PowerBench Thermal Simulation Includes Cold-Wall Cooling

June 11, 2018
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Vicor offers powerful simulation tools in the PowerBench online suite that address both thermal and electrical performance. Our applications engineers often find that customers aren’t aware of some of the capabilities of the tools, particularly the availability of features such as support for cold wall cooling.

Once you have selected Simulators from the PowerBench Tools menu, you are presented with a range of different Vicor power components that can be simulated. In this example we will use a DCM (DCM3623T36G06A8x00).

 

Basic Thermal Simulation

Starting thermal simulation is very easy: simply select “Thermal” as the simulation type in the drop-down menu at the top of the window.

Figure 1 - The Thermal Simulator

To run a simulation with the default thermal environment, just click the Simulate button, and the results are displayed at the bottom of the page. If at any time you need to go back to the default settings, just click the restore settings button and it will reset the values.

Figure 2 - Simulation Results

In the example with all default values, we can see that the operating temperature is 70°C, well within the capabilities of the DCM.

 

Changing the Inputs and Outputs of the DCM

Let’s assume that we want to simulate a larger load – for example 30A. By simply clicking on the load, we can set the new value for current and simulate again.

Figure 3 - Change Load

It’s easy to change other circuit parameters by clicking on them: for example, the input voltage or trim resistor can be used to simulate different input and output voltages.

 

Changing Thermal Design

The simulator allows for the parameters of the thermal management solution to be changed easily, reflecting a different design to cool the system. By clicking on “Click to edit” at the top of the Thermal Management box, we can then change the thermal environment.

Figure 4 - Change Cooling

In this case let’s increase the ambient temperature and decrease the airflow, while keeping the same heat sink for cooling. We will also make the simulation more accurate by adding a PCB temperature to take account of cooling through the pins of the DCM.

Figure 5 - New Thermal Parameters

When we simulate this environment, the operating temperature is 109°C. This is within operating conditions, but starting to get a little close to the maximum temperature. A relatively small increase in output current and temperature results in the DCM reaching its maximum operating temperature:

Figure 6 - No Thermal Headroom

At this stage we might choose to increase airflow, but it could be more effective to use a heat sink on both sides of the DCM, something that is set up by clicking a radio button in the simulator.

Figure 7 - Double Sided Cooling

This brings the operating temperature down to 111°C, providing a little extra headroom even in these more challenging conditions.

 

Cold Plate Cooling

The simulators can also determine temperatures when a cold plate (e.g. the wall of an enclosure) is used instead of a heat sink. This mode is selected using the same pop-up box and using the drop-down to select cold plate as the cooling type.

Figure 8 - Defining Cold Plate

Cold plate cooling is obviously more effective than a heat sink, and in this case, we see that using cold plate cooling on just one side reduces the operating temperature to below 100°C.

Figure 9 - Using Cold Plate Cooling

A Flexible Thermal Simulation Tool

The Vicor simulators are not just for determining electrical performance; they also provide valuable thermal simulation capabilities. By using the simulator in thermal mode, power engineers can quickly determine if their planned cooling strategies will remove sufficient heat from a Vicor power component. If more cooling is required, the simulator allows experimentation with changes to the heat sink, airflow and even cooling strategy to achieve the optimum thermal solution.

 

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