| 摘要 |
PURPOSE:To cut off current of light emitting device with a switch, to save power, and to reduce power source capacity by providing a switch between a power source circuit and a driving circuit of light emitting element, by detecting current flow rate of a current flowing through a Peltier element with a detecting circuit, and by controlling the switch by detecting circuit output. CONSTITUTION:At start-up by an external power source with a switch 1 of a controlling-and-driving circuit for an light emitting element on, a switch 7 connected to a power source circuit 6 is opened to supply the current from the circuit 6 only to a temperature controlling circuit 2. When the temperature of a light emitting element LD 4 reaches near a specified temperature due to heating or cooling of a Peltier element 4 near the LD 4 connected to the circuit 2, and a current flow rate is reduced to decrease a voltage difference of a current detecting resistance R, the outputs of an absolute value amplifier 8 and an amplifier 9 become near zero. If the output of the amplifier 9 becomes less than a reference voltage E0, the output of a comparator 11 is inverted. Consequently, the switch 7 is closed by a switch driving circuit 10 and a current is supplied to an LD driving circuit 5, thus allowing the LD 4 to be driven. |
