UM10501
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© NXP B.V. 2011. All rights reserved.
User manual
Rev. 2 — 16 November 2011
11 of 18
NXP Semiconductors
UM10501
SSL21083 reference board user manual
9. Active
bypass
An increased value for the inrush current resistor protects the board from damage with
phase-cut dimmers, but lowers the efficiency. If a higher power factor is not required, but
leading-edge dimmer resistance and high efficiency are important, the active bypass
option is available. In this circuit, the inrush current resistor is bypassed using a Silicon
Controlled Rectifier (SCR) (see
).
shows the results when active bypass is used.
Table 4.
Active bypass
V
IN
(V (AC))
V
o
(V
avr
)
I
o
(mA)
R1 (
)
Efficiency (%) Power factor
THD (%)
230
121
92
100
93.5
0.57
114
230
61
100
100
91.3
0.54
140
Fig 10. Active bypass
aaa-000503
100 Ω
2 MΩ
MCR22-6
470 nF