| 摘要 |
PURPOSE:To reduce the degree of risk of deterioration or damage by providing a short-circuit transistor (TR) capable of short-circuiting the base and emitter of an output TR by a low impedance and injecting a base current to the short- circuit TR from a current injection circuit when 2nd power supply voltage is below a prescribed limit. CONSTITUTION:A kind of a discharge resistor 32 to quicken the OFF operating speed is connected between the base and the emitter of the short-circuit TR 30. When the 2nd power supply voltage is below the limit and a voltage detecting TR 43 is turned off, an injecting TR 41 of an injecting current generating section enters the primary breakdown state where the base-emitter is released or opened and injects its primary breakdown current to the base of the short-circuit TR 30. The primary breakdown current as the injecting current is limited to a permissible value by a series resistance 42 of the collector-emitter circuit of the injection TR 41. Thus, the possibility of damage or deterioration of the injection TR 41 at its primary breakdown state is precluded. |
