LNK458DG View Datasheet(PDF) - Power Integrations, Inc

Part Name

Description

MFG CO.

LNK458DG

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

Power Integrations, Inc 

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LNK454/456-458/460

DES

DZOV

AC

RES

ROV

IN

D LinkSwitch-PL

CONTROL

BP

S

FB

CF

RF

RSENSE

PI-5837-060710

Figure 4. Typical Application Schematic.

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 (RSENSE in Figure 4). A small low-pass filter

(RF and CF in Figure 4) reduces high frequency noise at the

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 set 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 power 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.

Auto-restart protection is triggered by a FEEDBACK pin voltage

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

overvoltage protection (via DZOV and ROV, in Figure 4), which

triggers the IC to enter auto-restart.

Auto-Restart

2V

Cycle Skipping

Mode

Normal Operation

290 mV

520 mV

PI-5838-091010

Figure 5. FEEDBACK Pin Operational Voltage Thresholds.

www.powerint.com

3

Rev. A 11/01/10

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