| 摘要 |
PURPOSE:To not only improve a utilization factor, but also protect transistors (TR) by detecting the collector-emitter voltage and collector current of a TR connected in series with a load and deciding whether a TR in operation is in its safe operaing region or not on the basis of the detected voltage and current. CONSTITUTION:A voltage detector 11 is connected between the collector and emitter of a TR3 which controls a voltage or current supplied to the load to detect the collector-emitter voltage VCE of the TR3 in operation. A current detector 10 and a current detecting amplifier 12 detect the collector current IC of the same TR3. A permissible current computing element 17 is a function generator and the collector current limit value IC* as its output signal varies with the collector-emitter current VCE as the TR3 operates. Therefore, a comparator 15 compares the actual value IC of the collector current outputted from the amplifier 12 with the collector current limit value IC* at any time. |
