LNK454VG View Datasheet(PDF) - Power Integrations, Inc

Part Name

Description

MFG CO.

LNK454VG

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

Power Integrations, Inc 

1 2 3 4 5 6 7 8 9 10 Next

LNK454/456-458/460

LinkSwitch-PL Application Example

The circuit shown in Figure 7 provides a single constant current

output of 350 mA with an LED string voltage of 15 V. The

output current can be reduced using a standard AC mains

TRIAC dimmer down to 1% (3 mA) without instability and

flickering of the LED load. The board is compatible with both

low cost leading edge and more sophisticated trailing edge

dimmers.

The board was optimized to operate over the universal AC input

voltage range (85 VAC to 265 VAC, 47 Hz to 63 Hz) but suffers

no damage over an input range of 0 VAC to 300 VAC. This

increases field reliability and lifetime during line sags and swells.

LinkSwitch-PL based designs provide high power factor (>0.9

at 115 VAC / 230 VAC) and low THD (<15% at 230 VAC, <10%

at 115 VAC) enabling compliance to all current international

requirements and enabling a single design to be used

worldwide.

The form factor of the board was chosen to meet the requirements

for standard pear shaped (A19) LED replacement lamps. The

output is non-isolated and requires the mechanical design of

the enclosure to isolate both the supply and the LED load from

the user.

Due to the much lower power consumed by LED lighting

compared to incandescent lighting, the current drawn by the

lamp is below the holding current of the TRIAC dimmer. This

causes undesirable behavior such as limited dimming range

and/or flickering. Inrush current that flows to charge the input

capacitance when the TRIAC turns on causes current ringing.

This too can cause similar undesirable behavior as the ringing

may cause the TRIAC current to fall to zero and turn off for the

remainder of the AC cycle or rapidly turn on and off.

To overcome these issues the design includes three circuit

blocks, a passive damper, an active damper and a bleeder. The

drawback of these blocks is increased power dissipation and

therefore reduced efficiency of the supply. In this design, the

values selected allow flicker-free operation with a single lamp

connected to a single dimmer at high line. For flicker-free

operation with multiple lamps in parallel or at low line voltages

only (100/115 VAC) then the values may be optimized to reduce

dissipation and increase efficiency.

As these blocks are only required for dimming applications, for

non-dimming designs these components can simply be omitted

with jumpers used to replace R7, R8 and R20.

PI Part Selection

One device size larger than required was selected to increase

efficiency and reduce device thermal rise. This typically gives

the highest efficiency. Further increasing the device size often

results in the same or lower efficiency due to the larger

switching losses associated with a larger power MOSFET.

AC Line TRIAC Dimmer Interface Circuits

The requirement to provide output dimming with low cost,

TRIAC based, leading edge phase dimmers introduces a

number of trade-offs in the design.

Active Damper

R9

4.7 kΩ

L2

2.2 mH

F1

L 3.15 A

90 - 265

RV1

VAC 275 VAC

R2

4.7 kΩ

N

R20

47 Ω

L1

2.2 mH

Passive Damper

BR1

MB6S

600 V

R3

750 kΩ

R4

750 kΩ

C4

22 nF

630 V

C3

22 nF

50 V

Q3

R7

R8

240 Ω 240 Ω

C5

68 nF

400 V

Active and Passive Damper Circuits

Resistor R20 forms a passive damper that together with the

active damper limits the peak inrush current when the TRIAC

fires on each half cycle. It should be a flameproof type to safely

fail during a single point fault (e.g. failure of a bridge diode).

The active damper circuit connects a series resistance (R7 and

R8) with the input rectifier for a period of each AC half-cycle, it is

then bypassed for the remainder of the AC cycle by a parallel

SCR (Q3). Resistor R3, R4 and C3 determines the delay before

the turn-on of Q3 which then shorts out the damper resistors

R7 and R8.

R17

27 Ω

C10

1 nF

100 V

Bleeder

1

7

15 V, 350 mA

R12

100 kΩ

C7

1000 pF

630 V

R10

510 Ω

R13

4.7 Ω

D2

US1J

2

3

6

T1

EE16

D5

SS110-TP

C11

680 µF

25 V

R18

0.82 Ω

1%

RTN

C6

68 nF

400 V

D6

DL4006

LinkSwitch-PL

U1

LNK457DG

D

CONTROL

BP

R11

510 Ω

S

FB

C8

10 nF

50 V

R15

D4

3.3 kΩ BAV19WS

VR2

MAZS2000ML

20 V

R21

1 kΩ

R14

1 kΩ

C9

1 µF

25 V

R16

10 kΩ

PI-6171a-102910

Figure 7. Schematic of a 5 W, 15 V LED Driver for A19 Incandescent Lamp Replacement.

6

Rev. A 11/01/10

www.powerint.com

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