Rev. A 06/10

3

LNK454/456-458/460

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This document contains information on a new product. Specifications and information herein

are subject to change without notice.

PRELIMINARY

Functional Description

The LinkSwitch-PL combines a high-voltage power MOSFET

switch with a power supply controller in one device. The IC

provides a single stage power factor correction plus LED

current control. The LinkSwitch-PL controller consists of an

oscillator, feedback (sense and logic) circuit, 5.85 V regulator,

hysteretic over-temperature protection, frequency jittering,

cycle-by-cycle current limit, loop compensation circuitry, auto-

restart, switching on-time extension, power factor and constant

current control.

In a direct LED current sensing configuration, the average

FEEDBACK pin voltage is a replica of the LED current, scaled

by the sense resistor (R

(R

FEEDBACK pin.

Figure 5 illustrates the operating regions of the FEEDBACK pin

voltage. The LinkSwitch-PL sets its operating point such that

the average FEEDBACK pin voltage in steady-state operation is

290 mV. This threshold is low to minimize the sensing resistor

dissipation. The internal MOSFET switching frequency and

on-time are updated once every input AC half-cycle to regulate

the output current and maintain high power factor.

If the FEEDBACK pin peak voltage exceeds 520 mV, cycle

skipping mode is triggered and the power processed by the

integrated MOSFET is clamped on a cycle-by-cycle basis.

Switching frequency may vary during an input voltage half-cycle

to reduce thermal stress on the output LEDs.

Figure 4.

Typical Application Schematic.

Figure 5.

FEEDBACK Pin Operation Voltage Thresholds.

Latching shutdown protection is triggered by a FEEDBACK pin

voltage in excess of 2 V. This feature can be used to provide

output overvoltage protection (via DZ

which triggers the IC to latch off. This condition is reset when

the BYPASS pin voltage drops below 4.9 V, after removal of the

AC input.

PI-5838-041910

Latch Off

2 V

520 mV

Cycle Skipping

Mode

Normal Operation

290 mV

D

S

BP

CONTROL

FB

PI-5837-060710

LinkSwitch-PL

AC

IN