Patent ID: 6980445

Claim:
A power factor improving converter comprising: an inductor (L 11 , L 21 , L 31 ) to which a ripple voltage is applied; a switching element (Q 11 , Q 21 , Q 31 ) connected to one end of said inductor (L 11 , L 21 , L 31 ) to switch current flowing into said inductor (L 11 , L 21 , L 31 ) according to the ripple voltage; a DC voltage generating section (D 16 , C 11 , D 21 , C 21 , D 31 , C 31 ) that rectifies voltage generated across said inductor (L 11 , L 21 , L 31 ) by switching said switching element (Q 11 , Q 21 , Q 31 ) and smoothes to generate a DC voltage; and a control section ( 106 , 205 , 305 ) that sets a target level of a switching current flowing into a current path of said switching element based on a voltage level of the ripple voltage and controls to turn on and off said switching element (Q 11 , Q 21 , Q 31 ) in such a way that the switching current reaches the target level, wherein said control section ( 106 , 205 , 305 ) obtains a parameter, which changes when a ratio between an effective value of the ripple voltage and a voltage value of the DC voltage generated by said DC voltage generating section (D 16 , C 11 , D 21 , C 21 , D 31 , C 31 ) changes, and controls the target level of the switching current according to a value of the obtained parameter.