| 摘要 |
In an LED unit, all of eight LEDs are connected in series. The voltage of a power supply, that is, a battery of a vehicle, 12 V, is insufficient for the eight LEDs. To cope with this, a boosting circuit is provided within the control unit to boost the voltage to about 16 V which is then applied to the eight LEDs. The front end of the LED unit is connected to a constant-current circuit, and a voltage detection circuit is provided near and connected to this constant-current circuit for detecting the voltage applied to the constant-current circuit. The voltage detected by the voltage detection circuit is compared with a reference voltage drawn from the power supply, is amplified in an amplifier, and is input as a boosting control signal into the boosting circuit. The boosting control signal is output so as to regulate the boosted voltage in such a manner that the voltage detected in the voltage detection circuit is a lowest possible voltage.
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