| 摘要 |
PURPOSE:To obtain a base driving circuit with high performance without causing power loss by providing an ON-voltage detector, a setting device of an ON- voltage command and a comparator controlling the switching operation as the result of comparison between the signals from the ON-voltage detector and the setting device. CONSTITUTION:The ON-voltage detector 24 detecting an ON-voltage VCE of a power transistor (TR) 1 with a low loss consists of a resistor 21 having a high resistance value not causing large power loss and a Zener diode 22 for clamping not to give an excessive voltage input to a comparator 13. Further, in order to detect quickly and accurately the ON-voltage VCE, a small diode 23 having several pF of junction capacitance is provided in series with the Zener diode 22. The switch 5 is turned on and off by setting the ON-voltage VCE detected by the voltage detector 24 as, for example, VCE'L for the operating voltage while the VCE falls down and VCE'H for the operating voltage when the VCE is rising in this way, according to the relation of the setting device 20 of a command voltage VCE' and the comparator 13 with hysteresis width. |
