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A constant ON-time or constant OFF-time switching power converter includes a control circuit for controlling a power switch. The control circuit includes: a constant ON-time or constant OFF-time calculation circuit, for calculating a constant ON-time or constant OFF-time; a logic circuit having inpu

A constant ON-time or constant OFF-time switching power converter includes a control circuit for controlling a power switch. The control circuit includes: a constant ON-time or constant OFF-time calculation circuit, for calculating a constant ON-time or constant OFF-time; a logic circuit having inputs for receiving an output of the constant ON-time or constant OFF-time calculation circuit and a clock signal, respectively, wherein the clock signal has a frequency which is the desired fixed frequency; and a flip-flop for generating an output signal according to a set input and a reset input, wherein one of the set input and the reset input receives an output of the logic circuit, and the other one of the set input and the reset input receives a trigger signal which determines a start time of the ON-time or OFF-time.

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1. A constant ON-time or constant OFF-time switching power converter, comprising: a power stage circuit including at least one power switch, for converting an input voltage to an output voltage by an operation of the power switch;a control circuit for generating a control signal to control the power

1. A constant ON-time or constant OFF-time switching power converter, comprising: a power stage circuit including at least one power switch, for converting an input voltage to an output voltage by an operation of the power switch;a control circuit for generating a control signal to control the power switch, the control circuit including: a constant ON-time or constant OFF-time calculation circuit, for calculating a constant ON-time or constant OFF-time according to input voltage related information and output voltage related information, whereby when the power switch operates according to the constant ON-time or the constant OFF-time, the power switch operates by a fixed switching frequency;a logic circuit having inputs for receiving an output of the constant ON-time or constant OFF-time calculation circuit and a clock signal, respectively, wherein the clock signal has a frequency which is the fixed switching frequency; anda flip-flop for generating an output signal according to a set input and a reset input, the output signal determining an ON-time or an OFF-time of the power switch, wherein one of the set input and the reset input is coupled to an output of the logic circuit, and the other one of the set input and the reset input is coupled to a trigger signal which determines a start time of the ON-time or OFF-time of the power switch. 2. The constant ON-time or constant OFF-time switching power converter of claim 1, wherein before the switching frequency of the power switch is aligned to the fixed switching frequency, the frequency of the clock signal is faster than the switching frequency of the power switch. 3. The constant ON-time or constant OFF-time switching power converter of claim 1, wherein after the power switch operates by fixed switching frequency, the power switch operates by a duty ratio which is higher than 50%. 4. The constant ON-time or constant OFF-time switching power converter of claim 1, wherein the control circuit further includes a comparator for comparing a feedback signal related to the output voltage with a reference signal to generate the trigger signal. 5. The constant ON-time or constant OFF-time switching power converter of claim 1, wherein the control circuit further includes: an error amplifier for comparing a feedback signal related to the output voltage with a reference signal to generate an error amplified signal; anda comparator for making a comparison according to the error amplified signal with a current sense signal related to an inductor current in the power stage circuit to generate the trigger signal. 6. The constant ON-time or constant OFF-time switching power converter of claim 5, wherein the error amplified signal is compensated to generate a slop-compensated error amplified signal, and the comparator compares the slop-compensated error amplified signal with the current sense signal to generate the trigger signal. 7. The constant ON-time or constant OFF-time switching power converter of claim 5, wherein the current sense signal is compensated to generate a slop-compensated current sense signal, and the comparator compares the slop-compensated current sense signal with the error amplified signal to generate the trigger signal. 8. A control circuit for controlling a constant ON-time or constant OFF-time switching power converter, the switching power converter including a power stage circuit which includes at least one power switch, for converting an input voltage to an output voltage by an operation of the power switch, the control circuit generating a control signal to control the power switch, the control circuit comprising: a constant ON-time or constant OFF-time calculation circuit, for calculating a constant ON-time or constant OFF-time according to input voltage related information and output voltage related information, whereby when the power switch operates according to the constant ON-time or the constant OFF-time, the power switch operates by a fixed switching frequency; a logic circuit having inputs for receiving an output of the constant ON-time or constant OFF-time calculation circuit and a clock signal, respectively, wherein the clock signal has a frequency which is the fixed switching frequency; anda flip-flop for generating an output signal according to a set input and a reset input, the output signal determining an ON-time or an OFF-time of the power switch, wherein one of the set input and the reset input is coupled to an output of the logic circuit, and the other one of the set input and the reset input is coupled to a trigger signal which determines a start time of the ON-time or OFF-time of the power switch. 9. The control circuit of claim 8, wherein before the switching frequency of the power switch is aligned to the fixed switching frequency, the frequency of the clock signal is faster than the switching frequency of the power switch. 10. The control circuit of claim 8, wherein after the power switch operates by fixed switching frequency, the power switch operates by a duty ratio which is higher than 50%. 11. The control circuit of claim 8, wherein the control circuit further includes a comparator for comparing a feedback signal related to the output voltage with a reference signal to generate the trigger signal. 12. The control circuit of claim 8, wherein the control circuit further includes: an error amplifier for comparing a feedback signal related to the output voltage with a reference signal to generate an error amplified signal; anda comparator for making a comparison according to the error amplified signal with a current sense signal related to an inductor current in the power stage circuit to generate the trigger signal. 13. The control circuit of claim 12, wherein the error amplified signal is compensated to generate a slop-compensated error amplified signal, and the comparator compares the slop-compensated error amplified signal with the current sense signal to generate the trigger signal. 14. The control circuit of claim 8, wherein the current sense signal is compensated to generate a slop-compensated current sense signal, and the comparator compares the slop-compensated current sense signal with the error amplified signal to generate the trigger signal.