| 摘要 |
PURPOSE:To protect a main transistor against the surge voltage for a switching circuit by providing a subtransistor between the collector and base terminals of a switching transistor to absorb the surge voltage. CONSTITUTION:A main transistor TR 1 is switched by a driving pulse to be switched on and off by e base current Ib1 and base adverse current Ib2 respectively and then turned off. Then the surge voltage is generated by the wiring inductance L when a main circuit current I is rapidly attenuated. Under such conditions, the current I obtained by adding a current I1 flowing to a diode 3 and a resistance 4 to a current I2 flowing to the TR 1 is attenuated by an extent close to the attenuation specific linear value of a subtransistor TR 2. Thus the reduction rate is reduced and therefore the energy of the surge voltage is also reduced. The current I is bypassed by the TR 2 and the reduced energy is consumed more. As a result, the surge voltage can be absorbed. |
