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Transformerless power supply calculator

This tool calculates output parameters of a transformerless power supply where a capacitor is used to drop the voltage. The formulas and information come from Microchip application note AN954, written by Reston Condit.

The capacitor C1 must be X2 type capacitor.

Warning: transformerless power supplies provide no isolation from mains power, and are very dangerous. You must use isolation transformer whenever you want to connect anything, such as scope, DVM, or any other external equipment to the circuit. Even with isolation transformer high voltages are present, be very careful.

Input variables
Mains frequency Hz
Mains RMS voltage V
D1 breakdown voltage V
C1 nominal capacitance uF
R1 nominal resistance Ohms
D2 forward voltage drop V
C2 value uF
C1 tolerance %
R1 tolerance %
Results
Nominal output voltage below current limit V
Output ripple at nominal current mV
Available nominal current mA
Worst case available current mA
Best case available current mA
Worst case R1 power dissipation (pick double) W
Worst case D1 power dissipation (pick double) W
Worst case D2 power dissipation (pick double) W
Minimum rated voltage for C1 (pick double) V
Total consumed power max W

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