NCL30083(2013_02) 데이터 시트보기 (PDF) - ON Semiconductor

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NCL30083
(Rev.:2013_02)

Dimmable Quasi-Resonant Primary Side Current-Mode Controller for LED Lighting with Thermal Fold-back

ON Semiconductor 

NCL30083

Step Dimming

The step dimming function decreases the output current

from 100% to 5% of its nominal value in discrete steps.

There are 5 steps in total. Table 4 shows the different steps

value and the corresponding output current set−point. Each

time a brown−out is detected, the output current is decreased

by decreasing the reference voltage VREF setting the output

current value.

When the 5% dimming step is reached, if a brown−out

event occurs, the controller restarts at 100% of the output

current.

Table 4. DIMMING STEPS

Dimming Step

ON

Iout

100%

1

70%

2

40%

3

25%

4

10%

5

5%

Perceived Light

100%

84%

63%

50%

32%

17%

Vbulk

Vbulk(on)

Vbulk(off)

VCC

VCC(on)

Note:

The power supply designer must ensure that VCC stays

high enough when the light is turned−off to let the controller

memorize the dimming step state.

The power supply designer should use a split VCC circuit

for step dimming with a capacitor allowing providing

enough VCC for 1 s (47 mF to 100 mF capacitor).

The step dimming state is memorized by the controller

until VCC crosses VCC(reset).

VCC

4.7 mF

47 − 100 mF

Figure 62. Split VCC Supply

VCC(off)

VCC(reset)

BO

comp

Iout

100%

70%

40%

25%

10%

5%

Figure 63. Step Dimming Chronograms

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