Switch mode power supply with improved transient performance and control circuit thereof
AssigneeChengdu Monolithic Power Systems Co., Ltd.
InventorShanglin Xu
Life of this patent
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Abstract
A control circuit used in a switch mode power supply is provided. The control circuit has an error amplifier, a first compensation network having a first resistance and a second compensation network having a second resistance. The error amplifier has a first input terminal, a second input terminal and an output terminal. The first compensation network is coupled between the first input terminal and the output terminal of the error amplifier. The second compensation network is coupled to the first input terminal of the error amplifier. When the switch mode power supply enters the transient state, the control circuit increases the first resistance of the first compensation network or decreases the second resistance of the second compensation network.
Claims17
A control circuit used in a switch mode power supply, wherein the switch mode power supply has a power switch and an inductor, and converts an input voltage into an output voltage, the control circuit comprising:
- a transient detector configured to detect whether the switch mode power supply is in a transient state, and generate a transient detecting signal based on the detection result;
- an error amplifier having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is configured to receive a first feedback voltage indicative of the output voltage and the second input terminal is configured to receive a first reference voltage, the error amplifier is configured to provide an error signal at the output terminal based on the first feedback voltage and the first reference voltage;
- a first compensation network having a first resistance, the first compensation network has a first terminal and a second terminal, wherein the first terminal is coupled to the first input terminal of the error amplifier and the second terminal is coupled to the output terminal of the error amplifier;
- a first resistance regulator configured to receive the transient detecting signal and regulate the first resistance based on the transient detecting signal;
- and
- an adjusting voltage generator, wherein when the output voltage decreases and the switch mode power supply enters the transient state, the adjusting voltage generator is configured to provide an adjusting voltage with positive polarity to the second input terminal of the error amplifier, and wherein when the output voltage increases and the switch mode power supply enters the transient state, the adjusting voltage generator is configured to provide an adjusting voltage with negative polarity to the second input terminal of the error amplifier.
A switch mode power supply configured to convert an input voltage into an output voltage, the switch mode power supply comprising:
- a power switch;
- an inductor;
- a transient detector configured to detect whether the switch mode power supply is in a transient state, and generate a transient detecting signal based on the detection result;
- an error amplifier having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is configured to receive a first feedback voltage indicative of the output voltage and the second input terminal is configured to receive a first reference voltage, the error amplifier is configured to provide an error signal at the output terminal based on the first feedback voltage and the first reference voltage;
- a first compensation network having a first resistance, the first compensation network has a first terminal and a second terminal, wherein the first terminal is coupled to the first input terminal of the error amplifier and the second terminal is coupled to the output terminal of the error amplifier;
- a first resistance regulator configured to receive the transient detecting signal and regulate the first resistance based on the transient detecting signal;
- and
- an adjusting voltage generator, wherein when the output voltage decreases and the switch mode power supply enters the transient state, the adjusting voltage generator is configured to provide an adjusting voltage with positive polarity to the second input terminal of the error amplifier, and wherein when the output voltage increases and the switch mode power supply enters the transient state, the adjusting voltage generator is configured to provide an adjusting voltage with negative polarity to the second input terminal of the error amplifier.
A control method used in a switch mode power supply, wherein the switch mode power supply has a power switch and converts an input voltage into an output voltage by controlling the power switch, the control method comprising:
- engaging a control loop having an error amplifier to control the power switch, wherein the error amplifier has a first input terminal, a second input terminal and an output terminal;
- coupling a first compensation network between the first input terminal and the output terminal of the error amplifier, or coupling a second compensation network to the first input terminal of the error amplifier;
- and
- detecting whether the switch mode power supply enters a transient state, if the switch mode power supply enters the transient state, increasing a first resistance of the first compensation network or decreasing a second resistance of the second compensation network;
- wherein
- when the output voltage decreases and the switch mode power supply enters the transient state, a positive voltage is provided to the second input terminal of the error amplifier;
- and wherein
- when the output voltage increases and the switch mode power supply enters the transient state, a negative voltage is provided to the second input terminal of the error amplifier.
Dependencies are inferred from the claim text.