| 摘要 |
PURPOSE:To make small the circuit component, by reducing the power consumption through the current limit at the application of abnormal voltage. CONSTITUTION:When an abnormal voltage is fed to output terminals 13, 14, the base potential of charging control transistors TR25, 26 is limited with current control Zener diodes 31, 32 and the collector potential of TR25, 26 is increased. The base potential of protection TRs 33, 34 is increased accordingly, and TRs 25, 26 are compulsively OFF when the relation of voltage drops VE1, VE2, VB1, VB2 of bias resistors 23, 24, 29, 30 is VB1>VE1 and VB2>VE2. Thus, the impedance of the entire circuit is greater and the power consumption of the charging circuit is smaller. Further, when the abnormal voltage is released, the relation is again VB1<VE1, VB2<VE2, and the operation restores to normal operation. |
