Integrated circuit and method of digitally controling critical mode power factor correction circuit

An integrated circuit for digitally controlling a critical mode power factor correction circuit, the integrated circuit comprising:

• an output voltage detector and a switching current detector of the critical mode power factor correction circuit;
• an A/D converter and a sample and hold circuit that perform analog-to-digital conversion of an output signal of the output voltage detector and the switching current detector, wherein a sampling frequency of the A/D converter and the sample and hold circuit is synchronized with a variable switching frequency of the critical mode power factor correction circuit;
• an arithmetic unit that performs calculation based on the output signal of the A/D converter and generates a pulse signal to turn on and off a switching device of the critical mode power factor correction circuit;
• a correction value calculator that calculates, based on the sampling frequency, a linear correction value for correcting the output signal of the A/D converter;
• and
• an adder that adds the linear correction value calculated by the correction value calculator to the output signal of the A/D converter to correct the output signal of the A/D converter and inputs the corrected output signal to the arithmetic unit, wherein
• calculating the linear correction value by the correction value calculator comprises calculating the linear correction value based on a formula Vc=a−b/f for linear correction, where “a” and “b” are correction constants, “f” is the sampling frequency, and “Vc” is the linear correction value, and
• an area of the sampling frequency is divided into at least two sampling frequency bands, and the correction constants are set for each of the at least two sampling frequency bands.