Switch mode power supply, control circuit and associated control method
AssigneeChengdu Monolithic Power Systems Co., Ltd.
InventorsJunming Zhang, Hao Long, Hui Li
Life of this patent
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Abstract
A switch mode power supply having an output terminal configured to provide an output voltage, the switch mode power supply has a first switch and a control circuit. The control circuit is configured to provide a switching control signal to control the first switch. The control circuit is configured to provide the switching control signal based on a first pulse signal having a first frequency and a second frequency for a light load condition, and the control circuit is configured to provide the switching control signal based on a second pulse signal for a non-light load condition.
Claims20
A control circuit for controlling a switch mode power supply, the switch mode power supply having an output terminal configured to provide an output voltage and having a first switch with a control terminal, wherein the control circuit comprising:
- a mode management unit, having an input terminal and an output terminal, wherein the output terminal of the mode management unit is configured to provide a mode control signal;
- a skip cycle mode control unit, having an input terminal and an output terminal, wherein the input terminal of the skip cycle mode control unit is configured to receive a feedback signal representing the output voltage, wherein the output terminal of the skip cycle mode control unit is configured to provide a first pulse signal having a first frequency and a second frequency, wherein the first frequency and the second frequency are predetermined;
- a normal mode control unit, having an output terminal configured to provide a second pulse signal;
- and
- a drive signal management unit, having a first input terminal, a second input terminal, a third input terminal and an output terminal, wherein the first input terminal of the drive signal management unit is coupled to the output terminal of the mode management unit, the second input terminal of the drive signal management unit is coupled to the output terminal of the skip cycle mode control unit, the third input terminal of the drive signal management unit is coupled to the output terminal of the normal mode control unit, and the output terminal of the drive signal management unit is configured to provide a switching control signal to the control terminal of the first switch based on the first pulse signal, the second pulse signal and the mode control signal.
A switch mode power supply, having an output terminal configured to provide an output voltage, wherein the switch mode power supply comprising:
- a first switch, having a control terminal;
- a feedback circuit, configured to provide a feedback signal based on the output voltage;
- and
- a control circuit, configured to receive the feedback signal and provide a switching control signal to the control terminal of the first switch;
- and wherein
- when the switch mode power supply works in a skip cycle mode for a light load condition, the control circuit is configured to provide the switching control signal based on a first pulse signal having a first frequency and a second frequency, wherein the first frequency and the second frequency are predetermined;
- and
- when the switch mode power supply works in a normal mode for a non-light load condition, the control circuit is configured to provide the switching control signal based on a second pulse signal.
A control method for a switch mode power supply, the switch mode power supply having a first switch and an output terminal configured to provide an output voltage, the control method comprising:
- providing a feedback signal based on the output voltage of the switch mode power supply;
- comparing a switching frequency of the first switch with a frequency threshold;
- when the switching frequency of the first switch is less than the frequency threshold, the switch mode power supply works in a skip cycle mode, the first switch is controlled based on a first pulse signal, wherein the first pulse signal has a first frequency and a second frequency, and wherein the second frequency is higher than the first frequency;
- and
- when the switching frequency of the first switch is larger than the frequency threshold, the switch mode power supply works in a normal mode, the first switch is controlled based on a second pulse signal, wherein the second pulse signal has a third frequency, and wherein the third frequency is higher than the second frequency.
Dependencies are inferred from the claim text.