Friwo Mobile Power Gmbh

Friwo Geraetebau Gmbh

Arno Reinhard

Rüdiger Malsch

Armin Wegener

Ralf genBerghegger Schr&ouml;eder

Ralf Gennant Berghegger Schroder

The present invention relates to a control circuit for controlling the output power of a primary-controlled switched mode power supply unit, which comprises a primary switch and a transformer with an auxiliary winding. Within the auxiliary winding, voltage pulses are induced by primary-sided switching operations, which can be taken into account when controlling the output power. In order to provide an improved control and an enhanced flexibility with respect to the operational parameters, the sampling instance is determined based on the duration of the voltage pulse at the auxiliary winding during a previous switching cycle. In order to detect a defective contact between the auxiliary winding and the control circuit in a particularly simple and secure manner, the negative voltage pulse at the auxiliary winding occurring when the switch is closed may be used for confirming a proper connection. In order to optimize the switching off process of the switch and to reduce power losses, the output power may be controlled by comparing the current through the primary winding with two threshold values.

Control circuit for switched mode power supply unit

A charging system is used for contactless transfer of electric power from a charging unit to a mobile unit. The system includes a first substantially U-shaped ferrite core which is operable to be located within the charging unit. The first core includes a base area and two leg areas. Each leg area of the first core includes a pole face. A first winding is arranged on the base area of the first ferrite core. The system also includes a second substantially U-shaped ferrite core which is operable to be located within a mobile unit. The second core includes a base area and two leg areas. Each leg area of the second core includes a pole face. A second winding is arranged on the base area of the second ferrite core. The first ferrite core has larger cross-sectional dimensions than the second ferrite core.

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Münster, Germany

Arno Reinhard