I have optocouplers in my AVR Controlling PCB so The question is:

In order for secure protection, is it recommended to use two separate power supplies: one for the Micro-controller side and other for the optocoupler power supply? I use opto for triggering one IGBT which have its own power supply (one bridge rectifier and one capacitance without transformer), which could not be used as power supply for microcontroler or opto. Clearly i have two option: using 2 power supply, 1th as micro and optocopler power supplier and the other as IGBT power supplier line.

using 3 power supply, 1th for micro, 2th as optocopler power supplier and 3th as IGBT power supplier line.

So as you can see in this schematic, we have two power supply: 1 +5D 2 +5A Opto The output of Opto's going to one Buffer (74LS240) and then going to IR2130.

So Could i have use one power supply instead of two power supply.

The output side is here: enter image description here


closed as unclear what you're asking by Neil_UK, CL., Voltage Spike, Daniel Grillo, pjc50 Jan 16 '17 at 11:51

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    \$\begingroup\$ What!? Why are you using an optocoupler? Usually if you have to resort to an optocoupler, they would be using separate or split up power supplies. Optocoupler are used to separate voltage levels in different circuits while allowing them to communicate with each other. \$\endgroup\$ – Bradman175 Jan 1 '17 at 10:21
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    \$\begingroup\$ Let's have a schematic diagram. It's a waste of everybody's time to discuss the deployment of multiple power supplies without one. \$\endgroup\$ – Neil_UK Jan 1 '17 at 11:14
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    \$\begingroup\$ Please describe what you want to archive, not the parts you want to interconnect. You probably saw optocouplers being used in some applications. You should understand why they've been used. Then it should become clear if and why you need optocouplers. \$\endgroup\$ – try-catch-finally Jan 1 '17 at 13:00
  • \$\begingroup\$ Added schematic. \$\endgroup\$ – 1st Jan 1 '17 at 14:34
  • \$\begingroup\$ Can you add the a schematic for the output-side circuits? \$\endgroup\$ – ThreePhaseEel Jan 1 '17 at 14:38

You're not providing two power supplies to be able to use the optocouplers, you're using optocouplers to be able to communicate between isolated circuits. Optocouplers are bulky and expensive, so if you could avoid using them, you would almost always prefer not to.

The optocouplers are used here to provide safety isolation between a high-voltage circuit and another circuit, since the "output side" could all potentially be connected to 220 V in a fault situation.

If you were to combine the +5D and +5A nets (and the two ground nets), then there would no longer be safety isolation between the two sides, and your users could be electrocuted due to a fault in your circuit.

  • \$\begingroup\$ Yeah, emphasis on the optocouplers are a safety isolation device part \$\endgroup\$ – Sam Jan 1 '17 at 21:08

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