LM2596 TO-220 Package heat sink size

Mehul Laliwala

Other Parts Discussed in Thread: LM2596

I am trying to figure out what size of heat sink will I require for LM2596 TO-220 package. My input voltage is between 34-38 VDC unregulated, and my output is 24VDC. My load current is 1.1 Amp. My ambient is at 25 C and my max ambient is 61 C.

The datasheet does not show heat sink for voltage above 20VDC.

Thanks!

over 10 years ago

0 Frank De Stasi over 10 years ago

TI__Guru 72755 points

I have created a Webench design for you parameters. I have attached a summary with a suggested heat sink. If you wish to play around with the design, send your email address to simpleswitcherapps@ti.com and I will send you the link to the complete design.

webench_design_433359_92_119357483[1].pdf

0 Mehul Laliwala over 10 years ago in reply to Frank De Stasi

Prodigy 30 points

Frank how would I calculate the input Cin at 50Hz? I am stepping down from 120 VAC to 24 VAC, and I am full bridge rectifying to 34 - 38 Vdc.

0 Frank De Stasi over 10 years ago in reply to Mehul Laliwala

TI__Guru 72755 points

The bulk filter for the 50Hz supply is not very critical. You can use the equation: C=(I*T)/(2*dV). From Webench the input current is just under 1A, so we can use 1A to be conservative. Your 50Hz has a period of 20ms, so T=0.02. Let us choose a ripple of 2V, so dV=2. This gives a 5000uF capacitor. The next standard value is 4700uF. So, I would use a 4700uF, 50V (or more) with an RMS current rating of 1A or more. However, you still need the CIN shown in the design schematic placed as close as possible to the LM2596. Also, try to use the layout suggested in the Webench design.

0 Mehul Laliwala15 over 10 years ago in reply to Frank De Stasi

Prodigy 10 points

Thanks Frank!

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LM2596 TO-220 Package heat sink size