AC-DC converter having improved power factor to control feedback signal corresponding to output voltage of constant control circuit

An AC-DC converter of a type having an improved power factor including a rectifying circuit for rectifying an AC input supplied from a commercial power supply line, a booster converter circuit that raises the level of rectified voltage from aid rectifying circuit to obtain DC voltage higher than the peak value of the rectified output voltage at the both ends of an output capacitor thereof and a DC-DC converter circuit that converts the voltage obtained at said output capacitor of said booster converter circuit into a stabilized output to supply said stabilized output to an external load, said AC-DC converter comprising:

• an error amplifier that subjects a voltage corresponding to the output voltage between terminals of said output capacitor and voltage corresponding to reference voltage to a comparison to transmit a signal for maintaining the voltage between said terminals of said output capacitor at a constant level;
• and
• means including a constant-current circuit disposed between an input terminal of said error amplifier and a low-potential-side line of said booster converter circuit for changing the voltage corresponding to the output voltage of said output capacitor, wherein
• control of a constant-current value of said constant-current circuit is performed with said rectified output voltage from said rectifying circuit.