| 摘要 |
PURPOSE:To secure the insulation between a main power supply system and the control system of an FET and to simplify the constitution of a driving circuit, by combining the FET and a driving transformer having the driving, control and insulating functions. CONSTITUTION:A driving transformer T1' contains a secondary winding III which is connected to a pulse duration control circuit via a transistor TRQ3. Then an FET is adversely biased when the TRQ3 is turned on in case when the FET is turned on with the deenergizing current. As a result, the deenergizing current which does not finish the extraction of the input capacity of the FET and the discharge of the energizing energy of the transformer T1' is discharged through a winding II. Thus the FET is turned off. In this connection, the on- time of the FET can be controlled by varying the on-time of the TRQ3. With use of such driving transformer, the insulation is secured between a main power supply system and an FET control system. At the same time, the constitution can be simplified for a driving circuit. |
