Power supply having on-off control

Claim 2

A power supply for a video display apparatus comprising: a source of unregulated voltage; regulator means incorporating a controllable switch means having an input terminal coupled to said source of unregulated voltage, an output terminal and a control terminal responsive to an input signal for rendering said switch means conductive; a capacitor coupled to said switch means output terminal; start-up means coupled to said switch means control terminal and responsive to a selectable video display apparatus enabling signal for applying a temporary input signal to said control terminal for rendering said switch means conductive such that a voltage is established across said capacitor; and means responsive to said voltage across said capacitor for applying normal input signals to said control terminal, said start-up means being responsive to said voltage across said capacitor for becoming disabled.

Claim 3

The arrangement defined in claim 1, wherein said controllable switch means comprises an SCR.

Claim 4

The arrangement defined in claim 1, wherein said start-up means comprises a transistor, said transistor being rendered conductive in response to said selectable video display apparatus enabling signal for conducting current to said switch means control terminal.

Claim 5

A power supply for a video display apparatus comprising: a source of unregulated voltage; an SCR having a first terminal coupled to said source of unregulated voltage, a second terminal and a gate terminal; a capacitor coupled to said second terminal of said SCR; a start-up circuit coupled to said gate terminal of said SCR comprising: means responsive to video display apparatus enabling signal for providing an output signal; means incorporating a switch for applying said output signal to said gate terminal of said SCR for causing conduction of said SCR such that the voltage across said capacitor increases; circuit means responsive to the voltage developed across said capacitor for generating a first supply voltage; regulator control means responsive to said first supply voltage for providing a gating signal to said gate terminal of said SCR for controlling the conduction of said SCR for maintaining said voltage across said capacitor at a predetermined level, said predetermined level sufficient to cause said switch to change conduction states in order to disable said output signal generating means of said start-up circuit.

Claim 6

A power supply for a video display apparatus comprising: a source of unregulated voltage; an SCR having a first terminal coupled to said source of unregulated voltage, a second terminal and a gate terminal; a capacitor coupled to said second terminal of said SCR; a start-up circuit coupled to said gate terminal of said SCR comprising: means responsive to video display apparatus enabling signal for providing an output signal; means incorporating a switch for applying said output signal to said gate terminal of said SCR for causing conduction of said SCR such that the voltage across said capacitor increases; circuit means responsive to the voltage developed across said capacitor for generating a first supply voltage; regulator control means responsive to said first supply voltage for providing a gating signal to said gate terminal of said SCR for controlling the conduction of said SCR for maintaining said voltage across said capacitor at a predetermined level, said predetermined level sufficient to cause said switch to change conduction states in order to disable said output signal generating means of said start-up circuit.

Claim 7

The arrangement defined in claim 4, wherein said means for providing said output signal comprises a transistor having its conduction state controlled in response to said video display apparatus enabling signal.

Claim 8

The arrangement defined in claim 4, wherein said switch comprises a transistor rendered conductive in response to said output signal for conducting current to said gate terminal of said SCR.

Claim 9

The arrangement defined in claim 4, wherein said predetermined voltage across said capacitor is sufficient to render said switch nonconductive even in the presence of said output signal.