LNK456DG View Datasheet(PDF) - Power Integrations, Inc

Part Name

Description

Manufacturer

LNK456DG

LED Driver IC with TRIAC Dimming, Single-Stage PFC and Constant Current Control for Non-Isolated Applications

Power Integrations, Inc 

LNK454/456-458/460

VFB

ϕOS

VFB(ϕ)

ϕOL

ϕOL

VFB(ϕ)

0°

VLINE

VTRIAC

180°

Phase

Angle

0°

ϕOS

180°

Phase

Angle

ϕ

0° Phase

Angle

Conduction

Angle

Leading Edge

TRIAC Dimmers

Phase

Angle

0°

Conduction

Angle

ϕ

Phase

Angle

Phase

Angle

Trailing Edge

Dimmers

PI-5894a-091010

Figure 6. Feedback Voltage vs. Phase Angle Dimming Characteristics.

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

(jOS) threshold is exceeded, VFB and the output LED current

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 (jOL 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.

4

Rev. A 11/01/10

www.powerint.com

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