A display LED drive circuit is configured as follows. For example, a constant current circuit, a green display LED circuit, and a red display LED circuit are connected in series and a resistor circuit having a resistor causing a potential difference identical to each of the display LED is connected in parallel to each of the LED circuits. A corresponding switching element of the display LED circuit and a corresponding switching element of the resistor circuit connected in parallel are controlled to be opened and closed in opposite ways. Another route connected to a source circuit in parallel is connected to a constant current circuit, a blue display LED circuit, and a constant voltage diode in series. The blue display LED circuit is connected in parallel to a resistor circuit as has been described above. A predetermined voltage is taken out from the output terminal by the constant voltage diode and supplied to a control circuit. Thus, it is possible to reduce the number of constant current circuits, current consumption, and the cost, thereby improving the power source use efficiency.