MP4060—TRIAC Dimmable PFC, PSC LED Controller for 200-265VAC LEDs

MP4060 Rev. 1.0

www.MonolithicPower.com

19

5/27/2015

MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.

© 2015 MPS. All Rights Reserved.

Thermal Protection

To prevent the IC and the system from any lethal

thermal damage (when the junction temperature

exceeds

reference to decrease the output current, which

limits the rising temperature speed of the IC.

Typically, the output current drops to 20 percent

switching cycle and is latched until VCC drops

below UVLO. When the junction temperature

starts again.

Bleeder Disable

If the external active bleeder is applied to

improve the TRIAC-dimming compatibility, the

MP4060 features a bleeder disable function to

pull down the bleeder transistor by BD. This

improves

system

efficiency

and

thermal

performance if the bleeder is useless in certain

conditions. Figure 10 shows the bleeder disable

circuit.

Figure 10—Bleeder disable circuit

The integrated BD FET works in an open-drain

configuration when VCC drops below UVLO or

the active bleeder is activated.

The BD FET is turned on to pull down the

bleeder transistor under the following conditions:

I.

The dimmer is not connected to the driver.

II. The fault (OVP/OCP/OTP) triggers.

III. The system works in auto-restart mode over

The BD timing sequence is shown in Figure 11.

Figure 11—BD timing sequence

Adaptive Dimmer Type Detection

The MP4060 integrates adaptive dimmer type

detection to detect accurately which kind of

dimmer is connected at the system start-up

(leading-edge dimmer, trailing-edge dimmer, or

no dimmer). The MP4060 works in different

modes depending on the dimmer types to

achieve the best dimmer compatibility with the

highest performance.

Phase-Cut-Based Dimming Control

The

MP4060

implements

phase-cut-based

dimming control (both for leading-edge and

trailing-edge

dimmers).

For

leading-edge

dimmers, most are TRIAC-based. Usually, the

TRIAC dimmer consists of a bi-directional SCR

and an adjustable turn-on phase. Figure 12

shows

the

leading-edge

TRIAC

dimmer

waveforms.

Line voltage

after TRIAC

dimm er

Input line

voltage before

TRIAC dim m er

Rectified line

voltage

Dimmer

turn on

phase

Line cycle

Figure 12—Leading-edge dimmer waveforms