Constant-frequency control method with fast transient
AssigneeMonolithic Power Systems, Inc.
InventorZheng Luo
Life of this patent
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Abstract
A control circuit and method for a voltage converter. The control circuit having a ramp circuit, a reference generating circuit, a comparison circuit and a logic circuit. The ramp circuit generates a ramp signal that decreases from the moment the power switch is turned off and increases from the moment the power switch is turned on. The reference generating circuit generates a reference voltage. The comparison circuit compares the reference voltage with the sum of the feedback voltage and the ramp signal to generate a comparison signal. The logic circuit uses the comparison signal and a clock signal to generate the control signal to control a power switch of the voltage converter.
Claims13
A control circuit for a voltage converter converting an input voltage into an output voltage, wherein the voltage converter has a power switch, the control circuit comprising:
- a ramp circuit, configured to generate a ramp signal, wherein the ramp signal decreases from a moment the power switch is turned off and increases from a moment the power switch is turned on;
- a reference generating circuit, configured to generate a reference voltage, wherein the reference voltage increases from a value of a base voltage when the power switch is turned off, wherein the base voltage is regulated based on a feedback voltage and a source voltage, and the source voltage has a constant voltage level;
- a comparison circuit, configured to provide a comparison signal in response to the reference voltage and a sum of the feedback voltage and the ramp signal;
- and
- a logic circuit, configured to generate a control signal to control the power switch based on the comparison signal and a clock signal with constant frequency, wherein the power switch is turned off by the clock signal, and is turned on when the comparison signal indicates that the reference voltage increases to the sum of the feedback voltage and the ramp signal.
A voltage converting system for converting an input voltage into an output voltage, comprising:
- a voltage converter, comprising a power switch having a first terminal coupled to the input voltage, a second terminal and a controlled terminal;
- and
- a control circuit, comprising:
- a ramp circuit, configured to generate a ramp signal, wherein the ramp signal decreases from a moment the power switch is turned off and increases from a moment the power switch is turned on;
- a reference generating circuit, configured to generate a reference voltage, wherein the reference voltage increases from a value of a base voltage from a moment the power switch is turned off, wherein the base voltage is regulated based on a feedback voltage and a source voltage, and the source voltage has a constant voltage level;
- a comparison circuit, configured to provide a comparison signal in response to the reference voltage and a sum of the feedback voltage and the ramp signal;
- and
- a logic circuit, configured to generate the control signal based on the comparison signal and a clock signal with constant frequency, wherein the power switch is turned off by the clock signal, and is turned on when the comparison signal indicates that the reference voltage increases to the sum of the feedback voltage and the ramp signal.
A method of controlling a voltage converter to convert an input voltage into an output voltage, wherein the voltage converter comprises at least a power switch, the method comprising:
- turning off the power switch by a clock signal with constant frequency;
- generating a ramp signal and a reference voltage, wherein the ramp signal decreases from a moment the power switch is turned off and increases from a moment the power switch is turned on, and the reference voltage increases from a value of a base voltage from a moment the power switch is turned off, wherein the base voltage is regulated based on a feedback voltage and a source voltage, and the source voltage has a constant voltage level;
- comparing the reference voltage with a sum of the feedback voltage and the ramp signal, wherein the feedback voltage is in proportion to the output voltage;
- and
- turning on the power switch when the reference voltage reaches the sum of the feedback voltage and the ramp signal.
Dependencies are inferred from the claim text.