Ad
related to: heat sink calculation for mosfet circuit analysis
Search results
Results From The WOW.Com Content Network
Generally, forced convection heat sink thermal performance is improved by increasing the thermal conductivity of the heat sink materials, increasing the surface area (usually by adding extended surfaces, such as fins or foam metal) and by increasing the overall area heat transfer coefficient (usually by increase fluid velocity, such as adding ...
The heat sink thermal resistance model consists of two resistances, namely the resistance in the heat sink base, , and the resistance in the fins, . The heat sink base thermal resistance, , can be written as follows if the source is a uniformly applied the heat sink base. If it is not, then the base resistance is primarily spreading resistance:
The heat flow can be modelled by analogy to an electrical circuit where heat flow is represented by current, temperatures are represented by voltages, heat sources are represented by constant current sources, absolute thermal resistances are represented by resistors and thermal capacitances by capacitors.
Temperature increase becomes relevant for relatively small-cross-sections wires, where it may affect normal semiconductor behavior. Besides, since the generation of heat is proportional to the frequency of operation for switching circuits, fast computers have larger heat generation than slow ones, an undesired effect for chips manufacturers.
Heat sinks and other cooling devices and methods are now required for many integrated circuits including microprocessors. Power MOSFETs are at risk of thermal runaway . As their on-state resistance rises with temperature, if the load is approximately a constant-current load then the power loss rises correspondingly, generating further heat.
TO-220 packages can be mounted to a heat sink to dissipate several watts of waste heat. On a so-called "infinite heat sink", this can be 50 W or more. The top of the package has a metal tab with a hole used to mount the component to a heat sink. Thermal compound is often applied between package and heatsink to further improve heat transfer.
Heat pipes may also be added to aluminum or copper heat sinks to reduce spreading resistance. Shape – Thermal transfer takes place at the surface of the heat sink. Therefore, heat sinks should be designed to have a large surface area. This goal can be reached by using a large number of fine fins or by increasing the size of the heat sink itself.
The heat dissipation in integrated circuits problem has gained an increasing interest in recent years due to the miniaturization of semiconductor devices. The temperature increase becomes relevant for cases of relatively small-cross-sections wires, because such temperature increase may affect the normal behavior of semiconductor devices.