MP4056—TRIAC DIMMABLE, NON-ISOLATED OFFLINE LED CONTROLLER WITH APFC

MP4056 Rev.1.01

www.MonolithicPower.com

20

11/9/2016

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Io

Dimming turn on cycle

100%

30%

70%

Figure 13: Leading Edge Dimming Curve

For trailing edge dimmers, there is no holding

current, the COMP voltage is clamped at a lower

Figure 14 shows the relationship between the

trailing edge dimming turn-on phase and output

current.

Io

Dimming turn on cycle

100%

40%

70%

Figure 14: Trailing Edge Dimming Curve

Dimming Pull-Down Current Source

There are three kinds of dimming pull down

source is for trailing edge dimming, the other two

(weak/strong) current sources are for leading

edge dimming. The dimming pull down current is

used to pull down the rectified line voltage to zero

quickly to avoid any mis-detection on the MULT

pin.

If the leading edge dimmer is detected, the

dimming pull-down current source turns on when

trailing edge dimmer is detected, the dimming

pull-down current source turns on when the

The weak/strong dimming pull down current

source is selected through different resistance on

the ZCD pin. Figure 15 shows the selected logic:

Strong dimming pull-down current source is

selected; otherwise, weak dimming pull down

current source is selected.

In real

application design, the

weak/strong

dimming pull down current selection is related to

the detailed application SPEC.

+

ZCD

-

S

R1

R2

R3

Strong _DP

Figure 15: Weak/Strong Dimming Pull Down

Current Source Selection

Damping Circuit Control

If a leading edge dimmer or trailing edge dimmer

is detected, the damping circuit is enabled to limit

the inrush current at the moment dimmer turns

on. If no dimmer is detected, the damping circuit

is disabled by pulling up the damp pin voltage so

the damping resister is shorted by the damping

MOSFET. The damp pin voltage begins to be

pulled up if MULT voltage increases higher than

MULT

voltage

decreases

lower

than

source is 100

μA while the max pull down current

source is 400

μA.

Color Temperature and Brightness Control

for Warm Sunset Dimming application

The color temperature and brightness control

circuit is shown in figure 16.