RDK-268 Power Integrations, RDK-268 Datasheet - Page 4

• Manufacturer Part Number: RDK-268
• Description: REFERENCE DESIGN LINKSWITCH-PL
• Manufacturer: Power Integrations
• Series: LinkSwitch®-PLr

Specifications of RDK-268

• Mfg Application Notes: LinkSwitch-PL Family AppNote
• Design Resources: RDR-268
• Current - Output / Channel: 366mA
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 2.5 V ~ 3.5 V
• Voltage - Input: 85 ~ 265VAC
• Utilized Ic / Part: LNK454DG
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 596-1423

Rev. A 11/01/10
Figure 6.
TRIAC (Phase-Controlled) Dimming
The LinkSwitch-PL integrates several features to improve
dimming range and reduce external circuit complexity when
using a phase-controlled TRIAC dimmer. The output LED
current is controlled by the FEEDBACK pin voltage which
changes proportionally to the TRIAC dimmer conduction angle.
When the conduction angle decreases, the voltage at the
FEEDBACK pin decreases causing the average LED current to
decrease.
The FEEDBACK pin reference voltage adjustment is initiated at
approxi-mately 25% of the AC line half-cycle duration. When this
4
LNK454/456-458/460
Feedback Voltage vs. Phase Angle Dimming Characteristics.
V
V
V
TRIAC
LINE
FB( ϕ )
V
0°
0°
FB
ϕ OS
Phase
Angle
ϕ
TRIAC Dimmers
Leading Edge
Conduction
Angle
ϕ OL
180°
Phase
Angle
Phase
Angle
( j OS) threshold is exceeded, V
are reduced until a second phase angle threshold is reached.
At this point, with the TRIAC conduction angle being very
limited, the IC runs open loop at constant frequency and duty
cycle ( j OL region) and the integrated power MOSFET
processes as much power as the heavily chopped input voltage
will allow creating a light output that is deeply dimmed.
The 520 mV clamping feedback threshold is also linearly reduced
during dimming to control LED current ripple.
V
FB( ϕ )
0°
0°
ϕ OL
Conduction
Angle
Trailing Edge
Dimmers
FB
Phase
Angle
ϕ
and the output LED current
ϕ OS
180°
PI-5894a-091010
www.powerint.com
Phase
Angle
Phase
Angle