delay

t

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(a)

(b)

(c)

t

t

t

(a)

(b)

(c)

LM3445

SNVS570K – JANUARY 2009 – REVISED NOVEMBER 2011

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SENSING THE RECTIFIED TRIAC WAVEFORM

A bridge rectifier, BR1, converts the line (mains) voltage (Figure 15c) into a series of half-sines as shown in

Figure 15. Voltage Waveforms After Bridge Rectifier Without Triac Dimming

Figure 16c and Figure 16b show typical triac dimmed voltage waveforms before and after the bridge rectifier.

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.

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