CONTROL METHOD FOR STEP-UP/STEP-DOWN CHOPPER

摘要

PROBLEM TO BE SOLVED: To prevent the output voltage of a step-up/step-down chopper from being lowered below an allowable lower limit value, when the operation of the step-up/step-down chopper is switched from a step-down mode to a step-up mode, without increasing the capacitance of a smoothing capacitor and the rush current applied to the smoothing capacitor also. ;SOLUTION: If a DC voltage outputted by a step-up/step-down chopper 20 is stepped up not from zero but from a voltage higher than the allowable lower limit voltage of a 1st load 14, when a DC power supply 11 is interrupted and the operation of the step-up/step-down chopper 20 is switched from a step-down mode to a step-up mode, the output voltage of the step-up/step-down chopper 20 is not lowered to a voltage below the allowable lower limit voltage. Or a voltage command value which is given to an automatic voltage regulator 23 is started from a value higher, than the allowable lower limit value of the 1st load 14 to reach a required value at a predetermined voltage step-up speed. At that time, the proper step-up speed of the voltage command value is selected to protect a smoothing capacitor from excessive rush current.;COPYRIGHT: (C)1998,JPO