| 摘要 |
PURPOSE:To prevent a power source output transistor from damaging by providing an input voltage detector and an operating point automatic converter. CONSTITUTION:A power source circuit is composed of a protector 4, a power source output transistor (Tr) 5, a controller 6 and rectifiers 7, 9 and a switching transformer 8. In this case, the protector 4 is composed of a protecting circuit 1 with an operating point automatic converter, an input voltage detector 2 and an overcurrent detecting resistor 3. Thus, an overcurrent and an input voltage are detected, the both detection signals are applied to the protecting circuit 1, the operating point of the circuit 1 is differentiated between when the input voltage becomes large and when becomes small, thereby preventing Tr 5 from damaging due to an overcurrent. |
