There are three effective methods for cooling a power module

There are three basic methods for power module energy transfer from a high temperature area to a low temperature area: radiation, transmission, and convection.

Radiation: Electromagnetic induction transfer of heat between two objects of different temperature.

Transmission: Transfer of heat through a solid medium.

Convection: Transfer of heat through a fluid medium (air).

1, radiation heat dissipation

When two interfaces of different temperatures are confronted, a continuous radiative transfer of heat is caused.

The final influence of radiation on the temperature of some objects depends on many factors: the temperature difference of each component, the orientation of related components, the smoothness of the surface of components and the spacing between them.

Because there is no way to quantify this factor, coupled with the influence of the radiant kinetic energy exchange of the surrounding environment itself, it is difficult to calculate the damage of radiation to temperature, which is complicated and difficult to accurately calculate.

In the specific application of switching power converter control module, it is unlikely that radiant heat dissipation is used as the cooling mode of converter alone.

In most cases, the radiation source only dissipates 10% or less of the total heat. Therefore, the radiation heat dissipation is generally only as an auxiliary way in addition to the key heat dissipation method, and the thermal design scheme generally does not consider its influence on the temperature of the power module.

In the specific application, the temperature of the converter control module is higher than the natural environment temperature, so the radiation kinetic energy transfer is conducive to heat dissipation.

However, in some cases, the temperature of some heat sources around the control module (electronic device board, high-power resistance, etc.) is higher than that of the power module, and the radiant heat of these objects will instead make the temperature of the control module rise.

In the heat dissipation design scheme, the relative positions of the peripheral components of the converter control module should be arranged scientifically according to the influence of heat radiation.

When the heating element is close to the converter control module, in order to weaken the heating effect of the radiation source, the thin fin of the heat shield should be inserted between the control module and the heating element.

2, transmission heat dissipation

In many applications, the heat generated from the power module substrate is transferred to distant heat dissipation surfaces by heat transfer components.

In this way, the temperature of the PSU substrate will be equal to the temperature of the cooling surface, the temperature of the heat transfer component, and the sum of the temperatures of the two surfaces.

The thermal resistance of heat transfer components is proportional to the length L between the two, and inversely proportional to the cross-sectional area and heat transfer rate between the two, using appropriate raw materials and cross-sectional area, but also can effectively reduce the thermal resistance of heat transfer components.

Where installation space and cost are acceptable, the heat sink with the least thermal resistance should be used.

It should be kept in mind that when the PSU substrate temperature is slightly reduced, the mean time to failure (MTBF) will increase significantly.

The production and manufacturing of raw materials for heat sink is the key factor affecting the efficiency. We must pay attention to many aspects when selecting.

In most applications, the heat generated by the power module will be transferred from the substrate to the radiator or heat transfer components.

However, the temperature difference between the surface of the power module substrate and the heat transfer component must be controlled. The thermal resistance is connected in series in the heat dissipation control loop. The temperature of the substrate should be the sum of the surface temperature and the temperature of the heat transfer component.

If left unchecked, the rise in surface temperature will be very noticeable.

The total surface area should be as large as possible, and the surface smoothness should be within 5 mil (0.005 ft).

In order to better remove the convex and concave surface, you can fill the surface with thermal adhesive or heat transfer pad.

With appropriate measures, the surface thermal resistance can be reduced to less than 0.1 ℃/W.

The temperature can be reduced and TAmax can be increased only by reducing heat dissipation and thermal resistance (RTH) or power consumption (Ploss). The maximum power of the switching power supply is related to the application temperature. The main influencing parameters include loss output power Ploss, thermal resistance RTH, and maximum switching power shell temperature TC.

The switching power supply with the best efficiency and heat dissipation has a lower temperature.

In nominal output power output, their usable temperature will be surplus.

The switching power supply with low efficiency or weak heat dissipation has a higher temperature.

They must be air-cooled or derated for application.

3, convection heat dissipation

Convective heat dissipation is the most common way of heat dissipation in AEP power converters. Convection is generally divided into natural convection and forced convection.

Heat transfer from the hot block surface to the lower temperature of the surrounding static gas, called natural convection;

The transfer of heat from the surface of the hot block to the liquid gas is called forced convection.

The advantages of natural convection are very easy to achieve, no electric fan, lower cost, and high credibility of heat dissipation.

However, the volume of heat sink required to achieve the same substrate temperature is very large compared to forced convection.

Sinda Thermal is a professional and experienced heat sink manufacturer, our factory has been founded over 8 years, we are providing varieties of heat sinks to the global customers, we can offer the optimized thermal design and great quality heat sinks. Please contact us freely if you have any thermal requirements.