The flyback converter shown in Figure above uses a member of the TinySwitch-III family (U2, a TNY279PN) to provide up to 1.8 A of load current to six, high-intensity, Luxeon LEDs (the LXHL series).The output voltage is slightly below the forward voltage drop of the LEDs. Therefore, when the LEDs are connected to the supply, it operates in constant current (CC) mode. If the LEDs are disconnectedfrom the supply, Zener diode VR1 provides voltage feedback, which regulates the output voltage at about 13.5 VDC.A 100 mΩ resistor (R11) senses the output current and an Opamp (U1) drives the optocoupler (U3), which provides feedback to U2.The TinySwitch-III family of devices regulate by disabling or skipping MOSFET switching cycles.source

The non-isolated buck converter shown in Figure above was designed around a member of the LinkSwitch-TN IC family, the LNK306DN (U1). A LNK306DN was selected since its minimum current limit (450 mA) ensures that it will be able to deliver the required 330 mA of output current.Diode bridge BR1 rectifi es the AC input while capacitors C1 and C2 fi lter it. Inductor L1 and RF1 attenuate conducted EMI. In case of a component failure, RF1 will act as a fuse.source

A flyback converter with no input capacitance operating in discontinuous conduction mode inherently provides a high power factor. The schematic shown in Figure above takes this approach and adds an output current limit to form a high power LED driver. The circuit description below highlights the key circuit differences between this and a standard fly back converter.To prevent large voltage transients due to AC line inductance or surges, a clamp circuit consisting of C4, D5 and R3 limits the DC bus voltage to a safe value. Once in steady state, the capacitor is effectively decoupled from the circuit by D5 so as to not impact Power Factor (PF). Resistor R3 provides a discharge path for C4.source

The isolated flyback converter shown in Figure above is a single stage PFC-based LED ballast power supply. It can deliver an average output current of 1.67 A at 12 V, which makes it ideal for driving high current LED arrays. High power factor is achieved by operating a flyback converter in discontinuous conduction mode with minimal input capacitance. This results in a drain current envelope that follows the incoming AC voltage waveform. As discontinuous conduction mode results in higher primary RMS currents, a TOP247YN was selected to minimize the RDS(ON) of the MOSFET, reduce dissipation and improve overall efficiency.source

The power supply shown in Figure above uses a LinkSwitch-TN device in a low side buck converter configuration to deliver a constant current of 130 mA at a voltage of 70 VDC. The supply provides an ideal solution for driving LEDs that should be driven with a constant current rather than a constant voltage source.Fuse F1 provides catastrophic failure protection. Capacitor C1 and common mode choke L1 reduce conducted EMI. Diodes D1 through D4 provide full wave rectifi cation while high voltage capacitor C2 maintains a steady DC bus voltage.source