How to Operate LED Driver Circuit?
The resistors R1 and R2 limit the inrush current from the AC mains supply. This AC voltage is further reduced by the AC capacitor C1 which drops the voltage by around 210V. This reduced AC voltage is then rectified by the bridge rectifier to obtain a rectified DC voltage of about 20V. This DC voltage is then filtered by the filter capacitor which allows the AC ripple signals to pass through it and the DC signal is thus fed to the regulator IC. This filtered and rectified DC signal is then regulated by the IC voltage regulator. The voltage regulator used here ensures a maximum output current of 100mA, which is further reduced to 20mA using the resistor. Thus a regulated output of about 12V, 20mA is used to drive two red LEDs.
The resistor R1 acts as a bleeder resistor allowing the capacitor C1 to discharge once the power is switched off. This provides a great deal of safety.