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I am new to power electronics. I am designing an isolated DC-DC converter using an LT3002 and a ZA9672-BED (12V, 1A) transformer from Coilcraft. My target is 12V DC output with 10W power. The transformer can provide 12V with 1A.

I want to use an LT3088 linear regulator at the transformer's output to get a stable 12V. To do this, I must get around 14V at the ZA9672-BED (12V, 1A) thanks to the LT3088.

I am confused about if it can provide 14V (10W) or higher voltage on the ZA9672-BED (12V, 1A) rated 12V, 1A transformer. Will that cause any problems?

Circuit:

enter image description here

Result:

enter image description here

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    \$\begingroup\$ Show your proposed flyback circuit design please. There is some confusion in the words you are saying that should be solved with a schematic. You talk about the transformer's output connecting to the LDO regulator but, I don't seriously think you mean that. Please show your proposed design schematically. Add data sheet links for the two chips you mentioned as well. \$\endgroup\$
    – Andy aka
    Apr 10, 2023 at 12:54
  • \$\begingroup\$ I added all of the related information. \$\endgroup\$ Apr 10, 2023 at 13:09

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First of all, it's not recommended to use components at their maximum rated power or very close to it. You should always leave some "room", at the very least 10-20% to make sure your circuit will not fail or misbehave due to overload.

Second of all, you can set the output voltage from the transformer with resistors connected to RFB, RREF and TC pins of the LT3002, as specified in its datasheet on page 5:

The ratio of the RFB resistor to the RREF resistor, times the internal voltage reference, determines the output voltage (plus the effect of any non-unity transformer turns ratio).

Third of all, do you really need the LDO at the output? Do you know why are you using it?

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  • \$\begingroup\$ I want to limit the output power to 10W. LT3002 and the transformer can provide 12W at 12V output. I think that if I can use LDO with a maximum output current of 800mA at 12V, like in the circuit above, I can limit the output power while having a stable 12V. But I must increase the output voltage (out_flyback) to get 12V from LDO. By increasing Rfb, I can get 14V, but the transformer (ZE9672-BED) is rated for 12V. My question is increasing this voltage to 14V in the circuit (still 10W) might be a problem for the transformer? \$\endgroup\$ Apr 10, 2023 at 13:25
  • \$\begingroup\$ @FiratDagkiran No, it wouldn't be a problem, that's a relatively small change. You shouldn't use the LDO's absolute current limit to limit the output power. Depending on your load, the power can be limited via constant voltage, constant current or both. \$\endgroup\$ Apr 10, 2023 at 16:42

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