Integration of Vertical Dynamic Focus Voltage Generation and EW Drive
Publication Date: 2005-Dec-22
The IP.com Prior Art Database
Title: Integration of Vertical Dynamic Focus Voltage Generation and EW Drive
DAF stands for Dynamic Astigmatism Focusing, which is used in some picture tube for better focusing performance.
Current DAF circuitry only produces the horizontal voltage, which is about 761Vpp (parabola voltage) for 32" Wide Screen Real Flat (32wsrf) picture tube - assuming that the horizontal deflection current is constant throughout the whole screen. However, this is not the case as EW pin- cushion correction is needed for most of the picture tubes.
This voltage is usually produced by a DAF transformer that is connected in series with the deflection yoke of the picture tube.
This configuration is not optimum because the deflection yoke current is maximum at the centre of the screen due to EW pin-cushion correction. This resulted in higher peak to peak parabolic voltage at the centre of the screen, instead of having it at the four corners of the picture tube. Therefore, the current DAF circuitry is a compromise of the optimal DAF voltage needed by the picture tube.
The optimum parabolic voltages for 32wsrf picture tube are 761Vpp at the centre of the screen, and 903Vpp at the top and bottom of the screen. The extra 142Vpp parabolic waveform is the vertical DAF modulation voltage.
For vertical parabolic voltage generation, another active circuit needs to be used and that required at least two power transistors. This is costly.
This problem can be solved by integrating the EW drive circuit into the DAF circuitry and provides the added advantage of generating the vertical DAF voltage. There is no need for new components -- only reconfiguration of...