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enter image description here

I understand that the capacitor produces a resistance proportional to the 50 Hz of the mains input current, in this case 220 volts

But why is that resistance installed in parallel, what function does the resistance have?

Thanks

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    \$\begingroup\$ That resistor wouldn't be a 0603 sized SMD part. That size part can't handle the voltage, and the terminals would be too close together for that voltage. \$\endgroup\$
    – JRE
    Jan 16, 2021 at 9:31
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    \$\begingroup\$ If you build that thing, do not touch any part of it while it is plugged in. Safest is to close it up in a box so it can't bite you. \$\endgroup\$
    – JRE
    Jan 16, 2021 at 9:32
  • \$\begingroup\$ that resistor marked 0603 is mysterious, resistor numbers don't start with 0. \$\endgroup\$ Jan 16, 2021 at 10:37

2 Answers 2

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It is most likely a high value resistor to discharge the capacitor when the circuit is disconnected from the mains AC supply. This is purely for safety and not functionally required for the circuit.

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  • \$\begingroup\$ Thank you..., I had not thought of it \$\endgroup\$
    – Mario
    Jan 16, 2021 at 7:28
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    \$\begingroup\$ It may be similar to a 'bleeder' resistor. It is used for safety purposes. \$\endgroup\$
    – Kaswechiha
    Jan 16, 2021 at 8:54
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    \$\begingroup\$ Please mark the answer as accepted (check mark) if it is satisfactory to you. \$\endgroup\$ Jan 16, 2021 at 13:09
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This is transformerless power supply. Capacitor restrict current flowing. Resistor for discharging capacitor then main power is off for safety purpose. Also the circuit not complete. If main power on in peak of sinusoid, discharged capacitor make short circuit, current limited only by ESR of capacitor. Resistor in series should be added.

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  • \$\begingroup\$ Thanks for the information \$\endgroup\$
    – Mario
    Jan 17, 2021 at 7:52

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