| 摘要 |
PURPOSE:To prevent a transistor from being destroyed by a simple circuit by holding the ON time of a control input to the base of the transistor above a minimum value by connecting an ON-time holding circuit to the base circuit of the transistor put into operation by the control input from a control circuit. CONSTITUTION:Through transistor (TR) 10, power from DC power source 12 is applied to load 14 for ON-OFF operation and diode 16 absorbs the counter electromotive force of load 14 when (TR) 10 is in ON operation. Between the collector and emitter of this (TR) 10, capacitor 18, diode 20 and resistance 22 are connected to constitute a snubber circuit. To the base of (TR) 10 of this circuit, amplifier 24 is connected and between this amplifier 24 and control circuit 26, ON-time holding unit 28 is provided; and the output pulse width of monostable circuit 30 of this unit 28 is set to a value nearly equal to the discharge time of the snubber circuit and the output of OR circuit 32 is fixed above a minimum value without reference to the ON time of control circuit 26, thereby preventing the destruction of (TR) 10. |
