LYT3314-3328
LYTSwitch-3 Family
Single-Stage LED Driver IC with Combined PFC and
Constant Current Output for Outstanding TRIAC Dimming
in Isolated and Non-Isolated Topologies
Product Highlights
Combined Single-Stage PFC + Accurate CC Output
• Less than ±3% CC regulation over line and load
L
• Power Factor >0.9
• Ensures monotonic VA reduction with TRIAC phase angle
• Low THD, 15% typical for dimmable bulbs, as low as 7% in
T
LYTSwitch-3
BL
L
D
S
N
optimized designs
CONTROL
BS
DS
Advanced Integrated TRIAC Dimmer Detection
• Detects leading-edge and trailing-edge TRIAC dimmers
• High-efficiency mode when no dimmer is present
• Selectable dimming profile increases design flexibility
• Fast turn-on (<500 ms)
FB
BP
OC
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• Low pop-on and dead-travel
• Active bleeder drive for widest dimmer compatibility
Figure 1. Simplified Schematic (Buck).
Design Flexibility
• Supports buck, buck-boost, tapped buck-boost, boost, isolated and
non-isolated flyback
• Up to 20 W output
Output Power Table
Product2
Output Power1
Highest Reliability
• No electrolytic bulk capacitors or optoisolators for increased lifetime
• Comprehensive protection features
• Input and output overvoltage
• Output short-circuit and open-loop protection
• Advanced thermal control
• Thermal foldback ensures that light continues to be delivered at
elevated temperatures
• End-stop shutdown provides protection during fault conditions
85-132 VAC or 185-265 VAC
LYT33x4D3
LYT33x5D
LYT33x6D
LYT33x8D
5.7 W
8.8 W
12.6 W
20.4 W
Table 1. Output Power Table (Buck Topology).
Description
Notes:
1. Maximum practical continuous power in an open frame design with adequate
heat sinking, measured at 50˚C ambient (see Key Applications Considerations
for more information).
The LYTSwitch™-3 family is ideal for single-stage power factor
corrected constant current LED bulbs and downlighters.
2. Package: D: SO-16B.
Each device incorporates a high-voltage power MOSFET and discon-
tinuous mode, variable frequency variable on-time controller. The
controller also provides cycle-by-cycle current limit, output OVP, line
overvoltage, comprehensive protection features, plus advanced
thermal management circuitry.
3. ”x” digit describes VDSON(MAX) of the integrated switching MOSFET,
650 V = 1, 725 V = 2.
All LYTSwitch-3 ICs have a built-in TRIAC detector that discriminates
between leading-edge and trailing-edge dimmers. This capability
together with load monitoring circuitry regulates bleeder current during
each switching cycle. The controller disables the bleeder circuit
completely if no dimmer is detected, significantly increasing efficiency.
Figure 2. SO-16B (D Package).
The combination of a low-side switching topology, cooling via electroni-
cally quiet SOURCE pins and frequency jitter ensure extremely low EMI.
This reduces the size of the input filter components – greatly reducing
audible noise during dimming.
The part numbers shown in Table 1 describe 4 different power levels and
two MOSFET voltage options to cost-optimize designs while EcoSmartTM
switching technology insures maximum efficiency for each device size
and load condition.
www.power.com
April 2016
This Product is Covered by Patents and/or Pending Patent Applications.