| 摘要 |
PURPOSE:To protect an upstage FET from thermal breakdown by providing means for lagging the rising of power voltage for one component, i.e., a comparator, in a distribution circuit for a predetermined time and turning the upstage FETs, connected in H bridge, OFF for a predetermined time at the time of starting a motor. CONSTITUTION:Rising of power supply voltage for one components, i.e., comparators U1, U2, U3, in a distribution circuit 3 is lagged by means of a CR or the like thus turning upstage FETs Q1-Q3, connected in H bridge, OFF for a predetermined time at the time of starting a motor. Since the upstage FETs Q1-Q3 are turned ON only when an ON/OFF control power supply voltage for the upstage FETs Q1-Q3 reaches a level for turning the FETs Q1-Q3 perfectly ON, even if a control power supply voltage VC is fed under a state where a motor drive power supply voltage VM is being fed, the FETs Q1--Q3 can be protected against thermal breakdown thus obviating the necessity of determining the order of power supply input and realizing employment of so-called 2a contact type power supply input switch. |
