US 5,345,267 AGranted

AKB apparatus with hot start flash prevention

AssigneeThomson Consumer Electronics, Inc.

InventorAndrew K. Flickner

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Abstract

A receiver includes a kinescope, a driver amplifier and an integrated automatic kinescope bias (AKB) circuit. A soft start circuit includes a timing capacitor, external to the integrated circuit, and a control circuit within the integrated circuit which limits the AKB current adjustment range during turn-on to a time determined by the external capacitor. The capacitor is effectively isolated from the integrated circuit to prevent discharge thereof by protection diodes of the IC whereby the time constant of the overall AKB circuit is substantially the same for both hot start conditions and cold start conditions thereby avoiding undesirable visual start-up artifacts such as black level and contrast shifts during warm-up of the kinescope for either a cold start condition or a hot start condition.

Claims4

Dependent claims

AKB apparatus, for use with a kinescope driver amplifier, comprising:

an AKB control loop formed in an integrated circuit and including a first pin for connection to a current sensing resistor in said kinescope driver amplifier, having a second pin for supplying an AKB correction current to said kinescope driver amplifier and having a third pin for connection to a loop integration capacitor external to said integrated circuit;
an AKB range control switch formed in said integrated circuit and coupled to a point in said control loop for controlling the maximum value of said AKB correction current;
a threshold detector formed in said integrated circuit for controlling said range control switch, said detector having an input coupled to a fourth pin of said integrated circuit;
and
a soft start timing network, connected to said fourth pin and external to said integrated circuit, and including an RC network and a diode for coupling said network to said fourth pin of said integrated circuit.

2 more elements

Dependencies are inferred from the claim text.