Electric power conversion systems – Current conversion – Including an a.c.-d.c.-a.c. converter
Patent
1996-11-11
1998-04-14
Berhane, Adolf
Electric power conversion systems
Current conversion
Including an a.c.-d.c.-a.c. converter
363 39, 315224, H02M 5458, H05B 3702
Patent
active
057400210
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to switching power supplies for operating electric lamps connected to an alternating voltage mains network or a direct voltage source, and more particularly to a radio noise suppression circuit thereof.
BACKGROUND
Switching power supplies are suitable both for operating discharge lamps, especially fluorescent lamps and high-pressure lamps, and for operating incandescent lamps, such as low-voltage incandescent halogen lamps. Switching power supplies for operating discharge lamps are generally called electronic ballast devices (EBDs), while for low-voltage incandescent halogen lamps, the term electronic transformer or electronic converter is conventional.
Switching power supplies supplied by an alternating voltage mains network are also known as on-line switched-mode power supplies. If a switched-mode power supply is connected to a direct voltage source, such as a battery, then it can also be called an off-line switch-mode power supply. It is also possible to connect two or more switching power supplies in the manner of a cascade circuit; the output of a preceding power supply is then connected to the input of the next power supply, and so forth. In European Patent Disclosure EP-A 0 485 865, for instance, a circuit arrangement for operating a discharge lamp is shown. The circuit arrangement is supplied from a direct voltage source, such as an on-board electrical system of a motor vehicle, and has a step-up converter (upward controller) and optionally a downstream inverter for operating a discharge lamp with alternating current (AC).
One essential feature of switching power supplies is at least one switching portion having one or more fast switches--for which fast switching transistors are used as a rule. The switching portion may--for instance as explained in W. Hirschmann and A. Hauenstein, Schaltnetzteile in the form of a choke converter (downward, upward, or upward-downward controller, inverter), flyback converter, forward converter, or push-pull converter (in half- and full-bridge circuit). The switching portion converts the voltage at its input, such as the rectified mains voltage or the output voltage of a preceding converter, into a high-frequency switched voltage. Especially in the region of the switches, this creates fast potential changes relative to the grounded housing mass (protection class I devices) or the environment or ground (protection class II devices). Via capacitive couplings, the electrical fields, which vary over time, connected to the potential changes can affect common-mode noise, or interference, which for instance flows over the mains supply leads and through the switching power supply. The noise loop is closed via parasitic capacitances especially between the switching portion and ground. A detailed description of how radio noise arises can be found for instance Supplies!, Siemens AG, Berlin, 1990, page 72 ff. With respect to the limit values for radio noise in switching power supplies, VDE Specification 0871, and especially for electrical operating devices for lamps, VDE 0875--which corresponds to International Standard CISPR 15--must be adhered to.
One conventional provision to suppress common-mode noise is to incorporate an interference suppression filter, such as a current-compensated choke, into the mains supply leads. The design of current-compensated chokes is explained for instance in O. Kilgenstein, Schaltnetzteiie in der Praxis 1986, p. 355 ff. Its effect is based on the fact that the mains-frequency useful current can pass through undamped. High-frequency common-mode noise, conversely, is filtered out by the high inductance of the current-compensated choke. However, there are limits to compact structure, since the interference-suppressing action of a current-compensated choke can be reduced by immediately adjacent components and their noise signals or even--especially because of magnetic interference fields--be converted into an opposite kind of action.
In protection class I devices, Y capacitors can additionally be conn
REFERENCES:
patent: 4612480 (1986-09-01), Kneisel
patent: 4625270 (1986-11-01), Taylor
patent: 4792887 (1988-12-01), Bernitz et al.
patent: 4862041 (1989-08-01), Hirschmann
patent: 5111373 (1992-05-01), Higaki
patent: 5610479 (1997-03-01), Schmitt
"Schaltnetzteile" (Switched-Mode Power Supplies), Siemens AG, Berlin, 1990, . 72 et seq.
"Schaltnetzteile in der Praxis" (Switched-Mode Power Supplies in Practice) Vogel Buchverlag, Wurzburg, 1986, p. 355 et seq.
Lecheler Reinhard
Raiser Franz
Berhane Adolf
Patent-Treuhand-Gesellschaft fur Elektrische Gluehlampen mbH
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