Electronic devices such as central processing units (CPUs) and digital signal processors (DSPs) are comprised of various electronic components including active elements such as transistors and passive elements such as capacitors. Part of electric energy for driving the electronic components is converted into thermal energy and dissipated. Since the performance of electronic components normally depends on temperature, dissipated heat affects the electronic components and, in turn, the performance of the electronic device. Thus, technology for cooling an electronic device is extremely important to control an electronic device properly.
An example of technology for cooling an electronic device is air-cooling using an electric fan. In this method, an electric fan is provided to face the surface of an electronic device. Air taken in from an air inlet is blown to the surface of the electronic device by the electric fan. Air heated as a result of absorbing heat generated from the surface of the electronic device is discharged from an air outlet. Thus, the electronic device is cooled by removing the heat generated from the surface of the electronic device by using the electronic fan.
A device called a heat sink for dissipating heat is also used commonly. A heat sink is usually designed to have a large heat dissipation surface in order to transfer heat from a heat source such as an electronic device to a cool fluid or air that surrounds the electronic device. Heat generated from an electronic device is conducted to a heat sink and dissipated through an extensive heat dissipation surface of the heat sink.
A cooling method using an electric fan and a heat sink in combination is generally used to cool a semiconductor chip.
Time response of an electric fan or a heat sink to temperature variation is generally slow compared to variation in the amount of heat generated in an electronic device. In other words, the related-art cooling method cannot efficiently cool an electronic device in the face of minute-by-minute variation in the amount of heat generated in an electronic device. This necessitates holding extra cooling capacity in reserve in order to maintain the reliability of an electronic device. One drawback of this approach consists in large power consumption and noise of an electric fan. Another drawback is that the volume 6f an electric fan has to be larger than is necessary.