Abstract: A current source and an associated method for supplying current to a load such as an arrangement of LEDs. The intensity of the supplied current varies as a function of the temperature of the load. The intensity of the current is temperature-dependent and limited to a predefined maximum. The temperature dependence is achieved by the component parts that are used without the help of special temperature sensors. The current source is supplied with a reference voltage derived from an integrated circuit. The reference voltage is tapped from a port of the IC and therefore it is switchable. The reference voltage is used to produce a control current, which is fed through a driver stage to produce the current of the current source. Elements in the current source limit the current's intensity and change it as a function of temperature.

Abstract: A current source and an associated method for supplying current to a load such as an arrangement of LEDs. The intensity of the supplied current varies as a function of the temperature of the load. The intensity of the current is temperature-dependent and limited to a predefined maximum. The temperature dependence is achieved by the component parts that are used without the help of special temperature sensors. The current source is supplied with a reference voltage derived from an integrated circuit. The reference voltage is tapped from a port of the IC and therefore it is switchable. The reference voltage is used to produce a control current, which is fed through a driver stage to produce the current of the current source. Elements in the current source limit the current's intensity and change it as a function of temperature.

Abstract: The invention relates to an X-ray apparatus, comprising a rotary-anode X-ray tube, a device for monitoring the rotational speed of a rotary-anode drive motor of the X-ray tube, a sensor circuit for determining an angle signal which is dependent on the phase angle between a reference voltage and a current associated with the motor, a comparator circuit for detecting the angle signal variation which serves as a criterion for the rotational speed of the motor, and also comprising a frequency changer. Thanks to the fact that there is provided a device for forming a brief keying signal so as to trigger a reduction of the frequency of the rotary-anode drive motor, the device is also suitable for induction motors in which only a small phase angle variation is measured between standstill and the operating rotational speed.

Abstract: The invention relates to an X-ray apparatus, comprising a circuit arrangement for accelerating and decelerating the rotary anode of a rotary-anode X-ray tube in which phase-shifted alternating voltages can be applied to the stator windings of the drive motor for the rotary anode in an acceleration mode and a direct voltage acts on at least one of the windings in a deceleration mode, and also comprising a control device for the acceleration mode and the deceleration mode.

Abstract: A series resonant circuit and at least two push-pull connected electronic switches are traversed by a respective halfwave of the resonant-circuit current and via which switches the series resonant circuit is coupled to a d.c. source. GTO thyristors form the electronic switches, which thyristors are switched by a pulse generator device which generates a blocking pulse at the zero crossing of the resonant-circuit current and which generates a trigger pulse for the subsequently conductive GTO thyristor a predetermined delay time after activation of the blocking pulse to selectively shape the output current of the inverter to control the resultant power.

Abstract: A power generator drives a rotating anode of an X-ray tube via a stator-rotor in which the stator receives the anode side high voltage potential. An isolating transformer is connected to an alternating current source which converts DC voltage to AC voltage via a rectifier bridge, a regulator and a switching inverter. The secondary winding of the isolating transformer is coupled to a second rectifier bridge for applying rectified voltage to a second switching inverter that generates the alternating currents for the stator windings. The second inverter receives the high voltage which is also applied to the tube to generate X-rays.

Abstract: The invention relates to a drive system for a rotary-anode X-ray tube which comprises an asynchronous motor. The current through the stator windings is generated by two pulse-width modulators to which sinusoidal signals which are phase-shifted 90.degree. with respect to one another are supplied by a sine and a cosine memory. The amplitude thereof is controlled in dependence on the amplitude of the current through the relevant stator winding.

Abstract: Known circuit arrangements which measure and indicate the speed of a rotary-anode X-ray tube require that sensors be provided in the tube cover. This invention, however, does not require any modification in the tube cover and still provides an accurate speed measurement. According to the invention, the amplitudes I.sub.1, I.sub.2 of the currents through the two stator winding pairs are multiplied together and by the sine of the phase angle between the two currents. For a predetermined moment of inertia of the anode disc a given speed is reached when the integral of the product thus formed has reached a given value. When use is made of a rotary-anode X-ray tube whose anode discs have different moments of inertia, a predetermined speed is reached if the integral of the product I.sub.1. I.sub.2. sin .alpha. has reached a value proportional to the moment of inertia of the anode disc of the associated X-ray tube.

Abstract: A circuit to avoid excess voltages when the high voltage transformer of an X-ray generator is switched on. The circuit includes a second thyristor connected in series with a damping resistor and coupled in parallel with the starting thyristor for the X-ray tube. Said second thyristor is turned on simultaneously with the high-voltage starting signal, while the first (starting) thyristor (without a series-connected resistor) is turned on with a certain delay. This delay increases as the tube current decreases. Thus, excessive voltages during switching on can be eliminated independently of the value of the tube current with the addition of only a single damping resistor and a thyristor.

Abstract: In an X-ray generator with dose rate control, useful for both tomographic exposures, i.e., exposures with a fixed, preset exposure time, and also for Bucky exposures when different limit times are preset for given organs; including a tube power control which prevents the tube limit power from being exceeded during dose rate control. During tube power control, the current and the voltage are changed in opposite directions with respect to each other, so that the dose rate can be changed while the tube power remains constant.

Abstract: The exposure time in X-ray generators comprising a high-voltage generator which is actuated on the primary side is shorter than the actuation time on the primary side. This is because the high-voltage on the secondary side can follow the voltage on the primary side only at a given delay due to the stray inductance of the transformer. The effective exposure time (i.e. the time during which the X-ray tube emits the desired radiation), consequently, is shorter than the exposure time which is adjusted on the control panel, the reduction also being dependent of the tube current. So as to achieve that the effective exposure time is equal to the exposure time adjusted on the control panel, means are provided which prolong the actuation time in dependence of the exposure current.

Abstract: The invention relates to a time-measuring device for an X-ray generator comprising an automatic exposure device. The measurement of the actuation time which is controlled on the primary side by an automatic exposure device is inaccurate because the effect exposure time, which is the time during which the X-ray tube emits the desired radiation, is shorter than the actuation time in the primary circuit. This is due to the fact that, because of the always present stray inductances and cable capacitances etc., the high-voltage on the secondary side can follow the voltage on the primary side only with a given delay. For the accurate measurement of the effective exposure time, therefore, the actuation time is reduced by an amount which is dependent of the exposing tube current.