A double closed-loop control system for driving high brightness LED applied in spectral measurements

A double closed-loop control system for driving high brightness LED to keep the temperature and emission intensity of LED stable is presented. In one closed-loop control, a Peltier is used to control LED's temperature and its average power can be dynamically regulated as LED temperature changes. In another, sampling real emission intensity of LED and comparing with expected intensity is repeatedly operated to make the real intensity follow the expected intensity. Design of LED driving system is demonstrated, and the thermostatic control effect and stability of LED spectrum are tested. The test results show that the error of LED temperature control is about 0.1°C corresponding to a center wavelength shift of 0.015 nm for a red LED and the emission intensity error for the same LED is within 0.1%.