RDK-268 Power Integrations, RDK-268 Datasheet - Page 6

• Manufacturer Part Number: RDK-268
• Description: REFERENCE DESIGN LINKSWITCH-PL
• Manufacturer: Power Integrations
• Series: LinkSwitch®-PLr

Specifications of RDK-268

• Mfg Application Notes: LinkSwitch-PL Family AppNote
• Design Resources: RDR-268
• Current - Output / Channel: 366mA
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 2.5 V ~ 3.5 V
• Voltage - Input: 85 ~ 265VAC
• Utilized Ic / Part: LNK454DG
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 596-1423

Rev. A 11/01/10
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.
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.
Figure 7.
90 - 265
VAC
N
L
6
LNK454/456-458/460
3.15 A
F1
275 VAC
RV1
Schematic of a 5 W, 15 V LED Driver for A19 Incandescent Lamp Replacement.
Passive Damper
47 Ω
R20
2.2 mH
4.7 kΩ
R2
L1
MB6S
600 V
BR1
22 nF
50 V
C3
Active Damper
750 kΩ
750 kΩ
R3
R4
240 Ω
R7
Q3
240 Ω
R8
22 nF
630 V
C4
2.2 mH
4.7 kΩ
R9
L2
68 nF
400 V
C5
Bleeder
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.
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.
510 Ω
510 Ω
68 nF
400 V
R10
R11
100 kΩ
C6
R12
D
S
4.7 Ω
DL4006
LinkSwitch-PL
R13
US1J
CONTROL
D2
LNK457DG
D6
U1
1000 pF
630 V
C7
FB
10 nF
50 V
C8
BP
1 µF
25 V
3.3 kΩ
C9
R15
1
2
EE16
T1
BAV19WS
7
3
6
10 kΩ
R16
D4
27 Ω
R17
SS110-TP
1 kΩ
R21
MAZS2000ML
D5
VR2
20 V
100 V
1 kΩ
R14
1 nF
C10
www.powerint.com
680 µF
0.82 Ω
25 V
C11
R18
1%
PI-6171a-102910
15 V, 350 mA
RTN