PURPOSE: To enable use of low voltage dry battery and detect drop of battery voltage at high precision, by multiple rectifying the battery voltage to obtain power source voltage, and obtaining stable reference voltage by dividing this power source voltage.
CONSTITUTION: The voltage of a low voltage battery 1 such as a dry battery is multiplied by about 3 times by an oscillation circuit 2, a multiplier circuit 3, a ripple absorbing circuit 9, etc. to be a multiplied voltage oscillation output, which drives a smoke monitor circuit 4 intermittently. On the other hand, the multiplied voltage oscillation output is divided and stabilized by a reference voltage generating circuit 6 which is composed of resistance R3, zenor diode Z and other parts to become an excellent reference voltage, which is applied to a comparator 5. To this comparator 5 is applied also a multiplied voltage oscillation output after being divided by resistances R1, R2 in a dividing circuit 8. Comparing these two inputs, the comparator 5 detects a voltage drop of the battery 1. Therefore, the smoke detector may be driven by a low voltage battery such as a dry battery, and the voltage drop of such low voltage battery may be detected precisely.
KAHARA TOORU
NAKANO TAKESHI
SUZUKI YOSHIHARU
