Active offset for power factor controller

Claim 2

A switch mode power supply, comprising: a current source for producing current; output means responsive to said current for providing an output voltage; switch means for conditioning current supplied to said output means; control means responsive to a control signal for controlling conditioning by said switch means of current supplied to said output means; and sensing means for producing said control signals, said control signal including a sensed signal representing current flow through said switch means and a varying offset based on the output voltage of said output means.

Claim 3

The switch mode power supply of claim 1, wherein said current source includes inductor means controlled by to said switch means for supplying the current to said output means.

Claim 4

The switch mode power supply of claim 1, wherein said output means includes at least one capacitor across which said output voltage is developed.

Claim 5

The switch mode power supply of claim 1, wherein said control means comprises a power factor controller serving to control the power supply power factor.

Claim 6

The switch mode power supply of claim 2, wherein said control means comprises a power factor controller serving to control the power supply power factor.

Claim 7

In a ballast for a discharge lamp, a preconditioner for regulating a D.C. voltage comprising: a current source for producing current; output means responsive to said current across which said regulated D.C. voltage is applied; switch means for diverting current away from said output means; control means responsive to a control signal for controlling said switch means; and sensing means for producing said control signal, said control signal including a sensed signal representing current flow through said switch means and a varying offset based on the regulated D.C. voltage.

Claim 8

In a ballast for a discharge lamp, a preconditioner for regulating a D.C. voltage comprising: a current source for producing current; output means responsive to said current across which said regulated D.C. voltage is applied; switch means for diverting current away from said output means; control means responsive to a control signal for controlling said switch means; and sensing means for producing said control signal, said control signal including a sensed signal representing current flow through said switch means and a varying offset based on the regulated D.C. voltage.

Claim 9

The preconditioner of claim 6, wherein said current source includes inductor means controlled by said switch means for supplying the current to said output means and said output means includes at least one capacitor across which said regulated D.C. voltage is applied.

Claim 10

The preconditioner of claim 6, wherein said offset is directly proportional to said regulated D.C. voltage.

Claim 11

The preconditioner of claim 6, wherein said sensing means includes zener diode means having a cathode which varies between a low voltage level and a high voltage level based on the regulated D.C. voltage at said output means.

Claim 12

The preconditioner of claim 9, wherein the voltage at said cathode is directly proportional to said regulated D.C. voltage.

Claim 13

The preconditioner of claim 6, wherein the magnitude of said offset varies between two levels.

Claim 14

A ballast for a discharge lamp, comprising: an input terminal for connection to a source of voltage for the lamp ballast, a current source coupled to said input terminal and operative to produce a current, output means for connection to said discharge lamp and responsive to said current to provide an output voltage, switch means for controlling the current supplied to said output means, power factor control means responsive to a control signal for controlling the switch means so as to control the power factor of said ballast; and sensing means for producing said control signal which includes a sensed signal added to a varying offset that varies as a function of the output voltage.

Claim 15

A ballast for a discharge lamp, comprising: an input terminal for connection to a source of voltage for the lamp ballast, a current source coupled to said input terminal and operative to produce a current, output means for connection to said discharge lamp and responsive to said current to provide an output voltage, switch means for controlling the current supplied to said output means, power factor control means responsive to a control signal for controlling the switch means so as to control the power factor of said ballast; and sensing means for producing said control signal which includes a sensed signal added to a varying offset that varies as a function of the output voltage.

Claim 16

The ballast of claim 12, wherein said output voltage is a DC voltage and said offset increases when said D.C. voltage output rises above a predetermined voltage level.

Claim 17

The ballast of claim 13, wherein said offset varies between a low level and a high level at said predetermined voltage level.

Claim 18

The ballast of claim 14, wherein said high level is approximately at least five times greater in magnitude than said low level.

Claim 19

The ballast of claim 12, wherein said sensed signal includes a first component that represents a current that flows only through said switch means and a second component that represents a current from said input terminal.

Claim 26

A regulated power supply with power factor control comprising: an input terminal for connection to a source of unregulated supply voltage, at least one output terminal for connection to a load, a supply capacitor coupled to the one output terminal, a converter circuit coupled between said input terminal and said one output terminal for producing a load current and a regulated voltage at the one output terminal, said converter circuit including at least an inductor, a diode and a controlled semiconductor switch, switch control means responsive to a control signal thereby to control the switching of said semiconductor switch in a manner so as to control current flow through said inductor, and means for deriving a first signal component of said control signal indicative of a current flowing through said semiconductor switch and a second signal component of said control signal comprising an active offset signal that varies as a function of the voltage at said output terminal.

Claim 27

A regulated power supply with power factor control comprising: an input terminal for connection to a source of unregulated supply voltage, at least one output terminal for connection to a load, a supply capacitor coupled to the one output terminal, a converter circuit coupled between said input terminal and said one output terminal for producing a load current and a regulated voltage at the one output terminal, said converter circuit including at least an inductor, a diode and a controlled semiconductor switch, switch control means responsive to a control signal thereby to control the switching of said semiconductor switch in a manner so as to control current flow through said inductor, and means for deriving a first signal component of said control signal indicative of a current flowing through said semiconductor switch and a second signal component of said control signal comprising an active offset signal that varies as a function of the voltage at said output terminal.

Claim 28

A power supply as claimed in claim 20 wherein said deriving means produces an offset signal of sufficient magnitude to significantly affect switching of the semiconductor switch only during a no-load or light load condition.

Claim 29

A power supply as claimed in claim 20 further comprising means responsive to an input current flowing through said input terminal for deriving a third signal component of said control signal which is operative to cause the switch control means to switch on the semiconductor switch when the input current is approximately at zero level.

Claim 30

A power supply as claimed in claim 20 wherein said deriving means produces an offset signal of sufficient magnitude to significantly affect switching of the semiconductor switch at a predetermined voltage threshold level of the supply capacitor voltage.

Claim 31

A power supply as claimed in claim 20 wherein said first signal component is indicative only of a current flowing through said semiconductor switch and said control signal is substantially independent of the source of supply voltage whereby the switch control means adjusts the switching frequency of the semiconductor switch and produces asynchronous operation thereof.

Claim 32

A power supply as claimed in claim 20 wherein said deriving means derives third and fourth signal components of said control signal indicative of an input current flowing through said input terminal and of an input voltage at said input terminal, respectively.