A converter device is provided which has a power factor improving circuit that
removes effects of noise superimposed on an AC power supply and reduces higher
harmonics and improves the power factor. A power factor improving circuit (103)
generally includes a voltage error amplifier (8), a current error amplifier
(10), a comparator (11), a triangular wave oscillator (12),
an output buffer (13), and a DC power supply (PS). A power factor improving
unit (102) has a photocoupler (14) for detecting an output of an
AC power supply (1) and a microcomputer (15), where the output (Vp)
of the photocoupler (14) is given to the MCU of the microcomputer (15).
A D/A converter (17) in the microcomputer (15) gives a converter
output (DAO) to the power factor improving circuit (103) and the power factor
improving circuit (103) gives a reference voltage (VREF) to the D/A converter (17).
