Switching converter with smart frequency generator and control method thereof
First Claim
1. A switching converter, comprising:
- a switching circuit having a main transistor, wherein the switching circuit is configured to convert an input voltage into an output voltage;
a feedback circuit coupled to the switching circuit, wherein the feedback circuit is configured to generate a feedback signal indicative of the output voltage;
a current sensing circuit configured to sense the current flowing through the main transistor and generate a current sensing signal;
a clock generator configured to generate a clock signal;
an error amplifying circuit coupled to the feedback circuit, wherein based on the difference between a first reference voltage and the feedback signal, the error amplifying circuit generates a compensation signal;
a comparing circuit coupled to the current sensing circuit and the error amplifying circuit, wherein the comparing circuit compares the current sensing signal with the compensation signal and generates a reset signal; and
a control circuit coupled to the clock generator and the comparing circuit, wherein based on the clock signal and the reset signal, the control circuit generates a control signal to control the main transistor;
whereinthe clock generator is coupled to the control circuit to receive the control signal and detect whether the on-time of the main transistor is smaller than a time threshold based on the control signal, and wherein if the on-time of the main transistor is smaller than the time threshold, the clock generator will adjust the frequency of the clock signal to regulate the on-time of the main transistor to be equal to the time threshold.
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Abstract
A control method of a switching converter, wherein the switching converter has a main transistor and is configured to provide an output signal. The control method includes: generating a feedback signal indicative of the output signal of the switching converter; generating a clock signal to determine the switching frequency of the main transistor; generating a control signal to control the main transistor based on the clock signal and the feedback signal; and detecting whether the on-time of the main transistor is smaller than a time threshold based on the control signal. If the on-time of the main transistor is smaller than the time threshold, the frequency of the clock signal will be adjusted to regulate the on-time of the main transistor to be equal to the time threshold.
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Citations
17 Claims
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1. A switching converter, comprising:
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a switching circuit having a main transistor, wherein the switching circuit is configured to convert an input voltage into an output voltage; a feedback circuit coupled to the switching circuit, wherein the feedback circuit is configured to generate a feedback signal indicative of the output voltage; a current sensing circuit configured to sense the current flowing through the main transistor and generate a current sensing signal; a clock generator configured to generate a clock signal; an error amplifying circuit coupled to the feedback circuit, wherein based on the difference between a first reference voltage and the feedback signal, the error amplifying circuit generates a compensation signal; a comparing circuit coupled to the current sensing circuit and the error amplifying circuit, wherein the comparing circuit compares the current sensing signal with the compensation signal and generates a reset signal; and a control circuit coupled to the clock generator and the comparing circuit, wherein based on the clock signal and the reset signal, the control circuit generates a control signal to control the main transistor;
whereinthe clock generator is coupled to the control circuit to receive the control signal and detect whether the on-time of the main transistor is smaller than a time threshold based on the control signal, and wherein if the on-time of the main transistor is smaller than the time threshold, the clock generator will adjust the frequency of the clock signal to regulate the on-time of the main transistor to be equal to the time threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A controller used in a switching converter, wherein the switching converter has a main transistor and is configured to provide an output signal, the controller comprises:
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a clock generator configured to generate a clock signal to determine the switching frequency of the main transistor; and a control circuit coupled to the clock generator, wherein based on the clock signal and a feedback signal indicative of the output signal of the switching converter, the control circuit generates a control signal to control the main transistor;
whereinif the on-time of the main transistor is smaller than a time threshold, the clock generator will adjust the frequency of the clock signal to regulate the on-time of the main transistor to be equal to the time threshold; and
whereinthe clock generator comprises; a first current control circuit having an input terminal and an output terminal, wherein the input terminal is coupled to the control circuit to receive the control signal, and wherein based on the control signal, the first current control circuit detects whether the on-time of the main transistor is smaller than the time threshold, and generates a first current control signal at the output terminal; a first controllable current source having a first terminal, a second terminal and a control terminal, wherein the first terminal is coupled to a power supply voltage, the control terminal is coupled to the output terminal of the first current control circuit; a frequency setting circuit configured to provide a setting current; a first current mirror including a first transistor and a second transistor, wherein the first current mirror has a power supply terminal, a first terminal and a second terminal, and wherein the power supply terminal is coupled to the power supply voltage, the first terminal is coupled to the frequency setting circuit and the second terminal of the first controllable current source; a first capacitor having a first terminal and a second terminal, wherein the first terminal is coupled to the second terminal of the first current mirror, the second terminal is coupled to a reference ground; a fourth transistor having a first terminal, a second terminal and a control terminal, wherein the first terminal is coupled to the first terminal of the first capacitor, the second terminal is coupled to the reference ground; a comparator having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is coupled to the first terminal of the first capacitor, the second input terminal is configured to receive a threshold voltage; and a first one-shot circuit having an input terminal and an output terminal, wherein the input terminal is coupled to the output terminal of the comparator, the output terminal is coupled to the control terminal of the fourth transistor and is configured to provide the clock signal. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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Specification