| 摘要 |
PURPOSE:To protect a main switching element or a motor against circulation current by providing an OFF control means for temporarily turning OFF conducting main switching elements at same timing thereby blocking the circulation current from growing. CONSTITUTION:A mode detecting means 10 for detecting a regenerative mode is provided and when the means 10 detects a regenerative mode, a signal notifying the regenerative mode is delivered to an OFF control means 11. Consequently, a binary signal generating circuit 113 has an output lower than the maximum output of a saw-tooth wave generating circuit 112 and a comparator 114 outputs a pulse signal. Logic circuits 108, 110 then interrupt base signals of main switching elements Q1, Q2. Since the output from the OFF control means 11 functions commonly on a circuit producing the base signals for other main switching elements Q3-Q6, all main switching elements Q1-Q6 are temporarily turned OFF at same timing. |
