TDA8145 pillow calibration circuit

Relevant key device information applied in this article: TDA8145 A940 TDA8145 is a widely used pincushion correction dedicated IC. Its basic working principle is as follows: The field sawtooth wave voltage is sent to pin (2) of N551 through C592 and R550, and then passes through the IC. After internal amplification and limiting and waveform processing, an upward convex field frequency parabolic wave voltage is formed at pin 7. At the same time, it is added to the inverting input terminal of the internal operational amplifier and the horizontal frequency sawtooth wave voltage input to pin 8 is calculated and driven by inversion. It is then output by the 5th pin of N551, forming a concave field parabola voltage (a horizontal pulse whose amplitude is modulated by the field frequency parabola voltage). After amplification of this voltage V551, the field parabola voltage is output through L561. VR552 in the picture is a pillow-type distortion correction amount adjustment potentiometer. Adjusting it essentially changes the amount of negative feedback from the N551's pin 5 output signal to pin 7, and also changes the parabolic wave voltage amplitude output by pin 5, so that The correction amount is moderate to keep the grating in a rectangular shape without distortion. VR553 is the horizontal amplitude adjustment potentiometer. The horizontal pulse signal sent from the horizontal output transformer is cut by R562 and VD563 to form a pure 18Vp-p pulse. After being adjusted by VR553, the horizontal sawtooth wave voltage is formed by the integral action of VD551 and C556. Add it to pin 8 of IC361 and adjust VR553 to change the amplitude of the input pulse at pin 8, which also changes the electrical amplitude of the horizontal pulse output by pin 5. VR551 is a grating trapezoidal distortion correction potentiometer. Adjusting it changes the DC potential of pin 1 of N551, thereby changing the parabolic wave slope of the internal op amp output, achieving the function of correcting trapezoidal distortion.