Switching power supply device, switching power supply control method and electronic apparatus
First Claim
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1. A switching power supply device in a critical mode, comprising:
- a load detection section that detects a load;
an additional circuit, wherein the additional circuit includes a state transition detector, control logic, and a variable frequency signal oscillator;
a pulse generator, including;
a comparator;
a flip flop; and
an AND gate, wherein the comparator of the pulse generator receives a ramp signal from a ramp waveform generator, and a load signal from the load detection section, wherein a reset pulse is provided to a reset input of the flip flop from the comparator when a voltage of the ramp signal intersects a voltage of the load signal, wherein the AND gate receives a frequency control signal from the variable frequency signal oscillator of the additional circuit, and an output signal from a zero detector, and wherein an output of the AND gate is provided to a set input of the flip flop;
wherein, when the state transition detector determines that a voltage of the detected load is lighter than a threshold voltage, the control logic switches a frequency of the control signal of the variable frequency signal oscillator, wherein an upper limit of a switching frequency output by the pulse generator is lowered stepwise, wherein the switching frequency output by the pulse generator is a different, fixed amount for each of at least three stages, and wherein the control logic switches the threshold voltage in a plurality of stages.
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Abstract
Provided is a switching power supply device in a critical mode, including a load detection section that detects a load. When the detected load is lighter than a setting value, an upper limit of a switching frequency is lowered stepwise.
11 Citations
15 Claims
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1. A switching power supply device in a critical mode, comprising:
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a load detection section that detects a load; an additional circuit, wherein the additional circuit includes a state transition detector, control logic, and a variable frequency signal oscillator; a pulse generator, including; a comparator; a flip flop; and an AND gate, wherein the comparator of the pulse generator receives a ramp signal from a ramp waveform generator, and a load signal from the load detection section, wherein a reset pulse is provided to a reset input of the flip flop from the comparator when a voltage of the ramp signal intersects a voltage of the load signal, wherein the AND gate receives a frequency control signal from the variable frequency signal oscillator of the additional circuit, and an output signal from a zero detector, and wherein an output of the AND gate is provided to a set input of the flip flop; wherein, when the state transition detector determines that a voltage of the detected load is lighter than a threshold voltage, the control logic switches a frequency of the control signal of the variable frequency signal oscillator, wherein an upper limit of a switching frequency output by the pulse generator is lowered stepwise, wherein the switching frequency output by the pulse generator is a different, fixed amount for each of at least three stages, and wherein the control logic switches the threshold voltage in a plurality of stages. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of controlling a switching power supply in a critical mode, comprising:
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lowering an upper limit of a switching frequency stepwise when a load is detected by a load detection circuit and the detected load is lighter than a setting value, wherein the switching frequency is controlled by a pulse generator in response to a ramp signal, a signal from the load detection section, and a signal from a variable frequency signal oscillator provided as part of an additional circuit, wherein the pulse generator includes; a comparator; a flip flop; and an AND gate, wherein the comparator of the pulse generator receives a ramp signal from a ramp waveform generator, and a load signal from the load detection section, wherein a reset pulse is provided to a reset input of the flip flop from the comparator when the ramp signal intersects the load signal, wherein the AND gate receives a frequency control signal from the variable frequency signal oscillator of the additional circuit, and an output signal from a zero detector, wherein an output of the AND gate is provided to a set input of the flip flop, wherein the additional circuit further includes a state transition detector and control logic, wherein, when the state transition detector determines that a voltage of the detected load is lighter than a threshold voltage, the control logic switches a frequency of the control signal of the variable frequency signal oscillator, wherein an upper limit of a switching frequency output by the pulse generator is lowered stepwise, wherein the switching frequency output by the pulse generator is a different, fixed amount for each of at least three stages, and wherein the control logic switches the threshold voltage in a plurality of stages.
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15. An electronic apparatus comprising a switching power supply device in a critical mode,
wherein the switching power supply device includes a load detection section that detects a load, and when the detected load is lighter than a setting value, an upper limit of a switching frequency is lowered stepwise by a pulse generator in response to a ramp signal, a signal from a load detection section, and a signal from a variable frequency signal oscillator provided as part of an additional circuit, wherein the pulse generator includes: -
a comparator; a flip flop; and an AND gate, wherein the comparator of the pulse generator receives a ramp signal from a ramp waveform generator, and a load signal from the load detection section, wherein a reset pulse is provided to a reset input of the flip flop from the comparator when the ramp signal intersects the load signal, wherein the AND gate receives a frequency control signal from the variable frequency signal oscillator of the additional circuit, and an output signal from a zero detector, wherein an output of the AND gate is provided to a set input of the flip flop, wherein the additional circuit further includes a state transition detector and control logic, wherein, when the state transition detector determines that a voltage of the detected load is lighter than a threshold voltage, the control logic switches a frequency of the control signal of the variable frequency signal oscillator, wherein an upper limit of a switching frequency output by the pulse generator is lowered stepwise, wherein the switching frequency output by the pulse generator is a different, fixed amount for each of at least three stages, and wherein the control logic switches the threshold voltage in a plurality of stages.
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Specification