A Single LED is very small, and their luminance is related to the amount of driving current. Sufficient luminance for an illuminator requires many LEDs to be connected together and a constant current supplied to each LED. Therefore, the LED drive circuit must have constant-output-current control and/or constant-luminance control. We propose an LED drive circuit that consists of a boost-type DC-DC converter with constant-output-current control and constant-luminance control. This circuit is a switching regulator-type circuit controlled by pulse width modulation (PWM). Both the power and the constant-current control can be provided by a single system, without any ballast resistor or auxiliary current control circuit.
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