03260329| Datasheet

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Chokes for Power Lines Sine-Wave Chokes
General In switch-mode power supplies, the line input current is not a sine-wave curve like the line voltage but is pulse-shaped. This current function puts a load on the power supply network and distorts the network's voltage curves. With the aid of a "pump circuit" built up around a "sine-wave choke", it is possible to modify switch-mode power supplies to become "sine-wave power supplies" so that they meet the permitted limits for Class-D devices.

Current and voltage curves
VR R Icp UN ,, IN ,, NP VR UN IR N Icp NP

SSB1474-N

Fig. 1 Graph of the voltage VR (sine-shaped) and the mains input current. IR shows the pulse-shaped input of a standard switch-mode power supply, Icp is the current graph of a switch-mode power supply with "current pump", showing the reduced level of upper harmonic components.

For several years there have been attempts to produce switch-mode power supplies with a more sine-shaped input current characteristic. In this connection, the standard EN 61000-3-2 is presently being drafted. This prescribes limits for the harmonics of the input current and all new devices and appliances will have to be equipped with power supplies which comply with this standard. Television sets come under Class D of this standard. The standard is to apply to all devices with a power consumption of more than 75 W. At a later date, the power consumption limit under which the standard is to apply is to be lowered to 50 W.

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