Control of the output power of a DC-DC converter upon varying the switching frequency

Claim 3

A method according to claim 1, wherein the step of generating the DC signal comprises generating the DC signal to have an amplitude inversely proportional to the frequency of the periodic signal.

Claim 4

A method according to claim 2, wherein the step of clamping comprises clamping the error amplifier at a voltage having an amplitude proportional to the amplitude of the generated DC signal.

Claim 5

A method according to claim 1, wherein the oscillator comprises a sawtooth oscillator; and wherein the step of detecting comprises detecting a sawtooth periodic signal from the sawtooth oscillator.

Claim 8

A method according to claim 5, wherein the step of generating the DC signal comprises generating the DC signal to have an amplitude inversely proportional to the frequency of the periodic signal.

Claim 9

A method according to claim 5, wherein the oscillator comprises a sawtooth oscillator; and wherein the step of detecting comprises detecting a sawtooth periodic signal from the sawtooth oscillator.

Claim 10

A current mode PWM controller comprising: an oscillator including a resistor and a first capacitor defining a resistor-capacitor (R-C) circuit coupled between a node at a reference voltage and ground; an error amplifier of an output voltage referred to a pre-established voltage; and a current control circuit comprising a current sensing resistor to be functionally connected in series with a power switch, and control means for controlling an output power by varying a switching frequency of the power switch, said control means comprising a detecting and generating circuit for detecting a periodic signal produced on the first capacitor of said R-C circuit and for generating a DC signal having an amplitude inversely related to a frequency of the periodic signal, and a clamp stage for clamping the output voltage of said error amplifier at a voltage level related to the DC signal.

Claim 11

A current mode PWM controller comprising: an oscillator including a resistor and a first capacitor defining a resistor-capacitor (R-C) circuit coupled between a node at a reference voltage and ground; an error amplifier of an output voltage referred to a pre-established voltage; and a current control circuit comprising a current sensing resistor to be functionally connected in series with a power switch, and control means for controlling an output power by varying a switching frequency of the power switch, said control means comprising a detecting and generating circuit for detecting a periodic signal produced on the first capacitor of said R-C circuit and for generating a DC signal having an amplitude inversely related to a frequency of the periodic signal, and a clamp stage for clamping the output voltage of said error amplifier at a voltage level related to the DC signal.

Claim 12

A current mode PWM controller according to claim 8, wherein the detecting and generating circuit further comprises a second capacitor for determining a time constant; wherein the current mode PWM controller comprises a completely integrated portion except for the second capacitor; and wherein the second capacitor is externally connectable to the completely integrated portion through a dedicated connecting pin.

Claim 13

A current mode PWM controller according to claim 8, further comprising a detecting diode having an anode; and wherein said detecting and generating circuit comprises a buffer amplifier functionally connected between the first capacitor and the anode of the detecting diode.

Claim 14

A current mode PWM controller according to claim 10, wherein said clamp stage comprises a PNP transistor having a base coupled to the detecting diode, a collector coupled to ground, and an emitter coupled to the output of the error amplifier.

Claim 15

A current mode PWM controller according to claim 11, further comprising two directly biased diodes connected in cascade between the output of the error amplifier and the emitter of the PNP transistor.

Claim 16

A current mode PWM controller according to claim 8, wherein the detecting and generating circuit comprises means for generating the DC signal to have an amplitude inversely proportional to the frequency of the periodic signal.

Claim 17

A current mode PWM controller according to claim 13, wherein the clamping stage comprises means for clamping the output of the error amplifier at a voltage having an amplitude proportional to the amplitude of the generated DC signal.

Claim 18

A current mode PWM controller according to claim 8, wherein the oscillator comprises a sawtooth oscillator.

Claim 19

A current mode PWM controller comprising: an oscillator including a resistor and a first capacitor defining a resistor-capacitor (R-C) circuit coupled between a node at a reference voltage and ground; an error amplifier of an output voltage referred to a pre-established voltage; and a current control circuit comprising a current sensing resistor to be functionally connected in series with a power switch and control means for controlling an output power by varying a switching frequency of the power switch, said control means comprising a detecting and generating circuit for detecting a periodic signal produced on the first capacitor of said R-C circuit and for generating a DC signal having an amplitude inversely related to a frequency of the periodic signal, and an offset circuit for offsetting a signal present on said current sensing resistor by a voltage corresponding to a difference between a constant voltage and the oscillator DC signal.

Claim 20

A current mode PWM controller comprising: an oscillator including a resistor and a first capacitor defining a resistor-capacitor (R-C) circuit coupled between a node at a reference voltage and ground; an error amplifier of an output voltage referred to a pre-established voltage; and a current control circuit comprising a current sensing resistor to be functionally connected in series with a power switch and control means for controlling an output power by varying a switching frequency of the power switch, said control means comprising a detecting and generating circuit for detecting a periodic signal produced on the first capacitor of said R-C circuit and for generating a DC signal having an amplitude inversely related to a frequency of the periodic signal, and an offset circuit for offsetting a signal present on said current sensing resistor by a voltage corresponding to a difference between a constant voltage and the oscillator DC signal.

Claim 21

A current mode PWM controller according to claim 16, wherein the detecting and generating circuit further comprises a second capacitor for determining a time constant; wherein the current mode PWM controller comprises a completely integrated portion except for the second capacitor; and wherein the second capacitor is externally connectable to the completely integrated portion through a dedicated connecting pin.

Claim 22

A current mode PWM controller according to claim 16, further comprising a detecting diode having an anode; and wherein said detecting and generating circuit comprises a buffer amplifier functionally connected between the first capacitor and the anode of the detecting diode.

Claim 23

A current mode PWM controller according to claim 16, wherein the detecting and generating circuit comprises means for generating the DC signal to have an amplitude inversely proportional to the frequency of the periodic.

Claim 24

A current mode PWM controller according to claim 19, wherein the offset circuit comprises means for offsetting the signal present on said current sensing resistor by a voltage corresponding to a difference between a constant voltage and the generated DC signal.

Claim 25

A power supply for a scanning circuit of a cathode ray tube operating at varying frequencies of synchronization and comprising: a static DC--DC converter comprising a current mode PWM controller, said current mode PWM controller comprising an oscillator including a resistor and a first capacitor defining a resistor-capacitor (R-C) circuit coupled between a node at a reference voltage and ground; an error amplifier of an output voltage referred to a pre-established voltage; and a current control circuit comprising a current sensing resistor to be functionally connected in series with a power switch and control means for controlling an output power by varying a switching frequency of the power switch, said control means comprising a detecting and generating circuit for detecting a periodic signal produced on the first capacitor of said R-C circuit and for generating a DC signal having an amplitude inversely related to a frequency of the periodic signal, and a clamp stage for clamping the output voltage of said error amplifier at a voltage level related to the DC signal.

Claim 26

A power supply for a scanning circuit of a cathode ray tube operating at varying frequencies of synchronization and comprising: a static DC--DC converter comprising a current mode PWM controller, said current mode PWM controller comprising an oscillator including a resistor and a first capacitor defining a resistor-capacitor (R-C) circuit coupled between a node at a reference voltage and ground; an error amplifier of an output voltage referred to a pre-established voltage; and a current control circuit comprising a current sensing resistor to be functionally connected in series with a power switch and control means for controlling an output power by varying a switching frequency of the power switch, said control means comprising a detecting and generating circuit for detecting a periodic signal produced on the first capacitor of said R-C circuit and for generating a DC signal having an amplitude inversely related to a frequency of the periodic signal, and a clamp stage for clamping the output voltage of said error amplifier at a voltage level related to the DC signal.

Claim 27

A power supply according to claim 21, wherein the detecting and generating circuit further comprises a second capacitor for determining a time constant; wherein the current mode PWM controller comprises a completely integrated portion except for the second capacitor; and wherein the second capacitor is externally connectable to the completely integrated portion through a dedicated connecting pin.

Claim 28

A power supply according to claim 21, further comprising a detecting diode having an anode; and wherein said detecting and generating circuit comprises a buffer amplifier functionally connected between the first capacitor and the anode of the detecting diode.

Claim 29

A power supply according to claim 23, wherein said clamp stage comprises a PNP transistor having a base coupled to the detecting diode, a collector coupled to ground, and an emitter coupled to the output of the error amplifier.

Claim 30

A power supply according to claim 24, further comprising two directly biased diodes connected in cascade between the output of the error amplifier and the emitter of the PNP transistor.

Claim 31

A power supply according to claim 21, wherein the detecting and generating circuit comprises means for generating the DC signal to have an amplitude inversely proportional to the frequency of the periodic signal.

Claim 32

A power supply according to claim 26, wherein the clamping stage comprises means for clamping the output of the error amplifier at a voltage having an amplitude proportional to the amplitude of the generated DC signal.

Claim 33

A power supply according to claim 21, wherein the oscillator comprises a sawtooth oscillator.

Claim 34

A power supply for a scanning circuit of a cathode ray tube operating at varying frequencies of synchronization and comprising: a static DC--DC converter comprising a current mode PWM controller, said current mode PWM controller comprising an oscillator including a resistor and a first capacitor defining a resistor-capacitor (R-C) circuit coupled between a node at a reference voltage and ground; an error amplifier of an output voltage referred to a pre-established voltage; and a current control circuit comprising a current sensing resistor to be functionally connected in series with a power switch and control means for controlling an output power by varying a switching frequency of the power switch, said control means comprising a detecting and generating circuit for detecting a periodic signal produced on the first capacitor of said R-C circuit and for generating a DC signal having an amplitude inversely related to a frequency of the periodic signal, and an offset circuit for offsetting a signal present on said current sensing resistor by a voltage corresponding to a difference between a constant voltage and the DC signal.

Claim 35

A power supply for a scanning circuit of a cathode ray tube operating at varying frequencies of synchronization and comprising: a static DC--DC converter comprising a current mode PWM controller, said current mode PWM controller comprising an oscillator including a resistor and a first capacitor defining a resistor-capacitor (R-C) circuit coupled between a node at a reference voltage and ground; an error amplifier of an output voltage referred to a pre-established voltage; and a current control circuit comprising a current sensing resistor to be functionally connected in series with a power switch and control means for controlling an output power by varying a switching frequency of the power switch, said control means comprising a detecting and generating circuit for detecting a periodic signal produced on the first capacitor of said R-C circuit and for generating a DC signal having an amplitude inversely related to a frequency of the periodic signal, and an offset circuit for offsetting a signal present on said current sensing resistor by a voltage corresponding to a difference between a constant voltage and the DC signal.

Claim 36

A power supply according to claim 29, wherein the detecting and generating circuit further comprises a second capacitor for determining a time constant; wherein the current mode PWM controller comprises a completely integrated portion except for the second capacitor; and wherein the second capacitor is externally connectable to the completely integrated portion through a dedicated connecting pin.

Claim 37

A power supply according to claim 29, further comprising a detecting diode having an anode; and wherein said detecting and generating circuit comprises a buffer amplifier functionally connected between the first capacitor and the anode of the detecting diode.

Claim 38

A power supply according to claim 29, wherein the detecting and generating circuit comprises means for generating the DC signal to have an amplitude inversely proportional to the frequency of the periodic signal.

Claim 39

A power supply according to claim 29, wherein the oscillator comprises a sawtooth oscillator.