| 摘要 |
In a television receiver, a dynamic, parabolic correction voltage for focusing is generated by means of a transformer whose primary winding is fed with the line deflection current or a line-frequency voltage and to whose secondary winding a capacitor is connected, which capacitor integrates the sawtooth-waveform current in the secondary winding into a parabolic voltage. New types of picture tubes require a correction voltage which does not have a parabolic profile, rather whose form corresponds approximately to the cross section through the centre of a bathtub. It is an object to provide a simple circuit for generating such a bathtub-waveform correction voltage. This is achieved by virtue of the fact that a frequency-dependent network, in particular a series resonant circuit comprising an inductance (L) and a capacitance (C), is connected in parallel with the capacitor (Co), which network is tuned in such a way that the network effects an additional sinusoidal current (IL/C) with a period duration approximately equal to the line trace period (TH). The circuit is particularly simple, requires no active elements, effects a low power loss, can be used with a current transformer and furthermore enables blanking of the correction voltage during the vertical blanking interval.
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