Abstract: Color properties of high pressure sodium vapor discharge lamps are improved by disclosed operating circuit for applying pulsed direct current to the lamp. The circuit comprises a direct current supply circuit, a transistor switch in series with a ballast inductor and a lamp across the supply circuit, an SCR switch connected across the inductor, a coasting diode across the inductor and lamp, and a control circuit connected to the switches for applying DC pulses to the lamp at a predetermined repetition rate and duty cycle. The circuit produces pulse waveforms which provide optimum color improvement in the lamp and makes efficient use of the energy supplied from the power source.

Abstract: Circuit operating from a direct current source applies DC pulses to a high pressure sodium vapor lamp to improve the color properties of the lamp. The circuit includes a controlled thyristor switch in series with the lamp, an RC timing circuit for periodically turning on the switch at predetermined intervals, and an LC circuit for turning the switch off. An inductor comprising the primary winding of a transformer in series with a diode across the capacitor of the LC circuit provides for discharge of the capacitor to enable subsequent re-charging thereof, so as to produce the desired pulsed operation of the circuit, and the transformer secondary winding in series with a diode clamps the voltage of the primary winding. The disclosed arrangement prevents excessive voltage across the controlled switch and provides for the control of lamp wattage with respect to changes in lamp voltage.

Abstract: A high frequency power supply with inductive coupling and a SCR starter to light two fluorescent lamps is described. It supplies high frequency square waves to the fluorescent lamp for improved light output, efficiency and stability of operation. The rectified line voltage from a full wave rectifier is fed via a SCR starter to two transistors that form an inverter circuit. The inverter circuit is coupled to a ferrite core autotransformer. The secondary windings of the autotransformer are used to heat the filaments of the electrodes of the fluorescent lamp, and to form a reactive coupling along with inductors for stabilizing the arc discharge of the fluorescent lamp.

Abstract: An illuminating device for a microscope provided with a lighting control circuit controlled by changing the firing angle for which an impedance means is inserted between the output side of said lighting control circuit and primary side of the transformer in order to obtain a gentle rising curve for the current at the time of firing, thus to reduce the noise.

Abstract: A circuit arrangement for starting a linear metal halide arc discharge lamp while in a transistor switching bridge inverter circuit. A pulse generator is electrically connected to a trigger electrode which is mounted in close proximity to the lamp for supplying pulsed high voltage. The trigger electrode is capacitively coupled to the lamp for supplying pulsed high voltage for starting the lamp. A first logic gate is connected in circuit between a pulse width modulator and a phase splitter driver and is responsive to lamp current to lock the driver in a constant mode until the lamp starts. A second logic gate is connected to the pulse generator and is responsive to lamp current to inhibit the generator when the lamp is on. The pulse width modulator produces, when enabled, a variable pulse train having a fast rise and fall time. This variable pulse train is delivered to the phase splitter driver within which is developed the signal for driving the inverter.

Abstract: A lighting system for gaseous-discharge lamps for applying high voltage pulses to ignite the lamp and for discontinuing the application of high voltage pulses when the lamp is operating. The system includes ballast facilities having an inductive portion, and a control circuit which is responsive to a voltage induced in the inductive portion when the gaseous-discharge lamp operates. When the control circuit is operative, the pulsing portion of the system is disabled. The system is arranged so that the components of the control and pulsing circuits are not subjected to the application of high voltage pulses at any time.