2022年11月14日 · With a single transistor, the heat injected into the heatsink is injected in one place and spreads out from there, making the place the single transistor is mounted the hottest spot on the heatsink. This can be important when the thermal drop between the case of the transistor and the heatsink becomes significant.

2023年11月12日 · Without a heatsink case temp will be within a few degrees of junction temp. For most packages power dissipation without a heatsink is 1 - 2W max. At 70A, assuming its fully switched on, its dissipating approx 70^2 * 0.0033 = 16.2W. Without a reasonable heatsink your MOSFET will fry instantly.

2018年4月7日 · "A device is mounted on a heatsink. It is started from cold and run for five minutes before being switched off. The device produces 30W of losses and the thermal resistance between the device and the heatsink is 1.7C/W. The thermal capacitance of the heatsink is 100J/C. The ambient temperature is 40C.

2021年12月12日 · HI all, So i want to design a 12V 4A power supply. I am using the National Semiconductor Volt. Reg. Handbook from 1980, but section 8.3 isnt completely clear to me regarding the selection of the Bridge Rectifier. It states that the RMS Capacitor current can be 2-3 times the load current, so in...

2019年7月3日 · Those are the whole kit except you should be able to get black anodized for the same price which is supposed to radiate the heat better. Also apparently now the silicone sheet is preferred over the grease. Be careful with the mounting screw pressure to ensure it sits flat and in full contact on the heatsink.

2010年5月27日 · It works, but if and only if the heatsink is firmly connected to circuit ground, and the connection between the heatsink and the TO-220 tab is well made with star washers. The possibility of a fault due to a poor connection is great enough that actually connecting pin 2 to a ground trace is worth the effort.

2014年1月29日 · If the heatsink is electrically connected to ground (or any other potential except Vout), then the mounting kit is used to isolate the tab from the heatsink. Note that the bolt used to mount the LM317 to the heatsink must not short the two. Use the small Teflon shoulder washer supplied in the kit to prevent that...

2010年9月3日 · Yeah, one of the previous post sounded like you wanted to leave out the mylar washer. You still need to isolate the TO-220 from the heatsink, as well as insulating the screw from the heat-sink. There are also washers that have a similar electrical insulating effect, but are better heat conductors than a dry mylar washer (without heatsink grease).

2022年6月2日 · The heatsink is isolated from ground, just mounted on a PCB in some cases. This is not a common practice, but is sometimes used that way. A schematic will seldom show this, it is up to the person looking at the heatsink to determine how the transistors are mounted.

2010年5月9日 · I am using an IRFZ44N to switch 12 to 14.5vdc at 5a maximum; the load is purely resistive. The duty cycle will be about 50% on/50% off and will be switched on/off about twice per minute. The gate voltage is 8v and the ambient temperature will be 40 degrees C max. How do I calculate cooling...