UM10501
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© NXP B.V. 2011. All rights reserved.
User manual
Rev. 2 — 16 November 2011
10 of 18
NXP Semiconductors
UM10501
SSL21083 reference board user manual
8. Power factor adjustment
The SSL21083 IC and SSL21083 reference designs are designed for standard operation
with a power factor of 0.6 at 230 V (AC). This choice offers highest efficiency. It is possible
to tune the power factor to higher values using two methods.
Increasing the value of R1 raises the power factor above 0.7 with additional losses. (see
).
A resistor value of 270
for R1 also results in operation with most available phase cut
dimmers without damaging the lamp or dimmer. This change is not intended to reach
stable operation without flicker or a good dimming range.
Dimension the power rating of R1 to handle peak powers that occur using leading-edge
dimmers. These powers range between 2 W to 4 W. Alternatively, make a thermal link
between the onboard NTC and R1, causing the board to turn off at overtemperature of R1.
The second option is to increase power factor is using a valley fill circuit. The basic
schematic for this circuit is shown in
.
shows the results when using a
4.7
F capacitor for C2X and C2Y.
The valley fill circuit can only be employed, if the output voltage is below half the peak
input voltage. At 230 V (AC) input, it operates up to 85 V (DC) output voltage, otherwise
no power is delivered to the LEDs during the valley duration.
Table 2.
Power factor adjustment - increasing the value of resistor R1
V
IN
(V (AC))
V
o
(V
avr
)
I
o
(mA)
R1 (
)
Efficiency (%) Power factor
THD (%)
230
101.5
94
10
95.2
0.59
109.2
230
102.9
127
10
94.7
0.6
94
230
98
46
22
91.6
0.52
150
230
100.6
94
22
94.4
0.6
107
230
100.8
94
270
85.2
0.71
84
Table 3.
Power factor adjustment - valley fill circuit
V
IN
(V (AC))
V
o
(V
avr
)
I
o
(mA)
R1 (
)
Efficiency (%)
Power factor
THD (%)
230
85
97
22
95.1
0.78
66
230
61
100
270
89.3
0.8
58
Fig 9.
Valley fill circuit
aaa-000502
R1
C2X
C2Y