Parameterised LED current regulator for pulse width modulation switch delay for accurate colour mixing in multi-LED light sources

Abstract

Multi-LED colour mixing light sources are increasingly being used in lighting. The method used to set the dimming signal needs to accurately achieve and sustain the desired colour temperature and high colour rendering index (CRI). A pulse width modulation (PWM) signal is always used in LED colour mixing. But the PWM switch state creates a time delay in the multi-LED current regulator, resulting in a colour difference. A modified PWM signal to accurately maintain the desired colour temperature and a high CRI is derived from a parameterised LED current regulator switch state, using curve fitting. The modified PWM signal can be calculated from reconstructed coefficients of the illuminant spectrum.

Solar spectrum matching using monochromatic LEDs

“…Further, some researchers have put a huge number of different LEDs into an integrating sphere, and have changed the drive current of LEDs through pulse width modulation (PWM) technology to adjust the output light spectrum to match that of sunlight. [20][21][22][23][24] But thousands of LEDs increase the complexity and costs of the control circuit. Furthermore, changing the LED current will cause its main wavelength to drift and variation of the full width half maximum (FWHM) as well as the SPD.…”