| 摘要 |
PURPOSE:To obtain the stable output voltage although no coincidence is obtained for the input time point between the positive and negative DC voltages, by monitoring the DC input voltage with the reference voltage which is higher than each of the positive and negative voltages and lower than the total value of these voltages. CONSTITUTION:The positive DC voltage V1 is supplied between input terminals 1 and 2; and the negative DC voltage V2 is supplied between input terminals 2 and 3. The DC voltage V5 is delivered between output terminals 4 and 5. When only the voltage V2 is applied at a time point T1, the DC input voltage V4 is set lower than the breakdown voltage of a constant voltage diode ZD. As a result, no current flows to the diode ZD plus resistances R1 and R2, and accordingly a transistor TRQ3 is interrupted to supply no voltage to a constant voltage control circuit 6. Thereafter, the voltage V1 is applied and accordingly the voltage V4 exceeds the breakdown voltage of the diode ZD. Thus the circuit 6 has the normal operation to obtain the stable DC output voltage V3 between the terminals 4 and 5. |
