Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Reexamination Certificate
1999-11-08
2001-07-10
Patel, Rajnikant B. (Department: 2838)
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
C363S021070, C363S037000
Reexamination Certificate
active
06259610
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a circuit arrangement for connecting an electrical consumer to an alternating voltage source, wherein the electrical consumer is connected in series with a switch actuator and the switch actuator is associated with an electronic circuit whose direct voltage supply is carried out by the switch actuator.
2. Prior Art
Circuit arrangements of this generic type are known. These are used in residential wiring, for example, where electrical consumers are intended to be variably controllable by way of a bus and the wiring is carried out in a so-called two-wire technique (phase is connected through, no neutral conductor). A typical application example is the switching on and off of a light. Triacs or thyristors are used in a known manner as switch actuators which, in the alternating voltage circuit, can be brought into a high-impedance (off) state or a low-impedance (on) state as possible switching states. These are triggered by way of an electronic circuit which receives its direct voltage supply from the triac or the thyristor. If the triac or the thyristor is in the high-impedance state, a circuit for generating constant voltage, as a direct voltage source for the electronic circuit, is supplied with power via a capacitive or inductive series resistor. Usually Zener diodes or reference diodes are used as constant voltage generators in this connection.
In order to trigger the electrical consumers, the triac or the thyristor, when in the low-impedance state, are operated in phase-angle control, i.e. with each half-wave of the alternating voltage, the thyristor or the triac is connected through when the corresponding voltage required for this triggering has built up in the constant voltage generator.
In the known circuit arrangement, it is disadvantageous that in the high-impedance state of the switch actuator, only a relatively low current is available to the electronic circuit and this current is limited by the internal resistance of the electrical consumer. The higher the internal resistance of the electrical consumer, the lower the available power. It is also disadvantageous that in the low-impedance state of the switch actuator, the phase-angle control withholds a significant portion of the available voltage and therefore power from the electrical consumer. As a result of this, the electrical consumer cannot achieve its nominal power, particularly when it has a relatively low nominal power.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved circuit arrangement for connecting an electrical consumer to an alternating voltage source, which does not suffer from the above-described disadvantages.
According to the invention the circuit arrangement for connecting an electrical consumer to an alternating voltage source comprises a switch actuator connectable in series with the electrical consumer and an electronic circuit associated with the switch actuator and supplied with a direct voltage by means of it. The switch actuator includes a rectifier for supplying the direct voltage to the electronic circuit, a transformer comprising a secondary winding supplying power to the rectifier, a low inductance first primary winding and a high inductance second primary winding as well as switching means actuatable by the electronic circuit to switch between the two primary windings. Another switching means (
44
) is connected in parallel with the first primary winding (
26
) in order to short-circuit it for a predetermined short-circuit duration as a function of a nominal power consumed by the consumer.
The circuit arrangement according to the invention offers the advantage that the supply of direct voltage for the electronic circuit associated with the switch actuator is improved, particularly in the high-impedance state of the switch actuator, and that at the same time, the switch actuator and devices connected to it can be operated in a stable manner using the two-wire technique. Since the switch actuator includes a transformer which has two switchable primary windings that can be connected in series with the electrical consumer, wherein a first primary winding has a low inductance and a second primary winding has a high inductance and the secondary winding has a rectifier for producing the direct voltage supply, it is advantageously possible on the one hand to supply the direct voltage as a protection low voltage since the transformer produces a galvanic decoupling from the primary and therefore load circuit and on the other hand by switching between the two primary windings, to determine the high-impedance or low-impedance state of the switch actuator. In the high-impedance state, which corresponds to the off state of the electrical consumer, a relatively high internal resistance can be achieved in accordance with the inductance of the primary winding associated with the high-impedance state so that it is also possible to operate electrical consumers with very low nominal power.
In a preferred embodiment of the invention the provision is made that the primary winding, which determines the low-impedance state and consequently the on state of the electrical consumer, can be short circuited by a switching means, wherein the short circuit of the primary circuit can be adjusted as a function of a nominal power of the electrical consumer to be switched. This advantageously achieves the fact that by means of the circuit arrangement, electrical consumers can be switched, which have different nominal powers lying in a relatively large dispersion range, without overloading the transformer of the switch actuator.
In another preferable embodiment of the invention, the provision is made that the primary windings can be switched by a switching means which is actuated by the electronic circuit associated with the switch actuator. As a result of this, it is possible to actuate the switching means for switching between the primary windings at any time, independent of the switching state of the switch actuator since the actuation takes place by means of the electronic circuit whose direct voltage supply is carried out independent of the switching state of the switch actuator.
Other advantageous embodiments of the invention ensue from the remaining features disclosed in the dependent claims.
REFERENCES:
patent: 3887838 (1975-06-01), Thurston
patent: 4222086 (1980-09-01), Runyon
patent: 4443712 (1984-04-01), Gokita
patent: 5600546 (1997-02-01), Ho et al.
patent: 5831349 (1998-11-01), Weng
patent: 2 099 243 (1982-12-01), None
patent: 96/07239 (1996-03-01), None
Frei Martin
Karl Matthias
Patel Rajnikant B.
Robert & Bosch GmbH
Striker Michael J.
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