AL1666 datasheet(8/16 Pages) DIODES

8 / 16 page

AL1666

Document number: DS42417 Rev. 1 - 2

8 of 16

www.diodes.com

December 2019

AL1666

Application Information

The AL1666 is a constant current high PF Flyback and Buck-boost controller with Primary Side Regulation (PSR), targeting LED lighting

applications. The device eliminates the opto-couplers or the secondary feedback circuits, which will help to minimize the whole system BOM cost.

High power factor is achieved by constant on-time operation. In order to reduce the switching losses and improve EMI performance, quasi-

resonant switching mode is applied. The AL1666 integrates multiple protections including UVLO protection, VCC over voltage protection, output

open voltage protection, over current protection, thermal fold-back protection and over temperature protection. The AL1666 can support analog

dimming mode and PWM dimming.

OUT

VCC

OUT

GND

RTH

Input

VR1

DB1

RCS

R10

COMP

R14

CCOMP

Aux

ADIM

AL1666

PWMD

RCOMP

CVCC

R11

PWM Signal

CDIM

Figure 1. Flyback Application Circuit

OUT

VCC

OUT

GND

RTH

Input

VR1

DB1

RCS

COMP

Aux

AL1666

R11

ADIM

CDIM

PWM Signal

PWMD

CCOMP

RCOMP

CVCC

Figure 2. Buck-Boost Application Circuit

Start-Up

After AC supply is powered on, the capacitor CVCC across VCC pin and GND pin will be charged up by BUS voltage through a start-up resistor RTH.

Once VCC reaches VCC_TH, the internal blocks start to work. VCC is supplied by VBUS until the auxiliary winding of Flyback transformer could supply

enough energy to maintain VCC above VOPR_MIN. If VCC voltage is lower than VOPR_MIN, the switch will be turned off.

After VCC exceeds VCC_TH, the drive blocks don’t start to switch on/off signals until VCOMP is higher than the initial voltage VCOMP_ST which can be

programmed by RCOMP. The formula is shown as below. Such design can program startup on time to reduce the startup time or reduce the output

overshoot current.

COMP









700

Where VCOMP_ST is the pre-charged voltage of COMP pin, RCOMP is shown as Figure 1.

Generally, a big capacitance of CCOMP is necessary to achieve high power factor and stabilize the system loop (1μF to 2μF is recommended). The

pre-charged voltage in start-up procedure can be programmed by RCOMP.

AL1666 Datasheet(PDF) 8 Page - Diodes Incorporated

AL1666 Datasheet(HTML) 8 Page - Diodes Incorporated

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Datasheet Download

Link URL