Quote:
Originally Posted by GriffinRU
We will continue next week-end, need to go.
Dynamic loss is fixed with fet, each fet has a capacitance in the gate (value dependant on temp, load...) to charge and discharge this capacitor requires energy, so more fet's more energy.
Conduction loss would be related to Rdon and more fet's lower value, so good thing, but as you can see you need to keep balance...
I will check e-mail later, and let you know.
Keep in mind TO-220's and D-Pak's are huge packages and can easily absorb ~1W without heatsink, but they are not as fast as smaller, tuned fet's.
Your Amp has a pretty sized heatsink, right :)
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Heat sink issues will be no problem as the design I have in mind will allow for a very good heat sink to be used without sacrificing size (Compared to much larger ESCs). Look at this article in Power Electronics Technology
http://powerelectronics.com/thermal_...osfet_cooling/. The LFPAKs that I have been mentioning are being compared to the other package found on controllers such as the Schulze 40.160, Actronic 120, Jeti SPIN170-300 and the ones I'm having made. This article is saying things like, "This fact also opens the possibility of further reducing the pc board space occupied by the power MOSFETs by using physically smaller devices and placing those devices closer together. To investigate this possibility, another simulation was carried out where each pair of D2PAK MOSFETs in the H-bridge circuit was replaced with three LFPAK devices.
The LFPAK package is much smaller than the D2PAK, occupying the same pc board footprint as the familiar SO-8 package. However, unlike the SO-8, the LFPAK is a true power package that incorporates a bottom metal contact, which provides an effective heat path out of the device. There is an additional thermal pathway between the top of the device silicon and ambient through the top part of the encapsulation.
Although the LFPAK solution increases the total number of power packages used, the total board area occupied by this solution is significantly less than for the D2PAK case because the LFPAK package is much smaller than the D2PAK." and "In the last few years, there have been significant advances in the packaging of MOSFETs, including the introduction of the power SO-8 package. Bottom-side cooling can now be used successfully to transfer heat through the pc board, even when smaller power packages like the LFPAK are used in place of the D2PAK. The package on-resistance and inductances for these smaller package types are also significantly lower. The total losses in a system caused by these sources are therefore reduced significantly, even with the additional devices needed when using the smaller package types in place of larger MOSFETS.
The greatest advantage when switching from D2PAK to LFPAK is the resulting reduction of board space occupied by the MOSFETs, since pc board top copper is not needed to radiate heat. The smaller MOSFETs can be placed closer together, and the previously occupied board space is made available for other components." The components that I have in mind though are much smaller measuring 3mm Length x 2mm Width X 0.8mm height. If this works, it should make a very powerful controller.