| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an inexpensive power factor improved circuit, having a simple constitution with the reduced number of components and wires. <P>SOLUTION: The power factor improving circuit has a current detecting resistor Rsh for detecting a current flowing to an AC power supply Vac or a current flowing to a full-wave rectifying circuit B; an output voltage detecting operational amplifier 11 for amplifying errors between the output voltage Eo and a first reference voltage Vref and generating an error voltage; a current-detecting operational amplifier 13 for amplifying and outputting an error between a voltage, in proportion to the current detected by the current-detecting resistor Rsh and a second reference voltage; a multiplier 12 for varying the output from the current detecting operational amplifier 13, in response to the value of the error voltage from the output voltage detecting operational amplifier 11, and outputting the varied voltage as the second reference voltage to the current-detecting operational amplifier 13; and a pulse width modulator 14 for generating pulse signals with a controlled pulse width, in response to an output value from the current detecting operational amplifier 13, applying the pulse signal to a main switch Q1, and controlling the output voltage to a predetermined voltage. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
