Abstract: An LLC power converter has an output voltage which is determined by a frequency controller controlling the frequency of an on and off switching of the switches (5, 6) of the converter. In order to stabilize the output voltage at varying output currents, a control circuit feeds back the variation of the total current (I) in the converter to the frequency controller (22, 25) for correcting the frequency of the on and off switching of the switches.

Abstract: The present invention provides for a switched mode power supply having an input for receiving an input signal voltage, a flyback converter circuit arrangement and an output for delivering a regulated output signal voltage, and including a boost converter arranged to be operatively combined with the said flyback converter, and functioning such that the combined converter operates in a boost mode when the input voltage is above a threshold value, and in a flyback mode when the input voltage is below the threshold value.

Abstract: A half-bridge circuit which is operated as a double down-converter is equipped with a second inductor and power feedback capacitors and diodes. The power factor of the circuit is substantially improved thereby.

Abstract: A viscometer provided with a transducer for converting a viscosity parameter of a fluid into an electrical signal. The transducer comprises a container, provided with a cavity for the fluid to be measured, a support element firmly connected thereto and an oscillatory device, which at one end is firmly attached to the support element and at the other end has an oscillatory body. An oscillation drive coil powered by alternating current and a constant magnetic field device for generating a constant magnetic field are provided for bringing and maintaining the oscillatory body in oscillation. The transducer is provided with a detection device for detecting the oscillation of the oscillatory body. The constant magnetic field device is arranged such that it is not able to come into contact with the fluid to be measured and the constant magnetic field lines generated by said device are directed towards the oscillatory body.

Abstract: A rotary regenerative air preheater has electromagnetic drive devices to adjust the relationship between an end face of the regenerative mass and a sealing frame on a duct part. Electrical control means are responsive to signals generated by contact between the sealing shoe (or special sensors) borne on the frame and the end face, to drive the electromagnetic devices and break the contact. The control may be on/off, a time response such that a desired maximum clearance is experienced, or may be responsive to drag (i.e., the angle of arc over which contact is experienced). The electromagnetic drive devices are inherently self adjusted by having an air gap in their flux circuit which varies in dependence on the position of the sealing frame.