MP4032-1—PRIMARY-SIDE-CONTROLLED, OFFLINE LED DRIVER WITH FULLY-INTEGRATED MOSFET

MP4032-1 Rev. 1.02

www.MonolithicPower.com

13

7/15/2013

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+

1.9 uS

Blanking

Vcc

ZCD

Auxiliary Winding

OVP

signal

5.3V

Latch

Figure 6: Over-Voltage Sampling Unit

To avoid an oscillation spike mis-triggering the

OVP after the switch turns off, the OVP has a

blanking period, as shown in Figure 7. The

0V

Sampling Here

LEB _OVP

Figure 7: ZCD Voltage and OVP Sampling

Over-Current Protection

The MP4032-1 clamps the CS pin voltage

short circuit on the secondary-side occurs, the

ZCD pin can’t detect the zero-crossing signal and

triggers a 130µs auto-restart process. The COMP

voltage drops and the primary-side-peak current

falls, thus limiting the SC current. Meanwhile, the

auxiliary winding voltage falls following the

and the system restarts. Furthermore, once the

COMP level exceeds 5V, the COMP OCP

drops to 7.5V UVLO, and the system auto-

restarts.

Thermal Shutdown

To prevent thermal damage, the MP4032-1 shuts

off switching and remains latched once the inner

temperature exceeds the OTP threshold. When

TRIAC-Phase Dimming

The MP4032-1 can implement TRIAC-based

dimming. As shown in Figure 8, the TRIAC

dimmer is a bi-directional SCR with an adjustable

turn-on phase. The MP4032-1 detects the

dimming phase signal on the MULT pin that

feeds the signal into the control loop for the

dimming control.

Phase Detect

Signal

Input Line

Voltage

Line Voltage

after TRIAC

TRIAC turn

on phase

T

Delay

Figure 8: TRIAC-Phase Detection Signal for a

Leading-Edge TRIAC Dimmer