Direct impingement cooling of LED by Piezo fan

In this paper, an innovative heat management solution for the Light Emitting Diodes (LEDs) based on direct impingement cooling by Piezo fan has been proposed and evaluated. Round Piezo fans with 26 to 30 mm blade diameter, 1 to 5 mm fan thickness and narrow flow orifice (~ 3 to 7.5 mm) were developed which could provide very high velocity air jet (> 10 m/s) for impinging heat source footprint directly. These fans were driven at high operating frequency (300 to 550 Hz) and voltage (40 to 50 V_rms) to get high impact air jet at fan outlet. Different test cases have been studied to demonstrate and characterize the cooling capability of the Piezo fan based thermal solutions. Direct impingement cooling of the 5 × 5 mm² heat source with Piezo fan (30 mm diameter, 1.1 mm thickness and 7.5 mm orifice width) inclined at 35° to horizontal was tested which was able to reduce source temperature by 3 to 4 times as compared to natural convection cooling. Similarly, incorporation of Piezo fan for cooling multiple chips (x5) LED package with 9 W output heat load reduced the source temperature by more than 42 °C. Automotive headlamp with two LED packages and single heat sink was impinge cooled by two dedicated Piezo fans which reduce the source temperature by 7.6 °C and enhance the heat sink heat dissipation capacity by 48% due to improvement in the enclosure heat transfer coefficient. Piezo based impingement cooling can therefore increase the heat removal from heat source as well as can reduce the size of the heat sink designed for natural convection cooling. Based on these results, impingement type Piezo fan can be classified as standalone as well as heat sink integrated cooling solution for LED packages.