High power led driver circuit using LNK403EG

This high power led driver circuit is designed using LNK403EG IC designed by Power Integrations which can drive an LED string of 18 V at a current of 0.38 A (both nominal) from an input voltage range of 90 VAC to 265 VAC.
The topology used in this high power led driver circuit is an isolated flyback operating in continuous conduction mode.

Output current regulation is sensed entirely from the primary side eliminating the need for secondary side feedback components.
Fuse F1 fuses the input and BR1 rectifies the AC line voltage. Inductor L1-L3, C2, R2, and R3 form the EMI filter .
Diode D6 and high-voltage SMD ceramic capacitors C16 and C17 detect the peak AC line voltage. This voltage is converted to a current into the VOLTAGE MONITOR (V) pin via R4 and R7. This current is also used by the device to set the input over/ undervoltage protection thresholds. The V pin current and the FEEDBACK (FB) pin current are used internally to control the average output LED current.
Diode D3, C19, R5, R9 and R18 form the primary bias supply. This supplies the IC operating current into the BYPASS (BP) pin through D4 and R10 during normal operation. Resistor R5 provides filtering to improve output regulation while R9 and R10 act as a minimum load; this improves dimming range by causing the bias voltage to reduce as the output current falls.
A current proportional to the output voltage from the primary bias winding is fed into the
FB pin through R15. This information together with the line input voltage and the drain current are used to maintain a constant output current.
Components R12, R13, R20, R17, D7, Q1, C13, VR2, and Q3 in conjunction with R16 reduce the inrush current when the TRIAC dimmer turns on. This prevents the line inductance from peak charging input capacitance above the line voltage, causing flicker.