| 摘要 |
<P>PROBLEM TO BE SOLVED: To make a switching power supply circuit compatible over a wide range for power factor improvement, and to reduce the number of circuit component parts and the manufacturing cost of the circuit. <P>SOLUTION: For example, the number of turns of the primary winding N1 of an isolation converter transformer PIT is changed, according to the level of commercial alternating-current power supply AC. Thus, the range of control required for stabilizing operation, by switching frequency control is thereby nestled within the maximum control range of switching frequency in the 100 V AC system and in the 200 V AC system. Thus, stabilization can be carried out in correspondence both with the secondary direct-current output voltage Eo in the 100 V AC system and with that in the 200 V AC system for coping with a wider range. Power factor improvement is carried out by a power regeneration (feedback) method, and the magnetic flux density of the insulating converter transformer is controlled to a required value or smaller to expand the continuous mode of secondary-side rectifying operation. Thus, the ripple component superposed on secondary direct-current output voltage, which has posed problems in a power factor improvement by a power regeneration method, is suppressed. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
