RDK-268 Power Integrations

LNK454/456-458/460 LinkSwitch-PL Family LED Driver IC with TRIAC Dimming, Single-Stage PFC and Constant Current Control for Non-Isolated Applications Product Highlights Dramatically Simplifies Off-line LED Drivers Flicker-free phase-controlled TRIAC dimming Single-stage power factor correction and accurate constant current (CC) output Very low component count with small non-electrolytic bulk capacitor for compact replacement lamp designs AC IN LinkSwitch-PL D Compact SO8, eSOP, and eDIP packages CONTROL Completely eliminates control loop compensation BP S FB Advanced Performance Features Optimized for non-isolated flyback designs Frequency jitter greatly reduces EMI filter size and costs Low dissipation direct sensing of LED current PI-5835-060710 Advanced Protection and Safety Features Figure 1. Basic Application Schematic. Cycle skipping regulation for abnormally low output power to clamp peak output current delivered Output Power Table 725 V integrated power MOSFET allows small bulk capacitance 85-265 VAC and maximizes power capability 2 Product Minimum Output Maximum Output Short-circuit, overload, open feedback and output overvoltage 1 Power Power protection LNK454D 1.5 W 3 W Hysteretic thermal shutdown LNK456D 3 W 6 W Meets high-voltage creepage between DRAIN and all other pins LNK457D/K/V 4 W 8 W both on PCB and at package LNK458K/V 6 W 11.5 W EcoSmart - Energy Efficient LNK460K/V 8 W 16 W High power factor optimizes system lumen per input VA Table 1. Output Power Table. Control algorithm balances switching and conduction losses Notes: 1. Maximum practical continuous power in an open frame design with adequate over line and load to maintain optimum efficiency heat sinking, measured at +50 C ambient (see Key Applications Considerations for more information). Description 2. Packages: D: SO-8C, K: eSOP-12, V: eDIP-12. The LinkSwitch-PL family enables a very small and low cost Output Current single-stage power factor corrected constant current driver for solid state lighting. Optimized for direct LED current sensing, the Number of 350 mA 500 mA 700 mA 1000 mA LinkSwitch-PL operates over a wide input voltage range delivering Serial LEDs an output power of up to 16 W. The LinkSwitch-PL control 1 LNK454 LNK454 LNK454 LNK456 algorithm provides flicker-free TRIAC dimming with minimal 2 LNK454 LNK456 LNK456 LNK457 external components. 3 LNK456 LNK456 LNK457 LNK458 4 LNK456 LNK457 LNK458 LNK460 Each device incorporates a 725 V rated power MOSFET, a novel 5 LNK457 LNK458 LNK460 discontinuous mode variable frequency variable on-time controller, 6 LNK457 LNK458 LNK460 frequency jitter, cycle-by-cycle current limit and hysteretic thermal 7 LNK458 LNK460 shutdown in a monolithic 4-pin IC, available in SO-8C, eSOP-12, 8 LNK458 LNK460 and eDIP-12 packages. 9 LNK458 LNK460 10 LNK460 11 LNK460 12 LNK460 Figure 2. Device Selection Based on Length of Output LED Series String and Current. A Typical Voltage Drop of 3.5 V per LED is Assumed. www.powerint.com October 2011LNK454/456-458/460 DRAIN (D) REGULATOR BYPASS (BP) 5.85 V UV 4.9 V I I + LIM LIM V I LIM CURRENT LIMIT SOA SOA Q SET S STATE MACHINE V FB(SK) + Q CLR R UV + V FB(LO) Zero Crossing + PHASE V DAC I REF FB MEASUREMENT V Z LIM 1 A DIGITAL FILTER + AUTO-RESTART FEEDBACK (FB) INTEGRATOR Update INC/DEC CLK SET S Q FREQUENCY/ DUTY CYCLE CONTROLLER R CLR Q ON-TIME EXTENSION SOURCE (S) PI-5893-091010 Figure 2. Functional Block Diagram. Pin Functional Description D Package (SO-8C) DRAIN (D) Pin: High-voltage power MOSFET drain connection. The internal 8 1 FB S Exposed Pad (On Bottom) start-up bias current is drawn from this pin through a switched Internally Connected to 7 2 S high-voltage current source. Drain current sensing and BP SOURCE Pin 6 K Package associated controller functions are also performed using this pin. S (eSOP-12) 4 5 SOURCE (S) Pin: D S NC 1 12 S Power MOSFET source connection. Ground reference for FB 2 11 S BYPASS and FEEDBACK pins. BP 3 10 S BYPASS (BP) Pin: NC 4 9 S Connection point for the external bypass capacitor for the 8 S internally generated 5.85 V supply. D 6 7 S Exposed Pad Internally Connected to SOURCE Pin FEEDBACK (FB) Pin: V Package (eDIP-12) LED current sensing pin. During normal operation the 290 mV threshold determines the average value of the current flowing S 12 1 NC through the load sense resistor. S 11 2 FB S 10 3 BP A second threshold clamps excessive output current ripple. 4 NC S 9 A third higher threshold is used to protect against output S 8 short-circuit and overvoltage conditions (see Figure 5). S 7 6 D PI-5836a-061311 Figure 3. Pin Configuration (Top View). 2 Rev. C 10/11 www.powerint.com