Synch Lock for Vertical Deflection IC
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01
A circuit is disclosed for use in association with a fixed frequency commercial TV vertical deflection integrated circuit (IC) which enables the IC to be synchronized to a wide range of frequency about the fixed frequency. The IC is set to run freely, then the circuit applies synch pulses to stop the IC oscillator, and, lastly, applies modified synch pulses to reset the IC ramp generator directly. In CRT display design the most cost-effective vertical deflection is achieved with the aid of a commercial consumer TV IC. However, these devices are intended for use at fixed frame rates (UK 50 Hz, USA 60 Hz) and, as such, have a limited capture range of a few hertz about the free run frequency. The circuit to be described is a specific implementation for use with the Philips TDA1670A.