Texas Instruments LM3445 Evaluation Boards LM3445-EDSNEV/NOPB LM3445-EDSNEV/NOPB データシート
製品コード
LM3445-EDSNEV/NOPB
delay
V
BUCK
V
AC
V
BR1
t
?
(a)
(b)
(c)
t
t
V
AC
V
BR1
t
(a)
(b)
(c)
V
BUCK
SNVS570L – JANUARY 2009 – REVISED MAY 2013
SENSING THE RECTIFIED TRIAC WAVEFORM
A bridge rectifier, BR1, converts the line (mains) voltage (
c) into a series of half-sines as shown in
b.
a shows a typical voltage waveform after diode D3 (valley fill circuit, or V
BUCK
).
Figure 15. Voltage Waveforms After Bridge Rectifier Without Triac Dimming
c and
b show typical triac dimmed voltage waveforms before and after the bridge rectifier.
a shows a typical triac dimmed voltage waveform after diode D3 (valley fill circuit, or V
BUCK
).
Figure 16. Voltage Waveforms After Bridge Rectifier With Triac Dimming
LM3445 LINE SENSING CIRCUITRY
An external series pass regulator (R2, D1, and Q1) translates the rectified line voltage to a level where it can be
sensed by the BLDR pin on the LM3445.
sensed by the BLDR pin on the LM3445.
10
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