Initial charge completion determination method, initial charge completion determination circuit and power conversion device in power conversion device

摘要

PROBLEM TO BE SOLVED: To make it possible to detect initial charging termination always at an optimum point of time while fixing a threshold for determining initial charging termination, when a variation in DC power supply voltage is great.SOLUTION: An initial charging termination determination method for a power conversion device that comprises a DC middle capacitor C between a DC power supply VB and a power conversion unit composed of a switching element and includes an input switch SW1 and charging resistor R1 for connecting the DC middle capacitor with the DC power supply for initial charging for the DC power supply detects a voltage of the DC power supply as a first voltage detection value V1; detects a voltage of the DC middle capacitor as a second voltage detection value V2; compares the first voltage detection value with the second voltage detection value; outputs an initial charging termination signal when the difference between the voltage detection values has been equal to or lower than a preset threshold; and multiplies, before the comparison, the first voltage detection value or the second voltage detection value by a factor predetermined on the basis of a division ratio between charging side impedance and discharging side impedance or the inverse of the factor.SELECTED DRAWING: Figure 1