Abstract: A protected switch has a power first semiconductor device having a first main electrode for coupling to a first voltage supply line, a second main electrode coupled to a first terminal for connection via a load to a second voltage supply line and an insulated gate electrode coupled to a control terminal for supplying a gate control signal to enable conduction of the power semiconductor device. A control arrangement has a normally off second semiconductor device having first and second main electrodes coupling the normally off semiconductor device between the gate electrode of the power semiconductor device and one of the first and second main electrodes of the power first semiconductor device and a control electrode coupled via a resistance to the gate electrode of the power semiconductor device thereby causing the normally off semiconductor device to be rendered conducting when a gate control signal is supplied to the gate electyrode to enable conduction of the power semiconductor device.

Abstract: In a circuit arrangement including a pair of transistors serially connected together in a totem pole arrangement for bridging two buses at different voltage potentials, a driving scheme for controlling the conductive state of one of the pair of transistors. The scheme includes sensing the voltage difference across this one transistor by comparing a substantially fixed level represented by the voltage potential at one bus to a varying level. The varying level is based on the voltage at a junction joining the two transistors together. When the sensed voltage is at or below a predetermined level this one transistor is turned on.

Abstract: A ballast includes safety circuitry which senses lamp status through various phases of ballast operation. According to one feature, the ballast is prevented from supplying an output voltage upon initial energization of the ballast when a lamp is not present at the output terminals. The presence of a filament is sensed via a DC path extending through the filament heater windings of an output transformer. When the DC path is not complete, a control input, for example the power supply input of the ballast controller, is not provided with a voltage to start ballast operation. The DC path is also used to restart the ballast if a defective lamp is replaced with a good one. Over-voltage and capacitive mode detection is also disclosed to shut down ballast output upon lamp failure/removal.

Abstract: A power supply circuit for a two-phase asynchronous motor having two windings at a preset angle there-between. The supply circuit has three nodes at which are respectively supplied three node voltages U1, U2, U3 which are derived as logic combinations of a basic pulse train and a pulsed switching signal having a switching frequency and a duty cycle. The motor windings are respectively connected between the first and second nodes and between the second and third nodes. The voltage U2 at the second node has a rectangular waveform. The voltages U1 and U3 at the first and third nodes alternate between time intervals in which the voltage level is constant and time intervals in which the voltage is pulse modulated, and have a phase angle there-between corresponding to that between the motor windings.

Abstract: An inverter for powering a lamp at deep dim levels. Inverter driving circuitry includes a feedback loop which compares desired dim level to signal representing actual lamp power consumption. Reproducibility of desired lighting conditions for different types of lamps powered by the same ballast over a wide range of temperatures is also provided.

Abstract: A method for automatically initializing a wireless, packet-hopping network, such as a building system control network which is used to control the operation of a building system, such as a lighting, security, and/or HVAC system. In accordance with this initialization method, each node in the network first determines its entire connectivity, i.e., its connectivity to every other node in the network within a prescribed range thereof, and then routes this connectivity information to the building computer. This connectivity information is transmitted in a packet or set of packets that are routed to the building computer, thus minimizing the volume of traffic that the building computer and the nodes nearest thereto must handle, and thus, significantly reducing the probability of collisions of the connectivity information packets. This connectivity information is transmitted using a "software handshaking" technique to ensure that all of the connectivity information is received by the building computer.

Abstract: The invention relates to a circuit arrangement for operating a low-pressure discharge lamp. The circuit arrangement according to the invention comprises means X for supplying the low-pressure discharge lamp, provided with means X1 for generating a current of changing polarity. The circuit arrangement also comprises a feedback network which together with the means X and the low-pressure discharge lamp forms a control loop for controlling a lamp condition parameter. A low-pass filter is included in the control loop. The feedback network is provided with means M for generating a signal m which represents the instantaneous value of the lamp condition parameter, means C for comparing the signal m with a reference signal d, and means S for controlling the means X in dependence on the result of the comparison.

Abstract: A record carrier having standard and high-density information layers. The standard density layer, e.g. in a standard CD format, is positioned at the bottom of a substrate, and is read out through the substrate with a laser beam. The thickness of the substrate is within the CD specification, e.g. 1.2 mm. At least one high-density layer is formed by a material which is (nearly) transparent for the laser wavelength of standard CD players (.lambda.=780 nm), but is (at least partially) reflective for shorter wavelengths used for high-density discs (.lambda.=635 nm). To achieve a high density, a smaller track pitch and smaller pits are used in the high-density layer(s). To achieve better reading signals from both layers, the high-density layer is positioned closer to the side of entrance of the laser beam in the substrate. A higher numeric aperture of the focusing lens and, therefore, a smaller spot for the shorter wavelength results. The high-density layer is preferably positioned midway in the substrate, e.g.

Abstract: The apparatus comprises first and second input terminals (1, 3) for receiving an input voltage, a number of transformers (7), each of which comprises a primary winding (9) having first (13) and second (15) ends, and a secondary winding (11). At least one end of each primary winding is connected to a switching member (17) which comprises a first controllable switching element (19) and a second controllable switching element (21). This end (15) can be connected, via the first switching element (19), to the first input terminal (1) and, via the second switching element (21), to the second input terminal (3). The switching member (17) may be in a first state or a second state, the first switching element (19) being closed and the second switching element (21) being open in the first state whereas in the second state the first switching element is open and the second switching element is closed.

Abstract: A micromotor includes a magnetic rotor fixed on a shaft. A stator has at least one winding. Bearings are provided to rotatably support the shaft relative to the stator. The bearings include a first silicon substrate having a V-groove, with a pair of bounding walls. Both bounding walls extend parallel to the shaft. The bearings also include a second silicon substrate having a third bounding wall which also extends parallel to the shaft. The shaft is positioned relative to the stator by the three bounding walls.

Abstract: A lighting system having at least one light source for supplying artificial light and a control unit for controlling the light source. The light source is of the type having an adjustable color temperature. The control unit is provided with a control signal from a signal generator. The signal generator is dependent on the mean daylight level. The control unit is arranged to adjust the color temperature of the light source in dependence on a predetermined relationship between the mean daylight level and the color temperature of the artificial light. The lighting system will provide artificial light which will when the daylight level, as measured on an office desk, increases from approximately 400 lux to approximately 800 lux, increase the color temperature from approximately 3300 K to approximately 4300 K.

Abstract: A circuit arrangement comprises an inverter with two parallel switching branches which are connected to a DC voltage source and each of which comprises two series-connected switching members, each of which comprises at least one switch and an anti-parallel connected diode. A switching member in one switching branch each time constitutes a diagonal pair in conjunction with a switching member in the other switching branch. A load with a given polarity is connectable to a DC voltage source via the diagonal pair. The voltage on the load temporarily becomes zero upon the change-over from one polarity to the other. A control circuit is provided for opening and closing the switches in a manner such that the switching members are successively switched on and off.

Abstract: An electric motor having a permanent magnet rotor and a stable with two poles and two windings and electronic switching for controlling commutation. To ensure that the motor starts under heavy load conditions, commutation is delayed during a predetermined period of time while the rotor is travelling in a forward direction of rotation to suppress the associated braking torque.

Abstract: A circuit arrangement for alternatingly, at a frequency f, establishing and extinguishing a discharge in each of a plurality of discharge paths, each of which is associated with a first electrode situated at a first end of the discharge path and with a second electrode situated at a second end of the discharge path. Operating voltages are generated from a supply voltage during operation and are present across respective discharge paths and are periodic at the frequency f. The same operating voltage is present across each discharge path. During operation each discharge path is associated with an auxiliary electrode situated alongside the discharge path and the circuit arrangement further comprises respective switching devices for connecting and disconnecting each of the auxiliary electrodes at the frequency f to a terminal of the circuit arrangement to establish an ignition voltage during a part of each period between one of the electrodes and the auxiliary electrode associated with the same discharge path.

Abstract: An improved spindle motor, particularly for a hard-disc drive, having a stator in the form of a cylindrical coil carried by a mounting plate and a permanent magnet rotor carried on a rotatable hub. At its outer circumference the rotor generates a field perpendicular to the axis of rotation. A bell-shaped portion of the hub surrounds the coil. The hub is supported on the motor shaft by axial and radial hydrodynamic bearings. A soft-iron sleeve-shaped yoke externally surrounds the coil configuration. This permits the coil to be free of soft-magnetic parts, thereby reducing its inductance and improving the dynamic drive characteristics of the motor. The coil is preferably formed by curved foil windings, so there are no winding slots. This avoids the production of detent torques.

Abstract: The power supply apparatus serves to convert an electric direct voltage, acting as an input voltage, into an output voltage and comprises positive and negative input terminals (1, 3) which are arranged to receive the input voltage.

Abstract: A power supply apparatus including at least one coil and a controllable switching element and a peak-limiting circuit for limiting the maximum voltage across the switching element. The peak-limiting circuit includes a capacitor and a series connection of a first rectifier element and a resistor, as well as a second rectifier element which connects one end of the series connection to the positive input terminal of the apparatus. The energy dissipation in the resistor is dependent on the duty cycle of the switching element. The duty cycle in turn is dependent on the load of the power supply apparatus. Consequently, when the load of the power supply apparatus is small, the dissipation of the apparatus will be substantially lower.

Abstract: An inverter driving scheme for detecting when an inverter is in or near a capacitive mode of operation. In response to being within a capacitive mode of operation, the switching frequency is immediately increased to its maximum setting. When a near capacitive mode of operation is detected, the switching frequency is increased at a preset rate. During overvoltage conditions across the lamp combined with a near capacitive mode of operation, the switching frequency is immediately increased to its maximum setting.

Abstract: A lamp controller includes an interface circuit, or receiver, which receives an input signal and decodes control signals supplied from a transmitting device, such as a power line wall controller, according to at least two of the following communication techniques: phase angle control, step control, and coded control. The receiver tests the input signal and identifies which type of control technique is employed by the wall controller connected to the lamp controller. The receiver then decodes the control command from the input signal. In a disclosed embodiment, the lamp controller is gas discharge lamp dimming ballast having a two wire input for connection to the hot dimmed and neutral leads of the power line controller. The ballast has an improved topology in which a pre-conditioner supplies a substantially constant DC voltage to a ballast stage including an inverter, a resonant tank output and a control circuit.

Abstract: A lamp driving circuit having a series inductor and capacitor (L-C) in which the lamp load is connected in parallel with the capacitor. During pre-ignition of the lamp load, the driving signal supplied by a half-bridge oscillator includes a fundamental frequency and higher odd harmonics including a third harmonic of the fundamental frequency. The resonant frequency of the series connected L-C circuit is at least .sqroot.5 times greater than the fundamental frequency but not equal to the higher odd harmonic frequencies, preferably less than the third harmonic of the driving signal.