Output Power and Gain Monitoring in RF CMOS Class A Power Amplifiers by Thermal Imaging; X. Perpiñà et al.; IEEE Transactions on Instrumentation and Measurement.The viability of using off-chip single-shot imaging techniques for local thermal testing in integrated radio frequency (RF) power amplifiers (PAs) is analyzed. With this approach, the frequency response of the output power and power gain of a Class A RF PA is measured, also deriving information about the intrinsic operation of its transistors. To carry out this paper, the PA is heterodynally driven, and its electrical behavior is down converted into a lower frequency thermal field acquirable with an InfraRed lock-in thermography (IR-LIT) system. After discussing the theory, the feasibility of the proposed approach is demonstrated and assessed with thermal sensors monolithically integrated in the PA. As crucial advantages to RF-testing, this local approach is noninvasive and demands less complex instrumentation than the mainstream commercially available solutions.
Thermal Management Strategies for Low and High Voltage Retrofit LED Lamp Drivers; X. Perpiñà et al.; IEEE Transactions on Power Electronics. Several thermal management strategies for LED drivers designed for high lumen retrofit LED lamps are studied by simulation and experimentation means. Depending on the driver output, two scenarios are analyzed: Low Voltage-High Current (18V-620mA) and High Voltage-Low Current (110V-85mA). Experiments (infrared thermography and thermocouples) and multiscale simulation approaches are used to assist both the lamp and driver board thermal design, as well as the driver proper integration in the lighting system. As a result, a heatsink based on an Aluminum hollow cylinder with polymer axial fins is designed and evaluated. The heatsink assessement is carried out with an LED board, in which the LED junction temperature is modeled and extracted by monitoring the LED board backside temperature. Additional experimentation to better integrate the driver is performed aiming at reducing the contact thermal resistance between the driver and the heatsink and improving the heat removal in the driver housing by including a material with a high thermal conductivity (i.e., dry silica sand or magnesium oxide powder). The proposed solution reduces the LED junction temperature up to 18% with respect to a reference lamp, whereas both drivers depict working temperatures around or below 125°C, when a working temperature of 90°C is considered.