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US 4,233,635 AGranted
High voltage limiting circuit for a television receiver
AssigneeSony Corporation
InventorMasao Suzuki
Life of this patent
Estimating the term…
Abstract
A high voltage limiting circuit for a television receiver employs a negative pulse sample from a tertiary winding on a flyback transformer as a measure of high voltage. When the amplitude of the negative pulse sample exceeds a predetermined value, indicating excessive high voltage, a limiting circuit applies a voltage to an automatic frequency control input of a horizontal oscillator to increase the frequency of the horizontal oscillator. The increased frequency limits further increase in high voltage.
Claims5
A high voltage limiting circuit for a television receiver comprising:
- a horizontal oscillator for providing an output pulse having a frequency controlled by an automatic frequency control voltage;
- an output circuit driven by said output pulse from said horizontal oscillator to provide an output pulse signal;
- a fly-back transformer having a primary winding receiving said output pulse signal from said output circuit, a secondary winding and a tertiary winding;
- a high voltage rectifying circuit connected to said secondary winding of said fly-back transformer;
- a source of a reference potential;
- a voltage divider connected between said tertiary winding and said source of reference potential;
- a constant voltage device;
- and
- a transistor having an emitter connected to said source of reference potential, a base connected to said voltage divider through said constant voltage device and a collector connected to add a voltage to said automatic frequency control voltage controlling said frequency of said horizontal oscillator;
- said tertiary winding of said fly-back transformer being wound to produce a negative pulse and said reference potential being a positive voltage whereby the added voltage is effective to control the frequency of said horizontal oscillator so as to reduce a high voltage obtained at said high voltage rectifying circuit when a voltage of said negative pulse exceeds a predetermined value.
7 more elements
A high voltage limiting circuit for a television receiver comprising:
- horizontal pulse means for producing a horizontal pulse having a variably controlled frequency;
- automatic frequency control means for producing an automatic frequency control voltage to control said frequency to a predetermined value;
- a fly-back transformer having at least a primary winding to which said horizontal pulse is fed, a secondary winding supplying the high voltage which is to be limited, and a tertiary winding providing a pulse having an amplitude related to said high voltage;
- a source of a reference potential;
- a voltage divider connected between said tertiary winding and said source of reference potential and having a voltage divider junction;
- a transistor having a base, emitter and collector;
- a constant voltage device connected between said voltage divider junction and said base of the transistor;
- said emitter of the transistor being connected to said source of reference potential;
- and a voltage at said collector of the transistor being applied to said horizontal pulse means together with said automatic frequency control voltage whereby said frequency is increased beyond said predetermined frequency when said high voltage exceeds a predetermined value.
6 more elements
A high voltage limiting circuit for a television receiver comprising:
- horizontal pulse generating means for producing a horizontal pulse having a variably controlled frequency;
- said horizontal pulse generating means having means for controlling said frequency so as to maintain the latter at a predetermined frequency in response to an automatic frequency control signal;
- fly-back means responsive to said horizontal pulse for generating a high voltage;
- means in said fly-back means for producing a pulse having a first polarity and an amplitude related to said high voltage;
- a source of a reference potential having a polarity opposite to said first polarity;
- divider means connected between said means for producing a pulse and said source of reference potential for producing a control signal when said amplitude exceeds a predetermined amplitude;
- a transistor having a collector-emitter path between said source of reference potential and said means for controlling said frequency, said transistor further having a base to which said control signal is applied and said transistor being effective to add a limiting signal to said means for controlling said frequency which is effective to increase said frequency above said predetermined frequency in relation to the amount by which the amplitude of said pulse exceeds said predetermined amplitude whereby said high voltage is limited.
4 more elements
Dependencies are inferred from the claim text.