LNK405EG:15WPAR38TRIAC dimming LED driver solution

This article describes a high power factor (PF) TRIAC dimming LED driver from Powerint. The driver is designed to drive a nominal LED string voltage of 30V (at 0.5A) with an input voltage range of 180VAC to 265VAC. The LED driver uses the LNK405EG from the LinkSwitch-PH family of ICs. The

LinkSwitch-PH IC enables a low-cost, low-component-count LED driver that meets power factor and harmonic constraints while enhancing the end-user experience. It features an extremely wide dimming range, flicker-free operation (even at the cost of AC line TRIAC dimmers), and fast and clean turn-on characteristics.

It uses an isolated flyback topology and operates in continuous conduction mode. Output current regulation is entirely through primary-side sensing, eliminating the need for secondary-side feedback components. Because this is performed internally in the IC, no external current sensing is required on the primary side, further reducing component count and losses. The internal controller can adjust the MOSFET duty cycle to maintain a sinusoidal input current, thereby maintaining high power factor and low harmonic currents.


Figure 1 15W dimming LED driver outline

LinkSwitch-PH IC also provides a variety of advanced protection features, including automatic restart in the event of an open control loop and an output short circuit. Line overvoltage extends line fault and surge tolerance, output overvoltage protects the power supply when the load is disconnected, and precise delayed thermal shutdown ensures a safe average PCB temperature under various conditions. Regardless of the LED light source, the driver determines the performance attributes experienced by the end user. The design emphasizes compatibility with a variety of dimmers and can achieve the widest possible dimming range at a voltage of 230VAC.

Figure 2 15W dimming LED driver motherboard circuit diagram

Key features

• Designed with compatibility in mind with standard TRIAC dimmers

• Compatible with models rated at 1000W (vs. 600W)

• No output flicker

• No crackling when starting from low phase angles

• Up to 1000:1 dimming range - limited only by the connected dimmer

• Monotonic startup - no output flicker

Figure 3 Motherboard component layout (top)

Figure 4 Motherboard component layout (bottom)

• High energy efficiency

• Over 84% efficiency at 230VAC Comprehensive protection and reliability features

• Output open/output short protection and automatic recovery

• Line input overvoltage shutdown extends the withstand voltage range in the event of a line fault

• Automatic recovery thermal shutdown with long delay feature protects components and printed circuit boards

• Meets IEC61000-4-5 ring wave, IEC61000-3-2 Class C and EN55015 B conducted EMI requirements