MP4033GSE datasheet(20/25 Pages) MPS

20 / 25 page

MP4033—PRIMARY-SIDE–CONTROL, OFFLINE LED CONTROLLER WITH PFC

MP4033 Rev. 1.0

www.MonolithicPower.com

10/22/2014

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

Figure 13: Leading Edge Dimming Curve

For trailing edge dimmer, there is no holding

current, the COMP voltage is clamped at a lower

level VCOML_TL to get deeper dimming depth.

Figure 14 shows the relationship between the

trailing edge dimming turn-on phase and output

current.

Dimming turn on cycle

100%

40%

70%

VCOMP

Figure 14: Trailing Edge Dimming Curve

Dimming Pull-Down Current Source

There are three kinds of dimming pull down

current source in MP4033. The IDP_TL current

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

the MULT decreases to VMULT_DP_ON_LD and turns

off until the MULT increases to VMULT_DP_OFF_LD. If

trailing edge dimmer is detected, the dimming

pull-down current source turns on when the

MULT decreases to VMULT_DP_ON_TL and turns off

until the MULT increases to VMULT_DP_OFF_TL.

The weak/strong dimming pull down current

source is selected through different resistance on

the ZCD pin. Figure 15 shows the selected logic:

If IDP_DET_LD *(R1+R2//R3)≥VEN_DP_STR_LD

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.

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

VMULT_DAMP_ON and begins to be pulled down when

MULT

voltage

decreases

lower

than

VMULT_DAMP_OFF. The maximum pull up current

source is 100μA while the max pulling down

current source is 400μA.

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