| 摘要 |
PURPOSE:To decrease a turn-off time and to apply high speed switching to a power transistor (TR) by providing a comparison circuit comparing a voltage of a controlled system with a reference value and a circuit applying reversely a bias voltage to a base of the most pre-stage TR even during the on-period when the control object voltage is lower than the reference value at the output of the comparator circuit. CONSTITUTION:The power TR 1 is saturated at a value of a reference voltage source 10 or below immediately by an excess forward bias base current flowing to the power TR 1 at a period t1, an output of a compartor 9 is inverted and a reverse bias voltage is impressed to the base of the power TR 1. Thus, a large forward bias current flowing to the base of the power TR 1 is decreased rapidly and transits to a reverse bias current in a short time, then the time product (electric charge) of the excess forward bias current flowing after the power TR 1 is saturated is less and the degree of saturation of the per TR 1 is shallow. Moreover, the reverse bias current flows to release the saturation of the power TR 1 in a short time and the TR 1 is transited to the normal active state. |
