A temperature controller for high power light emitting diodes based on resistive heating and liquid cooling

• A temperature controller with liquid cooling and resistive heating for LED research.
• Pulse width controlled solenoid valve is used to control the liquid flow.
• Fast temperature change of 0.5 K/s with maximum cooling power of 90 W.
• Temperature range of 273–386 K achieved with temperature stability of ±0.03 K.

This paper describes a temperature controller that can be used to stabilize and control the p-n junction temperatures of high power light emitting diodes (LED) for research purposes. The controller utilizes resistive heating and liquid cooling instead of the traditional thermoelectric element based on Peltier effect. This construction offers higher temperatures and more efficient cooling than the Peltier coolers. Both heating and cooling are controlled with the same PI control electronics. The controller was tested with LEDs of 2.5 W electrical power, in the heat sink temperature range of 273–386 K. A stability of ±0.03 K was achieved, and the time constants for 20-K temperature steps with typical LEDs of 2.5 W power, were 72 s in the heating, and 54 s in the cooling mode.