Abstract: A pulse igniter for a discharge lamp has a transformer with a primary winding coupled to a first capacitor and a switching element and a secondary winding shunted by a series circuit of a diode and a second capacitor at its output. As a result, the generated ignition voltage is rectified and applied to the lamp for a relatively long time interval, resulting in improved ignition behavior.

Abstract: A bi-level output electronic high intensity discharge (HID) ballast system includes a circuit for selectively generating a bi-level output for powering a lamp and an electronic HID ballast with a feedback loop. The system also includes an error amplifier receiving a first signal indicative of one of current and power applied to the lamp and a reference voltage and generating a control signal applied to the feedback loop to thereby control power the applied to the lamp, and a switch which controls the level of the reference voltage. Alternatively, the system includes an error amplifier receiving a feedback signal indicative of one of current and power generated by the electronic HID ballast and a reference voltage and generating a control signal applied to the feedback loop to thereby control the power applied to the lamp, and a switch which controls the level of the feedback signal.

Abstract: A device which detects the angle of rotation of a rotor with respect to a stator of a brushless multi-phase d.c. motor. The rotor comprises a permanent magnet and the stator comprises a plurality of electrical windings. Electric drive signals are applied to the windings in order to drive the rotor. The device includes a drive circuit for applying pulse-shaped electric test signals to the windings while the rotor does not rotate. A measurement circuit detects flyback pulses generated by the motor in response to the test signals. A processing unit processes the durations of the detected flyback pulses in combination in order to determine the angle of rotation. On the basis of the angle of rotation thus determined, the motor can be started such that the rotor is set into rotation in a predetermined direction of rotation.

Abstract: A ballast circuit for a compact fluorescent lamp includes a down-converter for operating the lamp with a DC current during stationary operation. The ballast circuit is equipped with an additional inductor. The choke of the down-converter and the additional inductor jointly ignite the lamp. During stationary operation, the additional inductor conveys no current.

Abstract: An electronic fluorescent lamp ballast having output voltage stabilized by a bandpass filter connected between a transformer control winding and the switching electrode of the switching transistor. In one embodiment especially adapted for ballasts which power multiple lamps, the filter causes oscillation frequency to vary with the number of lamps lit in such a way that output (lamp) voltage remains relatively constant. A filter for this application preferably includes a low-Q tank circuit in the series path of a &pgr; section, and has an input high pass T section. In another embodiment, a low cost electronic ballast having power feedback uses passive bandpass filters between transformer control windings and the control electrodes, so as to simplify the control and driver circuitry.

Abstract: An apparatus for detecting peaks of positive and negative polarity in an information signal. The apparatus comprises a first peak detector means for detecting the positive peaks and a second peak detector for detecting the negative peaks. The first peak detector means comprises a first capacitor, and has an attack time for charging the first capacitor (32) and a decay time for discharging the first capacitor, the attack time being shorter than the decay time. The first peak detector has an output for generating an output signal (42) having a first output signal value when the first peak detector is in a charging state for charging the first capacitor and having a second output value when the first peak detector is in a non-charging state.

Abstract: A ballast circuit for a compact fluorescent lamp includes a down-converter for operating the lamp with a DC current during stationary operation. First and second input terminals provide a DC supply voltage and first and second output terminals connect to the lamp. The down-converter has a first switch and a diode serially connected to the input terminals and an inductor coupled to the first switch and to one output terminal. A second switch is coupled to the output terminal. A control circuit operates the first switch at a high frequency. During the preheating and ignition phase, the down-converter is operated in the continuous mode and during stationary operation in the discontinuous mode by control of the switching frequency of the first switch.

Abstract: An apparatus for reducing vertical segregation of a discharge lamp. A current/voltage input sweeps through a frequency range between the first azimuthal acoustic resonance mode and a first radial acoustic resonance mode of the discharge lamp. The current/voltage input is subsequently amplitude modulated. Alternatively, without amplitude modulation, the current/voltage input sweeps through the frequency range for a first portion of the period, and then for a second portion of the period drops to a relatively constant frequency.

Abstract: A high power electronic ballast for operating one or more discharge lamps includes a power factor correction high frequency converter input stage in cascade with an output stage made up of a half-bridge resonant converter. In place of the conventional isolation transformer in the output stage, the input stage utilizes a single integrated transformer inductor magnetic component, thereby eliminating the usual output stage isolation transformer. The input stage is operated in a critical conduction mode which further improves the electronic ballast.

Abstract: A dimming interface for translating the conduction pulse width of a signal produced by a triac dimmer into a proportional rectified average voltage serving as a dimming signal. The dimming signal is supplied as an input to an IC driver for controlling the level of lamp illumination. The proportional rectified average voltage can be converted into a signal representing a duty cylce whereby a variation in the mains line voltage does not affect the dimming signal.

Abstract: A digital to analogue converter includes at least one capacitor for storing an analogue output voltage resulting from the digital to analogue conversion. The converter further includes an output switch arrangement coupling the at least one capacitor to an output of the converter. The output switch arrangement is operated a plurality of times for each digital to analogue conversion, so that the analogue output voltage is switched to the output of the converter a plurality of times for each digital to analogue conversion. Each switching operation reduces the influence of an output load capacitance on the output signal. As a result smaller components can be used in the converter to achieve a given output signal resolution.

Abstract: A laminated magnetic core assembly and method of manufacture having at least one notch formed along opposite sides of a strip material from which the laminations are formed. The notches on the opposite sides of the strip are punched out and separated from each other by a fixed distance. The notches minimize the amount of scrap material by avoiding the need for increasing the width of the strip from which a narrower strip having precision cut sides is formed.

Abstract: A ballast for operating different types of lamp loads through identification of the lamp type during steady state operation of the lamp load. Lamp type recognition is achieved based on a comparison of the lamp load voltage and lamp load current data points stored in a random-access memory of a microprocessor to a plurality of V-I characteristic curves stored in a read-only memory of the microprocessor. Through this comparison, the ballast can distinguish among a number of different lamp loads having the same starting voltage.

Abstract: A circuit arrangement for igniting and operating an electrodeless discharge lamp provided with a half-bridge commutator having two switching elements each having an emitter electrode and a control electrode and a parasitic capacitance in between. Each switching element is alternately switched to a conducting state by means of a resonant control circuit. The resonant control circuit is coupled to an oscillator by way of a transformer. The resonant circuit is provided with a capacitor which forms a part of the oscillator.

Abstract: An electronic ballast for reducing blackening of a high intensity discharge lamp, reducing stress on both the lamp and ballast components caused by excessive voltage and current flow and increasing the lamp's effective life. These advantages are achieved through a ballast controller which readjusts the operating frequency of the lamp during each of the three phases of lamp start-up to limit lamp voltage to a predetermined level.

Abstract: In a receiver, two tuners (TUN1,TUN2) provide concurrent reception of mutually different signals. The two tuners are merged into one module (MOD). This may give rise to mutual interference. However, there are various cost-efficient measures to counter such mutual interference. One such measure is that an oscillation frequency in either of the two tuners does not coincide with the radio frequency, or any sub-harmonic of the radio frequency, of the signal received by the respective other tuner.

Abstract: A ballast for a compact fluorescent lamp includes a down-converter for operating the lamp with a DC current during stable operation and a charge pump for igniting the lamp. The converter includes an inductor and a first series circuit of a first diodie and a first switching element. An output capacitor shunts the lap terminals. The charge pump includes a second series circuit of second diodie and a second switching element coupled to the lamp terminals with the second diode polarized to prevent the discharge of the output capacitor when the second switching element is conductive. The inductor cooperates with the first and second diodes and the second switching element to build up the voltage across the outpout capacitor to the ignition voltage level of the lamp.

Abstract: A projection system includes first and second light sources which are disposed at an angle with respect to each other and are activated during respective different phases of an illumination cycle to illuminate a spot on different sides of a segmented rotary filter wheel. The filter wheel is alternately used to transmit light from one of the light sources, and to reflect light from the other light source, to a light valve, the output of which is projected onto a screen. The wheel segments may be alternately clear and mirrored or may alternately transmit and reflect colors to produce color sequential illumination of the light valve. In addition to filter wheels producing sequences of red, blue, green illumination, including the possibility of splitting a color phase into non-adjacent smaller phases to reduce color artifacts, a simple filter wheel which in two rotations produces a sequence of red, blue, green, cyan, magenta, yellow color illumination, resulting in an expanded color gamut, is also disclosed.

Abstract: A circuit arrangement for operating a semiconductor light source includes connection terminals for connecting a control unit, an input filter, a converter comprising a control circuit, output terminals for connecting the semiconductor light source, an apparatus CM for removing a leakage current occurring in the control unit in the non-conducting state, and a self-regulating circuit for deactivating the apparatus CM. The circuit arrangement is also provided with a detection circuit for detecting an incorrect functioning of the converter or the semiconductor light source. For this purpose, preferably a minimum voltage and a maximum voltage are detected at the output terminals.

Abstract: An improved high intensity discharge ("HID") ignition circuit for a ballast uses a gapped transformer with a capacitor placed across the secondary thereof. The ballast includes a DC source, a down converter, a commutator, and the ignition circuit. The output of the commutator is supplied to the secondary winding of the gapped transformer and the lamp, which are connected in series. The lamp is an HID lamp such as, for example, a metal halide lamp, high pressure sodium lamp, high pressure mercury lamp, or a metal vapor lamp. Power is furnished to the lamp over a cable. Ignition of the lamp is handled by the ignition circuit, which in addition to the secondary winding and the capacitor includes an inductor, the primary winding of the gapped transformer, two SIDACs, and the parallel combination of a resistor and a capacitor, all connected in series between the output of the down converter.