Therefore we need a resistor so that the capacitor can discharge properly after switching off the power supply. Bleeder resistor helps to achieve. How Electronic Components Work A New Multi Function Power Supply Unit For My Embedded Lab Resistor Power Rating Derating And Temperature Coefficient Thus a resistor of standard value is connected in parallel with the capacitor which helps in discharging after the curtailment of power. Function of resistor in power supply . So a resistor is used to limit the current. Before we learn the formula for calculating and optimizing resistor and capacitor values in a transformerless power supply it would be important to first summarize a standard transformerless power supply design. Analyzing a capactive power supply. The three diodes rectify the 3 phase voltages and combine them feel them via jp6 and r148 a