Single-Stage Accurate Primary-Side Constant Current (CC) Controller
Typical Schematic

Product Highlights

  • Better than ±5% Constant Current (CC) Regulation
  • Power Factor Correction (PFC) for Low-Line Applications
  • TRIAC Dimming and Non-Dimming Options


High Performance, Combined Driver, Controller, Switch

The LYTSwitch-4 family enables off-line LED drivers with high power factor which easily meet international requirements for THD and harmonics. Output current is tightly regulated with better than ±5% CC tolerance1. Efficiency of up to 92% is easily achieved in typical applications.

Supports a Wide Selection of TRIAC Dimmers

The LYTSwitch-4 family provides excellent turn-on characteristics for leading-edge and trailing-edge TRIAC dimming applications. This results in drivers with a wide dimming range and fast start-up, even when turning-on from a low conduction angle. Large dimming ratio and low "pop-on" current.

Low Solution Cost and Long Lifetime

LYTSwitch-4 ICs are highly integrated and employ a primary-side control technique that eliminates the optoisolator and reduces component count. This allows the use of low-cost single-sided printed circuit boards. Combining PFC and CC functions into a single-stage also helps reduce cost and increase efficiency. The 132 kHz switching frequency permits the use of small, low-cost magnetics.

LED drivers using the LYTSwitch-4 family do not use primary-side aluminum electrolytic bulk capacitors. This means greatly extended driver lifetime, especially in bulb and other high temperature applications.

Other Features

  • Fast start-up
    • <250 ms at full brightness
    • <1s at 10% brightness
  • High power factor >0.9
  • Easily meets EN61000-3-2
    • Less than 10% THD in optimized designs
  • Up to 92% efficient
  • 132 kHz switching frequency for small magnetics

Optimized for Different Applications and Power Levels

Part Number Input Voltage Range TRIAC Dimmable
LYT4211-LYT4218 85-132 VAC No
LYT4311-LYT4318 85-132 VAC Yes
LYT4221-LYT4228 160-300 VAC No
LYT4321-LYT4328 160-300 VAC Yes

Low-Line Output Power Table2
Product6 Minimum
Output Power3
Output Power4
LYT4x11E/L5 2.5 W 12 W
LYT4x12E/L 2.5 W 15 W
LYT4x13E/L 3.8 W 18 W
LYT4x14E/L 4.5 W 22 W
LYT4x15E/L 5.5 W 25 W
LYT4x16E/L 6.8 W 35 W
LYT4x17E/L 8.0 W 50 W
LYT4x18E/L 18 W 78 W
Table 1. Low-Line Output Power Table.

High-Line Output Power Table2
Product8 Minimum
Output Power3
Output Power4
LYT4x21E7 6 W 12 W
LYT4x22E 6 W 15 W
LYT4x23E 8 W 18 W
LYT4x24E 9 W 22 W
LYT4x25E 11 W 25 W
LYT4x26E 14 W 35 W
LYT4x27E 19 W 50 W
LYT4x28E 33 W 78 W
Table 2. High-Line Output Power Table.


  1. Performance for typical design. See Applications Note.
  2. Continuous power in an open-frame design with adequate heat sinking; device local ambient of 70 °C. Power level calculated assuming a typical LED string voltage and efficiency >80%.
  3. Minimum output power requires CBP = 47 μF.
  4. Maximum output power requires CBP = 4.7 μF.
  5. LNK4311 CBP = 47 μF, LNK4211 CBP = 4.7 μF.
  6. Package: eSIP-7C(E), eSIP-7F(L).
  7. LYT4321 CBP = 47 µF, LYT4221 CBP = 4.7 µF.
  8. Package: eSIP-7C

Product Documents
Package Informationpackageinfo.pdf
Data Sheetlytswitch-4_family_datasheet.pdf

Reference Design Kits (RDKs)
RDKs include a working power supply, sample devices, unpopulated pcb, data sheet, comprehensive engineering report, PI Expert design software and other related documentation.
RDK-347 12.6 W, Isolated Flyback, Dimmable, Power Factor Corrected LED Driver
Design Examples
DER-395 14.35 W High Efficiency (>86%) High Power Factor (>0.95) TRIAC Dimmable Non-Isolated LED Driver for PAR30 Lamps
DER-370 8.8 W High Efficiency (>86%) High Power Factor (>0.91) TRIAC Dimmable Non-Isolated LED Driver for PAR16 Lamps
DER-404 8 W High Efficiency (>84%) High Power Factor (>0.90) TRIAC Dimmable Non-Isolated LED Driver for A19 Lamps
DER-405 25 W High Efficiency (>90%) High Power Factor (>0.97) Non-Isolated LED Driver for T10 Tubes
DER-396 20 W High Efficiency >86% TRIAC Dimmable Isolated LED Driver for PAR38 Lamps
DER-359 8 W, Non-Isolated Buck, TRIAC Dimmable LED Driver for BR30 Lamps