggered by detecting the zero crossover of a power signal. The power transmitted through the SCR's is determined by the time period from the detection of the zero crossover to the generation of the trigger signal. Power signals are typically subject to noise which interferes with the detection of the zero crossover. Filters are provided for reducing the noise interference but function without altering the phase relation of the zero crossover of the filtered signal in respect to the unfiltered power signal. A pulse train of higher frequency than the power signal is generated to provide a plurality of triggering pulses for the SCR. Further, phase control signals are generated for each SCR to prevent the generation of trigger pulses when the SCR's are reverse biased. Thus, the present invention provides a precision voltage control for a power supply circuit which is particularly applicable for powering an electrostatic precipitator.
Abstract:
The present invention relates to a power supply for a gas discharge lamp such as a xenon arc lamp normally operating in the thermionic emission mode. The power supply is energized from an a.c. line and includes a d.c. source of low voltage and high current for sustained operation and a starter. During starting, the starter provides a succession of high voltage trigger pulses for initiating the gas discharge and a succession of unidirectional, medium voltage power pulses synchronized with the trigger pulses for heating the lamp to thermionic emission temperature. The medium voltage pulses are portions of half cycles derived from the a.c. line and applied to the lamp without filtering or energy storage. The circuit uses low cost components and provides a gradual warm-up of the lamp with a minimum of thermal shock.
Abstract:
The circuit for controlling the power supplied to a load from an alternating source in which a silicon control rectifier is connected in series with the source and the load. The particular silicon control rectifier used is one in which the impedance between the cathode and the gate is sufficiently high so that a simple RC firing circuit can be connected to the gate and the capacitor charged periodically to a value sufficient to effect conduction of the SCR.
Abstract:
A phase controlled power supply having a gate-controlled current regulator, such as a silicon controlled rectifier, and a gate signal generator circuit including a unijunction transistor, in which substantially equal power dissipation is provided through a load device regardless of variations in the magnitude of an alternating current supply voltage. Regulation of the current flow is achieved by varying the firing time or angle of the unijunction transistor when there is a variation in the magnitude of the supply voltage. This variation is achieved by connecting a capacitor having a value between 0.1 and 0.5 microfarads between the base-two electrode of the unijunction transistor and an electrode of the gate-controlled current regulator.