| 摘要 |
PROBLEM TO BE SOLVED: To provide a power unit which relieves the stress to a switching element caused by the charge current to a smoothing capacitor immediately after power on, without adding high breakdown strength and high-capacity parts, thereby suppressing increase in cost. SOLUTION: A power converter 2 is equipped with a series circuit composed of switching elements Q1 and Q2 turned on and off alternately. At on time of one switching element Q2, a charge current flows to a smoothing capacitor C1 via an inductor L1. Moreover, when the switching element Q2 is turned off, the energy of the inductor L1 is released, and a regenerative current flows into the switching element Q1. A control circuit 5 prevents the simultaneous turning on of the switching elements Q1 and Q2 by detecting the period when the regenerative current flows, based on the voltage polarity arising in the detected winding ns of a transformer T1, and keeping the switching element Q2 off during the period when the regenerative current flows. |
