Light emitting apparatus

Abstract

The invention provides an illuminating device. The objective of the invention is to inhibit overshoot current flowing over semiconductor light source and hold linear relationship between ON duty of determined light consumption and light consumption amount. In conduction of light emitting diodes LEDs 1 to 4, a switching signal 101 is converted into a voltage V 2 or 0V through a signal converter 26 in accordance with a logic level thereof The voltage obtained by the conversion is compared with a voltage V 1 on both ends of a resistor R 1 through an operational amplifier 20 to open / close an output loop by an NMOS transistor 22, a current If of the light emitting diodes LEDs 1 to 4 is limited to a current If 1 so as not to exceed a maximum current, and a current defined with an ON duty of the switching signal 101 is caused to flow as a mean current to the light emitting diodes LEDs 1 to 4 to inhibit an overshoot current from flowing to the light emitting diodes LEDs 1 to 4 while the output loop is closed.

Description

technical field [0001] The present invention relates to a light emitting device, and more particularly to a light emitting device configured to be usable as a vehicle lamp. Background technique [0002] Conventionally, semiconductor light emitting elements such as LEDs (Light Emitting Diodes) are known as light sources for vehicle lamps. When lighting LEDs and the like, for example, a structure is adopted in which a DC / DC converter is used as a power supply to boost the battery voltage while chopping, rectifies and smoothes the boosted voltage, and Provides smoothed DC power to LEDs. At this time, a shunt resistor is inserted into the output loop of the DC / DC converter in addition to the LED, and the current of the LED is detected from the voltage across the shunt resistor, and feedback control is performed in the DC / DC converter based on the detected current. , so that the current flowing in the LED is constant. When a plurality of LEDs are connected in series, each LED ...

AI Technical Summary

Problems solved by technology

However, in this method, for example, in order to slow down the conduction speed of the switching element, when the switching element is turned on and off at an on-duty of 10%, there is a concern that there will be a period in which sufficient current does not flow through the LED. % Dimming is on, the actual light amount is reduced to 5%, for example, and the linearity of the relationship between the conduction duty and the dimming light amount cannot be maintained.

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