This article introduces Powerint’s high power factor (PF) TRIAC dimming LED driver. The driver is designed to drive a nominal LED string voltage of 30V (at a current of 0.5A) with an input voltage range of 180VAC~265VAC. This LED driver adopts LNK405EG of LinkSwitch-PH series IC.
LinkSwitch-PH ICs enable low-cost, low-component-count LED drivers that meet power factor and harmonic constraints while enhancing the end-user experience. It has an extremely wide dimming range, flicker-free operation (even with the cost characteristics of an AC line TRIAC dimmer), fast and clean turn-on characteristics.
It uses an isolated flyback topology and operates in continuous conduction mode. The output current is regulated entirely by primary side induction, eliminating the need for secondary side feedback components. Since this is performed inside the IC, there is no need for external current sensing on the primary side, further reducing component count and losses. An internal controller adjusts the MOSFET duty cycle to maintain sinusoidal input current, which in turn maintains high power factor and low harmonic currents.
Figure 1 Outline diagram of 15W dimming LED driver
The LinkSwitch-PH IC also offers a variety of advanced protection features, including automatic restart in the event of an open control loop and an output short. Line overvoltage extends line fault and surge tolerance, output overvoltage protects the power supply in the event of load disconnection, and precise delayed thermal shutdown ensures a safe average PCB temperature under various conditions. Regardless of the LED light source, the driver is able to determine the performance attributes experienced by the end user. The design emphasizes compatibility with various dimmers, enabling the widest possible dimming range at 230VAC.
Figure 2 15W dimming LED driver motherboard circuit diagram
• Designed for compatibility with standard TRIAC dimmers
• Compatible with models rated at 1000W (vs. 600W)
• No output flickering
• No crackling when starting from low phase angles
• Up to 1000:1 dimming range – limited only by connected dimmer
• Monotonic start – no output flicker
Figure 3 Layout of motherboard components (top layer)
Figure 4 Layout of main board components (bottom layer)
• High energy efficiency
• Under the voltage of 230VAC, the efficiency is over 84% Comprehensive protection and reliability characteristics
• Output open circuit/output short circuit protection and automatic recovery
• Line input overvoltage shutdown extends withstand voltage range in the event of a line fault
• Auto-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
The Links: NL6448BC20-21C MDR250A40