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Fast Recovery Horizontal Deflection Circuit

IP.com Disclosure Number: IPCOM000062737D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

DeBar, DE: AUTHOR [+2]

Abstract

Conventional bipolar transistors which are used in highly tal deflection circuits for CRT displays suffer inductive horizontal deflection circuits or CRT displays suffer from an impaired switching speed and forward voltage drop, rendering them a less than optimum choice for the application.

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Fast Recovery Horizontal Deflection Circuit

Conventional bipolar transistors which are used in highly

tal deflection circuits for CRT displays suffer inductive horizontal deflection circuits or CRT displays suffer from an impaired switching speed and forward voltage drop, rendering them a less than optimum choice for the application.

An improved horizontal deflection circuit having fast recovery characteristics can be obtained by substituting a Hexfet of the VMOS power FET type for the conventional bipolar switching transistor in horizontal deflection circuits. An example of such an application is shown in the circuit diagram of the figure. The Hexfet 2 is driven by the deflection amplifier 6 to switch conduction between ground potential and horizontal deflection coil 4, whose opposite side is connected to the positive V potential. Hexfets are particularly good to use in place of bipolar transistors because of their low on resistance of ap- proximately
0.4 ohms, their high breakdown voltage of approxi- mately 500 volts, their fast switching turn-on delay of approxi- mately 80 nanoseconds and turn-off delay of approximately 400 nanoseconds. Hexfets typically can handle high currents on the order of 10 amps. As an additional feature, the parasitic shunt diode which is an inherent feature in Hexfet devices, can be used as the flyback diode in the horizontal deflection circuit. This dual function feature provides for the elimination of the need for any off drive circ...