| 摘要 |
<p>PURPOSE:To operate a DC-DC converter during an interval after occurrence of power interruption before provision of an undervoltage alarm by suppressing production of the undervoltage alarm upon detection of power interruption and suppressing production of a power interruption signal until detection of undervoltage thereby making possible to produce the undervoltage alarm upon recovery of power. CONSTITUTION:Upon elapse of a predetermined time after power interruption, a power interruption detecting circuit 21 detects power interruption to produce a high level output signal B which is fed through an inverter 23b to an AND circuit 23a. Consequently, production of an UVA signal for externally alarming power interruption is inhibited thus realizing a normal operation with respect to the outside. When the voltage drops furthermore due to sustained power interruption and the undervoltage detecting circuit 21 detects an undervoltage close to an alarm limit for producing a high level output signal A, an AND circuit 23c produces a power interruption signal to externally alarm power interruption.</p> |
