This 15 watt led driver circuit is designed using LNK407EG.
This 15 watt led driver circuit is designed to drive an LED string of 30V at a current of 500 mA (both nominal) from an input voltage range of 90 to 265 VAC.
This integrated controller and 725 V MOSFET dramatically reduces the complexity and component count of the solution.
The key design goals were to achieve the highest possible efficiency and eliminate electrolytic capacitors .
This 15 watt led driver circuit is very simple and require few external electronic parts .
Inductor L2-L4, C1, R1 and R5 form the EMI filter and together with C9 (Y1 safety) capacitor allow the design to meet EN55015B conducted EMI limits. Capacitor C8 provides a low impedance path for the primary switching current, a low value of capacitance is necessary to maintain a power factor of greater than 0.9.
Diode D1 and high-voltage SMD ceramic capacitors C11 and C10 detect the peak AC line voltage. This voltage is converted to a current into the VOLTAGE MONITOR (V) pin via R2, R7 and R13. This current is also used by the device to set the input over undervoltage protection thresholds.
Resistor R10 also sets the internal references to select the line undervoltage threshold. Resistor R14 is added to further improve line regulation, providing a constant output current over the specified input voltage range.
Diode D2 and VR1 clamp the drain voltage to below the BVDSS rating (725 V) of the internal power MOSFET in U1. Diode D5 is necessary to prevent reverse current from flowing through the LinkSwitch-PH device (the result of the minimal input capacitance).
Diode D4, D6, C7, R3, R6 and R8 form the primary bias supply. This supplies the IC operating current into the BYPASS (BP) pin through D6 and R8 during normal operation.
Resistor R3 provides filtering to improve output regulation while R6 acts as a minimum load. Capacitor C13 is the supply decoupling for the LinkSwitch-PH. During start-up C13 is charged to ~6 V from an internal high-voltage current source tied to the device DRAIN (D) pin. Once charged the energy stored in C13 is used to run the device until the output and bias winding voltage rise and current is supplied via R8.
A disconnected load / overvoltage shutdown function is provided by D7, C14, R11, VR2, C12, R12 and Q1. A second bias winding output voltage is used to eliminate the delay introduced by the larger value of C7 compared to C14.
In the image below you can see the transformer design and electrical specifications.