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I am facing annoying issues when converting 24V AC to 12 V DC. I want run 30 W LED and I have a limitation in input that I can only use 24V AC output of a transformer. I have the circuit as shown, but the problem is that the LED doesn't glow much, it is getting 12v but I am not sure about the current and R1 (as in figure) heats up very much.

Please help me reach my goalMultisim simulation.

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    \$\begingroup\$ Do you think R1 will be limiting the available current? \$\endgroup\$
    – Solar Mike
    Mar 17, 2020 at 12:36
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    \$\begingroup\$ LED datasheet required. \$\endgroup\$
    – user16324
    Mar 17, 2020 at 13:43
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    \$\begingroup\$ You've made your schematic very difficult to read for yourself and for everyone else. Put V+ on top and negative / GND on the bottom. See electronics.stackexchange.com/questions/152625/… for a well laid-out version of your schematic. \$\endgroup\$
    – Transistor
    Mar 17, 2020 at 14:47
  • \$\begingroup\$ "Please help me reach my goal" Please state what your goal is. \$\endgroup\$
    – winny
    Mar 17, 2020 at 14:51

2 Answers 2

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The LM7812CT provides 12 volts at up to 1 amp. That's a typical maximum continuous output power of 12 watts.

I want run 30Watts LED

There's your first problem. A 7812 is inappropriate for that power level.

Your second problem is the 1 kohm resistor will not pass anything like enough current to make a powerful LED operate without burning. Try something like this: -

enter image description here

You'll still need the bridge rectifier and reservoir capacitors but those capacitors will need to be hundreds of uF, possibly 1000 uF or more to get a reasonably smooth DC output voltage with an AC input frequency at only 50 Hz.

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  • \$\begingroup\$ what adjustment do you suggest i should make? \$\endgroup\$
    – Qizal Khan
    Mar 17, 2020 at 13:02
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    \$\begingroup\$ Use a buck current regulator circuit. \$\endgroup\$
    – Andy aka
    Mar 17, 2020 at 13:13
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Why don't you add a 2:1 autotransformer after your 24 ac? You'll have lower cos(phi), but for that much power, not really a matter. Then you use your straightener and a couple of capacitors in parallel.

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  • \$\begingroup\$ This does not answer OPs question. \$\endgroup\$
    – winny
    Mar 17, 2020 at 14:51

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