Converter circuit and associated method

A converter circuit for converting an input voltage to an output voltage, comprising:

• an error amplifier, coupled to the output voltage or a feedback output signal of the output voltage, and a reference signal, operable to generate an error signal accordingly;
• a ramp signal generator, generating a first ramp signal and a second ramp signal, wherein the absolute value of a declining slope of the first ramp signal is proportional to an amplitude of the error signal, and wherein a rising slope of the second ramp signal is proportional to the output voltage;
• a first comparator, coupled to the error signal and the first ramp signal, operable to generate a first comparing signal accordingly, wherein the first comparing signal is configured to turn on the converter circuit when the first ramp signal is lower than the error signal, and wherein an on time of the converter is reversely proportional to the rising slope of the second ramp signal;
• an adder having a first input terminal, a second input terminal and an output terminal, the first input terminal is configured to receive the error signal, the second input terminal is configured to receive an offset voltage, the adder is configured to add the error signal and the offset voltage to generate a sum signal, and wherein the offset voltage is provided by a DC voltage source, and wherein the DC voltage source has a negative terminal and a positive terminal, the negative terminal is connected to ground, the positive terminal is connected to the second input terminal of the adder to provide a constant DC voltage signal as the offset voltage;
• a second comparator, coupled to the sum signal and coupled to the second ramp signal, operable to generate a second comparing signal accordingly, wherein the second comparing signal is configured to turn off the converter circuit when the second ramp signal is higher than the sum signal, and wherein an off time of the converter is reversely proportional to the declining slope of the first ramp signal;
• and
• a control signal generator, coupled to the first comparing signal and the second comparing signal, operable to generate a control signal to turn switches in the converter circuit ON and OFF accordingly.