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I'm new in electronics. I want provide 9V (VVD9) and 5V (VCC) for my electronic board including power mosfets (IRF 3205), high power LED (14V-3.5A), micro-controller (at-mega16), and etc. I use this strategy to provide those voltages for aforementioned elements as depicted below:

First image

For more details I provide the main part of circuit as shown below. The circuit provides strobe (5Hz-2%duty cycle) for LEDs and a Camera:

Second image

I have two questions:

  1. Is using that strategy (shown in first image) good?
  2. As depicted in first image, input voltage is 24V. I Also use it for high power LEDs (in second image). Is there any side effect? (for example, voltage drops when LEDs are pulsing).

Any help or suggestion will be appreciated.

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  • \$\begingroup\$ How much current will your project draw from the 9V and 5V supplies, both peak current and average current? \$\endgroup\$
    – Elliot Alderson
    Commented Sep 19, 2019 at 14:43
  • \$\begingroup\$ 5v volt is used for micro controller and 9 volt is used for mosfet drivers. Mosfet drivers are tc4428. The current on 7809 and 7805 is less 100mA. The simulations also show it. \$\endgroup\$
    – Babak.Abad
    Commented Sep 19, 2019 at 15:26
  • \$\begingroup\$ Possible duplicate of Using Linear Voltage Regulators in Series? \$\endgroup\$
    – The Photon
    Commented Sep 19, 2019 at 15:33

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Is using that strategy (shown in first image) good?

It's fine, and using multiple linear regulators will spread the power dissipation from the current across multiple parts. The problem is the current is in series, so the power dissipation will increase for the 7812 and 7809. The most important thing is to keep the regulators from going over their temperature rating. This means you must calculate the max current through each of the parts and multiply it with the voltage drop to find max power dissipated. The second thing is not to use more current than the part can tolerate. I would estimate the power of the LCD and ATmega to be under 200mA, but this needs to be calculated by you or measured, most regulators support at least 500mA and some 1A (depends on the package usually, which is not listed).

As depicted in first image, input voltage is 24V. I Also use it for high power LEDs (in second image). Is there any side effect? (for example, voltage drops when LEDs are pulsing).

It is fine to use 24V for the LED's and for the regulators. One problem is the first regulator has a 12V drop, at 500mA (which is a ballpark number) this would be 6W dissipated. At 200mA it would be 2.4W and 100mA would be 1.2W. Make sure the 7812 has the right package and calculate the temperature rise

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  • \$\begingroup\$ Note that the LM78xx series has integrated thermal overload and short circuit protection: ti.com/lit/ds/symlink/lm340.pdf \$\endgroup\$
    – Caleb Reister
    Commented Sep 19, 2019 at 16:55
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    \$\begingroup\$ I think you mean "spreads the power dissipation" at the beginning, yeah? \$\endgroup\$
    – Hearth
    Commented Sep 19, 2019 at 16:57
  • \$\begingroup\$ @CalebReister Yes, However the OP has not defined what regulators they are using \$\endgroup\$
    – Voltage Spike ♦
    Commented Sep 19, 2019 at 17:30

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