| 摘要 |
PROBLEM TO BE SOLVED: To provide a power factor improving power unit which can utilize AC power and DC power in common as input with one power unit, and also can reduce the power loss of an element for detecting the current for control of power factor improvement. SOLUTION: This power factor improving power unit is equipped with a function of bringing the waveform of an input current close to that of input voltage. The unit is provided with a rectifying circuit 11 which rectifies the input power of AC, a voltage identifying circuit Q3 which identifies the level of the voltage appearing in the output of the rectifying circuit 11 as either of at least two kinds, a current detection means R1 which is inserted into the current path between the output of the rectifying circuit 11 and the load, and a field effect transistor Q2 for shunting which is connected in parallel with the current detection means R1. The field effect transistor Q2 for shunting is turned on and off, according to the magnitude of the voltage identified with the voltage identifying circuit Q3. |
