Capacitors generate heat via dielectric losses and connection losses between the dielectric and the terminals. These losses can be modeled as a series combination of the capacitor and ESR. Thermal changes can be calculated simply heat generated minus the heat dissipated. The heat rise during operation can then be expressed as a thermal resistance with units of ℃/watt.
Thermal management systems are required in electronic devices as they generate heat. This heat affects the reliability and lifespan of components, resulting in premature device failure.
As electronic devices decrease in size, the increasingly densely packaged circuits and components require the heat generated to be dissipated.
The development of electronics has resulted in the demand for efficient thermal management systems. A proper and efficient thermal management system allows electronic components to dissipate heat to the surroundings without exceeding the maximum allowable temperature.
The temperature of the surroundings, color, etc. influence heat dissipation from an electronic component. The geometry of electronic components also plays a major role in heat dissipation. Irrespective of the geometry, heat dissipation in electronic components is closely related to heat transfer mechanisms such as conduction, convection, and radiation. The heat dissipation capabilities of electronic components differ with each heat transfer mechanism and, in most cases, the dissipation results from combined processes.
In all heat dissipation methods, the only aim is to dissipate heat faster than the heat is generated. When the rate of heat generation in an electronic component is greater than the heat dissipation rate, there is more probability for the destruction of the device or component due to self-heating. Efficient thermal management techniques can improve the heat dissipation capabilities of electronic components, thereby preventing overheating and damage. We will discuss the heat dissipation capability of some passive electronic components in this article.
Heat dissipation capabilities of electronic component
When an electronic component works, energy is wasted in the form of heat energy. This heat energy increases the temperature of the component, and high temperatures can damage the device. The timely removal of generated heat is necessary for the lifespan and reliability of the electronic component.
The heat dissipation capability of an electronic component refers to the heat transfer process in it. The heat dissipation of electronic components occurs when they are hotter than their surroundings. The heat flows from higher temperatures to lower temperatures. Maintaining low-temperature surroundings is very important for heat removal from electronic components.
The temperature difference is an important parameter determining the heat dissipation capability of an electronic component. With the temperature difference, the mode of heat transfer changes. It may be conduction, convection, radiation, or a combination of them. The heat dissipation rate in an electronic component also differs with each of these processes. The amount of heat dissipated through conduction will be different from that of natural convection. The heat dissipation rate increases when natural convection shifts to forced convection. Some of the other factors that influence heat dissipation are the design or geometry, environmental characteristics, operating currents, etc.
Let’s discuss the heat dissipation in inductors and heating capacitors.
Heat dissipation in inductors
The proliferation of switching power supplies has introduced a lot of power inductors, otherwise called reactors or choke coils, in electronic systems. The trend of high power density has reduced the overall size of the circuit, including inductors. As the size gets reduced, the heat dissipation of inductors becomes of great concern.
The heat dissipation capability of an inductor is directly related to its surface area. The higher the surface area, the larger the amount of heat that gets dissipated in a short duration. As inductors are made of a core and windings, the mounting method and positioning of the core and windings play a significant role in heat dissipation. For example, the heat dissipation of windings is easier in a toroidal inductor compared to an E-type inductor. In E-type inductors, the heat dissipation capability of the core is higher than that in the toroidal inductors. Various thermal management techniques such as natural air cooling, liquid cooling, forced air cooling, and phase change cooling can be implemented for increasing the heat dissipation capability of inductors.
Heat dissipation in heating capacitors
Capacitors are often used in electronic circuits. The capacitor impedance consists of resistance as well as reactance. When the capacitor is subjected to a significant amount of ripple voltage or current, power is dissipated in the resistive component of the capacitor in the form of heat. The heat generated increases the temperature of the capacitor and causes heating. The temperature rise in a capacitor is dependent on the internal heat generation rate and heat dissipation rate to the external surroundings.
The heat dissipation capability of the capacitor is determined by the thermal characteristics of the capacitor surface and the thermal conductivity of the capacitor’s medium that separates it from its surroundings. The heat withstanding capacity of the leads, lugs, and terminals also affects the heat dissipation capability of the capacitor. The heat dissipation of the capacitor should be such that it does not allow the capacitor temperature to exceed the maximum rated value given in the datasheet.