Abstract: A voltage converter for converting an input voltage into at least a first high output voltage and a second lower output voltage. An input resonant circuit includes a transformer primary winding. At least first and second output circuits, each of which includes a respective secondary winding or a part of a secondary winding of the transformer and which supply the first and second output voltages. The second output circuit includes a rectifier arrangement supplying a DC output voltage. To improve the synchronism of the output voltages, i.e. reduce the cross-regulation, an additional capacitance is connected parallel to the secondary winding of the second output circuit and is dimensioned such that its capacitance, transformed to the primary winding essentially corresponds to the capacitance, transformed to the primary winding, of a parallel capacitance of the secondary winding of the first output circuit.

Abstract: Lamp voltage or current obtained from a self-oscillating converter is stabilized by a feedback circuit. Gates of the switching transistors are connected to output windings of a current transformer whose input current winding is in series with the resonant load lamp circuit. The lamp voltage or current is sensed, and the resulting signal is used to control current through an auxiliary control winding on the current transformer. Preferably, two opposite conductivity type control transistors are connected in parallel across the control winding, and low-pass filtered DC signals corresponding to the lamp voltage or current bias the control transistors.

Abstract: A circuit arrangement for supplying a discharge lamp with a direct current includes input terminals for connection to a supply voltage source. A circuit portion (I) is coupled to the input terminals for generating a DC voltage from the supply voltage and is provided with output terminals between which the DC voltage is present during operation. A first branch comprising a first capacitor interconnects the output terminals and a second branch comprising a series arrangement of a second capacitor and an impedance shunts the first branch. A load branch shunts the series arrangement and comprises terminals for connecting a discharge lamp. The second branch also includes a diode so that a discharge lamp operated by way of the circuit arrangement stabilizes satisfactorily after ignition by a current supplied by the second capacitor to the lamp via the impedance.

Abstract: A circuit for operating a discharge lamp from input terminals of a low frequency (f) supply voltage source with a rectifier coupled to the input terminals for rectifying the low-frequency supply voltage. A capacitor is coupled to the output of the rectifier. A DC-AC converter is coupled to the capacitor for generating a lamp current which comprises a DC component and a high-frequency AC component, the amplitude of the high-frequency AC component being modulated with a low frequency which is equal to twice the frequency f. An apparatus (V) adjusts the lamp power. The circuit parameters are chosen such that during operation the average amplitude of the high-frequency lamp current component is at least 500 times the amplitude of the low-frequency modulation of the high-frequency lamp current component with the power set for its maximum adjustable value. As a result, the discharge lamp can be dimmed over a wide range without striations occurring.

Abstract: A display device (1) is provided with a window frame (7). This window frame is arranged on the front wall (2). A vacuum-tight connection (10) is formed between the window frame and the front wall, and between the window frame and a rear wall (3) or a projecting portion of an intermediate element (4). The window frame reduces the risk of leakage, reinforces the construction and enables an improved method of manufacturing the display device to be achieved.

Abstract: In a navigation system a driver of a vehicle is guided along a planned route (310) from an origin to a destination. The system comprises a receiver (122) for receiving a traffic message of an actual travel condition concerning a road-element. The system comprises an evaluation module (126) to determine whether the received traffic message makes it necessary to plan a new route to the destination. If a traffic message is received for a road-element which does not form a part of the planned route (212), the evaluation module determines whether the message indicates an improvement (204) of the travel condition of that road-element and if this is so then the planning module plans a new route.

Abstract: Circulating current through a resonant tank circuit and inverter switches is reduced by feeding high frequency current back through a line inductor. A resonant load circuit is connected between an inverter output node and one of the terminals of the input rectifier circuit. A high frequency capacitor has one terminal connected to an AC-side terminal of the input rectifier circuit. The line inductor and the high frequency capacitor have values selected such that instantaneous high frequency capacitor current flow into that AC-side terminal has a greater magnitude than and polarity opposite to current through the line inductor into that AC-side terminal during a portion of every cycle of the high frequency voltage.

Abstract: A circuit arrangement for high-frequency operation of a discharge lamp comprises a low-frequency rectifier for generating a DC voltage (buffer voltage) across a first capacitor (C1) from a low-frequency supply voltage. A DC/AC converter generates a high-frequency AC voltage from the buffer voltage. A load branch is coupled to the DC/AC converter and is provided with coupling terminals for coupling the discharge lamp to the load branch. A high-frequency rectifier (HR) converts the high-frequency voltage generated by the DC/AC converter into a DC voltage and comprises a series arrangement of first and second diodes (D5, D6) which have the same orientation. A control circuit (CR) controls the power consumed by the discharge lamp to a level which is dependent on a control signal (Sg). The high-frequency rectifier further comprises a switching device and a further control circuit (CR1). The switching device shunts at least one of the diodes of a feedback unit.

Abstract: A differential interferometer system for measuring the mutual positions and movements of a first object (WH) and a second object (MH). The system comprises a first interferometer unit (1, 2, 3, 4) having a first measuring reflector (RW) and a second interferometer unit (5, 6, 7, 8) having a second measuring reflector (RM). Since a measuring beam (b.sub.m) passes through both the first and the second interferometer unit and is reflected by both the first and the second measuring reflector, and since the measuring beam and the reference beam (b.sub.r) traverse the same path at least between the two interferometer units, accurate measurements can be preformed very rapidly. The interferometer system may be used to great advantage in a step-and-scan-lithographic projection apparatus.

Abstract: A compact flourescent lamp in which the level of illumination is controlled by a triac dimmer. Premature turn off of the triac dimmer is avoided through the serial combination of at least one resistor and at least one capacitor forming a snubber placed across the output of the electromagnetic interference filter of the compact flourescent lamp ballast. The snubber dampens oscillations generated within the compact flourescent lamp whereby sufficient power is drawn by the compact flourescent lamp to sustain conduction of the triac dimmer throughout the dimming range of the latter.

Abstract: The invention relates to a circuit arrangement for operating a discharge lamp with a high frequency current comprising a power feedback circuit and a electrode preheater. The circuit arrangement comprises an antiboost switch for disabling the power feedback circuit before the lamp has ignited and enabling the power feedback circuit after the lamp has ignited- In accordance with the invention the antiboost switch is also used to enable the electrode preheater before the lamp has ignited and to disable the electrode preheater after the lamp has ignited.

Abstract: A flyback converter based on a switcher IC with Pulse Width Modulation control of the switching transistor. The pulse width is controlled by changing the input current at the control input. Under normal operating conditions the voltage at the control input is maintained at a fixed level, which voltage also serves as a supply voltage for the control unit. A charge pump provides extra charge for the smoothing capacitor at the control input when the load would cause the voltage across the smoothing capacitor to collapse below the fixed level, thereby preventing the control unit from entering the auto-restart mode of the switcher IC. In this way the flyback converter can be used as a constant power source for charging rechargeable batteries with a working voltage lower than the nominal operating output voltage of the converter.

Abstract: A circuit arrangement for igniting and operating at least two discharge lamps. the circuit is provided with input terminals (K1,K2) for connection to a supply voltage source and a circuit I (SC, S1, S2) coupled to the input terminals for generating a high-frequency voltage from a supply voltage delivered by the supply voltage source. A load branch B is coupled to the circuit I and comprising a first branch A including first terminals (K3,K3') for accommodating a discharge lamp and a first inductive element L1, and a second branch C shunting the first branch A and comprising further terminals (K4,K4') for accommodating a discharge lamp and a second inductive element L2 which is magnetically coupled to the first inductive element L1. A circuit II limits the voltage across branch A and branch C to a first value during the ignition of the discharge lamps.

Abstract: A method for the low-transient power control of electrical loads, particularly temperature-dependent loads electrically divided into essentially equal sub-loads connectable to an a.c. mains in order to receive power. Power control at low power levels utilizes alternately power-off phases, in which none of the sub-loads receive power for at least three a.c. half-waves, and heating phases, in which a temporal concatenation of at least a first and a second basic cycle of three a.c. half-waves supply power to each one of the sub-loads. The first sub-load receives power during one half-wave of the first basic cycle and the second sub-load receives power during one half-wave of the second basic cycle. The power is turned off during the other two half-waves of the first and the second basic cycle. Also disclosed is an electrical heating apparatus which embodies this method.

Abstract: A circuit arrangement for igniting a high pressure discharge lamp includes a secondary winding of a pulse transformer which is at least partially capacitively shunted forming a tuned filter. The tuned filter preferably forms a band pass filter for passing the second harmonic of the signal produced by a pulse generator. An increase in the supply of current during take-over results thereby minimizing the time required for ignition.

Abstract: A circuit arrangement for igniting and operating a high intensity discharge lamp including a Buck converter. The Buck converter includes a switch, a rectifier and an inductor having primary and secondary windings. The secondary winding is part of an integrator for controlling the non-conductive state of the switch. A detector responsive to the flow of current through the rectifier produces a signal supplied to the integrator output during the non-conductive state of the switch. The integrator output remains proportional to the flow of current through the inductor regardless of the state of the switch. Consequently, the time duration that the switch is in its non-conductive state can be limited while maintaining the circuit arrangement in a reliable non-self oscillatory mode of operation.

Abstract: A fluorescent lamp ballast having an integrated circuit driver which avoids lamp flicker caused by momentary dips in mains voltage during lamp turn on. The anti-flicker scheme within the fluorescent lamp ballast driver distinguishes between operating conditions during and after preheat of the lamp electrodes. By maintaining the voltage for powering the integrated circuit driver above its minimum threshold, the driver does not momentarily shut off during lamp turn on.

Abstract: A switched-mode power supply uses duty cycle control for the switching transistor. The primary current through the primary winding is sensed by means of a sensing resistor in series with the switching transistor. The voltage across the sensing resistor is differentiated, compared with a reference and integrated. The integrated signal lengthens the off period of the switching transistor, thereby limiting the peak value of the primary current at the beginning of the on period of the switching transistor. The peak value of the primary current at the end of the on period is limited by sensing the voltage across the sensing resistor. The combined limitations of the primary current ensure that the output current of the switched-mode power supply is limited in a well-defined manner.

Abstract: A power supply, including a resonant circuit having an output voltage and a current oscillating therethrough, and a voltage-fed half-bridge inverter producing a source voltage at an output coupled to the resonant circuit. The inverter is responsive to a driving signal. A driving circuit has a first input representing the sensed current oscillating through the resonant circuit, a second input representing the output voltage, and a reference voltage. The driving circuit includes compensation circuitry for maintaining the output voltage at the reference voltage and commanding a phase shift angle, and phase-shifting circuitry producing the driving signal based on a phase-shift of the sensed current. The amount of phase shift is commanded by the compensation circuitry.

Abstract: A triac dimmable compact fluorescent lamp having a low power factor. A power feedback circuit coupled between the input and output stages of the lamp ballast creates sufficient current demand to sustain triac conduction at low dim levels. The power fed back from the output stage to the input stage, which includes a voltage doubler, reflects the voltage across the lamp.