| 摘要 |
PURPOSE:To protect transistor (TR) securely by providing a TR in use with a temperature detector and comparing the output of an arithmetic circuit which vary a safe operation area according to temperature variation with a loss which is generated actually. CONSTITUTION:A cooling body which radiates heat from TRs 3A, 3B, and 3C is fitted to a temperature detector 16 composed of a thermistor, etc., and its detected temperature is converted by a temperature detecting amplifier 17 into a numeral corresponding to the temperature dependency of the permissible loss of the TRs 3A-3C. The output signal of this temperature detecting amplifier 17 and a set signal from a permissible loss setter 19 are added together by an adder 18 to calculate permissible loss corresponding to the operation condition of the TRs, so the permissible loss obtained by the adder 18 is compared by a comparator 18 with generated loss obtained from a multiplier 15; when the generated loss exceeds the permissible loss, the comparator 20 outputs a signal to a logical circuit 21 for protection to take proper measures by stopping the operation of the Trs 3A-3C, etc. |
