Converter circuit and motor drive control apparatus, air-conditioner, refrigerator, and induction heating cooker provided with the circuit

摘要

A converter circuit comprises first (3a) and second (3b) step-up converters connected in parallel; the first step-up converter (3a) includes a rectifier (2), a step-up reactor (4a), a switching element (5a), and a reverse current prevention element (6a); the second step-up converter (3b) includes a step-up reactor (4b), a switching element (5b), and a reverse current prevention element (6b); switching control means (7) controlling switching elements (5a) and (5b); and a smoothing capacitor (8) that is provided at the output of the step-up converters (3a) and (3b). The switching control means (7) switches the current mode operation of the converters into a continuous mode and a critical mode based on an input current value compared with a threshold.