To secure the reliability of a lighting switch and suppress the generation of heat to eliminate influence on other components, by causing futile current to flow to destroy an oxide film in a contact of a switch, in an LED (hight-emitting diode) circuit.
In the LED circuit 1, when the lighting switch S1 is closed, a current is caused to flow in twelve LEDs (DL1) and then an LED lamp lights up. At the same time, a current is caused to flow in a capacitor C1 to charge it, and then current is caused to flow even into the base of a transistor Q2 to turn the transistor Q2 on, thereby causes current to flow in a resistor R5 and the transistor Q2. Furthermore, a transistor Q1 is also turned on, thereby causes current to flow in a resistor R6 and the transistor Q1. Since the sum of these currents and the current in the LEDs (DL1) fully exceeds 1A, the oxide film formed in the contact of the lighting switch S1 is destroyed and removed. After one to two seconds, the capacitor C1 is charged fully and the flow of the charging current is stopped; and consequently the flows of currents in the transistors Q1 and Q2 are also stopped, and there is no concern about the generation of heat.
TAKAHASHI TOSHINORI
MISAWA AKIHIRO
