R. Stahl Schaltgerate Gmbh

Stahl Schaltergate Gmbh

Fritz Frey

Manfred Kaiser

Jorg Stritzelberger

Michael STÄHLE

A circuit arrangement for enforcing an intrinsically safe situation in a hazardous zone features a first switching device that lies in the series arm and a second switching device that lies in the shunt arm. If a fault occurs that would violate the conditions of intrinsic safety, the first switching device is initially blocked and the second switching device is switched through with a time delay such that the output terminals are mutually short-circuited. In addition, a monitoring device is provided for monitoring the load conditions at the switching device arranged in the series arm.

Circuit arrangement for limiting a voltage

A power-supply includes a power-supply input. A transformer has a primary winding and a secondary winding separated galvanically from the primary winding. A controlled semiconductor switch has a control input in series circuit with the primary winding, which lies parallel to the power-supply input. A controllable control circuit for the semiconductor switch delivers a periodic control signal, which is controlled such that the output voltage on the secondary winding is kept at a desired value independent of the load, to the semiconductor switch. A voltage limiting circuit lies parallel to the input side of the primary winding. An output signal of the voltage limiting circuit acts on the switch state of the semiconductor switch to move the semiconductor switch to a stationary state, in which it generates no alternating current on the primary winding, when the voltage on the primary winding has exceeded a specified limiting value.

Power supply with galvanic isolation

A blocking-oscillator-type converter circuit works with a transformer that has only one primary winding and one secondary winding. The transformer contains no reaction coupling winding for the blocking oscillator. The control voltage for the oscillator is derived from the primary voltage of the transformer, that is, during the free-running phase. Furthermore, a voltage monitoring circuit is provided that works independent of the oscillator, inhibiting the output voltage of the oscillator when the voltage on the output of the blocking-oscillator-type converter is too large. A current monitoring circuit works independent of the oscillator and the voltage monitoring circuit and inhibits the pulses for the power transistor when the current on the output side exceeds a specified amount.

Power supply having a voltage monitoring circuit

According to the invention, a blocking oscillator type converter circuit functions with a transformator that only comprises a primary winding and a secondary winding. Said transformator does not comprise a return coupling winding for the blocking oscillator. The control voltage of the oscillator is derived from the primary voltage of the transformator during the free-wheeling phase. The invention also relates to a voltage monitoring circuit that works independently from the oscillator, the output voltage of the oscillator being repressed when the voltage on the output of the blocking oscillator is too high. A flow monitoring circuit functions independently from the oscillator and the voltage monitoring circuit and suppresses the impulses for the power transistor when the power on the output side exceeds a predetermined measurement.

Power supply arrangement with output flow monitoring

A circuit arrangement includes a current measuring or temperature measuring device, used for triggering a shunt device. Said shunt device produces a short-circuit, which directly leads to the blowing of a fuse. The arrangement is modular and allows the operation of several current measuring devices on a common shunt device. Said arrangement is specifically adapted to prevent a protection resistor from warming up to too high a surface temperature in the case of an error, because the current is flowing for too much time.

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Kunzelsau, Germany

Fritz Frey