Hello. I have a 20 V dc power supply and a second power supply which has 2 linear regulators, L7812 and L7805 in cascade.
I installed the L7812 and L7805 onto a heat sink but the heat sink is a little bit small and it heats up to about 47 C. I know that in this moment it should be ok, but if the temperature in my room will rise to lets say about 30 C then I don't know if it will be any good.
I already made the PCB (before I saw this problem), and I found that the single solution is to install a resistor in series with D1, between the K of D1 and the + terminal of the capacitors. I made some calculations and tests, and it seems that a 33 R resistor will be ok.
Also, I cannot install a better heat sink (a larger one) because the enclosure for this project is too small.
Are there any better ideas to reduce the voltage on the input of 7812 ?
I installed the L7812 and L7805 onto a heat sink but the heat sink is a little bit small and it heats up to about 47 C. I know that in this moment it should be ok, but if the temperature in my room will rise to lets say about 30 C then I don't know if it will be any good.
I already made the PCB (before I saw this problem), and I found that the single solution is to install a resistor in series with D1, between the K of D1 and the + terminal of the capacitors. I made some calculations and tests, and it seems that a 33 R resistor will be ok.
Also, I cannot install a better heat sink (a larger one) because the enclosure for this project is too small.
Are there any better ideas to reduce the voltage on the input of 7812 ?
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