POWER CONVERSION DEVICE, MOTOR DRIVE DEVICE PROVIDED THEREWITH, FAN PROVIDED WITH SAID MOTOR DRIVE DEVICE, COMPRESSOR, AND AIR CONDITIONER, REFRIGERATOR, AND FREEZER PROVIDED WITH SAID FAN AND COMPRESSOR

摘要

To obtain a power conversion device that makes it possible to: both lengthen phase-current detection periods and simplify detection procedures; and control a carrier frequency so as to improve device performance. A power-supply shunt resistance (5) is provided between the load-voltage side of a DC power supply (1) and an inverter (2), and a lower-arm shunt resistance (6a through 6c) for each phase is provided between a lower-arm switching element (3d through 3f) for that phase and the power-supply shunt resistance (5). For each phase, a lower-arm voltage is detected, said lower-arm voltage being the voltage between the load-voltage side of the DC power supply (1) and the point where the lower-arm switching element (3d through 3f) for that phase connects to the lower-arm shunt resistance (6a through 6c) for that phase. The amount of current flowing through a load device (9) in each phase is computed on the basis of the detected lower-arm voltages, and the carrier frequency of a carrier signal, which serves as a base frequency for drive signals, is controlled in accordance with changes in a specific control parameter (A).