Abstract: The usual xenon radiation source in conventional weathering testers is replaced by UV light-emitting diodes (LEDs) (6). These can be used to provide a good approximation of the UV component of the solar spectrum, in particular when different types of UV light-emitting diodes (6) with different emission characteristics are employed. Optionally, further light-emitting diodes in the visible spectral range may also be used in order to cover other parts of the solar spectrum. The light-emitting diodes (6) may be mounted on a flexible printed circuit board (5), which may in turn be fitted on a tubular holding body (4). The flexible printed circuit board carrying the light-emitting diodes may also be placed on other substrates (7) which are pliable in a geometrically stable way, so that that they can be arranged at a uniform distance from material samples with a particular surface topology, in order to obtain uniform exposure.

Abstract: Drive circuit for operating at least one lamp in an associated load circuit, in which terminals for the lamp are arranged, having two switches in a half-bridge arrangement, each switch including a cascode circuit of a bipolar transistor having a control, a working and a reference electrode, and a field-effect transistor having a control, a working and a reference electrode. The center point of the half-bridge arrangement is coupled to the load circuit, and each cascode circuit has an input circuit, in which a diode and a secondary winding of a transformer, connected in series, are arranged in parallel with the control electrode of the bipolar transistor and the reference electrode of the field-effect transistor, the primary winding of the transformer being arranged in the load circuit such that the load circuit current flows through it when operating the lamp.

Abstract: A device for operating a plurality of discharge lamps (71, 72) is to be fashioned cost effectively. Two lamps (71, 72) are therefore operated in a single load circuit. In the preheating phase, the incandescent filaments (711, 712, 721, 722) are supplied with preheating current either directly or via a transformer (Ls, Lp). The preheating current is controlled via a temperature-dependent resistor (PTC) in such a way that the continuous heating current is greatly reduced over all the filaments during the operation of the lamp.

Abstract: In the case of circuit arrangements for operating discharge lamps (Lp1, Lp2) which include a charge pump for reducing line current harmonics, an energy imbalance occurs when the lamps are started. In order for this not to lead to components being destroyed, but for sufficient ignition voltage nevertheless to be generated at the lamps (Lp1, Lp2), a threshold switch (MOV, TH) monitors the frequency of an inverter included in the circuit arrangement.

Abstract: Circuit arrangement for starting and operating discharge lamps (Lp1, Lp2) with control of the lamp current and preheating of electrode filaments. No control device is required for the sequence of the preheating, igniting and operating phases. This is achieved by a preheating resistor which changes its value after the preheating phase, in combination with controller properties according to the invention.

Abstract: A device for operating a plurality of discharge lamps (71, 72) is to be fashioned cost effectively. Two lamps (71, 72) are therefore operated in a single load circuit. In the preheating phase, the incandescent filaments (711, 712, 721, 722) are supplied with preheating current either directly or via a transformer (Ls, Lp). The preheating current is controlled via a temperature-dependent resistor (PTC) in such a way that the continuous heating current is greatly reduced over all the filaments during the operation of the lamp.

Abstract: Free-running half-bridge inverter (HP) for operating gas discharge lamps having a current transformer as a feedback device. The half-bridge transistors (T1, T2) are essentially voltage controlled transistors (MOSFET). The drive circuits (1, 2) for the half-bridge transistors (T1, T2) contain a voltage threshold value switch (D2, R2) which, on reaching its voltage threshold, essentially carries a current which is proportional to the load current of the half-bridge inverter (HB).

Abstract: Free-running half-bridge inverter (HP) for operating gas discharge lamps having a current transformer as a feedback device. The half-bridge transistors (T1, T2) are essentially voltage controlled transistors (MOSFET). The drive circuits (1, 2) for the half-bridge transistors (T1, T2) contain a voltage threshold value switch (D2, R2) which, on reaching its voltage threshold, essentially carries a current which is proportional to the load current of the half-bridge inverter (HB).

Abstract: The invention relates to a circuit arrangement for operating electric lamps, the circuit arrangement having an inverter for generating a medium or high-frequency supply voltage for one or more lamps (21) and a starting circuit for the inverter, and also a device for deactivating the starting circuit, the starting circuit comprising a voltage-dependent switching element (34) and a capacitor (33), and the device for deactivating the starting circuit comprising a switching means (35) whose switching path is arranged in parallel with the capacitor (33) of the starting circuit. According to the invention, the device for deactivating the starting circuit has a threshold switch (39) for controlling the switching means (35).

Abstract: A method for determining the time curve of the intensity of radiation present at the location of at least one sample which is being examined. The sample follows a circular path of movement in a sealed sample chamber of a weathering testing device, around a stationary radiation device for producing UW and global radiation. At least one sensor which detects the momentary radiation intensity of the radiation device is provided. The sensor moves together with the at least one sample, and is displaced in relation thereto in relation to the radiation device, for example in the peripheral direction of the path of movement. An electrical signal corresponding to the momentary intensity of the radiation is derived by the sensor at set intervals.

Abstract: The invention relates to a circuit arrangement for operating electric lamps, the circuit arrangement having an inverter for generating a medium or high-frequency supply voltage for one or more lamps (21) and a starting circuit for the inverter, and also a device for deactivating the starting circuit, the starting circuit comprising a voltage-dependent switching element (34) and a capacitor (33), and the device for deactivating the starting circuit comprising a switching means (35) whose switching path is arranged in parallel with the capacitor (33) of the starting circuit. According to the invention, the device for deactivating the starting circuit has a threshold switch (39) for controlling the switching means (35).

Abstract: The invention relates to a circuit arrangement for operating at least one low-pressure discharge lamp (LP1, LP2) on an inverter (Q1, Q2). The circuit arrangement has a simplified harmonic filter for limiting the harmonic content of the mains current. In the preferred exemplary embodiment, the harmonic filter is formed by the back-up capacitor (C2), the diode (D1), the trapezoidal capacitor (C7) and the resonance capacitor (C6).

Abstract: The invention relates to a circuit arrangement for operating at least one discharge lamp (LP) on a half-bridge inverter (Q1, Q2), having at least one coupling capacitor (C3) and having a switch-off device (T1, A) which permanently switches off the half-bridge inverter (Q1, Q2) when the lamp (LP) refuses to start. According to the invention, the circuit arrangement has first and second devices (V1, V2) for monitoring the voltage drop across the at least one coupling capacitor (C3) and for activating the switch-off device (T1, A) as a function of the voltage drop detected across the at least one coupling capacitor (C3). If the voltage across the coupling capacitor (C3) deviates substantially from its normal value, for example owing to the occurrence or the rectifying effect at the end of the service life of the discharge lamp (LP), the half-bridge inverter (Q1, Q2) is shut down by the switch-off device (T1, A).

Abstract: The invention concerns the ageing of material samples in the test enclosure f an apparatus for testing exposure to light and weathering, using visible light, UV light and medium- or long-wavelength IR radiation and with air circulation. In order to ensure reproducible test results, a value representing the surface temperature of the sample is measured by means of a temperature sensor and compared, at the input of a control unit, with a predefined reference temperature. In the event of a temperature difference, a control signal generated by the control unit adjusts the power supply to a separate IR radiant heater for medium- and long-wavelength IR radiation in such a way that the difference disappears in accordance with a predefined indicial response.

Abstract: The invention relates to a circuit arrangement for operating electric lamps, having a free-running half-bridge inverter (Q1, Q2). An auxiliary transistor (T1, T2) is in each case connected into the control circuits of the half-bridge inverter transistors (Q1, Q2), so that the emitter impedance of each half-bridge inverter transistor (Q1, Q2) is formed by a parallel circuit which consists of at least one resistor (R5) or (R7) and the control path, arranged in parallel therewith, of the corresponding auxiliary transistor (T1) or (T2). The control inputs of the two auxiliary transistors (T1, T2) are, furthermore, connected to the output of a common control circuit (IC).

Abstract: The circuit arrangement according to the invention has a self-oscillating inverter having at least two alternately switching transistors (Q1, Q2), a load circuit connected to the inverter output and designed as a resonant circuit (L1, C1), and terminals for at least one electric lamp (LP). According to the invention, the control junction of a transistor (T1) is arranged in the emitter line of one of the inverter transistors (Q2). Via the variable conductivity of this control junction, the effective emitter resistance of the inverter transistor (Q2) is continuously varied as a function of the voltage drop across one of the resonant circuit components (C1), and the clock frequency of the inverter (Q1, Q2) is thereby increased so far that because of the now stronger detuning with respect to the resonant frequency of the resonant circuit (C1, L1) a reduction in the no-load voltage in the load circuit is achieved.

Abstract: The invention relates to a circuit arrangement for operating electric lam and an operating method for electric lamps. The circuit arrangement has an inverter ((Q1, Q2) with a switch-off device which switches off the inverter (Q1, Q2) in the case of an anomalous operating state. The switch-off device has a field-effect transistor (T1, T1') whose drain-source junction is arranged in the control circuit of an inverter switching transistor (Q2) and switches the control circuit of the inverter transistor (Q2) between a state which is of low resistance in normal operation and a state which is of high resistance in anomalous operation. After the occurrence of an anomalous operating state, it is advantageous to switch off synchronously with the blocking phase of the inverter transistor (Q2) in whose control circuit the field-effect transistor (T1, T1') is arranged.

Abstract: To operate one or more serially connected low-pressure discharge lamps, tcally fluorescent lamps, a preheating circuit is provided to preheat the electrodes of the lamps (E1, E2, E3, E4), which changes from low-impedance to high-impedance state after the lamps have been preheated by controlling a semiconductor switch (Q3) in the heating circuit. In accordance with the invention, to eliminate reliance on the resistances of the lamp filaments themselves, which are subject to variation from lamp-to-lamp due to manufacturing tolerances, and later on, to changes due to aging of the lamp, and to provide for reliable switching of the semiconductor switch, a sensing impedance element (Z), which may be an ohmic resistor or a capacitor (Z', Z"), is serially connected to the switching path of the semiconductor switch (Q3) which, typically, is a field effect transistor (FET).

Abstract: To control preheating current flow through a fluorescent lamp supplied from high-frequency inverter (T1, T2, A) and a series resonance circuit, an electronic switching control circuit (SC) is connected to the preheating circuit of at least one electrode filament (E1, E2, E10, E20, E11, E21, E12, E22) of one or more of the fluorescent lamps. The switching control circuit senses the voltage across the pair of terminals (T1, T1', T2, T2') of the electrode filaments, or across all the electrode filaments. Since fluorescent lamp filaments have a positive temperature coefficient of resistance, the voltage across the filaments will rise as the filament or filaments of the lamp reach electron emission temperature. This rise in voltage is sensed, for example, by a threshold circuit which may include a Zener diode, and is used to break the preheating circuit.

Abstract: A UV sensor having a photodetector for measurement of UV radiation, an SiO.sub.2 -containing dispersive element disposed ahead of the photodetector in the direction of incident UV radiation and an optional housing having an entry opening for UV radiation. The dispersive element contains quartz glass with interiorly disposed boundary surfaces, the orientations of which are statistically homogeneously distributed.